SWMU103_Plan_20080101

FINAL
Corrective Measures Implementation Plan
for
SWMU 103
Fort Bragg, North. Carolina
m
Submitted To:
U.S. ARMY ENVIRONMENTAL COMMAND
Submitted By:
PARSONS
RECE ED
JUN 112008
January 2008
OENR . F.�s,-I-T �' :. _ ,Gr_'nf�lAt OF`10E

_SONS
PA
1700 Broadway, Suite 900 o Dan,�n. C-;forado 80290 z [phone] 3 Fa4:1302,; 831.9208 sr.; roar<ac s.cor
24 January 2008
Ms. Bridget Lyons
US Army Environmental Command, IMAE-CDS/Bridgett Lyons
5179 Hoadley Road, Bldg E-4480
APGEA, MD 21010-5401
Subject: Submittal of the Final Corrective Measures Implementation Plan — SWMU 103,
North Carolina (USAEC Contract W91ZLK-05OD-0016, Task Order 0001)
Ms. Lyons,
Please find enclosed one hard copy and two electronic copies of the Final Corrective
Measures Implementation Plan — SWMU 103, Fort Bragg, North Carolina. This final
document was prepared by Parsons Infrastructure & Technology Group, Inc. (Parsons) for the
United States Army Environmental Command (USAEC) and the Fort Bragg Department of
Public Works (DPW). Copies of this document were also submitted to the Fort Bragg DPW
for their use as well as subsequent distribution to the North Carolina Department of
Environment and Natural Resources (NCDENR). Please. note that the underground injection
permit application contained in Appendix B is currently in review by. NCDENR. Parsons will
submit a final copy of the permit to you after it has been issued by NCDENR.
If you have any questions or require additional information, please contact me (801) 572
5999 or at [e-mail].
cc:
Sincerely,
PARSONS
Ross Miller PhD, P.E.
Project Manager
Mr. Jason Adcock — Fort Bragg (5 copies)
Ms. Angie Cook — Parsons Atlanta (1 copy) .
Mr. Edward Heyse —Parsons Denver (1 copy)
File (2 copies)
EGERIE-0
JUN 112008
DENR - FAYErrEMLLE REG] OVAL OFRCE
103 CMIP FINAL cover letter.doc

i
FINAL
Corrective Measures Implementation Plan
for
SWMU 103
Fort Bragg, North Carolina
Submitted To:
U.S. ARMY ENVIRONMENTAL COMMAND
Submitted By. -
PARSONS
January 2008

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FINAL
CORRECTIVE MEASURES IMPLEMENTATION PLAN
FOR
SWMU 103
FORT BRAGG, NORTH CAROLINA
January 2008
Prepared for:
UNITED STATES ARMY ENVIRONMENTAL
COMMAND
and
FORT BRAGG
l DIRECTORATE OF PUBLIC WORKS
Y
Ross filler PhDP:E.
Project Manager
Ca;iel' riffiths, C.P.G.
Technical Director.
• ,i'l8V1?31:�i�i�:
Edward Heyse PhD, P.E.
Technical Director
9
!ti
2132 p A
7 :`�
.�f
Sava
Steve Saville, PG.�
North Carolina Professional.
t`r Geologist No. 2132

TABLE OF CONTENTS
Page
LIST OF ACRONYMS AND ABBREVIATIONS ......................
SECTIONI - INTRODUCTION ............................................... ..................................... 1-1
1.0
Introduction..........................................................................................................1-1
1.1
Corrective action Objectives .......... .................................................. ....................
1-1
1.2
Document Organization.......................................................................................1-2
1.3
Facility Background..:.................:........................................................................1-2
1.4
Site History...............................................................:.......................................:..
1-3
1.5
Geology and Hydrogeology.................................................................................1-3
1.5.1 Site Geology.............................................:...............................................1-3
1.5.2 Groundwater Hydrology..........................................................................1-4
1.5.3 Surface Water Hydrology .................... :.... ...............................................
1-6
1.6
Summary of Previous Site Investigations............................................................
1-6
1.6.1 RCRA Facility Investigation at SWMUs 4 and 18..................................1-6
1.6.2 RCRA Facility Investigations at SWMU 103..........................................
1-7
1.6.3 Supplemental Investigations for the Corrective Measures Study ............
1-7
1.6.4 Surface Water Sampling by USACE in March 2006...............................1-7
1.6.5 Soil Gas Sampling in June 2006..................::..........................................1-7
1.6.6 Groundwater Sampling in June 2006.......................................................1-8
1.6.8 Corrective Measures Study...................:..................................................1-8
SECTION 2 - PROJECT ORGANIZATION, ROLES, AND
RESPONSIBILITIES............................................................................. 2-1
2.1 Project Organization ............................................... :"*-........
.................................. 2-1
2.2 Responsibilities and Authorities..................................................:....:.................. 2-1
2.2.1 Project Manager....................................................................................... 2-1
2.2.2 Technical Director.............................................................................:..... 2-2
2.2.3 Site Manager............................................................................................ 2-2
2.2.4 . Site Health and Safety Officer.................................................................2-2
2.3 Site Safety............................................................................................................2-2
SECTION 3 - CORRECTIVE MEASURES IMPLEMENTATION .............................. 3-1
3.1 Corrective Measures Design Approach.............:................................................. 3-1
3.1.1 Groundwater............................................................................................ 3-1
3.1.2 Surface Water........................................................................................... 3-2
3.2 Permitting and Regulatory Compliance............................................................... 3-3
3.2.1 Hazardous and Solid Waste Amendment Permit ..................................... 3-3
3.2.2 Underground Injection Permit................................................................. 3-3
3.2.3 Clean Water Act Permit........................................................................... 3-4
3.2.4 Notifications.............................................................................................3-4
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TABLE OF CONTENTS (Continued)
Page
3.2.5
Storm Water Pollution Prevention........................................................... 3-4
3.2.6
Spill Prevention, Control, and Countermeasures.....................................3-4
3.3 Corrective Measures Construction Activities......................................................
3-4
3.3.1
Monitoring Well Network........................................................................
3-4
3.3.1.1 Mobilization............................................................................
3-4
3.3.1.2 Monitoring Well Installation...................................................
3-5
3.3.1.3 Site Restoration.......................................................................
3-5
3.3.1.4 Final Site Survey.....................................................................3-5
3.3.2
Enhanced Bioremediation in Source Area ...............................................
3-6
3.3.2.1 Mobilization.............................................................................3-6
3.3.2.2 Organic Substrate Injection...........................................:.........
3-6
3.3.2.2.1 Substrate Injection Wells ........................................................
3-7
3.3.2.2.2 Substrate Direct Injection Points ................... 3-8
3.3.2.2.3 Substrates..................................I..................... 3-8
3.3.2.2.4 Substrate Preparation and
Emplacement................................................ 3-10
3.3.2.3 Site Restoration...................................................................... 3-12
3.3.2.4 Final Site Survey, ...................................................................
3-12
3.3.3
Surface Water Remedy..........................................................................
3-12
3.3.3.1 Mobilization..........................................................................3-12
3.3.3.2 Aeration/Volatilization Systems Installation ..........:.............
3-13
3.3.3.2.1 Step 1 - Roughen Streambed ........................
3-13
3.3.3.2.2 Step 2 - Drop Structures ...............................
3-14
3.3.3.2.3 Step 3 - Pilot Testing Active Aeration.........
3-15
3.3.3.2.4 Step 4 - Full Scale Active Aeration .............
3-17
3.3.3.3 Site Restoration.....................................................................
3-17
3.3.3.4 Final Site Survey ....................... ............................................
3-17
3.3.4
Fencing and Signs..................................................................................3-17
3.3.4.1 Mobilization..........................................................................
3-17
3.3.4.2 Fencing..................................................................................3-18
3.3.4.3 Warning Signs.......................................................................3-18
3.3.4.4 Site Restoration.....................................................................3-19
3.3.4.5 Final Site Survey...................................................................3-19
3.4 Performance Monitoring....................................................................................
3-19
3.4.1
Groundwater Monitoring Well Network, Frequency, and
Parameters...............................:..............................................................
3 -19
3.4.2
Soil Gas Monitoring...............................................................................
3-20
3.4.3
Surface Water Monitoring Locations, Frequency and Parameters ........
3-20
3.4.4
Performance Evaluations.......................................................................
3-21
3.4.5
Performance Monitoring Program Optimization ...................................
3-23
3.5 Contingency
Planning ............................. :...........................................................
3-23
3.5.1
Bioaugmentation Solution.Preparation and Injection............................3-24
3.5.2
Contingency Substrate Injection .............................. :.............................
3-25
3.6 Institutional Controls.........................................................................................
3-25
3.6.1
Ground Water.........................................................................................
3-25
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TABLE OF CONTENTS (Continued)
Page
3.6.2 Surface Water......................................................................................... 3-26
SECTION 4 - REPORTING AND DOCUMENTATION .............................................. 4-1
4.1 Corrective Measures Implementation Report ......................................................4-1
4.2 Performance Effectiveness Reports.....................................................................4-1
4.3 Periodic Remedy Reviews................................................................................... 4-2
SECTION5 - REFERENCES................................................................
LIST OF TABLES
No. Title .
1-1 Recommended Remedial Levels for COCs in Groundwater and Surface
Water at SWMU 103
1-2 Historical Detections of Contaminants in Groundwater at SWMU 103
1-3 Historical Detections of Contaminants in Surface Water at SWMU 103
3-1 Injection Protocol Summary
3-2 Year One Effectiveness Monitoring Program
LIST OF FIGURES
No. Title
1-1 Site Map and Surface Topography of SWMU 103
1-2 Confining Clay Contour at SWMU 103
1-3 Potentiometric Surface Map for Shallow Groundwater at SWMU 103
1-4 Potentiometric Surface Map for Deep Groundwater at SWMU 103
1-5 Surface Water Drainage at Fort Bragg, North Carolina
3-1 Source Area Treatment
3-2 Direct Push Injection Points at Source Area
3-3 Substrate Mixing System
3-4 Substrate Injection System
3-5 Surface Water Corrective Measure Step 1
3-6 Surface Water Corrective Measure Step 2
3-7 Surface Water Corrective Measure Step 3
3-8 French Drain and Cistern Baffle Design
3-9 French Drain and Cistern Design
3-10 Surface Water Air Sparger Design
3-11 Surface Water Air Sparger Baffle Design
3-12 Fencing and Monitoring Network
3-13 Soil Gas Monitoring Well Network at Holbrook Elementary School .
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5-1

LIST OF APPENDICES
A - Substrate Injection Calculations
B - Underground Injection Permit
C - Section 404 Nationwide Permit Number 38 Preconstruction Notification
D - Fence Specifications
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4 r LIST OF ACRONYMS AND ABBREVIATIONS
µg/L
microgram(s) per liter
1,1,2,2-TeCA
1,1,2,2-tetrachloroethane
AMSL
above mean sea level
bgs
below ground surface
BMP
Base Master Plan
cfin
cubic feet per minute
CMIR
Corrective Measures Implementation Report
CMS
corrective measures study
CAO
corrective action objective
COC
contaminant of concern
COR
Commanding Officer's Representative
CY
calendar year
DCE
dichloroethene
DERP
Defense Environmental Restoration Program
DO
dissolved oxygen
DoD
Department of Defense
DPT
direct -push technology
DPW
Department of Public Works
DS
drop structure
ft/day
feet -per day
'ft/ft
foot per foot
fft/year
feet per year
gpm
gallons per minute
GPS
global positioning system
HDPE
high -density polyethylene
HSWA
Hazardous and Solid Waste.Amendments
ID
inside diameter
LUC
land use controls
mg/L
milligram(s) per liter
Mid -Atlantic
Mid -Atlantic Associates, P.A.
MNA
monitored natural attenuation
mV
millivolts
NCDENR
North Carolina Department of Environment and Natural Resources
OD
outside diameter
ORP
oxidation-reduction potential
OSHA
Occupational Safety and Health Administration
OSWER
Office of Solid Waste and Environmental Response
Parsons
Parsons Infrastructure and Technology Group, Inc.
POC
point of contact
psi
pounds per square inch
PVC,
polyvinyl chloride
QAPP
Quality Assurance Program Plan
QC
quality control
RCRA
Resources Conservation and Recovery Act
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RFI
RCRA facility investigation
RGO
remedial goal objective
SAP
Sampling Analysis Plan
SCM
site conceptual model
SHARP
Safety, Health; and Risk Program
SPCC
spill prevention, control, and countermeasure
SWMU
Solid Waste Management Unit
TCE
trichloroethene
TEAP
terminal electron accepting process
TO
task order
TOC
total organic carbon
- USACE
United States Army Corps of Engineers
USAEC
United States Army Environmental Command
USEPA
United States Environmental Protection Agency
USGS
United States Geological Survey
UST
underground storage tank
VC
vinyl chloride
VOC
volatile organic compound
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SECTION 2
PROJECT ORGANIZATION, ROLES, AND RESPONSIBILITIES
2.1 PROJECT ORGANIZATION
This project is being conducted by Parsons under contract to the USAEC under
contract number W91ZLK-050D-0016, task order 0001 in conjunction with the Fort
Bragg DPW. The lead regulatory agency on this site is the NCDENR.
2.2 RESPONSIBILITIES AND AUTHORITIES
Parsons will serve as the Contractor for all corrective action activities specified in this
corrective measures implementation plan, and will be responsible for planning,
implementing, and documenting of engineering and corrective action activities. Parsons
will also be responsible for compliance with applicable quality control (QC), health and
safety, and regulatory requirements during the work. Parsons will report directly to
USAEC, through the Army's Contracting Officer's Representative (COR), and. may be
supported during various activities by one or more subcontractors. Subcontractors will
comply with all applicable Army and Parsons requirements. The following sections
describe the responsibilities of key Parsons project personnel.
2.2.1 Project Manager
The project manager's responsibilities will include:
• The effective execution of the Task Order (TO)/project,
• Serving as Army's and regulator's primary point of contact (POC) for the TO,
• Assigning the necessary technical and support personnel to execute their
project(s),
• Cost, schedule, and quality conformance,
• Preparing project status reports,
• Preparing any TO modifications, and participating in TO negotiations,
• Small business goal conformance, and
• Project closeout
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2.2.2 Technical Director
The technical director's responsibilities will include:
• Reviewing technical submittals for the project,
• Identifying technical expertise for project support
• Performing monthly audits of field activities
2.2.3 Site Manager
The site manager's responsibilities will include:
• Coordination with Fort Bragg personnel for site access, utility clearances, and
access to potable water from a nearby fire hydrant (if allowed under Fort Bragg
water use restrictions),
• Ensuring that this Corrective Measures Implementation Plan (CMIP) is
implemented completely and properly,
• Ensuring that all site activities are conducted safely,
• Personnel coordination, and
• Performing and documenting site audits.
2.2.4 Site Health and Safety Officer
The site health and safety officer's responsibilities will include:
• Site specific health and safety training for all Parsons employees,
• Daily health and safety -meetings,
• Daily site health and safety inspections,
• Periodic site health and safety audits,
• Maintenance of site health and safety (as well as Occupation Safety and Health
Administration [OSHA]) records, and
• Coordination of Parsons corporate health and safety audits as necessary.
2.3 ' SITE SAFETY
Parsons has implemented a Corporate Safety, Health, and Risk Program (SHARP)
which requires Project Managers to implement effective programs in these areas.
Parsons' goal is zero accidents and zero injuries with work tasks designed_ to minimize or
eliminate hazards to personnel, equipment, and the general public.
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A SHARP compliant site specific health and safety plan has been developed for this
project and is incorporated by reference (Parsons, 2007b) into this CMIP.
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SECTION 1
INTRODUCTION
1.0 INTRODUCTION
Parsons Infrastructure and Technology Group, Inc. (hereafter referred to as Parsons)
prepared this document for the United States Army Environmental Command (USAEC)
and the Fort Bragg Directorate of Public Works (DPW) under contract number W91ZLK-
050D-0016, task order 0001.. This report presents the Corrective Measures
Implementation Plan for Solid Waste Management Unit (SWMU) 103 at Fort Bragg
following the Office of Solid Waste and Emergency Response (OSWER) Directive
9902.3- 2A dated May 1994 "[Resource Conservation and Recovery Act] RCRA
Corrective Action Plan". The purpose of this document is to present the implementation
plan for corrective actions at SWMU 103.
1.1 CORRECTIVE ACTION OBJECTIVES
Contaminants have been detected in groundwater and .surface water at concentrations
exceeding North Carolina groundwater and surface water standards, indicating there is a
potential risk to human health and the environment. The corrective action objectives for
SWMU 103 are based on protection of human health and the environment. North
Carolina has established groundwater and surface water criteria for the protection of
human health and the environment (North Carolina 2L and IMAC standards and North
Carolina surface water standards, respectively). Corrective Action Objectives (CAOs)
have been developed for SWMU 103 based on the site related contaminants, physical
conditions, identification of regulatory requirements, and the baseline risk assessment.
These objectives are to:
• Prevent use of groundwater until North Carolina 2L standards are met.
• Reduce contaminants of concern (COCs) in groundwater to North Carolina 2L
standards.
• Reduce potential contact and ingestion of surface water.
• Protect surface waters from discharge of COCs at concentrations that cause surface
water to exceed North Carolina surface water standards.
The selected corrective action will consist of the application of enhanced
bioremediation technology to accelerate natural attenuation in the source area, engineered
aeration and volatilization to treat contaminated surface water, institutional controls, and
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rJ
f
monitoring. The application of these technologies will reduce contaminant
concentrations in groundwater and surface water, and will achieve the best overall results
with respect to such factors as effectiveness, implementability and cost.
1.2 DOCUMENT ORGANIZATION
The report is divided into 5 sections and 4 appendices.
• Section 1 presents the introduction, summarizes the CAOs, provides the purpose
and organization of this report and provides background information on regulatory
issues and previous investigations/actions conducted at the site. Section 1 also
covers the environmental (physical) setting at the site_.and Fort Bragg in general,
and summarizes the risk assessment -and potential impacts to human health.
• Section 2 describes project organization, responsible and authoritative parties, as
well as site, safety.
• Section 3 describes the scope of the final design, including the corrective measures
design approach,.and related construction activities and performance monitoring.
• Section 4 describes project reporting and documentation requirements.
• Section 5 provides references used in the preparation of this document.
• 'Appendix A contains the Substrate Injection Calculations.
• Appendix B contains a copy of the Underground Injection Permit Application.
• Appendix C contains the Section 404 Nationwide Permit Number 38
Preconstruction Notification.
• Appendix D contains the Fence Specifications.
1.3 FACILITY BACKGROUND
Fort Bragg, North Carolina is regulated under a Hazardous Waste Facility Permit
issued by the North Carolina Department of Environment and Natural Resources
(NCDENR) in conjunction with the United States Environmental Protection Agency
(USEPA) Region 4. One of the solid waste management units included under the permit
is SWMU 103, the former Mallonee Village Gas Station, located near the intersection of
Honeycutt Road and South Lucas Drive. The gas station was closed in 1998. Ten
underground storage tanks (USTs) were removed from the gas station prior to 1998. One
of the USTs contained waste solvents, and released chlorinated solvents into the soil and
groundwater. This chlorinated solvent contamination is being addressed under the RCRA
Permit under the designation SWMU 103. The former gas station also released
petroleum contaminants, which are being addressed under North Carolina UST
regulations.
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L.
1.4 SITE HISTORY
The Former Mallonee Village Gas Station (SWMU 103) closed in 1998, and was
located near the corner of Honeycutt Road and South Lucas Drive (Figure 1-1). With
NCDENR concurrence, the former gas station was formally designated as SWMU 103 in
calendar year (CY) 2000. Currently, SWMU 103 is an asphalt parking lot, concrete pad,
and gravel area with no trees and a few decorative shrubs. Therefore, with the
concurrence of NCDENR, there is no significant surface soil habitat for ecological
receptors at SWMU 103 proper.
The reasonably anticipated future land use of the SWMU 103 area is not expected to
change significantly from the current land use. The current land use for the area
surrounding SWMU 103 includes residential, unoccupied commercial (currently paved
areas), industrial (primarily outdoor storage and railroad), and wooded and vacant land.
Holbrook Elementary School is within the boundary of the SWMU 103 groundwater
plume.
1.5 GEOLOGY AND HYDROGEOLOGY
1.5.1 Site Geology
The following geology discussion is summarized from the RCRA Facility
Investigation (RFI) Report for SWMUs 4 and 18 (United States Geologic Survey [USGS]
,:- 1998). As discussed previously, SWMU 103 is located approximately 1,000 feet east of
. Beaver Creek and SWMUs 4 and 18; therefore, the geology would be expected to be
similar. This information has been supplemented with site -specific information gathered
from the installation of 8 soil borings for soil characterization and 53 soil borings for the
installation of 50 monitoring wells and 3 injection wells during the field investigations
performed from June 2000 to March 2005 at SWMU 103.
Geologic units in the Fort Bragg area, ranging from oldest to youngest, include the
Carolina Slate Belt rocks, which .comprise the basement rock, the Cape Fear Formation,
and the Middendorf Formation. Carolina Slate Belt rocks, which underlie the younger
sedimentary rocks, are of Precambrian and Cambrian age and are composed of
metavolcanic, metasedimentary, and igneous rock (USGS 1998). In some areas, these
rocks were exposed to weathering before the overlying sediments were deposited,
creating a zone of porous saprolite at the top of the basement rock. The)elevation of the
top of the basement rock ranges from 180 feet above mean sea level (AMSL) at Southern
Pines, near the western edge of the Military Reservation, to 110 feet below sea level near
the confluence of the Cape Fear River and Rockfish Creek (USGS, 1998). The Cape Fear
and Middendorf Formations overlie the basement rock and saprolite. These formations
are part of the generally southeastward -dipping and -thickening wedge of sediments that
constitute the Atlantic Coastal Plain deposits.
The Cape Fear Formation is composed primarily of clay interbedded with silt and silty
sand. Water in the Cape Fear Aquifer is under confined conditions. The uppermost Cape
Fear Formation consists of clay and sandy clay and ranges from 10 to 15 feet in
thickness. Twenty-seven oUthe 50 monitoring wells and all 3 injection wells installed
during the field activities for SWMU 103 were completed at the top of the Cape Fear
i
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Formation. The top of the Cape Fear Formation was observed at approximately 43 feet
below ground surface (bgs) [211.38 feet AMSL (MW-48)] to 65 feet bgs [191.5 feet
AMSL (MW-6)] in the vicinity of the source area (Former Mallonee Village Gas Station)
and 26 feet bgs [190.4 feet AMSL (MW-18)] to 36 feet bgs [179.5 feet AMSL (MW-2)]
in the area immediately east of Beaver Creek. The Cape Fear Formation was also
observed at 82 feet bgs [187.2 feet AMSL (MW-11)] upgradient of the source area.
Figure 1-2 presents an update of the clay contour (surface of the top of the Cape Fear
formation) below SWMU 103. The surface of the clay influences contaminant transport
in groundwater at SWMU 103. The clay surface has a local high or ridge that trends
from the northwest to the southeast across the site. The probable source area (Former
Mallonee Village Gas Station) is located just up gradient of this ridge on the edge of a
topographic low or trough in the clay surface. The location and size of the trough. is not
well understood. It is believed to extend from north of Honeycutt Road (MW-11) to the
south as far as the former gas station, then curve to the southeast toward Holbrook
tributary (MW-15). Wells MW-9 and MW-12 are on the east side of the trough.
The Middendorf Formation unconformably overlies the Cape Fear Formation and
forms the land surface everywhere in the area, except where it has been .removed by
erosion in the valley of Little River and its major tributaries and in part of Rockfish Creek
Valley. SWMU 103 is underlain by an alternating succession of sands, silty sands, clayey
sands, and clays of the Middendorf Formation. The Middendorf Formation at SWMU
103 ranges in thickness from approximately 20 feet (near Beaver Creek) to 80 feet (MW-
10/MW-11). Generally, the Middendorf Aquifer is unconfined at SWMU 103, although
semiconfined conditions can occur locally.
Soil types in the Fort Bragg cantonment area range from moderately well drained to
excessively well drained soils in the highly dissected uplands and have brittle loamy or
clayey subsoil. These soils are the weathered by-products of the unconsolidated sandy
sediments of the Coastal Plain. Soils located in the upland areas are generally sandy,
acidic, and low in organic matter and fertility. Soils in the lower elevations are heavier in
texture, contain more organic and clay material, and are poorly drained and swampy
when adjacent to natural waterways. Because much of the soils often have similar
properties, the transition zones are not always apparent. Several soil types are present
within the immediate vicinity of SWMU 103 ranging from loamy sand to sandy clay
1.5.2 Groundwater Hydrology
The same three geologic formations that underlie Fort Bragg also form the three fresh-
water aquifers in this area. The saprolite-basement rock aquifer is composed of the
saprolite underlying the Cape Fear Formation and the fracture zones in the uppermost
part of the metamorphic and crystalline Cambrian and Precambrian basement rock. This
saprolite-basement . aquifer is generally assumed to yield little water, and there are no
water supply wells known to tap solely into this aquifer.
The Cape Fear aquifer is composed primarily of clays interbedded with silt and silty
sands in the Fort Bragg area. The uppermost portion (5 to 10 feet) of the Cape Fear
Formation is a compact, thick clay unit that serves as an aquitard which restricts the
vertical movement of groundwater between the overlying sediments and the silty -sand
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units of the Cape Fear Formation, creating confined aquifer conditions for the
groundwater found in the Cape Fear units below. There are no potable water supply
wells in the Fort Bragg cantonment area that tap into the Cape Fear Formation; however,
east of Fort Bragg, the Cape Fear aquifer is used for both public and industrial water
supply.
The major water -bearing aquifer in the Fort Bragg area is the Middendorf aquifer,
which consists primarily of coarse -to -fine-grained silty or clayey sands with interbedded
light -gray to tan clay. Groundwater in the Middendorf aquifer is commonly under
unconfined conditions. In some areas of Fort Bragg, a laterally extensive clay layer is
present that separates the Middendorf aquifer into two water -bearing zones. The
groundwater in the Upper Middendorf remains unconfined, whereas the groundwater in
the lower zone is under confined or semi -confined conditions. The sandy soils of Fort
Bragg are highly permeable leached beds of the Upper Middendorf Formation that allow
a rapid infiltration of precipitation. Precipitation is the primary source of groundwater
recharge for the Middendorf Formation.
The depth to groundwater at SWMU 103 ranges from approximately 30 feet bgs in the
SWMU 103 source area to near ground surface adjacent to Beaver Creek. The shallow
and deep groundwater flow of SWMU 103 is toward Beaver Creek in a southerly to
southwesterly direction. The shallow and deep potentiometric maps from the September
2003 field investigation are presented in Figures 1-3 and 1-4, respectively, and are
consistent with previous investigations.
The horizontal hydraulic gradients of the shallow and deep surficial water are
approximately equal at an average of approximately 0.011 foot per foot (ft/ft) and do not
fluctuate much seasonally. Vertical gradients at SWMU 103 generally follow expected
patterns, with downward gradients in the higher topographic areas (i.e., above Honeycutt
Road) and upward gradients in the lower topographic areas (i.e., near Beaver Creek).
Variations from this pattern could be attributable to potential clay lenses producing
localized semi -confined conditions or to transient hydraulic conditions (e.g.,
precipitation). Beaver Creek represents a groundwater divide between SWMU 103 and
SWMUs 4 and 18, which are approximately 1,000 feet apart. SWMU 5 is .located
approximately 500 feet to the southwest of SWMU 4, and groundwater flow beneath this
landfill is more to the south.
The horizontal hydraulic conductivity determined from slug tests performed for
SWMUs 4 and 18 (east of Beaver Creek and the SWMU 103 area) during the RFI ranged,
from 3.2 to 42 feet per day. The wide range correlates with varying clay content in the
screened interval. The vertical hydraulic conductivity measured during the RFI for
SWMUs 4 and 18 ranged from 2.8 X 10-5 to 5.1 X 10-5 feet per day (ft/day).
Using a range of horizontal conductivities between 3.2 and 42 ft/day, an average
effective porosity of 20 percent, and a horizontal hydraulic gradient of 0.011, the average
horizontal linear groundwater velocity ranges between 0.176 to 2.3 ft/day (64 to 840 feet
per year [ft/yr]). The hydraulic conductivities determined from the wells completed in the
Lower Middendorf formation were higher overall than those from the wells completed in
the Upper Middendorf.
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1.5.3 Surface Water Hydrology
An east -west -trending ridge divides Fort Bragg into two drainage sub -basins (Figure
1-5). The northern sub -basin drains into tributaries of the Little River, while the southern
sub -basin drains into tributaries of the Cape Fear River. Surface drainage at SWMU 103,
which is in the southern sub -basin, drains into Beaver Creek and its tributaries. Beaver
Creek flows into Little Rockfish Creek which in turn discharges into Rockfish Creek, a
tributary of the Cape Fear River, which is east of Fort Bragg. Streams located on the
Military Reservation generally are low gradient and in many areas have poorly defined
channels that grade into swampy areas. Streambeds consist of unconsolidated materials,
typically silt, sand, or clay.
Several man-made impoundments are present at Fort Bragg and include Lake
McArthur in the northwestern corner of the Military reservation, McKellar's Pond in the
northeastern part of the Military Reservation, and Smith Lake in the southeastern part of
the Military Reservation. There are no natural lakes at Fort Bragg.
There are two prominent surface water features at SWMU 103: Beaver Creek and the
Holbrook tributary (Figure 1-1). Beaver Creek, a perennial stream, runs north to south
approximately 1,000 feet west of SWMU 103 and along.the eastern boundary of SWMUs
4 and 18. The natural slope of the topography on both the eastern and western sides is
toward Beaver Creek; therefore, surface. runoff from both SWMU 103 and SWMUs 4 and
18 potentially migrates to Beaver Creek. The sources of potential runoff to Beaver Creek
include SWMU 103 and SWMUs 4 and 18, the maintenance area that supports Fort
Bragg housing, a 36-inch-diameter storm water pipe outfall that transverses the northern
portion of SWMU 4 and receives storm water drainage from Knox Street, and residential
housing. The Holbrook tributary is located east and south of SWMU 103 and receives
storm water drainage from residential areas to the north, east, and south and from
Holbrook Elementary School, the former Mallonee Village Shopping Center, and SWMU
103 to the north.
The groundwater level near Beaver Creek is near ground surface, and Beaver Creek
represents a groundwater divide between SWMU 103 and SWMUs 4 and 18, indicating
that groundwater from both SWMU 103 and SWMUs 4 and 18 is potentially intercepting
Beaver Creek. Groundwater from SWMU 103 is also intercepting the Holbrook tributary.
1.6 SUMMARY OF PREVIOUS SITE INVESTIGATIONS
1.6.1 . RCRA Facility Investigation at SWMUs 4 and 18
An RFI was conducted by USGS at SWMUs 4 and 18 between 1992 and 1997, and
the results were reported in the RCRfl Faciliiylnvesligalion ofSolid #asleffanagemenl
Unils 4 and I8 Fol-I Bragg Inslallalzon Resloralion Program, Fort Bragg, North
Carolina (USGS, 1998). During the RFI, 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA) and
trichloroethene (TCE) were detected in the groundwater from 4MWS1, a background
monitoring well located east of. Beaver Creek. To assess the contamination found in .
4MWS 1 and surface water, in 1997 USGS conducted Geoprobe groundwater sampling at
14 locations east of Beaver Creek and surface water sampling at 3 locations from
tributaries of Beaver Creek. The results led to the discovery of SWMU 103.
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1.6.2 RCRA Facility Investigations at SWMU 103
Five field investigations (June/July 2000, April/May 2001, March 2002, December
2002/January 2003, and September 2003) under the RFI at SWMU 103 were used to
determine the nature and extent of contamination and refine the site conceptual model
(SCM) for SWMU 103. All of the activities performed for field investigation at SWMU
103 through CY 2003 are summarized in the SCM Report (SAIC Engineering, 2004b).
1.6.3 Supplemental Investigations for the Corrective Measures Study
The RFI for SWMU 103 (SAIC Engineering, 2004a) concluded that a corrective
measures study (CMS) was required, and that supplemental investigations and bench -
scale and in -situ pilot studies were required. The objectives for the additional field
activities for CMS for SWMU 103 were based on recommendations made in the 2004
RFI; the U.S. Army Corps of Engineers (USACE), Savannah District scope of work
dated August 10, 2004; and modification No.I to the USACE, Savannah District scope of
work dated January 28, 2005. These objectives included: installation of sentinel wells, at
Holbrook Elementary School; subsurface soil and groundwater around the former
heating -oil UST at Building 6-9344-A; groundwater sampling of monitoring wells at
SWMU 103; slug tests; bench -scale and in -situ pilot study to evaluate enhanced
bioremediation using aerobic cometabolic mechanism. All i of the supplemental
investigations performed at SWMU 103 are summarized in the CMS (Parsons, 2007a).
1.6.4 Surface Water Sampling by USACE in March 2006
Surface water samples were collected in Beaver Creek and the Holbrook tributary to
update the nature and extent of groundwater contamination intercepting these surface
water bodies. Four samples were collected in Beaver Creek and 10 were collected in the
Holbrook Tributary. - The results of the surface water sampling performed by USACE as
part of the supplemental sampling are discussed in Section 3.0 and Appendix F of the
CMS (Parsons, 2007a). Previous to the March 2006.sampling event, eleven surface water
samples were collected under the "I at SWMU 103 (four in June/July 2000, and seven
in April/May 2001). The March 2006 USACE findings did not change the conclusions of
the RFI. The most important finding was 1,1,2,2-TeCA exceeded North Carolina surface
water standards for approximately 2,200 feet of Holbrook Tributary as well as in one
sample from Beaver Creek just below the confluence of Beaver Creek and Holbrook
Tributary.
1.6.5 Soil Gas Sampling in June 2006
A total of 18 soil gas piezometers were installed in June 2006 around the perimeter of
the Holbrook Elementary School buildings and within open areas between separate
school buildings. The results of the soil gas sampling performed as part of the
supplemental sampling are discussed in Section 3.0 and Appendix F of the CMS
(Parsons, 2007a). The most significant finding from the soil gas and- crawlspace air
sampling was that the contaminants detected in these air samples (largely petroleum
compounds, alcohols, and ketones) were generally not found in groundwater. The
primary groundwater contaminants, 1,1,2,2-TeCA and TCE, were not detected in any of
the air samples. Therefore vapor intrusion of volatile organic compounds (VOCs) from
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groundwater into Holbrook Elementary School does not appear to be occurring to a
measurable extent.
1.6.6 Groundwater Sampling in June 2006
Groundwater samples were collected from three monitoring well locations around
Holbrook Elementary School and one location at the SWMU 103 source area to update
current contaminant concentrations and to evaluate the potential for vapor intrusion at the
school in conjunction with the soil gas sampling. The results of the groundwater
sampling performed as part of the supplemental sampling in June 2006 are discussed in
Section 3.0 and Appendix F of the CMS (Parsons, 2007a). The most significant finding
from the 2006 groundwater sampling event was, that 1,1,2,2-TeCA and TCE
concentrations are stable or decreasing.
1.6.8 Corrective Measures Study
Building on risk analysis from the RFI (SAIL, 2004a), the risk analysis in CMS
(Parsons, 2007a) used additional soil, groundwater, soil vapor and surface water samples
collected in CY2005 and 2006 to update human health contaminants of potential concern
for surface soil (CMS Section 3.5), -subsurface, soil (CMS Section 3.6), groundwater
(CMS Section 3.7), vapor intrusion (CMS Section 3.8), and surface water and sediment
(CMS Section 3.9), as well as ecological contaminants of potential concern (CMS
Section 3.10). This risk analysis was combined with information about the nature and
extent of contamination (CMS Sectios 3.11 and 3.12) to develop COCs . requiring
corrective action (CMS Section 3.13). Remedial goal objectives (RGOs) were
established from North Carolina 2L standards for groundwater and 213 standards for
surface water. The SWMU 103 COCs and their RGOs are presented in Table 1-1.
The COCs for groundwater are: 1,1,2,2-TeCA; chloroform; chloromethane;
tetrachloroethene; and TCE. Only VOCs originating from groundwater migrating from
SWMU 103 were considered as COCs in surface water. The only COC in surface water
requiring corrective action is 1,1,2,2-TeCA. Historical detection of contaminants in
groundwater and surface water are presented in Tables 1-2 and 1-3, respectively.
The CMS evaluated and selected the following corrective measures to remediate
volatile COCs in .groundwater and surface water at SWMU 103:
• Enhanced bioremediation using anaerobic reductive dechlorination in groundwater
in the source area, defined as the location of the former. Mallonee Village Gas
Station.
• Monitored natural attenuation (MNA) for remaining groundwater contamination.
• A step -wise application of corrective meausures technologies for the engineered
volatilization of COCs in surface water.
• Institutional controls to prevent the use of groundwater and surface water.
• Soil gas monitoring around Holbrook Elementary School.
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• Long-term surface water and groundwater monitoring.
active portion of the corrective action approach will treat
d bioremediation using anaerobic reductive dechlorination in th
immediate area ofthe tormer Mallonee—Village Gas Station) with the goal to permanently
reduce dissolved contaminant concentrations to less than 100 micrograms per liter (µg/L).
MNA will be used to further reduce the remaining groundwater contaminants to the
North Carolina 2L standards. Engineered, aeration systems to increase volatilization of
chlorinated solvents in surface water within the footprint of the SWMU 103 groundwater
plume will be installed using a step -wise approach until, surface water standards are met
at the point of compliance.
The selected corrective measures are protective of human health and environment
because COCs will be treated to meet RGOs. RGOs are established by the State of North
Carolina to protect human health and the environment. Until the corrective measures
achieve RGOs for all contaminants in all contaminated media, the corrective measures
are protective because they prevent contact with contaminated groundwater and surface
water.
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SECTION 2
PROJECT ORGANIZATION, ROLES, AND RESPONSIBILITIES
2.1 PROJECT ORGANIZATION
This project is' being conducted by Parsons under contract to the USAEC under
contract number W91ZLK-050D-0016, task order 0001 in conjunction with the Fort
Bragg DPW. The lead regulatory agency on this site is the NCDENR.
2.2 RESPONSIBILITIES AND AUTHORITIES
Parsons will serve as the Contractor for all corrective action activities specified in this
corrective measures implementation plan, and will be responsible for planning,
implementing, and documenting of engineering and corrective action activities. Parsons
will also be responsible for compliance with applicable quality control (QC), health and
safety, and regulatory requirements during the work. Parsons will report directly to
USAEC, through the Army's Contracting Officer's Representative (COR), and- may be
supported during various activities by one or more subcontractors. Subcontractors will
comply with all applicable Army and Parsons requirements. The following sections
describe the responsibilities of key Parsons project personnel.
2.2.1 Project Manager
The project manager's responsibilities will include:
The effective execution of the Task Order (TO)/project,
Serving as. Army's and regulator's primary point of contact (POC) for the TO,
Assigning the necessary technical and support personnel to execute their
project(s),
• Cost, schedule, and quality conformance,
• Preparing project status reports,
Preparing any TO mod if cations, and participating in TO negotiations,
• . Small business goal conformance, and
Project closeout
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1
2.2.2 Technical Director
The technical director's responsibilities will include:
• Reviewing technical submittals for the project,
• Identifying technical expertise for project support
• Performing monthly audits of field activities
2.2.3 Site Manager
The site manager's responsibilities will include:
• Coordination with Fort Bragg personnel for, site access, utility clearances, and
access to potable water from a nearby fire hydrant (if allowed under Fort Bragg
water use restrictions),
• Ensuring that this Corrective Measures Implementation Plan (CMIP) is
implemented completely and properly,
• Ensuring that all site activities are conducted safely,
• Personnel coordination, and
• Performing and documenting site audits.
2.2.4 Site health and Safety Officer
The site health and safety officer's responsibilities will include:
• Site specific health and safety training for all Parsons employees,
• Daily health and safety -meetings,
• Daily site health and safety inspections,
• Periodic site health and safety audits,
• Maintenance of site health and safety (as well as Occupation Safety and Health
Administration [OSHA]) records, and
• Coordination of Parsons corporate health and safety audits as necessary.
2.3 SITE SAFETY
Parsons has implemented a Corporate Safety, Health, and Risk Program (SHARP)
which requires Project Managers to implement effective programs in these areas.
Parsons' goal is zero accidents and zero injuries with work tasks designed, to minimize or
eliminate hazards to personnel, equipment, and the general public.
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k
A SHARP compliant site specific health and safety plan has been developed for this
project and is incorporated by reference (Parsons, 2007b) into this CMIP.
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SECTION 3
CORRECTIVE MEASURES IMPLEMENTATION
3.1 CORRECTIVE MEASURES DESIGN APPROACH
3.1.1 Groundwater
As selected in the CMS, the SWMU 103 groundwater corrective measures will
involve:
Source Treatment Using Enhanced Bioremediation. Enhanced anaerobic
bioremediation will be applied to the SWMU 103. source area to reduce
contaminant mass in the subsurface and reduce contaminant mass loading to
surface water. ' After the first twelve months, of performance monitoring, the
geochemical data and progress of 1,1,2,2-TeCA degradation in the source area will
be reviewed for effectiveness.
- . MNA of Remaining Groundwater Contamination. In addition to active
bioremediation in the source area, MNA will be employed to reduce contaminant
concentrations in the groundwater plume between the source area and Holbrook
Tributary. The natural attenuation period has been estimated to take as long as 60
years (Parsons, 2007a). It is probable that the impact of source treatment and
MNA will begin to reduce groundwater concentrations entering surface water
within approximately 10 years. Surface water treatment and institutional controls
to protect receptors from surface water contaminants will continue until. surface
water meets clean-up standards.
Institutional Controls. Institutional controls will include the restriction of
groundwater use at SWMU 103. Restrictions on groundwater use for consumption
and irrigation will be implemented until the RGOs are met. The administrative
and groundwater -use restrictions are implemented through. restrictions. imposed by
the Base Master Plan (BMP). Though groundwater is not currently used as a
source of drinking water at the site, institutional controls prohibiting the use of
groundwater in the future will protect human health from elevated levels of COCs
in the groundwater.
Groundwater Monitoring Network. One new monitoring well, MW-51, will be
installed to complete the groundwater monitoring network to evaluate the
performance of monitored natural attenuation.
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1,
Performance Groundwater Sampling. Groundwater at and near the source area
will be sampled quarterly during the first year following carbon substrate injection
to evaluate the performance of anaerobic reductive dechlorination. Should
additional injections be required, source area wells will be sampled quarterly for
one year as per the original injection. Thereafter, performance monitoring will be
conducted annually. Performance groundwater monitoring for MNA will initially
occur on an annual basis to evaluate the progress of the natural attenuation. The
groundwater monitoring network and frequency will be periodically assessed for
optimization, with the goal to eventually reduce sampling frequency to biennial.
• Soil Gas Monitoring. To ensure that Holbrook Elementary School is not
impacted by vapor intrusion in the future, soil gas monitoring .will be conducted
for one year at all existing representative monitoring points in the vicinity of the
school. If there is no indication of vapor intrusion, the soil gas monitoring
program will be optimized.
• Confirmatory Sampling. Confirmatory groundwater sampling will be conducted
for two years after the completion of the natural attenuation period to ensure that
the groundwater contamination has not rebounded.
• Reporting. An annual report will be issued to coincide with the results of the
sampling. If the monitoring frequency is reduced, progress reports will be issued to
coincide with groundwater monitoring.
3.1.2 Surface Water
As selected in the CMS, surface water corrective meausures will involve:
Engineered AerationNolatilization of Surface Water. Surface water will be
treated using aeration/volatilization to meet the North Carolina surface water
standard at the point of compliance (Beaver Creek at Knox Street). The
engineered aeration/volatilization systems will be implemented using a step -wise
approach to meet surface water standards:
— Step 1: Enhance the natural volatilization in the Holbrook Tributary using
three stream bed "roughening" structures (i.e., boulders). Two of the segments
will be placed within the natural stream bed, and the third will be placed within
the base flow culvert under the railroad. Monitoring near .Knox Street and
other locations over time will determine if Step 1 is adequate or if Step 2 is
required.
— Step 2: Up to five drop structures will be installed in reaches of the Holbrook
Tributary to increase retention time, surface area, and volatilization. Water
flowing over these structures will impinge on boulders and other stabilization
structures to increase volatilization. Monitoring near Knox Street and other
locations over time will determine if Step 2 is adequate or if Step 3 is required.
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Step 3: Up to two active aeration systems will be pilot tested. In the first pilot
test, base flow from the Holbrook Tributary will be pumped from the railroad
culvert effluent to Beaver Pond. At Beaver Pond, the pumped water will be
sprayed vertically to increase aeration and volatilization. If the first pilot test is
unsuccessful, the second pilot test will be implemented. The second pilot test
will be an air-sparging system that will be constructed within the Holbrook
Tributary base flow culvert at the railroad right-of-way. Monitoring near
Knox Street and other locations will determine' if the pilot systems are
successful.
- Step 4: Following Step 3, a full scale system based on pilot test data will be
implemented. Consideration will be given to life -cycle .costs since the Army
will be responsible for operations and maintenance costs long as these systems
are in place, estimated to be at least 50 years. Only one of the alternatives
described in Step 3 would be implemented at full scale.
Surface Water Sampling. Monitoring will be required during the period that
engineered aeration/volatilization system(s) are implemented. Monitoring will
include sampling above and below treatment zones quarterly for at least one year
(see section 3.4.3). Frequent sampling of the surface water will be necessary until
the surface water corrective measure technology is demonstrated to be operating as
designed.. Once that is accomplished, optimization of surface water sampling
frequency and locations may be evaluated.
i • Institutional Controls. Prevention of access to surface water at locations with
Y elevated COCs will be achieved. with a combination of signage,and new and
existing fencing.
3.2 PERMITTING AND REGULATORY COMPLIANCE
3.2.1 Hazardous and Solid Waste Amendment Permit
A Hazardous and Solid Waste Amendment (HSWA) permit is currently in place at
Fort Bragg. The Fort Bragg HSWA permit is due for renewal this year and the renewal
application has been submitted to NCDENR for review. The permit renewal application
briefly presents corrective measures planned at SWMU 103 with supporting detail
provided in this document. As part of the Fort Bragg HSWA permit renewal, the SWMU
103 corrective measures are subject to a 30-day public comment period.
3.2.2 Underground Injection Permit
A Groundwater Remediation Permit will be required for the injection activities at
SWMU 103. The remediation permit will be obtained from the NCDENR Aquifer
Protection Section through a formal application and review process. The Groundwater
Remediation Permit application for injection activities at SWMU 103 is attached as
Appendix B.
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3.2.3 Clean Water Act Permit
A USACE Section 404 Nationwide Permit Number 38 (Cleanup of Hazardous and Toxic
Waste), will be required for corrective measures in the streambed. This permit will authorize
the specific activities required to treat COCs within Beaver Creek and the Holbrook
Tributary. The Pre -Construction Notification Application for the streambed corrective
measures at SWMU 103 is attached as Appendix D.
3.2.4 Notifications
Fort Bragg DPW, NCDENR, and USAEC will be kept abreast of field schedule
developments through regularly scheduled bi-weekly conference calls. The NCDENR
Aquifer Protection Section will not typically attend the biweekly project conference calls.
Therefore the NCDENR Aquifer Protection Section Representative (Qu Qi) will be
updated periodically by Parsons or by the project NCDENR representative (Marti
Morgan).
3.2.5 Storm Water Pollution Prevention
It is anticipated that the ground surface and related vegetation at SWMU 103 will be
disturbed only minimally during injection activities at the source area because drilling
activities will be limited to direct push drilling and vehicle traffic off currently
established roads will be minimal. Thus, a storm water pollution prevention plan is not
required for this effort.
3.2.6 Spill Prevention, Control, and Countermeasures
Oils stored on -site (soybean oil) are subject to regulation under 40 CFR 112, Oil
Pollution Prevention. The total volume of vegetable oil stored on site will be greater than
the 1,320 gallon limit specified in the Spill Prevention, Control, and Countermeasure
(SPCC) regulations under 40 CFR 112 Subpart C. The emulsion product and pH buffer
also planned for injection at SWMU 103 do not fall under this regulation as these
products do not have similar physical properties as oil (e.g., solubility and density) and
the volumes of these products stored on site will be relatively low (less than 1,320
gallons).
A SPCC plan for both SWMU 69 and SWMU 103 will be developed and published
under a separate cover.
3.3 CORRECTIVE MEASURES CONSTRUCTION'ACTIVITIES
3.3.1 Monitoring Well Network
3.3.1.1 Mobilization
Mobilization activities will commence upon acceptance of the final SWMU 103 CMIP
and the receipt of all required permits and authorizations as discussed in Section 3.2.
Mobilization activities will consist of the following tasks:
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• Coordination of utility clearances for all drilling locations.
• Site access coordination with Fort Bragg. The intended drilling areas are not
located in high security or limited access areas. However, facility coordination
will be necessary for proper'sighting of equipment and materials.
• Mobilization of a drilling contractor to support the hollow stem well installation
activities.
3.3.1.2 Monitoring Well Installation
One new monitoring well, MW-51, will be installed to complete the groundwater
monitoring network required to evaluate the performance of the natural attenuation
alternative. The location of the new monitoring well is along Sharpe Drive between MW-
29 and MW-31, as presented in Figure 3-1.
Monitoring well MW-51 will be installed using hollow stem auger drilling methods
and will be constructed of two inch inside diameter (ID) polyvinyl chloride (PVC) well
materials. The MW,51 boring will be advanced to the contact of the Middendorf
Formation and the Upper Cape Fear Confining Unit (an estimated 45 feet bgs at MW-51)
using 4-1/4 inch ID hollow stem augers. After -the augers reach termination depth the
monitoring well.will be installed inside the auger, the augers will be withdrawn, and filter
sand (#10-20) will be emplaced within the annular space,;between the outside of the PVC
- ` t screen and the inside of the borehole to a level approximately 2 feet above the top of the
10-ft PVC screen. The remaining annular space .will be sealed with approximately 2 feet
of bentonite chips immediately above the sand filter pack and concrete/bentonite grout,
from the top of the bentonite chip seal :to approximately 2 feet below ground surface.
The top of the casing will be finished with the installation of a water tight "J-plug" cap
within a steel "stick-up" type surface completion set in a concrete collar.
The installation of new permanent monitoring well MW-51 will be . conducted in
accordance with North Carolina State regulations as specified in Subchapter 2C Section
.0100of the North Carolina Administrative Code.
3.3.1.3 Site Restoration
After well installation is complete, any area that was disturbed by this activity will ,be
returned to pre -mobilization condition. It is expected that site restoration activities will
be limited to filling in ruts and planting grass seed. Major disturbances are not expected
because there will be.no off -road vehicle usage.
3.3.1.4 Final Site Survey
The new permanent monitoring well location will be surveyed by a state licensed :land
surveyor. . All new well location data will be presented in the Corrective Measures
Implementation Report (CMIR).
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3.3.2 Enhanced Bioremediation in Source Area
3.3.2.1 Mobilization
Mobilization activities will commence upon acceptance of the final SWMU 103 CMIP
and the receipt of all required permits and authorizations as discussed in Section. 3.2.
Mobilization activities will consist of the following tasks:
• Coordination of utility clearances for all drilling locations.
• Site access coordination with Fort Bragg. The intended drilling and injection areas
are not located in high security or limited access areas. However, facility
coordination will be necessary for proper sighting of equipment and materials.
Delivery of organic substrates and injection equipment.
• Mobilization of a drilling contractor to support the direct push well installation and
injection activities.
3.3.2.2 Organic Substrate Injection
The purpose of applying enhanced anaerobic bioremediation technology to the
S WMU ,103 source area is to reduce contaminant mass present in the subsurface and
thereby reduce long-term contaminant mass loading to Holbrook Tributary and Beaver
Creek. An injection well network in the source area will consist of 36 direct push
injection points and temporarysmall diameter injection wells. Based on the radial flow
in the deep groundwater, this design should produce anaerobic conditions in a 10,900-
square foot treatment area beneath and in the vicinity of the former solvent UST (Figure
3-2).
Based on a review of available boring logs compiled in the SWMU103 source area the
top -of -clay surface slopes downward toward the northeast and southwest from a high
located in the vicinity of existing well MW-48. The .clay high at MW-48 is located at
approximately 44 feet bgs and slopes downward to approximately 52 feet bgs at MW-50
and 56 feet bgs at MW-23. The water table in the source area is relatively consistently
located at approximately 32 feet bgs. The difference between the depth to the water table
and the depth to the underlying confining clay unit represents the unconfined Middendorf
Aquifer and ranges in thickness from a minimum of 11 feet at MW=48 and a maximum of
24 feet at MW-23. Organic substrate will be injected throughout most of the Middendorf
aquifer thickness such that a majority of the saturated thickness within the source area
becomes an enhanced bioremediation treatment . cell. Organic substrate 'will be
concentrated near the bottom of the saturated thickness of the Middendorf aquifer where
the highest concentrations of 1,1,2,2-TeCA have historically been detected.
After the first twelve months of performance monitoring, the geochemical data and
progress of 1,1,2,2-TeCA in the source area will be reviewed. The goal of the organic
substrate injection is to achieve less than 100 µg/L 1,1,2,2-TeCA concentration within the
source area. A second injection of organic substrate may be applied to the SMWU 103
source area in the event that:
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• concentrations of chlorinated VOCs remain or rebound above 100 µg/L,
TOC concentrations decline to less than 20 mg/L, and
data indicate that dechlorination has halted or is not occurring (e.g.; parent
compound molar fraction increases to nearly 100% and daughter product molar
fraction decreases to near 0%).
The purpose of implementing the second injection is to provide additional carbon
substrate if the original injection successfully enhances biodegradation but the target area
becomes depleted of carbon substrate (see section 3.5).
3.3.2.2.1 Substrate Injection Wells
A total of 36 injection locations will be installed in the SWMU 103 source area.
Eighteen of these points will be installed as temporary small diameter PVC wells. The
temporary PVC injection wells will consist of 0.75-inch or 1-inch ID PVC injection wells
installed using either a Parsons -owned direct push rig or a subcontracted direct push rig.
Approximate locations and installation details of the temporary injection wells are
addressed on Figure 3-1 and in Table 34.
The location and depth of the injection points are designed to target the highest
concentrations of 1,1,2,2-TeCA in the source area, found in the Middendorf aquifer near
f the top of the Upper Cape Fear Confining Unit. To ensure adequate vertical distribution
of substrate, the depth of each temporary injection well will vary based on field
observations. Approximately one half of the temporary wells will be set on the top of the
Upper Cape Fear Confining Unit. For the remainder of temporary injection wells, the
bottom of the screened interval will be based five feet above the top of the Upper Cape
Fear Confining Unit, within the Middendorf Formation.
The temporary injection wells will be constructed with screen lengths of up to 10 feet.
The direct -push technology (DPT) equipment will advance 2-1/8-inch outside diameter
(OD) steel casing to the top of the Upper Cape Fear Confining Unit. The steel outer
casing will be outfitted with an expendable tip. After the steel DPT casing has been
advanced to approximately 1-foot below the bottom of the intended screen interval, the
steel casing will be pulled back approximately 1-foot to dislodge the expendable steel
point. After the expendable point has been dislodged, the well will be installed inside the
DPT casing. The injection points will be constructed with screen lengths of
approximately 10 feet.
Each injection well will consist of 10 feet of 3/4-inch or 1-inch ID machine slotted
Schedule 40 PVC screen flush threaded to the appropriate length of non -slotted riser pipe.
The riser pipe will extend from the top of the screen interval to approximately 2-feet
above ground surface. The entire well stick, consisting of PVC screen and casing will be
installed inside the steel DPT casing and the steel casing will be withdrawn to allow the
natural formation material to collapse around the injection well. After the steel DPT
casing is withdrawn, the depth to natural collapse will be measured using a steel tape
attached to a sounding weight. In the event that natural soils do not collapse around the
s screened interval, a sandpack consisting of new, clean 20-40 silica sand will be installed
t
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in the annular space around the screen. The remaining open annular space will be filled
with a bentonite concrete sanitary seal from the top of either natural collapse or the
installed sandpack to the ground surface. Once each well is installed, a threaded cap will
be installed in the top of the well casing to seal the well.
Each injection well will be completed with a temporary PVC surface casing to protect
the injection well from potential damage. The temporary PVC surface casing will consist
of a 5-foot section of 4" PVC schedule 40 pipe that will be installed around the injection
well and buried in the ground to approximately 2-3 feet in depth. A bentonite surface
sanitary seal will be installed at the bottom of the surface completion to keep surface
water from infiltrating down the borehole. A threaded PVC cap will be installed at the
top of the completion casing to seal the completion.
3.3.2.2.2 Substrate Direct Injection Points
Substrate will be injected into the subsurface directly through temporarily installed
steel GeoprobeTM rods and screen point sampling tools at one half of the injection
locations (18). The location and depth of the direct injection wells are designed. to target
the highest concentrations of 1,1,2,2-TeCA in the source area, found near the top of the
Upper Cape Fear Confining Unit. To ensure adequate vertical distribution of substrate,
the depth of each injection point will vary based on field observations. Approximately
one half of the injection points will be set in the Middendorf aquifer at the top of the
Upper Cape Fear Confining Unit. For the remainder of points, the bottom of the screened
interval will be based five feet above the top of the Upper Cape Fear Confining Unit, - .l
within the Middendorf Formation. Substrate injection at these direct injection locations
will be conducted in the same way as the injection wells except that the substrate will be , _f
injected into the subsurface directly through the GeoprobeTM rods instead of through PVC
well casings. The GeoprobeTM. rods and associated tool string will be removed after
injection activities are complete at each point and thus will not remain in the ground for
more than a few days.
3.3.2.2.3 Substrates
The injection fluid that will be deployed at SWMU 103 will consist of a four part
emulsion. The injection fluid will consist of approximately 68,400 gallons of water,
5,060 gallons of neat soybean oil, 820 gallons of a pre -mixed soybean oil -in -water
emulsion product (containing soybean oil and sodium lactate), and approximately 750
gallons of pH buffering product.
The injection fluid was designed specifically for the source area at SWMU 103 by first
calculating the geometric and hydraulic properties of the intended injection area such as
the cross sectional area, the intended lateral dimensions, volume of pore water present
during injection, and the volume of groundwater that will flow through the treatment
zone during the intended life expectancy of 10 years. These properties were then used to
calculate the hydrogen demand that must be met to deplete competing electron acceptors
(e.g., dissolved oxygen [DO], nitrate, and carbon dioxide) as well as the hydrogen
demand required to reductively dechlorinate the contaminant mass present at the injection
area. A safety factor of 20X was then applied to develop a conservative hydrogen
loading requirement that is sufficient to deplete all known electron acceptors as well as
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any potential unknown or unquantifiable inefficiencies or electron consumers. The total
hydrogen demand was than converted to substrate demand by dividing the hydrogen
demand (in moles of molecular hydrogen) by the production capacity of the sum of the
individual electron donors. The resulting substrate donor demand and the hydraulic
characteristics of the injection area were then used to design the actual injection fluid for
the injection area such that the intended treatment area is achieved. The design
calculations for the injection area are presented in Appendix A and ,are summarized in
Table 3-1.
Neat.Soybean Oil
Food -grade soybean oil and liquid lecithin will be obtained from a commercial
supplier such as Solae, Inc. of Fort Wayne, Indiana. Vegetable oil and lecithin are food -
grade materials extracted from soybeans and are used in the food industry for a wide
variety of applications. A -soybean oil -lecithin mixture with a ratio of 10 pounds'soybean
oil to 0.25 pound lecithin will be prepared by the vendor prior to shipment to Fort Bragg.
Pure soybean oil/lecithin emulsion will be shipped in bulk tanker trailers (40,000 pound
loads).
Soybean oil is relatively insoluble in water, thus lecithin is added as an emulsification
agent so that the soybean oil can be emulsified with water prior to injection. This
emulsification step is taken to increase the injection volume (e.g., 1 part oil and 9 parts
water) without increasing the vegetable oil volume. The result is that a relatively small
r " 1 volume of vegetable oil (5,060 gallons) can be distributed into a relatively large volume
of aquifer matrix (approximately 220,000 cubic feet). This will distribute vegetable oil
such that the vegetable oil occupies only a small portion (7 percent) of the interstitial void
spaces of the aquifer matrix. In this way, the distributed vegetable oil does not impede
groundwater flow.
After injection,. the vegetable oil -in -water emulsion will ultimately break and be
distributed as small droplets of oil trapped within the aquifer matrix. This entrapped oil
does not migrate with advective groundwater flow, rather it remains in place as a
relatively immobile, slowly soluble, long-term source of organic carbon.
Soybean Oil -in -Water Micro -Emulsion Product
A portion of the soybean oil loading that will be injected at SWMU 103 will be added
in the form of a soybean oil -in -water micro -emulsion product. This product will be
shipped to Fort Bragg as a pre-processed micro -emulsion with an oil droplet size of less
than one micron, which is considerably smaller than the 10 to 20 micron median droplet
size of the field mixed emulsion discussed above. The extremely small droplet size of the
micro -emulsion product allows the soybean oil associated with this product to travel short
distances in the direction of groundwater flow after injection. The travel distance is
typically on the order of 20 to 50 feet depending on the groundwater flow velocity and
the mean pore throat size of the soil matrix. It is expected that the migration distance at
SWMU 103 will be toward the lower end of that range due to the relatively low
groundwater flow rates calculated for the SWMU 103 source area. The migration of the
micro -emulsion product will result in the expansion of the enhanced bioremediation
ti
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treatment area, the extension. of the residence time in the treatment area, and increased
treatment efficiency.
pH Buffering Product
A pH buffering product consisting of a mixture of proprietary, naturally occurring, and
long lasting buffering agents, water, dispersants, and food grade preservatives will be
injected into the subsurface at SWMU 103 along with the organic substrates. The pH
buffering product will be added to support pH conditions in the neutral range by
neutralizing naturally occurring acidic compounds as well as organic acids produced
during the fermentation of the vegetable oil. pH conditions must be supported above
approximately pH 6.0 in order for biotic reductive dechlorination to occur efficiently
(Volkering and Pijis 2004).
Injection Water
Potable water will be used in conjunction with extracted site groundwater to dilute the
organic substrates prior to injection. If possible, potable water will be obtained from a
nearby fire hydrant. If Fort Bragg water use restrictions prohibit use of fire hydrant
water, potable water will be purchased off -post, trucked to the site and stored in, a 20,000
gallon frac tank. The make-up water will be characterized to provide information on
potential contaminants introduced into the subsurface from the injected water. Potable
water and groundwater will serve as a dispersant for the soybean oil -in -water emulsion as
well as a carrier for the pH product. Approximately 91 percent of the total fluid that will
be injected at SWMU 103 will be water. The injection fluid will consist primarily of
water in order to ensure adequate distribution of the organic substrates to avoid
physically clogging soil pore throats with soybean oil or the development of excessive
biofouling, which would cause an unacceptable decrease in site soil permeability and
result in groundwater flow deflection. It is expected that approximately 50 percent of the
makeup water for the injections will consist of potable -water with the remaining
consisting of untreated groundwater. However, if groundwater cannot be extracted from
existing SWMU 103 wells at a reasonable rate then a larger percentage of potable water
may be used to maintain the project schedule.
3.3.2.2.4 Substrate Preparation and Emplacement
Substrate injection activities will begin with the delivery and staging of the or
substrates and the setup of a portable injection system, at SWMU 103. The injection
system will be shipped to Fort Bragg on one or two pallets and will be setup in a rental
cargo van to protect the system from inclement weather. The injection system will be
staged in the open area immediately east of the former Mallonee Village Gas Station area
(west of South Lucas Drive) in close proximity to an existing fire hydrant.
Potable water will be supplied to the injection system from a 20,000 gallon frac tank.
The frac tank will be filled with potable water from either a nearby fire hydrant or with
potable water trucked in from off -post, depending on Fort Bragg water use restrictions. If
the fire hydrant is used, it will be connected to the frac tank with a temporary high
density polyethylene (HDPE) line (Figure 3-3). The line will be connected to the fire
hydrant only when the tank is being filled, and backflow will be prevented through the
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use of an air gap that will be at least twice the diameter of the fill pipe as required by
ASME Al12.1.2—1"1,Air Gaps In Plumbing Systems. The organic substrates and the
pH amendment product will then be added to the potable water at the correct dosage rate
inline through a series of dosimeters. A static high sheer in -line mixer will be used to
emulsify the soybean oil -lecithin mixture and potable water to form an oil -in -water
emulsion. This oil -in -water emulsion will then be pumped to the injection area with an
air operated diaphragm pump through HDPE conveyance lines. The system that will be
staged in the Former Mallonee Village Gas Station parking lot is depicted in Figures 3-3
and 3-4.
Within the injection area, site groundwater will be extracted from existing
groundwater monitoring wells for re -injection with the oil -in -water emulsion being piped
from the parking lot staging area. Submersible pumps will be temporarily installed in
one or two monitoring wells to supply site water for injection. The discharge lines from
the submersible pumps will be tied in to the supply line coming from the injection system
through a manifold consisting of valves and flow meters designed to measure flow from
the groundwater extraction pumps and flow coming from the injection system (Figure 3-
4). The mixtures of site groundwater and potable water will depend on the rate at which
groundwater can be extracted from the formation. However, the final mixture of organic
substrate and water will conform to the design calculations summarized in Table 3-1 and
presented in Appendix A.
After, the oil -in -water emulsion from the injection system has been diluted with site
groundwater pumped from nearby wells, the emulsion will be injected into a combination
of temporary injection wells and injection points. It is expected that the total oil -in -water
emulsion flow (20 gallons per minute [gpm]) will be split so that substrate can be injected
into four to six injection locations at the same time (3 to 5 gpm per location). Substrate
injection will start at each location at a relatively low rate for the first 5 to 10 minutes to
ensure that all aspects of the system are in order. During that period, system pressures
will be monitored and flow rate adjustments will be made as needed to avoid excessive
pressure which could constitute a safety hazard. Removal of all air from the system will
be ensured by checking the air release vents installed on each of the injection location
risers.
Once this initial volume of substrate is injected, the injection rate will be increased to
the maximum rate possible without exceeding safe operating pressures. or the overburden
pressure of the formation (<40 pounds per square inch [psi]). After the appropriate
volume of the emulsion has been injected into the subsurface the emulsion flow will be
stopped and system pressure will be reduced to zero prior to disconnecting any injection
lines.
Assuming the volumes of emulsion/water mixture presented in Table 3-1 can be
successfully injected into the formation equally and radially along the entire length of
each injection screen interval, and assuming 15 percent effective porosity in the
subsurface, this should provide a column of substrate (evenly distributed as droplets
throughout the aquifer material) approximately 11 to 12 feet. in diameter around each
substrate injection well. The effective oil saturation in the subsurface after injection is
complete is targeted at approximately 7 percent of the effective porosity. During the
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course of injection, water samples from downgradient wells will be monitored with a
clear bailer to check for emulsion breakthrough.
After the process has been completed, the presence of phase -separated oil emulsion in
the substrate injection wells and the impact on the groundwater table elevation will be
measured with an oil -water interface probe. The presence of vegetable oil or vegetable
oil emulsion in nearby wells will also be monitored visually by collecting samples with a
clear polyethylene bailer.
3:3.2.3 Site Restoration
After well installation and substrate injection activities are complete, any areas that
were disturbed by these activities will be returned to their pre -mobilization state. It, is
expected that site restoration activities will be limited to filling in ruts and planting grass
seed. Major disturbances are not expected because off -road vehicle usage will be limited
to a pickup truck mounted direct push drilling rig and potentially a small site support
vehicle.
3.3.2.4 Final Site Survey
After well installation and substrate injection activities are complete all well locations
will be surveyed. Injection well locations will be surveyed by Parsons using a global
positioning system (GPS) or by taping from existing well locations. A Well Completion
Record will be submitted to Fort Bragg for the permanent monitoring well MW-51 to be
installed along Sharp Drive east of Holbrook Tributary. All new well location data will
be presented in the CMIR.
3.3.3 Surface Water Remedy
3.3.3.1 Mobilization
Mobilization activities will commence upon acceptance of the final SWMU 103 CMIP
and the receipt of all required permits and authorizations as discussed in Section 3.2.
Mobilization activities will consist of the following tasks:
• Coordination of utility clearances at all drop structures and other subsurface
construction locations.
• Coordination with Fort Bragg DPW for controlled brush burning as necessary to
install and maintain fences.
• Site access coordination with Fort Bragg. The intended surface water corrective
measures areas are not located in high security or limited access areas. However,
facility coordination will be necessary for proper siting of equipment and
materials.
Delivery of surface water corrective measures supplies and equipment.
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3.3.3.2 Aeration/Volatilization Systems Installation
Volatilization of VOCs occurs in the streams under ambient conditions. In -stream
engineered aeration and volatilization technologies for removing VOCs in surface water
are low -technology systems that facilitate gas transfer. Monitoring in April 2007 shows
that 1,1,2,2-TeCA concentrations in Beaver Creek decrease (presumably through multiple
processes including dilution, volatilization, and biodegradation) to meet North Carolina
surface water standards somewhere between Knox Street and Gruber Road. Because
1,1,2,2-TeCA migrates beyond the known footprint of the groundwater plume at
concentrations greater than the North Carolina. surface water standard, engineered
aeration and volatilization at SWMU 103 is necessary to attain the surface water
standard.
The conceptual model for the hydrology and contaminant transport of 1,1,2,2-TeCA in
the Holbrook tributary and Beaver Creek is that the majority of contaminated water flow
appears to be in the Holbrook tributary. The combined base flow is relatively low at an
estimated 150 to 180 gpm. The concentration of 1,1,2,2-TeCA in surface water where
Beaver Creek flows under Knox Street is < 8.6 µg/L (relative to the surface water
standard of 4 µg/L). Engineered in -stream aeration and volatilization is a .feasible
approach to meet the surface water standard at this location. A step -wise approach will
be taken toward implementation of engineered in -stream aeration and volatilization
technologies.
3.3.3.2.1 Step 1 - Roughen Streambed
The surface water corrective action approach involves four steps of increasing
corrective action to attain the surface water standard. The first step or surface water
corrective action strategy is to "roughen" the stream bed. Three segments of the
Holbrook Tributary stream bed will be roughened with boulders or paving stones to
increase turbulence, surface mixing, and volatilization (Figure 3-5). The three..segments
are areas with the greatest existing grade and generally experience higher flow velocities.
The segments are:
207-foot section of Holbrook Tributary in the base flow (south -trending) culvert
under the. railroad right-of-way (Stations 17+31 to 19+36). This section will be
roughened by placing paving stones in a staggered pattern on the culvert bottom.
• 42-foot section of Holbrook Tributary below South Lucas Drive, (Stations 20+56
to 20+98). This section will be roughened with one layer of Type 1 granite rip/rap
(12"-16") as available from local quarry..
• 55-foot section of Holbrook Tributary above Sharp Drive (Stations 32+24 to
32+79). This section will be roughened with one layer of Type 1 granite rip/rap
(12"-16") as available from local quarry...
Three 12-inch paving stones will be needed for every four -feet of culvert (150 paving
stones total). Twelve -inch boulders will be placed directly in the stream bed for the other
two sections, totaling 97-feet of stream bed estimated at six feet wide by one -foot deep or
22 cubic yards of boulders for the two sections. Both segments will be approximately as
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wide as the stream channel. The as -built volume of each segment will depend on the
characteristics of the stream in the immediate vicinity. Local sources will supply and
deliver the boulders and paving stones. The segments will be constructed by small
backhoe and/or manual labor.
Quarterly surface water monitoring at the compliance point (Knox Street) will
continue for at least one year to determine if Step 1 is sufficient to reduce 1,1,2,2-TeCA
to the surface water standard, or if Step 2 is required.
3.3.3.2.2 Step 2 - Drop Structures
If the surface water standard of 4 gg/L at Knox Street is not met by Step 1, the surface
water corrective action approach will proceed to Step 2. Step 2 consists of installing
sheet -pile drop structures (similar to those that already exist in Holbrook tributary) in
reaches of the Holbrook Tributary that typically have low velocity flow. The drop
structures will increase the retention time and surface area, and therefore volatilization, of
upstream surface water, and may increase aeration and volatilization downstream. Rocks
placed below each drop structure will increase volatilization as water impinges on the
rocks after it crests the drop structure.
Five potential locations for drop structures have been selected (Figure 3-6):
• Drop structure (DS) 1 — Beaver Creek at Station 11+00 (100 feet upstream of
Knox Street)
• DS 2 — Holbrook Tributary at Station 20+56 (upstream of the railroad culvert)
• DS 3 — Holbrook Tributary at Station 25+51 (raising existing weir behind
Holbrook Elementary School)
• DS 4 — Holbrook Tributary at Station 30+10 (downstream of Sharp Drive behind
Holbrook Elementary School)
• DS 5 — Holbrook Tributary at Station 32+79 (upstream of Sharp Drive)
Construction of drop structures will proceed in phases to achieve the surface water
standard. Initially, the two drop structures with the greatest chance of success (DS 1 and
DS 5) will be installed. Surface water monitoring over time will determine if these two
drop structures are sufficient to reduce 1,1,2,2-TeCA to the surface water standard. If the
first two drop structures do not achieve the surface water standard, but are determined to
be driving 1,1,2,2-TeCA concentrations toward the surface water standard, drop
structures at the other three sites may be considered.
The drop structures will be designed to focus the base flow discharge (less than 180
gpm) through one or more notches in sheet piling in order to measure surface water
discharge and direct the flow onto boulders below the drop structure. The height of each
drop will be less than 18 inches above stream grade to minimize effects of the retained
surface water on the natural stream flow (e.g., excessive sedimentation, ponding), while
still creating a significant drop to increase aeration.
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The drop structures will be constructed of sheet steel driven vertically into the stream
bed perpendicular to flow, and will extend across the stream channel. Each section of
sheet steel will be driven up to three feet below grade, and the width will be between the
banks of the channel. One layer of Type 1 granite rip/rap (12"-16") as available from
local quarry will be placed on the downstream side of each drop structure to reduce scour
and to provide an impinging surface to increase volatilization. The as -built dimensions of
each drop structure will depend on the characteristics of the stream in the immediate
vicinity.
Quarterly surface water monitoring at the compliance point (Knox Street) will
continue for at least one year to determine if Step 2 is sufficient to reduce 1,1,2,2-TeCA
to the surface water standard, or if Step 3 is necessary.
3.3.3.2.3 Step 3 - Pilot Testing Active Aeration
If Step 2 is not successful at reducing 1,1,2,2-TeCA concentrations to the' surface
water standard at Knox Street, up to two active aeration systems will be pilot -tested
(Figure 3-7). In the first pilot test, base flow from the Holbrook Tributary will be
pumped from the railroad culvert to Beaver Pond. At Beaver Pond, the pumped water
will be sprayed vertically to increase aeration and volatilization. If the first pilot test is
not successful at reducing 1,1,2,2-TeCA, the second pilot test will be implemented, in
which an air-sparging system will be constructed within the Holbrook Tributary base
flow culvert at the railroad right-of-way. The pilot tests would be conducted sequentially
over a period of months. Surface water monitoring at the compliance point (Knox Street)
will determine the efficacy of each pilot test to reduce 1,1,2,2-TeCA to the surface water
standard.
Aeration of base flow at Beaver Pond
The first pilot test will volatilize 1,1,2,2-TeCA by pumping base flow from the
Holbrook Tributary to Beaver Pond (on Beaver Creek), then aerating the pumped
discharge with a fountain at Beaver Pond. Beaver Pond is a 1.7 acre, perennial surface
water feature of the Beaver Creek watershed. It is located within the project boundary
approximately one quarter mile southwest of the source area.
Base flow discharge of Holbrook Tributary is estimated at 150 to 180 gpm: The
Holbrook Tributary stream channel widens downstream, and after passing under Sharp
Drive, base flow meanders over stream bed deposits. Approximately 300 feet upstream
of its confluence with Beaver Creek; the Holbrook Tributary (at Station 19+36) passes
under the railroad right-of-way through three culverts, each four feet in diameter. The
southernmost culvert has the lowest invert elevation and carries the Holbrook Tributary
base flow south under the railroad, and continues south, to a confluence with Beaver
Creek. The other two culverts have higher entrance .elevations and carry the flood flow
west under the railroad, and continue west in a more direct path to a confluence with
Beaver Creek.
Plywood and sandbag baffles will be constructed across the entrances of two culverts
to direct flow toward the pumping cistern. A baffle will be constructed across the
entrance to the base flow culvert to a height of 0.83 feet above the invert. This baffle will
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divert base flow from Holbrook Tributary into the northernmost culvert. A baffle will be
constructed across the entrance to the northernmost culvert from 0.83' to 1.69'. The
baffle on the northernmost culvert is designed. to accept up to four inches of water. If
more than four inches of water are flowing in the Holbrook Tributary, the additional flow
will be diverted to the middle and southern culverts. The middle culvert will not be
baffled (Figure 3-8). The purpose of these baffles is to direct flow to the corrective
measure system while protecting that system from damage due to high velocity flood
waters. Should this step be necessary and selected as the final remedy, these baffles will
be permanently constructed by anchoring steel plates to the concrete headwalls.
A French drain and cistern will be installed near the downstream opening of the
northernmost culvert. The cistern will be constructed from 4-feet diameter metal culvert,
perforated so that water can enter through the sides. It will be approximately 4-feet deep,
and will be installed such that its top surface will rise slightly above the streambed
(Figure 3-9). The gravel pack (French drain), constructed of pea gravel, will be installed
around the cistern so that the Holbrook Tributary base flow will infiltrate through gravel
pack and screened walls of the cistern. A 150 gpm capacity submersible pump will be
installed inside the cistern. The pump will be powered from an existing overhead power
line at the railroad right-of-way. The pump will be controlled by a float switch; the
pumping capacity will relate directly to the water level inside the cistern. The pump will
shut down if an insufficient amount of water exists within the cistern. During periods of
high flow, stream discharge in excess of 150 gpm will flow through the other two
culverts and down their existing stream channels until the flow is high enough to overtop
the baffle at the northern culvert. This design will protect the system while conserving
the flood water carrying capacity of the three culverts.
The captured base flow will be pumped approximately 600 feet from the cistern to
Beaver Pond. Piping will be made of high density polyethylene, and will follow as direct
path as possible to Beaver Pond. The pumped water will be sprayed vertically by
fountain into Beaver Pond to increase aeration and volatilization. The hydraulic impact
of this pilot test is that base flow from Holbrook Tributary will discharge into Beaver
Creek about 700 feet upstream from its current confluence. Increased retention time
within Beaver Pond will enhance volatilization and potentially biodegradation of 1,1,2,2-
TeCA. Surface water monitoring at the compliance point (Knox Street) over time will
determine if the pumping system is sufficient to reduce 1,1,2,2-TeCA to the surface water
standard.
Air-Sparging
If necessary, the second system will pilot test the efficacy of an air sparger located
within the base flow culvert where Holbrook Tributary passes under the railroad (Station
19 + 36). The second pilot test will only be conducted if the first pilot test is
unsuccessful.
The air-sparging system will cover about 100 feet of the base flow culvert length with
two sections of nine sparging pipes (Figure 3-10). Each section will be controlled by a
separate valve. Within each section, the sparging pipes will be constructed of 50 foot
lengths of three-inch steel pipe offset two inches laterally, making the final dimension of
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the air-sparging system 100 feet by 4 feet. Each sparging pipe will have 1/8-inch holes
placed two inches apart.
The system will be powered by a 2500 cubic foot per minute (cfin) blower located at
the downstream opening of the base flow culvert. For the purposes of pilot testing, the
blower will be powered using a portable generator capable of 440V. One week of pilot
testing will determine the optimal air flow rate with respect to reducing 1,1,2,2-TeCA
concentrations and power requirements. Should this step be necessary and selected as the
final remedy, the blower will be powered from an existing overhead "power line at the
railroad right-of-way.
A plywood and sandbag baffle will be constructed at the entrance and exit of the base
flow culvert. The entrance will.,be baffled from 0.38-feet to 1.5-feet from the bottom of
the culvert, allowing a 0.38-feet interval for base flow to enter the culvert. The baffle at
the exit will rise 1.4 feet from the base, and is designed -to pond water within the culvert
and increase the residence time and depth of water for sparging (Figure, 3-11). The
purpose of the baffle system is the same as described above. Should this step be .
necessary and selected as the final remedy, these baffles "will be permanently constructed
by anchoring steel plates to the concrete headwalls.
3.3.3.2.4 Step 4 - Full Scale Active Aeration
Following Step 3, the most efficient system based on pilot test data will be
implemented at full-scale. Consideration will be given to life -cycle costs since the Army
will be responsible for operation and maintenance costs as long as these systems are in
place; estimated to be at least 50 years. Only one of the, alternatives described in Step 3
would, be implemented at full "scale. Pilot test equipment for the Step 3 alternative that is
not implemented at full scale during Step 4"would be removed.
3.3.3.3 Site Restoration
After surface water corrective measure "activities are complete, any, areas that were
disturbed by these activities will be returned to their pre -mobilization state. It is expected
that site restoration activities will include filling in ruts, backfilling two short roads that
will be constructed down to the stream bed, and planting grass seed.
3.3.3.4 Final Site Survey
The location of surface water corrective measure systems will be, surveyed after all
activities are complete. All location data will be presented in the CMIR.
3:3.4 Fencing and Signs
3.3.4.1 Mobilization
Mobilization activities will commence upon acceptance of the final SVIW 103 CMIP
and the receipt of all required permits and authorizations as discussed in Section 3.2.
Mobilization activities will consist of the following tasks:
� y
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• Coordination of utility clearances at all fence construction locations.
• Site access coordination with Fort Bragg. The intended fenced areas are not
located in high security or limited access areas. However; facility coordination
will be necessary for proper sighting of equipment and materials.
3.3.4.2 Fencing
Chain link fencing will be used to limit access to the Holbrook Tributary. Fencing
already exists at the following locations (see Figure 3-12):
• Along the southern bank of Holbrook Tributary between Sharp Drive and South
Dougherty Avenue.
• Both sides of Holbrook Tributary between Sharp Drive and South Lucas Drive.
• Along the northern bank of Holbrook Tributary between South Lucas Drive and
the railroad culvert.
Existing fences will need to be inspected and repaired to limit access to Holbrook
Tributary.
New fencing will be installed in the following areas:
Enclose the northern side of Holbrook Tributary between Sharp Drive and South
Dougherty Avenue. Construction of new fencing will be necessary between the
intersection of Sharp Drive and the Holbrook Tributary to the southwest corner of
the intersection of Honeycutt Road and South Dougherty Avenue. Fencing will
follow Honeycutt Road so that it can be easily accessed for maintenance (i.e.,
burning) by Fort Bragg.
• Enclose the southern side of the Holbrook Tributary between South Lucas Drive to
the railroad right-of-way.
All fencing materials, dimensions, and construction methods will be in accordance to
Unified Facilities Guidance Specifications (USACE, 2007) and the Fort Bragg
Installation Design Guide. Two gates will be necessary to access surface water treatment
systems and monitoring locations on the Holbrook Tributary. One double -swing gate
will be constructed at or near the intersection of the Holbrook Tributary and Sharp Drive
to access the enclosed area north of Sharp Drive. A second double -swing gate will be
located at the intersection of the Holbrook Tributary and South Lucas Drive to access the.
enclosed. area west of South Lucas Drive. All gates will be locked with padlocks and
keys provided by Fort Bragg.
3.3.4.3 Warning Signs
Signs will be mounted onto the fencing to clearly communicate restrictions to the
Holbrook Tributary. Signs will be placed to optimize exposure to the main vehicular and
pedestrian paths adjacent to fenced areas. Signs will be placed at regular intervals where
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not adjacent to public right of ways. The maximum distance between signs will be 200
feet.
All signs will comply with the Fort Bragg Installation Design Guide for Type A3
Small Metal signs. Each sign will be an 18" by 24" metal panel colored brown with 1/2-
inch white border and white reflective letters. The signs will display "KEEP OUT", "No
Fishing" and "No Wading" in white Helvetica font, and will be mounted on metal "U-
channel" posts attached to the fence.
3.3.4.4 Site Restoration ..
After fence construction activities are complete, any areas that were disturbed by these
activities will be returned to their pre -mobilization state. It is expected that site
restoration activities will be limited to filling in ruts and planting grass seed. Major
disturbances are not expected because off -road vehicle usage will be limited to a pickup
truck and potentially a small tracked vehicle (e.g., Bobcat) for fence construction.
3.3.4.5 Final Site Survey
The location of fencing will be surveyed after all activities are complete. All location
data will be presented in the CMIR.
3.4 PERFORMANCE MONITORING
3.4.1 Groundwater Monitoring Well Network, Frequency, and Parameters
Theinitial groundwater monitoring network will consist of 30 wells (Table 32 and
Figure 342). The monitoring well network will be evaluated annually for optimization
opportunities. The monitoring network focuses on the deeper wells (and eliminates some
shallow wells) from the existing network because contamination' is primarily in the
deeper wells.
Groundwater near the source area will be sampled quarterly during the first year
following carbon substrate injection to evaluate the performance of anaerobic_ reductive
dechlorination. Should additional injections be 'necessary, quarterly performance
monitoring will be conducted as with the initial injection. Thereafter, performance
monitoring will be conducted' annually or biennially based on periodic evaluation of
results. The current, naturally occurring geochemical conditions at SWMU '103 are
aerobic. Thus, it is expected that it will take at least six months for the injected substrate
to establish anaerobic conditions necessary for biotic reductive dechlorination to occur.
After anaerobic conditions are established it typically takes at least 6 to 12 additional
months to establish the proper -microbial population .necessary for biotic reductive
dechlorination.
During the first year following substrate injection groundwater from wells in the
vicinity of the carbon substrate injection. areas will be sampled and analyzed for VOCs,
total organic carbon (TOC), geochemical parameters and pH. In addition, several of the
temporary injection wells will also be sampled to monitor geochemical and contaminant
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conditions within the injection areas. Results of the groundwater sampling will be used
to evaluate the effectiveness of the enhanced anaerobic bioremediation application.
Performance groundwater monitoring for MNA would occur on an annual or biennial
basis to evaluate the progress of the natural attenuation. The location and sampling
frequency of wells for performance sampling will be selected based on evaluation of the
results of the previous year's performance sampling. Groundwater will be analyzed for
VOCs and natural attenuation parameters.
Groundwater sampling activities will be conducted in accordance with the final project
sampling and analysis plan/quality assurance program -plan (SAP/QAPP).
3.4.2 Soil Gas Monitoring
Crawlspace air and soil gas sampling has determined that VOCs are not currently
impacting indoor air quality at Holbrook Elementary School. To ensure that the school is
not impacted by vapor intrusion in the future, soil gas monitoring will be conducted at
existing representative monitoring points. A total of 18 soil gas monitoring points
surround the perimeter of the Holbrook Elementary School buildings and within open
areas between separate school buildings (Figure 3-13). Soil gas sampling will be
conducted from all 18 sampling points for one more year. Soil vapor samples will be
collected in accordance with EPA Method TO-15 and analyzed for VOCs. If the 2006
soil gas sampling results are confirmed, and groundwater VOC concentrations do not
increase, the sampling network will be optimized. Optimized sample locations and
frequency will be determined based on evaluation of sample results. One possible
optimized network includes monitoring points SG1, SG14, and SG16. If the new
sampling results do not confirm the 2006 results, additional gas samples will be collected
annually prior to the beginning of the school year., The results of the soil gas sampling
will be evaluated relative to EPA vapor intrusion screening criteria to ensure that
Holbrook Elementary School remains safe from vapor intrusion.
3.4.3 -Surface Water Monitoring Locations, Frequency and Parameters
Seven surface water performance monitoring locations will be established on
Holbrook Tributary and Beaver Creek (Figure 3-12). Surface water at these locations
will be sampled quarterly for at least one year after construction of passive aeration
structures. The locations are:
i
• S-1: Located at Station 9+10, where Beaver Creek flows under Knox Street. This
location is the compliance point for surface water treatment.
• S-2: Located at Station 17+29, where Holbrook Tributary exits the culvert under
the railroad. Samples from this location will evaluate the performance of
treatment systems in the culvert and in the lower portions of Holbrook Tributary
(below South Lucas Drive).
• 53:, Located at Station 23+48, where Holbrook Tributary exits the culvert under
South Lucas Drive. Samples from this location will evaluate the performance of
treatment systems just above South Lucas Drive.
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• S4: Located at Station 29+52. This location has historically had the highest
measured concentration of 1,1,2,2-TeCA in Holbrook Tributary surface water.
Samples from this location will evaluate the performance of treatment systems
near Sharp Drive.
• S5: Located at Station 35+00, on Holbrook Tributary upstream of Sharp Drive.
Samples from this location will track contaminant levels in surface water
upgradient of the first passive treatment area.
• S6: Located at Station 16+80, on Beaver Creek about 50 feet upstream of
confluence with Holbrook Tributary. Samples from this location will evaluate
contaminant levels in surface water released from Beaver Pond and groundwater
discharge.
• S7: Located at Station 23+20 on Beaver Creek at the outfall of Beaver" Pond.
Samples from this location will evaluate contaminant levels in surface water
released from Beaver Pond.
Monitoring of surface water will be required to assess contaminant concentrations, and.
'ensure the protection of human health and the environment. Surface water sampling will
be conducted during low flow conditions (worst case) at fixed locations. Samples will be
collected after five (and preferably ten) days of no precipitation. Repeated sampling at
fixed locations will allow thorough evaluation of the performance of an implemented
-� corrective action across the seasons, and'more control over observations. Surface water
sampling activities will be conducted in accordance with the final project SAP/QAPP.
3.4.4 Performance Evaluations
The performance of the enhanced bioremediation application at SWMU 103 initially
will be evaluated annually. If the long term monitoring program sampling frequency is
reduced to less than annual, performance evaluations will be conducted on the same
frequency as the sampling schedule.
The performance evaluation at SWMU 103 will start with an assessment of
contaminant concentrations over time. Contaminant concentration trends are the primary
line of evidence for determining the effectiveness of the SWMU 103 application. If
contaminant concentrations in groundwater decrease over time, the SWMU 103
corrective actions application can be considered to be successful.
The. second .step in evaluating the effectiveness of an enhanced bioremediation
application is to evaluate the concentrations of parent compounds (1,1,2,2-TeCA and
TCE) and reductive dechlorination daughter products (cis-1,2-dichloroethene. [cis-1,2-
DCE], vinyl chloride (VC), and ethene). If biotic reductive dechlorination is occurring,
then the concentration and molar fraction of the parent compound will decrease while the
concentrations and molar fractions of daughter products will increase. The presence and
relative molar fractions of the individual daughter products will indicate whether partial
or complete reductive dechlorination is occurring. During the first year after substrate
injection it is expected that at least partial reductive dechlorination of 1,1,2,2-TeCA and
- TCE to cis-1,2-13CE will occur. However, more complete reductive dechlorination to
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VC and ethene may not occur until up to 2 years after injection. The demonstration of
partial reductive dechlorination, coupled with reduced 1,1,2,2-TeCA and TCE
concentrations during year one will be interpreted to indicate that the SWMU 103
enhanced bioremediation application successfully induced reductive dechlorination.
It should be noted that VC is extremely unstable under aerobic geochemical conditions
(the natural geochemical conditions at SWMU 103) because VC is readily degraded
through aerobic oxidation. Thus, while VC may be produced in the injection areas
through biotic reductive dechlorination, the VC mass will be rapidly oxidized once it
migrates outside of the anaerobic zone established around the injection area.
The third step in evaluating an enhanced bioremediation application involves the
evaluation of the geochemical data to determine what geochemical conditions are present
at the site and whether sufficient organic substrate remains to support the anaerobic
geochemical conditions necessary for biotic reductive dechlorination. TOC
concentrations are evaluated to determine if sufficient organic carbon remains. TOC
concentrations greater than 20 milligrams per liter (mg/L) have been interpreted by the
United States Environmental Protection Agency to be necessary to support anaerobic
geochemical conditions and reductive dechlorination (USEPA, 1998). In addition, DO,
oxidation-reduction potential (ORP), nitrate/nitrite, ferrous iron, methane, and manganese
data will be reviewed to determine what terminal electron accepting processes (TEAPs)
are actually occurring at SWMU 103. This data will help to determine how much of the
organic substrate is being used to process other than reductive dechlorination and will
lead to a determination of how long the substrate will actually last in the subsurface.
The final step in evaluating the enhanced bioremediation at SWMU 103 will be to
review the pH data. Biotic reductive dechlorination has been shown to occur most
rapidly under pH neutral conditions (6.5 to 7.5). In addition, biotic reductive
dechlorination does not occur at acid conditions (pH less than 6.0) due to the pH
sensitivity of the microorganisms involved in the reductive dechlorination process
(Volkering and Pijls, 2004). If pH conditions become more acidic than pH 6.0 during the
course of this application (due to the depletion of natural and added buffering capacity)
then complete reductive dechlorination may slow down until the buffering capacity is
replaced.
Surface water treatment will be evaluated through periodic monitoring at the surface
water monitoring sites. Consistent monitoring locations are key to evaluating treatment
performance. Since contaminant migration may be influenced by seasonal variations,
surface water will be monitored for a year to evaluate the performance of each step in the
surface water treatment strategy.
The following conditions will indicate a successful remedy:
• The TOC concentration in each injection area (as indicated by data collected from
the temporary injection wells) is greater than 20 mg/L.
• Declining 1,1,2,2-TeCA concentration trends and increasing daughter product
concentrations in the injection area monitoring wells (e.g., MW-23, MW-48, MW-
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49, MW-50). Trends in these wells will have to be established some time after the
injection event(s) to allow dilution water to migrate away from the source area.
Convergence toward North Carolina surface water standard of 4µg/L for 1,1,2,2-
TeCA at Knox Street, as well as trends from other surface water sampling
locations indicating 1,1,2,2-TeCA volatilization.
3.4.5 Performance Monitoring Program Optimization
The SWMU 103 performance monitoring program will be evaluated annually to
determine if the program can ' be optimized such that only data that ,are of value and
directly contribute to future decisions are. collected. Any proposed changes to the
monitoring program will be discussed and approved by the Army and NCDENR prior to
implementation.
3.5 CONTINGENCY PLANNING
Two potential contingencies are planned for possible deployment at SWMU 103. In
the event that the analytical data (VOCs' and geochemistry) indicate that anaerobic
geochemical conditions appropriate for biotic reductive dechlorination have been
established but that biotic reductive dechlorination 'is not .occurring, then a
bioaugmentation culture maybe injected into the SWMU 103 injection area in an effort
to emplace -a microbial population known to be capable of reductive dechlorination,
�1 thereby inducing reductive dechlorination. This contingency will be deployed if all of the
following conditions are met:
• DO is consistently less than I mg/L over multiple sampling rounds. The
bioaugmentation culture can only survive in an anaerobic' environment.
• ORP is less than -100 millivolts (mV) (indicative of moderately to strongly
reducing conditions) over multiple sampling rounds. The bioaugmentation culture
can only survive in an anaerobic (reducing) environment.
• TOC concentration is above 50 mg/L in the area being considered for
bioaugmentation. Because the bioaugmentation culture can only survive in an
anaerobic environment, there needs to be enough carbon present to maintain
anaerobic conditions.
• 1,1,2,2-TeCA concentration trends increase or remain stable over multiple
sampling rounds beyond the first year of long term monitoring. If 1,1,2,2-TeCA
concentrations do not decrease although geochemical conditions are favorable for
reductive dechlorination, bioaugmentation may be able to initiate the process.
• Daughter products (cis-1,2-DCE and/or VC and/or ethene) are not detected. The
lack of daughter products is an indication that reductive dechlorination is not
occurring even though conditions are favorable.
The second contingency relates to the early depletion'of the injected organic substrate.
If geochemical data indicates that the organic substrate emplaced during the first injection
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is becoming depleted before contaminant concentrations are reduced in the source area,
then additional organic substrate will be injected into the ' source area to extend the
longevity of the enhanced bioremediation application. Substrate depletion will be
signified by the reduction of TOC concentrations to below 20 mg/L and the return, of
aerobic geochemical conditions in the injection area. If geochemical data indicates that
the substrate is reaching depletion. 1,1,2,2-TeCA concentrations at the source area remain
above 100µg/L, and reductive dechlorination daughter products are not being produced,
then additional organic substrate will be injected.
3.5.1 Bioaugmentation Solution Preparation and Injection
In' the event that bioaugmentation is deemed to be necessary, a bioaugmentation
culture will be purchased from SIREM Laboratories and mobilized to the site in specially
designed pressurized shipping containers. An injection system consisting of a
groundwater extraction pump, a transfer pump, an injection pump, and an inline
dosimeter as well as various valves, pressure gauges, and flow meters will also be
mobilized to the field site.
It is expected that less than one liter of bioaugmentation culture will be required for
each injection well based on Parsons and Sirem Laboratories' prior experience at other
sites. Sirem's general rule of thumb for calculating culture dosage is 1 part culture per
30,000 parts groundwater in the intended treatment area. The treatment volume for each
injection well is approximately 2,098 gallons. Applying a 1:30,000 factor yields a
calculated culture volume of approximately 0.25 liters per injection well. Thus,
approximately 4.5 liters of bioaugmentation culture will be required for the injection area.
Upon arrival, the injection system will be setup at the. source area. A groundwater
extraction pump will be installed in a nearby monitoring well to supply makeup water for
the bioaugmentation injection. The geochemistry of the groundwater to be extracted will
be confirmed to be anaerobic (DO less than 1 mg/L) . prior to mixing with the
bioaugmentation culture. After the groundwater geochemistry has been confirmed. The
groundwater will be extracted, amended inline with culture through a closed system
dosimeter, and re -injected into the previously installed small diameter injection wells.
The bioaugmentation process will begin at each injection well by starting the
extraction pump, pumping water through the entire injection system, and discharging to
the injection well. During this initial phase the system will be bled of all air bubbles and
pockets and all joints and couplings will be inspected for leaks. After the system has
been started the dosimeter will be set to add bioaugmentation culture at a rate of 1 percent
of the water flow. Previously extracted groundwater amended with one percent culture
will continue to be injected until approximately 0.25 liters of culture have been added.
At that point the dosimeter will be shutdown and un-amended groundwater will continue
to be injected to improve the subsurface distribution of bioaugmentation culture.
Ultimately each injection well will receive approximately 0.25 liters of culture and
approximately 250 gallons of water.
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3.5.2 Contingency Substrate Injection
Additional soybean oil and the injection system will be mobilized to the site in the
event that a second substrate injection is deemed to be necessary. The contingency
injection will be conducted in exactly the same way as the primary injection except that
the contingency injection will be conducted through the previously installed small
diameter injection wells only. The scope of the second injection and the substrate
loading to be deployed will depend upon conditions present within the source area.
However, for permitting purposes it is assumed that the contingency injection will be
required and that it will involve the injection of approximately half. of the substrate
volumes injected during the primary injection.
3.6 INSTITUTIONAL CONTROLS
3.6.1 Ground Water
Current administrative controls and groundwater -use restrictions for the SWMU 103
groundwater plume footprint are incorporated in the BMP. SWMU 1.03 is part of a
federal installation and is expected to be retained by the federal . government for the
indefinite future. Existing groundwater -use restrictions currently prevent the use of the
groundwater for potable water and irrigation. References to relevant corrective action
documents for this SWMU are included in the BMP. The groundwater use restrictions
will remain until North Carolina 21, standards are met, or until concentrations are at such
levels to allow for unrestricted use and exposure.
A survey plat for the SWMU has been included in the BMP. The survey plat indicates
the location and dimensions of the SWMU 103 groundwater plume with respect to
permanently surveyed benchmarks. The plat contains a directive that states Fort Bragg's
obligation to prohibit use of the groundwater at SWMU 103 in accordance with this
CMS. The previously surveyed groundwater monitoring wells that establish the present
extent of groundwater contamination originating from SWMU 103 were used to establish
the perimeter of the SWMU 103 groundwater plume.
Institutional controls include the restriction of groundwater use at SWMU 103.
Restrictions on groundwater use for consumption and irrigation will be implemented for
the life of this corrective action alternative, estimated to be 20 to 60 years. The
groundwater -use restrictions will be implemented during the period of ownership by DoD
through the BMP. The BMP is an effective tool for prohibiting installation of drinking
water or irrigation wells at the site while property is under DoD ownership. Groundwater
is not currently used as a source of drinking water or irrigation at the site. Institutional
controls prohibiting the use of groundwater in the future would be effective at protecting
human health from the elevated levels of COCs in the groundwater.
Current land use controls (LUCs) prohibit intrusive activities (e.g., excavation,
digging, drilling) at SWMU 103 without an approved health and safety plan, use of
proper personal protective equipment, and other necessary precautions. If soil is
excavated from within the SWMU 103 plume area, it must be properly characterized,
classified, and disposed of in accordance with Fort Bragg policy and applicable
environmental regulations.
i
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A LUC Boundary for Indoor Air Concerns surrounds the SWMU 103 groundwater
contaminant plume. LUCs for this area place limitations on construction of buildings
within this boundary due to vapor intrusion concerns. If structures must be sited within
this LUC boundary, building design must incorporate appropriate features to mitigate
potential for human exposure to"chlorinated VOCs from groundwater.
3.6.2 Surface Water
Current administrative controls and use restrictions for surface waters affected by SWMU
103 are incorporated into the BMP. The surface water in Beaver Creek and the Holbrook
tributary is not used as a source of potable water, irrigation, and/or recreation primarily
because the flows are too low. The streams are primarily used as a stormwater drainage
conveyance for Fort Bragg. Surface water -use restrictions exist to prevent its use for
drinking water, irrigation, or recreation. Fencing will be constructed at the Holbrook
tributary to restrict contact with the surface water. Warning signs will also be placed at
the Holbrook Tributary to inform persons of the potential contamination .in the surface
water. Current surface water -use restrictions and the addition of fencing and warning
signs will provide an effective, readily implementable, and cost-effective method for
reducing human exposure to surface water at the site. The surface water use restrictions
will remain until North Carolina standards are met, or until concentrations are at such
levels to allow for unrestricted use and exposure.
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SECTION 4
REPORTING AND DOCUMENTATION
4.1 CORRECTIVE MEASURES IMPLEMENTATION REPORT
A CMIR will be issued at the completion of the substrate injection, fencing, and initial
surface water remediation activities at SWMU 103. Since the surface water remedy will
be implemented in several -steps over several years, construction of subsequent steps will
be documented in performance effectiveness reports. The CMIR will present all field
activities completed at- SWMU 103, any field data collected during the installation of the
corrective action, and any deviations from the final SWMU 103 CMIP. The report will
also include information about monitoring wells that are pumped to provide supplemental
groundwater for injection, including which wells are used and groundwater extraction
rates.
j r , 4.2 PERFORMANCE EFFECTIVENESS REPORTS
An annual performance effectiveness report will be issued to present the results of the
sampling events collected during the previous calendar year. If the monitoring frequency
is reduced, the frequency of progress reporting will be reduced as well to coincide with
monitoring events. Performance effectiveness reports will present all data collected
during the subject reporting period, an assessment of contaminant concentration trends at
each performance monitoring well, an assessment of the effectiveness of the corrective
action implemented at SWMU 103, and recommendations for any changes to the
performance monitoring program for the following reporting period.
Recommended elements of the evaluation report for this site.include:
A summary of site activities.
An evaluation of new data and comparisons with previous data and established
performance criteria, which would' consist of presentation of the following:
- Data in tabular format (proposed historical groundwater and surface water
contaminant concentration data format are provided as Tables 1-2 and 1-3,
respectively);
- Graphs (e.g., contaminant concentration versus time for individual wells);
- Figures (contaminant contours); and
L.
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- Progress towards achieving remediation goals.
• An evaluation of need for implementation of additional corrective action phases
and/or contingency plan.
• Conclusions.
• Recommendations.
4.3 PERIODIC REMEDY REVIEWS
This site is managed by the Army under the Department of Defense (DoD) Defense
Environmental Restoration Program (DERP). Paragraph 23.2 of the DoD DERP
guidance specifies that periodic remedy reviews be conducted at least every five years to
ensure that the selected remedy continues to protect human, health and the environment.
Thus, the corrective action at SWMU 103 will be reviewed at least every five years. The
first review will be conducted within .approximately five years of the selected remedy
installation (estimated to be during the spring of 2013).
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TABLES

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Table 1-1
Recommended Remedial Levels for COCs in Groundwater and Surface Water at SWMU 103
Analyte
Maximum
Concentration
Recommended
Remedial Level
Groundwater
Volatile Organic Compounds ( )
Chloroform
82
70
Chloromethane
6.9
2.6
1,1,2,2-Tetrachloroethane
660
0.17
Tetrachloroethene
3.2
0.7
Trichloroethene
78
2.8
Surface Water
Volatile Organic Com ounds ( )
1 1,2,2-Tetrachloroethane
59.6
4
COC = Constituent of concern.
SWMU = Solid waste management unit.

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cr)
Kil

Table 1-2: Historic Detections of Contaminants in Groundwater at 9WMU 103
1,1,2,2-Tqft=hIoroedww
0.17
n/a
470
63
29 J
100
Trichtoroethene
2.8
5
66
10
14 J
ND (50)
Tetrachloroeltme
0.7
5
2.6
0.5 1
ND (1)
ND (50)
Chloroform
70
100
1.1
ND (1)
ND (1)
82
Chloromethane
2.6
n/a
ND (1)
ND (3.5)
ND (1)
ND (50)
T c
5
5
ND (1)
ND (1)
ND (1)
ND (50)
_D
-Dichloroethene
c
1 i hh
ff1,1,2-Trichloroethane
100
70
ND (1)
ND 2)
ND (50)
cis- 1,2-Dichloiroethene
cis
70
70
ND (1)
ND (1)
trans-1,2-Dichlomethene
100
too
ND (1)
ND (1)
1,1-Dichloroethene.
7
-7
ND (1)
ND (1)
ND (I
ND (50)
Vinyl Chloride
0.015
2
ND (1)
ND (2)
ND 1
ND (50)
Methylene Chloride
4.6
5.
ND (1)
ND (2)
ND (1)
ND (50)
2 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
1,1,2,2-Tetrachloroethane
0.17
n/a
434
660
420
340
Trichloroethene
2.8
5
46
69
22
50
Tetmehloroethene
0.7 —
5
1.6
2.3
ND 5)
ND 10)
Chloroform
70
100
1.1
1.2
5.5
17
Chloromethane
2.6
n/a
ND 2.9)
ND 1)
ND 5)
ND (10)
IF : 1"' ,!� ,v,u_
1 1,2-Trichloroethane
5
5
0.4 J
ND 1)
ND 5)
ND 10)
1 2-Dichloradhene
100
70
ND 2
ND 5
ND 10)
is-1,2-Dichlomethene
70
70
0.2 J
ND 1
trans-1,2-Dichloroethene
100
100
ND 1)
ND 1)
1,1-Dichloroethene
7
7
ND (1)
ND 1)
ND 5
ND 10)
Vin 1 Chloride
0.015
2
ND (2
ND 1
ND 5)
ND (10)
Meth lone Chloride
4.6
5
ND (2)
ND 1)
ND 5) 1
ND (10)
3 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
1,1 ,2-Tetmhloroethane
0.17
n/a
270
470
450
43
Trichloroethene
2.8
5
49
66
68
10
etrachkMxdWne
0.7
5
1.4 J
2.2
2.3
0.3 J
hlomfonn
70
100
0.96 J .
1.9
1.7
ND 1)
Chlommethane
2.6
n/a
ND (2)
ND 1)
ND 1)
5.2
hlomethane -
5
5
0.73 J
ND 1)
ND 1)
2.1
oroethene
100
70
ND 2
0.48 J
0.47 J
ichlomedm=
70
70
ND 2
0.4 J
Dichleroethene
p
100
too
ND (2)
0.4 J
omedw=
7
7
ND 2
ND 1
ND l
ND 1oride
0.015
2
ND 2
ND 1
ND 1
ND 2)
e Chloride
4.6
5
ND (2)
ND 1)
ND 1)
ND (2
4 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
W* Laeatlon
N.C.
Groundwater
Standard 21,
Federal
MCL
In Plume
In Plume
In Plume
In Plume
Station
MW-03
MW-03
MW-05
MW-05
sample ID
4203112
320311
420511
4205112
Date
5/7/2001
1/14/2003
7/18/2000
5/2/2001
De h of Seeened Interval )
5 to 15 ft
5 to 15 ft
15 to 25 ft
15 to 25 ft
1,1,-Tetrachloroethane
017
n/a
33
22
143
179
Trichloroethene
2.8
5
7.8
6.9
21
22
Tetrachioroethene
0.7
5
0.2 J
ND 1
0.8 J
i J
roform
70
100
ND 1
ND 1
0.6 J
0.9 J
Chloromethane
2.6
n/a
2.9
ND 1)
ND 1)
ND 6.8)
5
5
4
ND 1
ND 1
0.2 J
roethene
100
70
ND 2chtoroedme
70
70
0.4 J
ND 1
ND 1
ND iiehloroethene
Khloroethane
100
100
0.2 J
ND 1
ND !
ND (1)
roethene
7
7
ND 1
ND 1
ND 1
NDt
oride
0.015
2
ND (2
ND 1
ND 2
ND
Chloride
4-6
5
ND (2
ND 1)
ND 2)
ND
5 of 33

This page intentionally left blank

J__
------
21
Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
oc>iti0a
N.C.
Groundwater
Standard 2L
Federal
MCL
In Plume
In Plume
In Plume
In Plume
MW-05
MW-05
MW-09
MW-09
eiD
420521
320511
420911
4209112
5/2/2001
1/12/2003
7/18/2000
5/3/2001
of Sceened Interval
15 to 25 ft
15 to 25 ft
48 to 50 ft
48 to 50 ft
M�Yr1Nfe:i%��i�AhlYaYl�'�i/lA��i�1 ..:.: r-..
���...+... iFe ....'.:s...
+. :.. <'.:. .r.-:_.. �c:..
... a ... .. r...
..F:y _ �t. .. _.e
n ... �... �. ..r. ... .- •
- .... ...... ,.. -
Tetracblomedum
0.17
n/a
166
220
34
23
2.8
5
22
26
3.6
2.5
pChloromethane
0.7
5
1.4
1.1
0.2 J
ND 1olm
70
100
0.9 J
0.7 J
0.7 J
0.9
2.6
n/a
ND (2.5)
ND 1)
ND 2.2)
3.6
1,1 2-Trichloroethane
5
5
ND 1)
ND 1
ND 1
ND 1
1,2-Dichloroethene
100
70
ND 2)
cis-1,2-Dichlowethene
70
70
ND 1
ND 1
ND 1
ND 1
trans-1 2-Dichioroethene
100
100
ND 1)
ND 1)
ND 1)
ND (1)
1,1-Dichlowethene
7
7
ND 1
ND 1
ND 1
ND 1
Vin 1 Chloride
0.015
2
ND 2
ND 1
(2)
ND 2
Meth ene Chloride
4.6
5
ND 2)
ND 1F77M(2)
ND (2
6 of 33

Table 1-2:-Historic Detections of Contaminants in Groundwater at SWMU 103
1,1,?:a-TCft=hIOrOedU=
0.17
n/a
290
86
110
409
Trkhtomethene
2.8
5
15
22
14
50
Tebwhkwpe&=
0.7
5
0.53 J
0.6 J
ND (1)
3.2
ChImoform
70
100
0.74 J
2.4
0.65 J
1.2
Chloronwthaw
2.6
n/a
ND (0.96)
ND (1)
ND (1)
ND 1.1)
1,1,2-Tfichloroethahe
5
5
ND (0.49)
ND (1)
ND (1)
0.3 J
1,2-Dichlomethene
too
70
ND (0.63)
ND (2
cis- 1,2-Dichtoroethem
70
70
ND (0.36)
ND (1)
ND (1)
ND (1)
-1,2-Dichloroethene
IMethylene
100
100
ND (0.27)
ND (1)
ND (1)
ND (1)
IJ-DiMproodme
7
7
ND (0. 11)
ND (1)
ND (1)
ND (1)
Vinyl Chloride
0.015
2
ND (0.26)
ND (2)
ND 1)
E
ND (2)
Chloride
4.6
5
ND 0.21)
ND (2)
ND (1)
ND (2)
7 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
1WdI Location
In Plume
In Plume
in plume
In Plume
lion
0
MW-12
MW-12
MW-12
MW-15
mple, ID
N.C.
321211
321221
321216
421511
Date
ltmh4
Groundwater Federal
1/13/2003
1/13/2003
6/28/2006
5/2/2001
epth of Sceened Interval (bgs)
Standard 2L MCL
43.8 to 53.8 ft
43.8 to 53.8 ft
418 to 53.8 ft
29.6 to 39.6 ft
r �0,=,M
1,1,2,2-Tetrachlomedum
0.17
n/a
510
800
260
91
Trichlozoethene
2.8
S
41
56
40
9.7
Tetrachloveetimme
0.7
5
2.7
2.5
2.1
0.5 J
Chloroform
70
100
0.911
0.96 J
0.83 J
0.7 J
C"Itoromethane
2.6
n/a
ND (1)
ND (1)
ND (2)
ND (1.4)
5
5
ND (1)
ND (1)
ND (2)
ND (1)
1,2-Dichkwoethene
100
70
ND (2)
ND (2)
ND (2)
is-1,2-Dichloroethene
70
70
ND (1)
ND (1)
ND (2)
ND (1)
I1,1,2-TrieWWoefliane
trans-1,2-13ichlomethene
100
100
ND (1)
ND (1)
ND (2)
ND (1)
I,I-Dichloroethene
7
7
ND (1)
ND (1)
NDf(2)
ND (1)
inyl Chloride
0.015
2
ND (1)
ND (1)
ND (2)
ND (2)
Meth Chloride
4.6
5
ND (1)
ND (1)
ND 2)
ND (2)
8 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
1,1,2,2-Tetrachioroedww
017
n/a
95
125
160
121
richloroedv=
2.8
5
12
14
20
14
etsachloroedme
0.7
5
ND 1
0.7 J
0.77 J
0.7 J
hMmOform
70 .
100
0.62 J
0.5 J
i 0.58 J
11
hlowrnedww
2.6
n/a
ND 1)
ND 1)
ND 1
ND (1
�M/[IIIXPM %� � I/%i4" /IP. ,. _.� ._.F.�. _, d iA. r.4T �., 5..._�J.i:.... t!cZ ::. ..K.._.Y3 ,. .4-...i.. _.. _F. ..'.:... ..' .n,. ... �_N.�,':r. -,1... .ix.:�>.,'_J ait -•
1 1,2-Trichlowethane
5
5
ND l
1.7
ND 1
1.8
1-Dichioroethene
100
70
ND 2 1
ND 2)
cis-1,2-DichWwedw3w
70
70
ND 1
ND 1)
ND 1
ND 1
Baas-l2-Dichlomcthene
100
100
ND(1)
ND 1)
ND 1)
ND(1
1 1-Dichh wethene
7
7
ND (1)
ND 1)
ND 1)
ND 1
Yin Chloride
0.015
2
ND 1-
ND 2
ND 1
ND 2
methylene Chloride
4.6
5
ND (1)
ND 2)
ND 1)
ND (2)
9 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
1,1,2,2-Tet=hIoroedume
0.17
n/a
200
140
150
71
Trichtwoethene
2.8
5.
28
17
16
8.6
Tetmchkwmflime
0.7
5
1
0.78 J
0.76 J
0.3 J
Chlorofoim
70
100
11
ND (1)
ND (1)
0.2 J
Chloremedww
2.6
n/a
ND (1)
ND (1)
ND (1)
ND (2)
5
5
ND (1)
ND (1)
ND (1)
ND (1)
1,2-Dichtoroethene
100
70
ND (2)
0.6 J
ND (2)
is-1,2-Dichtoreethene
70
70
ND (1)
0.58 1
0.68 J
ND (1)
I1,1,2-Trichlorpediane
trans- 1,2-Dichloroethene
100
100
ND (1)
ND (1)
ND (1)
ND (1)
I,[-Dichloroethene
7
7
i ND (1)
ND (1)
ND (1)
ND (1)
Vinyl Mad&
0.015
2
1
ND (1)
ND (1)
U-ND (1)
ND (2)
Meth lene Chloride
4.6
5
ND (1)
ND (1)
1 ND (t)
ND (2)
10 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Statioa
MW-02
MW-02
MW-17
MW-17
Sa!! ID
N.C.
4202112
320211
421711
321711-
Date
Groundwater
Federal
5/7/2001
9/12/2003
5/3/2001
1/14/2003
Depth of Sceened luterval s
Standard 21,
MCL
26.5 to 35.5 ft
26.5 to 35.5 ft
9.1 to 19.1 ft
9.1 to 19.1 ft
Oprila inants,ofCorrcern'(u21
13,2,2-Tetrachloroethane
0.17
n/a
115
62
ND 1)
1.9
Trichloroethene
2.8
5
14
10
ND 1
ND 1
Tehachloroethene
0.7
5
0.7 J
ND 1)
ND 1
ND 1
Chloroform
70
100
0.7 J
ND 1)
0.6 J
ND l
hioromethane
2.6
n/a
3.3
ND 1
ND 1)
ND (1
112-Trichloroethane
5
5
ND 1
ND 1
ND 1)
ND 1
1 2-Dichloroediene
100
70
ND 2
ND 2
cis-1,2-Dichloroethene
70
70
ND 1
ND 1
ND !
ND 1)
tmas-1,2-Diehloroethene
too
100 _
ND 1)
ND 1)
ND 1)
ND (1
1,1-Dichloroethene
7
7
ND (1)
ND 1)
ND 1
ND 1
thin 1 Chloride
0.015
2
ND 2
ND 1
ND 2
ND 1
ethylene Chloride
4.6
5
ND (2)
ND 1)
ND 2) .
ND (1)
11 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Station
N.C.
Groundwater
Standard 2L
Federal
MCL
MW-20
MW-20
MW-26
I MW-26
!!E&ID
422011
322011,
322611
322621
Date
5/8/2001
1/14/2003
3/28/2002
3/28/2002.
LIeptk of Sceened Interval (bp)
20.45 to 30.45 ft
20.45 to 30.45 ft
34.0 to 44.0 ft
34.0 to 44.0 ft
n- /a
7
5.9
ND (1)
91
Trichloroethene
2.8
5
0.7 J
0.92 J
1.3
1.4
rChlo1,1,2,2-Teowhlrco-r,oedu'm""—
Wh
0.7
5
ND (1)
ND (1)
ND (1)
ND (1)
tomfoun,
h h im
70
100
1.2
2.2
1.8
1.8
roniedum
JOIX
2.6
n/a
ND (2.9)
ND (1)
ND (1)
ND (1)
5
5
ND (1)
ND (1).
ND (1)
ND (1)
I 1,2-Dichloroethene
100
70
ND (2)
C cis-1,2-Dichkwoedme
i
70
70
ND (1)
ND (1)
ND (1)
ND (1)
IN1,1,24fichlomedum
am-i,2-Dichloroethene
trans-!
too
100
ND (1)
ND (1)
ND (1)
ND (1)
,I-DichWmthene
Iethylene
7
7
ND (1)
ND (1)
D
ND (1)
i Chloride
0.015
2
ND (2
ND (1) - J-EfND
(1)
ND (1)
Chloride
4.6
5
ND (2)
ND (1)
. 2.9'
2.5
12 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Station
N.C.
Groundwater
Standard 21,
Federal
MCL
MW-26
MW-26
MW-28.
MW-28
ID
32AAI 1
322612
322811
322812
Date
1/14/2003
4/14/2005
3/29/2002
9/9/2003
Depth of Seemed Interval
34.0 to 44.0 ft
34.0 to 44.0 ft
28.0 to 38.0 ft
28-0 to 38.0 ft
13,2,2-Teftachloroeflune
0.17
n/a
5.6
5.1
2.6
2.2 J
Trichkmxthene
2.8
5
0.811
0.6 J
ND (1)
ND (0.27 J)
FChIplorm
0.7
5
ND (1)
ND (1)
ND (1)
ND (0.22 J)
70
100
2.6
2.3
ND (1)
ND (0.24 J)
foronwdiane
10 M
2.6
n/a
ND (1)
ND (1)
ND (1)
ND (0.96 J)
1,1,,2-Trichloroethane
5
5
ND (1)
ND (1)
ND (1)
ND (0.49 J)
1,24)ichloroethene
100
70
ND (2)
ND (1)
ND (0.63)
-1,2-Dichloroediene
s S_l
70
70
ND (1)
ND (1)
ND (0.36 J)
trans-1)ichloroedvew
100
100
ND (1)
ND (1)
ND (0.27 J)
I 1,1_1
,I-Dichlowediene
7
7
ND (1)
ND (1)
ND (1)
ND (0. 11 J)
Vinyl Chloride
Vj
0.015
2
ND (1)
ND (1)
ND (1)
ND (0.26 J)
Methylene Chloride
M!
4.6
1 5
ND (1)
ND (1)
1 ND (4)
1 ND(O.21_J)__
13oI33

1
Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
jpa
MW-31
MW-31
MW-33
MW-33
Ip
N.C.
323111
—323112
323311
32BB11
pats
GroundwaterFederal
3/29/2002
9/10/2003
3/29/2002
1/l4/2003
De th of Sceened Interval b )
Standard 2L
MCL
19.0 to 29.0 ft
19.0 to 29.0 ft
11.0 to 21.0 ft
11.0 to 2.1.0 ft
,2-TetrachkWOefl=e
0.17
n/a
ND 1)
ND 0.59)
ND 1)
5.2
hhueethene
2.8
5
ND 1
ND .27
ND 1)
ND (1)
hloroedwne
f
0.7
5
ND 1
ND 0.22)
ND 1)
ND 1)
mform
70
l00
3.1
2.3
1
1
romethane
2.6
n/a
ND (1)
ND 0.96)
ND 1)
ND (1)
,2-Trichloroethane
5
5
ND 1
ND 0.49.
ND 1)
ND 1
-Dichioroethene
100
70
ND 0.63
ND 2
-1,2-Dichloroedw=
70
70
ND 1
ND 0.36)
ND 1
ND 1)
ns-1 2-Dichloroethene
IN1,11nethylene
100
100
ND 1)
ND 0.27) .
ND 1)
ND 1
-Dichloroethene
7
7
ND (1
ND 0.11
ND 1)
1 Chloride
0.015
2
ND 1
ND 0.26)
ND 1
±NNDt(l)j
Chloride
4.6
5
1.9 J
ND 0.52)
2.8
14 of 33

f.
Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Station
4MWSI
4MWSI
4MWSI
4MWSI
Sam* ID
N.C.
4MWSI-GWI
4MWSI-GW2
420011
423111
Daft
Groundwater
Federal
2/24/1993
3/4/1997
1
7/21/2000
5/7/2001
2epth of Sceened Interval (bas)
Standard 2L
MCL
20.5 to 30.5 ft
20.5 to 30.5 ft
20.5 to 30.5 ft
20.5 to 30.5 ft
1,1,2,2-Teftwhioroethane
11,2
0.17
n/a
31
20
22
25
Trichloreedu=
2.8
5
5
3
4.3
2.8
e h1oreedwn
0.7
5
5
1
ND (1)
ND (1)
r0form
70
100
5
0.57
0.5 1
0.6 J
hIoromethane
2.6
n/a
14
1
3.6
ND (2.8)
1,1,2-Trichloroethane
5
5
S
1
ND (1)
ND (1)
1,2-Dichkmethene
100
70
cis- 1,2-Dichloroethene
70
70
ND (1)
ND (1)
trans-1,2-Dichloroediene
too
too
5
ND (1)
ND (1)
IJ-Dichloroethene
7
7
ND (1)
ND (1)
ND I
ND (1 )
inyl Chloride
I
0.015
2
11 ::E:
- 1
ND (2)
±�
1
ND (2)
Methylene Chloride
4.6
5
1
ND (2)
(
ND (2)
15 of 33

t
'
�
� J
Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
sv,.fa i ..�ai..� ilxir,a�+fnr EInlf,r�vil-1'rlinni Hnflasrv�lr Srivenl -
tiow
4MWS1 I
MW-35
MW-35
MW-35
saawle ID
N.C.
320411
323511
323512
323513
Data
Groundwater
Federal
1/14/2003
1/12/2003
9/13/2003
4/14/2005
De tb of Sceened Interval b
Standard 2L
MCL
-20.5 to 30.5 ft
6 to 16 ft
6 to 16 ft
6 to 16 ft
Vantaminawft
I1,2,2-Tetraehloroethane
0.17
n/a
22
17_
25
22
riehlemethene
2.8
5
4.7
2.3
3
2.2
Tetrachloroethene
0.7
5
ND 1)
ND 1
ND 1)
ND 1)
lowform
70
100
0.57 J
ND l
0.67 J
0.59 J
Chloroomethane
2.6
n/a
ND (1)
ND 1)
ND 1)
ND 1)
1,2-Trichioroethane
5
5
ND
1
ND
1)
ND
1)
ND
1)
2-Dichlomethene
100
70
ND 2
ND 2
ND 2
ND
1)
s-! 2-Dichlomethene
70
70,
ND
1
ND
1
ND
1
ans-1,2-Dichloroedwne
IMI
100
100
ND
1)
ND
1
ND
1)
1-Dichloroethene
7
7
ND
1
ND
1)
ND
1
ND
1)
in Chloride
&015
2
ND
1
ND
1
ND
1
ND
1)
eth Methylene Chloride
4.6
5
ND
1)
ND
1)
ND
1)
ND
1)
16 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
'"'no
MW-35
MW-35
MW-35
MW-36
Sample ID
N.C.
323514
323515
323521
323611
pate
Groundwater
Federal
8/4/2005
6/27/2006
6/27/2006
1/12/2003
Depth of Sceened Interval h s)
Standard 2L
MCL
6 to 16 ft
6 to 16 ft
6 to 16 ft
17.0 to 27.0 ft
t'is»tiiwinn»lc.infl'�arom litaflsl .. .._ .,;.:;.. .. �F . ,>,, .. ..:;:. s 1
. ,.
1,1,2,2-Tetrachloroedume
0.17
n/a
is
2.9
3
34
Trichloruethene
2.8
5
1.4
0.59 J
0.62 J
4.4
ctmehloroethme
0.7
5
ND 1
ND 1
ND 1
ND (1
toroform
70
100
0.35 J
ND 1
ND 1
0.84 J
Chloromethane
2.6
n/a
ND 1)
ND (1)
ND (1)
ND 1)
�Ibi�iohfni• 1?rnr/�urte.'Y�toLfJ'..... .
1;2-Trichloroedme
5
5
ND 1)
ND 1)
ND (1)
ND 1
2-Dichloroethene
100
70
1 R
ND 1
ND (1)
ND 2
s-1,2-Dichloroethene
70
70
ND 1)
ND 1
ND (1),
trans-1,2-Dichloroedwne
Ivul,
100
100
ND 1)
ND 1
ND (1)
I-Dichloroethene.
7
7
ND 1
1)
ND (1)
ND (1)
ia 1 Chloride
0.015
2
ND 1)
tND
LE1
ND (1ND
1)
eth lens Chloride
4.6
5
ND 1)
1)
ND (1)
ND (1)
17 of 33
j

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Statiwr
MW-36
MW-36
MW-37
MW-37
Sample ID
N.C.
323612
323613
323711
323712
Date
Groundwater
Federal
9/13/2003
4/14/2005
1/12/2003
9/13/2003
Depth of Sceened Interval b s)
Standard 2L
MCL
17.0 to 27.0 ft
17.0 to 27.0 ft
6 to 16 ft
6 to 16 ft
1,1,2,2-Tetrachbroethane
0.17
n/a
29
28
ND (1)
0.71 J
Triehioroethene
2.8
5
3.7
3.1
ND (1)
ND 1)
Tetrachloraethene
0.7
5
ND 1)
ND 1)
ND 1
ND (1)
Chlomfonn
70
100
0.76 J
0.76 J
ND 1
ND 1
Chlommethane
2.6
n/a -
ND 1)
ND (1)
ND (1)
ND (1)
1,1,24tichlomethane
5
5
ND(1)
ND 1)
ND (1)
ND 1)
1-Dichloroethene
100
70
ND 2
ND 1
ND (2)
ND 2
is-1 2-Diehioroethene
70
70
ND 1)
ND 1
ND (1
hens-1,2-Dichloroethene
100
100
ND 1)
ND (1
ND 1
1,1-Dichloroethene
7
7
ND 1)
ND 1)
ND 1)
ND (1)
Vinyl Chloride
0.015
2
ND 1)
ND 1
ND (1)
ND 1)
methylene Chloride
4.6
5
ND 1)
ND (1)
ND (1.1)
0.95 J
18033

This page intentionally left blank

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Station
MW-37
MW-37
MW-37
MW-37
Sample ID
N.C.
323721
323713
323714
323715
Date
Groundwater
Federal
9/13/2003
4/12/2005
8/4/2005
6/27/2006
Depth of Sceened Interval (bgs)
Standard 21,
MCL
6 to 16 ft"
6 to 16 ft
6to16ft
6 to 16 ft
.
1,1,2,2-Tetrachlorpedmw
0.17
n/a
0.72 J
0.98 J
1.3
0.5 1
Tdchloroethene
2.8
5
ND (1)
ND (1)
ND (1)
ND (1)
Tetrachlowedwne
0.7
5
ND (1)
ND (1)
ND (1)
ND (1)
Chloroform
70
100
ND (1)
ND (1)
ND (1)
ND (1)
Chloronwthane
2.6
1 n/a
ND (1)
ND (1)
ND (1)
ND (1)
1,1,2-Michloroethane
5
5
ND (1)
ND (1)
ND (1)
ND (1)
1,2-Dichloroethene
100
70
ND (2)
ND (1)
1 R
ND (1)
is-1,2-Dichloroetimm
C j
70
70
ND (1)
ND (1)
-1,2-Dichloroedow
100
ND (1)
ND (1)
1 'I-DichWWhene ,1
7
7
ND (1)
ND (1)
N
ND (1)
VjVinyl Chloride
0.015
2
ND (1)
ND (1)
ND (1)
EE:::]
ND (1)
Methylene Chloride
M!
4.6
5
1.8
ND (1)
ND (1)
ND (1) -
=1
19 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
well ]LAWAtion
N.C.
Groundwater
Standard 21,
Federal
MCL
Holbrook School
Holbrook School
Holbrook School
Holbrook Sch(x
ate
MW-38
MW-38
MW-38
MW41
SaWle ID
323811
323812
323813
324111
Date
1/12/2003
9/13/2003
4/13/2005
4/12/2005
Dnepth of Sceened Interval (bgs)
17.0 to 27.0 ft
17.0 to 27.0 ft
17.0 to 27.0 ft
34.2 to 44.2 ft
1,1,2,2-Tebachloradhane
0.17
n/a
84
73
77
330
richloroethene
2.8
5
6.9
6.7
5.8
35
Tetrachloroethene
Tcchloroniethane
0.7
5
ND (1)
0.59 J
ND (2)
-1.9
111010form
70
100
ND (1)
ND (1)
1.4 J
1.5
C
2.6
n/a
ND (1)
ND (1)
ND (2)
ND (1)
1,1,2-Tnchloroethane
5
5
ND (1)
ND (1)
ND (2)
2.5
1,2-Dichloroethene
100
70
ND (2)
ND (2)
ND (2)
13
cis4,2-13ichloroethene
70
70
ND (1)
ND (1)
-1,2-Dichloroethene
100
too
ND (1)
ND (1)
IJ-Dichloroethene
7
7
ND (2)
ND (1)
ND (1)
ND (1)
Vi
inyl Chloride
rMethylene
0.015
2
ND (1)
ND (1)
ND (2)
ND (1)
Meth Chloride
4.6
5
ND (1)
ND (1)
ND (2)
ND (1)
20 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Lyon Lm ation
Holbrook School
Holbrook School
Holbrook School
other
Sullen
MW42
MW42
MW42
IW-1
gampLe ID
N.C.
324211
324212
32421.6
350111
Date
Groundwater
Federal
4/14/2005
8/4/2005
6/28/2006
4/14/2005
-Depth of Sceened Interval s)
Standard 2L
MCL
26.7 to 36.7 ft
26.7 to 36.7 ft
26.7 to 36.7 ft
28.7 to 43.7 ft
C'a»►m»iann�cnfl-'nacamaunLFs1 'i ...:... ._ . ,;,'.. �. ,o . ,z .. -:;_ .._ ,, .:•
.;... ;.. _ .: _;. ..
= ....._: .. _
0.17
n/a
3 t0.
210
180
280
richlorocthene
2.8
5
29
18
25
40
etrachiowethene
ITTChloromethane
0.7
5
2
1.7
1.5 J
ND 10)
hloroform
70
100
0.74 J
0.46 J
0.55 J
3.4 J
2.6
n/a
ND 1)
ND 1)
ND (2)
ND 10)
1 1,2-Trichloroethane
5
5
ND 1
ND 1
ND 2
ND 10
1 2-Dichloroethene
100
70
0.54 J
l R
ND (2
ND 10)
cis-1,2-Dichioroethene
70
70
ND 2)
trans-1,2-Dichloroethene
100
100 '
ND 2
1 1-Dichlorocthene
7
7'
ND 2)
ND 1)
ND 10
ND 1)
VinylChloride
0.015
2
ND 1
ND 1
ND 2
ND 10)
Meth lene Chloride
4.6
5
ND 1)
ND (1)
ND (2)
ND (10)
21 of 33.

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Sta"
N.C.
Groundwater
21,
StandardI
Federal
MCL
IW-2
IW-3
sample ID
350211
350311
420111
4201112
Date
4/13/2005
4/13/2005
7/20/2000
1
5/7/2001
Wh of Sceened Interval (bgs)
2e
28.8 to 43.8 ft
29.5 to 44.5 ft
5 to 15 ft
5to15ft.
,
0.17
n/a
570
250
35
18
blomethene
2.8
5
78
34
4.3
1.4
Vl,2,2-TetmchIoroed=w
T Tetrachloroedmw
0.7
5
2.6
1.4
0.2 J
ND (1)
toroform
70
100
1.4
0.91 j
ND (1)
ND (1)
Chl'oronwthane
2.6
n1a
ND (1)
ND (1)
ND (3.2)
3.4
1,1,2-Trichloroethane
2
5
5
ND (1)
ND (1)
0.5 J
ND (1).
1,2-Dichkwoethene
100
70
0.61 J
1.1
LI
cis- 1,2-Dichloroethene
70
70
ND (1)
ND (1)
-1,2-Dichloroethene
100
100
ND (1)
ND (1)
J-Dichloroethene
7
i 7
ND (1)
ND (1)
ND (1)
ND (1)
in Chloride
0.015
1
2
ND (1)
ND (1)
ND (2)
#
ND (2
Meth lane Chloride
4.6
ND 1)
(
ND 1
()
ND 2)
(
ND (2 H
22 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Station
I N.C.
lGroundwater
Standard 2L
1
Federal
MCL
MW-01
I MW-04
MW-04
I MW-04
Sample ID
1 320111
420411
420421
4204112
Date
9/12/2003
7/19/2000
7/19/2000
5/6/2001
De tb of Sceened interval b s
5 to 15 ft
5 to 15 ft
5 to 15 ft
5 to 15 ft
GanlQsultpnts ofurcern (Ms�) s
1,1,22-Tetrachloroeflum
0.17
n/a
7.1
ND 1)
ND 1
1.7
cichloreethene
2.8
5
1.5
ND 1)
ND 1)
ND 1)
Tetrachloroethene
0.7
5
ND 1)
ND 1)
ND 1)
ND 1
Chloroform
70
100
ND (1)
ND 1
ND 1)
0.4 J
hloromethane
2.6
n/a
ND (1)
ND (5.9)
ND 2.2
3.2
V—v A.nln: Z—Ar l - -.:._. ...:........: ... . . i . _ .. . _..I . _ ..-. z . I . . . .
1,2-Trichloroedme
5
5
ND 1)
ND 1
ND 1)
ND 1
2-Diehkmethene
100
70
ND 2
s-1,2-Diehloroethene
70
70
ND 1
ND 1
ND 1
ND 1
ans-1 2-Dichloroethene
Ivul,
100
100
ND 1)
ND 1)
ND 1)
ND (1
1-Dicblorocthene
7
7
ND 0.11
ND 1
ND (0.11
in 1 Chloride
0.015
2
ttj
ND 2
ND 2
ND 2eth
Methylene Chloride
4.6
5
ND 2)
ND 2
ND (2)
23 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Station
MW-04
MW-04
MW-07
MW-07
Saar kID
N.C.
320412
320421
420711
4207112
Date
Groundwater
Federal
9/12/2003
9/12/2003
7/19/2000
5/8/2001
b of Sceened Interval )
Standard 2L
MCL
5 to 15 ft
5 to 15 ft
30 to 40 ft
30 to 40 ft
L�i:..J.:.reNimJR e«nnnn»x �ien�/: �.. ..:•-..� ".-'....-,. - ^�'.. '.
..
! 1-Tetiachioroethane
0.17
n/a
ND 1
ND 1)
11
26
ricbloreetbene
2.8
5
ND 1)
ND 1
0.8 J
2.4
Tetracbtoroethene
0.7
5
ND 1
ND 1
ND 1)
ND 1
Moroibrin
70
100
ND (1)
ND 1.
0.6 J
0.6 J
hloroutethane
2.6
n/a
ND (1)
ND (1)
ND 1.2).
ND 3.5)
1,2-Trichloroethane
5
5
ND 1
ND 1)
ND 1)
ND 1
2-Dichloroethene
100
70
ND 2
ND 2
-1,2-Dichloroethene
70
70
ND 1
ND 1)
ND 1
ND 1
m-1,2-Dichloroethene
INIliethylene
100
100
ND 1)
ND 1)
ND 1
ND (1
1-Dichloroethene
7
7
ND 1
ND 1
ND 1)
ND 1
n 1 Chloride
0.015
2
ND (1
ND 1
ND 2
ND 2
Chloride
4.6
5
ND d)
ND 1)
ND 2)
ND (2)
24 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
MW-07
MW-07
MW-08
MW-08
N.C.
320711
320712
420811
4208112
Gr:7 dwaterl
Federal
1/13/2003
7/19/2000
5/3/2001
St dard 21,
MCL
30 to 40 ft
.4/12/2,005
30 to 40 ft
25.to 35 ft
25 to 35 ft
0.17
11/a
30 J
9.3
ND (1)
ND (1)
richbtodhene
2.8
5
ND (1)
1.2
ND (1)
ND (1)'
tFctrwhkwoeth=
0.7
5
ND (1)
ND (1)
ND (1)
ND (1)
L02Mfor—M
70
100
ND (1)
0.74 J
2.1
1.6
[ChWenwdiam
2.6
n/a
ND (1)
ND (1)
ND (3.6)
4.7
1,1,2-Trichloroethane
5
5
ND (1)
ND (1)
ND (1)
ND (1)
100
70
ND (2)
ND (1)
11,2-Dichlomethene
is-1 2-Dichloroethene
70
70
ND (1)
ND (1)
ND (1)
ftans-1,2-Dich"oethene
too-
too
ND (1)
ND 1)
ND I
1,1-Dichlomethene
7
7
ND (1)
ND (1)
ND (1)
ND (1)
hinyl Chlod&
I (
0A15
2
ND (I
(I
!ND t(I d
ND (1)
j
ND (2)
j
ND (2)
Meth ene Chloride
4.6
5
ND (1)
ND 2)
ND (2)
25 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Statiw
I
I I
MW-08
MW-10
MW-10
MW-13
Saimple ID
I N.C.
1 1
320811
421011
321011
421311
Date
lGroundwaterl
Federal 1
9/9/2003
5/2/2001
9/10/2003
5/2/2001
Depth of Sceened Interval
Standard 2L
MCL
25 to 35 ft
26.8 to 36.8 ft
26.8 to 36.8 ft
20.8 to 30.8 ft
Canlaminanls afCancern:luQ/Ll...
0.17
n/a
ND (0.59 J)
2
ND 0.59)
ND 1
oroethene
2.8
5
ND (0.27 J)
ND 1)
ND 0.27
ND 1)
r-Tettwh1oroethm
hloroethene
0.7
5
ND 0.22 J)
ND 1)
ND 0.22
ND (1)
oform
70
100
1.5 J
1 J
1.9
0.7 J
2.6
n/a
ND 0.96 J)
ND (1.8)
ND 0.96)
ND 1.9)
IlImpiphior PrwLinlr luo/la. .
! 1,2-Trichlomethane
5
5
ND 0.49 J)
ND 1)
ND 0.49
ND 1)
1 2-Dichloroedmw
100
70
ND 0.63)
ND 0.63)
cis-1,2-Dichioroethene
70
70
ND (0.36 J)
ND 1)
ND 0.36
ND 1)
trans-1,2-Dichloroethene
100
100
ND (0.27 J)
ND 1)
ND 0.27
ND (1)
I l-DichWrocdww
7
7
ND (2
ND 1)
ND 1)
ND (0.11
I1 Chloride
0.015
2
ND 0.26 J)
ND 2)
ND 0.26)
ND( 2
methylene Chloride
4.6
5
ND (0.21 J)
ND 2)
ND 0.21)
ND (2)
26 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Station
MW-13
I MW-14 I
MW-14 I
MW-14
Sample ID -
N.C.
321311
421411
421421
321411
Date
Groundwater
Federal
1/14/2003
5/2/2001
5/2/2001
1/13/2003
Depth of Sceened intervalab)EjStandard2L
MCL
20.8 to 30.8 ft
4.85 to 14.85 ft
4.85 to 14.85 ft
4.85 to 14.85 ft
Contaminants ofCancernaur/L)
loroedmine
0.17
n/a
2.9
0.9 J
1J
17
2.8
5
ND 1
ND 1)
ND 1)
2.3
rse
F
0.7
5
ND (1)
ND 1
ND 1)
ND 1
70
100
0.64 J
1 I
l J
0.56 J
2.6.
n/a
ND (1)
ND (1)
ND 1)
ND (1
�crauenrer•.rrnaucrs rueicr.,.. • - ...� :,;:. - .:.
1,1,2-Trichioroethane
5
5
ND 1)
ND 1)
ND 1
ND 1
1 2-Diehlonoethene
100
70
ND 2
ND 2
cis-i 2-Dichloroethene
70
70
ND 1
ND 1
ND 1
ND 1)
trans-1,2-Dichloroethene
100
100
ND (1)
ND 1)
ND 1)
ND (1
1 1-Dichloroethene
7
7
ND 2
ND 1
ND 0.11
ND (1
Vinyl Chloride
0.015
2
ND (1)'
ND 2
ND 2
ND 1
Methylene Chloride
4.6
5
ND 1)
ND 2)
ND 2)
ND (1)
27 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
MW-16 MW-21 MW-24 MW-24
N.C. 421611 422111 422411 422412
pate Groundwaterl Federal 1 5/3/2001 5/8/2001 5/4/2001 3/27
epth /2002
Dof Sceened Interval (bgs) Standard 2L MCL 3.6 to 13.6 ft 12.2 to 22.2 ft 18.5 to 28.5 ft 18.5 to 28.5 ft
0.17
n/a
ND (1)
3.7
ND 1)
ND (2)
htoroethene
2.8
5
ND 1)
0.3 J
ND 1)
ND 2)
V2-Tetrachloroedume
achloroethene
0.7
5
ND (1)
ND 1)
ND 1)
ND 2)
oroform
70
100
0.6 J
2.1
0.5 J
ND 2)
Chloromethane
2.6
n/a
4.9
ND (2.8)
ND 1.2
ND (2
■/)mmRfnr (7r 7Ru./a./gym//._1 ._.. .. .._ .r.: ...::'. `' .... .. _
1,12-Trichloroedum
5
5
ND 1
ND 1)
ND 1
ND 2
12-Dichloroethene
100
70
cis-1 2-Dichloroethene
70
70
ND 1
ND 1)
ND .1
ND 2
trans-1,2-Dichloroethene
100
100
ND 1)
ND 1)
1
ND 1
ND (2
i i-Dichloroethene
7
7
ND 0.11
ND 1)
ND 1
ND(0.11 J)
Vinyl Chloride
0.015
2
ND (2
ND 2
ND 2
ND (2
Methylene Chloride
4.6
5
ND (2)
ND 2)
ND (2)
ND (5)
28 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
WON Location _
Other
Other
Other
Other
Station
MW-24
MW-25
MW-25
MW-25
Sample ID
N.C.
322411
422511
322511
422512
Date
Groundwater
Federal
9/11/2003
5/4/2001
9/11/2003
3/27/2002
Depth of Sceened Interval b )
Standard 2L
MCL
18.5 to 28.5 ft
18.5 to 28.5 ft
18.5 to 28.5 ft
18.5 to 28.5 ft
1 1,2 2-Tetrachloroethane
0.17
n/a
ND (1)
ND 1)
ND 0.59)
ND 2)
Trichloroethene
2.8
5
ND 1
ND 1)
ND 0.27
ND 2)
Tetrachloroethene
0.7
5
ND 1
ND 1)
ND 0.22
ND 2)
loroform
70
100
ND 1
1.5
ND 0.24
ND 2
Chloromethane
2.6
n/a
ND (1)
ND 1)
ND 0.96)
ND (2)
I n"s.,-A.0a. *jj.s ,4.s-dv4,m/r I ...:;'-". , r.. ' ... Z - , ._.. :, ,-,: ' - - I . .
2-Trichloroethane
5
5
ND 1)
ND 1
ND 0.49)
ND 2
Dichioroethene
100
70
ND 2
ND 0.63
l 2-Dichloroethene
70
70
ND 1)
ND 1)
ND 0.36)
ND 2s-1,2-Dichloroethene
[12
100
100
ND 1)
ND 1)
ND 0.27)
ND (2Dichloroethene
7
7
ND l
ND 1)
ND 1
ND 1
1 Chloride
0.015
2
ND (1
ND 2
0.5 J
ND 2h
lene Chloride
4.6
5
ND (1.6)
ND 2)
ND 0.21)
ND (5)
-uelGaistiluenls;arid;Qthers, /L _,..,: � ...: ..,.
Benzene
1
5
ND 1
0.2 J
ND 0.14
ND 2
Toluene
1000
1000
ND 1)
ND 1.3)
ND 0,18
ND 2
Eth %enzene
550
700
ND (1)
0.3 J
ND 0.15)
ND 2)
Xylem, total
530
10000
ND 2
ND 3)
ND 0.41)
- ND (2
Methyl Tertiary Butyl Ether MTBE
200
n/a
ND (1)
ND 0.49
Acetone
1 700
1 n/a
ND (21
ND (1)
ND (0.63)
ND (2)
29 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
MW-29
MW-29
MW-30
MW-30
ID
N.C.
322911
322912
323011
323012
Date
Groundwate
Federal
3/29/2002
9/11/2003
3/29/2002
9/10/2003
of Sceeaed Interval (bg)
Standard 2L
MCL
34.0 to 44.0 ft
34.0 to 44.0 ft
19.0 to 29.0 ft
19.0 to 29.0 ft
1,1,z2-TetMChtorOCdUUIe
0.17
n/a
ND (1)
3 J
ND (1)
ND (0.59)
Trichloaxthene
2.8
5
ND (1)
ND (0.27)
ND (1)
ND (0.27)
Tefischloroethene
0.7
5
ND (1)
ND (0.22)
ND (1)
ND (0.22)
Chloraforin
70
too
ND (1)
ND (0.24)
ND (1)
ND (0.24)
-Chloronwthane
2.6
n/a
I ND (1)
ND (0.96)
ND (1)
ND (0.96)
1,1,2-Trichlorpedu =nc
5
5
ND (1)
ND (0.49)
ND (1)
ND (0v49)
1,2-Dichloroedwne
100
70
ND (0.63)
ND 0.63)
is-1 2-Dichloroethene
70
70
ND (1)
ND (0.36)
ND 1)
ND (0.36)
trans-1,2-13ichtawethene
100
100
ND (1)
ND (0.27)
ND (I
ND (0.27)
7
7
ND (100)
1 ND (1)
ND 0.}1
ND (1)
I1.1-Dichlorcedwne
Vinyl Chloride
0.015
2
ND (1)
ND (0.26)
ND (1)
N 0. 26
Methylene Chloride
4.6
5
2.1
ND (011)
1 2-8
0.94 J
30 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Wen Locad"
N.C.
Groundwater
Standard 2L
Federal
MCL
Other
Other
Other
Other
Station
MW-32
MW-34
MW-34
MW-43
Sample ID
323211
323411
323412
324311
Date
3/29/2002
1/15/2003
9/9/2003
4/13/2005
of Sceened 1�terval b )
6.0 to 16.0 ft
55.0 to 65.0 ft
55.0 to 65.0 ft
43.7 to 53.7 ft
•-*�---max.-�...�s� . _ .,r.::- _.,,._�.--.. .... ,.. ..
1 1,2 2-Tetrachlomethane
._:.�, ....,,,...._
0.17
... .. .,-._
n/a
ND 1
79
84
66
richloroethene
2.8
5
ND 1
9.1
9.3 J
7.8
etrachloroethene
0.7
5
ND 1)
ND 1)
ND (0.22 J)
0.51 J
Chloroform
70
100
1
0.75 J
0.76 J
0.97 J
hloromethane
2.6
n/a
ND (1)
ND 1)
ND 0.96 ]
ND (1)
hterProdacts' IL t .:..
5
5
ND 1)
ND 1
ND 0.49 J
ND 1
oroethene
100
70
ND 2
ND 0.63
ND 1chloroethene
70
70
ND 1
ND 1
ND 0.36 JDichloroethene
Vhloroethane
100
100
ND (1)
ND 1)
ND 0.27 Joroethene
7
7
ND (1)
ND 1
ND 1)
ND 1oride
0.015
2
ND (1
ND 1
ND 0.26 J
ND 1s
Chloride
4.6
5
3.5
ND 1
ND 0.21 l
ND (1
31 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
Wall Location
Wall
N.C.
Groundwater
Standard 2L
Federal
MCL
Other
Other
Other
Other
Station
MW44
MW45
MW46
MW47
jp
324412
324511
324611
324711
Date
4/13/2005
-4/14/2005
4/15/2005
4/12/2005
Sceened Interval (W)
26.7 to 36.7 ft
26.7 to 36.7 ft
26.7 to 36.7 ft
26.8 to 36.8 ft
0.17
n/a
16
41
7.9
110
Trichloroethene
2.8
5
1.7
4.6
0.77 J
ND (100)
Teftwhlowethene
0.7
5
ND (1)
0.36 J
ND (1)
ND (tOO)
Chlowform
70
100
0.731
0.81
1.8
ND (100)
-Chlovainethane
2.6
n/a
ND (1)
ND (1)
ND (1)
ND (100)
�1,1,2-Trichloroethane
5
5
ND (1)
ND (1)
ND (1)
ND (100)
1,2-Dichlomethene
100
70
ND (1)
ND (1)
ND (1)
ND (100)
cis- 1,2-MchlormM,
70
70
trans- 1,2-Mhlorocthene
too,
100
1.1-Dichloroethene
7
7
ND (1)
ND (1)
ND (1)
ND (1)
Vinyl Chloride
0.01E
2
ND (1)
ND (1)
ND (1)
ND (100)
Methytene Chloride
4.6
1 5
ND (1)
1 ND (11
1 ND (1)
ND (100)
32 of 33

Table 1-2: Historic Detections of Contaminants in Groundwater at SWMU 103
WeA
N.C.
Groundwater
Standard 2L
Federal
MCL
Other
Other
Other
Other
MW69344C
MW69344C
MW69344C
MW69344C
ID
324C11
324411
323113
323421
p
3/28/2002
9/10/2003
4/15/2005
4/15/2005
De t6 of Sceened Interval c
24 to 34 ft
24 to 34 ft
24 to 34 ft
24 to 34 ft
1 i-Tetrachloroethane
0.17
n/a
2
4.1 J
ND 1
ND 1
doldonoethene
2.8
5
ND l
ND 0.27)
ND 1)
ND 1
ittrachtaroeu
0.7
5
ND 1
ND 0.22
ND 1)
ND 1
70
too
ND 1
0.55 J
0.49 J
0.6 J
thane
2.6
n/a
ND (1)
ND 0.96
ND 1
ND (1Rroductshtoroedme
5
5
ND 1
ND 0.49
ND !)
ND !omethene
100
70
ND 0.63
ND 1
ND !chloroothen
N
70
70
ND 1
ND 0.36Dichloroetttene
100
100
ND (1)
ND 0.27)
omethene
7
7
ND (1
ND 1
ND 2)
ND 2loride
0.015
2
ND 1
ND 0.26)
ND 1
ND (1e
Chloride
4.6
5
2.1
0.63 J
0.98 J
0.64 J
„~retCaitstituents;u»d:Qther ... . /L
Benzene
1
5
2.9
2.6
0.98 J
10 J
Toluene
1000.
M000
2.2
4.3
1.8
2.1
Eth lbcnzene
550
700
23.6
14
18
20
lens, total
530
10000
211
141
130
140
MethylTertiary Butyl Ether MTBE
200
n/a
ND (I
ND 0.49)
ND 1
ND (1)
A
700
n/a
ND 1)
ND 0.63)
ND 1
ND (1
0.41
100
ND (1)
ND (0.34)
ND (1)
ND (1)
bgs - below ground surface
MCL - maximum contaminant level
n/a - Federal MCL does not exist for given analyte.
J - indicates an estimated value.
ND - not detected; value in parenthesis is the method detection limit (MDL).
R - indicates a rejected value.
Empty cells indicate samples not analyzed for given analyte.
33 of 33

Table 1-3: Historic Detections of Contaminants in
Surface Water at SWMU 103
Beaver Creek Beaver Creek Beaver Creek Beaver Creek
Nrober
40 + 10
37 + 70
37 +.70
37 + 70
37 + 70 -
37 + 70
Smple Nane
SWS05
BCI
BCI
BCI
BCI
SWSI
sampleto
N.C.Srrface
430511
BCI-SW1L
BCI-SWIH
BCI-SW2H
BCI-SW2L
430111
Date
Water Standard
5/3/2001
10/21/1992
1/8/1993
1/8/1993
2/19/1997
7/17/2000
-aitfaminant o ,.Concern: L '
I,1,2,2-Tetrachloroethane 0.17
ND 1
ND(7)
ND 7)
ND 7)
ND 1)
ND 1
1 12-Trichhumthane
ND 1
ND 5
ND 5)
ND 5
ND 1)
ND 1
ridilavethene
2.5
ND 1
ND(5)
ND 5
ND S
ND 1
ND 1
trans-l2-Dechbmethene
ND 1
ND(5)
ND 5
ND 5
ND(1)
ND 1
is-12-Dichlorocthene
ND 1
ND(1)
ND 1
1 1-Dichloroethem
ND 2
ND 4
ND 4
ND 4
ND(1)
ND 1
Vin I Chloride
0.025
ND 2
ND 11
ND 11
ND(I1)
ND(1)
ND 2
1 of 13

Table 1-3: Historic Detections of Contaminants in
Surface Water at SWMU 103
N.C. Surface
WsterStaadard
Beaver Creek
Beaver Creek
Beaver Creek
Beaver Creek
Beaver Creek
Beaver Creek
NwAm
37 + 70
32 + 60
30 + 80
29 + 80
23 + 20
19 + 50
Name
SW-06
WSW
SW-05
BC1A
SWS07
BC1B
an ID
NDSACE-103SW-06
430611
NDSACE-103SW-05
BC1A-SWIL
430711
BCIB-SWIL
Date
3/7/2006
5/3/2001
3/7/2006
2/19/1997
5/3/2001
2/19/1997
1,1 2-Tetrachlorccdwne
0:17
ND 2 1.4 1.05 J 1.5 2.4 4.8
1 1-Trlchloroethone
ND 1
ND 1
ND 1
ricbiomethenc
2.5
ND 2
0.2 J
ND 2
ND 1 -
0.3 J
ND 1
f 2-Dichloroethew
ND 1
ND 1
ND l
ie-12-IIid�braelhene
ND 1
ND f
ND 1)
1 t.D
ND 2)
ND 1
ND 2
ND I
Vin Chloride
0.025
ND 2)- "
ND 1
ND 2)
ND 1
2of13

This }gage intentionally left blank

1
Table 1-3: Historic
Detections of Contaminants in
Surface Water at SWMU 103
Beaver Creek
Beaver Creek
Beaver Creek
Beaver Creek
Beaver Creek
Beaver Creek
NmAw
19+50
19+50
19+50
19+50
19+50
16+80
Name
BCIB
SWS3
SWS08
SWS08
SW-03
BEAVER CREEK
N.C. Surface
BCIB-SW2L
430311
430811
430821
NDSACE-103SW-03
20701200304
mID
Date
Water Standard
2/19/1997
7/17/2000
5/4/2001
5/4/2001
3/7/2006
1/18/2007
arrt .Cmicern.
f,l ,2-Tetracbh�roetluvie
0.17 5.11
2.5 3.2
3.2
3.46
2.26
Ani�oirincllwv/�Na.�eo/Jj•:e...-:
_:.� ..
. ..:.....:. ... .. f-...::. ... ,.::.:i.. .:,-!:; :_.:..
C,..;. ..,.. ... ;: ::. ., ....:,... .-
. _ _.- ...
... -
_ '
i)-Trichiomethanc
ND 1
ND 1
ND 1
ND 0.333)
riebkwoethenc
2.5
ND l
ND 1
0.5 J
0.6 J
0.57 J
ND 0.702
12-Dichkwoelhcne
ND 1
ND 1)
ND 1
ND 0.374
is-1 2-Dichbroethene
. ND 1
ND 1
ND 1
ND 0.292
Id-Dichloroethene
ND 1
ND 2
ND 1
ND 0.205
1 0:025
M 1
ND 2
ND 2)
ND 2
ND 0.383
3of13

Table 1-3: Historic Detections of Contaminants in
Surface Water at SWMU 103
rt—.M.
N.C. Surface
Water Stshadard
Beaver Creek
Beaver Creek
Beaver Creek
Beaver Creek
Beaver Creek
Beaver Cr4
Nsumber
16+20
15+00
13+00
10+00-
10+00
10+00
CONFLUENCE
SW-01
BELOW SW -I
BC2
BC2 2
BC2
ID
rD=
20701200303
NDSACE-103SW-4M
20701200302
BC2-SWIL
BC2-SWIH
BC2-SW,
1/18/2 007
3n12006
1/1812007.
10/21/1992
1/8/1993
1/4/1991
,
1,1,2,2-Tchachloroethane
0.17 9.29
19 6.93
11
ND (7)
8.4
11.1.2-Trichkweethane
ND (0.333)
ND (0.333)
ND (5)
ND (5)
ND (1)
2.5
0.979 F
1.32 J
ND (0.702)
ND (5)
ND (5)
ND (1)
-I 2.pichloroethene
ND (0.374)
ND 0.374
ND (5)
ND (5)
ND (1)
.2 ichipmedume
ND (0.292)
ND 0.2 2
'()
ND 1)
(
14)ktIowc!=—
.
ND (0.205)
ND (0.205)
ND (4)
ND (4)
ND (1)
in I Chloride
0.025
ND (0.383)
ND (0.383)
ND (11)
ND (11)
ND (1)
4 of 13

Table 1-3: Historic Detections of Contaminants in
. . Surface Water at SWMU 103
N.C. Surface
Water Standard
Water
Beaver Creek
Beaver Creek
Beaver Creek
Beaver Creek
Beaver Creek'
Beaver Creek
Number_
10+00
10+00
10+00
9+10
9+10
9+10
ISmok Nmw
BC2
SWS4
SWSIO
Knox St.
Knox St.
Knox St.
BC2-SW3L
430411
431011
20701200301
20702090901
20704261504
Dale
2119/1997
7/17/2000
5/6/2001
1/18/2007
2/7/2007
4/25/2007
0.17
I l
7.9 12 6.93 .11.5 8.55
ND (1)
ND (1)
ND (1)
ND (0.333)
ND (0.333)
ND (8)
23
ND (1)
ND (1)
0.6 J
0.717 F
ND (0.702)
ND (0. 123)
1,2-Dichlorwthenci
ND (1)
ND (1)
ND I
ND (0.374)
ND (0.374)
ND (0. 113)
ET;rdchUTw'o"qth�ene'
is-1 1. -DkhWwedwrw
,2
ND (1)
0.4 J
0.2 J
ND (0.292)
ND (0.292)
ND (0. 154)
I-D. ichl"pediew
I I 14D
ND (1)
ND (0.205)
ND (0.205)
ND (0.226)
n I Chloride
i inyl
0.025
—7-9D —(I)-
ND (2
ND (2
ND (0.383)
ND (0.383)
ND (0. 163)
5 of 13

This page intentionally left blank

m
Table 1-3: Historic Detections of Contaminants in
Surface Water at SWMU 103
Beaver Creek Beaver Creek _ _ _ Beaver Creek Beaver Creek Beaver Creek
9� + It) 1 9 + 10 Downstream of Knox St. I Downstream of Knox St. I Downstream of Knox St.
[S-amide Name
Knox St.
Knox St.
WETLAND BEGINS
Kenderburg St.
Gniber Rd.
ID
N.C. Surface
20706042807
20710242702
20704261505
20706042804
20704261502
Date
Water Standard
6/2/2007
10/23/2007
4/25/2007
6/2/2007
4/25/2007
orttamirtorie' Concerm G' ..
2,2-Tetrachloroethane
0.17 7.27
11.2 J
1.83
ND 0.156
1.42
1,1,2-Trichloroethane
ND 0.068
ND 0.068 J
ND 0.06E
ND 0.068)
ND 0.068
richlomcthene
2.5.
ND 0.123
ND 0.123
ND 0.123)
ND CO.123
ND 0.123
trans-1 2-Dichloroethene
ND 0.113
ND 0.113 J
ND 0.113
ND 0.113
ND 0.113
is-1 2-Dichloroethene
ND 0.154
ND 0.154 J)
ND 0.154
ND 0.154
ND 0.154
1 1-Dichloroethene
ND 0.226
ND 0.226 J)
ND 0.226
ND 0.226
ND 0.226
IVinyI Chloride
0.025
1 ND 0.163
ND 0.163 J)
ND 0.163
ND 0.163
ND 0.163
6oi13

Table 1-3: Historic Detections of Contaminants in
Surface Water at SWMU 103
N.C. Surface
Water Standard
Beaver Creek
Beaver Creek
Beaver Creek
Holbrook Tribute
Holbrook Tributary
Downstream of Knox St.
Downstream of Knox St.
Downstream of Knox St.
50+70
48+70
Gruber Rd.-
POST BOUNDARY
LEAVING POST
SWS12
SW-14
K712j,2-T.UachlWwoethane
20706042805
20704261503
20706042806
331211
NDSACE-103SW-14
6/2/2007
4/25/2007
6/2/2007
3/29/2002
3/7/2006
0.17 ND 0.156 ND 0.156 ND 0.156 ND 2 ND 2)
1 l-Trichloroedgme
ND 0.068
ND 0.068
ND 0,068
ND 2
ITIrichlomethene
2.5
ND 0,123
ND 0.123
ND 0.123
ND 2
ND 2
1 2-Dichlometbene
ND ,113
ND 0.113
ND 0.113
ND 2
1 2-Diehloroethene
ND 0.154
ND 0:154
ND 0.154
ND 2
1 1-fie
ND fl.226
ND 0.22
ND (0.226).
Vinyl Chloride
0.025
ND 0.163
ND 0.163
ND 0.163
ND 2
7of13

Table 1-3: Historic Detections of Contaminants in
Surface Water at SWMU 103
1.1.2-Trichlorocthane
ND' 2
2.5
ND 2
ND 2
ND 2
2.34
2.24
-1 2-Dichhxo dww
ND 2
is-1-Dichloroediene
ND 2
i 1-D hkwoethene
Vinyl Chloride
0.025
ND 2
8of13

Table 1-3: Historic Detections of Contaminants in
Surface Water at SWMU 103
Holbrook Tributary Holbrook Tributaty
Holbrook Tributaty
Holbrook Tributary Ho I
Nor
36+30 32+65
31+70
30+00
MWple Nam
SW-lo SHARP DOWN GRADIENT
SW-09
SWS14
wo-nok ID N.C. Surface
NDSACE-103SW-10 20710242706.
NDSACE-103SW-09
331411 NDE
Date Water Stauslard
3/7/2006 10/23/2007
3nn006
3/29/2002
;ccocertrAMIJ
11,1,2,2-Teftachloroedum 0.17
28.9 56J
8.23
59.6
11.1.2-Tvicidoroedum
ND (0.068 J)
ND(
ITIrkhtwoo6cne
2.3
ND (2)
6.42 J
1.38 J
5.9
3.29
1 241hchloroathwe
ND (0. 113 A
ND, (2)
is-1
8-l' is i
1 '2.Dichkwocdmw
ND(0.154J)
ND (2)
11n4DichkwOcthene
ND (0.226 J)
i I
in I Chloride
0.025
ND 0.163 J)
ND (2)
90(13

Table 1-3: Historic Detections of Contaminants in
Surface Water at SWMIJ 103
N.C. Surface
Water Standard
27+30
25+00
24+03
23+48
22+84
N="w
SWS1 I
SW-07
LUCAS UPGRADIENT
SwSis
SW-04
JD
431111
NDSACE-103SW-07
20710242705
331511
NDSACE-103SW-04
Date
5/6/2001
3/7/2006
10/23/2007
3/29/2002
3/7/2006
;z;wfVOnCivm (kelU,-'7. , --
-258
I
1 22T-Tch.cMoyneth= 0.17 37 22.9 29.2 J 23.9
'
1,1,2-Tskhkwocth2=
ND (1)
ND (0.068 J)
ND (2)
Trichkwacdww
2.5
2.3
2.74
1.91 j
1.6 J
1.92 J
trans-1,2-DichwMetheft
ND (1)
ND 0.113 J)
ND (2)
1,2-DichWmethene
ND (1)
ND 0.154 J)
ND (2)
I,I-DichWwcdwae
ND (0.226 A
,Vinyl Chloride
0.025
ND (2)
ND 0.163 J)
ND (2)
10 of 13

Table 1-3: Historic Detections of Contaminants in
Surface Water at SWMU 183
1.acaiiaa Holbrook Tributary Holbrook Tributary Holbrook Tributary Holbrook Tributary Holbrook Tributary
Nor 22+84 22+84 22+94 17+30 17+30
N.C. Surface
Standard
ABOVE WEIR
BELOW WEIR
WEIR RADIENT
BC1D
SYSTEM CULVERT
FName
{p
20701200306
20701200305
20702090902
BC1D-SWIL
20702090903
D=2te.Water
1/18/2007
1/18/2007
2/7/2007
2/21/1997
2/7/2007
. '-VNII•CI M•. 's f: af. ....n r:-...:. :....._:..ry. ,. :: w. a _J.:.. -.': _:-f..-....
.: �.'-:'.
_rr_- _
11-Tetrachloroetliane 0.17 7.56
6.79
30.8
27
29.2
} 1-Tr)chbray�
ND 0,333
ND 0.333)
ND 0.333
ND 0.333
ITrichlorog"ne
2.5
0.92 F
0.905 F
1.12F
1.3
0.955 F
trans-1-Dichloroetheoe
ND 0.374
ND 0.374
ND 0.374
ND 0.374
ND 0.292
ND 0.292
ND 0.292
ND 0.292hloroetbene
ofti:K-Dichlowethew
ND 0.205
ND (0.205
ND 0.205
ND (1
ND 0.226hloride
0.025
ND 0.383
ND (0.383)
ND 0.383
ND (1)
ND 0.383
11 of 13

Table 1-3: Historic Detections of Contaminants in
Surface Water at SWMIJ 103
N.C. Surface
Water Standard
Holbrook Tributary
Holbrook Tributary
Holbrook Tributary
Holbrook Tributary
Holbrook
•
17+30
17+30
17+30
17+30W
17+1
AlgaeNI
w
Holbrook Culvert
Holbrook Culvert
SYSTEM CULVERT
BCIC
SW
1, D
20704261506
20706042802
20710242703
BC1C-SW1L
430:
Date
4/25/2007
6/2/2007
10/23/2007
2/19/1997
7/174
MaW4fC gw-OnP
11,12.2-Tetrachloroethane
0.17 18.3
18.1— 24 J 32 J ND
ND (0.068)
ND (0.068)
ND (0.068 J)
ND (1)
IT,richloroethme
2.5
ND 0.123
0.987 J
ND 0.123 JO
2.2 J
ND (1)
8-1.2-DichloraWmic
trans-1
ND (0. 113)
ND (0. 113)
ND (0. 113 J)
0.4 J
i-1,2-Dichloroethew
ND(0.154)
ND (0. 154)
ND (0. 154 J)
0.7 J
1l.-IDichloroethene
ND (0.226)
ND (0.226)
ND (0.226 J)
ND (1)
inyl Chloride
V Vi I
0.025
ND 0.163
ND 0.163
ND(O.163J)
ND (1)
0.4 J
o 12 of 13

Table 1-3: Historic Detections of Contaminants in
Surface Water at SWMU 103
I..10dott
N.C. Surface
Waster Standard
Holbrook Tributary
Holbrook Tributaiy
East Fork
East Fork
East Fork
r
17 + 30 W
17 + 30 W
35 + 00
35 + 00
30 + 00
SWS09
SW-02
SWS16
SWS16
SWI-EASTFORK
430911
NDSACE-103SW-02
331611
331621
20710242704
MI.
5/4/2001
3/7/2006
3/29/2002
3/29/2002
10/23/2007
: L',onceJlJloroethaue
.2
0.17 0.7 7 21.4
ND
ND 2
2.58 J
1,1,2-Ttrichloraelhatic
ND 1
ND 2
ND 2)
ND 0.068 J)
richkweedwat:.
2.5
ND 1
1.48 J
ND 2
ND 2
ND 0.123 JO
tram-1 2-Dichbraet WM
ND 1
ND 2
ND 2)
ND 0.113
is4 -Dices
ND !
ND 2
ND 2
ND 0.154
t 1-Dic6locoetht ae
ND -1
ND 0.226 J
in I C6lacide
0.025
ND 2
ND 2
ND 2)
ND 0.163
F - indicates analyte detected above the MDL but below the P.L.
J - indicates an estimated value.
ND - not detected; vatuc in parenthesis is the method detection limit (MDL).
R - indicates a rejected value.
Empty cells indicate samples not analyzed for given analyte.
13 of 13

TABLE 3-1
SOURCE AREA INJECTION PROTOCOL
SUMU-103
FORT BRAGG, NORTH CAROLINA
1 hl.b Sabalr.1.1 M I Total V.t —
1.IeeM I.Jeetia Eatabi $Fred.$ 3�.Y adkd% M&A.P W.rr+ 1.4-5
tetanalSpl+V.lu. S-ybee.0o L. late Neal Ira OY A water Sabatrate Sbatmladream .t3�
Flood FrreeM S.bamk by W*W 7.3% Finial Lactic, Add Ctra.tratirc N gnLmmM er ►ereea 011ky Vckaac le e��. 73%
Frl hrem Water by W • 924W. FW ON C fR
GIVE T"ATMENT ZONE CONCENTIIATIONS
Dedp Uk(y—): IH Ladle AcM Treat eat Z.a Caetatratla (m/L): 119 Fat VeVebk00Coectsa.11ee(tq/L): IA"
NUTM Sete♦ Lactate Freieel
1. Aawmn wifiClear sodium Ixmm product is 60 paceoe smftum lactate by weigh.
I.
Molecular w igh of s.,bm bctne (CHrMOH-COONs) - 11206.
. MaKwar weigh of look Arid (CAo,) - 90.08. -
4. Spatifc gravity of WiUCkw Product - 1323 @ 20 dews Cebkm
. Wdph of uclear Product - 11.0 pamda per pllun
ttest per p0oo of lactic aeid ie prods -1323 x 8.33 Wgd Hr0 x 0.60 x (90.08/11206) - 531 �pL
OTESiFaFnsfe-e Fr -dad
1. Aest®es Guctme produce is 80, f.aae sugar by weigh.
OTEL V""Ab on E...Nm hadet
1. A -stores —kim proAat is 60, soybean oil by weigle. _
2.Soybea oil n 7.8 ponuds Per palm
. Aswmea ofetatiiaproduce is 0.96 and tbas euukim product is paccosodiurnhwr
D— G.U—
Taal
Totes
GRUM
Total
Emu4im Prod ct
Pmubioo Product
I 33
14.9
I
220
3.7
Ned Oil
Nest Soybean
Oil
. 1 35
920
1
220
23.0
BuffaAaM
BufferApea
1 33
13.5
1
220
3.4

TABLE 3-2
YEAR ONE EFFECTIVENESS MONITORING PROGRAM
SWMU 103
���a�aaaaaaa
®a����aaaaaaa
®�®��aaaaaaa
��■�a�iaaaaaaa
���a��aaaaaaa
®®����aaaaaaa
���a��aa�■aaa®
®�a�iaaaaaaa
��a��aa��aaaa
���a�''aa■�oaaa
�®����aaa■sa�a�a
���s��aas��a■�
o���®��aa�■��a�
�����■��a®sans
r�u�
®■i■�
®ate
��
��
�
®�■�
" Wells within the source area will be'sampled quarterly for the first year, then will be sampled annually.
"' Volatile organic compounds (VOCs) to include aromatic and chlorinated aliphatic hydrocarbons.
d Well head analyses include dissolved oxygen, oxidation-reduction potential, pH, temperature, and conductivity.
m Mobile lab analyses include carbon dioxide, allmlinity, ferrous iron, and manganese.

FIGURES

This page intentionally left blank

J
we
-71. 5
i i 1239
9 ��`� / /' p !+t�•j_'JIlv�i � ' N: �O 1247
Z G�i � ^CCU^ p VVJ � 11391
SHONE..
56...
I FORMER HEONG. i
CT, .ROAD - $WMU 103c OIL. us
= j C
PARKIhG\ N to P ING. '
1 STORM WATER / cj357. m 1 g 50m O
\OUTFACE
693448 / 6B9321rn
o� co
IVE ` B wq� /o
o \n 5B p! �0,11
o \
\
ku
s 9 ?
A�0. C!'/0O .��'•
BISHO q► °� n �^ °m
TREE7 0? \O O'r�m�O 4q x•
� spa
)
6¢'J46 6{S NOW
S 4
°V
cc 65
,p. Sg 4
ATKINSO
STREET
Q ss
6 . _ 4
� �93u�36
654 1
LEGEND S• E NEER.DISTRICT
U.. ARI[Y NGI
�•A,: CORPS OF.:ENGINEERS'
. ............................ . BUILDING SAVANNAH. GEORGIA
........................ ASPHALT ROAD UOOmi 06fR.1
.. — ............ ....:.... STREAM OR CSAwn
REEK CORPS OF CNGNWtS
SAVM&Wt'UOMA
225�. (5-FT INTERVALNDATUMLIISEMEAN SEA WITH ELEVATION
. LEVEL SITE MAPANDSURFACE
:.......................CONTOUR LINE TOP.OGRAWOF SWMU 163
BOUNDARY. AS IDENTIFIED IN 0. 200 400 FORT BRAGG; NORTH CAROU.NA
............ RFI; (USGS 1996a) FOR SWMU 5 "
. DRAYH REY.NOJDATE: .. CAD FLE: - -
SCALE.1" --400' R.BEELER I 0/11-17-05. /99004/DGN/BBD_103SITEr01
Fkam 1-1. Site Abp smdSurbc, e.Topogmphy-of SWMU 103.

t� en20 (n}��`wkritc.TSS4acaTtata q �' a.
�R5 18 GROId10. LOCATLOM)
.M46,0. �p3 Wfi [✓DID' .
OA�CKGROUND)
• \ 19,5
� p C 1 ful CYtT ,�.tVI-1 . CS
RT° S IAW N 13.. ,,i Y� //fjg ruura 9'
6 A5r0 .`�r�, f'H641 &p8 v
41B
't7' 1 . ✓PAI 0� PMp t O, tTdO n .'' ' •UItB].L� � .O❑ �j ',�
r � 1C4'n :Ji AEiih1-9-. �' \�� �� ! � p • 1"/.'
p� h, d o
a �r 7 d- �✓ �.
W_w y'
1 �' . ./ �. ��. � V � 'Si �f � , I-y. tl05.Gr � .8 l�Y�;�'• ' awu�ate j4�\ Iaj m
]5efnw to '.
\ itf8S7 neoa)'i f, CP d 4 P CP d
185. f s6v0 5 + i" r, nryv 19 Q pb' �fj. sr.A
.. 'Q \.Ly4 n 4 PlloiEllR� q � .LS�r'.
` �_ `B3'�51�' t•1"' ~� ,\ ) ..� O Q OQ . G7 o
\. i .. "-- ` �; '�suas4i \ Itah Di � 'a,:O p 0 A-CJ p 9 4 d b c,�@ ' @ \ d e� �•
--L' ���, i \ 9 s Q• p i3 p Q A d P O� .cl U y� 4: c. _0.
1
). p O �helmn � n dl1 p R ij !3 p tl
', a•p • a p.y' uw y n
ra.'a o Q (a A a '� 13 '= Q 'dim "��y'� AC4
j 4 is Al l,\ 6'm.47. Qq'�s if% "\J��. °� d� .U.•� " 17p
LEGEND.
AD SHALLOW: MONITORING -WELL LOCATION
DEEPr1gf+9T0f, pjn 91EI.L Loco ON
,NOTES:
It INTERMEDIATE• MONITORING WELL LOCATION
MW1 - MW9 INSTALLED JUNE 2000.
5188.34). ELEVATION..OF. CLAY, FT AMSL•
MW10 - MW25 INSTALLED ,APRIL. 2001.
Q DEEP- SOIL BORING -
TAW26 -: MW33: INS.TW_LED MARCH- 2002.'
i?Fif'.";.rr SvAfi;.{;. pEA�TtJitk', -
4MWS6 - 4MWS111NSTALLED MARCH 2002..
tdW34 - MW40 INSTALLED. DECEMBER'.,002:
--- REtIISED 80UNOAR'f OF SWMU'5 AS IOEi)TIFIED. IN PFI
draw1745446 SWMU 103 Mao Fiaures.cdr ma 10112/07: Pa .1

a
\L,
� `216 t~`4ua5;
'I N t�l4 i 23 '� a]M"e <xI.,T Inr,Ri-g;i a.LJ
�� ,o $ d [[11 �n�` otminz,rLGcnTltx(124� m � a.}I
/Nr r ma+ I B 3r
O
222.
Y
S e�s o
S� 103
i"..a:•. uw 7 vzz O'� FD-QRISR HEATING- GYM &Gp?q G%, v.sw 5 0o r
IL ,STs4H-z➢
22�0, eL
�Qa� 7 a � � , A• I3 .g �� a �� � .B o--
Al—
I uM ro
�xu G, ,� � � � ,Ta t9 a� �e,t�� Q-� ° v u®tea, ❑ Q a8 , u
,4:i 4 EI R ELTA
�LENENTARY, SCHOOL q y�•- mfl p � �`i, � s a, �„
I L,y .i 0 0�2' •I' t 0� 'O A' Fp�L,
� r
1ON
--�. �,;i •"\. Ida:e.
` t. e o � cQ w✓aa�' m Q�C �%Q�',,�r r' f?� �im �
i °,."291 SueR7 HAS
at inn G' ao JQD m9 �'�' • 't% . - F) �: � 6 a
i e .11: S d
e'A A l?SV ,2 p I
mc
c
n63
LEGEND
"Z .SHALLOW MOfJfTORING WELL, LOCATION
NOTES:
DEEf-". NffitnTOkItJG 1',rE1.4 LOCKNOEJ
NW1 - MW9 .INSTALLED JUNE, 2000.
m INTERIJEDIATE'MONITCIRINGWELL LOCATION
MW10 =. MW25 INSTALLED, APRIL' 2001.
r,1W26'-,MW32 INSTALLED'MARCH 2002.
--`UtTF iCE-S!ATEf1, t; GATUI?E.
41"IS6 - 4MWS11INSTALLED NIARCH 2O02.,
--E30UAf0,Vt}' 0F'.'3147dU 5, AS IDEJ;dTIt3"c0,u4 P.FI
MW34 - NIW40 INSTALLED OECENBER 2002.
" (U.SGS ' Q0)
DIRECTION' or, GROUNDWATER FLOW
0SIYMI 103 ANO'FORMER HEATING -OIL
UST LOCATIONS
— — BOUNDARY OF SVU 4
dtaYA745446 SWMU 103 Map Fiaures.cdr ms 10112107, Pa 2
FIGURE 1-3
POTENTIOMETRIC SURFACE MAP
N FOR SHALLOW GROUNDWATER
FOR SWMU' 103; SWMUs 4 AND 18,.
AND: VICINITY (September 2003)
Fort Bragg, Norih. Carollna
0 300 600
SCALE: PARSONS.
Denver,. Colorado

Q.?�J `R ✓;'f 9om!v Ltrt,TUxO.
ea.
­ ,r tuOun COCn)larr"
rna:w r
-
rswlnl. 4 fe e2� rma
m o / 1'I 9acx 1p1 ..-
'%F•
-322.4. - Q•
2 a97 08 �L „ c
g Fr snF096EN HEATING cnC- �p �B vu sol oo
224eaitr /,,`2�,�W r254 'OIL' USTsr;3,,g (7 gI(R'�'�� e0 {1 0 ({`y^��'}.
0{�,�'� }{'gyp �' 4 omo •• "\�•.
2Ja7 FL IS m t$ 1i Cy
�20 1V2f, U 149 . ,A� J n ¢ •iY J_4q .,em
g [�F71,
rAaoo
HA13A
1• f'K 1 22065 U' 't.\. \]49 .• '�(t. Ey1; $�}j �. i1 l d o
' .2 f iin�"�rzuWmf REHA1 ... \
SIt11�r18t t. uFV 3-MN 37 �� 7 is .a
4t12W3\V v�l. �21]:f .2�656 dm dlsd �. vaaK.
Qy -Pl , ��_ '. 2i8 •. . f~ i.,• v � \ se �fLN! 1,, '`r i`QYw. ;3.. NTA
wu2u.zeELEMENTARY RY SCHOOL.
C a •.
q\nr\ 2ta f3 ` a9 a51a Y 1 �- 6. t q �iy y� m __ram
t C O•bU.�f
f9r wsr 1 2] m 6 a G pa Ga'o Q 'q' a o rm£c��� m� e
\'20-.-
6. 6 R A(t d_ b 1q .c'. : �' _ 1 ��. 1f:a� �- G' op O�� •P � m W El
ti:r., 5� 9YY5 20B •, m r Q .&q.G OqI, m9- 4 Qb owl/ co a. n
b
ty o�
' '�l4rcr roo � u �\D gdmd —•• m�� 9.� m C;c^m�f.7 ; d
LEGEND'
It ;SHALLOVY f,1CPIITORING; WELL. LOCATION
�;). DE'GPA40"f-bRIN,G N/EliL,L0tATI6N
ID . INTERMEDIATE -MONITORING WELL LOCATION
--• SURFACE WER.'P+F,'t,TU+CG
--60U1JflARY .PF uVIMU a 46 IDENTIFIED 31 RFI
(Usr, :.10001
SWMU 103'AND-FORMER HEATIN07DIL
UST LOCATIONS
BOUNDARY OF SWMU 4
NOTES
MWT- MW9 INSTALLED JUNE 2000.
MWI0 - MW25'INSTALLED APRIL 2001.
AIW26 - NIW32 INSTALLED MARCH 2O02.
4MWS6 - 4MWS111HSTALLED MARCH 2O02.
MW34 - 1AW40 INSTALLED DECEMBER'2002.
IJ
0 . 3�W�600
SCALE.. V = 600'
draw1745446 SWMU 103 Map Figures.cdr ma 10/12/07 Pg 3

35° 15'
79' 15' 79° 00'
Lidle River
Llple River
SWMU
Pope 103 ,I{,
Air Force •f�• 1t
ro l]adoRher
Base-N-
1
�C or nirn.rnm
Cr. �� sr
. Cr. `^.J r. birheRna • ■ .+�rr�..T . Dralna9e aia� r5mr •./ •
Divide. ,r a• r� cr..
O Mammon wimioo. Drainage o-r
/: asSao
r
• O" 1■ �M Cms
NlrMhnn rrftm •+�• Cr.
Cn Barter • 'XnmLmr
LIuW Cr. Bml r Lys,
PO
Boo- h a' AfLnnu d Lowrr �`
Cmn Br. Jr yPY • G4 Eefir
River
(C.Tr � - Broom Chn;
Drorldah acik \ ` Rarh�rh 'nice / lbmt .Lya
tr. Lokr
Fort<Bragg
Ilitary. Rese'rvatio,
Boundary
35- 00'. G05-0250D
0: 5 10 15 Miles
0 5 10 15 Kilomefers
—■■�■■� Drainage Divide
------- Fort Bragg MllltaryInstallation- Boundary
River or stream FIGURE 1.!
RAIN
De
draw1745446 SWMU 103 Man Fiqures.cdr ma
E

r p C4 g Pgc� •• v .
00
r' 2.
lop a_ . eycutt
kioneycti4l:Rd :,j_
SOURCE PREA:
N
,ems n
1 . I - hacP Dc
IVi1N-fit t�
N\\X___'0*1P' I p� .tea h1D
Legend
0 ` , S - Site Boundary
1 YG Street/Road
Rail Road
Stream $
/r 5�
a 1 ® 0 Building
1 i ?.�'.'" NW I Wetlands Proposed Deep Monitoring Well
c� 7
Fence ® Deep Monitoring Well
I mj M 1,1,2,2-Tetractiloroe;hane
SIP
FIGURE 31"
chi SWMU-103
+ SOURCE AREA TREATMENT
USING ENHANCED 61OREMEDIATION .
AND ENGINEERED. AERATION/
VOLATILIZATION'OF SURFACE WATER.
c� FortBragg NG
PARSONS .
r� 1
Denver; Colorado.
'SAE&GIS1FtBragg1S W MU
1121/08

agend
Street/Road
M Organic Substrate Treatment Area
ED Injection Well (Radius of Influence)
0 Injection Point (Radius of Influence)
Deep Monitoring Well
(Depth (fi) to Top of Clay)
Injection Well
Q5
Shallow Monitoring Well
(Depth (it) to Top of lay)
Removed Underground Storage Tank
J
Direction of groundwater flow through the source area
-MW-48n:
(441
(>37
.-W-2
.(44.2-!
MW-4' N
(>37.')
Coordinate System: North Carolina State Plane, NAD83, Feet
Feet
30 Is 0 30
SWM.0 103
'PARSONS Fort Bragg
North Carolina
UJOSY:
BT
SWMU 103 Source Area
LH
PROJECTNUWFR
KED BY: SCALE As Shown
AK 745446.30020
FIGURE
*UTED BY.' I — January 2008 NU&IBM.
-
JD FILE: XAGIS%fLbmggW1apsTg1-3.md 32
S:W-SXG[SIFtBragg%SWMU-103_Final _ProjectAreaLZoormffLxd [xh 12,1108

r
.l
..
�)oyoean
Oil
Emulsion
Product
Neat . pH..
Fire Soybean Buffer:
'Hydrant/ . . . Oil Product:
Water Truck 20,000, gallon
Froc Tani( :
Flow Diaphrag In Line Mixer —�To Anjecti°sn;
Meter .:Pump .

From
Mix! Flo+n
System Mete
jection Point
rn
Injection Point
0
Iniection:Point
G 0
�c ,e..
9�. o
LEGEND
® BALL VALVE
TITLE SWI V.1®3
CORRECTIVE MEASURES IMPLEMENTATION FLAN
SUBSTRATE. INJEQTIO. N .SYSTEM
PRESSURE GAGE
LOCATION'
FT. 3RAGG; NORTH.CAROLINA . .
CHECKED BY
D. GrlO the
PARSONS
DRAFTED BY
MA
3.=4
FILE
drawW45446 Sl S stenixdr
.
DATE:.,' ".
9104/W
. draM745446 SWMU 103 Maps Figures.edr.ma 1123108 Pg 7

��Ycutt R� d �J
a t
yodeyo4
i �d
t Legend
Site Boundary
rr Street/Road
Rail Road
Stream
0 Building
NWI Wetlands
Sta 10 0 Roughen Streambed
Proposed Surface Water Sampling Location
Coordinate System: North Carolina State Plane, NAD83, Feed
Feet
400 200 0 400.
SWMU 103
PARSONS Fort Bragg
p:.
' North Carolina
GNEDe.:
BT SWMU 103
BY: Surface Water Corrective Measure
LH Ste 1- Rou hen-Streambed
'CI DBY: 6CJ1LE: As Shown PRCUEq NUMBER:
745446.30020
B„EDBY, D„£ January 2008 „ MBER:
FlLE: X%GI511Lhre8giM8ps15g1-3.fmd
3-5
S:IESIGISIFIBraggISWMU-103 Fba IM_Riprap.rtuctl bch 1121108 .

ionally left blank

ionally left blank

SAESIGIS\FtBraggISWMU-103_SourceAT_PilotTest.nixd Ixh 1121108

This page intentionally left blank

base flow culvert over flow culvert over flow culvert
upstream entrances to culverts
;�,-, ., jbelfle (plywood stabilized YAM sandbagging)
Ficiures.cdr ma

This page intentionally left blank
I `J

Plan View
150 gpm
conduit
---------
---------- ---
cover
.
;
W
r
�.
T�
y.
low-water.
�_.
. .
switch
1_
:level
...
to •44'ERR.
.l .l .1
'
e;pump
_---submerse
0'
r
10
corrugated metal:
y .,rwy yus
•®.
��
Y GL
culvert material
4M+ri s-'n)i iFhNh� h4W^4-ril+'S -y Mi h /' 1 ell
S L i V i
i fl ;}5 �r5. '�1 j�r'^�-f +ii7yy � � � �•
i 7. � y
t- y 1 � 5 r
S� t"' +��5i
.. ..
'�
slotted`screen
._.....,. �1.....- ........
�. Section View
Egtavel .filter pack
(pea gravel):
draw1745446 SWMU 103 Map Figures.tdrma 10/17/07 :Pg 13
-1.

This page intentionally left blank

control valves
steel piping with 118"
holes at 2" seperation
25`
17'
/er,.Colora2
draw1745446 SWMU 103 Map Flaures.cdr ma 10/12/07 'Pp 10

—.
0:38' 1.0'
base flow calved over flow culvert overflow ctiverl
upstream entrances to culverts
IN
downstream exit of base flow dulvert
f I baffle (plywood stabifted with sandbagging).
FIGURE 3-1.1
SURFACE WATER
AIR.SPARGER.BAFFLE DESIGN
Fort Bragg;. North Carolina
PARSONS
Denver, Colorado
dravA745446 SWMU 103 Map Figures.cdr ma 10/12107 PO 11

This page intentionally left blank
- -�

N
Feet
0
250.
500
S:IESIGIS1FtBragl
Spea
I� ��,�MIIN28
i N
00
Honon y
SOURCE AREA
eMW20�
0neyu►tt'Rd .. ®MW �t�J I'`
NI 2_ W12 took. ®� M1tU22 ' 1 �'LQM t tl
1\f M'w-4U` 4PMA
♦ r.
�1MW3.
o �„ It;\�TW�39 MW® QMW31
a
Legend
W19 ; YG Site Boundary O Proposed Surface Water Sampling Location
Street/Road
t\� S6 S2 ; • Proposed Deep Monitoring Well
Rail Road
Stream ® Deep Monitoring Well
1 1
0 _Building
� 1
a of NWI Wetlands ® Shallow Monitoring Well
1 u�r Fence r 1
�Oh 1 1 1 r 1,1,2,2-Tetrachloroethane
`�f I M 33 1 ` . " r New Fences and Gates
' D ;3 �.
o FIGURE 3-12
[ \ FENCING -AND MONITORING NETWORK
SWMU-103
Fort Bragg, NC
O�
i 1 PARSONS
. Denver;"Colorado. _
JM etwork:mxd Ixh 1/21/08

i
t
I
I
SG1.,.' MW°355 i
10W.
SG2 XSG3 !
t
SG18® $G5
®SG4 ESG7
SG17
HOLB000K
SG16 ELEMENTARY : ®SG6 . !
CSC OOL SGS
®SG9
SGt4 .�
ESGIO
HS01 ■SG11
c
n
®SG13 OKSG12
IdNd=37� _
- / J
t
FIGURE 3-13
LEGEND: SOIL GAS MONITORING
0........ ........... ..... BUILDING
........... ... ASPHALT ROAD NETWORK AROUN
..._.__ ................ SURFACE. WATER FEATURE HOLBROOK ELEMENTARY_
Q..............SHALLOW MONITORING WELL LOCATION (JUKE 2006.) SWMU.'
................. DEEP MONITORING WELL LOCATION
■ ..............SOIL GAS MONITORING WELL LOCATION
....................... CRAWLSPACE AR SAMPLE 0 50 100 Fort. Bragg, North Carolir
ALE"I" = 100' PARSONS.
Denver, •Colorado
d,e.A7ASAGR CWMI 1 1n2 Man $:I,, ac edr and 101ndln7Pn 5 - .

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APPENDIX A
SUBSTRATE INJECTION CALCULATIONS
w

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J
TABLE A-1
SOURCE AREA INJECTION PROTOCOL
SWMU-103
FORT BRAGG, NORTH CAROLINA
1. Treatment Zone Physical Dimensions
Width (Perpendicular to predominant groundwater flow direction)
Length (Parallel to predominant groundwater flow)
Saturated Thickness
Treatment Zone Cross Sectional Area
Treatment Zone Volume
Treatment Zone Total Pore Volume (total volume x total porosity)
Treatment Zone Effective Groundwater Volume (total volume x effective porosity)
Design Period of Performance
2. Treatment Zone Hydrogeologic Properties
Total Porosity
Effective Porosity
Average Aquifer Hydraulic Conductivity
Average Hydraulic Gradient
Average Groundwater Seepage Velocity through the Treatment Zone
Average Groundwater Seepage Velocity through the Treatment Zone
Average Groundwater Flux through the Treatment Zone
Soil Bulk Density
Soil Fraction Organic Carbon (foc)
3. Initial Treatment Cell Electron -Acceptor Demand, (one total pore volume)
A. Aqueous -Phase Native Electron Acceptors
Oxygen avg of 4 readings
Nitrate
Sulfate
Carbon Dioxide (estimated as the amount of Methane produced)
Soli
B. Solid -Phase Native Electron Acceptors
Manganese (IV) (estimated as the amount of Mn (II) produced)
Iron (III) (estimated as the amount of Fe (II) produced)
Solid -Pt
C. Soluble Contaminant Electron Acceptors
Tetrachloroelhene (PCE)
Trichloroethene (TCE)
Dichloroelhene (cis-DCE, trans-DCE, and 1,1-DCE)
Vinyl Chloride (VC)
Carbon Tetrachloride (CT)
Trichloromelhene ( or chloroform) (CF)
Dichloromethane (or methylene chloride) (MC)
Chloromelhane
Tetrachloroethane (1,1,1,2-PCA and 1,1,2,2-PCA)
Trichloroethane (1,1,1-TCA and 1,1,2-TCA)
Dichloroethane (1,1-DCA and 1,2-DCA)
Chloroethane
D: Sorbed Contaminant Electron Acceptors
(Soil Concentration = Koc x foc x Cgw)
Tetrachloroethene (PCE)
Trichloroethene (TCE)
Dichloroethene (cis-DCE, trans-DCE, and 1,1-DCE)
Vinyl Chloride (VC)
Carbon Tetrachloride (CT)
Trichloromethane (or chloroform) (CF)
Dichloromethane (or methylene chloride) (MC)
Chloromethane
Tetrachloroethane (1,1,1,2-PCA and 1,1,2,2-PCA)
Trichloroethane (1,1,1-TCA and 1,1,2-TCA)
Dichloroethane (1,1-DCA and 1,2-DCA)
Chloroelhane
Values
Range
Units
117
1-10,000
feet
93
1-1,000
feet
15
1-100
feet
1755
-
ft2
163,2 55
-
ft3
366,752
gallons
183,176
-
gallons
10
.5 to 5
year
30 %
.05-50
15 %
.05-50
7
.01-1000
ft/day
0.008
0.1-0.0001
fl/ft
0.37
-
ft/day
136.3
-
ft/yr
268,396
-
gallons/year
1.65
1.4-2.0
gm/cm'
0.0021
0.0001-0.1
Stoichiometric Hydrogen Electron
Concentration Mass demand Demand Equivalents per
(mg/L) (lb) (wt/wt h2) (lb) Mole
4.0
1 12.23
7.9
1.55
1 4
1.3
1 3.97
10.2
0.39
5
5
15.29
10.6
1.45
8
15.0
1 45.86
5.5
8.40
8
ble Competing Electron Acceptor Demand (lb.)
11.8
Stoichiometric Hydrogen Electron
Concentration Mass demand Demand Equivalents per
(mg/L) (lb) (wt/wt h2) (lb) Mole
1.0
1 3.06
1 27.5
1 0.11
1
5
15.29
55.9
0.27
1
ase Competing Electron Acceptor Demand (Ib.)
0.38
Stoichiometric Hydrogen Electron
Concentration Mass demand Demand Equivalents per
(mg/L) (lb) (wt/wt h2) (lb) Mole
0.000
0.00
20.6
0.00
8
0.000
0.00
21.7
0.00
6
0.000
0.00
24.0
0.00
4
0.000
0.00
31.0
0.00,
2
0.000
0.00
19.1
0.00
8
0.000
0.00
19.8
0.00
6
0.000
0.00
21.1
0.00
4
0.000
0.00
25.0
0.00
2
0.470
1.44
20.8
0.07
8
0.000
0.00
22.1
0.00
6
0.000
0.00
24.5
0.00
4
0.000
0.00
32.0
0.00
1 2
Total Soluble Contaminant Electron Acceptor Demand (lb.)I 0.07 - 1
Stoichiometric Hydrogen Electron
Koc Soil Conc. Mass demand Demand Equivalents per
(mug) (mg/kg) (lb) (wYwt h2) (lb) Mole
263
0.00
0.00
20.6
0.00
1 8
107
0.00
0.00
21.7
0.00
6
45
0.00
0.00
24.0
0.00
4
3.0
0.00
0.00
31.0
0.00
2
224
0.00
0.00
25.4 .
0.00
8
63
0.00
0.00
12.3
0.00
6
28
0.00
0.00
21.1
0.00
4
25
0.00
0.00
25.0
0.00
2
117
1 0.12
1.94
20.8
0.09
8
105
0.00
0.00
22.0
0.00
6
30
0.00
0.00
25.0
0.00
1 4
3
0.00
1 0.00
32.0
1 0.00
1 2
1 otal soroea t:ontammam tlectron Acceptor uemano til u.uy t
(continued)
A-1
103 CMIP App A injedtonxls
11 2008

4. Treatment Cell Electron -Acceptor Flux (per year)
A. Soluble Native Electron Acceptors
TABLE A-1
Concentration
(mg/L)
Mass
(lb)
Stoichiometric
demand
(wt/wt hz)
Hydrogen
Demand
(Ib)
Electron
Equivalents per
Mole
4.0
8.96
7.9
1.13
4
1.3
2.91
10.2
0.29
5
5
11.20
10.6
1.06
8
15.0
33.59
5.5
6.15
8
Oxygen
Nitrate
Sulfate
Carbon Dioxide (estimated as the amount of Methane produced)
Total Competing Electron Acceptor Demand Flux (Iblyr
8.6
B. Soluble Contaminant Electron Acceptors
Tetrachloroethene (PCE)
Trchloroethene (TCE)
Dichloroethene (cis-DCE, trans-DCE, and 1,1-DCE)
Vinyl Chloride (VC)
Carbon Tetrachloride (CT)
Trichloromethane ( or chloroform) (CF)
Dichloromelhane (or methylene chloride) (MC)
Chloromethane
Tetrachloroethane (1,1,1,2-PCA and 1,1,2,2-PCA)
Trichloroethane (1,1,1-TCA and 1,1,2-TCA)
Dichloroethane (1,1-DCA and 1,2-DCA)
Chloroethane
Stoichiometric Hydrogen Electron
Concentration Mass demand Demand Equivalents per
(mg/L) (lb) (wt/wt hz) (Ib) Mole
0.000
0.00
20.6
0.00
8
0.000
0.00
21.7
0.00
6
0.000
0.00
24.0
0.00
4
0.000
0.00
31.0
0.00
2
0.000
0.00
19.1
0.00
8
0.000
0.00
19.8
0.00
6
0.000
0.00
21.1
0.00
4
0.000
0.00
25.0
0.00
2
0.470
1.05
20.8
0.05
8
0.000
1 0.00
22.1
0.00
6
0.000
0.00
24.5
0.00
4
0.000
1 0.00
32.0
1 0.00
2
Total Soluble Contaminant Electron Acceptor Demand Flux (Iblyrj 0.05
Initial Hydrogen Demand First Year (lb)l 21.01
Total Life -Cycle Hydrogen Demand (lb)l 99.16
5. Design Factors and Total Hydrogen Demand
Microbial Efficiency Uncertainty Factor 2X - 5X
Methane and Solid -Phase Electron Acceptor Uncertainly 2X - 5X
Remedial Design Safety Factor (e.g., Substrate Leaving Reaction Zone) 1X - 2X
SOLUBLE SUBSTRATE DESIGN FACTOR: 5.0
HRC DESIGN FACTOR: 0.0
SLOW RELEASE EDIBLE OIL DESIGN FACTOR: 20.0
A-2
103 CMIP App A injection.As 1232008

TABLE A-2
SOURCE AREA INJECTION PROTOCOL
SWMU-103
FLIRT RRAL7L]- Naurr" CAIMIANA
Substrate
Molecular Formula
Substrate
Molecular
weight
mlmole
Moles of Hydrogen
Produced per Mole
of Substrate
Ratio of Hydrogen
Produced to
Substrata mf
P&P Manual Appendix
C
Lactic Add (asslalling 100%)
CA03
90.1
15
0.3357
2
Molasses (assuming 100% sucrose)
C12H22011
342
15
0.0883
8
Fructose (assuming 100%)
C61-11206
180
8
0.0895
4
Ethanol (assuming 100%)
C21-1a0
46.1
2
0.0875
2
G39HW039
956,
24
0.0506
26
1.1nolsic Acid (Soybean Oil, Com ON, Cotton Oil)
CI&I17202
281
12
0.0862
16
Table A-3
Estimated Substrate Requirements for
Hydrogen Demand in Table 1, Area 1
r1^alnn I Ifa /umaretr 1a
Substrate
Design Factor
Pure Substrate Mass
Required to Fulfill
Hydrogen Demand
(pounds)
Substrate Product
Required to FuMH
Hydrogen Demand
Rds
Substrate Mass
Required to Fulfill
Hydrogen Demand
(milligrams)
Effective Substrate
Concentration
m
Lactic Add
0.0
0
0
0.00E+00
0
Sodium Lactats Product t solution)
6.0
1477
IA2
1.12E+09
97
Molasses 60% sucrose by weight)
0.0
0
0
0.00E+00
0
Fructose Product es 80% fructose by weight)
0.0
0
0
0.00E+00
0
Ethanol Product ass 80% ethanol by weight)
0.0
.0
0
0.00E+00
0
HR assumes 40% lactic add and 40% glyqW by weight)
0.0
0
0
O.00E+00
0
1-1ndeic Add (Soybean ON, Corn Oil, Cotton Oil
0.0
0
0
0.00E+00
0
CommaroW Voostable Off Emulsion Product 00% oil by weight)
20.0
22,996
38.326
1.74E+10
1 506
MOTES: Sodium Laoute rrOtluet
1. Assumes sodium lactate product is 60 percent sodium lactate by weight.
2. Molecular weight or sodium lactate (CFrCHOWCOONa) - 112.06.
3. Molecular weight of lactic Acid (CsHe03) = 90.08.
4. Therefore, sodium lactate product yields 48.4 (0.60 x (9o.08/112.06)) percent by weight lactic acid.
103 CMIP AVW A [e-mail] A - 3
U2=008

SOURCE AREA INJECTION PROTOCOL
SWMU-103
FORT BRAGG, NORTH CAROLINA
Injection Points I Subs
Injection Injection Emulsion Product 50% oil by !!eight)
Well Interval I Spacing Volume I Soybean OilLactate
I
Fv
Total Volume Estimated Injection
BuRering MakeupWater+ Injection ERetrive Radius of Time
A enl Water Substrate Substrate Interval Porosity Influence at3gpm
S I
Final Percent Substrate by Weight: 7.5% Final Lactic Add Concentration: 03 grams/liter Percent Oil by Volume in Emulsion: 73%
Final Percent Water by Weight: 92.5% Final Oil Concentration: 68.2 Zramstliter
EFFECTIVE TREATMENT ZONE CONCENTRATIONS
Design Life (years): 10 Lactic Add Treatment Zone Concentration (mg/L): 119 Final Vegetable Oil Concentration (mg/L): 1,679
Treatment Zone Volume+ Groundwater Flux Volume 3.050310 ealons
NOTES: Sodium Lactate Product
1. Assumes WillClear sodium lactate product is 60 percent sodium lactate by weight.
2. Molecularweight of sodium Lactate (CH-CHOH-COONa) - 112.06.
3. Molecular weight of lactic Acid (WdOs)-90.08.
0. Specific gravity of WillClear Product = 1.323 @ 20 degrees Celsius.
5. Weight ofWWClear Product a 11.0 pounds per piton
6. Pounds per gallon of lactic acid in product = 1.323 x 8.331b/gal 40 x 0.60 x (90,081112.06) = 5.31 Wgal.
NOTES: Frudme Product
1. Assumes fmctose product is 80 pc=rd fmctow sugar by weighL
NOTES: Vegetable Oil Emulsion Product
I.
Assumes emulsion product is 60 percent soybean oil by weight.
2. Soybean oil is 7.8 pounds per gallon.
3. Assumes scpc.'c gravity of emubon Product is 0.96 and that emulsion product is 4 percent sodium lactate by wr
Drum
Gallons
Total
Totes Gallons
Total
Emulsion Product
Emulsion Product
1
55
14.9
1 220
3.7
Neat Soybean Oil
Neat So bean Oil
l
55
92.0
1 220
23.0
BufferAgent
Bu(ferA cm
1
55
13.5
1 220
3.4
103 CMIP App A injection.xls A - 4 123,2008

J
APPENDIX B
UNDERGROUND INJECTION PERMIT
NOTE: The Underground Injection Permit is in preparation as of the publication of this
report. Copies of the approved Underground Injection Permit will be distributed with the
next version of this report or as an addendum.

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♦ _..e Rd
c
LF�ROJECTAREA
4
`�
� 1
13.
Legend
Site Boundary
— — Housing Boundary
Fence
Street/Road
p. Rail Road
o Stream
Building
_ Wetlands
� Coordinate System: North Carolina State Plane, NAM, Feet
Feet
ri-t
400 200 0 400
GO- - Ur us
SWMU 103
'PARSONS Fort Bragg
North Carolina
NED BY:
` N BT SWMU 103 Project Area
BY
-� I LH
- 'IPROJECT NU (EDBY: ER:
AK MB
SGLE: As Shown 745446.3002
D BY: DATE. September 2007 FIGURE :
FILE: 7CI3ISIR hra902ps1fig1-3.rtotd
SIES{G!$IFtBra991s 1U-103 Final_ProjectArea.MWbdh 1011&07
l

onally left blank

finally left blank ( )

N
A/
11650
, i 0 n
Ire C-Ln
r-j
CID
-
Legend
Site Boundary
Street/Road
Rail Road
Stream
Building
I§tq. 109 i Wetlands
Roughen Streambed
Proposed Surface Water Samping Location
�4,
Coordinate System: North Carolina State Plane, NAD83, Feet
Feet
400 200 0 400
SWMU 103
Fort ort Bragg
North Carolina
IED BY.
BT SWMU 103 Surface Water Remedy
Step 1 - Roughen Streambed
LH
PROJECTNUMBER.
BY.- s— As Shown 745446.30020
?Aix DATE: FIGURE
BY: September 2007 NUMBER: 4
JD

orally left blank

i
i
n .
3� FWf( i
NN
r �fjf1
j
n
t
`j Legend
`�-
�i Site Boundary i V
�. Street(Road
Rail Road
Stream
Building
�Y%ice Wetlands
Sta 1,
I
I
1
' oordinate System: North Carolina State Plane, NADB3, Feet
Feet
+ l 400 _200� 0 _ 400
PARSONS
Fort Bragg
North Carolina
'SKJiiD BY:
BT SWMU103 Surface Water Remedy
wr,�HBr step 2 - Drop Sistattures
LHvBwEaSuuBEe:
As Shawn 745446.30020
,iHEGI�D HY: BCFLE: .-
K
''-_� - �• {�I�jDBIYTiIfD BYn D"�: September -2o07_ �� A: 5
" (, JD F2E: Xi6IB{fl�.cag�Hl8pSlbgl-3.rmD
i
i
i

S2 Air Spargir
within Baseflow
0+
S1
-103_SourceAT­PilotTest.mxd lxh 10/15,/07
S4
Legend
Site Boundary
Street/Road
AA Rail Road
Stream
P Building
Wetlands
(3) Proposed Surface Water Sarnping Location
- Pilot Test A
Pilot Test B
FIGURE 6
SWMU 103 Surface Water Remedy
Step 3 - Pilot Tests
Fort Bragg, NC. .
PARSONS�
Denver, Colorado-...

This page intentionally left blank

base flow alved over flow culvert over flow calved
upstream entrances to culverts
v �baM a (plywood slabifted with soMbaggirKj)
mat

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Plan view
Section view
'T •
gravel filter pack
(pea gravel)
ma
150 gpm conduit
cover
low water
level switch
submersible pump
corrugated metal
culvert material
slotted screen

This page intentionally left blank

control valves ----
steel piping with 118"
holes at 2" seperation
103 Map Roures.cdr ma 10/15/07 Pp 10

base flow culvert over flow culvert over flow culvert
upstream entrances to culverts
downstream exit of base flow culvert
F^ be01e (plywood stablized wllh sandbagging)
ma 10/15/07 Pg 11

This page intentionally left blank

APPENDIX C
SECTION 404 NATIONWIDE PERMIT NUMBER 38
PRECONSTRUCTION NOTIFICATION

OF
Pre -Construction Notification (PCN) Application. Form
For Section 404 and/or Section 10 Nationwide, Regional and General Permits, Section 401
General Water Quality Certifications, and.Riparian Buffer and Watershed Buffer Rules
This form is to be used for projects qualifying for any of the U.S. Army Corps of Engineers' (USACE)
Nationwide, Regional or' General Permits as required by Section 404 of the Clean Water Act and/or
Section 10 of the Rivers and Harbors Act, and for the North Carolina Division of Water Quality's
(DWQ) associated General 401 Water Quality Certifications. This form is also to be used for any
project requiring approval under any' Riparian Buffer Rules implemented by the N.C. Division of Water
Quality. This form should not be used if you are requesting an Individual 404 Permit or Individual 401
Water Quality Certification. The USACE Individual Permit application form is available online at
www.saw.usace.aKMy.mil/wetlands/Pennits.html.
The USACE is the lead regulatory agency. To review the requirements for the use of Nationwide,
Regional or General permits, and to determine which permit applies to your project, please go to the
USACE website at www.saw.usace.army.mil/wetlands/index.html, or contact one of ,the field offices
listed on page 3 of this application. The website also lists the responsible project manager for each
county in North Carolina and provides additional information regarding the identification and regulation
of wetlands and waters of the U.S.
The DWQ issues a corresponding Certification (General or Individual), andcannot tell the applicant
which 401 Certification will apply until the 404 Permit type has been determined by the USACE.
Applicants are encouraged to visit DWQ's 401/Wetlands Unit. website at
http://h2o.enr.state.nc.us/ncwetlands to read about current requirements for the 401 Water Quality
Certification Program and to determine whether or not Riparian Buffer Rules are applicable. The
applicant is also advised to read the full text of the General Certification (GC) matching the specific 404
Permit requested. In some cases, written approval for General Certifications is not required, provided
that the applicant adheres to all conditions of the GC. Applicants lacking access to the internet should
contact DWQ's Central Office in Raleigh at [phone].
Trout Waters Coordination - Special coordination with the North Carolina Wildlife Resources
Commission (NCWRC) is required , for projects occurring in any of North Carolina's twenty-five
counties that contain trout waters. In such cases, the applicant should contact the appropriate NCWRC
regional coordinator (listed by county on page 4 of this application) prior to submittal of the application.
Page 1 of 12

Coastal Area Management Act (CAMA) Coordination - If the project occurs in any of North Carolina's
twenty coastal counties (listed on page 4) the applicant should contact the .North Carolina Division of
Coastal Management (DCM). DCM will determine whether or not the project is within a designated
Area of Environmental Concern, in which case DCM will act as the lead permitting agency. In such
cases, DCM will require a CAMA Permit and will coordinate the 404/401 Permits.
The applicant may also choose to coordinate with the United States Fish and Wildlife Service to ensure
that the proposed project will have no impact upon any endangered or threatened species or critical
habitat as regulated by the Endangered Species Act, and the State Historic Preservation Office, North
Carolina Department of Cultural Resources to ensure that the proposed project will have no impact upon
any properties listed or eligible for listing on the National Register of Historic Places. Compliance with
these regulations is required to be eligible for any Department of the Army permit. The addresses for
both agencies are listed on page 3 of this application.
USACE Permits - Submit one copy of this form, along with supporting narratives, maps, data forms,
photos, etc. to the applicable USACE Regulatory Field Office. Upon receipt of an application, the
USACE will determine if the application is complete as soon as possible, not to exceed 30 days. This
PCN form is designed for the convenience of the applicant to address information needs for all USACE
Nationwide, Regional or General permits, as well as information required for State authorizations,
certifications, and coordination. Fully providing the information requested on this form will result in a
complete application for any of the USACE Nationwide, Regional or General permits. To review the
minimum amount of information that must be provided for a complete PCN for each USACE
Nationwide permit, see Condition 13, 67 Fed. Reg. 2090 (Jan. 15, 2002), available at
http://www.usace.army.mil/inet/functions/cw/cecwo/reg/2002nwps.pdf. Processing times vary by
permit and begin once the application has been determined to be complete. Please contact the
appropriate regulatory field office for specific answers to permit processing periods.
401 Water Quality Certification or Buffer Rules - All information is required unless otherwise stated
as optional. Incomplete applications will be returned. Submit seven collated copies of all' USACE
Permit materials to the Division of Water Quality, 401/Wetlands Unit, 1650 Mail Service Center,
Raleigh, NC, 27699-1650. If written approval is required or specifically requested for a 401
Certification, then a non-refundable application fee is required. In brief, if project impacts include less
than one acre of cumulative wetland/water impacts and less than 150 feet cumulative impacts to
streams, then a fee of $200 is required. If either of these thresholds is exceeded, then a fee of $475 is
required. A check made out to the North Carolina Division of Water Quality, with the specific name of
the project or applicant identified, should be stapled to .the front of the application package. For more
information, see the DWQ website at http://h2o.ehnr.state.nc.us/ncwetlands/fees.html. The fee must be
attached with the application unless the applicant is a federal agency in which case the check may be
issued from a separate office. In such cases, the project must be identifiable on the U.S. Treasury check
so that it can be credited to the appropriate project. If written approval is sought solely for Buffer Rules,
the application fee does not apply, and the applicant should clearly state (in a cover letter) that only
Buffer Rule approval is sought in writing. Wetlands or waters of the U.S. may not be impacted prior to
issuance or waiver of a Section 401 Water Quality Certification. Upon receipt of a complete application
for a 401 Certification, the Division of Water Quality has 60 days to prepare a written response to the
applicant. This may include a 401 Certification, an on -hold letter pending receipt of additional
requested information, or denial.
Page 2 of 12

US Army Corps Of Engineers Field Offices and County Coverage
Asheville Regulatory Field Office
Alexander
Caldwell
Haywood
McDowell
US Army Corps of Engineers
Alleghany
Catawba
Henderson
Mecklenburg
151 Patton Avenue
Ashe
Cherokee
Iredell
Mitchell
Room 208
Avery
Clay
Jackson
Polk
Asheville, NC 28801-5006
Buncombe
Cleveland
Lincoln
Rowan
Telephone: [phone]
Burke
Gaston
Macon
Rutherford
Fax: [phone]
Cabarrus
Graham
Madison
Stanley
Raleigh Regulatory Field Office
Alamance
Franklin
Nash
Surry
US Army Corps Of Engineers
Caswell
Forsyth
Northampton
Vance
6508 Falls of the Neuse Road
Chatham
Granville
Orange
Wake
Suite 120
Davidson
Guilford
Person
Warren
Raleigh, NC 27615
Davie
Halifax
Randolph
Wilkes
Telephone: [phone]
Durham
Johnston
Rockingham
Wilson
Fax: [phone]
Edgecombe
Lee
Stokes
Yadkin
Washington Regulatory Field Office
US Army Corps Of Engineers
Post Office Box 1000
Washington, NC 27889-1000 , .
Telephone: [phone]
Fax: [phone]
Wilmington Regulatory Field Office
US Army Corps Of Engineers
Post Office Box 1890
Wilmington, NC 28402-1890
Telephone: [phone]
Fax: [phone]
Division of Water Quality
401 Wetlands Unit
1650 Mail Service Center
Raleigh, NC 27699-1650
Telephone: [phone]
Fax: [phone]
Beaufort
Currituck
Jones
Bertie
Dare
Lenoir
Camden
Gates
Martin
Carteret*
Green
Pamlico
Chowan-
Hertford
Pasquotank
Craven
Hyde
Perquimans
Anson
Duplin
Onslow
Bladen
Harnett
Pender
Brunswick
Hoke
Richmond
Carteret
Montgomery
Robeson
Columbus
Moore
Sampson
Cumberland
New Hanover
Scotland
North Carolina State Agencies
Division of Water Quality
Ecosystem Enhancement Program
1652 Mail Service Center
Raleigh, NC 27699-1652
Telephone: [phone]
Fax: [phone]
Pitt ..
Tyrrell
Washington
Wayne
Swain
Transylvania
Union
Watauga
Yancey
*Croatan National Forest Only
State Historic Preservation Office
Department Of Cultural Resources
4617 Mail Service Center
Raleigh, NC 27699-4617
Telephone: [phone]
-Fax: [phone]
US Fish and Wildlife Service / National Marine Fisheries Service
US Fish and Wildlife Service US Fish and Wildlife Service National Marine Fisheries Service
Raleigh Field Office Asheville Field Office Habitat Conservation Division
Post Office Box 33726 . 160 Zillicoa Street Pivers Island
Raleigh, NC 27636-3726 Asheville, NC 28801 Beaufort, NC 28516
Telephone: [phone] Telephone: [phone] Telephone: [phone]
Page 3 of 12

Division of Coastal Management
1638 Mail Service Center
Raleigh, NC 27699-1638
Telephone: [phone]
Fax: [phone]
Western Piedmont Region Coordinator
3855 Idlewild Road
Kernersville, NC 27284-9180
Telephone: [phone]
Mountain Region Coordinator
20830 Great Smoky Mtn. Expressway
Waynesville, NC 28786
Telephone: [phone]
Fax: [phone]
CAMA and NC Coastal Counties
Beaufort
Chowan
Hertford
Pasquotank
Bertie
Craven
Hyde
Pender
Brunswick
Currituck
New Hanover
Perquimans
Camden
Dare
Onslow
Tyrrell
Carteret
Gates
Pamlico
Washington
NCWRC and NC Trout Counties
Alleghany
Caldwell
Ashe
Mitchell
Avery
Stokes
Burke
Surry
Buncombe
Henderson
Cherokee
Jackson
Clay
Macon
Graham
Madison
Haywood
McDowell
Watauga
Wilkes
Polk
Rutherford
Swain
Transylvania
Yancey -
n
APPLICATION FORM BEGINS ON PAGE 5. PLEASE DO NOT SUBMIT PAGES 1 - 4.
Page 4 of 12

Office Use Only: Form Version March 05
USACE Action ID No. DWQ No.
(If any particular item is not applicable to this project, please enter "Not Applicable" or "N/A".)
I. Processing
1. Check all of the approval(s) requested for this project:
X Section 404 Permit ❑ Riparian or Watershed Buffer Rules
❑ Section 10 Permit ❑. Isolated Wetland Permit from DWQ
❑ 401 Water Quality Certification ❑ Express 401 Water Quality Certification
2. Nationwide, Regional or General Permit Number(s) Requested: 38
3. If this notification is solely a courtesy copy because written approval for the 401 Certification
is not required, check here: ❑
4. If payment into the North Carolina Ecosystem Enhancement Program (NCEEP) is proposed
for mitigation of impacts, attach the acceptance letter from NCEEP, complete section VIII,
and check here: ❑
5. If your project is located in any of North Carolina's twenty coastal counties (listed on page
4), and the project is within a North Carolina Division of Coastal Management Area of
Environmental Concern (see the top of page 2 for further details), check here: ❑
II. Applicant Information
1. Owner/Applicant Information
Name: Directorate of Public Works
Mailing Address: ATTN: IMSE-BRG-PWE
2175 ReillyRoad. Sto,QA
Fort Bragg, NC 28310
Telephone Number: 910-396-7432 Fax Number: 910-396-4188
E-mail Address: steven.harrissr(a,us.armymil _jason.adcockaus.army.mil
2. Agent/Consultant Information (A signed and dated copy of the Agent Authorization letter
must be attached if the Agent has signatory authority for the owner/applicant.)
Name:
Company Affiliation:
Mailing Address:
Telephone Number. Fax Number.
E-mail Address:
Page 5 of 12

III. Project Information
Attach a vicinity map clearly showing the location of the property with respect to local
landmarks such as towns, rivers, and roads. Also provide a detailed site plan showing property
boundaries and development plans in relation to surrounding properties. Both the vicinity map
and site plan must include a scale and north arrow. The specific footprints of all buildings;
impervious surfaces, or other facilities must be included. If possible, -the maps and plans should
include the appropriate USGS Topographic Quad Map and NRCS Soil Survey with the property
boundaries outlined. Plan drawings, or other maps may be included at the applicant's discretion,
so long as the property is clearly defined. For administrative and distribution purposes, the
USACE requires information to be submitted on sheets no larger than 11 by 17-inch format;
however, DWQ may accept paperwork of any size. DWQ prefers full-size construction
drawings rather than a sequential sheet version of the full-size plans. If full-size plans are
reduced to a small scale such that the final version is illegible, the applicant will be informed that
the project has been placed on hold until decipherable maps are provided.
1. Name of project: Fort Bragg — SWMU 103 surface water remediation
2. T.I.P. Project Number or State Project Number (NCDOT Only): Not applicable
3. Property Identification Number (Tax PIN): Not applicable; federal property
4. Location
County: Cumberland Nearest Town: Fayetteville
Subdivision name (include phase/lot number): Fort Bragg
Directions to site (include road numbers/names, landmarks, etc.): Beaver Creek and
Holbrook Tributary near Holbrook Elementary School, Fort Bragg.
5. Site coordinates (For linear projects, such as a road or utility line, attach a sheet that
separately lists the coordinates for each crossing of a distinct waterbody.)
Decimal Degrees (6 digits minimum): 35.135553 ON 78.975561 °W
6. Property size (acres): 3000 ft of stream x 10 ft = 0.7 acres
7. Name of nearest receiving body of water: Little Rock Fish Creek / Rockfish Creek
8. River Basin: Cape Fear
(Note — this must be one of North Carolina's seventeen designated major river basins. The
River Basin map is available at http://h2o.enr.state.nc.us/admin/maps/.)
9. Describe the existing conditions on the site and general land use in the vicinity of the project
at the time of this application: Site is entirely on Fort Bragg. Nearest land uses include
residential (post housing) and undeveloped land.
Page 6 of 12

10. Describe the overall project in detail, including the type of equipment to be used:
Please see attached sheet. i
11. Explain the purpose of the proposed work: Chlorinated solvents have contaminated
groundwater, which is upwelling into nearby streams. The puroose of this project is to
reduce contaminant concentrations in surface water to meet North Carolina surface standards.
IV. Prior Project History
If jurisdictional determinations and/or permits have been requested and/or obtained for this
project (including all prior phases of the same subdivision) in the past, please explain. Include
the USACE Action ID Number, DWQ Project Number, application date, and date permits and
certifications were issued or withdrawn. Provide photocopies of previously issued permits,
certifications or other useful information. Describe previously approved wetland, stream and
buffer impacts, along with associated mitigation (where applicable). If this is a NCDOT project,
list and, describe permits issued for prior segments of the same T.I.P. project, along with
construction schedules. None.
V. Future Project Plans
r
Are any future permit requests anticipated for this project? If so, describe the anticipated work,
and provide justification for the exclusion of this work from the current application.
Not applicable.
VI. Proposed Impacts to Waters of the United States/Waters of the State
It is the applicant's (or agent's) responsibility to 'determine, delineate and map all impacts to
wetlands,. open water, and, stream channels associated with the project. Each impact must be
listed separately in the tables below (e.g., culvert installation should be listed separately from
riprap dissipater pads). Be sure to indicate if an impact is temporary. All proposed impacts,
permanent and temporary, must be listed, and must be labeled and clearly identifiable on an
accompanying site plan. All wetlands and waters, and all streams (intermittent and perennial)
should be shown on a delineation map, whether or not impacts are proposed to these systems.
Wetland and stream evaluation and delineation forms should be included as, appropriate.
Photographs may be included at the applicant's discretion. If this proposed impact is strictly for
wetland or stream mitigation, list and describe the impact in Section VIR below. If additional
space is needed for listing or description, please attach a separate sheet.
1. Provide a written description of the proposed impacts: Please see attached description.
Page 7 of 12

2. Individually list wetland impacts. Types of impacts include, but are not limited to
mechanized clearing, grading, fill, excavation, flooding, ditching/drainage, etc. For dams,
sep ely list impacts due to both structure and flooding.
Wetland Impact
Site Number
(indicate on map)
!
Type of Impact
Type of Wetland
(e.g., forested, marsh,
herbaceous, bog, etc.)
Located within
100-year
Floodplain
es/no
Distance to
Nearest
Stream
linear feet
Area of
Impact
(acres)
Total Wetland Impact (acres)
0
3. List the total acreage (estimated) of all existing wetlands on the property: None
4. Individually list all intermittent and perennial stream impacts. Be`sure to identify temporary
impacts. Stream impacts include, but are not limited to placement of fill or culverts, dam
construction, flooding, relocation, stabilization activities (e.g., cement walls, rip -rap, crib
walls, gabions, etc.), excavation, ditching/straightening, etc. If stream relocation is proposed,
plans and profiles showing the- linear footprint for both the original and relocated streams
must be included. To calculate acreage, multiply length X width, then divide by 43,560.
Stream Impact
Perennial
Average
Impact
Area of
Number
Stream Name
Type of Impact
t?
Intermittent.
Stream Width
Length
Impact
indicate on ma
Before Impact
linear feet
acres
I
Holbrook
Boulders in streambed
4
300
0.028
Tributary,
Holbrook
Flooding (<1.5 ft)"
2
Tributary and
behind Drop Structures
4
1420
0.130
Beaver Creek
Baseflow pumped to
Holbrook
Beaver Pond and
3
Tributary
eliminated from culvert
4
307
0.028
and 100 ft of existing
4
Holbrook
Air sparge (flooding in
4
200
0.018
Tributary
culvert)
Total Stream Impact (by length and acreage)
2227
0.204
5. Individually list all open water impacts (including lakes, ponds, estuaries, sounds, Atlantic
Ocean and any other water of the U.S.). Open water impacts include, but are not limited to
fill, excavation, dredging, flooding, drainage, bulkheads, etc.
Open Water Impact
Site Number
indicate on ma
Name of Waterbody
(if applicable)
Type of Impact
Type of Waterbody
(lake, pond, estuary, sound, bay,
ocean etc.)
Area of
Impact
(acres
Total Open Water Impact (acres)
0
Page 8 of 12

6. List the cumulative impact to all Waters of the U.S. resulting from the project:
Stream Impact (acres):
0.204
Wetland Impact (acres):
0
Open Water Impact (acres):
0
Total Impact to Waters of the U.S. (acres)
0.204
Total Stream Impact linear feet):
2227
7. Isolated Waters
Do any isolated waters exist on the property? ❑ Yes X No
Describe all impacts to isolated waters, and include the type of water (wetland or stream) and
the size of the proposed impact (acres or linear feet). Please note that this section only
applies to waters that have specifically been determined to be isolated by the USACE.
8. Pond Creation
If construction of a pond is proposed, associated wetland and stream impacts should be
included above in the wetland and stream impact sections. Also, the proposed pond should
be described here and illustrated on any maps included with this application.
Pond to be created in (check all that apply): ❑ uplands [� stream ❑ wetlands
Describe the method of construction (e.g., dam/embankment,. excavation, installation of
draw -down valve or spillway, etc.):
Proposed use or purpose of pond (e.g., livestock watering, irrigation, aesthetic, trout pond,
local stormwater requirement, etc.):
Current land use in the vicinity of the pond:
Size of watershed draining to pond: Expected pond surface area:
VII. Impact Justification (Avoidance and Minimization)
Specifically describe measures taken to avoid the proposed impacts. It may be useful to provide
information related to site constraints such as. topography, building ordinances, accessibility, and
financial viability of the project. The applicant may attach drawings of alternative, lower -impact
site layouts, and explain why these design options were not feasible. Also discuss how impacts
were minimized once the desired site plan was developed. If applicable, discuss construction
techniques to be followed during construction to reduce impacts. Please see attached
justification.
VIII. Mitigation
DWQ • In accordance with 1 SA NCAC 2H .0500, mitigation may be required by the NC
Division of Water Quality for projects involving greater than or equal to one acre of impacts to
freshwater wetlands or greater than or equal to 150 linear feet of total impacts to perennial
streams.
Page 9 of 12

USACE — In accordance with the Final Notice of Issuance and Modification of Nationwide
Permits, published in the Federal Register on January 15, 2002, mitigation will be required when
necessary to ensure that adverse effects to the aquatic environment are minimal. Factors
including size and type of proposed impact and function and relative value of the impacted
aquatic resource will be considered in. determining acceptability of appropriate and practicable
mitigation as proposed. Examples of mitigation that may be appropriate and practicable include,
but are not limited to: reducing the size of the project; establishing and maintaining wetland
and/or upland vegetated buffers to protect open waters such as streams; and replacing losses of
aquatic resource functions and values by creating, restoring, enhancing, or preserving similar
functions and values, preferable in the same watershed.
If mitigation is required for this project, a copy of the mitigation plan must be attached in order
for USACE or DWQ to consider the application complete for processing. Any application
lacking a required mitigation plan or NCEEP concurrence shall be placed on hold as incomplete.
An applicant may also choose to review the current guidelines for stream restoration in DWQ's
Draft Technical Guide for Stream Work in North Carolina, available at
htti)://h2o.enr.state.nc.us/ncwetlands/stn-nizide.html.
1. Provide a brief description of the proposed mitigation plan. The description should provide
as much information as possible, including, but not limited to: site location (attach directions
and/or map, if offsite), affected stream and river basin, type and amount (acreage/linear feet)
of mitigation proposed (restoration, enhancement, creation, or preservation), a plan view,
preservation mechanism (e.g., deed restrictions, conservation easement, etc.), and a
description of the current site conditions and proposed method of construction. Please attach
a separate sheet if more space is needed.
No mitigation is planned. Actions are intended to restore quality of impacted streams.
2. Mitigation may also be made by payment into the North Carolina Ecosystem Enhancement
Program (NCEEP). Please note it is the applicant's responsibility to contact the NCEEP at
[phone] to determine availability, and written approval from the NCEEP indicating
that they are will to accept payment for the mitigation must be attached to this form. For
additional information regarding the application process for the NCEEP, check the NCEEP
website at http://h2o.enr.state.nc.us/wrp/index.htm. If use of the NCEEP is proposed, please
check the appropriate box on page five and provide the following information:
Amount of stream mitigation requested (linear feet): Not applicable
Amount of buffer mitigation requested (square feet): Not applicable
Amount of Riparian wetland mitigation requested (acres): Not applicable
Amount of Non -riparian wetland mitigation requested (acres): Not applicable
Amount of Coastal wetland mitigation requested (acres): Not applicable
Page 10 of 12

IX. Environmental Documentation (required by DWQ)
1. Does the project involve an, expenditure of public (federal/state/local) funds or the use of
public (federal/state) land? Yes X No ❑
2. If yes, does the -project require preparation of an environmental document pursuant to the
requirements of the National or North Carolina Environmental Policy Act (NEPA/SEPA)?
Note: If you are not sure whether a ` NEPA/SEPA document is required, call the SEPA
coordinator at [phone] to review current thresholds for environmental documentation.
Yes ❑ No X
3. If yes, has the document review been finalized by the State Clearinghouse? If so, please
attach a copy of the NEPA or SEPA final approval letter. Yes ❑ No ❑
X. Proposed Impacts on Riparian and Watershed Buffers (required by DWQ)-
It is the applicant's (or agent's) responsibility to determine, delineate and map all impacts to
required state and local buffers associated with the project. The applicant must also provide
justification for these impacts in Section VII above: All proposed impacts must be listed herein,
and must be clearly identifiable on the accompanying site plan. All buffers must be shown on a
map, whether or not impacts are proposed to the buffers. Correspondence from the DWQ
Regional- Office may be included as appropriate. Photographs may also be included at the
J
applicant's discretion.
1. Will the project impact protected riparian buffers identified within 15A NCAC 2B .0233
(Meuse), 15A NCAC 2B .0259 (Tar -Pamlico), 15A NCAC 02B .0243 (Catawba) 15A NCAC
2B .0250 (Randleman Rules and Water Supply -Buffer Requirements), or other (please
identify, )? Yes ❑ No X
2.
If "yes", identify the square feet and acreage of impact to each zone of the riparian buffers.
If buffer mitigation is required calculate the required amount of mitigation by applying the
bu ffer multipliers.
Zone'
Impact
ware feet
Multiplier
p
Required
Mitigation
I
3 (2 for Catawba)
2
1.5
Total
• Zone I extends out 30 feet perpendicular from the top of the near bank of channel; Zone 2 extends an
additiona120 feet from the edge of Zone 1.
3. If buffer mitigation is required, please discuss what type of mitigation is proposed (i.e.,
Donation of Property, Riparian Buffer Restoration / Enhancement, or . Payment into the
Riparian Buffer Restoration Fund). Please attach all appropriate information as identified
within 1 SA NCAC 2B .0242 or .0244, or .0260.
Page 11 of 12

XI. Stormwater (required by DWQ)
Describe impervious acreage (existing and proposed) versus total acreage on the site. Discuss
stormwater controls proposed in order to protect surface waters and wetlands downstream from
the property. If percent impervious surface exceeds 20%, please provide calculations
demonstrating total proposed impervious level. No change in impervious acreage.
XII. Sewage Disposal (required by DWQ)
Clearly detail the ultimate treatment methods and disposition (non -discharge or discharge) of
wastewater generated from the proposed project, or available capacity of the subject facility.
Not applicable.
XIII. ,Violations (required by DWQ)
Is this site in violation of DWQ Wetland Rules (15A NCAC 2H .0500) or any Buffer Rules?
Yes ❑ No X
Is this an after -the -fact permit application? Yes ❑ No X
XIV. Cumulative Impacts (required by DWQ)
Will this project (based on past and reasonably anticipated future impacts) result in additional
development, which could impact nearby downstream water quality? Yes ❑ No X
If yes, please submit a qualitative or quantitative cumulative impact analysis in accordance with
the most recent North Carolina Division of Water Quality policy posted on our website at
htW://h2o.enr.state.nc.us/ncwetlands. If no, please provide a short narrative description: This
proiect is intended to clean up contamination from Past releases. No changes to land -use or land
development are expected from these proposed actions.
XV. Other Circumstances (Optional):
It is the applicant's responsibility to submit the application sufficiently in advance of desired
construction dates to allow processing time for these permits. However, an applicant may
choose to list constraints associated with construction or sequencing that may impose limits on
work schedules (e.g., draw -down schedules for lakes, dates associated with Endangered and
Threatened Species, accessibility problems, or other issues outside of the applicant's control).
l
Applicant/Agent's Signature Date
(Agent's signature is valid only if an authorization letter from the applicant is provided.)
Page 12 of 12

/ Additional Information to support PCN Application for Stream Remediation at
SWMU 103, Fort Bragg, North Carolina.
M. Project Information
10. Describe the overall project in detail,`including"the type of equipment to be used:
The project area includes Beaver Creek - and Holbrook Tributary on Fort Bragg
between Knox Street and Honeycutt Road. Figure 1 shows the project area as well as
nearby surrounding wetlands. There are no designated wetlands within the project area.
Figure 2 provides a more detailed view of the project area, and Figure 3 provides a plan -
profile view of the impacted reaches of Beaver Creek and Holbrook Tributary in their
current condition.
This project is one element of clean-up of Fort Bragg Solid Waste Management Unit
(SWMU) 103 under the Resource Conservation and Recovery Act (RCRA). The goal of
the project is to use engineered aeration/volatilization systems to remove 1,1,2,2-
tetrachloroethane (1,1,2,2-TeCA) from Holbrook Tributary and Beaver Creek so that the
North Carolina surface water standard of 4 µg/L is met in Beaver Creek at the point that
Beaver Creek flows under Knox Street. The need for clean-up, and the selection of the
clean-up alternative are "detailed in the following reports:
SAIC (Science Applications International Corporation) 2004a. Site Conceptual Model
Report for the Former Mallonee Village Gas Station and -Vicinity that includes
- SWMUs 4 and 18 and SWMU S at Fort Bragg, North Carolina. September 2004.
SAIC 2004b. RCRA Facility Investigation for the Former Mallonee Village Gas Station
SWMU 103 at Fort Bragg, North Carolina. September 2004.
Parsons 2007. Final Corrective Measures Study for SWMU 103, Fort Bragg, North
Carolina. August 2007
Engineered aeration systems may be passive systems such as "roughening" the stream
bed with boulders or installing" weirs / drop structures to increase agitation and surface
area to facilitate volatilization. More complicated active approaches include mechanical
surface mixers, fountains, or air sparging systems. Active approaches require mechanical
pumping of either surface water or air.
Engineered aeration systems involve a number of technical, regulatory and safety
constraints. These include:
• Limited vertical relief. The change in elevation in the Holbrook tributary in
the vicinity of the contaminant plume is 25 feet (Honeycutt Road to Beaver
Creek). A majority of the elevation change occurs upstream of Sharp Drive.
The limited amount of vertical relief will limit the number of possible drop
structures or weirs, as well as the effectiveness of passive aeration systems
in general.
• Erosion concerns: Active aeration systems create erosion concerns. Surface
mixers generate strong currents that would require construction of a large
concrete basin, requiring substantial changes to the streambed. Other active
systems (sprayers/fountains or- air sparging) must be also configured to
prevent erosion, but solutions should be less costly.
Page 1 of 7

Additional Information to support PCN Application for Stream Remediation at
SWMU 103, Fort Bragg, North Carolina.
USACE permitting: Preliminary discussions with the USACE Wilmington
District revealed that a nationwide permit #38 will be required for minimal
remediation in the streambed. If construction is extensive a more'
comprehensive permit may be required. The goal of the USACE is for
"minimal damage" to the surface water environment..
Safety, particularly for children: Some aeration/volatilization devices will
attract the attention of children from the school and surrounding residential
areas. Some of the technologies will increase .the depth of the water in
certain areas, creating a safety hazard. Any aeration/volatilization approach
other than installing boulders will likely require limiting access with fencing.
An additional complicating factor is that most of the aeration/volatilization
technologies will have to be pilot tested to ascertain their effectiveness.
Both passive and active engineered aeration/volatilization approaches. are possible.
However, given the constraints and concerns listed above, a step -wise approach is the
most prudent course with each step being more difficult, potentially causing increased
concern from a USACE perspective of "minimal damage" and each causing more
potential safety hazards for small children.
Step 1
Three segments of the Holbrook Tributary stream bed will be roughened with
boulders or paving stones to increase turbulence, surface mixing, and volatilization
(Figure 4). The segments are:
207-ft section of Holbrook Tributary in the base flow (south -trending) culvertunder
the railroad right-of-way (Stations 17+31 to 19+36). This section will be roughened
by placing paving stones in a staggered pattern on the culvert bottom.
42-ft section of Holbrook Tributary below South Lucas Drive (Stations 20+56 to
20+98). This section will be roughened with one layer of D50 12-inch boulders or
recycled concrete.
55-ft section of Holbrook Tributary above Sharp Drive (Stations 32+24 to 32+79).
This section will be roughened with one layer of D50 12-inch boulders or recycled
concrete.
The as -built volume of each segment will depend on the characteristics of the stream
in the immediate vicinity. The segments will be constructed by small backhoe and/or
manual labor. Surface water monitoring at the compliance point (Knox Street) for one
year will determine if Step 1 is sufficient to reduce 1,1,2,2-TeCA to the surface water
standard, or if Step 2 is required. -
Step 2
If the surface water standard of 4 µg/L at Knox Street is not met by Step 1, the surface
water remediation approach will proceed to Step 2. Step 2 consists of installing sheet -
pile drop structures (similar to those that already exist in Holbrook tributary) in reaches
of Beaver Creek the Holbrook Tributary that typically have low velocity flow. The drop
structures will increase the retention time and surface area, and therefore volatilization, of
Page 2 of 7

Additional Information to support PCN Application for Stream Remediation at
SWMU 103, Fort Bragg, North Carolina.
upstream surface water, and may increase aeration and volatilization downstream. Rocks
placed below each drop structure will increase volatilization as water- impinges on the
rocks after it crests the drop structure.
Five potential locations for drop structures have bee selected (Figure 5):
• Drop structure (DS) 1 — Beaver Creek at Station 11+00 (100 ft upstream of
Knox Street)
• DS 2 — Holbrook Tributary at Station 20+56 (upstream of the railroad culvert)
• DS 3 — Holbrook Tributary at Station 25+51 (raising existing weir behind
Holbrook Elementary School).
• DS 4 — Holbrook Tributary at Station 30+10 (downstream of Sharp Drive
behind Holbrook Elementary School).
• DS 5 — Holbrook Tributary at Station 32+79 (upstream of Sharp.Drive).
Initially, the two drop structures with the greatest chance of success (DS 1 and DS 5)
will be installed. These two drop structures will be monitored for at least six months. If
these two drop structures reduce the concentration of 1,1,2,2-TeCA in surface water, drop
structures at the other three sites may be considered.
The drop structures will be designed to focus the base flow discharge (less than 200
gpm) through one or more notches in sheet piling in order to measure surface water
discharge and direct the flow onto boulders below the drop structure. The height of each
drop will be less than 18 inches above stream grade to minimize effects of the retained
surface water on the natural stream flow (e.g., excessive sedimentation, ponding), while
still creating a significant drop to increase aeration.
The drop structures will be constructed of sheet steel driven vertically into the stream
bed perpendicular to flow, and will extend across the stream channel. Each section of
sheet steel will be driven up to three feet below grade, and the width will be between the
banks of the channel. The as -built dimensions of each weir will depend on the
characteristics of the stream in the immediate vicinity. One layer of D50 124nch
boulders (probably recycled concrete) will be placed on the downstream side of each
drop structure to reduce scour and to provide an impinging surface to increase
volatilization.
Surface water monitoring at the compliance point (Knox Street) for one year will
determine if Step 2 is sufficient to reduce 1,1,2,2-TeCA to the surface water standard, or
if Step 3 is necessary.
Step 3
If Step 2 is not successful at reducing 1,1,2,2-TeCA concentrations to the surface
water standard at Knox Street, two active aeration systems will be pilot -tested (Figure 6).
Page 3 of 7

Additional Information to support PCN Application for Stream Remediation at -- _
SWNW 103, Fort Bragg, North Carolina. i
In the first pilot test, base flow from the Holbrook Tributary will be pumped from the
railroad right-of-way to Beaver Pond. At Beaver Pond, the pumped water will be sprayed
vertically to increase aeration and volatilization. In the second pilot test, an air-sparging
system will be constructed within the Holbrook Tributary base flow culvert at the railroad
right-of-way. The pilot tests would be conducted sequentially over a period of months.
Monitoring near Knox Street over time will determine the effectiveness of the pilot tests.
Aeration of base flow at Beaver Pond
The first pilot test will volatilize 1,1,2,2-TeCA by pumping base flow from the
Holbrook Tributary to Beaver Pond (on Beaver Creek), then aerating the pumped
discharge with a fountain at Beaver Pond.
There are three culverts under the railroad on Holbrook Tributary at Station 19+36.
The southernmost culvert has the lowest invert elevation and carries Holbrook Tributary
baseflow south under the railroad. The other two culverts have higher entrance
elevations and carry flood flow west under the railroad. Plywood and sandbag baffles
will be constructed across the entrances of two culverts to direct flow toward the
pumping cistern. A baffle will be constructed across the entrance to the base flow culvert
to a height of 0.83 ft above the invert. This baffle will divert base flow from Holbrook
Tributary into the northernmost culvert. A baffle will be constructed across the entrance
to the northernmost culvert from 0.83' to 1.69. The baffle on the northernmost culvert is
designed to accept up to four inches of water. If more than four inches of water are
flowing in the Holbrook Tributary, the additional. flow will be diverted to the middle and
southern culverts (Figure 7). The middle culvert will not be baffled. The purpose of
these baffles is to direct flow to the remediation system while protecting the system from
damage due to high velocity flood waters. Should this step be necessary and selected as
the final remedy, these baffles will be permanently constructed by anchoring steel plates
to the concrete headwalls.
A French drain and cistern will be installed near the downstream opening of the
northernmost culvert (Figure 8). The cistern will be constructed from 4-fft diameter metal
culvert, perforated so that water can enter through the sides. It will be approximately 4-ft
deep, and will be installed such that its top surface will rise slightly above the streambed.
The gravel pack (French drain), constructed of pea gravel, will be installed around the
cistern so that Holbrook Tributary base flow will infiltrate through the gravel pack and
screened walls of the cistern. A 150 gpm capacity submersible pump will be installed
inside the cistern. Power will be controlled by a float switch; the pumping capacity will
relate directly to the water level inside the cistern. The pump will shut down if an
insufficient amount of water exists within the cistern. During periods of high flow,
stream discharge in excess of 150 gpm will flow through the other two culverts and down
their existing stream channels until flow is high enough to overtop the remediation
culvert baffle: This design will protect the remediation system while conserving the
flood water carrying capacity of the three existing culverts.
Captured base flow will be pumped approximately 600 feet from the cistern to
Beaver Pond. High density polyethylene piping will lay on the ground surface and will
follow as direct path as possible to Beaver Pond. The pumped water will be sprayed
j
Page 4 of 7

Additional Information to support PCN Application for Stream Remediation at
SWMU 103, Fort. Bragg, North Carolina.
vertically by fountain into Beaver Pond to increase aeration and volatilization. The
hydraulic impact of this pilot test is that base flow from Holbrook Tributary will
discharge into Beaver Creek about 700 ft upstream from its current confluence.
Increased retention time within Beaver Pond will enhance volatilization and potentially
biodegradation of 1,1,2,2-TeCA. Surface water monitoring at the compliance point (Knox
Street) over time will determine if the pumping system is sufficient to reduce 1,1,2,2-
TeCA to the surface water standard.
' Air-Sparging
The second system will pilot test the efficacy of an air sparger located within the base
flow culvert of the Holbrook Tributary culvert at the railroad right-of-way. The second
-pilot test will only be conducted if the first pilot test is unsuccessful.
The air-sparging system will cover about 100 ft of the base flow culvert length with
two sections of nine sparging pipes (Figure 9). Each section will be controlled by a
separate valve. Within each section, the sparging pipes will be constructed of 50 feet
lengths of three-inch steel pipe offset two inches laterally, making the final dimension of
the air-sparging system 100 feet by 4 feet. Each sparging pipe will have 1/8-inch holes
two inches apart. The system will be powered by a 2500-cubic foot per minute (cfin)
blower located at the downstream opening of the base flow culvert.
A plywood and sandbag baffle will be constructed at the entrance and exit of the base
flow culvert. The entrance will be baffled from 0.38-ft to 1.5-ft from the bottom of the
culvert, allowing a 0.3841 interval for base flow to enter the culvert. The baffle at the
exit will rise 1.4 feet from the base, and is designed to pond water within the culvert and
increase the residence time and depth of water for sparging while protecting the system
from damage due to high velocity flood waters (Figure 10). Should this step be necessary
and selected as the final remedy, these baffles will be permanently constructed by
anchoring steel plates to the concrete headwalls.
Step 4
J
Following Step 3, the most efficient system based on pilot test data will be
implemented. Consideration will be given to life -cycle costs since the Army will be
responsible for operation and maintenance costs as long as these systems are in place,
estimated to be at least 50 years. Only one of the alternatives described in Step 3 would
be implemented at full scale. The Step 3 pilot test equipment for the alternative that is
not implemented at full scale for Step 4 would be removed.
VI. Proposed Impacts to Waters of the United States/Waters of the State
1. Provide a written description of the proposed impacts:
Note that the impact of each, step will only be realized if the previous step is
unsuccessful at meeting surface water clean up goals. Each step will be operated for
approximately one year before proceeding to the next step (if necessary).
Step 1
Page 5 of 7

Additional Information to support PCN Application for Stream Remediation at
SWMU 103, Fort Bragg, North Carolina.
The emplacement of boulders or paving stones in the streambed will not negatively
alter surface water flow. The boulders will be placed in a manner which will ensure their
stability during periods of -high discharge.
Step 2
Each drop structure would temporarily retain flow, increasing the surface area and
depth of the Holbrook Tributary upstream. However, the flooded volume would be less
than 1.5 ft in depth. Depending on location, each drop structure could back up flow for
100 to 529 ft upstream. Since the channel is relatively narrow and deep, the width of the
flooded area will not increase much beyond the current stream bed; and will remain
within the current stream channel.
Because of the low relief of each drop structure, an insignificant amount of
downstream scouring is expected. Boulders, similar to those used in Step 1, would be
placed on the downstream side of the drop structures to dissipate energy and increase
volatilization. These boulders will not negatively alter surface water flow.
Step 3
The potential impact of Step 3 pilot tests would be temporary (no more than one year
for each).
• Pilot test of pumping to Beaver Pond: A rate of discharge equivalent to base flow
within the Holbrook Tributary (-150 gpm) would be removed between the railroad
culvert entrance to the confluence with Beaver Creek. During periods of discharge
less than 150 gpm, surface water would be minimal across this segment. The
water table would not be altered significantly by pumping, and it is expected that
the streambed and its sediment would retain a significant volume of water. During
periods of discharge greater than 150 gpm, the surface water volume would exceed
the capacity of the submersible pump and the Holbrook Tributary would flow
continuously.
• Pilot test of air sparging: The exit of the Holbrook Tributary base flow culvert
would be baffled to a height of 1.4-ft above grade.. This would increase the surface
area and depth of the Holbrook Tributary in the culvert; however, the flooded
volume would be less than 1.5-ft in depth. As this volume would be retained
within the culvert, there would be no impact to the streambed. The grade of the
culvert is such that the 16 inches vertical of retained surface water would not flood
a large area of the culvert. During periods of high discharge, flow would be
unimpeded across the top of the baffle. Air will be bubbled through the water
from pipes laid in the bottom of the. culvert.
VII. Impact Justification (Avoidance and Minimization)
The Army is required to treat the contamination in Holbrook Tributary and Beaver
Creek to meet North Carolina surface water standards. The Corrective Measures Study
screened nine possible corrective action technologies to address surface water
contamination at this site. Surface water technologies, along with groundwater
technologies, were combined into three overall alternative approaches. (including two
Page 6 of 7

Additional Information to support PCN Application for Stream Remediation at
SWMU 103, Fort Bragg, North Carolina.
different alternatives for surface water) that were subjected to a detailed evaluation
according to RCRA criteria. The two alternatives, to address surface water were:
• Engineered aeration and volatilization to remove contaminants from surface water.
• Installing collection trenches to extract and treat contaminated groundwater prior
to its natural discharge to. surface water. Treated groundwater would be
discharged to the surface water channel.
The groundwater pump -and -treat alternative was rejected for multiple reasons: based
increased cost and potential exposure to hazardous chemicals; decreased short-term
effectiveness; safety concerns for residents and children at nearby Holbrook Elementary
School; and potential issues with long-term effectiveness and implementability due to
increased complexity of the solution.
Impacts to surface water for the chosen alternative, engineered aeration/volatilization,
have been minimized through implementing remedial activities in a step -wise fashion.
The lowest impact technology will be implemented first, and higher impact technologies
will only be implemented if the initial steps are unable to achieve clean-up goals.
Page 7 of 7

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APPENDIX D
FENCE SPECIFICATIONS

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USACE / NAVFAC/ AFCESA / NASA UFGS-32 3113.00 20 (July 2006)
Preparing Activity: NAVFAC Superseding
UFGS-32 3113.00 20 (April 2006)
UNIFIED FACILITIES GUIDE SPECIFICATIONS
Revised throughout - changes not indicated by CHG tags
References are in agreement with UMRL dated 19 March 2007
SECTION TABLE OF CONTENTS
DIVISION 32 - EXTERIOR IMPROVEMENTS
SECTION 32 31 13.00 20
CHAIN LINK FENCES AND GATES
07/06
PART 1 GENERAL
1.1 REFERENCES
1.2 DEFINITION
1.3 SUBMITTALS
1.4 DELIVERY, STORAGE, AND HANDLING
1.5 QUALITY ASSURANCE
1.5.1 Required Report Data
PART 2 PRODUCTS
2.1 CHAIN -LINK FENCING AND ACCESSORIES
2.1.1 Fabric
2.1.2 Gates
2.1.3 Posts and Braces
2.1.4 Fencing Accessories
2.1.5 Concrete
2.1.6 Grout
PART 3 EXECUTION
3.1 SITE PREPARATION
3.1.1 Clearing and Grading
3.1.2 Excavation
3.2 FENCE INSTALLATION
3.2.1 Post Spacing
3.2.2 Post Setting
3.2.2.1 Earth and Bedrock
3.2.3 Bracing
3.2.4 Top and Bottom Tension Wires
3.2.5 Fabric
3.3 ACCESSORIES INSTALLATION
3.3.1 Post Caps
3.3.2 Gates
3.4 GROUNDING
3.5 CLEANUP
D-1

USACE / NAVFAC / AFCESA / NASA UFGS-32 31 13.00 20 (July 2006)
Preparing Activity: NAVFAC Superseding
UFGS-32 3113.00 20 (April 2006)
UNIFIED FACILITIES GUIDE SPECIFICATIONS
Revised throughout - changes not indicated by CHG tags
References are in agreement with UMRL dated 19 March 2007
PART1 GENERAL
1.1 REFERENCES
The publications listed below form a part of this specification to the extent referenced. The
publications are referred to within the text by the basic designation only.
ASTM INTERNATIONAL (ASTM)
ASTM C 94/C 94M (2006) Standard Specification for Ready -Mixed
Concrete
U.S. GENERAL SERVICES ADMINISTRATION (GSA)
FS RR-F-191
(Rev K) Fencing, Wire and Post Metal (and
Gates, Chain -Link Fence Fabric, and
Accessories)
FS RR-F-191/1
(Rev D) Fencing, Wire and Post, Metal (Chain -
Link Fence Fabric)
FS RR-F-191/2
(Rev D) Fencing, Wire and Post, Metal (Chain -
Link Fence Gates)
FS RR-F-191/3
(Rev D) Fencing, Wire and Post, Metal (Chain -
Link Fence Posts, Top Rails and Braces)
FS RR-F-191/4
(Rev D) Fencing, Wire and Post, Metal (Chain -
Link Fence Accessories)
1.2 DEFINITION
Year 2000 compliant - means computer controlled facility components that accurately
process date and time data (including, but not limited to, calculating, comparing, and
sequencing) from, into, and between the twentieth and twenty-first centuries, and the
years 1999 and 2000 and leap year calculations.
1.3 SUBMITTALS
Government approval is required for submittals with a "G" designation; submittals not
having a "G" designation are for as information only. When used, a designation
following the "G" designation identifies the office that will review the submittal for
D-2

the Government. The following shall be submitted in accordance with Section 01 33
00 SUBMITTAL PROCEDURES:
SD-03 Product Data
Chain -link fencing components
Accessories
SD-07 Certificates
Fabric
Posts
Braces
Framing
Tension wires
Gates
SD-08 Manufacturer's Instructions
Fence
1.4 DELIVERY, STORAGE, AND HANDLING
Deliver materials to site in an undamaged condition. Store materials off the ground to
provide protection against oxidation caused by ground contact.
1.5 QUALITY ASSURANCE
1.5.1 Required Report Data
Submit reports of listing of chain -link fencing and accessories regarding weight in
grams (ounces) for zinc coating.
PART 2 PRODUCTS
2.1 CHAIN -LINK FENCING AND ACCESSORIES
FS RR-F-191 and detailed specifications as referenced and other requirements as
specified.
2.1.1 Fabric
FS RR-F-191/1; Type I, zinc -coated steel, 9 gage. Mesh size, 50 mm (2 inches).
Provide selvage knuckled at both selvages. Height of fabric, as indicated.
2.1.2 Gates
D-3

FS RR-F-191/2; Type II, double swing. Shape and size of gate frame, as
indicated. Framing and bracing members, round of steel alloy. Steel member
finish, zinc -coated. Gate frames and braces of minimum sizes listed in FS RR-F-
191/3 for each Class and Grade except that steel pipe frames shall be 48 mm
(1.90 inches) od, 3 mm (0.120 inches) minimum wall. thickness and aluminum
pipe frames and intermediate braces shall be 47.5 mm (1.869 inches) od, 1.4 kg
per meter (0.940 lb/ft) of length. Gate fabric, as specified for fencing fabric.
Coating for steel latches, stops, hinges, keepers, and accessories, galvanized.
Gate latches, hinges, stops, keepers, rollers, and other hardware items shall be
furnished as required for the operation of the gate. Special gate frames, as
indicated. Gate leaves more than 2.4 m (8 feet) wide shall have intermediate
members as necessary to provide rigid construction, free from sag or twist. Gate
leaves less than 2.4 m (8 feet) wide shall have truss rods or intermediate braces.
Attach gate fabric to gate frame in accordance with manufacturer's standards,
except that welding will not be permitted. Arrange padlocking latches to be
accessible from both sides of gate, regardless of latching arrangement.
2.1.3 Posts and Braces
FS RR-F-191/3 line, end, corner, and pull posts; Class 1, steel pipe, Grade A.
Braces; Class 1, steel pipe, Grade A, in minimum sizes listed in FS RR-F-
191/3 for each class and grade.
2.1.4 Fencing Accessories
FS RR-F-191/4. Provide wire ties constructed of the same material as the
fencing fabric.
2.1.5 Concrete
ASTM C 94/C 94M, using 19 mm (3/4 inch) maximum -size aggregate, and
having minimum compressive strength of 20 MPa (3000 psi) at 28 days.
2.1.6 Grout
Provide grout of proportions one part portland cement to three parts clean,
well -graded sand and a minimum amount of water to produce a workable mix.
PART 3 EXECUTION
3.1 SITE PREPARATION
3.1.1 Clearing and Grading
Clear fence line of trees, brush, and other obstacles to install fencing. Establish a
graded, compacted fence line prior to fencing installation. Compact fill used to
establish fence line.
3.1.2 Excavation
Excavate to dimensions indicated for concrete -embedded items, except in bedrock. If
bedrock is encountered, continue excavation to depth indicated or 450 mm (18 inches)
into bedrock, whichever is less, with a diameter in bedrock a minimum of 50 mm (2
D-4

inches) larger than outside diameter of post. Clear post holes of loose material.
Dispose of waste material, as directed.
3.2 FENCE INSTALLATION
Install fence on prepared surfaces to line and grade indicated. Install fence in
accordance with fence manufacturer's written installation instructions except as
modified herein.
3.2.1 Post Spacing
Provide line posts spaced equidistantly apart, not exceeding 3 in (10 feet) on
center. Provide gate posts spaced as necessary for size of gate openings. Do not
exceed 152 in(500 feet) on straight runs between braced posts. Provide corner or,
pull posts, with bracing in both directions, for changes in direction of 0.26 rad
(15 degrees) or more, or for abrupt changes in grade.,Provide drawings showing
location of gate, corner, end, and pull posts.
3.2.2 Post Setting
Set posts plumb: Allow concrete and grout to cure a minimum of 72 hours before
performing other work on posts.
3.2.2.1 Earth and Bedrock
Provide concrete bases of dimensions indicated except in bedrock. Compact
concrete to eliminate voids, and finish to a dome shape. In bedrock, set posts
with a minimum of 25 mm (one inch) of grout around each post. Work grout
into hole to eliminate voids, and finish to a dome shape.
3.2.3 Bracing
Brace gate, corner, end, and pull posts to nearest post with a horizontal brace
used as a compression member, placed at least 300 mm (12 inches) below top of
fence, and a diagonal truss rod and truss tightener used as a tension member.
3.2.5 Top and Bottom Tension Wires
Install top and bottom tension wires before installing chain -link fabric, and pull
wires taut. Place top and bottom tension wires within 200 mm (8 inches) of
respective fabric line.
3.2.6. Fabric
Pull fabric taut and secure fabric to top wire and bottom wire, close to both sides
of each post and at maximum intervals of 600 mm (24 inches) on center. Secure
fabric to posts using stretcher bars, ties or clips spaced 375 mm (15 inches) on
center, or by integrally weaving to integral fastening loops of end, corner, pull,
and gate posts for full length of each post. Install fabric on opposite side of posts
from area being secured. Install fabric so that bottom of fabric is 50 mm (2
inches) above ground level.
D-5

3.3 ACCESSORIES INSTALLATION
3.3.1 Post Caps
Install post caps as recommended by the manufacturer.
3.3.2 Gates
Install swing gates to swing through 3.14 rad (180 degrees) from closed to open.
3.4 GROUNDING
Fences crossed by overhead powerlines in excess of 600 volts shall be
grounded as specified in Section 26 41 01.00 10 LIGHTNING PROTECTION
SYSTEM.
Fences shall be grounded on each side of all gates, at each corner, at the
closest approach to each building located within 15 in (50 feet) of the fence,
and where the fence alignment changes more than 15 degrees. Grounding
locations shall not exceed 198 in (650 feet). Each gate panel shall be bonded
with a flexible bond strap to its gate post. Fences crossed by powerlines
of 600 volts or more shall be grounded at or near the point of crossing and
at distances not exceeding 45 in (150 feet) on each side of crossing. Ground
conductor shall consist of No. 8 AWG solid copper wire. Grounding
electrodes shall be 19 mm (3/4 inch) by 3.05 m (10 foot) long copper -clad steel
rod. Electrodes shall be driven into the earth so that the top of the
electrode is at least 152 mm (6 inches) below the grade. Where driving is
impracticable, electrodes shall be buried a minimum of 305 mm (12 inches)
deep and radially from the fence. The top of the electrode shall be not
less than 610 mm (2 feet) or more than 2.4 in (8 feet) from the fence. Ground
conductor shall be clamped to the fence and electrodes with bronze
grounding clamps to create electrical continuity between fence posts, fence
fabric, and ground rods. After installation the total resistance of fence
to ground shall not be greater than 25 ohms.
3.5 CLEANUP
Remove waste fencing materials and other debris from the station.
p

FINAL
Corrective Measures Study
for
SWMU 103
Fort- Bragg, North Carolina
Submitted To:
U.S. ARMY ENVIRONMENTAL COMMAND
Submitted By.,
PARSONS
JUN 11 2008
August 2007 � DENR-FAYEFEMLLEREGIONALURCE'

RECOVER
JUN 11
DENR-FAYETfMLE REGIONAL URCE

TABLE OF CONTENTS
Page
EXECUTIVESUMMARY...........................................................................................ES-1
SECTION 1 - INTRODUCTION....................................................................................1-1
1.1 Site Background...................................................................................................1-2
1.2 Regulatory Background.......................................................................................1-3
1.3 Scope of the Corrective Measures Study ....................................... :..................... 1-3
1.4 Corrective Measures Study Report Organization................................................1-4
SECTION 2 - SITE CHARACTERIZATION................................................................2-1
2.1 Site Overview....................................................................................................... 2-1
2.2 Topography, Physiography, and Climate.............................................................2-2
2.3 Water Supply....................................................................................................... 2-2
2.4 Site Geology......................................................................................................... 2-4
2.5 Hydrogeology...................................................................................................... 2-5
2.6 Surface Water Hydrology.................................................................................... 2-7
2.7 Site Ecology
2.8 Supplemental Investigations for the Corrective Measures Stud
2.8.1 Sentinel Wells at Holbrook Elementary School ............................ :.......... 2-9
2.8.2 Subsurface Soil and Groundwater Around the Former Heating -Oil UST
atBuilding 6-9344-A............................................................................... 2-9
2.8.3 Groundwater Sampling of Monitoring Wells at SWMU 103................2-10
2.8.4 Slug Tests............................................................................................... 2-10
2.8.5 Bench -Scale and In -Situ Pilot Study Evaluating Enhanced
Bioremediation Using Aerobic Cometabolic Mechanism ..................... 2-11
2.8.5.1 Bench -Scale Study................................................................ 2-11
2.8.5.2 In -Situ Pilot Study.................................................................2-12
2.9 Surface Water Sampling by USACE in March 2006.........................................2-15
2.10 Soil Gas Sampling in June 2006........................................................................ 2-16
2.11 Groundwater Sampling in June 2006.................................................................2-18
SECTION 3 - UPDATE OF NATURE AND EXTENT OF CONTAMINATION
AND THE SITE CONCEPTUAL MODEL ........................................... 3-1
3.1 Source of Contaminants at SWMU 103............................................................... 3-1
3.2 Soils and Geology........................................................... ... 3-2
..................................
3.3 Groundwater Hydrology...................................................................................... 3-2
3.4 Surface Water Hydrology.................................................................................... 3-3
3.5 Surface Soil.......................................................................................................... 3-3
3.6 Subsurface Soil.................................................................................................... 3-3
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TABLE OF CONTENTS (Continued)
Page
3.7
Groundwater........................................................................................................ 3-4
3.7.1 Volatile Organic Compounds.................................................................. 3-4
3.7.2 Semivolatile Organic Compounds........................................................... 3-6
3.7.3 Distribution of Groundwater Contaminants ............................................. 3-6
3.7.4 Potential Groundwater Contamination Upgradient of SWMU 103......... 3-8
3.7.5 Potential Contamination Migrating Under Beaver Creek ........................ 3-9
3.7.6 Natural Attenuation of Chlorinated Solvents in Groundwater ................ 3-9
3.8
Vapor Intrusion..................................................................................................3-10
3.8.1 Tier I Screen...........................................................................................
3-11
3.8.2 Tier II Screen.........................................................................................
3-11
3.9
Surface Water and Sediment..............................................................................
3-12
3.9.1 Surface Water.........................................................................................3-12
3.9.2 Sediment................................................................................................
3-13
3.10
Ecological Risk Assessment..............................................................................
3-13
3.11
Fate and Transport .............................................................................................
3-13
3.11.1 Soil Screening Level Evaluation............................................................
3-14
3.11.2 Natural Attenuation Modeling...............................................................
3-14
3.12
Nature and Extent of Contamination and Human Health Constituents of
PotentialConcern ................................................................................................
3-17
3.13
Development of Remedial Goal Options...........................................................
3-17
3.13.1 Groundwater Remedial Goal Options ....................................................
3-18
3.13.1.1 Potable Use RGOs................................................................
3-18
3.13.1.2 Uncertainty............................................................................3-18
3.13.2 Surface Water.........................................................................................3-19
SECTION 4 - JUSTIFICATION AND PURPOSE OF CORRECTIVE ACTION......... 4-1
4.1 Purpose.................................................................................................................4-1
4.2 Remedial Response Objectives............................................................................4-1
4.3 Identification of Remedial Levels........................................................................ 4-2
SECTION 5 - SCREENING OF CORRECTIVE ACTIONS ......................................... 5-1
5.1 Screening Criteria.................................................................................................5-1
5.1.1 Effectiveness............................................................................................ 5-1
5.1.2 Implementability...................................................................................... 5-2
5.1.3 Cost.......................................................................................................... 5-2
5.2 Evaluation of Corrective Action Technologies for Groundwater ........................ 5-2
5.2.1 No Action................................................................................................. 5-2
5.2.2 Institutional Controls............................................................................... 5-3
5.2.3 Monitored Natural Attenuation................................................................ 5-3
5.2.4 Phytoremediation..................................................................................... 5-4
5.2.5 Permeable Reactive Barrier..................................................................... 5-5
5.2.6 Groundwater'Pumping and Ex -situ Treatment of Groundwater .............. 5-6
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TABLE OF CONTENTS (Continued)
Page
5.2.7 Air Sparging............................................................................................. 5-7
5.2.8 In -Situ Chemical Oxidation..................................................................... 5-7
5.2.9 Enhanced Bioremediation Using Anaerobic Reductive Dechlorination . 5-8
5.2.10 Enhanced Bioremediation Using Aerobic Cometabolic Mechanism ...... 5-9
5.2.11 Monitoring............................................................................................. 5-10
5.3 Evaluation of Corrective Action Technologies for Surface Water .................... 5-11
5.3.1 No Action............................................................................................... 5-11
5.3.2 Institutional Controls............................................................................. 5-11
5.3.3 Ex -situ Treatment Technologies and Process Options .......................... 5-12
5.3.4 In -situ Treatment Technologies and Process Options ........................... 5-13
5.3.4.1 Aeration/Volatilization..........................................................5-13
5.3.4.2 Constructed Wetlands...::...................................................... 5-15
5.3.4.3 Biological Mats.....:............................................................... 5-16
5.3.5 Stream Segregation................................................................................5-16
5.3.6 Monitoring ............................................................................................. 5-17
5.4 Corrective Action Alternatives.......................................................................... 5-17
5.4.1 Evaluation Factors................................................................................. 5-19
5.4.2 Evaluation of Corrective Action Alternatives ........................................ 5-22
5.4.2.1 Alternative 1: MNA, Institutional Controls, Engineered
Aeration/Volatilization of Surface Water, and Monitoring.. 5-22
5.4.2.2 Alternative 2: Source Treatment using Enhanced
Bioremediation, MNA, Engineered Aeration/Volatilization of
Surface Water, Institutional Controls, and Monitoring......... 5-27
5.4.2.3 Alternative 3: Source Area Treatment using Enhanced
Bioremediation, MNA, Pump -and -Treat Contaminated
Groundwater to Protect Surface. Water, Institutional Controls,
andMonitoring...................................................................... 5-34
SECTION 6 - COMPARATIVE ANALYSIS OF ALTERNATIVES,
CONCEPTUAL DESIGN, AND IMPLEMENTATION PLAN ........... 6-1
6.1 Comparative Analysis of Corrective Actions ......................................................
6-1
6.1.1
Protection of Human Health and the Environment ..................................
6-2
6.1.2
Attainment of Media Cleanup Standards .................................................
6-3
6.1.3
Control of Source of Releases..................................................................
6-3
6.1.4
Comply with Applicable Standards for Management of Waste ..............
6-3
6.1.5
Other Factors............................................................................................
6-4
6.1.5.1 Long-term reliability and Effectiveness ..................................
6-4
6.1.5.2 Reduction in the Toxicity, Mobility, or Volume of Wastes....
6-4
6.1.5.3 Short -Term effectiveness........................................................
6-4
6.1.5.4 Implementability.....................................................................
6-5 .
6.1.5.5 Costs........................................................................................6-5
6.1.4
Selected Alternative.................................................................................
6-5 "
6.2 Conceptual Design of Selected Alternative.........................................................
6-6
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TABLE OF CONTENTS (Continued)
Page
6.2.1
Establishment of Institutional Controls ................................................... 6-6
6.2.2
Engineered AerationNolatilization for Surface Water ............................ 6-6
6.2.3
Warning Signs and Fencing..................................................................... 6-7
6.2.4
Complete Groundwater Network ......................... :................................... 6-7
6.2.5
Enhanced Bioremediation in the Source Area ......................................... 6-7
6.2.6
Monitored Natural Attenuation................................................................ 6-8
6.2.7
Monitoring...........................................................................................:... 6-8
6.2.7.1 Soil Gas.................................................................................... 6-8
6.2.7.2 Groundwater.........................................................................:..6-9
6.2.7.3 Surface Water..........................................................................6-9
6.2.8
Investigation -Derived Waste...................................................................
6-9
6.2.9
Operation and Maintenance...................................................................6-10
6.2.10
Reporting................................................................................................6-10
6.2.10.1 Periodic Progress Reports .....................................................
6-10
6.2.10.2 Corrective Action Completion Report ..................................
6-10
6.2.11
Monitoring Well and Soil Gas Monitoring Point Abandonment...........
6-10
6.3 Cost Estimate.....................................................................................................
6-10
6.4 Implementation Schedule...................................................................................
6-10
SECTION7 - REFERENCES......................................................................................... 7-1
APPENDICES
A - Boring Logs
B - Monitoring Well Construction Diagrams
C - Laboratory Analytical Data and Chain -of -Custody
D - Results of Slug Tests
E - Results of In -Situ Pilot Study at SWMU 103
F - Supplemental Investigation for SWMU 103 Conducted in Calendar Years 2005 and
2006
G - Analytical Data Sets for Subsurface and Groundwater
J - Laboratory Analytical Data and Chains -of -Custody for Sampling Conducted In
Calendar Years 2005 And 2006
K - Fate and Transport Modeling
-1V-
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TABLE OF CONTENTS (Continued)
LIST OF TABLES
No
Title
2-1
Water Levels for April 2005, SWMU 103
2-2
Summary of Horizontal Gradients, SWMU 103
2-3
Summary of Vertical Hydraulic Gradients at Well Pairs, SWMU 103
24
Monitoring Well Construction Summary for March 2005, SWMU 103
2-5
Field Parameter Measurements during Groundwater Sampling, SWMU 103
2-6
Slug Test Results for Wells at SWMU 103
2-7
Summary of Results for Bench -Scale Studies Using CL-OutTM (April 2005)'
SWMU 103
2-8
Summary of PermeOx®, CL-OutTM, and PoWater Injections Conducted during
the SWMU 103 Pilot Study
2-9
Comparison of Critical Field Parameters Collected during In -Situ Pilot Study,
SWMU 103
2-10
Summary of Results of Groundwater for Pilot Study (April — August 2005),
SWMU 103
3-1
Summary Statistics of Analytes Detected in Subsurface Soil, SWMU 103
`` 3-2
Summary Statistics of VOCs Detected in Groundwater, SWMU 103
3-3
Summary Statistics of Semivolatile Organic Compounds Detected in
Groundwater, SWMU 103
3-4
Historical groundwater VOC data support reductive dechlorination in the
SWMU 103 source area
3-5
Vapor Intrusion Tier II Screening Summary
3-6
Screening to Determine HHCOPC in Beaver Creek and the Holbrook Tributary
3-7
Comparison of SRC in Subsurface Soil to North Carolina SSLs, SWMU 103
3-8
Natural Attenuation Time to Multiple Target Groundwater Concentrations at
SWMU 103
3-9
HHCOPCs in Groundwater and Surface Water at SWMU 103
3-10
Recommended RGOs for Potable Use of Groundwater, SWMU 103
3-11
Determination of COCs and Recommended RGOs for Surface Water, SWMU
103
4-1
Recommended Remedial Levels for COCs in Groundwater and Surface Water at
SWMU 103
5-1
Evaluation of Corrective Action Technologies/Process Options for
Groundwater, SWMU 103
5-2
Evaluation of Corrective Action Technologies/Process Options for Surface
Water, SWMU 103
5-3
Cost Comparision of Remedial Alternatives for SWMU 103
5-4
Comparison of Site -wide Corrective Action Alternatives for Groundwater and
Surface Water by Evaluation Criteria
" -v-
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TABLE OF CONTENTS (CONTINUED)
LIST OF FIGURES
No. Title
1-1 Site Map and Surface Topography of SWMU 103
1-2 Locations of Former USTs and CLosure Activities at the Former Mallonee Gas
Station, SWMU 103 (Source Area)
2-1 Site Location Map for Fort Bragg Military Reservation
2-2 SWMU 103 and Nearby Property Use
2-3 Locations of Water Supply Wells at Fort Bragg, North Carolina
2-4 Clay Contour Map for SWMU 103
2-5 Generalized Relation between Geologic and Hydrologic Units at SWMU 103
2-6 Potentiometric Surface Map for Shallow Groundwater for SWMU 103 and
Vicinity (April 2005)
2-7 Potentiometric Surface Map for Deep Groundwater for SWMU 103 and vicinity
(April 2005)
2-8 Surface Water Drainage
2-9 Sentinel Wells at Holbrook Elementary School, SWMU 103
2-10 Locations of DPT Soil Borings and Monitoring Wells Around the Former
Heating -Oil USTs at SWMU 103 --�
2-11 Locations of Additional Monitoring and Injection wells for the Pilot Study at ;
SWMU 103
2-12 Surface Water Locations Collected by USACE — Savannah District in March
2006 at SWMU 103
2-13 Soil Gas Monitoring Well Network Around Holbrook Elementary School (June
2006), SWMU 103
2-14 Locations of Additional Groundwater Sampling (June 2006) at SWMU 103
3-1 1,1,2,2-Tetrachloroethane and Trichloroethene Concentrations in Deep
Groundwater in the SWMU 103 Source Area
3-2 Chemical and Biological Degradation Pathways of Chlorinated Solvents at
SWMU 103
3-3 Extent of Groundwater and Surface Water Contamination at SWMU 103
3-4 Generalized Site Conceptual Model for. SWMU 103
5-1 SWMU-103 Alternative 1 Remedy: Monitored Natural Alternation of
Groundwater, Natural or Engineered Aeration/Volatilization of Surface Water
5-2 SWMU-103 Alternative 2 Remedy: Source Area Treatment Using Enhanced
Bioremediation Natural or Engineered Aeration/Volatilization of Surface Water
5-3 SWMU-103 Alternative 3 Remedy: Source Area Treatment using Enhanced
Bioremediation, Pump -and -Treat Contaminated Ground Water to Protect
Surface Water
5-4 Ground Water Interception Trench Design
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LIST OF ACRONYMS AND ABBREVIATIONS
µg/L
microgram(s) per liter
AMSL
above mean sea level
AOC
area of concern
AT123D
Analytical Transient 1-, 2-," 3-Dimensional
bgs
below ground surface
BMP
Base Master Plan
BTEX
benzene, toluene, ethylbenzene, and xylenes
CMCOPC
contaminant migration constituents of potential concern
CMS
correctivemeasures study
cm/sec
centimeters per second
COC
contaminant of concern
COD
chemical oxygen demand
CVOC
chlorinated volatile organic compounds
CY
calendar year
DCE
dichloroethene
DNAPL
dense nonaqueous-phase liquid
DO
dissolved oxygen
DoD
Department of Defense
DPT
direct -push technology
DPW
Department of Public Works
r ECOPC
Ecological COPCs
r EPA
United States Environmental Protection Agency
OF
degrees Fahrenheit
F&T
fate and transport
ft/ft
foot per foot
gal
gallon
gpd
gallons per day
gpm
gallons per minute
HDPE
high -density polyethylene
HHCOPC
human health constituents of potential concern
HP
horsepower
HQ
hazard quotient
HSWA
Hazardous and Solid Waste Amendments
IDW
investigation -derived waste
IMAC
maximum acceptable concentration
in
inch(es)
IRP
Installation Restoration Program
ISCO
In -situ chemical oxidation
kPa
kilopascals
L
liter(s)
LNAPL
light nonaqueous-phase liquid
M
meter(s)
mg/kg
milligram(s) per kilogram
mg/L
milligram(s) per liter
Mid -Atlantic
Mid -Atlantic Associates, P.A.
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mm Hg
t
millimeters of mercury '-
MNA
monitored natural attenuation
MODFLOW
Modular Three -Dimensional Groundwater Flow Model
mph
miles per hour
MTBE
methyl tert-butyl ether
NC
North Carolina
NCAC
North Carolina Administrative Code
NCDENR
North Carolina Department of Environment and Natural Resources
NOAA
National Oceanic and Atmospheric Administration
NPDES
National Pollutant Discharge Elimination System
O&M
operations and maintenance
ORC
oxygen -releasing compound
ORP
oxidation-reduction potential
OSHA
Occupational Safety and Health Administration
OSWER
Office of Solid Waste and Environmental Response
OWS
oil/water separator
PAH
polyaromatic hydrocarbon
Parsons
Parsons Infrastructure and Technology Group, Inc.
PRB
permeable reactive barriers
PRG
preliminary remediation goal
PVC
polyvinyl chloride
RBCA
Risk -Based Corrective Action
RCRA
Resources Conservation and Recovery Act
RFI
RCRA facility investigation
RGO
remedial goal option
RRO
remedial response objective
SCM
site conceptual model
SESOIL
SEasonal Flow and Transport Model for the Unsaturated SOIL Zone
SRC
site -related constituents
SSL
soil screening levels
SVOC
semivolatile organic compound
SWMU
Solid Waste Management Unit
TCA
trichloroethane
TCE
trichloroethene
TOC
total organic carbon
UIC
Underground Injection Control
USACE
United States Army Corps of Engineers
USGS
United States Geological Survey
UST
underground storage tank
VOC
volatile organic compound
WS
water supply
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EXECUTIVE SUMMARY
A corrective measures study (CMS) was performed for the former Mallonee Village Gas
Station Solid Waste Management Unit (SWMU) 103 at the Fort Bragg Military Reservation,
North Carolina, to evaluate potential corrective actions for addressing contaminants in
groundwater and surface water. This report has been prepared by Parsons Infrastructure and
Technology Group, Inc. (hereafter referred to as Parsons) for the Army Environmental
Command under contract number W91ZLK-050D-0016, task order 0001.
The former Mallonee Village Gas Station (Building 6-9650) site is located at the corner of
Honeycutt Road and South Lucas Drive and during its operational life contained up to 10
underground storage tanks (USTs): one 13,500-gal diesel tank; one 10,000-gal gasoline tank;
two 1,000-gal heating fuel tanks, two 10,000-gal gasoline tanks; one 6,000-gal tank; one 6,000-
gal diesel tank, one waste oil tank, and one solvent tank. Closure reports were submitted for two
UST removal actions; four USTs were removed in 1996 and four were removed in 1998. A
records search at the time indicated that the waste oil and solvent tanks had been removed (date
unknown) prior to the inception of current UST regulations. Chlorinated solvents are believed to
have been released -from the solvent tank over 30 years ago and are the focus of SWMU 103.
The site was formally closed in 1998 and designated as SWMU 103 in calendar year (CY) 2000.
A Resource Conservation and Recovery Act (RCRA) facility investigation (RFI) conducted
from June 2000 through January 2003 determined the nature and extent of contamination and the
site conceptual model (SCM) for SWMU 103. The RFI concluded that a CMS was required for
SWMU 103 and supplemental investigations and bench -scale and in -situ pilot .studies were
g g
required. The supplemental investigation performed from :March through August 2005 included:
(1) the installation of four sentinel wells downgradient of the SWMU 103 site and upgradient of
Holbrook Elementary School located approximately 500 feet southeast of the SWMU 103 site,
(2) collection of groundwater samples to update the nature and extent of groundwater
contamination, (3) slug testing, and (4) performance of bench -scale treatability and in -situ pilot
studies evaluating the injection of specialized bacteria and oxygen -releasing compound (ORC)
for the treatment of contaminants in groundwater. The additional soil andgroundwater data were
used to update the nature and extent of contamination and the SCM for SWMU 103. The bench -
scale and in -situ pilot studies indicated that the specialized bacteria were effective at treating the
primary contaminant in groundwater, 1,1,2,2-tetrachloroethane. However, rebound of
contaminant levels occurred in the treatment zones due to the limited nature of the pilot study
and relatively high groundwater flow rates. Further supplemental investigations in June 2006
included soil gas and.crawlspace air samples around and under Holbrook Elementary School to
screen for vapor intrusion, and additional groundwater monitoring in existing wells.
The supplemental data collected in CY 2005 and CY 2006 did not change the conclusions of
the RFI or SCM for SWMU 103. Low concentrations of chlorinated solvents and petroleum
contaminants are present in groundwater originating from the former Mallonee Village Gas
Station. The chlorinated solvents are associated with SWMU 103, while the petroleum
compounds are associated with the petroleum USTs that are addressed under North Carolina
UST regulations. No remaining soil source was identified at SWMU 103, but diffusion from
Cape Fear clays under the former gas station is suspected to be the current continuing source of
chlorinated VOCs in groundwater. 1,1,2.,2-Tetrachloroethane and trichloroethene (TCE) are
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representative chemicals for chlorinated solvents. 1,1,2,2-Tetrachloroethane has been detected at
concentrations as high as 660 micrograms per liter (µg/L) and exceeds the North Carolina 2L
standard in 47 of 53 site wells over approximately a 92 acre area. TCE was detected as high as
78 µg/L and exceeds its North Carolina 2L standard in 31 of 53 site wells over approximately a
74 acre area. The chlorinated solvent contamination permeates the entire groundwater column
with the higher concentrations located in the deep surficial groundwater. Concentrations
generally appear to be decreasing or stable with time. Volatile organic compounds (VOCs) in
groundwater are being intercepted by Beaver Creek and the Holbrook tributary.
The following media and chemicals were identified as being of concern and requiring
evaluation of potential corrective actions in the CMS:
Groundwater (Human Health): 1,1,2,2-tetrachloroethane; chloroform; chloromethane;
tetrachloroethene; and TCE.
Surface Water: 1,1,2,2-tetrachloroethane.
The North Carolina 2L or interim maximum acceptable concentration standards were
established as the remedial levels for the groundwater COCs. The North Carolina 2L standard of
0.17, µg/L was established as the groundwater remedial level for 1,1,2,2-tetrachloroethane. The
North Carolina surface water standard of 4 µg/L was established as the remedial level for
1,1,2,2-tetrachloroethane in surface water.
The following remedial response objectives were developed for the COCs identified in
groundwater and surface water that are protective of human health and the environment:
• Prevent potential use of groundwater.
• Reduce concentrations of contaminants of concern (COCs) in groundwater to the North
Carolina 2L standards.
• Reduce potential contact and ingestion of surface water.
• Prevent contaminants in groundwater from migrating to surface water at concentrations
above the North Carolina surface water standards.
No action and five categories of corrective action process options/technologies were identified
as applicable for chlorinated solvent (primarily) and petroleum contamination in groundwater at
SWMU 103: (1) institutional controls: land- and groundwater -use restrictions and physical
barriers; (2) monitored natural attenuation (MNA); (3) ex -situ treatment technologies (i.e., pump
and treat); (4) in -situ treatment technologies (e.g., enhanced bioremediation); and (5) monitoring
(i.e., groundwater, surface water, and soil gas). No action and three categories of corrective
action process options/technologies were identified as applicable for chlorinated solvent
contamination in surface water at SWMU 103: (1) institutional controls (i.e., use restrictions and
physical barriers), (2) in -stream technologies (i.e., aeratiori/volatilization), and (3) monitoring.
The corrective action process options/technologies were screened with respect to effectiveness,
implementability, and relative cost and those process options/technologies passing the screening
were combined into the following three site -wide corrective actions for detailed analysis against
U. S. Environmental Protection Agency criteria.
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(t `5
-' Alternative 1: MNA, Engineered Aeration/Volatilization of Surface Water, Institutional
Controls, and Monitoring
• Institutional controls to prevent the use of groundwater and surface water.
• Fencing and signs along the Holbrook tributary and Beaver Creek to reduce exposure to
surface water where 1,1,2,2-tetrachloroethane exceeds surface water standards.
• MNA of groundwater contamination.
• Annual soil gas monitoring at Holbrook Elementary School. i
• Engineered, volatilization of VOCs in surface water.
• Surface water and groundwater monitoring to evaluate performance:
This alternative would require a long-term monitoring program.
Alternative 2: Source Area Treatment Using Enhanced Bioremediation, MNA,
Engineered Aeration/Volatilization of Surface Water, Institutional Controls, and
Monitoring
• Institutional controls to prevent the use of groundwater and surface water.
• Fencing and signs along the Holbrook tributary and Beaver Creek to reduce exposure to
_.' surface water where 1,1,2,2-tetrachloroethane exceeds surface water standards.
Enhanced bioremediation using anaerobic reductive dechlorination in groundwater in the
source area, which was defined as the location of the former Mallonee Village Gas
Station.
• NINA for remaining groundwater contamination.
• Engineered volatilization of VOCs in surface water.
• Annual soil gas monitoring at Holbrook Elementary School.
• Surface water and groundwater monitoring to evaluate performance.
The active portion of the Alternative 2 would treat groundwater using enhanced
bioremediation (i.e., anaerobic reductive dechlorination) in the source area, which was defined as
the immediate area of the former Mallonee Village Gas Station, with the goal to reduce
chlorinated solvent concentrations in treatment zone groundwater by approximately 90 percent.
MNA would be used to further reduce the remaining groundwater contaminants to the North
Carolina 2L standards.
Alternative 3: Source Area Treatment Using Enhanced Bioremediation, MNA, Pump -
and -Treat Contaminated Groundwater to Protect Surface Water, Institutional Controls,
and Monitoring
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• Institutional controls to prevent the use of groundwater and surface water.
• Enhanced bioremediation using anaerobic reductive dechlorination in groundwater in the
source area, which was defined as the location of the former' Mallonee Village Gas
Station.
• MNA for the remaining contaminated groundwater.
• Pump -and -treat groundwater using subsurface drains and activated carbon adsorption
treatment to prevent contaminated groundwater from discharging to surface water.
• Annual soil gas monitoring at Holbrook Elementary School.
• Long-term surface water and groundwater monitoring to evaluate performance.
Alternative 3 would use enhanced bioremediation using anaerobic reductive dechlorination to
treat groundwater in the source area as described above for Alternative 2. MNA would be used to
further reduce the remaining groundwater contaminants to the North Carolina 2L standards. A
series of subsurface drains would be used to extract enough groundwater to prevent migration of
contaminants to surface water. Extracted groundwater would be treated with activated carbon
and discharged to nearby surface water drainages. The pump -and -treat system would continue
until the combined effects of enhanced bioremediation and MNA reduce the contaminant flux
such that surface water quality will not exceed RGOs.
A comparative analysis of the three site -wide alternatives resulted in the selection of
Alternative 2, source area treatment using enhanced bioremediation and aeration/volatilization of
contaminants in surface water, as the alternative that best balances reduction of contaminant
mass and associated risks to human health and the environment and costs. All three alternatives
are effective at protecting human health and the environment over the short and long term
through a combination of passive and/or active measures. Alternatives 2 and 3 are superior to
Alternative 1 in that they 1) provide enhanced control of the source of releases; 2) provide a
greater reduction in toxicity, mobility and volume of waste; and 3) satisfy a statutory preference
for active treatment. The enhanced bioremediation in the source area also reduces the
uncertainty inherent in a purely MNA approach at a site where existing conditions are not
conducive to natural biodegradation.
Alternative 3 provides additional control of contaminant migration and discharge to surface
water relative to Alternative 2, but at additional cost, decreased short-term effectiveness, and
possibly decreased implementability due to considerably more complex O&M requirements.
Given that surface water is not used for human consumption or contact, provides limited if any
environmentally significant habitat, and contaminant migration can be controlled through
engineered aeration/volatilization, Alternative 3 provides only marginal benefits relative to
Alternative 2. Therefore, Alternative 2, source treatment, NINA, and engineered
aeration/volatilization of surface water, offers the best balance against RCRA screening criteria
and costs. The alternative is protective of human health and the environment and is both readily
implementable and cost effective.
Alternative 2 would use a combination of active and passive treatment technologies and
institutional controls to provide protection of human health and the environment. Enhanced
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bioremediation in the source zone would be used to reduce the contaminant flux from the clay
layer to the surficial aquifer and eventually from the groundwater to surface water. MNA would
be relied upon to further reduce contaminant concentrations throughout the plume and would
require monitoring of contaminant levels to ensure that the mass of contamination in the
groundwater is reducing with time. Aeration/volatilization would be used to reduce 1,1,2,2-
tetrachloroethane concentrations to levels below surface water standards at a point within the
footprint of the SWMU 103 groundwater plume' (currently understood to extend as far as the
point where Beaver Creek flows under Knox Road). A combination of new and existing fencing
would prevent human contact with surface water containing 1,1,2,2-tetrachloroethane
concentrations above surface water standards. Institutional controls and soil gas, groundwater,
and surface water monitoring would be used to ensure the protection of'tihuman health and the
environment and to monitor performance over the implementation time required to meet
remedial levels. Administrative and groundwater -use restrictions would be implemented during
the period of ownership by the U. S. Department of Defense through restrictions imposed by the
Base Master Plan (BMP) and the Hazardous and Solid Waste Amendments permit. Use of
groundwater within the plume boundaries for drinking water and irrigation would be prohibited.
Warning signs would be installed along Beaver Creek and the Holbrook tributary to reduce
contact with the contaminated surface water. Alternative 2 would be easily implementable and its
implementation would not impact human health or the environment.
..,
Soil gas samples would be collected annually from three existing soil gas monitoring points
located at Holbrook Elementary School to ensure that VOCs are not migrating from the
groundwater into the overlying soil vapor at concentrations that represent a risk to human health.
Performance groundwater sampling would be performed quarterly for the first year, then on
an annual basis at 31 wells to monitor the progress of the remedial actions. Monitoring locations
and frequency would be optimized over time pending monitoring results. Corf rmatory sampling
would be performed two years after the last MNA performance sampling to ensure degradation
and lack of contaminant rebound. Surface water samples would be collected annually at six
locations until surface water meets 1,1,2,2-tetrachloroethane standards throughout its reach in the
vicinity of SWMU 103. Groundwater and surface water will be analyzed for VOCs. Semivolatile
organic compounds in groundwater will also be targeted for analysis at selected locations in the
source area.
The total time to implement Alternative 2 is estimated to be approximately 60 years. The total
capital cost for Alternative 2 is $961,000. The operation and maintenance costs are $2,351,650.
The total cost of Alternative 2 is $3,312,650.
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SECTION 1
INTRODUCTION
This corrective measures study (CMS) for Solid Waste Management Unit (SWMU) 103 at the
Fort Bragg Military Reservation, North Carolina, summarizes the results from the Resource
Conservation and Recovery Act (RCRA) facility investigation (RFI) by SAIC Engineering of
North Carolina (hereafter referred to as SAIC Engineering) and presents results of supplemental
subsurface soil and groundwater sampling, and bench -scale and pilot studies performed in
calendar year (CY) 2005. Remedial response objectives (RROs) that are protective of human
health and the environment are developed for the contaminants of concern (COCs) identified in
groundwater and surface water. Applicable corrective action process options and technologies
are screened and combined into potential alternatives to meet RROs developed for SWMU 103.
The corrective action alternatives are evaluated, one alternative is selected, and a detailed
conceptual design is developed.
This report has been prepared by Parsons Infrastructure and Technology Group (Parsons) for
the Army Environmental Command under contract number W91ZLK-050D-0016, task order
0001.
The former Mallonee Village Gas Station, hereafter referred to as SWMU 103, is located at
the corner of Honeycutt Road and South Lucas Drive (Figure 1-1). The site was previously
considered to be part of S WMUs 4 and 18; however, the results of a field investigation
conducted, as reported in the Field Investigation Report for the Phase I RFI for SWMU 103
dated November 2000 (SAIC Engineering 2000a), and a records search performed June/July
2000 in the area east of Beaver Creek (SAIC Engineering 2000b), indicated that the probable
source of the potential contamination east of Beaver Creek was removed underground storage
tanks (USTs) located at Building 6-9650. The UST site was known as the Mallonee Village Gas
Station (Figure 1-2) and contained up to 10 USTs during its operation, which included one
13,500-gallon (gal) diesel tank; one 10,000-gal gasoline tank; two 1,000-gal heating fuel tanks,
two 10,000-gal gasoline tanks; one 6,000-gal tank; one 6,000-gal diesel tank, one waste oil tank,
and one solvent tank. The site, which was formally closed in 1998, was formally identified as
SWMU 103 in CY 2000.
An observational approach was used for the RFI at SWMU 103 and vicinity, resulting in five
separate field mobilizations beginning in June/July 2000 and culminating in September 2003.
The individual field investigations under the RFI for SWMU 103 included supplemental .
collection and analysis of media samples from SWMUs 4, 5, and 18, which are located (Figure
1-1) west and southwest of SWMU 103, respectively, to support the site -wide groundwater
analysis. The results from these field investigations were evaluated in the Site Conceptual Model
Report for the Former Mallonee Village Gas Station and Vicinity that includes SWMUs 4, 5, and
18 at Fort Bragg, North Carolina (SAIC 2004a). The RFI for the Former Mallonee Village Gas
i
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Station SWMU 103 at Fort Bragg, North Carolina (SAIC 2004b), which is a companion
document to the site conceptual model (SCM), was issued in September 2004. This document
concluded that the nature and extent of contamination had been determined at SWMU 103 and
recommended that a CMS be developed.
1.1 SITE BACKGROUND
SWMU 103 was discovered during the investigation of SWMUs 4 and 18 located west of
SWMU 103 (Figure 1-1). SWMU 4 is an abandoned landfill covering an area of approximately
10 acres. SWMU 18 consists of two fire protection training pits, which overlie a northern section
of SWMU 4. One oil/water separator (OWS) (#6-9273) and one heating -oil UST (#6-9273-A)
are located at SWMU 18 as part of the fire protection training pits. The OWS was removed as
part of the closure of SWMU 18. The heating -oil UST was removed and replaced with an
aboveground storage tank for continued heating of the building.
SWMU 18 is located entirely within the SWMU 4 boundary. SWMUs 4 and 18 are located in
the central part of the Fort Bragg cantonment area, southeast of the intersection of Honeycutt
Road and Knox Street, as shown on Figure 1-1.
During the RFI conducted by the U. S. Geological Survey for SWMUs 4 and 18 (USGS
1998), groundwater contamination was discovered at 4MWS1, which was a background well
located east of Beaver Creek and east of the boundary of SWMUs 4 and 18. The RFI concluded
that this groundwater contamination could be the source of similar_ contaminants detected in
Beaver Creek. The RFI also concluded that the groundwater contaminant plume east of Beaver {
Creek was probably not related to the SWMUs 4 and 18 sites.
A records search performed during June/July 2000 in the area east of Beaver Creek (SAIC
Engineering 2000b) indicated that the probable source of the potential contamination east of
Beaver Creek was removed USTs located at Building 6-9650. The UST site was known as the
Mallonee Village Gas Station. Two UST removals have been documented by closure reports.
The following four USTs located west of (i.e., behind) Building 6-9650 were removed in 1996:
one 13,500-gal diesel tank, one 10,000-gal gasoline tank, and two 1,000-gal heating fuel tanks
(Earth Tech 1996). The following four USTs were removed in 1998: two 10,000-gal gasoline
tanks; one 6,000-gal tank; and one 6,000-gal diesel tank (Mid -Atlantic Associates, P.A. [Mid -
Atlantic] 1998). Information obtained during the records search also indicated that one waste oil
tank and one solvent tank had been removed before (date unknown) the inception of current UST
regulations; therefore, no closure reports were available for review. With the concurrence of the
North Carolina Department of Environment and Natural Resources (NCDENR), the area east of
Beaver Creek received its own SWMU designation and is now identified as the former Mallonee
Village Gas Station (SWMU 103). The location of the newly designated SWMU 103 is
identified on Figure 1-1 and the RFI investigation separated it from the extended RFI for
SWMUs 4 and 18.
In addition, following designation of SWMU 103 with its own reference number, the Fort
Bragg Department of Public Works (DPW), with the concurrence of the U.S. Army Corps of
Engineers (USACE), Savannah District and NCDENR, decided to evaluate groundwater at
SWMUs 4 and 18; the former Mallonee Village Gas Station (SWMU 103); and adjacent SWMU
5, an abandoned landfill, as one unit (i.e., on an area- or site -wide basis) to identify any potential
influences between the four SWMUs. SWMU 103 is directly east of Beaver Creek, which
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f
borders the eastern side of SWMUs 4 and 18 (Figure 1-1). SWMU 5 is approximately 200 feet
west of SWMUs 4 and 18 across Knox Street.
1.2 REGULATORY BACKGROUND
Fort Bragg is a U. S. Department of Defense (DoD) facility in the Installation Restoration
Program (IRP). Under the IRP, the* facility is required to work toward compliance with federal
and state environmental laws and regulations. In 1988 a RCRA facility assessment of the
Reservation was performed to identify areas of concern (AOCs) with respect to compliance with
RCRA and the Hazardous and Solid Waste Amendments (HS WA) (Kearney, Inc., and DPRA,
Inc. 1988). Fort Bragg holds a RCRA permit issued by the U. S. Environmental Protection
Agency (EPA) Region 4 and NCDENR. An RFI was performed to address environmental
conditions at 31 SWMUs and 7 AOCs at Fort Bragg in accordance with RCRA corrective action
guidelines. The RFI included a field investigation of SWMUs 4 and 18 between 1992 and 1997
to determine the nature and extent of contamination in soil and groundwater and the potential for
migration of contamination from the source areas. SWMU 103 was discovered during the
investigation of SWMUs 4 and 18. The former Mallonee Village Gas Station was formally
identified as SWMU 103 in CY 2000.
The regulatory authority governing the action at SWMU 103 is RCRA, 40 Code of Federal
Regulations 264; Title II, Subpart C, Section 3004 (42 United States Code 690 et seq.).
Regulatory criteria and guidance for corrective actions at SWMU 103 include groundwater
cleanup standards. The North Carolina Standards for Groundwater Protection [15A North
- - Carolina Administrative Code (NCAC) 2L and interim maximum acceptable concentrations
(IMAC)] are criteria for cleanup for groundwater. The North Carolina action levels are
- calculated values equivalent to a remedial goal option (RGO) protective of a 1E-06 excess cancer
risk or a non-cancerhazard quotient (HQ) of 1.0. Surface water (i.e., Beaver Creek and the
Holbrook tributary) was compared to North Carolina standards for all freshwater classifications
(Class C) dated April 1, 2003 (NCDENR 2003). In the absence of a North Carolina standard for
all freshwater classification values, the constituent was compared to the more stringent North
Carolina water supply (WS) classes for surface water. North Carolina has five classifications for
WS surface waters (WS-I through WS-V). In the absence of either a North Carolina Class C or
WS value, the surface water result was compared to a federal 304a standard (EPA 1998).
1.3 SCOPE OF THE CORRECTIVE MEASURES STUDY
The scope of this CMS contains two distinct elements. One focuses on the summary and
evaluation of the supplemental subsurface soil and groundwater data collected in CY 2005 and
CY 2006 to update the nature and extent of contamination in these media and the evaluation of
bench -scale and in -situ pilot studies to evaluate potential remedial technologies for groundwater.
The second involves the evaluation of applicable corrective actions and selection of an
appropriate corrective action alternative that will be protective of human health and the
environment (CMS activities). The scope of the CMS is presented below.
• Summarize results of the soil, groundwater, and soil gas data collected at SWMU 103 in
CY 2005 and CY 2006.
• Summarize the results of the bench -scale and in -situ pilot studies performed in CY 2005.
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• Update the nature.and.extent of subsurface soil and groundwater contamination.: -
Develop RGOs and subsequent RROs for COCs that. are -protective of human :health: and
the environment.
• , Screen. applicable:.corrective; action technologies and, process: options and develop .site -
wide corrective action alternatives that meet the RROs..
Select ,an, appropriate .site -wide corrective. action .alternative that is protective of human:
health and-the.environment: and develop a conceptual design for the alternative.
1.4 CORRECTIVE MEASURES STUDY' REPORT ORGANIZATION
This CMS report is divided into seven chapters. Chapter 1,;0, Introduction; presents, general
background .information . on Fort : Bragg, , specific background -information, . on'the . project: and
SWMU 103, and, regulatory background information; as . Well. as an:' explanati6n of the. scope.
Chapter 2.0, Site Characterization, provides, an overview of SWMU 103; physical and -
environmental - descriptions, and supplemental:investigations. performed in CY 2005'. Chapter .
.0; Update of Nature and Extent and the SCM, presents a summary and , update .of nature ' and
extent :of contamination, contaminant fate and: transport (F&T); and : SC1VI based on results from,
the supplemental investigation performed in CY 2005. Chapter 4.0, Justification and Purpose:of
Corrective :Action,, presents the purpose of the corrective action.: and .proposed remedial .levels.
Chapter 5.0, Screening of.Corrective Actions,,' presents ari:evaluation of corrective actions and
screens them against established objectives and balancing.- factors. Chapter'.6.0, Conceptual
Design and. Implementation Plan; -identifies the: selected .corrective::actions for SWMU .103, '
presents; design ;and implementation, details, and .provides a cost estimate and-, schedule for .the .
remedy. References are presented in Chapter 7.0.
The following. appendices are, also included:
• Appendix A, soil .boring logs;
• Appendix B; monitoring and injection:well construction;diagrams;
• Appendix C; laboratory analytical data and chain -of -custody for sampling conducted in
CY.2005;. .
Appendix D,.slug test results;
Appendix E,: results of the in-situ.,pilot study;
• Appendix- F; supplemental investigation;
Appendix G, complete:data sets for subsurface soil a nd.grouridwater;
Appendix J; laboratory analytical data and chains -of -custody for. samplingconducted. in
CY 2006; and .
Appendix K, the F&YmodeL .
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SECTION 2
SITE CHARACTERIZATION
The site characterization infonnation presented in Sections 2.1 through 2.7 has been
summarized from the SCM Report for SWMU 103 at Fort Bragg, North Carolina (SAIC 2004a).
The results from the field investigations conducted by SAIC Engineering in March through
August 2005 are summarized in Sections 2.8 and 2.9.
2.1 SITE OVERVIEW
Fort Bragg is situated in northwestern Cumberland County and northern Hoke County.
Cumberland County occupies about 661 square miles and had a population of 302,000 in 2000
(U. S. Census Bureau 2000). Hoke County occupies about 414 square miles and had a
population of 34,000 in 2000 (U. S. Census Bureau 2000).
Fort Bragg had a combined military and civilian population of 29,000 according to the 2000
census (U. S. Census Bureau 2000). The principal population centers near Fort Bragg are the city
of Fayetteville, 5 Miles to the southeast, and Spring Lake, adjacent to the northeastern boundary
of Fort Bragg (see Figure 2-1). The populations of Fayetteville and Spring Lake in 2000 were
121,000 and 8,100, respectively (U. S. Census Bureau 2000).
Property use in the vicinity of SWMU 103 is shown on Figure 2-2 and is.summarized below.
Directly east across South Lucas Drive is a vacant, asphalt parking area, which used to be the
location of the Mallonee Village Shopping Center. The Mallonee Village Shopping Center was
demolished in CY 2004, An elementary school (Holbrook Elementary School) is also -located
across South Luca's Drive but slightly southeast of SWMU 103.
Directly south of SWMU 1103 along South Lucas Drive are a credit union and a Sprint
telephone building. A maintenance area that supports Fort Bragg housing is located directly west
of SWMU 103. Residential housing occupies the remaining property to the south, east, and north
of SWMU 103. The Officer's Club Golf Course is northwest of the intersection of Knox Street
and Honeycutt Road. Carolina Power and Light power transmission lines running north to south
are located west of SWMU 103, between it and Beaver Creek.
Several SWMUs (i.e., SWMUs 4 and 18, SWMU 5, SWMU 8, and SWMU 9, which are part
of the Fort Bragg IRP) are located in the vicinity of SWMU 103. SWMUs 4 and 18 are located
west of Beaver Creek and SWMU 103. SWMU 5 is located approximately 250 feet southwest of
the southern portion of SWMU 4. The Knox Street railroad yard (Honeycutt Marshalling Yard)
is located west of Beaver Creek and southwest of SWMU 103. The closest part of SWMU 8 is
approximately 500 feet southwest of SWMUs 4 and 18, while SWMU 9 is approximately 2,000
feet southwest.
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2.2 TOPOGRAPHY, PHYSIOGRAPHY, AND CLIMATE
SWMU 103 is located on a gentle, sloping hill that decreases in elevation to the west and
southwest toward Beaver Creek and to the south and east toward the Holbrook tributary. The
topography continues to increase in elevation to the north. The elevation of the land surface at
SWMU 103 is approximately 250 feet above mean sea level (AMSL) and decreases to an
elevation of approximately 220 feet AMSL near Beaver Creek. Beaver Creek is the only surface
water body at the site and flanks the western side of the SWMU 103 investigation area. The
Holbrook tributary of Beaver'Creek is located east and south of SWMU 103. The topography of
SWMU 103 and the adjacent area is presented on Figure 1-1.
Fort Bragg is situated in the Sand Hills hydrologic zone of the North Carolina Coastal Plain.
The Coastal Plain extends westward from the Atlantic Ocean to the Fall Line, a distance of about
130 miles. The Fall Line is the boundary between the Coastal Plain and Piedmont physiographic
provinces. The Sand Hills area is characterized by deep, sandy soil and has the most variable
topography and highest land -surface elevations in the Coastal Plain. The topography at Fort
Bragg is characterized by gently to steeply sloping ridges; the highest ridges are in the central
part of the Reservation. Elevations range from approximately 550 feet AMSL in the western part
of the Reservation to approximately 150 feet AMSL in the northeastern part along Little River.
The climate at Fort Bragg is classified as subtropical with long, hot summers and mild
winters. From 1951 to 1980 the mean annual rainfall was 47.80 inches (in). From 1984 to 1993
the mean annual precipitation at Pope Air Force Base (which is adjacent to Fort Bragg), located
approximately 2 miles north of SWMU 5, was 45.99 in. Intense rainstorms occur primarily
during the summer months. During this period, relative humidity ranged from an average of 63%
in April to 76% in August. From 1984 through 1993 the mean annual temperature was 62.4
degrees Fahrenheit (7). The prevailing wind direction at Fort Bragg is.from the southwest, with
an average velocity of about 9 miles per hour (mph) (USGS 1996).
Total evaporation data are available for a site operated by the National Oceanic and
Atmospheric Agency in Hofmann Forest, Onslow County (NOAA 1984-1993). Evaporation
rates at the Hofinann Forest site are considered- to be representative of the Sand Hills and
southern Coastal Plain of North Carolina with which Fort Bragg is identified. From 1984 through
1993, the average annual evaporation at the Hofinann Forest site was 38.27 in. The highest mean
monthly evaporation rate at Hofinann Forest was in June (6.74 in.), and the lowest was in
December (1.64 in.) (USGS 1996).
2.3 WATER SUPPLY
Drinking water supplies for Fort Bragg and surrounding areas are primarily obtained from
surface water sources. One exception is that of the town of Spring Lake, which obtains most of
its water supply from groundwater sources. Spring Lake is located northeast of Fort Bragg, north
of the cantonment area. Water used at Fort Bragg for drinking water purposes is obtained from
Little River, which has. a drainage area of about 348 square miles. The average rate of water use
at Fort Bragg was 7.2 million gallons per day (gpd) in 1994 (USGS 1998). Water is impounded
at two dams near *the water treatment plant. Two supplemental water supply reservoirs are
maintained at Fort Bragg: Lake McArthur in the northwestern corner of the Military Reservation
and McKellar's Pond at the northwestern side of the cantonment area. These two reservoirs,
which drain into Little River, have storage capacities of 9.6 and 2.6 billion gal, respectively
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- f (USGS 1998). As of 1994, withdrawal from these reservoirs to supplement the Fort Bragg water
supply had not been necessary. Water supplies for the city of Fayetteville, which is southeast of
.Fort Bragg,. are obtained from the Cape Fear River and impoundments along Cross Creek and
Lower Cross Creek, which drain the southeastern part of Fort Bragg.
The Middendorf Aquifer, the Cape Fear Aquifer, and the underlying saprolite-bedrock aquifer
represent three potential sources of groundwater. There are 28 water supply wells at Fort Bragg
used for purposes other than drinking water supply (Figure 2-3). Reported well depths range
from 62 to 600 feet below ground surface '(bgs), with a median reported depth of 93 feet;
reported yields range from 5 to 170,gallons per minute (gpm). Water levels in these 28 wells
range in depth from 11.5 to 85 feet bgs. The depths of the screened intervals and the aquifers
(Middendorf Aquifer, Cape Fear Aquifer, or underlying saprolite-bedrock aquifer) in which they
are screened are unknown.
Eleven of the 28 wells at Fort Bragg (wells 12 to 18 and 26 to 29) are located in the
cantonment area. All of these wells are used to irrigate golf courses. Well 10, located
approximately 3 miles east of SWMU 103 at the Smith Lake Bath House and which previously
provided potable water, has been plugged and abandoned. Five of the 11 irrigation wells are
located at the Ryder (Officer's Club) Golf Course (wells 12' to 16), northwest and upgradient of
SWMUs 4 and 18, and are within the Beaver Creek drainage area. The bottoms of the well
screens are estimated to be at elevations ranging from 150 to 220 feet AMSL, thus suggesting
that these wells are screened in the Middendorf Aquifer and the underlying Cape Fear Aquifer.
Based on the groundwater potentiometric surface, it does not appear that these irrigation wells
influence groundwater flow or contaminant transport in the vicinity of SWMU 103 (see Section
2.5).
Six of the 11 supply wells (wells 17 and 18 and 26!through 29) are located at the Stryker Golf
Course, .southeast of SWMU 103. The depths of two of these wells range from 152 to 164 feet
bgs; however, completion information on the remaining four water supply wells at the Stryker
Golf Course is unavailable.
The remaining wells at Fort.Bragg are outside the cantonment area and are used for various
needs other than drinking water supply. Because groundwater from SWMU 103 flows directly to
Beaver Creek, it is unlikely that potential contamination would affect water quality at the more
distant potable supply wells.
The municipal supply wells nearest SWMU 103 are in. Spring Lake. Approximately 25% of
the water used by Spring Lake is supplied by the city of Fayetteville water system, and the
remaining 75% is supplied by five municipal supply wells maintained by the Spring Lake Public
Works_ Department (USGS 1998). Wells 8, 9, 10, and 12 are located 3.5 to 4.0 miles north of
SWMU 103. The.: Spring Lake wells, with . the exception of one well designated 11A, are
screened in the Cape Fear Aquifer. Well 1 IA is screened at the base of the Middendorf Aquifer.
Reported well yields range from 90 to 180 gpm. Because these wells lie to the north of SWMU
103 and groundwater flow in the Middendorf Aquifer at SWMU 103 is to the southwest into
Beaver Creek, these wells are not likely to be affected by contamination.
LaGrange Waterworks, which supplies water to residential areas southwest of Fort Bragg and
west of Fayetteville, has 39. wells ranging from 75 to 100 feet deep, with yields ranging from 35
to 150 gpm (USGS 1998).
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2.4 SITE GEOLOGY
The following geology discussion is summarized from the RFI Report for SWMUs 4 and. 18
(USGS 1998). As discussed previously, SWMU 103 is located approximately 1,000 feet east of
Beaver Creek and SWMUs 4 and 18; therefore, the geology would be expected to be similar. The
information has been supplemented with site -specific information gathered from the installation
of 8 soil borings for soil characterization and 53 soil borings for the installation of 50 monitoring
wells and 3 injection wells during the field investigations performed from June/July 2000 to
March 2005 at SWMU 103. The borings logs for borings installed for the installation of injection
wells (IW1 through IW3) and monitoring wells (MW41 through MW50) and for soil sampling
for the supplemental investigation for SWMU 103 are presented in Appendix A.
Geologic units in the Fort Bragg area, ranging from oldest to youngest, include the Carolina
Slate Belt rocks, which comprise the basement rock, the Cape Fear Formation, and the
Middendorf Formation. Carolina Slate Belt rocks, which underlie the younger sedimentary rocks,
are of Precambrian and Cambrian age and are composed of metavolcanic, metasedimentary, and
igneous rock (USGS 1998). In some areas, these rocks were exposed to weathering before the
overlying sediments were deposited, creating a .zone of porous saprolite at the top of the
basement rock. The elevation of the top of the basement rock ranges from 180 feet AMSL at
Southern Pines, near the western edge of the Military Reservation, to 110 feet below sea level
near the confluence of the Cape Fear River and Rockfish Creek (USGS 1998). The Cape Fear
and Middendorf Formations overlie the basement rock and saprolite. These formations are part -
of the generally southeastward -dipping and -thickening wedge of sediments that constitute the
Atlantic Coastal Plain deposits.
The Cape Fear Formation is composed primarily of clay interbedded with silt and silty sand.
Water in the Cape Fear Aquifer is under confined conditions. The uppermost Cape Fear
Formation consists of clay and sandy clay and ranges from 10 to 15 feet in thickness. Twenty-
seven of the 50 monitoring wells and all 3 injection wells installed during the field activities for
SWMU 103 were completed at the top of the Cape Fear Formation. The top of the Cape Fear
Formation was observed at approximately 43 feet bgs [211.38 feet AMSL (MW48)] to 65 feet
bgs [191.5 feet AMSL (MW6)] in the vicinity of the source area (former Mallonee Village Gas
Station) and 26 feet bgs [190.4 feet AMSL (MW18)] to 36 feet bgs [179.5 feet AMSL (MW2)]
in the area immediately east of Beaver Creek. The Cape Fear Formation was also observed at 82
feet bgs [187.2 feet AMSL (MW11)] upgradient of the source area.
Figure 2-4 presents an update of the clay contour (surface of the top of the Cape Fear
formation) below SWMU 103. The surface of the clay influences contaminant transport in
groundwater at SWMU 103. The clay surface has a local high or ridge that trends from the
northwest to the southeast across the site. The probable source area (former Mallonee Village
Gas Station) is located just upgradient of this ridge on the edge of a topographic low or trough in
the clay surface. The trough extends from north of Honeycutt Road (MW11) to the south as far
as the former gas station, then curves to the southeast toward Holbrook tributary (MW15). Wells
MW9 and MW12 are on the east side of the trough. The impact of the clay surface on
groundwater flow is described in Section 2.5. ,
As previously stated, the Middendorf Formation unconformably overlies the Cape Fear
Formation and forms the land surface everywhere in the area, except where it has been removed
by erosion in the valley of Little River and its major tributaries and in part of Rockfish Creek
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Valley. SWMU 103 is underlain' by an alternating succession'of sands, silty sands, clayey sands,
and clays of the Middendorf Formation. The Middendorf Formation at SWMU 103 ranges in
thickness from approximately 20 feet (near Beaver Creek) to 80 feet (MW10/MW11). Generally,
the Middendorf Aquifer is unconfined at SWMU 103, although semiconfined conditions can
occur locally.
2.5 HYDROGEOLOGY
The Fort.Bragg area is underlain by three freshwater aquifers: the saprolite-basement, Cape
Fear, and Middendorf aquifers (Figure 2-5). The major water -bearing strata at Fort Bragg are in
the Middendorf Formation, referred to as the Middendorf Aquifer.
The saprolite-basement rock aquifer is below the Cape Fear Formation, and its depth ranges
from 140 feet bgs in low-lying parts of the cantonment area to 300 feet or more bgs in the central
and western parts of Fort Bragg. The saprolite-basement aquifer is generally assumed to yield
little water, and no supply wells in this area are known to tap solely this aquifer. The Cape Fear
Aquifer is composed of the Cape Fear Formation, which is primarily clay interbedded with silt
and silty sand under confined conditions. The uppermost 5 to 10 feet of the Cape Fear Formation
in the Fort Bragg area form the. Cape Fear confining unit. This confining unit restricts vertical
movement of water between the overlying sediments and the.silty sand units of the Cape Fear
Aquifer. East of Fort Bragg, the Cape Fear Aquifer is used for public and industrial water
supplies (USGS 1998).
The Middendorf Aquifer primarily consists of coarse- to fine-grained silty or clayey sands,
with interbedded light gray to tan clays. The interbedded and discontinuous clay layers in this
aquifer support local perched water zones. Perched water zones in the Fort Bragg area generally
are within 20 feet of ground surface, and groundwater in these perched zones is under
unconfined conditions and referred to as the surficial aquifer. The saturated thickness of the
water table within a perched water zone is typically only a few feet. Many of the perched water
zones dry out during the growing season and are not reliable sources of water supply (USGS
1998).
Groundwater in the lower part of the Middendorf Aquifer is commonly under confined or
semiconfined conditions, as determined by interbedded clay layers, whereas groundwater in the
upper part of the Middendorf Aquifer is under unconfined conditions. The potentiometric' surface
of the aquifer is as much as 80 feet bgs in upland areas of the Military Reservation and is near
land surface along perennial streams (discharge areas for the Middendorf Aquifer).
The sandy soil that covers most of Fort Bragg and the Middendorf Aquifer is leached beds of
the Middendorf Formation. This sand is highly permeable and allows rapidinfiltration of
precipitation, which is the primary source of groundwater recharge.
Groundwater at SWMU 103 is evaluated on an area -wide basis across SWMU 103, SWMUs
4 and 18, and SWMU 5; therefore, water levels were measured from all wells installed at these
SWMUs. A total of 50 monitoring wells (MW1 through MW50) and 3 injection wells were
installed as part of field investigations specific to SWMU 103. Sixteen monitoring wells
(AE14A4-1 through 4MWS1, 4MWS3, 4MWS4, 4MWS6 through 4MWS11) exist at SWMUs 4
and 18. Ten existing monitoring wells (5MWD1 5MWD2, and 5MWS1 through 5MWS8) make
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up the groundwater monitoring network around SWMU 5. Water levels collected in April 2005
from these wells were used to develop area -wide shallow and deep surficial groundwater maps.
Monitoring wells screened across the water table were used to develop the shallow
groundwater potentiometric maps. Water level measurements from the wells screened at the top
of the Cape Fear confining unit were used to develop the deep groundwater potentiometric maps.
Some wells at SWMUs 4 and 18 and SWMU 5 were installed to evaluate a specific screened
interval and did not fit the specific shallow/deep identification. Water level measurements from
wells identified as intermediate were not used in either the shallow or deep interpretation. Table
2-1 presents the water levels measured in April 2005 that were used to develop the shallow and
deep site -wide groundwater potentiometric maps. The shallow and deep potentiometric maps for
April 2005 are presented as Figures 2-6 and 2-7, respectively.
Groundwater flow from the potential source area (former Building 6-9650) at SWMU 103 is
primarily to the southwest. The average shallow and deep horizontal hydraulic gradients and
predominant groundwater flow directions from the SWMU 103 source area from each field
investigation are presented in Table 2-2. The 'horizontal hydraulic gradient was consistent
between field investigations, with the shallow and deep horizontal hydraulic gradients ranging
from 0.01 to 0.013 feet/feet. The groundwater flow on both sides of Beaver Creek generally
follows the ground surface topography and is directed toward Beaver Creek.
Although the shallow groundwater can flow southwest with the hydraulic gradients shown in
Figure 2-6, the deep groundwater is prevented from doing so by the clay ridge (Figure 2-4).
Deeper groundwater in the clay trough is either forced to flow southeast toward Holbrook
tributary, or may be relatively stagnant during times of drought.
At SWMU 103 there are 18 nested well pairs consisting of deep and shallow monitoring
wells. The vertical hydraulic gradient for each well pair for each field investigation is presented
in Table 2-3. Eight well pairs located along the northern, eastern, and southern boundaries (i.e.,
MW10/MW11, MW12/MW13, MW14/MW15, MW21/MW20, MW26/1\4W27, MW32/MW33,
MW35/MW36, and MW41/MW42) of the SWMU all have downward vertical hydraulic
gradients. That is, the groundwater elevation in the shallow well -is higher than the groundwater
elevation in the deep well. The range of downward vertical hydraulic gradients is 0.011 to 0.21
foot/foot (ft/ft), with the average being 0.044 ft/ft. Six well pairs located near the source area and
to the south near Beaver Creek and the Holbrook tributary (i.e., MW1/MW2, MW6/MW7,
MW16/MW17, MW18/MW19, MW22/MW23, MW43/MW44, and MW49/MW50) have
upward vertical hydraulic gradients. That is, the groundwater elevation in the deep well is higher
than the groundwater elevation in the shallow well. The range of upward vertical hydraulic
gradients is 0.0041 to 0.062 ft/ft, with the average being 0.028 ft/ft. In addition, two well pairs
(MW8/MW9 and MW37/MW38) located to the east and south of the SWMU have exhibited
reversals in direction of vertical hydraulic gradient. That is, the groundwater elevations in the
deep well are sometimes higher and sometimes lower than the groundwater elevation in the
paired shallow well. Although the vertical gradient at well pair MW8/MW9, which is located
east of SWMU 103, indicated an upward gradient in May 2001, water levels measured in March
2001, January 2003, September 2003, and April 2005 at this well pair have indicated_ a
downward gradient. The vertical gradients at this well pair have ranged from 0.0074 ft/ft upward
to 0.034 ft/ft downward. The vertical gradients for the well pair MW37/MW38, which is located
south of SWMU 103 at Holbrook Elementary School, have ranged from 0.085 ft/ft upward in
January 2003 to 0.0046 ft/ft downward in September 2003 and April 2005. Water levels at the -
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well pair MW47/1\4W48 located at SWMU 103 indicate no difference in water levels between
the shallow and deep portions of the aquifer at this location. However, due to the shallow clay
layer encountered at ,this location, the screened intervalsat this well pair actually overlap by
approximately 3.5 feet and, thus, may not provide an accurate representation of potential
differences between the upper and lower portions of the aquifer.
A laboratory vertical hydraulic conductivity test was conducted on one undisturbed soil
sample from monitoring well MW10 at SWMU 103. The soil sample was collected at20 to 22
feet bgs. The vertical hydraulic conductivity determined for this sample was 6.6E-04 centimeters
per second (cm/sec). During drilling activities the lithology of this sample interval was observed
to be sand.
2.6 SURFACE WATER HYDROLOGY
An east -west -trending ridge divides Fort Bragg into two drainage sub_basins (Figure 2-8). The
northern sub -basin drains into tributaries of the Little River, while the southern sub -basin drains
into tributaries of the Cape Fear River. Surface drainage at SWMU 103, which is in the southern
sub -basin, drains into Beaver Creek and its tributaries. Beaver Creek flows into Cumberland
Creek (Figure 2-8), a tributary of the Cape Fear River, which is east of Fort Bragg. Streams
located on the Military Reservation generally are low gradient and in many areas have poorly
defined channels that grade into swampy areas. Streambeds consist of unconsolidated materials,
typically silt, sand, or clay.
Several man-made impoundments are present at Fort Bragg. and include Lake McArthur in the
northwestern corner of the. Military. reservation, McKellar's Pond in the northeastern part of the
_ Military Reservation, and Smith Lake in the southeastern part of the Military Reservation. There
are no natural lakes at Fort Bragg.
Beaver Creek runs north to south approximately 1,000 feet west of SWMU 103 and along the
eastern boundary of SWMUs 4 and 18. The creek is heavily vegetated in the'area of SWMU 103
and SWMUs 4 and 18. The natural slope of the topography on both the eastern and western sides
is toward the creek; therefore, surface runoff from both sides potentially, migrates to Beaver
Creek (Figure 1-1). The sources of potential runoff in the area include SWMU 103 and SWMUs
4 and 18, the maintenance area that supports Fort Bragg housing, "and a 36-in.-diameter
stormwater pipe outfall that transverses the northern portion of SWMU 4 and receives
stormwater drainage from _ Knox Street (Figure 1-1). In addition, the Holbrook tributary of
Beaver Creek' is .located east and south of SWMU 103. This tributary receives stormwater
drainage from residential areas to the north, east, and south; Holbrook Elementary School to the
north; and Mallonee Village and SWMU 103.
2.7 SITE ECOLOGY
SWMU 103 comprises an asphalt parking lot, concrete pad, and gravel area with no trees and
a few decorative shrubs.:A small grassy slope lies between the site and an adjacent parking lot.
Based on the characteristics of the site, NCDENR (meeting at Fort Bragg on March 10, 2004)
agreed that there is no habitat for ecological receptors at SWMU 103 proper. .
Beaver Creek and the Holbrook tributary flow to the east and south/southeast of SWMU 103
(Figure 1-1). Beaver Creek originates north of SWMU 103 and drains a large area north, south,
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and west of the site. Beaver Creek receives runoff from numerous roads and residential
properties. The Holbrook tributary drains a small area and originates to the east of SWMU 103.
.Beaver Creek is a perennial stream that supports aquatic communities. Drainage from SWMU
103 primarily flows into the Holbrook tributary.
Aquatic receptors in Beaver Creek, the tributaries that flow into the creek, and surrounding
wetlands include invertebrates, plants, algae, amphibians, and fish. The native fish population in
the perennial rivers, streams, and lakes at Fort Bragg includes blue gill, chain pickerel, grass
pickerel, largemouth bass, redbreast,.red ear, warmouth, bowfish, bullhead catfish, carp, channel
catfish, and gizzard shad. However, Beaver Creek and Holbrook tributary are too shallow (often
one or two inches deep) to support larger fish.
2.8 SUPPLEMENTAL INVESTIGATIONS FOR THE CORRECTIVE MEASURES
STUDY
Five field investigations (June/July 2000, April/May 2001, March 2002, December
2002/January 2003, and September 2003) under'the RFI at SWMU 103 were used to determine
the nature and extent of contamination and the SCM for SWMU 103 (SAIC 2004a). All of the
activities performed for field investigation at SWMU 103 through CY 2003 were summarized in
the SCM Report (SAIC 2004a). The RFl (SAIC 2004b) concluded that a CMS was required for
SWMU 103 and supplemental investigations and. bench -scale and in -situ pilot studies were
required (see Section 1.3).
The objectives for the additional field activities for CMS for SWMU 103 at Fort Bragg, North
Carolina, were. based on recommendations made in the RFI (SAIC Engineering 2002); the
USAGE, Savannah District scope of work dated August 10, 2004; and modification No.1 to the
USACE, Savannah District scope of work dated January 28, 2005, and include
• defining the present characteristics of the groundwater in the source area at SWMU 103,
• defining the extent of impacted soil and groundwater around the former heating -oil UST
site located east of Building 6-9344-A (this former heating oil UST site has been removed
from SWMU 103 and is being addressed under the North Carolina Risk Based Corrective
Action [RBCA] program),
• defining the present characteristics of the groundwater just upgradient of Holbrook
Elementary School and downgradient of the SWMU 103 source area and former heating -
oil USTs source area at Building 6-9344-A,
• performing a bench -scale pilot study on groundwater from SWMU 103, and
• performing in -situ pilot studies on groundwater in the SWMU 103 source area.
The field activities to support this CMS were presented in the Addendum No. 6 to the
Sampling and Analysis Plan for the Pilot Studies to Support the Corrective Measures Study for
Mallonee Village Gas Station (SWMU 103) at Fort Bragg, North Carolina (SAIC Engineering
2005). The field activities and results are summarized in the following sections.
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- 2.8.1 , Sentinel Wells at Holbrook Elementary School
Two additional monitoring well pairs (each consisting of a shallow and a deep well) were
installed (1) directly downgradient of the -SWMU 103 source area and just upgradient of
Holbrook Elementary School, and (2) directly downgradient of the former.heating-oil USTs and
just upgradient of Holbrook Elementary School.
The locations of the sentinel wells. (MW41 through MW44) are presented on Figure 2-9. The
wells were constructed of 2-in.-diameter polyvinyl chloride (PVC) and have flush -surface
completions. The wells were installed using rotosonic drilling techniques. The shallow surficial
groundwater wells were installed at the water table. The deep surficial groundwater wells were
installed to the top of the underlying clay:layer. The monitoring well construction is summarized
in Table 274.., Boring logs for the installation, of the monitoring wells are presented in Appendix
A. The monitoring well construction diagrams are presented in Appendix B.
One subsurface soil sample was collected from each boring and analyzed for volatile organic
compounds (VOCs), methyl tertiary butyl ether (MTBE), and semivolatile organic compounds
(SVOCs). Groundwater samples were collected a minimum of 14 days after development using
micropurge, low -flow techniques and analyzed for VOCs and MTBE. The shallow surficial
groundwater. wells (MW41 and MW43) were also sampled and analyzed for SVOCs: The chain
of custody and complete analytical results are presented in Appendix C.
2.8.2 Subsurface Soil and Groundwater Around the Former Heating -Oil UST at
Building 6-9344-A
Twelve soil borings (DPT-09 through DPT-20) were installed around the perimeter of the
excavation to remove the former heating -oil USTs at Building 6-9344-A and at points outside
those locations identified as contaminated based on previous investigations using -direct -push
technology (DPT). The DPT, soil borings locations are shown on Figure 2-10. Two subsurface
soil samples. and a groundwater sample were collected from each location. The soil and
groundwater data from the.12 DPTs were used to site the locations of monitoring wells (MW45
and MW46) installed to monitor groundwater contamination over time. The monitoring wells
were installed using rotosonic drilling techniques. The locations of the monitoring wells are
presented on Figure 2=10. The monitoring wells were screened at the water table. The monitoring
well construction is summarized in Table 2=4. Boring logs for the installation of the monitoring
wells are presented in Appendix A. The monitoring well construction diagrams are presented in
Appendix B.
Two subsurface. soil samples and one groundwater sample were collected from each DPT
boring and analyzed.for VOCs, MTBE; and SVOCs. Twenty-four- to 48-hr analytical results
were requested from the analytical laboratory for the soil and groundwater samples from the
DPT locations to. allow the siting, of the two monitoring wells (MW45 and MW46). One
subsurface soil sample was collected from' -the soil borings for the installation of monitoring
wells and analyzed for VOCs, MTBE, and SVOCs.
Groundwater, samples were collected from the two monitoring wells (MW45 and MW46) a
minimum of 14 days after development. In addition, groundwater was collected from existing
well MW69344C. All groundwater samples were collected using micropurge, low -flow
techniques and analyzed for VOCs, MTBE, and SVOCs. Total organic carbon (TOC) and
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chemical oxygen demand (COD) samples also were collected from the new wells (MW45 and
MW46). The chain of custody and complete analytical results are presented in Appendix C. Field
parameters collected during the groundwater sampling are presented in Table 2-5. Since the
performance of these. field activities, the former heating -oil UST site at Building 6-9344-A has
been removed from under RCRA (i.e., the CMS for SWMU 103) and future remedial activities
will be addressed under the North Carolina RBCA Program for USTs; therefore, -the results of
the soil and groundwater sampling from these locations will not be further discussed in this CMS
unless the data from these locations are pertinent to the investigation/CMS for SWMU 103.
2.8.3 Groundwater Sampling of Monitoring Wells at SWMU 103
Groundwater samples were collected from the following monitoring wells to update the
nature and extent of contamination for the CMS and for baseline conditions prior to the SWMU
Pilot Study: MW6, MW7, MW22, MW23, MW26 (shallow site -specific background location),
MW27 (deep site -specific background location), MW35, MW36, MW37, and MW38. The
locations of the wells are presented on Figures 2-9 and 2-11.
The groundwater samples were collected using micropurge, low -flow techniques and
analyzed for VOCs and MTBE. Samples for SVOCs were also collected and analyzed for
groundwater from shallow surficial groundwater wells (MW7, MW22, MW27, MW35, and
MW37). COD and TOC analyses were performed on samples from wells located in the source
areas and background locations (MW22, MW23, MW26, and MW27). The chain of custody and
complete analytical results are presented in Appendix C. Field parameters collected during the
groundwater sampling are presented in Table 2-5.
2.8.4 Slug Tests
Slug tests were performed in the source area of SWMU 103 and the former heating -oil USTs
at Building 6-9344-A to determine the hydraulic conductivity of the aquifer and support the
evaluation of remedial technologies (e.g., injection technologies) in the CMS. The slug tests
were conducted at monitoring well locations distributed across the shallow and deep surficial
groundwater aquifer (shallow and deep monitoring wells) at both the SWMU 103 source area
and the former heating -oil USTs. Because the purpose of the slug tests was to determine the
hydraulic conductivity of the saturated zone adjacent to the well, the position of the static water
level, either above the top of the screened interval or within, the screened interval, was used to
determine the type of test conducted so that a temporary fall of the water level into the screened
interval or a rise of the water level only in the screened interval was avoided. Only a rising head
test (slug withdrawal) was conducted if either of these conditions occurred.
Slug tests were conducted at 10 wells in the vicinity of SWMU 103, which included two well
pairs and six individual wells. The slug test type was based on the available water level data.
Slug tests were conducted by placing a transducer/data logger into the well and allowing the
water level to equilibrate to static conditions. A slug that displaced a minimum of 1 foot of water
was inserted into the well to provide an adequate response for data analysis. For wells where the
water level was above the top of the screened interval, a falling head'test was conducted first by
instantaneously placing the slug into the water column and continuously measuring the water
level decline. The rising head tests were conducted following completion of the falling head test
by rapidly removing the slug from the water column and continuously measuring the water level
rise. The slug tests were continued until at least 85 to 90% of the initial water level measurement
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had been obtained. Data loggers were programmed to record data in a logarithmic mode with
rapid. measurements at the beginning of the test and decreasing measurement intervals as the test
proceeded.
Data recorded by the data logger were transferred to a computer after completion of the tests.
The data were analyzed using the AQTESOLVTM software program for well test analysis to
determine hydraulic conductivity. The Bouwer and Rice method (1976, 1989), which -is
applicable to unconfined aquifers, was used for analysis of the test data.
The results of the slug tests are presented in Table 2-6. The wells tested, slug test type (rising
head or falling head), and hydraulic conductivity results are. indicated in this table. The average
and geometric mean of the hydraulic conductivities determined from the slug test data are both
.approximately 10-3 cm/sec, which is consistent with the expected range, for silty to ,fine sand
(Heath 1984). The complete AQTESOLVTM results and data logger reports are presented in
Appendix D.
2.8.5 Bench -Scale and In -Situ Pilot Study Evaluating Enhanced Bioremediation Using
Aerobic Cometabolic Mechanism
Chlorinated hydrocarbons have been observed to be oxidized cometabolically by microbes
under aerobic conditions (see: Section 5.2.10). The cometabolic process, involves the microbial
breakdown of the chlorinated hydrocarbons where the chlorinated hydrocarbon is oxidized
incidentally by an. enzyme or cofactor produced during microbial metabolism "of another
compound being used as an electron donor. Electron donors that have been observed in aerobic
oxidation include the following: dextrose, methane, ethene, ethane, propane, butane, aromatic
hydrocarbons (such as toluene and phenol), and ammonia. Because of the naturally occurring
aerobic conditions observed in the groundwater at SWMU 103, the following bench -scale and in -
situ pilot studies were performed to evaluate potential bioremediation using aerobic cometabolic
mechanism.
A specialized_ microbial blend (CL-OutTM) developed for effectiveness' against chlorinated
organic solvents manufactured by CL-Solutions and dextrose. were selected as the representative
aerobic bacteria and electron donor, respectively, to evaluate bioremediation using aerobic
cometabolic mechanism. CL-OutTM is comprised of nonpathogenic, naturally occurring bacterial
strains (no artificial mutation or genetic engineering) specifically isolated for their ability to
reduce trichloroethene (TCE) and its degradation products. The bacteria degrade chlorinated
volatile organic compounds (CVOCs) through a cometabolic pathway that requires. a primary
substrate (dextrose) :and an aerobic environment. Oxygenase enzymes oxidize TCE to form an
epoxide; which is further reduced to 1,2-dihydroxy-TCE, that ultimately breaks down to fatty
acids or alcohols and finally to carbon dioxide, chloride ions, and water. The results of the
bench -scale study and in -situ pilot studies are presented in the following sections.
2.8.5.1 Bench -scale study
A bench -scale treatability study was performed to determine whether the addition of
specialized bacteria would be effective for the groundwater at SWMU 103. A. sample of the
groundwater was collected from MW23, the location of the highest 1,1,2,2-tetrachloroethane
concentrations, and shipped to Osprey Biotechnics (Osprey). Table 2-7 presents the results of the
bench -scale testing. 'The complete analytical results and chain of custody are presented in
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Appendix C. Osprey was sent four sets of duplicate samples (40-milliliter vials). Osprey
performed four (A, B, C, and D) replicate bench -scale studies. One vial of each set was
inoculated with 0.2 gram of CL-OutTM/nitrate/dextrose. The other vial of the set was maintained
as a control.
The bench -scale study (Table 2-7) indicated an average 16% percent removal of 1,1,2,2-
tetrachloroethane. The removal of TCE was more sporadic, probably due to the lower initial
concentration level and the fact that WE is produced from the breakdown of 1,1,2,2-
tetrachloroethane. The average percent removal for TCE was 12.5%. According to Dr. Peter
Vandenberg of Osprey, 10 to 20% reduction in contamination indicates success for the bench -
scale testing. The bench -scale testing is a qualitative test to determine if the contaminant can be
degraded by the specialized bacteria. The bench -scale test indicated that 1,1,2,2-
tetrachloroethane was treatable with CL-OutTM and that the in -situ pilot study should be
performed to develop site -specific criteria.
2.8.5.2 In -situ pilot study
The in -situ pilot study was performed based on the results of the bench -scale study and the
results are presented in the following sections.
Pilot Study Design and Injection Procedures. The SWMU 103 Pilot Study consisted of
installation of three injection wells and four monitoring wells, injection of specialized bacteria
during two injection events, and groundwater monitoring over a 2-month period to evaluate the
performance of the injections. Three injection wells (IW1, IW2, and IW3) were installed in the
vicinity of the SWMU 103 source area. Two additional shallow/deep well pairs (MW47/MW48
and MW49/MW50) were installed in the SWMU 103 source area to evaluate the groundwater
treatment by specialized bacteria. These wells were located downgradient of the injection wells.
Figure 2-11 presents the locations of the new monitoring and injection wells. The monitoring and
injection wells were constructed of 2-in.-diameter PVC with flush -surface completions. The
shallow monitoring well was screened across the water table. The deep surficial groundwater
monitoring wells and injection wells were installed to the top of the clay -confining layer. Due to
the shallow nature of the clay -confining unit encountered at the injection well locations, these
wells were completed with a continuous 15-feet screened interval instead of the planned three
separate screened intervals (2 to 5 feet below the water table, midway through the water column,
and at the clay -confining layer). A field change request was submitted to USACE addressing this
change. The wells were installed using rotosonic drilling techniques. The injection wells and
associated monitoring wells were located to have an approximate 10-foot radius between the
injection wells and the nearest downgradient well pair (MW47/MW48) and. an approximate 20-
foot radius to the furthest downgradient well pair (MW49/MW50). The monitoring well
construction is summarized in Table 2-4. Boring logs for the installation of the monitoring wells
are presented in Appendix A. The monitoring and injection well construction diagrams are
presented in Appendix B. The existing well pair MW22/MW23 is located in the source zone but
upgradient of the pilot test and served to represent background conditions for the test. These
wells are also shown on Figure 241.
A microbial blend (CL-OutTM), combined with nutrients, specifically designed for treatment
of chlorinated organic solvents, was injected into the three injection wells to biodegrade 1,1,2,2-
tetrachloroethane and TCE during the SWMU 103 Pilot Study. The specialized bacteria were
shipped from the supplier in freeze-dried, powdered form. The 55-gal Mylar bags, containing _
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approximately 1 gal of bacteria, were mixed with approximately 55 gal of clean, potable water to
produce 55 gal of high -activity microbial. solution. The specialized bacteria were allowed to
activate for 24 hr before injection into the subsurface. One 55-gal drum of CL-OutTM specialized
bacteria solution comprised the initial dosage and was injected (by gravity or pump) into each
injection well. Fifty pounds of dextrose were added to and dissolved in each 55-gal drum of CL-
OutTM prior to injection.
Supplemental oxygen was supplied to the subsurface using a solution of PermeOx®. Prior to
injection of the CL-OutTM, a slurry of PermeOx® was prepared by mixing an appropriate amount
of PermeOx® powder with approximately 5 gal of water. The PermeOx® was then placed in
each injection well by gravity flow. This procedure was repeated until 15 to 20 lbs of PermeOx®
was injected into each injection well. Following injection of the PermeOx®, each well was
surged with a surge block designed for use in a 24n well to distribute the PermeOx&throughout
the screened interval of the well and augment movement of the PermeOx® into the surrounding
formation.
To ensure the CL-OutTM was distributed throughout both the lower and upper portions of the
aquifer, a straddle packer assembly was used in each injection well to isolate the lower and upper
portions of the screened intervals during injection of the CL-OutTM. During injection into the
lower portion of the aquifer, the packer assembly was equipped with a solid section of casing
between the upper and lower packers, and was positioned so that the CL-OutTM could be injected
into the lower 5 feet of the screened interval by placing the lower packer at approximately 10
feet below the top of the screen. The upper packer was positioned across the upper portion of the
screen, which extended above the water level, to seal this portion of the screen and prevent
movement of groundwater out of the unsaturated portion of the screen. For injection into the
upper portion of the aquifer, the packers were positioned similar to the arrangement for injection
into the lower portion of the aquifer, but the solid section of casing between the packers was
replaced with a perforated section of casing to allow flow of the CL-OutTM out of this 5-foot
interval. In this manner, the bottom 5 feet of the screened interval and the top of'the screened
interval above the water level were sealed off and the CL-OutTM could be injected into the upper
5 feet of the aquifer.
The injection of the CL-OutTM was conducted so that one-half of a 55-gal drum of the
microbial solution was injected into the lower portion of the aquifer and the other half was
injected into the upper portion of the aquifer at each injection well. Due to the lower hydraulic
conductivity of the formation at the IW2 injection well, it was necessary to pump the CL-OutTM
into the lower portion of the aquifer at this well. A bladder pump was used for pumping the CL-
OutTM to avoid the high pressures and heat produced by other hydraulic pumps that could
damage the microbes. After injection of the CL-OutTM, fresh, clean potable water was injected to
provide hydraulic head to drive the CL-OutTM into the formation and to flush the screen. This
process was repeated for the second injection, which was performed approximately 30 days after
the initial injection.
In addition to the slurry of PermeOx®, each injection well was equipped with a time -release
diffuser containing PermeOx® following injection of the CL-OutTM solution. The diffusers were
constructed of a 10-foot length of 1.5-in diameter PVC screen sealed with caps on, both ends.
Approximately 5 lbs of PermeOx® powder was placed into fabric socks, which were placed
inside the PVC screen section. The diffusers were lowered into each injection well until
completely submerged and remained in the wells throughout the Pilot Study, with the exception
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of sample collection periods. PermeOxg remained in the diffusers at the completion of the Pilot
Study and was returned to the wells following completion of the last performance monitoring
sampling event.
Table 2-8 presents a summary of the quantities of PermeOx®, CL-OutTM, and potable water
injected into each well during the two injections comprising the Pilot Study at SWMU 103.
Table 2-9 presents a summary of field parameters collected during the Pilot Study.
Pilot Study Performance Monitoring. Groundwater monitoring was conducted at SWMU
103 source area wells following injection of the microbial solution. Groundwater samples for
performance monitoring were collected during four sampling events. These samples were
collected at approximately 7 days following the first injection and at approximately 30 days
following the first injection. Groundwater samples were also collected at approximately 7 days
after the second injection and approximately 30 days after the second injection. The performance
groundwater sampling included three source -area monitoring well pairs (MW22/MW23
[background], MW47/MW48, and MW49/MW50) and the three injection wells (IW1 through
IW3). The locations of the performance monitoring wells are presented on Figure 2-11.
The performance monitoring groundwater samples were collected using micropurge, low -
flow techniques and analyzed for VOCs, chloride, nitrate, TOC, and microbial plate count.
Samples for SVOCs were also collected and analyzed for groundwater from the shallow surficial
groundwater wells (MW22, MW47, and MW49). Accura Analytical Laboratory, Inc. performed
the chemical analyses and Osprey conducted the microbial plate count. The chain of custody and
complete analytical results are presented in Appendix C. Field measurements obtained during the
groundwater sampling activities for the in -situ pilot study are presented in Table 2-9.
In -situ Pilot Study Results. The results of the in -situ pilot study are presented in Table 2-10.
The baseline groundwater samples- were collected on April 13 and 14, 2005, and represent the
concentration of contaminants prior to injection. As discussed in Section 2.8.6.1, PermeOx® and
specialized bacteria were injected March 25 and 26, and June 28 through 30, 2005. Groundwater
samples were collected approximately 7 days and 30 days after each injection to evaluate the
performance of the treatment. Table 2-9 presents the critical field parameters, dissolved oxygen
(DO), pH, and oxidation-reduction potential (ORP) collected during the Pilot Study.
The data indicate that CL-OutTM will probably degrade 1,1,2,2-tetrachlorothane, though the
test was probably too short duration and the dose possibly too low to impact contaminants
beyond the injection wells. The three injection wells were located around MW47 and MW48,
with MW49 and MW50 located to evaluate downgradient performance. 1,1,2,2-Tetrachlorothane
concentrations decreased to essentially nondetect in the injection wells (IW1 through IW3)
where contact with the bacteria, dextrose, and oxygen was assured. Sporadic decreases in
concentrations of 1,1,2,2-tetrachloroethane were observed in MW47 and MW48. 1,1,2,2-
Tetrachlorethane was reduced from 110 µg/L to nondetect (< 1 µg/L) and from 340 to 250 µg/L
in MW47 and MW48, respectively, after 7 days from injection. However, rebound occurred, as
observed in the groundwater samples collected 30 days after the first injection, with
concentrations of 1,1,2,2-tetrachloroethane of 210 and 330 µg/L in MW47. and MW48,
respectively. The pattern of removal is. repeated by the second injection with reductions in
1,1,2,2-tetrachloroethane of 210 to 90 µg/L at MW47 and 330 to <5 [tg/L at MW48, with a
leveling off or rebounding again occurring 30 days after the second injection. It is possible there
was some slight removal of 1,1,2,2-tetrachloroethane in the deep downgradient well MW50; but
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t. the changes in concentration were not much different than those observed in background wells
MW22 and MW23. The influence of the bacteria and dextrose injections were considerably
lower at the downgradient locations. The concentrations of TCE did not follow the removal
patterns for 1,1,2,2-tetrachloroethane. In all of the injection wells, TCE concentrations initially
increased while 1,1,2,2-tetrachloroethane decreased, likely because TCE is produced by the
biological breakdown of 1,1,2,2-tetrachloroethane. No significant changes in TCE concentrations
were observed in any of the monitoring wells. The concentrations of 1,1,2,2-tetrachloroethane;
TCE; and TOC with time for each well are presented in Appendix E. Figures El through E9. The
following summarizes the observations and conclusions of the in -situ pilot study.
CL-OutTM effectively treats 1,1,2,2-tetrachloroethane in groundwater if sufficient oxygen,
nutrients, and buffering are provided: Based on the aquifer flow field, the monitoring well pair
MW47/MW48 is 10 feet downgradient- from IW1 and MW49/MW50 is 15 feet downgradient
from IW2. The MW47/MVd48 well pair experienced changes in plate count, 1,1,2,2-
tetrachloroethane decreases, and TOC increases within 7 days. The response in well pair
MW49/MW50 was considerably less, but TOC increases were observed after 30 days. Thus, the
7-day effective downgradient radius of influence is at least 10 feet.
The optimum CL-OutTM level, as indicated by pseudomonad plate counts of>1,000,000, was
reached in MW47, MW48, and MW49 less than 7 days after the first injection, but was also
observed in background well MW22 at the same time, suggesting a high background population.
The target population was not maintained for 30 days, suggesting either continuous dilution by
aquifer flow and mixing or due to die -off due to limiting factors, such as nutrients, oxygen, or
competition. Along with the rapid rebound of 1,1,2,2-tetrachloroethane in monitoring wells,
these factors may indicate difficulties maintaining target clean-up levels with this technology.
There appears to be good correlation between achieving the target-CL-OutTM population and
the degradation of 1,1,2,2-tetrachloroethane.
TCE increases in the injection wells in which the 1,1,2,2-tetrachloroethane concentration
decreases because TCE is a degradation product of the biological cometabolic degradation of
1,1,2,2-tetrachloroethane. This may be the most convincing evidence of biodegradation
observed in the pilot test.
There does not appear to be a correlation between DO or Redox levels and microbial
population levels.
2-Butanone was detected in injection wells and MW47. It increased during the pilot study in
IW2. Increases in 2-butanone and acetone have been observed at some CL-OutTM treatment sites
(email Mike Saul of CL-Solutions, 2005). These ketones may form as a transformation of
organic acids produced by the breakdown of the solvents.
2.9 SURFACE WATER SAMPLING BY USACE IN MARCH 2O06
Surface water samples were collected in Beaver Creek and the.Holbrook tributary to.update
the nature and extent of groundwater contamination intercepting these surface water bodies. Four
samples were collected in Beaver Creek and 10 were collected in the Holbrook Tributary-. Figure
2-12 identifies the locations. USACE followed guidance from the EPA Region 4 Standard
Operating Procedures for the collection of surface water samples (EPA 2001b). A clean scoop
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with an extension handle was used to collect the surface water samples. Samples were collected -_
as close as possible to the center of either Beaver Creek or the Holbrook tributary. Efforts were
made to minimize collecting sediment in the sample scoop. The sample was collected from the
surface and poured into a laboratory -preserved bottle. A trip blank was included to check for
cross -contamination during shipment. Duplicate samples were taken from the same scoop as the
initial sample and an equipment blank was taken after collection of all the samples.
The results of the surface water sampling performed by USACE as part of the supplemental
sampling are discussed in Appendix F and have been incorporated into the updated site
conceptual model discussion in Section 3.0. The USACE findings did not change the
conclusions of the RFI. The most important finding was 1,1,2,2-tetrachloroethane exceeded
North Carolina surface water standards for approximately 2,200 feet of Holbrook Tributary as
well as in one sample from Beaver Creek just below the confluence of Beaver Creek and
Holbrook Tributary.
2.10 SOIL GAS SAMPLING IN NNE 2006
A total of 18 soil gas piezometers were installed in June 2006 (Figure 2-13) around the
perimeter of the Holbrook Elementary School buildings and within open areas between separate
school buildings. The piezometers were installed as close to the school buildings as reasonably
practicable with consideration of underground structures and utilities. All soil gas sampling was
conducted in accordance with Addendum No. 7 to the Sampling and Analysis Plan to Support
the CMS at the Mallonee Village Gas Station (SAIC 2006).
The boreholes for installation of the soil gas piezometers were created using a Geoprobe®
(DPT) truck -mounted rig to remove the soil from a 2.0- to 3.0-in.-diameter borehole. The
boreholes were advanced to a depth of approximately 8.0 to 10.0 feet bgs. After completion of
the boreholes, the well screen and casing were inserted into the boring so that — 1.0 foot of
granular filter pack material was beneath the well plug. The casing, screen, and fitting materials
for construction of the piezometer were 1.0-in.-diameter, Schedule 40 steel. Screen sections were
commercially fabricated with slotted openings equal to 0.025 cm (0.010 in.). The length of
screen for the piezometer was 2.0 feet. The top of the casing had a threaded, airtight cap that was
fitted with a sample port sized to join to the inlet line of a 6-liter (L) SUMMA canister. After
insertion of the piezometer screen and casing in the borehole, granular filter pack material was
placed within the annular space around the screen to a depth of 1.0 feet above the top of the
screen. Granular filter pack material was 20/40 grade sand. Bentonite was used to create an
annular seal between the granular filter pack and an upper grout seal. Commercially available
bentonite pellets were added to the annular space above the filter pack. A sufficient quantity of
bentonite pellets was added to create a 2.0-feet-thick seal. After placement of the bentonite
pellets, a small volume of VOC-free potable water was added to hydrate the seal material.
Hydration time for thebentonite pellets was a minimum of 1.0 hr.
After completion of the bentonite seal, the remaining annular space from the top of the
bentonite seal was grouted to ground surface. A flush -mount, drive -over well cover was placed
over the piezometer. A concrete collar, with minimum dimensions of 1.5 by 1.5 feet, was poured
around the well cover. Table 2-11 presents a summary of the piezometer construction.
The piezometer was purged approximately 48 hours after placement of the concrete collar to
remove atmospheric air introduced during construction. Purging was accomplished by
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r�
M connecting a vacuum pump to the sampling port located on the piezometer's top cap using
flexible Teflon® or stainless steel tubing. A flow -totalizing indicator was attached to the
discharge line of the vacuum pump: Purging was continued until three well volumes of air were
removed from the piezometer.
Sampling system components were cleaned in accordance with Method TO-15 (EPA 1999)
prior to assembly of the sampling system.
The sampling systems for soil vapor were 6-L subatmospheric SUMMA canisters. For
collection of the soil vapor samples, flow restriction was provided by a critical orifice set to
charge the canisters to the desired end pressure over a 60-second sample collection period. The
sampling system was assembled in accordance with Method TO-15.
Sampling was conducted at least 72 hr after. initial purging of the soil gas monitoring well.
Once the sampling 'system was located at the soil gas sampling station, connection to the sample
port in the piezometer was made with Teflon® or stainless steel tubing fitted with a stainless
steel vacuum valve. Temperature, pressure, and other relevant parameters specified by Method
TO-15 were recorded. The soil gas sample was collected by opening the system's valving for the
specified sample collection period of 60 seconds. Flow restriction was provided by a critical
orifice set to charge the canister to the desired end pressure over this sample collection period.
Upon collection of the samples, the final pressure was checked and recorded. The final system
pressure was — 88 kiloPascals (kPa) (90 to 100 millimeters of mercury [mm Hg] of vacuum).
Upon collection of the air samples, the SUMMA canister's valve was closed. The sampling
line was disconnected from the canister and the canister removed from the sampling system. The
SUMMA canister was ,labeled as required, by the Sampling and Analysis Plan. The canisters
were shipped to the laboratory in a canister shipping case; as required by the manufacturer's r
specifications.
All equipment, including the sampling inlet line, used at each sampling station was dedicated;
therefore, no decontamination was required.
In addition to soil gas samples collected from the soil gas piezometers, one ambient air
sample was collected from each of the two accessible crawl spaces beneath Holbrook
Elementary. School. These air samples were also collected using a 6-L SUMMA canister. The
canisters were placed in an appropriate location within the crawl space and were left for a
minimum 8-hr period. The SUMMA canisters were equipped with a flow controller calibrated to
obtain a time -integrated sample over an 8-hr period.
Air samples were analyzed for VOCs using gas chromatography/mass spectrometry analyses,
as required by EPA Method TO-15. The results of the soil gas sampling performed as part to the
supplemental sampling are presented in Appendix F and have been incorporated into the updated
site conceptual model discussion in Section 3.0. The most significant finding from the soil gas
and crawlspace air sampling was that the contaminants detected in these air samples (largely
petroleum compounds, alcohols, and ketones) were generally notfound in groundwater. The
primary groundwater contaminants, 1,1,2,2-tetrachloroethane and TCE, were not detected in any
of the air samples. Therefore vapor intrusion of VOCs from groundwater into Holbrook
Elementary School does not appear to be occurring to a measurable extent.
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2.11 GROUNDWATER SAMPLING IN JUKE 2006
Groundwater samples were collected from three monitoring well locations (MW35, MW37,
and MW42) around Holbrook Elementary School and one location (MW48) at the SWMU 103
source area to update current contaminant concentrations and to evaluate the potential for vapor
intrusion at the school in conjunction with the soil gas sampling (Section 2.10). The locations of
the wells are presented on Figure 2-14. All groundwater sampling was conducted in accordance
with Addendum No. 7 to the Sampling and Analysis Plan to Support the CMS at Mallonee
Village Gas Station (SAIC 2006). The collection of groundwater samples from the monitoring
wells was accomplished using low -flow, non -dedicated bladder pumps. The groundwater
samples were collected using micropurge, low -flow techniques and analyzed for VOCs. The
results of the groundwater sampling performed as part to the supplemental sampling in June
2006 are discussed in Appendix F and have been incorporated into the updated site conceptual
model discussion in Section 3.0. The most significant finding from the 2006 groundwater
sampling event was that 1,1,2,2-tetrachloroethane and TCE concentrations are stable or
decreasing.
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SECTION 3
UPDATE OF NATURE AND EXTENT OF CONTAMINATION AND THE
SITE CONCEPTUAL MODEL
The update of the nature and extent of contamination and SCM is confined to SWMU 103. As
directed by NCDENR and the Fort Bragg DPW, contaminants identified in the media associated
with the former heating -oil UST will be evaluated and presented in a Comprehensive Site
Assessment Report to. be written by USAGE, Savannah District following the North Carolina
RBCA UST guidance and will not be discussed in the following discussion on the SCM for
SWMU 103.
The supplemental investigation conducted in CY 2005 to support the CMS did not
significantly change the SCM for SWMU 103 described in the SCM Report (SAIC 2004a)
because (1) no constituents of potential concern (COPCs) were identified in the additional
subsurface soil samples collected in CY 2005 (Appendix F), and (2) concentrations. of COCS
-"- detected in groundwater were similar or slightly lower than during the previous investigations
(Appendix F). The SCM and the conclusion for each medium are briefly summarized in the
following section to support the CMS. The only changes that are evident in the updated nature
and extent of contamination and SCM involve .impacts from the removal of the contaminants
originating around the former. heating -oil USTs located at Building 6-9344-C and the update of
the natural attenuation evaluation. The nature and extent of contamination and SCM for SWMU
103 is summarized in the following sections to support the CMS.
3.1 SOURCE OF CONTANHNANTS AT SWMU 103
The source of the contamination originating from SWMU 103 is primarily chlorinated solvent
products released from at least. one UST formerly located at the former Mallonee Village Gas
Station. Through its operational life, the former Mallonee Village Gas Station had up to ten
USTs containing the following petroleum products: waste oil, heating oil, solvents, gasoline,
and diesel fuel (Figure 1-2). All of the USTs have been removed, and surface and subsurface
soils have been excavated in the immediate areas of the USTs and piping. Free product and soil
contamination were indicated during removal actions. Eight of the USTs were removed in 1996
and 1998 under North Carolina UST regulations, and closure reports were submitted for these
USTs. One waste oil UST and one solvent UST were removed prior to the inception of the
current North Carolina UST regulations. Contaminants associated with petroleum products
(benzene and other aromatic VOC and SVOC hydrocarbons, and methyl-tert-butyl ether-
[MTBE]) are believed to be the remnants of spills or leaks from the petroleum USTs removed
under North Carolina UST regulations. Contaminants associated with the former heating oil
UST at Building 6-9344 (Section 2.8.2) are being addressed under the North Carolina RBCA
program for USTs. The SWMU 103 contaminants are chlorinated solvents, believed to have
leaked from the solvent UST at the former gas station.
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No other sources of chlorinated solvent contamination have been identified for SWMU 103.
Relatively high levels of chlorinated solvents were also detected in wells to the east (MW-9 and
MW-12) and south (MW-41 and MW-42) of the former gas station. Higher concentrations of
solvents at these locations are likely due to groundwater transport from the former gas station
source area as influenced by the clay "trough" and not due to separate sources of contamination.
3.2 SOILS AND GEOLOGY
The soils beneath SWMU 103 are primarily sands (average of 82%) with intermittent,
relatively thin clay lenses. The Cape Fear clay -confining unit is present at a depth of
approximately 50 to 60 feet bgs. The indurated clay of this unit has low permeability (10-7 to 10-8
cm/sec) and acts as a barrier to any further vertical contaminant migration; therefore, potential
soil and groundwater contaminants are confined to the Middendorf Formation above the Cape
Fear confining unit. Contours (Figure 2-4) of the surface of the clay indicate a clay high just to
south (downgradient) of the location of the former Mallonee Village Gas Station. The former gas
station is located on the edge of a low trough in the clay that extends toward Holbrook tributary
in the east as well as approximately 750 feet north (upgradient) of the former gas station where
the clay elevation begins to increase around MW10/MW11. This clay trough likely influences
groundwater flow and contaminant transport in the deeper groundwater to the north and east of
the former gas station.
3.3 GROUNDWATER HYDROLOGY
The depth to groundwater at SWMU 103 ranges from approximately 30 feet bgs in the area of
the former Mallonee Village Gas Station area to near ground surface adjacent to Beaver Creek.
The shallow and deep groundwater flow at SWMU 103 is toward Beaver Creek in a southerly to
southwesterly direction.
Shallow and deep potentiometric maps show a consistent groundwater flow direction (see
Figures 2-6 and 2-7 for most current potentiometric maps [April 2005]) to the southwest from
the SWMU 103 source area. However, groundwater flow is influenced by the surface of the
Cape Fear clay (Figure 2-4). Shallow groundwater can flow over the clay ridge to the south of
the former gas station. Deeper groundwater is prevented from flowing south or southwest by the
clay ridge, and is likely diverted in the clay trough to the southeast toward Holbrook tributary.
The horizontal hydraulic gradients of the shallow and deep surficial flow system are
approximately equal with an average of approximately 0.01 ft/ft and do not fluctuate much
seasonally. Vertical gradients at SWMU 103 generally follow expected patterns, with downward
gradients in the higher topographic areas (i.e., above Honeycutt Road) and upward gradients in
the lower topographic areas (i.e., near Beaver Creek). Variations from this pattern could be
attributable to potential clay lenses producing localized semiconfined conditions or to transient
hydraulic conditions (e.g., precipitation).
Beaver Creek represents a groundwater divide between SWMU 103 and SWMUs 4.and 18,
which are approximately 1,000 feet apart.
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3.4 SURFACE WATER HYDROLOGY
There are two prominent surface water features at SWMU 103: Beaver Creek and the
Holbrook tributary (Figure 1-1). Beaver Creek, a perennial stream, runs north to south
approximately 1,000 feet west of SWMU 103 and along the eastern boundary of SWMUs 4 and
18. The natural slope of the topography on both the eastern and western sides is toward Beaver
Creek; therefore, surface runoff from both SWMU 103 and SWMUs 4 and 18 potentially
migrates to Beaver Creek. The sources of potential runoff to Beaver Creek include SWMU 103
and SWMUs 4 and 18, the maintenance area that supports Fort Bragg housing, a 36-in.-diameter
stormwater pipe outfall that transverses the northern portion of SWMU 4 and receives
stormwater drainage from Knox Street, and residential housing.
The Holbrook tributary is located east and south of SWMU 103 and receives stormwater
drainage from residential areas to the north, east, and south and. from Holbrook Elementary
School, the former Mallonee Village Shopping Center, and SWMU 103 to the north.
The groundwater , level near Beaver Creek is near ground . surface, and Beaver Creek
represents a groundwater divide between SWMU 103 and SWMUs 4 and 18, indicating that
groundwater from both SWMU 103 and SWMUs 4 and 18 is intercepting Beaver Creek.
Groundwater from SWMU 103 is also intercepting the Holbrook tributary.
There is only a limited amount of information about surface water flows in Beaver Creek and
the Holbrook tributary. It appears that the base flow is relatively low, usually less than 180
<' gallons per minute m most of which discharges from the Holbrook- tributary g p (gp ), g into Beaver
Creek. During high rainfall events, such as thunderstorms (estimated to be 60 — 70 days per
year), flows can be much greater.
3.5 SURFACE SOIL
No additional soil samples were collected during the supplemental investigation for the CMS.
Therefore, the conclusions from the RFI (SAIC 2004b) are still applicable. No VOCs were
identified as human health constituents of potential concern (HHCOPCs) in surface soil. Four
polyaromatic hydrocarbons (PAHs) (benzo(a)pyrene, benzo(ghi)perylene,
dibenzo(ah)anthracene, and phenanthrene) were identified as HHCOPCs in surface soil. Of
these, benzo(ghi)perylene .and phenanthrene were identified as HHCOPCs in surface soil by
default because there. were no EPA Region 9 residential soil preliminary remediation goals
(PRGs).(EPA 2003a).
These SVOCs were detected along roads and parking areas, which were located outside the
SWMU 103 source area. The RFI (SAIC 2004b) concluded the SVOCs in surface soil are the
result of surface runoff from these parking areas and roads and not attributable to SWMU 103
and, do not require further investigation or development of corrective measures in the CMS.
3.6 SUBSURFACE SOIL
Nine additional subsurface soil samples were collected from soil borings for the installation of
monitoring wells at SWMU 103 for the supplemental investigation (CY 2005) for the CMS. The
results from this supplemental investigation are discussed .in Appendix F. The subsurface soil
data set for SWMU 103 was reevaluated by adding the nine additional subsurface soil samples
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from the supplemental investigation for the CMS, removing data from subsurface soils
associated with the former heating -oil UST, and updating to the most current EPA Region 9
residential PRGs (October 2004). The new screening values are presented in Table 3-1. The data
making up this subsurface soil data set are presented in Appendix G, Table G-1.
Only one VOC (total xylenes) was identified as an HHCOPC in subsurface soil. Total xylenes
were detected in 6 of 33 subsurface soil samples with only 2 of the 6 slightly above the EPA
Region 9 residential PRG (27 milligrams per kilogram [mg/kg]). Subsequent to the RFI, SWMU
103 was limited to the contaminant release from the solvent UST, -and petroleum contaminants
are addressed under North Carolina UST regulations. The two detections of ethylbenzene above
the EPA Region 9 residential PRG in subsurface soil occurred in the soil interval just above the
water table (26 to 27 feet bgs at S138 and 28 to 30 feet bgs at 4PH40). Typically, only subsurface
soil data down to 10 feet bgs (the approximate maximum depth of a foundation for a house) are
evaluated to determine HHCOPCs for subsurface soil.
The conclusions presented in the SCM Report (SAIC 2004a) and RFI (SAIC 2004b) are still
applicable for subsurface soil associated with SWMU 103; HHCOPCs in the SWMU 103 source
area are infrequently detected and are located in the interval just above the water table. The low
level of contamination in subsurface soil at or below the water table at the SWMU 103 source
area is addressed in the CMS along with potential groundwater treatment in this area; therefore,
no separate corrective measures for the remediation of HHCOPCs in subsurface soil will be
required in the SWMU 103' source area.
3.7 GROUNDWATER
The groundwater dataset for SWMU 103 was updated by adding data from the supplemental
investigation for the CMS and removing data that was specific to the former heating -oil UST
area. This update included adding the VOC and SVOC results from groundwater collected in the
SWMU 103 source area in April 2005 and around Holbrook Elementary School in April 2005,
August 2005, and June 2006. VOC and SVOC data collected from well MW69344C were not
included in the data set because free product continues to accumulate in this well. In addition,
SVOC data from wells installed around the former heating -oil UST (MW41, MW42, MW43,
MW443 MW45 and MW46) were not included in the groundwater data set because the former
heating -oil USTs at Building 6-9344-A are the source of SVOCs (i.e., PAHs) in groundwater;
however, VOC data from these wells were included because chlorinated solvents in the
groundwater originate from the SWMU 103 site. In addition, groundwater samples (except for
the baseline sampling) collected to evaluate the performance of the in -situ pilot study were not
included because the samples were impacted by the injection of specialized bacteria, oxygen -
releasing compounds (ORCs), and nutrients.
Tables 3-2 and 3-3 present summary statistics for VOCs and SVOCs in groundwater,
respectively, using the updated groundwater data set. The updated groundwater data set is
presented in Appendix G, Table G-2.
3.7.1 Volatile Organic Compounds
Twenty-one VOCs were detected in the groundwater. Using the criteria developed in the RFI,
of the 21 VOCs, only 14 were detected above EPA Region 9 PRGs and/or the North Carolina 2L
standards and identified as HHCOPCs for potable use of groundwater. The 14 VOCs are:
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1,1,2,2-tetrachloroethane; 1,1,2-trichloroethane (TCA);. 1,2-dichloroethene (DCE); acetone;
benzene; chloroform; chloromethane; dibromochloromethane; ethylbenzene; MTBE;
tetrachloroethene; toluene; TCE; and total xylenes. These 14 VOCs are HHCOPCs in
groundwater at SWMU 103. Three VOCs (benzene, ethylbenzene, and TCE) were also detected
,above their respective maximum contaminant levels (MCLs). It should be noted that the only
VOCs that were eliminated from the list of site -related constituents (SRCs) from the SCM and
RFI were six VOCs detected once in groundwater collected from MW69344C, the monitoring
well located at.the former heating -oil UST in which free product continues to accumulate.
Of these 14 VOCs, four exceed the EPA Region 9 PRGs but are below the North Carolina 2L .
standards or the federal drinking water MCL; 1,1,2-TCA, 1,2-DCE, dibromochloromethane, and
toluene.. Since these contaminants do not exceed statutory groundwater or drinking water
standards for potable use, they were eliminated' as HHCOPCs for potable use during the CMS
process.
Ten VOCs exceed a potable use standard in at least one sample at SWMU 103. Of these 10
VOCS:
• Five are chlorinated compounds: 1,1,2,2-tetrachloroethane, TCE, chloroform,
chloromethane, and tetrachloroethene.
• Four are. associated with petroleum products: benzene, ethylbenzene, total xylenes, and
MTBE.
• One is non -chlorinated but not commonly associated with petroleum products: acetone.
The four chemicals associated with petroleum products,are excluded as SWMU 103 HHCOPCs
because they most likely resulted from releases from petroleum USTs that were removed under
North Carolina UST regulations: SWMU 103 is defined by a solvent tank release. Therefore the
contaminants associated with the petroleum USTs are addressed under North Carolina .UST
regulations, not the SWMU 103 RCRA process.
Acetone is a common laboratory contaminant and has a very short half-life in the
environment. It was detected above the North Carolina 2L standard in only one well (MW-11),
but was not detected in the subsequent sampling event. Acetone was therefore eliminated as an
HHCOPC for SWMU 103.
The primary contaminants in groundwater are chlorinated solvents. The highest
concentrations of chlorinated solvents are still measured in the deep surficial groundwater.
Although not regulated as part of SWMU 103, the highest concentrations of petroleum
contaminants are located in the shallow surficial groundwater:. The concentrations of chlorinated
solvents (and petroleum contaminants) exhibited a sporadic but slight decrease from previous
results.
In summary, 1,1,2,2-tetrachloroethane; chloroform; chloromethane; tetrachloroethene;
and TCE were retained as HHCOPCs in groundwater at SWMU 103 and evaluated of potential
corrective actions in the CMS.
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3.7.2 Semivolatile Organic Compounds
Eight SVOCs were detected in groundwater. Using the criteria developed in the RFI, of these
eight SVOCs, only three [2-methylnaphthalene, naphthalene, and bis(2-ethylhexyl)phthalate]
were detected above EPA .Region 9 tap water PRGs or the North Carolina 2L standards. 2-
Methlynaphthalene.was detected in 4 of 58 groundwater samples at SWMU 103; all four of the
detections exceed the EPA Region 9 tap water PRG, and three of the detections exceed the North
Carolina 2L standards. Naphthalene was detected in groundwater in 3 of 58 groundwater samples
with all three detections above the EPA Region 9 tap water PRG and the North Carolina 2L
standard. All of the detections of naphthalene and three of the detections of 2-methylnaphthalene
were at MW22, the shallow surficial groundwater well located in the area of the former Mallonee
Village Gas Station (SWMU 103). The remaining 2-methylnaphthalene concentration (1.9J
micrograms per liter [[tg/L]) was located at MW8, a shallow surficial groundwater well east of
the SWMU 103 source area; this concentration is below the North Carolina 2L standard.
The RFI concluded that 2-methylnaphthalene and naphthalene are contaminants associated
with SWMU 103 and are only located in the surficial groundwater in the area of the former
Mallonee Village Gas Station. However, these contaminants are associated with petroleum
products, and therefore probably resulted from releases from the petroleum USTs at the former
Mallonee Village Gas Station. The petroleum USTs were removed and remediated under North
Carolina UST regulations, and SWMU 103 is limited to the solvent release. Therefore 2-
methylnaphthalene and naphthalene were eliminated as SWMU 103 HHCOPCs in the CMS
process.
Bis(2-ethylhexyl)phthalate was detected in 12 of 58 groundwater samples with one of the
detected concentrations exceeding the EPA Region 9 tap water PRG and two exceeding the
North Carolina 2L standard. Bis(2ethylhexyl)phthalate is a common contaminant associated with
the manufacture of plastics and is a common laboratory contaminant. Bis(2-ethylhexyl)phthalate
is not associated with contamination originating from SWMU 103 but is more likely a common
background contaminant.
In summary, although 2-methylnaphthalene, naphthalene, and bis(2-ethylhexylphthalate) were
detected above North Carolina 2L standards, these chemicals are not associated with SWMU 103
and therefore are not HHCOPCs in groundwater at SWMU 103.
3.7.3 Distribution of Groundwater Contaminants
The highest concentrations of chlorinated solvents were detected in the deep portions (just
above the clay -confining unit) of the surficial water -bearing zone, while the highest
concentrations of petroleum -related constituents [benzene, toluene, ethylbenzene, and xylenes
(BTEX)] were detected in the shallow portion (at the water table) of the surficial water -bearing
zone.
The release of chlorinated solvents and petroleum products from the removed USTs at the
former Mallonee Village Gas Station was the primary source of contaminants in groundwater at
SWMU 103. The petroleum products were released from USTs that were removed and regulated
under North Carolina UST regulations. The chlorinated solvents were released from a solvent
UST that is the subject of the SWMU 103 CMS. No other sources have been identified for
SWMU 103 contamination. It has been hypothesized that in the past, a light, nonaqueous-phase
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liquid (LNAPL) and a dense, nonaqueous-phase liquid (DNAPL) might have been present during
the initial phase of the past release (more than 30 years ago); however, the concentrations of
constituents detected to date have not indicated the existence of a free -phase LNAPL or DNAPL
in the subsurface.
Most VOCs associated with chlorinated solvents have migrated significantly beyond the
SWMU 103 source area. Distribution of these VOCs was assessed relative to North Carolina 2L
standards as a threshold:
1,1,2,2-Tetrachloroethane is the chlorinated solvent detected most often and at the highest
concentrations. It exceeded the North Carolina 2L standard in at least one sample in 47 of
53 wells. The highest concentrations (>250 µg/L) are generally deeper wells clustered
around the former gas station source area (IW1, IW2, IW3, MW6, MW23, MW48, and
MW50), but also include a few wells to.the east (MW9 and MW12) and south (MW41
and MW42). The higher levels of 1,1,2,2-tetrachloroethane in MW9 and MW12 probably
represents contaminant migration in the clay trough toward Holbrook tributary. The
higher levels of 1,1,2,2-tetrachloroethane in MW41 and MW42 (as well as detections at
concentrations >100 µg/L in wells further south) likely represent migration around and
over the clay ridge with the hydraulic gradient.
• TCE is generally the next most widely distributed contaminant, and exceeds its North
Carolina 2L .standard in 31 of 53 wells. Its concentrations are highly correlated .with,
though lower than, 1,1,2,2-tetrachloroethane (the TCE concentration is usually about 5%
to 20% of the 1,1,2,2-tetrachloroethane concentration). This correlation is evidence of a
r common source and migration pathways.
• Tetrachloroethene was detected above its North Carolina 2L standard in 14 of 53 wells. It
is also well correlated with 1,1,2,2-tetrachloroethane but at much lower concentrations
(highest detection was 3.2 µg/I, in MW12). Although tetrachloroethene exceeds North
Carolina 2L standards, it never exceeds its MCL.. The tetrachloroethene was likely
released and migrated with 1,1,2,2-tetrachloroethane and TCE..
• Chloromethane was detected above its North Carolina 2L standard in 9 of 53 wells. The
highest concentration was 6.9 µg/L in MW6. Generally its detection locations correlate
poorly with those of 1,1,2,2-tetrachloroethane, TCE and PCE. It is more commonly found
in shallow wells, often near Beaver Creek. It is not clear if chloromethane originated from
the SWMU 103 solvent tank.
• Chloroform was detected above its North Carolina 2L standard in only one sample from
shallow source well MW22. Although chloroform exceeds North Carolina. 2L standards,
it never exceeds its MCL.
The distribution of VOC contaminants demonstrate that _1,1,2,2-tetrachloroethene, TCE, and
PCE share a common source (the solvent UST at the former gas station) and common migration,
pathways. It is possible but uncertain whether chloromethane and chloroform were also released
from the solvent UST. 1,1,2,2-Tetrachloroethane and TCE are the' most widespread
contaminants and are present in concentrations several orders of magnitude above the North
Carolina 2L standards, and therefore will have the greatest influence on the clean-up approach
-r and time until standards are met.
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To explain the higher concentrations of chlorinated solvents in deeper portions of the
Middendorf aquifer, the RFI hypothesized that in the past (more than 30 years ago) a DNAPL
(chlorinated solvent) might have been released from SWMU 103 that could have migrated to the
top of the clay -confining unit and dispersed across the top of the clay, with a portion adsorbed to
the surface of the clay, which acts as a continuous source by dissolution to the deep surficial
groundwater. This hypothesis seems unlikely because contaminant concentrations are too low to
indicate the presence of DNAPL. Also, subsurface soil samples of the clay from the Cape Fear
confining layer indicated concentrations of chlorinated solvents (see Section 4.9.6 of the SCM
Report), but groundwater modeling did not reproduce comparable groundwater concentrations.
This argues against a historic DNAPL pool on the clay surface.
The former Mallonee Village Gas Station was located just upgradient of an elevated high in
the clay -confining unit (Cape Fear confining unit). Dissolved contaminants in the more shallow
portions of the surficial groundwater could flow over the clay "ridge" so that dissolved
contaminants could easily migrate with groundwater to the south (toward MW41 and MW42).
However, dissolved contaminants in deeper .groundwater (in the trough) are prevented from
migrating south by the clay high. Groundwater (and dissolved contaminants) may be relatively
stagnant in the trough, or may be directed eastward toward the Holbrook tributary (and MW9
and MW12). Matrix diffusion theory supports the conceptual model that dissolved contaminants
could diffuse and adsorb into the Cape Fear clay, and diffusion back out of this clay could
support the higher concentrations of VOCs found in the deeper portions of the surficial
groundwater, particularly if advective transport in this zone is relatively slow. Therefore,
whether the original source material was DNAPL, or more likely dissolved -phase solvents, the
underlying Cape Fear clay formation plays an important role in the conceptual site model.
The concentrations of chlorinated solvents measured to date do not indicate the presence of
free -phase DNAPL. The groundwater data for April 2005 and June 2006 indicate a possible
decreasing trend since January 2003 at the SWMU 103 source area (former Mallonee Village
Gas Station) due to natural attenuation and/or seasonal variations. Figure 3-1 illustrates that
concentrations of 1,1,2,2-tetrachloroethane show a decreasing trend in deep wells MW12,
MW23 and MW48. Concentrations of TCE appear to be relatively stable.
3.7.4 Potential Groundwater Contamination Upgradient of SWMU 103
Low concentrations of 1,1,2,2-tetrachloroethane; TCE; and chloroform have been detected to
date in groundwater from site -specific background wells north of Honeycutt Road MW26 and
MW27. MW26 and MW27 were installed because groundwater in the original background wells,
MW10 and MWl1, also contained chlorinated solvents. In addition, low concentrations of four
VOCs (1,1,2,2-tetrachloroethane; .chloroform; toluene; and TCE) were detected at the water
table, and six VOCs (1,1,2,2-tetrachloroethane; 1,2-DCE; toluene; TCE; cis-1,2-DCE; and trans-
1,2-DCE) were detected in the deep groundwater samples (just above the clay) collected from
temporary sampling locations in the residential area located north of SWMU 103 and Honeycutt
Road (as far as approximately 2,800 feet north of SWMU 103). 1,1,2,2-Tetrachloroethane was
detected at concentrations above the North Carolina groundwater standards [15A NCAC 2L,
NCDENR 2002] in wells MW26 and MW27.
The chlorinated solvents in the groundwater north of Honeycutt Road are most likely from
SWMU 103, because the relative proportion of solvent concentrations (particularly the ratio of
1,1,2,2-tetrachloroethane to TCE) is the same (this is most clearly seen in MWl 1).
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It is possible that deep groundwater in the clay trough (Figure 2-4) is relatively stagnant and
that contaminants have traveled by diffusion or mixing northward in the trough from the former
gas station. However, the residential area is north of the point at which the clay begins to
increase in elevation as it approaches MW27, the site -specific deep background well. It seems
unlikely that contaminants from SWMU 103 would be impacting groundwater this far upgradient
of the SWMU 103 source area. However, low. levels of VOCs characteristic of SWMU 103
chlorinated solvents are present in groundwater upgradient of SWMU 103.
3.7.5 Potential Contamination Migrating Under Beaver Creek
The groundwater results from SWMUs 4 and 18 do not indicate that the contamination
present in groundwater located at SWMU 103 is migrating below Beaver Creek. Some common
constituents (i.e., chlorinated solvents and their degradation products) are present both east and
west of the creek; however, much higher levels would be detected west of Beaver Creek if
significant levels of contaminants, specifically 1,1,2,2-tetrachloroethane and TCE and their
degradation products, were migrating beneath Beaver. Creek.
The shallow and deep surficial groundwater flow from SWMU 103..is in a southwesterly
direction toward Beaver Creek. In addition, there is a slight upward vertical gradient associated
with the well pairs located along Beaver Creek (MW1/MW2 and MW18/1\4W19), suggesting
that groundwater movement is upward toward the shallower portion of the aquifer, which is
connected to the surface water of Beaver Creek. Tetrachloroethene; TCE; 1,1,2,2-
tetrachloroethane; chloroform; chloromethane; and cis-1,2-DCE have been detected in surface
water and sediment in Beaver Creek.
Available information indicates that chlorinated solvent contaminants.and/or their degradation
products in groundwater from SWMU 103 are intercepting- the surface water in Beaver Creek
and the Holbrook tributary.
3.7.6 Natural Attenuation of Chlorinated Solvents in Groundwater
Figure 3-2 presents the chemical and biological breakdown pathways for the predominant
contaminants in groundwater at SWMU 103. Breakdown products of 1,1,2,2-tetrachloroethane
and TCE such as cis-1,2-DCE, trans-1,2-DCE; and 1,1,2-TCA have historically been
infrequently detected at low concentrations in the shallow source area groundwater, indicating
that reductive dechlorination of 1,1,2,2-tetrachloroethane may have occurred when the solvents
and fuels were co -mingled after release. The lack of migration of these daughter products from
the source area is noteworthy. Groundwater geochemical data collected during the course of site
investigations at SWMU 103 indicate that natural conditions beneath the site are aerobic,, with
DO concentrations ranging from 4 to 8 milligrams per liter (mg/L) and ORPs ranging from +100
to +350 millivolts. In addition, competing electron acceptors such as sulfate and nitrate are
present at concentrations that will limit anaerobic dechlorination. However, these electron
acceptors do not represent an obstacle to reductive dechlorination of 1,1,2,2-tetrachloroethane
when adequate carbon substrate is available.
Review of SWMU 103 site data collected in the vicinity of the source area from monitoring
well pairs MW22/23. and MW6/7 is instructive to assess past natural attenuation processes and
the current distribution of contaminants.. At both well clusters high concentrations of fuel
compounds have .been detected at the shallow wells (MW7 and MW22), but significant
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concentrations of fuel compounds are absent at both deep wells (MW6 and MW23). It appears
that the chlorinated solvents and fuels originally leaked from USTs and the solvents sank through
the unsaturated and saturated zones as a DNAPL, possibly reaching the top of the Cape Fear
Formation clay. Early in the spill history we can assume that 1,1,2,2-tetrachloroethane
concentrations at the shallow wells (MW7 and MW22) were similar to or even greater than
1,1,2,2-tetrachloroethane concentrations at the deeper wells today (MW6 and MW23). A
comparison of the chlorinated solvent concentrations present in the shallow and deep wells in
recent years indicates the impact of fuel -related organic carbon on 1,1,2,2-tetrachloroethane and
TCE degradation. Solvent and fuel VOC data collected in January 2003 are summarized in Table
3-4.
Groundwater analytical data collected from the deep wells (MW6 and MW23) indicate that
1,1,2,2-tetrachloroethane and TCE are present at relatively high concentrations in the absence of
BTEX. Conversely, BTEX compounds are present at relatively high concentrations at the
shallow wells (MW7 and MW22) while 1,1,2,2-tetrachloroethane, PCE, and TCE are present at
very low concentrations or are non -detect. These data clearly indicate that, in the presence of
elevated concentrations of organic carbon sources (i.e., fuel hydrocarbons), 1,1,2,2-
tetrachloroethane and TCE are anaerobically biodegraded without the sustained accumulation of
daughter products cis 1,2-DCE and vinyl chloride.
3.8 VAPOR INTRUSION
In addition to screening against potable use criteria (i.e., Region 9 PRGs and/or North
Carolina 2L standards), chemicals detected in groundwater were evaluated for their potential to
migrate to indoor air at Holbrook Elementary School. The vapor intrusion evaluation included in
the SCM Report (SAIC 2004a) is based on EPA's Office of Solid Waste and Emergency
Response (OSWER) Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway
from Groundwater and Soils (Subsurface Vapor Intrusion Guidance) (EPA 2002). Since the
vapor intrusion evaluation in the SCM Report (SAIC 2004a) was completed, two actions have
occurred:
• New monitoring wells (MW41 and MW42) were installed near Holbrook Elementary
School and additional data were collected from the new and existing monitoring wells in
April 2005, August 2005 and June 2006.
• Eighteen permanent soil gas monitoring points were installed around the perimeter and
between the buildings comprising Holbrook Elementary School. Samples were collected
from all soil gas monitoring points as well as two crawlspaces under the school in June
2006.
The soil gas and crawlspace air sampling in June 2006 showed that VOCs are not migrating
from groundwater to the school via, vapor intrusion to any measurable extent. Several
contaminants (primarily alcohols, ketones, and petroleum contaminants) were detected in soil
gas and crawlspace air samples, but most have not been detected in groundwater near Holbrook
Elementary School. The primary contaminants in groundwater, 1,1,2,2-tetrachloroethane and
TCE, were not detected in any of the air samples. There were only three contaminants, acetone,
chloroform and tetrachloroethene, that were detected both in groundwater and soil
gas/crawlspace air samples. However, if these contaminants were in the air samples due to
volatilization and vapor transport from groundwater, 1,1,2,2-tetrachloroethane and TCE would
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also have been present. Therefore, it was concluded that vapor intrusion of groundwater
contaminants is an incomplete, or at least insignificant, pathway. The details of this analysis are
in Appendix F.
Nevertheless, the 2006 data were used to evaluate risk of vapor intrusion. The maximum
concentrations of volatile constituents detected in groundwater in April 2005, August 2005, and
June 2006 from shallow monitoring wells (MW35, MW37, and MW42) located closest to
Holbrook Elementary School and results of crawl space and soil gas samples from Holbrook
Elementary School in June 2006 (Figure 2-13) were evaluated using the EPA (2002) draft
guidance, and the results are presented in the following'sections.
3.8.1 Tier I Screen
The groundwater at SWMU 103 failed the Tier I screen because seven organic chemicals
detected in shallow monitoring wells MW35, MW37, and/or MW42 (acetone, chloroform;
dibromochloromethane; 1,2-DCE; 1,1,2,2-tetrachloroethane; tetrachloroethene; and TCE) meet
the criteria of being sufficiently volatile and toxic. Therefore, 'a Tier II screen was performed.
3.8.2 Tier II Screen
All of the VOCs identified in the Tier I screening were eliminated as potential vapor intrusion
risks based on Tier II screening. A summary of the screening levels and monitoring results is
presented in Table 3-5. Screening results for individual chemicals are described below.
(l Of the seven VOCs detected in groundwater, only three, acetone, chloroform and PCE were
detected. in any soil gas . or crawlspace air samples. Due .. to the incomplete pathway,
dibromochloromethane, 1,2-DCE, 1,1,2,2-tetrachloroethane and, TCE were eliminated as
potential vapor intrusion risks. Note .that dibromochloromethane and 1,2-DCE concentrations in
groundwater were below the 10-6 risk level for vapor intrusion.
Acetone was detected at low concentrations in crawlspace air samples (3 of 3), soil gas
samples (18 of 20), and groundwater. samples (3 of 10). All detections were below target
concentrations. Therefore, acetone is eliminated as a potential vapor intrusion problem at
Holbrook Elementary School.
Chloroform was detected at low concentrations in groundwater (5 of 10) samples, but
concentrations were low enough 'to satisfy the 10-6 risk level for vapor intrusion. Chloroform
was not detected in any crawlspace air samples, but was detected in 4 of.20 deep soil gas
samples. Three of the four detections and all 16 non -detections were low enough to satisf6y the
10-6 risk level. Concentrations in only one of the 20. soil gas samples exceeded the 10- risk
level; that exceedance satisfied the 10-5 risk level for chloroform. Therefore chloroform is not
expected to be a vapor intrusion problem at Holbrook Elementary School.
Tetrachloroethene was detected at low concentrations in crawlspace air samples (1 of 3), soil
gas samples (4 of 20), and groundwater sam6ples (3 of 10). Concentrations in all groundwater
and soil gas samples were below the 10- risk level targets. The concentrations in one
crawlspace sample exceeded the 10-6 risk level, but satisfied the 10-5 risk level for
tetrachloroethene. Therefore tetrachloroethene is not expected to be a vapor intrusion problem at
Holbrook Elementary School.
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In summary, results indicate that there is currently no threat of vapor intrusion from VOCs in
groundwater into Holbrook Elementary School. Since only one round of soil gas monitoring has
been conducted to date, continued monitoring at Holbrook Elementary School is prudent to
ensure that there is no threat to human health.
3.9 SURFACE WATER AND SEDIMENT
Surface water samples were collected in Beaver Creek and the Holbrook tributary in March
2006 to update the nature and extent of surface water contamination and to determine the extent
of groundwater contamination intercepting these. surface water bodies. Four samples (SW1,
SW3, SW5, and SW6) were collected in Beaver Creek and ten samples (SW2, SW4, SW7, SW8,
S W9, S W 10, S W l 1, S W 12, S W 13, and S W 14) were collected in the Holbrook tributary. The
results from this supplemental investigation of surface water are discussed in Appendix F. The
results indicate that VOCs characteristic of the contaminants in groundwater at SWMU 103
continue to migrate to surface water in Beaver Creek and the Holbrook tributary at levels above
the North Carolina surface water standards. The 1,1,2,2-tetrachloroethane concentrations in
surface water in the Holbrook tributary continue to exceed the North Carolina surface water
standards for this VOC. 1,1,2,2-Tetrachloroethane concentrations in Beaver Creek exceed the
North Carolina surface water standards downstream of where the Holbrook tributary discharges
into it. The supplemental surface water data collected in March 2006 confirmed the conclusions
of the SCM, as summarized below.
The SCM (SAIL 2004a) determined that groundwater contamination originating from SWMU
103 and intercepting Beaver Creek and the Holbrook tributary is the source of chlorinated VOC
contamination in surface water and sediment in Beaver Creek and the Holbrook tributary.
Conversely, SVOCs identified as HHCOPCs in surface water and sediment were not attributed to
SWMU 103. SVOCs were primarily detected at SW6, a surface water/sediment sampling
location that is directly downstream of a 36-in.-diameter stormwater pipe outfall that traverses
the northern portion of SWMU 4 and receives stormwater drainage from Knox Street. The
stormwater outfall is the main contributing factor to the elevated levels of SVOCs detected at
this location. The SVOCs in surface water and sediment are most likely from the asphalt of Knox
Street and petroleum products leaking from automobiles traveling along the street. In addition,
SVOCs were detected in sediment at the background locations in Beaver Creek, indicating that
there is an upstream contribution to SVOC contaminants in sediment other than runoff from
SWMU 103 into Beaver Creek. Table 3-6 presents the HHCOPC screening for VOC SRCs from
the RFI.
3.9.1 Surface Water
1,1,2,2-Tetrachloroethane was identified as the only HHCOPC in surface water in Beaver
Creek and the Holbrook tributary. Several other VOCs were detected in surface water, but all
were below North Carolina surface water standards. Acetone was also eliminated as a surface
water HHCOPC at the CMS stage because it is not a groundwater HHCOPC. The VOC
HHCOPC will require evaluation of potential corrective action in the CMS.
Surface water base flow in Beaver Creek at Knox Street appears to be approximately 180
gpm. The concentration of 1,1,2,2-tetrachloroethane in Beaver Creek at Knox Street during base
flow conditions appears < 8.6 µg/L, which is just above its North Carolina surface water standard
of 4 µg/L.
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3.9.2 Sediment
Eight sediment HHCOPCs were identified for Beaver Creek and three sediment HHCOPCs
were identified for the.Holbrook tributary (all SVOCs) (SAIC 2004b). As discussed previously,
the SVOCs were determined not to be originating from SWMU 103; therefore, there are no
HHCOPCs in sediment.
3.10 ECOLOGICAL RISK ASSESSMENT
SWMU 103 is comprised of an asphalt parking lot, concrete pad, and gravel area with no trees
and a few decorative shrubs; therefore, with the concurrence of NCDENR, there is no significant
surface soil habitat for ecological receptors at SWMU 103 proper. Ecological COPCs (ECOPCs)
were identified in surface water and sediment as shown below.
Surface Water. Toluene and bis(2-ethylhexyl)phthalate are ECOPCs in surface water.
Sediment. Seven VOCs [..1,1,2,2-tetrachloroethane; 2-butanone; 4-methyl-2-pentanone;
acetone; toluene; TCE; and total xylenes] and 16 SVOCs [3+4-methylphenol, anthracene,
benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(ghi)perylene,
benzo(k)fluoranthene, benzoic acid, bis(2ethylhexyl)phthalate, carbazole, chrysene,
dibenzo(ah)anthracene, fluoranthene, indeno(1,2,3-cd)pyrene, phenanthrene, and pyrene] are
considered ECOPCs in sediment.
Although all of these contaminants were included in the ecological risk analysis, it is noted
..N that only two, 1,1,2,2-tetrachloroethane and TCE, can specifically be attributed to the SWMU
103 solvent UST release. Groundwater contamination originating from SWMU 103 and
intercepting Beaver Creek and the Holbrook tributary is the source of chlorinated solvent
contamination in surface water and sediment in Beaver Creek and the Holbrook tributary.
SWMU 103 is not the source of SVOC contamination in surface water and sediment. SVOCs
were primarily detected at SWS6, a surface water/sediment location that is directly downstream
of a 36-in.-diameter stormwater pipe outfall that traverses the northern portion of SWMU 4 and
receives stormwater drainage from Knox Street. The stormwater outfall is the main contributing
factor to the elevated levels of SVOCs detected at this location. The SVOCs in surface water and
sediment are most likely. from the asphalt of Knox Street and petroleum products leaking from
automobiles traveling along the street. In addition, SVOCs were detected in sediment at the
background locations in Beaver Creek, indicating there is an upstream contribution to SVOC
contaminants in sediment other than runoff from SWMU 103 into Beaver Creek.
Only VOCs originating from groundwater migrating from SWMU 103 are ECOPCs in
surface water and sediment. Corrective measures evaluated to remediate HHCOPCs in
groundwater at SWMU 103 will reduce/eliminate constituents identified as ECOPCs in surface
water and sediment; therefore, no specific corrective measures are evaluated in the CMS for
ECOPCs.
3.11 FATE AND TRANSPORT
A contaminant F&T analysis presented in the SCM Report (SAIC 2004a) assessed how
representative compounds detected at SWMU 103 could be transported in' the environment and
their potential fate. It also evaluated the potential for contaminants in subsurface soil to leach to
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groundwater by a comparison to the North Carolina soil screening levels (SSLs) to identify
contaminant migration constituents of potential concern (CMCOPCs). The following F&T
section updates the F&T analysis using the updated sampling and analysis conducted in 2005 and
2006. The previous contractor, SAIC, developed a numerical model that is presented in
Appendix K.
3.11.1 Soil Screening Level Evaluation
The contaminants detected (i.e., SRCs) in the updated subsurface soil data set (Table 3-1) for
SWMU 103 were evaluated for their potential to migrate to groundwater by comparing the
maximum concentrations in subsurface soil to North Carolina SSLs (Table 3-7).
Five VOCs (1,1,2,2-tetrachloroethane; benzene; chloroform; ethylbenzene; and total xylenes)
exceeded their respective North Carolina SSLs (Table 3-7). 1,1,2,2-Tetrachloroethane exceeded
its North Carolina SSL in 2 of 2 detections out of 33 subsurface soil samples. Benzene exceeded
its North Carolina SSL in 1 of 3 detections out of 33 subsurface soil samples. Chloroform
exceeded its North Carolina SSL in 1 of 4 detections out of 33 subsurface soil samples.
Ethylbenzene exceeded its North Carolina SSL in 2 of 5 detections out of 33 subsurface soil
samples. Total xylenes exceeded its North Carolina SSL in 2 of 6 detections out of 33 subsurface
soil samples. However, benzene, ethylbenzene, and total xylenes are associated with petroleum
products and not the solvent UST release that comprises SWMU 103. Therefore 1,1,2,2-
tetrachloroethane; and chloroform are CMCOPCs in subsurface soil. All of the VOCs that
exceeded their respective North Carolina SSL in .subsurface soil were indicated as SRCs in
groundwater at SWMU 103. All of the VOC concentrations exceeding North Carolina SSLs
were located at or within the immediate area of the former Mallonee Village Gas Station. Most
of the VOCs exceeding the North Carolina SSL were located at or just above the water table (>
25 feet bgs).
1,1,2,2-Tetrachloroethane; and chloroform are identified as CMCOPCs in subsurface soil at
SWMU 103. These contaminants were infrequently detected and are located at or just above the
water table; therefore, as concluded by the SCM (SAIC 2004a), these contaminants are not
significantly contributing to the SWMU 103 source area groundwater contamination. The
contaminants are not colocated with the highest concentrations of contaminants in groundwater,
and modeling in the SCM Report indicated that the currently observed groundwater
concentrations is not the result of measured contamination in the subsurface soil. The subsurface
soil contamination at or just below the water table represents a depleted source. The low level of
contamination in subsurface soil at or below the water table at the SWMU 103 source area will
be addressed with potential groundwater treatment in this area in the CMS; therefore, no further
evaluation is required for CMCOPCs in subsurface soil in the SWMU 103 source area.
3.11.2 Natural Attenuation Modeling
This section presents the methods and results of the update of F&T modeling used to evaluate
the migration of the primary COC (1,1,2,2-tetrachloroethane) from SWMU 103. This work was
conducted by the previous contractor, SAIC.
F&T modeling was updated based on the supplemental investigation performed in CY 2005.
Results from previous F&T modeling (SAIC 2004a) indicated that the maximum observed
concentration in groundwater was approximately an order of magnitude higher than the
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maximum concentration that would result from leaching of the observed soil concentrations as
predicted by SEasonal Flow and Transport Model for the Unsaturated SOIL Zone (SESOIL) and
Analytical Transient 1-, 2-, 3-Dimensional (AT123D) modeling. Also, the supplemental
investigation performed in CY 2005 did not identify a soil zone with higher concentrations than
what was observed in the past. Therefore, the updated F&T analysis only involves the observed
groundwater concentration, which is identified as the primary source of contamination at this
site. The detailed numerical modeling approach, assumptions, and results are presented in
Appendix K. A summary of the numerical model and the results is presented below.
The numerical model was set up using a Modular Three -Dimensional Groundwater Flow
Model (MODFLOW) . simulator at a scale corresponding -to a 100-foot grid spacing and
populated with information from the SCM. The final values for the hydraulic conductivity,
recharge, and constant -head boundary conditions were set through calibration to observed
groundwater level data for April 2005, and are presented in Appendix K. The calibrated model
can simulate average, steady-state conditions on a scale of approximately 100-foot grid spacing.
The calibrated model was then used to simulate groundwater flow under average, steady-state
conditions. The model was also used to predict natural attenuation of 1,1,2,2-tetrachloroethane
by coupling MODFLOW-simulated flow fields with the Modular Three -Dimensional Multi -
Species Transport Model (MT3DMS). Flow simulations were conducted assuming current
conditions. The initial condition of the plume was set by using the most recent observed
concentrations. The groundwater was divided into two layers: one representing the shallow
surficial groundwater (Layer 1) and one representing the deep surficial groundwater (Layer 2).
Groundwater concentrations, tend to vary with depth with the higher concentrations of
chlorinated solvents toward the deeper groundwater. To avoid overestimating the, mass of
contamination at the site, an average concentration for each layer was determined from the most
recent sampling results. The initial concentration for Layer 1 was an average of the shallow well
concentrations and the calculated 'concentration at the Layer 1/Layer 2 interface. Similarly, the
initial- concentration for Layer 2 was an average of the calculated concentration at the Layer
1/Layer 2 interface and the deep well concentrations (please see the discussion in Appendix K).
The calibrated model encompasses an area of approximately 92 acres with a contaminant mass of
approximately 77.56 kg of 1,1,2,2-tetrachloroethane within the dissolved plume.
The biological degradation half-life was assumed to be very conservative as described below
(i.e., 7.9 years).and was consistent with previous modeling efforts for SWMU 103. The fate of
the 1;1,2,2-tetrachloroethane (primary COC in groundwater) was simulated over a period of 100
years at target concentrations associated with specific receptors. These target concentrations and
resulting mass removal required to achieve the target concentrations are presented in the
following bullets:
5 µg/L: the groundwater concentration of 1,1,2,2-tetrachloroethane identified in the site -
specific background location (MW27), requiring a removal of approximately 77.18 kg of
1,1,2,2-tetrachloroethane (99.5% removal).
• 4 µg/L: remedial level for 1,1,2,2-tetrachloroethane in surface water, which is equal to the
North Carolina surface water standard criterion for 1,1,2,2-tetrachloroethane identified to
be protective of surface water, requiring a removal of approximately 77.29 kg of 1,1,2,2-
tetrachloroethane (99.6% removal).
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• I µg/L: the analytical reporting level for 1,1,2,2-tetrachloroethane, requiring a removal of
approximately 17.53 kg of 1,1,2,2-tetrachloroethane (99.96% removal).
• 0.17 µg/L: remedial level for 1,1,2,2-tetrachloroethane in groundwater, which is. equal to
the North Carolina 2L standard, requiring a removal of 77.56 kg of 1,1,2,2-
tetrachloroethane (100% removal).
Concentration -over -time plots at strategic receptor locations were developed. Receptor
exposure points were selected at various distances downgradient from the source areas and at
probable discharge points in Beaver Creek and/or the Holbrook tributary. These locations were
selected based on the points of maximum detected concentrations in Beaver Creek and the
Holbrook tributary, and selected downgradient groundwater locations. Time periods were
estimated to achieve the various target levels (e.g., 5, 4, 1, and 0.17 µg/L) at the receptor
exposure points. The natural attenuation time to achieve each target level is summarized in Table
3-8. The estimated natural attenuation period to achieve the North Carolina 2L standard (0.17
µg/L) for tetrachloroethane is 60 years from CY 2005, and the period to achieve the North
Carolina surface water standard (4 µg/L) for 1,1,2,2-tetrachloroethane is 33 years from CY 2005.
Contaminant is removed by advection, discharge to surface water, and the modeled decay
function.
While the modeling effort provides a useful estimate of the natural attenuation period, it is
important to acknowledge the uncertainty associated with the estimate. There are several sources
of uncertainty:
The natural attenuation decay rate for 1,1,2,2-tetrachloroethane was chosen based on
literature values, and in order to be conservative, a value toward the lower end of the
range of suggested values was selected for use. Although the selected value (half life of
7.9 years) is considered to be conservative, the value is not validated for SWMU 103. Site
wide, groundwater samples have only been analyzed from July 2000 through June 2006
(less than 6 years), and no single site well has been sampled for that entire period. This
timeframe is too short to validate the decay rate.
The model assumed that all contaminant mass is, present in the primary flow zones
(Layers 1 and 2). However, the Site Conceptual Model speculates that diffusion out of the
lower Cape Fear Formation clay layer is acting a continuing source of contamination.
Sufficient data are not available to quantify a mass flux of 1,1,2,2-tetrachloroethane from
the clay into the overlying aquifer. If diffusion from clay is a significant source of
contamination, the model may have underestimated the required natural attenuation
period.
• Although 1,1,2,2-tetrachloroethane is detected in the site -specific background location (5
µg/L in MW27), no upgradient flux of contamination is included in the model. The
natural attenuation period required to achieve RGOs below the site -specific background
concentration is uncertain.
• The North Carolina 2L standard for 1,1,2,2-tetrachloroethane (0.17 µg/L) is below the
analytical detection limit for that chemical. It will be difficult to determine if the North
Carolina 2L standard is met.
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3.12 NATURE AND EXTENT OF CONTANIINATION AND HUMAN HEALTH
CONSTITUENTS OF POTENTIAL CONCERN
Figure 3-3 presents the estimated horizontal extents of groundwater and surface water
contamination based on the latest groundwater data from each well and surface water sampling
point using 1,1,2,2-tetrachloroethane and TCE as representative chemicals for chlorinated
solvents. The areal extents of 1,1,2,2-tetrachloroethane and TCE contamination are
approximately 92 and 74 acres, respectively. The chlorinated solvent contamination permeates
the entire groundwater column with the higher concentrations located in the deep surficial
groundwater. Contaminants in groundwater are being intercepted by Beaver Creek and the
Holbrook tributary. Figure 3-4 summarizes the contaminants and the migration pathways and
SCM for SWMU 103. Table 3-9 presents the final HHCOPCs in groundwater and surface water
requiring development of RGOs and evaluation of potential corrective actions in a CMS.
3.13 DEVELOPMENT OF REMEDIAL GOAL OPTIONS
The RFI (SAIC 2004b) and the supplemental investigation for the CMS identified COPCs for
potable use (HHCOPCs) and vapor intrusion COPCs in groundwater and HHCOPCs in surface
water requiring potential corrective action. Vapor intrusion COPCs have subsequently been
eliminated as a result of the soil gas and crawlspace air monitoring in June 2006. Table 3-9
presents a summary of COPCs requiring the development of RGOs. RGOs were calculated to
assist in risk management decisions and to establish a range of values from which site remedial
levels could be established. RGOs were developed for HHCOPCs in groundwater and surface
water. A summary of each medium is presented below.
Surface Soil. Semivolatile HHCOPCs identified in surface soil were detected at spots along
roads and parking areas that'were located outside the SWMU 103 source area. The SVOCs in
surface soil are the result of surface runoff from these parking areas and roads and are not
attributable to SWMU 103.
Subsurface Soil. HHCOPCs and volatile CMCOPCs in the SWMU ' 103 source area are
infrequently detected and are located just above the water table. The low level of contamination
in subsurface soil at or below the water table in the SWMU 103 source area will be addressed
with potential groundwater treatment in this area as evaluated in the CMS. Therefore, no separate
corrective measures for the remediation of HHCOPCs or CMCOPCs in subsurface soil will be
required in the SWMU* 103 source area.
Groundwater. Volatile HHCOPCs are present in groundwater originating from the SWMU
103 solvent tank release, at the former Mallonee Village Gas Station and require potential action.
HHCOPCs were identified as those chlorinated solvent contaminants whose maximum
concentration exceeded either the North Carolina 2L or IMAC Standard. The HHCOPCs in
groundwater requiring potential corrective action are: 1,1,2,2-tetrachloroethane; chloroform;
chloromethane; tetrachloroethene; and TCE.
Surface Water and Sediment. Only VOCs originating from groundwater migrating from
SWMU 103 were considered as potential HHCOPCs in surface water. No VOCs. were indicated
as HHCOPCs in sediment. The only HHCOPC in surface water requiring potential corrective
action is 1,1,2,2-tetrachloroethane.
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Corrective measures evaluated to remediate volatile HHCOPCs in groundwater at SWMU
103 will reduce/eliminate constituents identified as HHCOPCs in surface water in Beaver Creek
and the Holbrook tributary.
3.13.1 Groundwater Remedial Goal Options
RGOs for the use of groundwater as a potable water supply were developed as described
below.
3.13.1.1 Potable Use RGOs
The North Carolina groundwater standards (15A NCAC 2L) and North Carolina groundwater
interim standards were chosen as the recommended RGOs for potable use of groundwater. Table
3-10 presents the recommended RGOs and final COCs identified in groundwater. 1,1,2,2-
Tetrachloroethane; chloroform; chloromethane; tetrachloroethene and TCE are COCs for potable
use of groundwater.
3.13.1.2 Uncertainty
Important sources -of uncertainty associated with using RGOs in establishing remedial levels
for groundwater at SWMU 103 are discussed below.
Background VOC Concentrations
As discussed in the SCM (Section 3.7.4), low levels of chlorinated solvent contamination are
present upgradient of SWMU 103. Specifically, 1,1,2,2-tetrachloroethane; TCE; and chloroform
consistently are detected at -the deep surficial site -specific background location (MW26) and
1,1,2,2-tetrachloroethane and chloroform continue to be detected in the shallow surficial site -
specific background location (MW27). The most current groundwater data (CY 2005) indicate
concentrations of 1,1,2,2-tetrachloroethane; TCE; and chloroform of 5.1, 0.6J, and 2.3 µg/L,
respectively, in the deep surficial background groundwater and concentrations of 1,1,2,2-
tetrachloroethane and chloroform of 1.1 and 1.2 µg/L, respectively, in the shallow surficial
background groundwater. 1,1,2,2-Tetrachloroethane concentrations are above the North Carolina
2L standard. The upgradient groundwater will continue to impact groundwater at SWMU 103
and interfere with obtaining a remedial level below the concentration levels measured at the
background locations. However, no sources of 1,1,2,2-tetrachloroethane other than the former
Mallonee Village gas station have been identified. The relative proportions of "background"
VOC contamination are the same as those at the SWMU 103 source area (former gas station).
Analytical Detection Level
The North Carolina 2L standard for 1,1,2,2-tetracholoroethane is 0.17 µg/L. The analytical
reporting level for 1,1,2,2-tetrachloroethane is 1 µg/L. Analysis to less than 1 µg/L represents an
uncertainty because concentrations below this value would be indicated as estimated by the
analytical laboratory. Therefore, remediation of COC concentrations to the North Carolina 2L
standard would be difficult to measure.
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3.13.2 Surface Water
The recommended RGOs for surface water are the North Carolina surface water standards.
The RGOs were selected using a process similar to the HHCOPC screening performed in the RFI
(SAIC 2004b). Beaver Creek has been designated as a Class C stream by NCDENR (NCAC
213.0300, - NCDENR 2003). Class C streams are to be protected to support aquatic -life
propagation and survival, fishing, wildlife, secondary recreation, and agriculture. The surface
water results from Beaver Creek were compared to North Carolina standards for all freshwater
classifications (Class C) dated April 1, 2001. In the absence of a North Carolina standard for all
freshwater classification values, the constituent's MDC was compared to the more stringent
North Carolina WS classes for surface water. North Carolina has five classifications for WS
surface waters (WS-1 through WS-V). In the absence of either a North Carolina Class C or WS
value, the surface water MDC was compared to a federal 304a standard (EPA 1998). For both
Beaver Creek and the Holbrook tributary, constituents with MDCs that were above any of the
surface water screening values were retained as surface water HHCOPCs.
Table 3-11 presents the recommended RGOs and final COCs identified in surface water.
1,1,2,2-Tetracholoroethane was .identified as a COC in surface water because the MDC was
above the recommended RGO (i.e., the North Carolina surface water standard). 1,1,2,2-
Tetra6holoroethane in surface water will require corrective action.
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SECTION 4
JUSTIFICATION AND PURPOSE OF CORRECTIVE ACTION
4.1 PURPOSE
EPA has established that corrective action.reflect the major technical components that should
be included in a selected remedy. The corrective_ action shall: (1) protect human health and the
environment; .(2) attain media cleanup standards set by the implementing agency (i.e.,
NCDENR); (3) control the source of the releases so as to reduce or eliminate, to the extent
practicable, further releases that might pose a threat to human health and the environment; (4)
comply with any applicable standards for management of wastes; and (5) other factors.
4.2 REMEDIAL RESPONSE OBJECTIVES
Contaminants have been detected in groundwater and surface water at concentrations
exceeding North Carolina groundwater and surface water standards, respectively, at SWMU 103
indicating there is a potential risk to human health and the environment. Therefore, corrective
action is warranted at SWMU 103.
The remedial action objectives for SWMU 103 are based on the protection of human health
and the environment. North Carolina has established groundwater and surface water criteria for
the protection of human health and the environment (North Carolina 2L and IMAC standards and
North Carolina surface water standards; respectively). The RROs for SWMU 103 are presented
below:
• Prevent use of groundwater.
• Reduce COCs in groundwater to North Carolina 2L standards.
• Reduce potential contact and ingestion of surface water.
• Prevent surface water from exceeding North Carolina surface water standards due to
discharge of groundwater contaminants into surface water.
The selected corrective actions would provide the technology(ies) necessary to 'minimize
exposure to contaminants in groundwater and surface water, reduce contaminant concentrations
in groundwater and surface water to levels that are protective of human health and the
environment, and achieve the best overall results with respect to such factors as effectiveness,
implementability, and cost.
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4.3 IDENTIFICATION OF REMEDIAL LEVELS
The development of potential remedial goals was presented in Section 3.13. Five VOCs
(1,1,2,2-tetrachloroethane; chloroform; chloromethane; tetrachloroethene; and TCE) are
considered HHCOCs in groundwater. The North Carolina 2L and IMAC groundwater standards
are proposed as the remedial levels for HHCOCs in groundwater. One VOC, 1,1,2,2-
tetrachloroethane is considered an HHCOC in surface water. The North Carolina surface water
standard (4 µg/L) was recommended as the proposed remedial level for surface water. Table 4-1
presents the HHCOCs and recommended remedial levels for groundwater and surface water at
SWMU 103.
In addition to the five VOCs that currently exceed remedial goals, other VOCs are
degradation daughter products of these contaminants (Figure 3-2). Although daughter products
do not currently exceed North Carolina 2L standards, they may be produced in the future under
natural conditions or certain remedial action technologies such as enhanced bioremediation. The
overall monitoring program needs to include daughter products and consider their North Carolina
2L standard (if any). Relevant daughter products are 1,1,2-trichloroethane, 1,2-dichloroethane,
chloroethane, cis 1,2-dichloroethene, trans 152-dichloroethene, 1,1-dichloroethene, and vinyl
chloride.
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SECTION 5
SCREENING OF CORRECTIVE ACTIONS
This chapter identifies . corrective action process options/technologies applicable to
groundwater and surface water at SWMU 103 and screens the process options/technologies with
respect to effectiveness, implementability, and cost. The process options/technologies that are
retained following the screening process are combined into site -wide corrective action
alternatives that address various levels of protectiveness of human health and environment. The
corrective action alternatives are then described and evaluated in more detail with respect to
RCRA standards in accordance with EPA guidance (EPA 1994) consisting of protecting human
health and the environment, attaining media cleanup standards, controlling the source of release,
compliance with applicable standards, and other factors (long-term reliability and effectiveness,
reduction in toxicity, mobility, or volume of wastes, implementability, and cost). Based on this
evaluation, a site -wide alternative is selected for detailed conceptual design and evaluation.
5.1 SCREENING CRITERIA
The first step in the development of corrective action alternatives involves the identification
and screening of suitable remedial process options/technologies for meeting the stated RROs
(Section 4.2). The process options/technologies were focused to chlorinated solvent
contamination (i.e., VOCs) in groundwater and surface water. The technologies presented are
evaluated for their general ability to protect and reduce the risk to human health for contaminants
in groundwater and surface water.
The technologies are discussed sufficiently to allow them to be compared using three general
criteria: effectiveness, implementability, and cost. An explanation of each criterion is provided
below.
5.1.1 Effectiveness
This criterion evaluates the extent to which a corrective action process option/technology
reduces overall risk to human health and the environment. It also considers the degree to which
the remedial process option/technology provides sufficient long-term control and reliability to
prevent exposures that exceed levels protective of human and environmental receptors. In
addition; short-term effectiveness is: included, which is particularly important for the SWW 103
site considering the close proximity to Holbrook. Elementary School and residential housing.
Short-term effectiveness evaluates the potential short-term impacts to human health and
environment from the implementation of the process option/technology. Other factors considered
include performance characteristics and expected durability.
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5.1.2 Implementability
This criterion evaluates the technical and administrative factors affecting implementation of a
corrective action and considers the availability of services and materials required during
implementation. Technical factors assessed include ease and reliability of initiating construction
and operations, prospects for implementing any additional future actions, and adequacy of
monitoring systems to detect failures. The impact of a remedial alternative to post operations was
considered, with the proximity of SWMU 103 to Holbrook Elementary School and residential
housing and utilities as significant factors for evaluating the potential implementation of the
process option/technology. Technical feasibility considers the performance history of the
technologies in direct applications or the expected performance for similar applications.
Uncertainties associated with construction, operation, and performance monitoring are also
considered. Service and material considerations, include equipment and operator availability and
applicability or development requirements for prospective technologies. The availability of
services and materials is addressed by considering the material components of the proposed
technologies and the locations and quantities of those materials. Administrative factors include
ease of obtaining permits, enforcing restrictions, and maintaining long-term controlof the site.
5.1.3 Cost
Relative screening level costs are included for each corrective action process
option/technology. The cost estimates are generic and intended solely to facilitate evaluation and
comparison among technologies.
5.2 EVALUATION OF CORRECTIVE ACTION TECHNOLOGIES FOR
GROUNDWATER
A no -action alternative and five categories of corrective action process options/technologies
were identified as applicable for chlorinated solvent contamination in groundwater at SWMU
103: (1) institutional controls: land- and groundwater -use restrictions and physical barriers, (2)
monitored natural attenuation (MNA), (3) ex -situ treatment technologies (i.e., pump and treat),
(4) in -situ technologies (e.g., chemical oxidation, bioremediation, phytoremediation, etc.), and
(5) monitoring (e.g., groundwater, surface water, soil gas, etc.). These corrective action
technologies are described in Table 5-1. The technologies were evaluated using the screening
criteria of effectiveness, implementability, and cost. Results of the screening are also shown in
Table 5-1.
5.2.1 No Action
The no -action option provides a baseline against which other process options/technologies can
be compared. Under this option, no further action would be taken to mitigate risks posed by
groundwater or surface water at SWMU 103. Risks to human health and the environment would
remain the same. Groundwater at SWMU 103 is presently not used and no restrictions or
controls would be placed on the use of groundwater. Future use of the groundwater is unlikely
given the poor production characteristics in the surficial groundwater; however, this could not be
ensured. Contaminants in groundwater would continue to migrate to surface water in Beaver
Creek and Holbrook tributary where there is the potential for risk to human health and
environment. Under no action, no groundwater monitoring would be performed to assess the
future levels of contamination or potential migration. Groundwater and surface water
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contamination would continue to be present at unknown levels. No cost would be associated with
the selection of this alternative. The acceptability of the no -action option is judged in relation to
the assessment of known site risks and by comparison with other corrective action technologies.
No action is not considered a viable option because it provides no reliable or effective method
for protecting human health or the environment. Therefore, the no -action option has been
eliminated from further evaluation.
5.2.2 Institutional Controls
Institutional controls are actions taken to restrict access to contaminated areas or media
through the establishment of land- or groundwater -use restrictions or by construction of physical
barriers. Land- and groundwater -use restrictions include those implemented through the BMP.
Groundwater -use restrictions would be implemented preventing its use for drinking water or
irrigation. Land- and groundwater -use restrictions would be documented and implemented at
Fort Bragg through the BMP. Currently; SWMU 103 is part of a federal installation and is
expected to be retained by the federal government for the indefinite future. As such, land- and
groundwater -use restrictions would be implemented as specified in the facility BMP. Existing
fencing could be repaired/upgraded and new fencing could be installed to prevent contact with
surface water. In addition, signs could be placed along Beaver Creek and the Holbrook tributary
to inform persons of the potential contamination in surface water. Land -use restrictions and/or
warning signs would provide an effective, readily implementable, and cost-effective method for
reducing human exposure to surface water at the site. Groundwater -use restrictions would be
effective at preventing exposure to the groundwater. Institutional controls will not be considered
as a stand-alone technology but will be combined with other more active process
j ? options/technologies to ensure their protectiveness during the corrective action period. The
institutional controls alternative has been retained for further consideration.
5.2.3 Monitored Natural Attenuation
Natural attenuation or intrinsic remediation is the reduction in the concentration and mass of a
substance in groundwater due to naturally occurring physical, chemical, and biological processes
without human intervention. These processes include, but are not limited to, dispersion,
diffusion, sorption and retardation, and biodegradation. Many organic compounds are degraded
in the subsurface environment by both biological and abiotic mechanisms. However, biological
mechanisms tend to dominate in most groundwater systems and, -therefore, are the primary
destructive attenuation mechanism.
The primary process for natural biodegradation of the more highly chlorinated species is
hydrogenolysis or reductive dechlorination. This involves the microbial transformations of
chlorinated solvents under anaerobic conditions (without oxygen) using reductive reactions that
involve either hydrogenolysis or dihaloelimination. Hydrogenolysis occurs when a chlorine atom
is replaced by a hydrogen atom. Dihaloelimination involves removal of two adjacent chlorine
atoms and formation of a carbon -to -carbon double bond. High DO concentrations and positive
Redox readings were measured during groundwater sampling, indicating a highly aerobic and
oxidizing (i.e., non -reducing) subsurface environment at SWMU 103. Aerobic conditions are
conducive to the biological degradation of petroleum contaminants. These conditions are not
conducive to anaerobic reductive dechlorination. Other biological natural attenuation processes
for chlorinated compounds or solvents include cometabolic mechanisms in which the chlorinated
solvent is biodegraded via co -metabolism; the degradation is catalyzed by an enzyme or cofactor
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that is produced by the microorganism for other purposes, typically the degradation of another
chemical in the groundwater. Cometabolic mechanisms are aerobic, meaning they occur in the
presence of oxygen.
Modeling (Section 3.11.2) performed using the most current 1,1,2,2-tetrachloroethane
concentrations and lowest (most conservative) literature -based biological degradation rate for
chlorinated solvents in groundwater at SWMU 103 estimated that 60 years from CY 2005 would
be required to'achieve the North Carolina 2L standards. 1,1,2;2-Tetrachloroethane was selected
for modeling because it is the primary contaminant in groundwater and, therefore, is the limiting
factor for the natural attenuation period. The other chlorinated solvents in groundwater. would be
expected to achieve their respective remedial levels sooner than 1,1,2,2-tetrachloroethane. Some
uncertainty is associated with any modeling, especially in predicting the .time required to achieve
concentrations below analytical detection levels. The North Carolina 2L standard for 1,1,2,2-
tetrachloroethane is 0.17 µg/L, which is below the analytical reporting level of 1 µg/L for
1,1,2,2-tetrachloroethane. Modeling estimated that the concentration of 1,1,2,2-tetrachloroethane
would be below the reporting limit in 44 years from CY ' 2005. MNA of groundwater would
require the monitoring of contaminant levels to ensure that the mass of contamination in the
groundwater is being reduced with time. Institutional controls (Section 5.2.2) and groundwater
monitoring would be used in conjunction with MNA to ensure the protection of human health
and the, environment over the typically longer implementation times required to meet remedial
levels. In addition, MNA could be combined with more active technologies to meet the RROs for
the site in a more reasonable timeframe. MNA is retained for further consideration.
5.2.4 Phytoremediation
Phytoremediation is an emerging technology that uses plants and their associated rhizospheric
microorganisms to remove, degrade, or contain chemical contaminants located in soil and
groundwater. Phytoremediation is limited to the depths that the plants roots (plant dependent)
will reach, which is approximately 20 to 25 feet bgs, though the technology is more successful
with very shallow water tables (2 to 5 feet bgs). Phytoremediation could not be used for total
treatment of the groundwater plume at SWMU 103 because of the depth of the groundwater
contamination and land use at SWMU 103. Phytoremediation was considered for use in
conjunction with other remedial technologies (e.g., NINA, etc.) as a barrier/polishing step to
prevent contaminated groundwater from intercepting surface water at Beaver Creek and the
Holbrook tributary. The groundwater along Beaver Creek and the Holbrook tributary is
encountered at approximately 5 to 8 feet bgs and extends to approximately 25 feet bgs (clay -
confining layer). For SWMU 103, phytoremediation would focus on 1,1,2,2-tetrachloroethene in
groundwater. Literature indicates that hybrid poplars or willows would be suited to the
geographic location of SWMU 103. Phytoremediation using phreatophyte trees such as hybrid)
poplars and willows has been proven effective for treating low concentrations of CVOCs. High
hydraulic uptake rates from the hybrid poplars and willows would only begin after
approximately 4 years of growth; however, very little hydraulic uptake would occur during the
winter months when the plants were dormant.
A typical phytoremediation system for CVOCs would consist of offset rows of hybrid poplar
or willow trees placed approximately 10 feet apart. However, portions of SWMU 103 are already
heavily wooded; the existing hardwood trees transpire water at approximately half the rate of
hybrid poplar or willow trees. Fort Bragg DPW has indicated that willow trees are unacceptable
for planting at Fort Bragg. That leaves only the use of poplar trees to supplement the
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evapotranspiration of the existing hardwoods as the only potential implementable
phyotoremediation option. Limitations of implementability and effectiveness .resulted in the
elimination of phytoremediation from further analysis.
5.2.5 Permeable Reactive Barrier
PRBs using reactive media such as zero-valent iron are a passive in -situ treatment technology
that has been successful in treating chlorinated solvents contamination in groundwater.
Permeable reactive walls are trenches excavated perpendicular to the groundwater flow. path that
are backfilled with a reactive medium. The reactive wall can be designed and constructed to be
permanently left in -place or can consist of cassettes of treatment medium that could be
periodically replaced. As the contaminated groundwater flows through the wall, the
contaminants are removed by physical and chemical processes including precipitation, sorption,
oxidation/reduction, fixation, and/or degradation.
Several methods have been developed for construction of permeable reactive walls to as deep
as 100 feet bgs; however, typical construction techniques are applicable to shallow
emplacements less than 45 feet in- depth. In the simplest case, a trench of the appropriate width
can be excavated by a backhoe, tracked excavator, trencher, or similar equipment to intercept the
flow of the contaminated groundwater. As discussed under,the SCM, the contaminant plume at
SWMU 103 is large (approximately 90+ acres) and intercepts surface water at Beaver Creek and
the Holbrook tributary. Contaminated groundwater at SWMU 103 also has migrated under
Holbrook Elementary School. The PRB would be tied into the clay=confining layer located
beneath the groundwater plume. The depths to the clay -confining layer are amenable
(approximately 30. feet bgs) to a PRB along the perimeter of the plume, as well as upgradient of
Holbrook Elementary School. A number of installation methods would be applicable for SWMU
103 including: sheet piling, biopolymer trench, continuous -pass trench, and uniform auger holes.
The continuous -pass trench was selected as the representative process option for the installation
method because of its low cost. The continuous -pass trencher can trench to depths of 25 to 30
feet bgs; the reactive material is placed in the trench and subsequently covered as the trencher
advances forward. Potential issues regarding the effectiveness of reactive walls include the
potential for biological growth and precipitation of metals that could compromise long-term
performance. If reductive dehalogenation is incomplete, degradation products such as vinyl
chloride might be produced.
Two installations of a PRB were considered for SWMU 103. One design would confine the
entire downgradient portion of the plume prior to the groundwater intercepting Beaver Creek and
the Holbrook tributary, and the second limited design would be to install a PRB just upgradient .
of Holbrook Elementary School to prevent groundwater from migrating beneath the school. The
complete PRB would be installed along the perimeter of the plume upgradient (east) of Beaver
Creek and upgradient (north and west) of the Holbrook tributary. Under this design, as 'the PRB
nears Holbrook Elementary School; 'it would trend along the west and north sides of the school to
remove contaminants in groundwater on the upgradient side. The total length would be
approximately 3,875 feet. The depth to the clay -confining layer at this point would .be at the
present limits of installation capabilities using standard excavation technologies. The second
limited design would be to only install a PRB upgradient of Holbrook Elementary School to
prevent contaminated water from migrating beneath the school. The PRB would encircle
Holbrook Elementary School on the west, north, and northeast sides and be approximately 1,075
feet in length. Again, the depth of clay would have to be confirmed along the path of the PRB
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because present data indicate that the clay in some portions of this area may be at, or greater
than, the maximum feasible depth for the installation of the PRB using typical construction
techniques.
High DO concentrations and positive ORP readings were measured during groundwater
sampling at SWMU 103, thus indicating a highly aerobic and non -reducing subsurface
environment. In addition, the nitrate and sulfate concentrations in groundwater ranged from 0.6
to 3.2 mg/L and 1.6 to 39.8 mg/L, respectively (SAIC 2004a). Under highly oxygenated
conditions, dissolved iron may precipitate as ferric oxyhydroxide or ferric hydroxide, reducing
the permeability of the PRB. The highly aerobic conditions and moderate nitrate and sulfate
concentrations will necessitate use of a relatively large quantity of zero-valent iron to treat the
relatively low concentrations of chlorinated solvents, and may result in premature failure and the
need for replacement/rejuvenation of the'PRB.
PRB designs only reduce or eliminate the migration of the contaminants in groundwater at
SWMU 103. The PRBs would treat the groundwater at SWMU 103 prior to migration to a
potential exposure point/receptor (surface water and/or Holbrook Elementary School). Unless
coupled with an additional treatment alternative, the groundwater upgradient of the PRB would
remain contaminated at SWMU 103. Both potential designs for a PRB were eliminated from
further analysis because of implementation concerns and high costs. Implementation of a PRB at
SWMU 103 would encounter difficulty due to underground utilities (e.g., fiberoptics to Sprint
building, sewer, water, etc.) and interruption of the school. In addition, construction of a long
PRB would be extremely "expensive. Installation of a continuous PRB only upgradient of
Holbrook Elementary School would also have the same implementability concerns. The
groundwater in the remaining areas of the plume would still be contaminated, thus requiring
additional corrective action. In addition, implementation of either PRB design near Holbrook
Elementary School would result in interruption of the school's operations.
5.2.6 Groundwater Pumping and Ex -situ Treatment of Groundwater
Pump -and -treat technologies consist of the installation of a series of extraction wells or
subsurface drains in the area of the plume that are manifolded together and connected to a pump.
Groundwater is pumped/extracted from the aquifer to a treatment system. The treatment
processes are specific to the contaminants in the groundwater. For the COCs at SWMU 103,
various treatment systems ranging from ex -situ air stripping to activated carbon are applicable.
Discharge of any treated groundwater from the treatment system would require a National
Pollutant Discharge Elimination System permit. A site -wide pump -and -treat approach was
eliminated because the large size of the contaminated groundwater plume (more than 92 acres)
would require an extensive number of extraction wells manifolded together and would generate
large quantities of water requiring treatment. Site -wide implementability of an extensive network
of manifolded extraction wells would be difficult given the locations of utilities and the
proximity to residential areas. Pump -and -treat technology is more likely to be effective and
implementable at SWMU 103 if goals are limited to intercepting, removing, and treating
contaminated groundwater prior to its discharge to surface water. This objective could be
implemented through a series of subsurface drains along Holbrook tributary and/or Beaver
Creek. The drains can be located such that they will avoid major utilities as well as impact to
the base mission and residents. Pumping rates can be adjusted to minimize discharge of
contaminated groundwater to the surface water as well as minimize impact to the creek and
tributary (i.e., not pump existing surface water from the creek bed). Contaminant concentrations
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are sufficiently low in the target areas so the carbon adsorption is a cost competitive treatment
technology. This treatment technology also has advantages in that it is clean (no air emissions),
quiet, and low impact. The expected total pumping rate is 10 to 20 gpm. Costs of pump -and -
treat approaches are generally high primarily due to the long period of time that the system
would have to be operational. However, if pump -and -treat is implemented in conjunction with
an approach to reduce the mass flux of the contaminant source, the operational life of the system
could be limited. Once groundwater concentrations are reduced sufficiently that surface water is
no longer threatened, pumping would be eliminated. Therefore pump -and -treat is retained for
further analysis.
5.2.7' Air Sparging
In -situ air sparging involves .the installation of injection wells or a trench into the saturated
zone. Air is then injected, and the VOCs dissolved in the groundwater are volatilized/stripped
from it into the overlying vadose zone where they eventually migrate out into the atmosphere or
are captured via soil vapor extraction; hence, air sparging is typically used in conjunction with
vacuum extraction systems. Depending on the contaminant concentration in the vapor stream, the
extracted vapor can be released to the atmosphere or piped to a treatment system where the
volatile contaminants are treated prior to being released to the atmosphere. The injected air
travels through the saturated zone in 'the form of continuous air channels that are influenced by
the pressure and flow rate of the injected air and the depth of injection; however, the structure
and stratification of the saturated zone soil have the most predominant influence on the
effectiveness of an air sparging system. Significant preferential channeling can be caused by
relatively subtle permeability changes, reducing the effectiveness of the air sparging system.
The subsurface geology (Section 2.3) at SWMU 103 is amenable to vapor extraction. The
average hydraulic conductivity of the saturated zone based on slug testing at SWMU 103 is 4.8
feet/day, which is sufficiently high hydraulic conductivity for air sparging. However, air
sparging could result in uncontrolled migration of vapors.
Air sparging was eliminated from further consideration at SWMU 103 because of the
uncertainty associated with the mobilization of vapors. Vapor intrusion has been a concern at
Holbrook Elementary School and the adjacent residential housing. Air sparging would mobilize
VOCs in groundwater and concentrations could increase vapor migration to buildings. In
addition, the same implementability concerns associated with site -wide groundwater extraction
are applicable.to air sparging. This includes an extensive network of extraction wells and a large
manifold system.
5.2.8 In -Situ Chemical Oxidation
In -situ chemical oxidation (ISCO) involves the injection of an oxidizing agent, and potentially
a catalyst, to oxidize (degrade) the chlorinated solvents in groundwater. The primary chemical
oxidation chemicals 'are hydrogen peroxide, permanganate, ozone, and Fenton's reagent
(hydrogen peroxide and iron). The oxidant chemicals react with the contaminant producing
innocuous substances such as carbon dioxide, water, and inorganic chloride. Classes of
chemicals that, are amenable to treatment by ISCO include BTEX, chlorinated alkenes, PAHs,
and many other organic compounds. Literature indicates that chemical oxidants are not effective
against chlorinated alkanes such as TCA (Yin 1999). However, more recent investigations have
indicated that chlorinated alkanes can be reduced using Fenton's reagent (Smith et al. 2004). The
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observed process is not an oxidative process, but is believed to use a co-reductant mechanism;
therefore, the mechanism has lower removal efficiencies and requires larger quantities of
oxidants to achieve the reductive conditions.
The chemical oxidant is typically injected through a series of injection wells or temporary
points. Chemical oxidation typically is more appropriate for contaminant plumes with higher
contaminant concentrations and not the relatively large (more than 92 acres) and diffuse (i.e.,
low -concentration) contaminant plume at SWMU 103. Multiple injections would be required.
The predominant contaminant in groundwater at SWMU 103 is 1,1,2,2-tetrachloroethane, a
chlorinated alkane. ISCO was eliminated from further consideration for the following reasons:
(1) the uncertainty associated with its performance on the primary COC (1,1,2,2-
tetrachloroethane, a chlorinated alkane), (2) a highly -concentrated source area has not been
identified at SWMU 103, and (3) the large dosage and longer reactive, time that would potentially
be required to treat the primary COC.
5.2.9 Enhanced Bioremediation Using Anaerobic Reductive Dechlorination
Reductive dechlorination is the most prominent mechanism by which CVOCs are biologically
degraded and takes place under anaerobic (no oxygen) conditions. The degradation pathway for
1,1,2,2-tetrachloroethane; tetrachloroethene; and TCE is presented in Figure 3-2. Reductive
dechlorination is a process in which anaerobic microorganisms substitute hydrogen for chlorine
on the chlorinated solvent. There are a number of electron donors that have been injected into the
subsurface at chlorinated solvent sites to facilitate reductive dechlorination biodegradation and
their selection is based on site -specific conditions. These include both liquids (sodium lactate,
molasses, and vegetable oil) and solids (hydrogen -releasing compound and chitin). Site -specific
geochemistry conditions determine whether anaerobic reductive dechlorination. can be
effectively initiated and maintained in the subsurface.
High DO concentrations and positive ORPs were measured during groundwater sampling at
SWMU 103, indicating a highly aerobic and oxidizing subsurface environment. These conditions
are not conducive to promoting anaerobic reductive dechlorination; however, they can be
overcome by adding sufficient organic substrate. The nitrate and sulfate concentrations in
groundwater ranged from 0.6 to 3.2 mg/L and 1.6 to 39.8 mg/L, respectively (SAIC 2004a).
Nitrate and sulfate concentrations less than 1 and 20 mg/L, respectively, are conducive for
reductive dechlorination (AFCEE 2004). Although the upper range of nitrate and sulfate
concentrations in SWMU 103 groundwater are above these thresholds, they do not preclude
successful implementation of enhanced bioremediation. In addition, the total iron concentration
in groundwater ranged from 0.09 to 5.9 mg/L. The 5.9 mg/L total iron concentration had a
corresponding 0.5 mg/L of ferrous iron, indicating that the iron was primarily in groundwater as
ferric iron. High levels of ferric iron inhibit microbial anaerobic dechlorination similar to other
competing electron acceptors (AFCEE 2004).
Elevated concentrations of competing electron acceptors do not preclude implementation of
enhanced anaerobic reductive dechlorination at SWMU 103; however, they will put an additional
demand on injected electron donors such that a higher quantity of electron donor would be
required to attain and maintain the proper environment for anaerobic reductive dechlorination to
be successful. Analysis of contaminant concentrations in the source area indicates that reductive
dechlorination has occurred on site in the past due to commingling of chlorinated solvent and
petroleum fuel contaminants (see Section 3.7.6). Chlorinated solvent concentrations are
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relatively low in shallow groundwater, where BTEX is present, but much higher in deeper
sections of the aquifer, where BTEX is absent. Daughter products of I,1,2,2-tetrachloroethane
and TCE are also present, though infrequently and at very low levels. This indicates that
potentially more toxic daughter products, such as vinyl chloride, are not expected to accumulate
but would biodegrade very quickly under ambient groundwater geochemistry. However,
generation of some vinyl chloride in the treatment zone is expected, and therefore this process is
not recommended in the immediate vicinity of inhabited buildings where vapor intrusion is a
concern.
Given the large plume size with relatively low concentrations of. chlorinated solvent
contaminants, the high concentration of some competing electron receptors including DO, and
lack of degradation products, SWMU 103 is not a good candidate.for application of anaerobic
reductive dechlorination for complete plume treatment. However, anaerobic reductive
dechlorination may be applicable for treatment of specific areas (e.g., source area) of the plume;
therefore, anaerobic reductive/dechlorination biodegradation was retained for further
consideration.
A combination of soluble (e.g., high fructose corn syrup) and slow release (e.g., vegetable oil)
carbon substrates is particularly well suited for the SWMU 103 source area. The soluble
substrate will begin to biodegrade immediately, creating anaerobic conditions. The slow release
substrate will help maintain these conditions over the longer term. It is particularly important to
treat chlorinated solvent contaminants that are diffusing out of the Cape Fear clays (i.e., the
probable source of continuing chlorinated solvent contamination). Organic substrate injected at
the top of the confining clay unit will absorb into the clay surface and enhance biological
.treatment for chlorinated solvent contaminant diffusing out of the clay. This treatment zone will
be particularly long-lasting since there is no advective groundwater flow in the clay and therefore
depleted electron acceptors will not be quickly replenished.
A pH amendment product such as sodium bicarbonate would also be added to maintain
neutral pH conditions that are optimal for chlorinated solvent biodegradation. Some of the
injection points can be completed as small diameter wells so that supplemental carbon substrate,
pH amendment, and if necessary, bioaugmentation culture can be, added in the future as
appropriate. Generally, microorganisms capable of reductive dechlorination are ubiquitous in
the environment, but may take time to generate a population sufficient to provide significant
biodegradation. If this process is slow in developing, bioaugmentation with a commercial
microbial culture can accelerate the process. Based on the above discussion, enhanced anaerobic
bioremediation is retained for further evaluation.
5.2.10 Enhanced Bioremediation Using Aerobic Cometabolic Mechanism
Chlorinated hydrocarbons have been observed to be oxidized cometabolically by microbes
under aerobic conditions. The cometabolic. process involves the microbial breakdown of the
chlorinated hydrocarbons where the chlorinated hydrocarbon is oxidized incidentally by an
enzyme or cofactor produced during microbial metabolism of another compound being used as
an electron donors. Electron donors that have been observed in aerobic oxidation include:
dextrose, methane, ethene, ethane, propane, butane, aromatic hydrocarbons (such as toluene and
phenol), and ammonia. Under aerobic conditions, a monoxygenase enzyme mediates the electron
donation reaction, converting the chlorinated hydrocarbon into unstable epoxides that rapidly
degrade in water to alcohols and fatty acids (EPA 2000).
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Because of the naturally occurring highly aerobic conditions observed in the groundwater at
SWMU 103, 'bench -scale (Section 2.8.5.1) and in -situ (Section 2.8.5.2) pilot studies were
performed to evaluate bioremediation using aerobic cometabolic mechanism. The results
indicated that the addition of an electron donor (represented by dextrose) and aerobic bacteria did
biodegrade 1,1,2,2-tetrachloroethane and possibly also TCE. However, contaminant
concentrations rapidly rebounded. Unfortunately, the carbon substrates for aerobic cometabolic
bioremediation are gases or are highly soluble. This means that carbon substrate, as well as
oxygen, would have to be injected continuously to support this biodegradation process, resulting
in more infrastructure needed on site as well as'higher costs. It will also not be possible maintain
enough carbon substrate and oxygen in the top layer of the Cape Fear clays to create a
biodegradation zone that would effectively stop the diffusive flux of chlorinated solvent
contamination into the aquifer. Therefore aerobic cometabolism can only be engineered to treat
chlorinated solvents once they are in the aquifer, and will not impact the flux of contaminants
from the lower confining clay. These factors combine to lower effectiveness and
implementability and increase costs such that bioremediation by aerobic cometabolism is
considerably less suited to SWMU 103 site conditions than is reductive dechlorination.
Enhanced bioremediation using aerobic cometabolic mechanism was not retained for further
consideration.
5.2.11 Monitoring
Monitoring of groundwater, surface water, and soil gas may be required to periodically assess
contaminant concentrations to ensure the protection of human health and the environment and to
evaluate the performance of an implemented corrective action. The monitoring requirements
(sample schedule, number of samples, locations, etc.) would be specific for the selected
corrective action alternative, and optimized over time as trends become apparent and
contaminant levels change in response to the corrective action. The description and purpose of
the monitoring of each medium are discussed in the following sections.
Groundwater monitoring would be performed in selected monitoring wells at SWMU 103 to
evaluate the performance of an implemented corrective action. The groundwater would be
sampled using low -flow or possibly passive sampling techniques to reduce the impact of
turbidity on the groundwater samples. At a minimum, the groundwater samples would be
analyzed for VOCs to evaluate the concentrations of presently identified contaminants and
potential degradation products in groundwater. VOC analysis includes all those chlorinated
solvents that currently exceed clean-up standards, as well as other chlorinated compounds that
could be formed as products of biodegradation processes. In addition, field parameters such as
turbidity, DO, temperature, ORP, and pH would be measured at each well where groundwater
samples were collected. Water levels would be collected at the monitoring wells to develop
groundwater potentiometric maps. Additional analysis may be performed on groundwater for the
implementation of specific alternatives. For example, natural attenuation parameters would be
collected for alternatives in which MNA was part of the alternative, or nutrients (nitrogen,
phosphate, etc.) and bacteria plate count samples may be collected for in -situ bioaugmentation
alternatives. Specific sample requirements for groundwater will be discussed as part of each site -
wide alternative.
Soil gas samples would be collected around Holbrook Elementary School to ensure that
VOCs in groundwater have not migrated (i.e., vapor intrusion) into the soil under Holbrook
Elementary School at levels that present a risk to human health in the school. Soil gas samples
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would be collected from permanent soil gas probes installed around the school and analyzed for
VOCs. It is anticipated that annual soil gas samples would be performed prior to the start of the
school year. However, the soil gas sampling scope may be adjusted based on the, corrective
action that has been implemented. Specific sample requirements for soil gas are discussed as part
of each site -wide alternative.
_ Surface water samples may be collected to evaluate .potential .contaminant migration from
groundwater to this medium in Beaver Creek and the Holbrook tributary. At a minimum, the
surface water samples would be analyzed for VOCs in groundwater migrating from SWMU 103.
In addition, field parameter measurements similar to those collected for groundwater would be
performed. Specific sample requirements for surface water are discussed as part of each site -
wide alternative.
5.3 EVALUATION OF CORRECTIVE. ACTION TECHNOLOGIES FOR SURFACE.
WATER
A no -action alternative and five, categories of corrective action process options/technologies
were identified as applicable for chlorinated solvent contamination in surface water at SWMU
103: (1) institutional controls (i.e., use restrictions and physical barriers), (2) ex -situ treatment
technologies (i.e., air stripping, activated carbon, etc.); (3) in -stream. technologies (i.e.,
aeration/volatilization, constructed wetlands, etc.), (4) stream restoration/segregation, and (5)
monitoring. These corrective action technologies are described in Table 5-2. The technologies
were evaluated using the screening criteria of effectiveness, implementability, and cost. Results
of the screening are also summarized in Table 5-2.
5.3.1 No Action
The no -action option provides a baseline against which other process options/technologies can
be compared. Under this option, no further action would be taken to mitigate risks posed by
surface water at SWMU 103. Risks to human health and. the, environment would remain the
same. Contaminants in groundwater would continue to migrate to surfacewater in Beaver Creek
and the Holbrook tributary where there is the potential for risk to human health and the
environment. Under no action, no surface water monitoring would be performed to assess the
future levels of contamination or potential migration. Migration of contaminated surface water in
Beaver Creek and the Holbrook tributary would continue at unknown levels. No cost would be
associated with the selection of this alternative. The acceptability of the no -action option is
judged in relation to the assessment of known site risks and by comparison with other corrective
action 'technologies. No action- for surface water is not considered a viable option because it
provides no reliable or effective method for, protecting human health or the environment.
Therefore, the no -action option has been eliminated from further evaluation.
5.3.2 Institutional Controls
Institutional controls are actions taken to restrict access to contaminated areas or media
through the establishment of land-, or surface water -use restrictions or by construction of physical
barriers. Surface water -use restrictions include those implemented through.the BMP. The surface
water in Beaver Creek and the Holbrook tributary is not used as a source of potable water,
irrigation, and/or recreation primarily because the flows are too low. The streams are primarily
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used as a stormwater drainage conveyance for Fort Bragg. The ecological habitat was described
in Section 2.7.
Surface water -use restrictions would be. implemented, thus preventing its use, for drinking
water, irrigation, or recreation. The surface water -use restrictions would be documented and
implemented at Fort Bragg through the BMP. Currently,- SWMU 103 is part of a federal
installation and is expected to be retained by the federal government for the indefinite future. As
such, land- and groundwater -use restrictions would be implemented as specified in the facility
BMP. Existing fencing could be repaired/upgraded and new fencing could be installed along
Beaver Creek and the Holbrook tributary to restrict contact with the surface water. Warning
signs would also be placed along Beaver Creek and the Holbrook tributary to inform persons of
the potential contamination in the surface water. Surface water -use restrictions and/or warning
signs would provide an effective, readily implementable, and cost-effective method for reducing
human exposure to surface water at the site. Institutional controls for surface water will not be
considered as a stand-alone technology, but will be combined with other more active process
options/technologies to ensure their protectiveness during the corrective action period. The
institutional controls alternative has been retained for further consideration.
5.3.3 Ex -situ Treatment Technologies and Process Options
A variety of treatment technologies are available for treating VOCs in water and would be
applicable to treating the surface water. The most common treatment technologies for VOCs are
air stripping and activated carbon. Using ex -situ treatment, the surface water would be diverted
and pumped to a low -profile air stripper or activated carbon system where it would be treated
and then discharged back into the stream. The ex -situ system would have to be designed to
accommodate or bypass stormwater flows in the Holbrook tributary. The facility would be
located near where the Holbrook tributary discharges into Beaver Creek to ensure that all
contamination migrating to the Holbrook tributary is treated prior to entering Beaver Creek. At
present, the Holbrook tributary is the only contributor to the exceedances of VOCs in Beaver
Creek because all of the concentrations above the North Carolina surface water standards have
been downstream of where . the Holbrook tributary enters Beaver Creek. Electrical and
communication (for remote operation) utilities would have to be run to the system. The unit
would have to be fenced to prevent unauthorized access and trespassing. There would be O&M
associated with the ex -situ systems.
Ex -situ treatment was eliminated from further. consideration. Activated carbon treatment was
eliminated as a process option for surface water because of the higher level of pretreatment that
would be required for the surface water and the solid waste that would be created by the waste
carbon. The activated carbon could easily clog from particulates in the surface water, especially
during rainfall events. Therefore, pretreatment such as sedimentation and potential filtration
would be required to pretreat the surface water. Further, total organic carbon concentrations in
surface water were measured at 3.2 mg/L, which will consume activated carbon capacity and
raise treatment costs. The activated carbon system would create solid waste from the spent
carbon and sludge generated from the pretreatment sedimentation.
Ex -situ air stripping was also eliminated from further consideration because of
implementability requirements, O&M requirements, the uncertainty associated with the design
(e.g., stormwater flows, pretreatment requirements, etc.), and relatively high cost..
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�ll
-- 5.3.4 In -situ Treatment Technologies and Process Options
In -situ treatment technologies for surface water include both physical systems to increase
aeration/volatilization of VOCs in the surface water such as riprap or engineered cascades and
biological systems such as constructed wetlands, which use a combination of abiotic and biotic
processes to treat the VOCs in surface water.
5.3.4.1 Aeration/Volatilization
In -stream aeration/volatilization technologies for removing VOCs in surface water are low -
technology systems that facilitate gas transfer. Volatilization of VOCs occurs in the streams
under ambient conditions. Monitoring in. April 2007 shows that 1,1,2,2-tetrachloroethane
concentrations in Beaver Creek decrease (presumably through volatilization) to meet. North
Carolina surface water standards somewhere between Knox Street and Gruber Road. If
compliance with surface water RGOs were attained through natural volatilization sufficiently
near the confluence of Holbrook tributary and Beaver Creek, natural volatilization combined
with institutional controls and monitoring may be an acceptable solution. However, since
1,1,2,2-tetrachloroethane migrates beyond theknown footprint of the groundwater plume
(currently understood to extend to Knox Street) at concentrations greater than the North Carolina
surface water standard, aeration/volatilization would have to be enhanced through engineered
technologies.
. The conceptual, model for the hydrology and contaminant transport of 1,1,2,2-
tetrachloroethane in the Holbrook tributary and Beaver Creek is that the majority of water flow
appears to be in the Holbrook tributary. The combined base flow is relatively low, estimated to
be approximately 180 gpm. The concentration of 1,1,2,2-tetrachloroethane in surface water
where Beaver Creek flows under Knox Street is < 8.6 µg/L (relative to the surface water standard
of 4 µg/L). Enhancing in -stream aeration/volatilization appears to be a feasible approach to meet
the surface water standard at this location.
Engineered aeration systems may be passive systems such as "roughening" the stream bed
with boulders or installing weirs / drop structures to increase agitation and surface area to
facilitate volatilization. More complicated active approaches include mechanical surface mixers,
fountains, or air sparging systems, which are effectively low technology versions of air stripping
(Section 5.3.3). Active approaches require mechanical pumping of either surface water or air and
probably the formation of an in -stream collection pool to accumulate sufficient surface water to
allow volatilization.
Engineered aeration systems involve a number of technical, regulatory and safety constraints.
These include:
• Limited vertical relief. The change in elevation in the Holbrook tributary in the vicinity of'
the contaminant plume is 25 feet (Honeycutt Road to Beaver Creek). A majority of the
elevation change occurs before San Lucas Drive. The limited amount of vertical relief
will limit the number of possible drop structures or weirs, as well as the effectiveness of
passive aeration systems in general.
• Erosion concerns: Active aeration systems create erosion concerns. Surface mixers
generate strong currents that would require a construction of a large concrete basin,
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requiring substantial changes to the streambed and potential difficulties obtaining the
necessary permits. Other active systems (sprayers/fountains or air sparging) must be also
configured to prevent erosion, but solutions should be less costly.
• USACE permitting: Preliminary discussions with the USACE Wilmington District
revealed that a nationwide permit #38 will be required for minimal remediation in the
streambed. If construction is extensive a more time consuming permit may be required.
The goal of the USACE is for "minimal damage" to the surface water environment.
Fish and wildlife concerns: Certain aeration systems could pose a barrier to fish
migration. Both the Holbrook tributary and Beaver Creek are too shallow for most of
their reach to support . fish larger than small minnows. The impact of
aeration/volatilization approaches on fish migration will need to be discussed with the
Fish and Wildlife Service.
• Safety, particularly for children: Some aeration/volatilization devices will attract the
attention of children from the school and surrounding residential areas. Some of the
technologies will increase the depth of the water in certain areas, creating a safety hazard.
Any aeration/volatilization approach other than installing boulders will likely require
limiting access with fencing.
An additional complicating factor is that most of the aeration/Volatilization technologies will
have to be pilot tested to ascertain their effectiveness.
Both passive and active engineered aeration/volatilization approaches are retained for further
evaluation. However, given the constraints and concerns listed above, a step -wise approach is
the most prudent course with each step being more difficult, potentially causing more regulatory
problems from a Fish and Wildlife perspective relative to hypothetical fish migration; a USACE
perspective of "minimal- damage"; and each causing more potential safety hazards for small
children.
Step 1: Enhance the natural volatilization by roughening the stream bed. This would be
accomplished by focusing on those portions of the stream that are ,flowing at the highest
velocities. Boulders, and paving blocks (in Holbrook Culvert) would be strategically placed in
the highest velocity areas in an attempt to agitate the water surface by developing eddies and
small hydraulic. jumps that would increase volatilization over that currently occurring.
Monitoring near Knox Street over a period of time will determine if Step 1 is adequate or if Step
2 is indicated. Issues with this approach are as follows:
• COE Permit. Adding boulders (6-12 inches) should be viewed as an enhancement to the
current stream system and may not require a permit.
• Fish Migration: Placement of boulders and paving stones would be such that
hypothetical fish migration would not be impacted.
• Safety: The current depth of the stream would not be impacted. Therefore, no increase in
hazard to children.
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Step 2: Assuming that 4 µg/L at a location near Knox Street is not achieved by the Step 1
approach alone, drop structures, in reaches of the stream that currently have slow velocities,
would be installed. The current weir in the Holbrook tributary would be raised about one foot
and at least one additional weir /drop structure would be placed just upstream of Knox Street.
Additional drop structures could be installed if appropriate locations are identified. This would
increase the retention time and surface area in the current slow velocity reaches of the stream and
increase volatilization and potentially other attenuation mechanisms. Water flowing over these
structures would impinge on hard surfaces to increase volatilization. Monitoring near Knox
Street over a period of time will determine if Step 2 is adequate or if Step 3 is indicated. Issues
with this approach are as follows:
• COE Permit. Adding drop structures would most likely require a permit.
• Fish migration: Drop structures will prevent any upstream fish migration.
• Safety: Drop structures will increase stream depth and hazard to children.
Step 3: Assuming Steps 1 and 2 are. not successful at meeting the 4 µg/L standard at a
location near Knox Street, additional pilot tests will be conducted to determine the best."active"
system to install. Consideration will be given to life -cycle costs since the Army will be
responsible for O&M costs for up to 50 years.
Step 4: Implement the most efficient system based on pilot test data. .
5.3.4.2 Constructed Wetlands
Constructed wetlands are capable of treating various contaminants in surface water and have
been constructed to treat/polish stormwater and water from sewage treatment plants, acid mine
drainage, landfill leachate, etc. Literature does not specifically indicate any constructed wetlands
specifically for VOCs. Similar to phytoremediation, as discussed under groundwater treatment
(Section 5.2.4), constructed wetlands use a combination of physical, chemical,. and biological
processes to remove/degrade contaminants in the water. Many plants are _capable of removing
VOCs through evapotranspiration and other processes occurring in the subsurface environment.
Constructed wetlands can be constructed to be subsurface or surface flow and to accommodate
stormwater events.
A wetland or swampy area exists in the Beaver Creek drainage just downstream from SWMU
103 between Knox Street and Gruber Road. Monitoring in April 2007 indicated that 1,1,2,2-
tetrachloroethane concentrations decrease to within North Carolina surface water standards prior
to the water reaching Gruber Road. The processes that contribute to concentration decreases are
undefined, but the wetlands/swamp ,in this area may be a contributing factor. Since this area is
outside the currently. defined footprint of the SWMU 103 groundwater plume, this area, is
currently _ unavailable to be incorporated into a natural attenuation remedy for surface water.
However, the data indicate that'a constructed wetland is a potentially effective remedy.
Conceptually, constructed wetlands would be installed in the Holbrook tributary near the
confluence of the. Holbrook tributary and Beaver Creek. Some contouring/excavation would be
necessary to install an influent structure to facilitate the distribution of the incoming water to
allow maximum contact with the wetlands plants and to install a gravel bed to anchor the
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wetland plants. Reeds, cattails, or other regional -appropriate wetland plants capable of removing
VOCs would be planted in a gravel substrate bed. Unfortunately, there is no way to design a
constructed wetland for this purpose (i.e., predict how large of a wetland is necessary to achieve
the desired reduction in concentration).
Railroad tracks are located in this area. In addition, Fort Bragg DPW indicated that the area
surrounding the Holbrook tributary is leased to family housing and use of additional land for the
constructed wetlands outside the boundaries of the existing Holbrook tributary would be
prohibited.
A constructed wetlands sized to accommodate stormwater flows would probably be
prohibitive in this area; however, a constructed wetlands to accommodate the smaller flows that
occur during most of the year might be implernentable. Stormwater flows would have to be
allowed to bypass the wetlands because of the lack of available area to accommodate larger
flows.
Given the implementability concerns, particularly the limited available space, constructed
wetlands are eliminated from further evaluation.
5.3.4.3 Biological Mats
At Aberdeen Proving Ground, Maryland, biological mats were placed in a streambed to treat
1,1,2,2-tetrachloroethane-contaminated groundwater as it upwelled into surface water. The mats
were bioaugmented with the WBC-2 culture, which is a consortium of bacteria developed by
SERIM Laboratories and the US Geological Survey and known to biodegrade 1,1,2,2-
tetrachloroethane. However, to be effective, these ]vats need to stay substantially submerged to
maintain anaerobic conditions necessary for 1,1,2,2-tetrachloroethane biodegradation by WBC-2.
Stream depths at SWMU 103 are too shallow (and sometimes may dry up entirely) to maintain
the necessary anaerobic conditions. Also, to be effective, the mats must cover the entire reach of
the stream where contaminated groundwater discharges. Placing mats in pools behind drop -
structures is unlikely to cover enough of the gaining reaches of the stream to be effective. Given
the effectiveness concerns, biological mats were eliminated from further evaluation.
5.3.5 Stream Segregation
Contaminants in groundwater migrating to surface water in the Holbrook tributary represent a
primary exposure pathway at SWMU 103. This pathway could be eliminated by either lining the
Holbrook tributary with a low -permeability layer [e.g., clay or high -density polyethylene
(HDPE)] that still facilitates stormwater flow to Beaver Creek or enclosing the impacted length
of the Holbrook tributary in a pipe or box culvert, both of which would eliminate groundwater
from migrating to surface water. No flow data are available for the Holbrook tributary or Beaver
Creek in the area of SWMU 103. Based on a water resources map dated 1997, the Beaver Creek
drainage area is approximately 3,356 acres; however, the Holbrook tributary is located only in
the eastern portion of the drainage area and would not receive drainage from the entire 3,356
acres.
The width of the groundwater plume would require a minimum of approximately 3,500 feet of
the Holbrook tributary to be separated from groundwater. The groundwater flow model
developed for SWMU 103 (Appendix K) indicates that the Holbrook streambed would continue
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to act as preferential pathway for the transport of groundwater toward Beaver Creek because it is
a natural topographic low that is sloped toward Beaver Creek. Unfortunately this means that
groundwater water contamination would continue to migrate and ultimately discharge into
Beaver Creek. Segregation of groundwater and Holbrook tributary would merely transfer the
surface water contamination problem further downstream.
Prior to the design of the stream restoration or encasement of the Holbrook tributary in a pipe
or. box culvert, a topographic survey of the Holbrook tributary and the adjacent area would be
required, as well as an evaluation of the potential stormwater flow in the Holbrook tributary. In -
stream restoration would involve contouring and potentially raising the existing streambed of the
Holbrook tributary by 'I to 2 feet between Dougherty Drive and Beaver Creek, which is
approximately 4,018 linear feet. The stream bed would be raised .to ensure surface water is above
the water table. The liner would consist of a gravel/sand bed, followed by a clay layer, and
finally .a HDPE liner. A gravel bed followed by interlocking blocks (specifically used for
streambeds/erosion control) would be placed on top of the HDPE liner. The interlocking blocks
would ultimately fill up with sediment and provide a stable streambed for native habitat to take
hold. The stream restoration would require annual maintenance.
Encasing the Holbrook tributary in pipe or box culvert would require similar construction as
the stream restoration. The 4,018 feet of the tributary would.require less contouring and grading
prior to installation. The pipe or box culvert would be tied into the existing culvert at Dougherty
Drive and sized to accommodate stormwater flow. Catch basins at ground surface would be
located along the length of the pipe to collect surface runoff from adjacent land. Placing the
Holbrook tributary underground would allow more land for. recreational purposes near the
residential housing and would reduce maintenance in the area. An elliptical pipe or box culvert
provides a lower profile for the water transport than a circular pipe. Box culverts tend to be
installed where structural concerns exist and are more expensive than piping.
Given the anticipated low effectiveness and high cost of these alternatives, stream
restoration/segregation was not retained for further evaluation.
5.3.6 Monitoring
Monitoring of surface water will be required to assess contaminant concentrations, ensure the
protection of human health and the environment, and evaluate the performance of an
implemented corrective action, and would be .required as part of any corrective action.
Monitoring of impacted media, including surface water, is .discussed under Section 5.2.11.
Monitoring is retained for further evaluation in combination with other alternatives.
5.4 'CORRECTIVE ACTION ALTERNATIVES
.The process options/technologies retained following the screening step were. combined in.
various ways to develop site -wide corrective action alternatives that would meet the RROs of
protecting human health and environment (Section 4.2). All of the corrective actions would have.
some level of institutional controls to ensure protection of human health during . the
implementation period and monitoring to evaluate the performance of the alternative. The
following three site -wide corrective action alternatives were identified to meet the RROS.
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Alternative 1: MNA, Engineered Aeration/Volatilization of Surface Water, Institutional
Controls, and Monitoring .
• Institutional controls to prevent the use of groundwater and surface water.
• Fencing and signs along the Holbrook tributary to reduce exposure to surface water.
• MNA of the groundwater contamination.
• Annual soil gas monitoring around Holbrook Elementary School.
• Engineered volatilization of VOCs in surface water.
• Surface water and groundwater monitoring to evaluate performance.
This alternative would require a long-term monitoring program. Engineered aeration systems
to increase volatilization of chlorinated solvents in surface water within the footprint of the
SWMU 103 groundwater plume would be installed using a step -wise approach until surface
water standards are met at the point of compliance.
Alternative 2: Source Area Treatment Using Enhanced Bioremediation, MNA,
Engineered Aeration/Volatilization of Surface Water, Institutional Controls, and
Monitoring
• Institutional controls to prevent the use of groundwater and surface water.
• Enhanced bioremediation using anaerobic reductive dechlorination in groundwater in the
source area, which was defined as the location of the former Mallonee Village Gas
Station.
• MNA for remaining groundwater contamination.
• Engineered volatilization of VOCs in surface water.
• Annual soil gas monitoring around Holbrook Elementary School.
• Long-term surface water and groundwater monitoring.
The active portion of the remedial alternative would treat groundwater by enhanced
bioremediation using anaerobic reductive dechlorination in the source area, which was defined as
the immediate area of the former Mallonee Village Gas Station, with the goal to permanently
reduce dissolved contaminant concentrations by approximately 90 percent. MNA would be used
to further reduce the remaining groundwater contaminants to the North Carolina 2L standards.
Engineered aeration systems to increase volatilization of chlorinated solvents in surface water
within the footprint of the SWMU 103 groundwater plume would be installed using a step -wise
approach until surface water standards are met at the point of compliance.
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Alternative 3: Source Area Treatment Using Enhanced Bioremediation, MNA, Pump -
and -Treat Contaminated Groundwater to Protect Surface Water, Institutional Controls,
and Monitoring
• Institutional controls. to prevent the use of groundwater and surface water.
• Enhanced bioremediation using anaerobic reductive dechlorination in groundwater in the
source area, which was defined as the location of the former Mallonee Village Gas
Station.
• MNA for the remaining contaminated groundwater.
• Pump -and -treat groundwater using subsurface drains and activated carbon adsorption
.treatment to prevent contaminated groundwater from discharging to surface water.
• Annual soil gas monitoring around Holbrook Elementary School.,
• Long-term surface water and groundwater monitoring.
The active portion of the' remedial alternative would treat groundwater by enhanced
bioremediation using anaerobic reductive dechlorination in the source area, which was defined as
the immediate area of the former Mallonee Village Gas Station, with the goal to permanently
reduce dissolved contaminant concentrations by approximately 90 percent. MNA would be .used
to further reduce the remaining groundwater contaminants to the North Carolina 2L standards. A
series of subsurface drains would be used to extract enough groundwater to prevent migration of
contaminants to surface water. Extracted groundwater will be treated with activated carbon and
discharged to Beaver Creek and/or Holbrook tributary. Pump -and -treat would continue until
enhanced bioremediation reduces the contaminant flux such that concentrations of VOCs in
surface water will not exceed RGOs.
5.4.1 Evaluation Factors
Based on the results of the technology screening, the retained technologies were combined
into site -wide corrective action alternatives that are considered applicable to contaminants
identified in groundwater and surface water at the SWMU 103 site. The alternatives are then
evaluated against RCRA standards as established in the RCRA Corrective Action Plan Guidance
(EPA 1994). These standards are listed below.
Protection of Human Health and the Environment assesses whether the alternative can
adequately protect human health and the environment, over both the short and long terms, from
unacceptable risks posed by contaminants at the site. Overall protection of human health and the
environment draws on other factors assessed under the evaluation criteria —specifically, short-
term effectiveness, long-term effectiveness, and permanence —and on compliance with state and
federal regulations. The criterion assesses how the source of contamination is to be reduced or
controlled, how the site -related risks are to be reduced, and "whether target levels will be attained.
Attain Media Cleanup Standards. The corrective action will be required to attain media
cleanup standards. The cleanup standards established for groundwater and. surface water at
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SWMU 103 are the North Carolina 2L or IMAC standards and North Carolina surface water
standards, respectively.
Control of Source of Releases. The corrective action must stop further environmental
degradation by controlling or eliminating further releases that may pose a threat to human health
and environment. No continuing source to groundwater was identified during the RFI at the
SWMU 103 area. However, contaminated groundwater originating from past releases from the
former Mallonee Village Gas Station (SWMU 103) intercepts surface water in Beaver Creek and
the Holbrook tributary.
Comply with Applicable Standards for Management of Waste. Each corrective action shall
be in compliance with state and federal environmental laws regulations' (e.g., waste
characterization and disposal, underground injection permitting, etc.).
Other Factors
Long -tern: i reliability and effectiveness assesses the reliability of the remedial action in
meeting the RROs. The assessment of long-term effectiveness is made considering the factors
described below.
• The magnitude of the residual risk .to human health and environmental receptors
remaining from untreated waste or treatment residues left at the conclusion of the remedial
activities. The characteristics of the waste to be considered should include its volume,
toxicity, mobility, and propensity to bioaccumulate.
An assessment of the long-term reliability of engineering and institutional controls to
provide continued protection from untreated waste or treatment residues, including an
assessment of the type, degree, and adequacy of long-term management [including
engineering controls, monitoring, and operations and maintenance (O&M)] required for
untreated waste or treatment residues remaining at the site and the potential need for
replacement of the action and the continuing need for repairs to maintain the performance
of the remedy. .
Reduction in the toxicity, mobility, or volume of wastes through treatment addresses the
degree to which actions employ treatment technologies that permanently and significantly reduce
the toxicity, mobility, or volume of the hazardous substances. The ability of an alternative to
reduce toxicity, mobility, or volume is not considered under this criterion unless the alternative
accomplishes the reduction through treatment. The following specific factors are considered:
• treatment process;
• amount of hazardous materials that would be treated;
• degree of reduction in toxicity, mobility, or volume, including how the principal threat is
addressed through treatment;
• degree to which the treatment is irreversible;
• type and quantity of treatment residuals that would remain following treatment; and
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• degree to which the alternative satisfies the preference for treatment.
Short-term effectiveness of an alternative is evaluated relative to its effect on human health
and the environment during implementation of the corrective action. The short-term
effectiveness assessment is based on four key factors:
• short-term risks that might be posed to the community during implementation of an
alternative,
• potential for impacts on workers during construction and the effectiveness and reliability
of protective measures,
• potential environmental impacts of the action and the effectiveness and reliability of
mitigative measures during implementation, and
• time until objectives are achieved.
Implementability refers to the ease or difficulty of deploying the alternatives. Specific factors
used in assessing implementability include those listed below. .
• Technical feasibility, including technical difficulties and unknowns associated with the
construction and operation of a technology; reliability of the technology; ease of
undertaking additional remedial actions, and ability to monitor the effectiveness of the
remedy.
Administrative feasibility, including activities needed to coordinate with other offices and
l agencies and the ability and time required to obtain any necessary approvals and permits
from other agencies (for,off--site actions).
• Availability of services and materials, including the availability of adequate off -site
treatment, storage capacity, and disposal capacity and services; necessary equipment and
specialists and provisions :to ensure any necessary, additional resources; services and
materials; and prospective technologies.
Cost. The cost of an alternative reflects the capital and O&M. requirements and provides an
estimate of its dollar cost. The costs estimated in this report are based on Parsons proposal costs
to conduct each of the alternatives described, which in turn were based on quotes from suppliers,
generic unit costs, vendor information, cost -estimating guides, prior experience, and other
information. The primary methodology used is a quantity takeoff method in which costs are
calculated based on a unit cost multiplied by a quantity. The cost estimates were developed using
CY 2006 dollars, with no discount factors. The costs presented in the detailed description of
alternatives are prepared for guidance in project evaluation and implementation and based on
nondiscounted cost. They are believed to be accurate within a range between -30 and +50% of
the actual costs, in accordance with EPA guidance. The actual costs for these actions could be
higher than estimated because of unexpected site conditions and the potential for delays in taking
the action. Correspondingly, costs could be lower if construction efficiencies are achieved. A
summary of the nondiscounted cost estimate for each alternative is presented in Table 5-3.
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5.4.2 Evaluation of Corrective Action Alternatives
The corrective action alternatives are summarized in Table 5-4, along with the associated
levels of protection of human health and the costs. The paragraphs below summarize the
evaluation of the corrective action alternatives with respect to the primary evaluation factors of
protection of human health and cost.
5.4.2.1- Alternative 1: MNA, institutional controls, engineered aeration/volatilization of
surface water, and monitoring
Alternative 1 would involve the implementation of institutional controls (fencing and signs),
MNA, engineered aeration/volatilization of contaminated surface water, annual soil gas
monitoring around Holbrook Elementary School, and groundwater and surface water monitoring.
Figure 5-1 presents the general site layout of Alternative 1.
MNA. MNA would require the monitoring of contaminant levels to ensure that the mass of
contamination in the groundwater is reducing with time. Institutional controls and soil gas,
groundwater, and surface water monitoring would be used in conjunction with MNA to ensure
the protection of human health and the environment over the long implementation time required
to meet remedial levels.
The natural attenuation alternative was modeled using the calibrated numerical model
discussed in Section 3.11.2. Modeling estimated that it would require 60 years from CY 2005 to
reduce the concentration of 1,1,2,2-tetrachloroethane in groundwater to less than the remedial
level of 0.17 µg/L (the North Carolina 2L standard). Some uncertainty would be associated with
achieving the groundwater cleanup because _the analytical reporting level of 1,1,2,2-
tetrachloroethane is 1 µg/L. Modeling estimated that it would require approximately 44 years
from CY 2005 to reduce the 1,1,2,2-tetrachloroethane concentration to 1 µg/L, 30 years to reach
the background concentration of 5 µg/L, and 33 years to achieve the remedial level for surface
water (4 µg/L). All of these time estimates are uncertain since (1) the model uses a potentially
conservative but unvalidated decay rate, (2) contaminant flux from the Cape Fear clay was not
incorporated as a source term for the model, and (3) contaminants are present in the upgradient
site -specific background well at concentrations above North Carolina 2L standards.
Institutional Controls. Institutional controls would include the restriction of groundwater use
at SWMU 103. Restrictions on groundwater use for consumption and irrigation would be
implemented for the life of this remedial alternative, estimated to be 62 years (2 additional years
added for confirmatory sampling, reporting, and well abandonment). Access to Holbrook
tributary surface water, where it exceeds surface water standards, will be achieved with a
combination of new and existing fencing. New fencing will match the existing 6-foot-high
vinyl -covered chain link. Signs would also be installed along Beaver Creek and the Holbrook
tributary informing persons of the potential contamination in the surface water. Signs along the
Holbrook tributary would be installed on either the new fence or the existing fence, while signs
along Beaver Creek would be installed on metal posts. The administrative and groundwater -use
restrictions would be implemented during the period of ownership by DoD through restrictions
imposed by the BMP. The BMP would be an effective tool for prohibiting installation of potable
water wells at the site while the property is under DoD ownership. Groundwater is not currently
used as a source of drinking water at the site. Institutional controls prohibiting the use of
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groundwater in the future would be effective at protecting human health from the elevated levels
of COCs.in the groundwater.
Soil Gas Monitoring. Crawlspace air and soil gas sampling has determined that VOCs are
not impacting indoor air quality at Holbrook Elementary School. To ensure that the school is not
impacted by vapor intrusion in the future, soil gas monitoring would be conducted at existing
representative monitoring points..A total of 18 soil gas monitoring points surround the perimeter
of the Holbrook Elementary School buildings and within open areas between separate school
buildings (Figure 2-13). The soil gas sampling would be conducted from all 18 sampling points
for one more year. If the 2006 soil gas sampling results are confirmed, and groundwater VOC
concentrations do not increase, the sampling network will be optimized. It is anticipated that
three upgradient monitoring points (SG1, SG14, and SG16) will continue to be monitored
annually. Soil vapor samples would be collected in accordance with EPAMethod TO-15 and
analyzed for VOCs. Soil gas samples would be collected annually prior to the beginning of the
school year. The results of the soil gas sampling would be evaluated relative to EPA vapor
intrusion screening criteria to ensure that Holbrook Elementary School remains safe from vapor
intrusion.
Engineered Aeration/Volatilization of Surface Water. Surface water will treated using
aeration/volatilization within the footprint of the groundwater plume to meet the North Carolina
surface water standard (4 µg/L of 1,1,2,2-tetrachloroethane). The most downstream extent of the
groundwater plume (currently understood to be where Beaver Creek flows under Knox Street)
would be the point -of -compliance to meet surface water standards. The engineered
aeration/volatilization systems would be implemented using the step -wise approach outlined in
} Section 5.3.4.1. The step -wise process would begin with a simple passive aeration system
(roughening the streambed with small boulders) and proceed to more complex aeration solutions
until monitoring shows that the installed aeration/volatilization system is effective at meeting
surface water standards at the point -of -compliance.
Groundwater Monitoring Network. One new monitoring well (MW51) would be installed
to complete the groundwater monitoring network to evaluate the performance of the natural
attenuation alternative. The location of the. new monitoring well is along Sharpe Drive between
MW-29 and MW-31. The initial groundwater monitoring network will consist of 31 wells. The
monitoring well network will be evaluated annually for optimization opportunities. Some
shallow wells can be eliminated from the existing network since contamination is primarily in
the deeper wells.
Performance Groundwater Sampling. Performance groundwater monitoring for MNA
would be performed on an annual basis to evaluate the progress of . natural attenuation. The
location and sampling frequency of wells for performance sampling would be selected based on
evaluation of the results of the previous year's performance sampling. Over the first 10 years, it
is anticipated that some of the interior wells may be moved to a biennial (every other year)
sampling frequency. However, wells near the Holbrook Elementary School and residential areas
would remain on an annual sampling frequency. Groundwater would be analyzed for VOCs and
natural attenuation parameters.
Surface Water Sampling. Effectiveness monitoring will be required during the period that
engineered aeration/volatilization system(s) are implemented to establish whether the
technologies in place are achieving the necessary contaminant reduction. The effectiveness
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monitoring will include sampling above and below treatment zones, conducted on a frequent
basis to provide sufficient data on which to make that determination. Once the successful
technology for remediation of the surface waters is selected, as established through the
effectiveness monitoring, a reduced monitoring schedule can be established. Surface water
would be analyzed for VOCs.
Confirmatory Sampling. Confirmatory groundwater sampling would be conducted for two
years after the completion of the natural attenuation period to ensure that the groundwater
contamination had not rebounded.
Reporting. An annual report would be issued to coincide with the results of the sampling. If
the monitoring frequency is reduced, progress reports would be issued to coincide with
groundwater monitoring. A confirmation report would be issued at the completion of the
confirmatory sampling.
Protection of Human Health and the Environment
Alternative 1 would be protective of human health and environment through a combination of
passive treatment systems (natural attenuation for groundwater and engineered
aeration/volatilization for surface water), institutional controls, and, if necessary, more active
engineered aeration/volatilization (for surface water). Natural attenuation would be used to
reduce contaminant concentrations in groundwater over time. Fencing along the Holbrook
tributary would prevent exposure to surface water. Warning signs along Beaver Creek and the
Holbrook tributary would reduce exposure to the surface water year round. The results of the soil
gas sampling would determine if mitigative measures were necessary to prevent vapor intrusion
at Holbrook Elementary School. These may include lining the crawl spaces and/or ventilating the
crawl spaces or basements. The mitigative measures would be protective of human health to risk
from vapor intrusion.
Institutional controls preventing the use of groundwater for drinking or irrigation would be
implemented to eliminate potential contact (i.e., risk) from the groundwater. This alternative
would provide protection of human health through warning signs and placing and maintaining
legal controls on the. use of groundwater. Institutional controls would be put in place and
maintained by Fort Bragg through the BMP. The SWMU 103 area is expected to remain under
the ownership of the federal government; therefore, sufficient confidence in their long-term
effectiveness is assumed. Groundwater is presently not used for drinking water in the area.
Monitoring of the soil gas, groundwater, and surface water would ensure that contamination is
not migrating or increasing in concentration to an unacceptable degree.
Attain Media Cleanup Standards
Alternative 1 would comply with groundwater and surface water cleanup levels but not in a
short timeframe. The concentration of 1,1,2,2-tetrachloroethane in groundwater would remain
above the North Carolina 2L standards until complete restoration of the aquifer had been
achieved, estimated by modeling to be 60 years from CY 2005. However, modeling also has
estimated that the groundwater concentration of 1,1,2,2-tetrachloroethane will be below the
reporting limit (<1 µg/L) in 44 years from CY 2005 and protective of surface water (4 µg/L) in
33 years from CY 2005. The modeling results did not account for contamination (e.g., 5.1 µg/L
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of 1,1,2,2-tetrachloroethane) detected at the background locations (MW26 and MW27) at
SWMU 103, which could continue to act as a small contaminant recharge area. Modeling results
indicate that it will take 30 years to reach the background level. There is uncertainty associated
with achieving cleanup levels below 5 µg/L due to the background concentration.
Engineered aeration/volatilization will be applied in a step -wise approach until VOCs meet
surface water standards at the point -of -compliance.
Legal controls implemented under this alternative would prevent ingestion of contaminated
drinking water, and long-term monitoring would demonstrate when the aquifer was restored to
the North Carolina 21, standards.
Control of Source of Releases
The groundwater contamination originating from the former Mallonee Village Gas Station
(SWMU 103) is from past releases to the subsurface from a leaking solvent UST that was
removed. No current source is located at SWMU 103; therefore, there are no ongoing primary
sources of contamination to groundwater to control. However, VOCs in the clay formation
underlying the surficial water -bearing zone may represent a continuing secondary source of
contamination: The groundwater is the source of the contamination in surface water. Natural
attenuation will be used to reduce the VOC concentrations in groundwater to levels that will be
below cleanup goals in surface water. Modeling indicated that this process could take 33 years.
In the interim, engineered in -stream aeration/volatilization will remove VOCs in surface water.
Comply.with Applicable Standards for Management of Waste
Alternative 1 would comply with state and federal requirements. Investigation -derived waste
(IDW) generated during the installation of -groundwater wells would be characterized to
determine waste characteristics. Waste would be disposed of in accordance with all state and
federal regulations.
Other Factors
Long -Term Reliability and Effectiveness. The long-term effectiveness and permanence of
natural attenuation would be dependent on the establishment and maintenance of institutional
controls and the decrease with time in contaminant concentrations as predicted by modeling.
Institutional controls would be established- to eliminate the potential for exposure to humans and
the environment, thereby reducing the potential risk. Some uncertainty is associated with the
modeling of natural attenuation and'F&T of the contaminants. However, the model would be
confirmed/updated as additional data are collected and analyzed. .
Engineered in -stream aeration/volatilization. would be applied in a step -wise approach until
they are effective for removal of VOCs in surface .water.
Reduction in the Toxicity, Mobility, or Volume of. Wastes. Alternative 1 uses primarily
passive treatment (natural attenuation and/or volatilization) to treat the contaminants in
groundwater and surface water. A more active engineered aeration/volatilization system will be
used to treat contaminants in surface water if passive volatilization is ineffective. Except for the
engineered aeration/volatilization system for surface water, Alternative 1 does not meet the
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statutory preference for employing treatment technologies that permanently reduce the toxicity,
mobility, or volume of the contaminants. There would be immediate reduction in toxicity,
mobility, or volume of the contaminants as a result of implementing this alternative in surface
water only. Natural attenuation would require approximately 33 years before it would remove
contaminants in groundwater to levels protective -of the surface water. Volatilization would
reduce the toxicity of any remaining VOCs migrating to surface water.
Groundwater concentrations have been decreasing since January 2003 and modeling has
predicted that the aquifer will be restored to below the North Carolina 2L standards in 60 years
from CY 2005. Annual groundwater monitoring would be used to confirm the continued
decrease in toxicity in groundwater contaminants. Surface water sampling would be used to
confirm that volatilization was removing contaminants and therefore reducing the toxicity.
Short -Term Effectiveness. Short-term impacts would be minimal for Alternative 1. Impacts
to the environment or community would not be expected to occur from implementation of any of
the actions under this alternative. Workers and the community -would have limited exposure to
contaminated groundwater during the installation of the monitoring well, engineered aeration
system, and sampling (soil gas, groundwater, and surface water) activities resulting in the
potential for few short-term risks. Health and safety controls in accordance with Occupational
Safety and Health Agency (OSHA) requirements would be implemented to mitigate, prevent,
and limit potential exposure of workers during these activities.
The total time to implement this alternative is estimated to be 62 years. According to the
modeling results, it would take approximately 60 years from CY 2005 to meet the North
Carolina 2L standards (cleanup levels). Confirmatory sampling would be performed for two
years after the completion of the natural attenuation period.
Implementability. Alternative 1, MNA and in -stream aeration/volatilization, is readily
implementable because no active remedial actions would be taken that would require extensive
construction or permitting. A modest amount of construction and possibly a permit would be
required for the in -stream aeration/volatilization system. Materials, equipment, and labor for
installation of monitoring wells, the aeration/volatilization system, and sampling (soil gas,
groundwater, and surface water) are readily available.
Establishment of the groundwater -use restrictions will require additional time and effort for
development, preparation, and processing of the necessary paperwork. Administrative provisions
already exist to allow for incorporation of groundwater -use restrictions into the BMP. Collection
of annual groundwater samples will require additional time and resources; however,
subcontractors and laboratories needed to perform this work are readily available.
Cost. The capital cost for the installation of the monitoring well, the in -stream
aeration/volatilization system, fencing, and baseline sampling would be approximately $661,000.
O&M costs were estimated for a 60-year period and would be approximately $2,639,150. O&M
costs would include annual groundwater and surface water sampling for 60 years from CY 2005.
Samples would be analyzed and validated. O&M costs would also include reports, a final review
and confirmation report, and monitoring well abandonment. The total cost for Alternative 1
would be approximately $3,300,150. Detailed costs for this alternative are presented in Table 5-
3.
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5.4.2.2 Alternative 2: Source treatment using enhanced bioremediation, WiA,
engineered aeration/volatilization of surface water, institutional controls, and monitoring
Alternative 2 would use enhanced bioremediation via anaerobic reductive dechlorination to
treat contamination in groundwater and saturated soil located in the source area, which was
defined as the previous location of the former Mallonee Village Gas Station (Figure 5-2). The
source area has concentrations of 1,1,2,2-tetrachloroethane in groundwater ranging from
approximately 250 to 660 µg/L, and the RFI indicated low levels of residual chlorinated solvents
absorbed onto the surface of the clay at the confining layer located'at approximately 65 feet bgs.
After treatment of the source area, natural attenuation would be used to treat the remaining
dissolved concentrations in groundwater until the concentrations of 1,1,2,2-tetrachlorethane
reach the North Carolina 2L standard (0.17 µg/L). Engineered aeration/volatilization would be
used to treat VOCs in surface water in the same manner as described in Alternative 1.
Institutional controls ,and soil gas, groundwater, and surface water monitoring would be used in
conjunction with MNA to ensure the protection of human health and the environment over the
long implementation time required to.meet final remedial levels in groundwater.
As discussed in Chapter 4, Screening of Technologies, enhanced biodegradation using
anaerobic reductive dechlorination has been successfully used to biologically degrade
chlorinated solvents in saturated soil and groundwater. Analytical data from groundwater from
the source area of SWMU 103 showed that anaerobic 'reductive dechlorination has likely
occurred in the past due to commingling of fuel and chlorinated solvent contamination in the
shallow groundwater.
Source Treatment Using Enhanced Bioremediation. The purpose of applying enhanced
anaerobic bioremediation technology to the SWMU 103 source area (former gas station) is to
reduce contaminant mass present in the subsurface and thereby reduce long-term contaminant
mass loading to Holbrook Tributary and Beaver Creek. The mixed substrate for this application
will consist of a soluble substrate such as high fructose corn syrup to provide an immediate mass
of bioavailable organic carbon to create anaerobic, reducing conditions, and vegetable oil to
provide a slow release source of organic carbon to drive reductive dechlorination over the long.
term. This mixture typically supports anaerobic biodegradation for 2 to 3 years. Organic
substrate will be targeted for the lower 15 feet of the Middendorf aquifer where VOC
concentrations are highest. Organic substrate will also absorb into the top of the confining clay
unit (believed to be the primary source of continuing contamination) and enhance biodegradation
of 1,1,2,2-tetrachloroethane and TCE diffusing. out of the clay. A pH amendment product such as
sodium bicarbonate will also be added to maintain neutral pH conditions within each reaction
area. Degradation . products (cis 1,2-DCE and vinyl chloride) are more rapidly degraded in
neutral pH conditions, making pH buffering an important factor in successful enhanced
bioremediation applications.
The injection well network in the source area will consist of 42 direct push injection points
installed in a grid orientation. The spacing between the injection points will be approximately 10
feet to ensure adequate substrate distribution. Each of the injection points will be advanced to.
the top of the Cape Fear Formation Clay so that the substrate is injected in the bottom portion of
the Middendorf Formation. Half of the injection points will be completed as temporary small
diameter wells to allow for future injections of amendments and additional organic substrate if
necessary. During the initial injection approximately 800 to 1,000 gallons of organic substrate
mixture and pH amendment will be injected areach point. Based on the radial flow in the.deep
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groundwater, this design should produce anaerobic conditions in at least a 10,000-square foot
area beneath the former solvent UST area (Figure 5-2).
After the first six months of performance monitoring, the geochemical data and progress of
1,1,2,2-tetrachloroethane and TCE degradation in the source area will be reviewed. If
degradation is lagging and conditions are sufficiently anaerobic, a supplemental injection of
approximately 300 to 500 gallons of dilute bioaugmentation culture and a pH amendment may be
added into each of the small diameter wells. The bioaugmentation culture will consist of a non-
pathogenic, naturally occurring combination of microbial strains known to be capable of
complete dechlorination of 1,1,2,2-tetrachloroethane and its degradation products (cis 1,2-DCE
and vinyl chloride). The bioaugmentation culture will be -provided by SIREM Laboratories,
which has developed a bioaugmentation product called WBC-2 that was specifically developed
for the degradation of 1,1,2,2-tetrachloroethane in conjunction with the US Geological Survey.
WBC-2 has been field tested at Aberdeen Proving Ground for the Army and has been shown to
be very effective at completely degrading 1,1,2,2-tetrachloroethane. The application of WBC-2
at Aberdeen Proving Grounds was accomplished in biological mats that were placed in a
streambed and promoted biodegradation of contaminated groundwater as it upwelled into the
stream. The goal of the organic substrate injection is to achieve a 90-percent average 1,1,2,2-
tetrachloroethane reduction within the source area. A second injection of organic substrate may
be applied to the SMWU-103 source area in the event that concentrations of 1,1,2,2-
tetrachloroethane rebound above 100 µg/L within the source area within 3 years of the initial
injection.
MNA of Remaining Groundwater Contamination. In addition to active bioremediation in
the source area, MNA will be employed as described in Alternative 1. The calibrated numerical
model discussed in Section 3.11.2 predicted 60 years for MNA alone to reach the North Carolina
2L standard (0.17 µg/L) and 33 years to reach the surface water remedial level (4 µg/L). These
predictions may be optimistic since (1) the model uses a potentially conservative but. unvalidated
decay rate, and (2) contaminant flux from the Cape Fear clay was not incorporated as source
term for the model. However, a 90-percent source reduction in contaminant mass through
enhanced bioremediation would eventually produce much lower VOC concentrations beneath
Holbrook school and in surface water. Based on groundwater velocities of 200-500 feet per year
at the site, the time for groundwater emanating from the source area to reach Holbrook Tributary
behind the school (-1000 feet) is 2 to 5 years. Although 1,1,2,2-tetrachloroethane will move
slower than groundwater flow due to the effects of retardation, it is probable that the impact of
source treatment and NINA will begin to reduce groundwater concentrations entering surface
water within 10 years. Treatment and institutional controls to protect surface water would
continue until surface water meets clean-up standards, which will probably take substantially
longer.
Institutional Controls. Institutional controls would include the restriction of groundwater use
at SWMU 103. Restrictions on groundwater use for consumption and irrigation ,would be
implemented for the life of this remedial alternative, estimated to be nearly as Tong as for
Alternative 1 (60 years).
Prevention of access to surface water at locations where VOC levels exceed surface water
standards in Holbrook Tributary will be achieved with a combination of new and existing
fencing. New fencing will match the existing 6-foot vinyl -covered chain link. Signs would also
be installed along Beaver Creek and the Holbrook tributary prohibiting access and contact with
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surface water. Groundwater treatment should begin to reduce the flux of contaminants to surface
water standards within 10 years. Attainment of surface water standards will likely take
considerably longer, at which time institutional controls could be removed.
The administrative and groundwater -use restrictions would be implemented during the period
of ownership by DoD through restrictions imposed by the BMP. The. BMP would be an effective
tool for prohibiting installation of potable water wells at the site while the property is under DOD.
ownership. Groundwater .is not currently used as a source of drinking water at the site.
Institutional controls prohibiting the use of groundwater in the future would be effective at
protecting human health from the elevated levels of COCs in the groundwater.
Groundwater Monitoring Network. One new monitoring well (MW51), would be installed
to complete the groundwater monitoring network to evaluate the performance of the natural
attenuation alternative. The location of the new monitoring well is along Sharpe Drive between
MW-29 and MW-31, as presented in Figure 5-2. The initial groundwater monitoring network
will consist of 31 wells. The monitoring well network will be evaluated annually for
optimization opportunities. Some shallow wells can be eliminated from the existing network
since contamination is primarily in.the deeper wells.
Performance Groundwater Sampling. Groundwater will be sampled quarterly during the
first year following carbon substrate injection to evaluate the performance of anaerobic reductive
dechlorination. Thereafter, performance monitoring will be conducted annually. Groundwater
from wells in the vicinity of the carbon substrate injection would be sampled -and analyzed for
VOCs, TOC, geochemical parameters and pH. Results of the groundwater sampling will be used
to evaluate the effectiveness . of anaerobic reductive .dechlorination and develop plans for
subsequent bioaugmentation and carbon substrate injections as necessary.
Performance groundwater monitoring for MNA would occur on an annual basis to evaluate
the progress of the natural attenuation. The location and sampling frequency of wells for
performance sampling would be selected based on evaluation of the results of the previous year's
performance sampling. Over the first 10 years, it is anticipated that. some of the interior wells
may be moved to a biennial sampling frequency. However, wells near the Holbrook Elementary
School and residential areas would remain on an annual sampling frequency. Groundwater
would be analyzed for VOCs and natural attenuation parameters.
Soil Gas Monitoring. Crawlspace air and soil gas sampling has determined that VOCs are
not currently impacting indoor air quality at Holbrook Elementary School. To ensure that. the
school is not impacted by vapor intrusion in the future, soil gas monitoring would be conducted
at existing representative monitoring points. A total of 18 soil gas monitoring points surround the
perimeter of the Holbrook Elementary School buildings and within open areas between separate
school buildings (Figure 2-13). The soil gas sampling would be conducted from all 18 sampling
points for one more year. If the 2006 soil gas sampling results are confirmed, and groundwater
VOC concentrations do not increase, the sampling network will be optimized. It is anticipated
that three upgradient monitoring points (SGI, SG14, and SG16) will continue, to be monitored
annually. Soil vapor samples would be collected in accordance with EPA Method TO-15 and
analyzed for VOCs. -Soil gas samples would be collected annually prior to the beginning of the
school year. The results of the soil gas sampling would be evaluated relative to EPA vapor
intrusion screening criteria to ensure that Holbrook Elementary School remains safe from vapor
intrusion.
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Engineered AerationNolatilization of Surface Water. Surface water will be treated using
aeration/volatilization within the footprint of the groundwater plume to meet the North Carolina
surface water standard (4 µg/L of 1,1,2,2-tetrachloroethane). The most downstream extent of the
groundwater plume (currently understood to be where Beaver Creek flows under Knox Street)
would be the point -of -compliance to meet surface water standards. The engineered
aeration/volatilization systems would be implemented using the step -wise approach outlined in
Section 5.3.4.1. The step -wise process would begin with a simple passive aeration system
(roughening the streambed with small boulders) and proceed to more complex aeration solutions
until monitoring shows that the installed aeration/volatilization system is effective at meeting
surface water standards at the point -of -compliance.
Surface Water Sampling. Effectiveness monitoring will be required during the period that
engineered aeration/volatilization system(s) are implemented to establish whether the
technologies in place are achieving the necessary contaminant reduction. The effectiveness
monitoring will include sampling above and below treatment zones, conducted on a frequent
basis to provide sufficient. data on which to make that determination. Once the successful
technology for remediation of the surface waters is selected, as established through the
effectiveness monitoring, a reduced monitoring schedule can be established. 'Surface water
would be analyzed for VOCs.
Confirmatory Sampling. Confirmatory groundwater sampling would be conducted for two
years after the completion of the natural attenuation period to ensure that the groundwater
contamination had not rebounded.
Reporting. An annual report would be issued to coincide with the results of the sampling. If
the monitoring frequency is reduced, progress reports would be issued to coincide with
groundwater monitoring. A confirmation report would be issued at the completion of the
confirmatory sampling.
Protection of Human Health and the Environment
Alternative 2, source treatment using anaerobic bioremediation followed by natural
attenuation and treatment of contaminated surface water using engineered aeration/volatilization,
uses a combination of active and passive treatments to be protective of human health and the
environment. Active treatment using anaerobic reductive dechlorination in the source area would
more rapidly reduce VOC concentrations dissolved in groundwater and reduce the flux of
contaminants from the Cape Fear Formation clays to the groundwater. Active source area
treatment should also result in a more rapid decrease in dissolved VOC concentrations
downgradient of the source area and reduce the flux of contaminants to surface water, shortening
the time that institutional controls and volatilization will be required to meet the North Carolina
surface water criteria. After completion of the engineered treatment of the source area, natural
attenuation would then be implemented to remove the remaining contaminants in groundwater to
below remedial levels (North Carolina 2L or IMAC standards). Upon achieving groundwater
remedial levels, contaminants would no longer pose a risk to potential receptors; therefore, the
alternative would have long-term effectiveness. Because the active portion of the alternative is an
in -situ process, there would be little disturbance of soil or groundwater over the short term that
might result in an impact to human health or the environment. The active treatment alternative
would also reduce the toxicity of the contaminants in groundwater and subsequent migration to
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surface water. Source treatment would result in an overall reduction in the volume of
contaminants in groundwater.
The soil gas sampling would ensure that Holbrook Elementary School remains safe from
vapor intrusion.
Institutional controls preventing the use of groundwater for drinking or irrigation would be
implemented to eliminate potential contact (i.e., risk) from the groundwater during the natural
attenuation period. Therefore, the overall protection of human health and the environment during
the natural attenuation period of this alternative is dependent upon the establishment and
maintenance of institutional controls. Institutional controls would be instituted and maintained by
Fort Bragg through the BMP. The SWMU 103 area is expected to remain under the ownership of
the federal government; therefore, sufficient confidence in their long-term effectiveness is
assumed.
Maintaining the existing fencing, installing new fencing along the Holbrook tributary where
surface water VOC concentrations exceed regulatory criteria, and installing warning signs along
the Holbrook tributary and Beaver Creek would reduce the 'potential for exposure to
contaminated surface water.
Monitoring of the soil gas, groundwater, and surface water would confirm the performance of
the active remediation and ensure that contamination is not migrating or increasing in
concentration to an unacceptable degree.
Attain Media Cleanup Standards
Alternative 2 would reduce the groundwater contaminant flux to surface water, such that -
surface water clean-up levels would be met and institutional controls and engineered
volatilization could be discontinued. Based on estimates of travel times from the source area to
Holbrook tributary, surface water should start to be impacted by lower contaminant loading
within 10 years. Groundwater would eventually attain the North Carolina 2L or IMAC standards
but not within a short timeframe. The concentrations in groundwater would remain above the
North Carolina 2L standards until complete restoration of the aquifer is achieved, which will
likely take decades.
Engineered aeration/volatilization systems would be implemented in a step -wise approach
until one or more technologies successfully remove VOCs from surface water so that surface
water standards are met at the point -of -compliance.
Legal controls implemented under this alternative would prevent ingestion of contaminated
drinking water, and long-term monitoring would demonstrate when the aquifer was restored to
the North Carolina 2L standards.
Control of Source of Releases
The groundwater contamination originating from the former Mallonee Village Gas Station
(SWMU 103) results from past releases to the subsurface from leaking USTs that were removed.
No current source has been identified at SWMU 103; however, the primary source of the
groundwater contamination is hypothesized to be residual contamination adsorbed onto the soil
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matrix. Active source treatment is targeted for the area where contaminants diffuse from the
confining clay layer into' the aquifer. Organic substrate will diffuse into the clay and create
conditions that will result in biodegradation of contaminants as they migrate into the aquifer.
The groundwater is the source of the contamination in surface water. The source area
treatment will reduce the VOCs in groundwater to levels below cleanup goals (North Carolina
surface water standards). Until the contaminant flux from groundwater to surface water is
reduced, surface water quality criteria will be met by engineered aeration/volatilization.
Comply with Applicable Standards for Management of Waste
Alternative 2 will comply with state and federal requirements. An Underground Injection
Control (UIC) Program Permit will be required prior to the injection of any substance into the
subsurface. All of the representative injectants. evaluated in the conceptual design for anaerobic
reductive dechlorination are approved substances for injection by the state of North Carolina.
IDW generated during the installation of injection wells and groundwater monitoring wells
will be characterized to determine waste characteristics. Waste will be disposed of in accordance
with all state and federal regulations. To date, liquid and solid waste generated during the RFI
have been characterized as non -hazardous.
Other Factors
Long -Term Reliability and Effectiveness. Alternative 2 achieves long-term reliability and
effectiveness through a combination of active and passive treatment technologies. The active
treatment in the source area biologically degrades contamination in groundwater in the source
area. The treatment of contamination in the source area will reduce the contaminant flux from the
Cape Fear Formation clay to the aquifer and eventually reduce the flux of contamination from
groundwater to surface water. This will expedite the natural attenuation process. Engineered
aeration/volatilization processes in Holbrook tributary and Beaver Creek will achieve North
Carolina surface water criteria until the source area treatment can reduce the flux of
contamination from groundwater to surface water.
The source area treatment would be designed to maximize the chances of success. The
geochemistry (i.e., high DO, positive ORP, nitrate, sulfate, etc.) of the subsurface at SWMU 103
is not naturally conducive to anaerobic reductive dechlorination. Therefore the injection of
carbon substrate would be targeted for to a limited volume to provide enough substrate to
maximize chance of creating the desired strongly reducing conditions. The injected volume will
be the deeper portions of the surficial aquifer in the source area (former gas station) to allow
contaminants to degrade as they migrate away from the source.
After source treatment, the remaining contamination in groundwater would be allowed to
naturally attenuate to below remedial levels (North Carolina 21, or IMAC standards). The
timeframe is uncertain but removal of the contaminant source will expedite the attainment of
remedial levels. The long-term effectiveness and permanence of natural attenuation depends on
the establishment and maintenance of institutional controls, and the decrease with time in
contaminant concentrations. Institutional controls would be established to minimize potential
exposure to humans and the environment, thereby reducing the potential risk from groundwater
and contact with surface water. Some uncertainty is associated with the modeling of natural
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attenuation and F&T of the contaminants. However, the monitoring will evaluate the
effectiveness of natural attenuation processes.
Reduction in the Toxicity, Mobility, or Volume of Wastes. Alternative 2 uses active
treatment to reduce the toxicity of the groundwater in the source area to levels protective of
surface water. Therefore, Alternative 2 meets the statutory preference for employing treatment
technologies that permanently reduce the toxicity, mobility, or volume of the contaminants. After
active source area treatment is complete, Alternative 2 uses passive treatment to reduce the
remaining low level of contaminants in groundwater until the concentrations reach the North
Carolina 2L standard.
Groundwater monitoring would be used to confirm the continued decrease in toxicity in
groundwater contaminants. Surface water sampling would be used to confirm that engineered
aeration/volatilization is effective at removing contaminants above surface water criteria until the
flux of groundwater contaminants is sufficiently reduced that surface water treatment is no
longer necessary.
Short -Term Effectiveness. Short-term impacts would be minimal for Alternative 2; however,
injections would be performed at the source area (at the former gas station that is located near
Holbrook Elementary School and residential areas) for up to a three-year period. Negative
impacts to the environment or community would not be expected to occur from implementation
of any of the actions under this alternative. Workers would have limited exposure to
contaminated groundwater during the installation of the monitoring well, injection of the
substrate, and sampling (soil gas, groundwater, and surface water) activities, thus resulting in the
potential for few short-term risks. There would be no exposure of the general community to
contaminated media during performance. of these activities. The anaerobic bioremediation
substrates and amendments selected for application are innocuous substances and have been
approved for injection by the state of North Carolina. Health and safety controls in accordance
with OSHA requirements would be implemented to mitigate, prevent, and limit potential
exposure of workers during these activities.
The intermediate degradation products (e.g., vinyl chloride) of anaerobic reductive
dechlorination are relatively toxic and, therefore, potential migration would have to be monitored
to ensure that the degradation products wore not causing an increased vapor intrusion risk in
Holbrook Elementary School or degradation of surface water quality in the Holbrook tributary.
These daughter products have likely been produced in the past due to commingling of fuel and
chlorinated solvent plumes, but accumulation of daughter products has not been observed. The
natural aerobic conditions of the aquifer are expected to rapidly degrade these daughter products
prior to their migrating under Holbrook Elementary School or into the Holbrook tributary.
However, daughter products will be produced in the immediate vicinity of the substrate injection,
therefore substrate injections have not been recommended close to inhabited buildings such as
Holbrook Elementary School.
Without active treatment, natural attenuation alone may take 60 years or longer to achieve
clean up criteria. Alternative 2 will shorten this timeframe, but reaching the very low North
Carolina 2L standards (cleanup levels) across the entire site will still take decades.
Implementability. Alternative 2 is readily implementable, but addition of substrate injection
adds a (manageable) layer of complexity relative to Alternative 1. Materials, equipment, and
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labor for installation of injection wells, monitoring wells, injection of additives to promote
anaerobic reductive dechlorination, and sampling (soil gas, groundwater, and surface water) are
readily available. The manufacturers of anaerobic reductive dechlorination injectants have
sufficient capacity; however, coordination with vendors needs to occur so that sufficient
quantities are available for each injection event and supplies will not be interrupted.
The initial substrate injection task will likely take approximately 3-4 weeks to accomplish and
will involve a two -person field crew, direct push rig, pumps, hoses, tanks, and mixers. IDW
generation would be minimal. Disruptions to any site activities would be small-scale and very
temporary. Implementability issues related to any required follow-on activities (i.e.,
bioaugmentation and second substrate injection) would be similar to, or less complex than, those
related to the initial substrate injection.
Establishment of groundwater -use restrictions will require additional time and effort for
development, preparation, and processing of the necessary paperwork. Administrative provisions
already exist to allow for incorporation of groundwater -use restrictions into the BMP. Collection
of annual groundwater and surface water samples will require additional time and resources;
however, subcontractors and laboratories needed to perform this work are readily available.
Cost. The capital cost for the installation of injection wells and monitoring wells, substrate
and other amendments for injection, and baseline sampling would be approximately $961,000.
O&M costs were estimated for a 60-year period and would be approximately $2,524,150. O&M
costs are estimated based on annual groundwater monitoring for 60 years and surface water
monitoring for 25 years. Samples would be analyzed and data would be validated. O&M costs
would also include reports, a final review and confirmation report, and monitoring well
abandonment. The total cost for Alternative 2 would be approximately $3,485,150. Detailed
costs for this alternative are presented in Table 5-3.
5.4.2.3 Alternative 3: source area treatment using enhanced bioremediation, MNA,
pump -and -treat contaminated groundwater to protect surface water, institutional controls,
and monitoring
Alternative 3 is the same as Alternative 2 except in the way that surface water is protected. Deep
groundwater collection trenches will be installed in key locations upgradient of Holbrook
Tributary and Beaver Creek to more quickly reduce contaminant discharge to surface water.
Groundwater will be intercepted in deep, gravel -filled interception trenches and pumped from
four sumps located at the downgradient end of each trench. Trenches will be located 70-300 feet
upgradient of the creeks and pumping levels will be regulated to prevent drying up of the creeks.
Collected groundwater will be pumped through a simple activated carbon system prior to
discharge back to surface waters. Figure 5-3 illustrates source area treatment and trench
locations for Alternative 3. Surface water criteria would be met along the entire reach of the
streams in a short period of time, eliminating the need for institutional controls and
aeration/volatilization treatment of surface water. The following conceptual design for
Alternative 3 describes only the differences in design between Alternatives 2 and 3. Similar
design features between Alternatives 2 and 3 are identified but their details are referenced.
Source Treatment using Enhanced Bioremediation. Source treatment using enhanced
bioremediation by anaerobic reductive dechlorination would be the same as described above for
Alternative 2. Source treatment will reduce the flux of contaminants from the source area to
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surface water, eventually eliminating the need for the pump -and -treat system. For purposes of
this evaluation, source area treatment is estimated to reduce groundwater contamination so that
the pump -and -treat system can be turned off in 25 years.
Groundwater Interception Trench and Treatment System: In. order to more quickly
achieve surface water standards, four deep groundwater interception trenches would be installed
on the north side of Holbrook Tributary and East side of Beaver Creek to remove and treat
1,1,2,2-tetrachloroethane-contaminated groundwater before it enters surface waters.
Groundwater entering Holbrook Tributary has a more significant impact, based on surface water
exceedances of .the current 4 µg/L North Carolina surface water standard for 1,1,2,2-
tetrachloroethane. For this reason, three of the four groundwater collection trenches would
intercept and treat groundwater entering Holbrook Tributary. One trench will intercept
groundwater before it reaches the school and avoids difficult and disruptive construction. near the
primary school grounds.
Using a continuous trenching machine, 1,350 feet of gravel -filled trench would be installed in
four segments as shown on Figure 5-3. Segments Al and A2 will. be completed to the maximum
35-foot depth of the trencher. Although this is not deep enough to reach the Cape Fear clays,
these partially penetrating trenches will be pumped to create upward flow of deeper groundwater
into the trench. This trench design will create a significant cone of depression that will capture
groundwater flowing from the source area under the Holbrook Elementary School. Based on
2005 utility drawings of this area, one storm sewer will need to be removed and repaired -to
complete segment A2. The other trench segments have been sited to avoid known utilities in
r these areas. Dig permits will be used to verify a clear path for the trencher. Segments 131 and B2
will be completed to a depth of 30 feet to contact the top of the Cape Fear clays. A 16-inch sewer
force main will be left untouched between the B 1 and B2 segments. Interceptor trench locations
were selected to avoid any trenching in sensitive habitats or near school buildings.
As shown on Figure 5-4, each trench segment will include a 6-inch HDPE perforated pipe that
drains to an 18-inch sump installed at the downgradient end of the segment. The trenching
machine is fitted with special attachments to install the 6-inch piping and sumps. Water levels in
the trench and sump will be controlled with a small 'h-horsepower (HP) pump. The pumping
level in the trench will be set at a depth that is at or slightly below the elevation of the Holbrook
Tributary. This level control will allow the trench to mimic the potentiometric surface of the
stream and collect groundwater that would otherwise have discharged to surface water. Because
the interception trench is located 100 to 200 feet upgradient of the creek, the very flat gradient
created by the interception trench will not remove surface water from the creek or groundwater
entering the Holbrook Tributary from the south bank. Figure 5-4 shows the April 2005
groundwater elevations along the path of the trench. Also shown are the proposed pumping
elevations and the elevation of the creek at the downgradient end of the trench. The level of the
pump can be adjusted to collect .contaminated groundwater without impacting water levels in the
creek.
Based on conservative flow modeling, the total groundwater discharge to Holbrook Tributary
(from both sides of the creek) over this 2,000-foot stretch is 10 to 20 gpm. Each ''/Z-HP sump
pump will be capable of pumping from 5 to 15 gpm. The Al and A2 segments will be pumped
through a :prefilter and two 500-pound carbon canisters before discharging to Holbrook
Tributary. A duplicate system will treat groundwater from the B 1 and B2 segments. A small
building housing the carbon canisters will be located outside of the school playground. Power is
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present on site at the segment Al and A2 sumps. Power will have to be brought into a small
treatment building located outside the school fence near segments B1 and B2. The two sump
covers and two 6-inch cleanouts will be flush mounted and will be the only visible parts of the
trench system. Site restoration at segments Al and A2 will include asphalt repairs while
segments B 1 and B2 will require regrading, replacement of topsoil, and reseeding.
There are three important construction issues related to the interceptor trenches. First, the
construction areas are near the school and neighborhoods and work must proceed quickly and
fencing and warning signs must be in place to limit access to the work zone. The drain
construction around the playground perimeter must take place when school is not in session.
Second, excess trench spoils must be removed from the site at the end of each day.
Approximately 200 cubic yards (10 tandem truck loads) of soil will be hauled from the site each
day over a 14-day period. The first trench spoils pile will be sampled and 24-hour sample
turnaround requested to confirm the non -hazardous nature of the soil. This sample can also be
used to determine if spoils can be hauled to the Ft Bragg borrow area as general fill or if it needs
to be taken to a RCRA D landfill as non -hazardous material. Third, the construction must
minimize environmental damage and not impact the Army mission or personnel. Trench
conceptual design has avoided the sensitive habitats near the stream and the selected trench
locations will minimize inconvenience to installation residents.
The interceptor trench and treatment system will operate until groundwater concentrations are
sufficiently low that surface water will no longer be adversely impacted. Pump -and -treat
operations are expected to be conducted for a period of 25 years.
MNA of Remaining Groundwater Contamination. In addition to active bioremediation in
the source area, NINA will be employed similar to that described above for Alternative 2. The
calibrated numerical model discussed in Section 3.11.2 predicted 60 years for NINA alone to
reach North Carolina 2L standard (0.17 µg/L) and 33 years to reach the surface water remedial
level (4 µg/L). These predictions may be optimistic since (1) the model uses a potentially
conservative but unvalidated decay rate, and (2) contaminant flux from the Cape Fear clay was
not incorporated as source term for the model. However, a 90-percent source reduction in
contaminant mass through enhanced bioremediation would eventually produce much lower VOC
concentrations beneath Holbrook school and in surface water. Based on groundwater velocities
of 100 feet per year at the site, the time for groundwater emanating from the source area to reach
Holbrook Tributary behind the school (-1,000 feet) is 2 to 5 years. Although 1,1,2,2-
tetrachloroethane will move slower than advective groundwater flow due to the effects of
retardation, it is probable that the impact of source treatment and MNA will begin to reduce
groundwater concentrations entering the interceptor trenches within 10 years. It will take
considerably longer for the groundwater concentrations to reduce to the point that surface water
will meet clean up standards without the operation of the interceptor trench and treatment
system.
Institutional Controls. Institutional controls' and soil gas, groundwater, and surface water
monitoring would be similar to Alternative 2 and would include land- and groundwater -use
restrictions at SWMU 103. However, institutional controls, fencing, warning signs and
aeration/volatilization treatment systems for surface water would not be necessary. Restrictions
on groundwater use for consumption and irrigation would be implemented for the life of this
remedial alternative, which is estimated to be 60 years.
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Groundwater Monitoring Network. One new monitoring well (MW51) would be installed
to complete the groundwater monitoring network to evaluate the performance of the remedy. The
location of the new monitoring well is along Sharpe Drive between MW-29 and MW-31, as
presented on Figure 5-3. The initial groundwater monitoring network will consist of 31 wells.
The monitoring well network will be evaluated annually for optimization opportunities. Some
shallow wells can be eliminated from the existing network since contamination is primarily in
the deeper wells.
Performance Groundwater Sampling. The performance sampling for. source treatment and
MNA will be the same as described under Alternative 2. Groundwater monitoring, including
measurement of groundwater elevations, from the same network of wells will be used to evaluate
the performance of the interceptor trenches. Influent and effluent sampling and analysis for
VOCs would be conducted to evaluate performance of the carbon treatment systems.
Soil Gas Monitoring. Annual soil gas monitoring would be similar to Alternative 2.
Surface Water .Sampling. Annual surface water samples would be collected similar to
Alternative 2 until it was demonstrated that the interceptor trenches were protecting the surface
waters. Surface water samples would be collected again once the interceptor trenches were shut
down.
Confirmatory Groundwater Sampling. Confirmatory groundwater sampling would be the
same as Alternative 2.
Reporting. Reporting would be the same as described in Alternative 2.
Protection of Human Health and the Environment
The primary difference between Alternatives 3 and 2 is the installation of interceptor trenches
to more actively prevent surface water contamination. Therefore, the differences in degree of
protection of human health and the environment between Alternatives 3 and 2 are due only to
this portion of the designs and are discussed below.
Capturing and treating contaminated groundwater prior to its discharge to Holbrook tributary
and Beaver Creek would eliminate the potential risks to human health and the environment posed
by exposure to contaminated surface water. Given. the proximity of the Holbrook tributary to
Holbrook Elementary School, residential areas, and open recreation areas, this represents a
significant increase from Alternative 2 in the protection of human health. The Holbrook tributary
does not have significant ecological habitat; however, elimination of contaminants in "a potential
drinking water source for fauna present along this stretch would increase the protectiveness to
ecological receptors.
Source treatment using enhanced bioremediation followed by natural attenuation and
collection and treatment of contaminated groundwater prior to discharge to surface water uses a
combination of active and passive treatment to be protective of human health and the
environment. Active treatment would degrade contaminants in the source area groundwater,
facilitating more rapid improvement of downgradient groundwater quality. Eliminating surface
water contamination would eliminate the need for institutional controls and
aeration/volatilization treatment for surface water. Similarly with Alternative 2, treatment of the
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source area will reduce the mass of contaminants migrating toward surface water; therefore, the
alternative would have long-term effectiveness.
There would be little disturbance of soil or groundwater associated with the source area
treatment that might result in an impact to human health or the environment because the active
portion of the alternative is an in -situ process. The installation of the interceptor trenches would
be performed during the summer months when Holbrook Elementary School is not in session,
reducing the chance for exposure to contaminated soils that are excavated. Temporary fencing
would be installed around the active construction portion of the installation of the trenches to
prevent trespassing.
Because the MNA portion of Alternative -3 is the same. as Alternative 2, the same level of
protection of human health and the environment would be achieved and maintained through
institutional controls. The exposure to contaminated surface water would be eliminated.
Land- and groundwater -use restrictions would be the same as for Alternative 2 during the
natural attenuation period. Therefore, the overall protection of human health and the environment
during the natural attenuation period of this alternative is dependent on the establishment and
maintenance of institutional controls. Institutional controls would be instituted and maintained by
Fort Bragg through the BMP. The SWMU 103 area is expected to remain under the ownership of
the federal government; therefore, the long-term effectiveness of institutional controls is
assumed.
Monitoring of the soil gas, groundwater, and surface water would confirm the performance of
the remedial alternative and ensure that contamination is not migrating or increasing in
concentration to an unacceptable degree.
Attain Media Cleanup Standards
Alternative 3 would comply with surface water cleanup levels through the active interception
and treatment of contaminated groundwater prior to its discharge to surface water. Surface water
would meet clean up criteria in a few months. Modeling indicates that at least 25 years of pump -
and -treat will be necessary before the source area treatment and natural attenuation processes
reduce groundwater contaminants to concentrations below the North Carolina surface water
criterion, at which time pump -and -treat operations could be discontinued. Groundwater would
attain the North Carolina 2L or IMAC standards, but not in a short timeframe. Contaminant
concentration's in groundwater would remain above North Carolina 2L standards until complete
restoration of the aquifer had been achieved, which will likely take decades.
Institutional controls (i.e., groundwater -use restrictions) implemented under this alternative
would prevent the potential ingestion of contaminated drinking water, and long-term monitoring
would demonstrate when the aquifer was restored to North Carolina 2L standards.
Control of Source of Releases
►Q
Alternative 3 would control releases from the source areas as described above for Alternative
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Releases of contaminated groundwater to surface water would be eliminated. The interceptor
trenches and treatment systems will- collect and treat contaminated groundwater prior to its
discharge to surface water.
Comply with Applicable Standards for Management of Waste
Alternative 3 will comply with state and federal requirements. An UIC Program' Permit will
be required prior to the injection of any substance into the subsurface. All of the representative
injectants evaluated in the conceptual, design for enhanced bioremediation are approved
substances for injection by the State of North Carolina. Alternative 3 may require a National
Pollutant Discharge Elimination System (NPDES) permit and associated monitoring to discharge
treated groundwater to Holbrook Tributary.
IDW generated during the installation of injection wells and groundwater monitoring wells
will be characterized to determine waste characteristics. Waste will be disposed of in accordance
with all state and federal regulations.
Other Factors
Long -Term Reliability and Effectiveness. Similarly to Alternative 2, Alternative 3 achieves
long-term reliability and effectiveness through a combination of active and passive .treatment
technologies. The active treatment in the source area would biologically degrade contamination
in groundwater in the source area. The treatment of contamination in the source area will reduce
the contaminant flux from the Cape Fear Formation clay to the aquifer and eventually reduce the
( flux of contamination from groundwater to surface water under non -pumping. conditions.
Intercepting and treating contaminated groundwater prior to its discharge. to surface water
provides long-term reliability and effectiveness in eliminating potential exposure to surface
water. It also eliminates the need for institutional controls to limit potential exposure to surface
water contaminants.
The reliability of enhanced bioremediation and MNA are the same as Alternative 2.
Institutional controls would be established to prevent exposure to contaminated groundwater.
Reduction in the Toxicity, Mobility, or Volume of Wastes. -Similar to Alternative 2,
Alternative 3_ uses active treatment to reduce the toxicity of the groundwater in the source area.
Alternative 3 also uses active treatment to reduce the toxicity of. groundwater discharging to
surface water.
Alternative 3 does meet the statutory preference for employing treatment technologies that
permanently reduce the toxicity, ' mobility, or volume of the contaminants. Alternative 3 uses
active treatment to reduce the toxicity in groundwater in the -source area and in groundwater
discharging to surface water.
In addition to treatment of the source area and treatment of groundwater extracted from the
interceptor trenches, natural attenuation processes will passively treat the remaining
contaminants in groundwater.
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Groundwater monitoring would be used to confirm the continued decrease in toxicity of
groundwater as a result of engineered remediation and natural attenuation. Surface water
sampling would be used to confirm that active. treatment using the interceptor trench and
activated carbon treatment was reducing the toxicity of groundwater entering surface water.
Short -Term Effectiveness. Short-term impacts for Alternative 3 would be similar to
Alternative 2 for the injection and MNA portions of this alternative because they are essentially
the same. There would be increased short-term impacts from installing the interceptor trenches.
These impacts could be somewhat mitigated by removing excavated material daily, and by
constructing the interceptor trenches when school was not in session. The remedy would not
have to rely on institutional controls to prevent exposure to contaminated surface water upstream
of the aeration/volatilization systems employed in Alternative 2.
The total time to implement Alternative 3 is the same as Alternative 2, approximately 60
years.
Implementability. Alternative 3 is implementable. Materials, equipment, and labor for
installation of injection wells, monitoring wells, injection of additives to promote anaerobic
reductive dechlorination, and sampling (soil gas, groundwater, and surface water) are available
as described under Alternative 2. However, from an implementability standpoint this alternative
is the most complex and challenging of the three alternatives evaluated due to the addition of
groundwater pumping, treatment, and discharge. Utility clearances would have to be obtained
along the full length of the trenches, and substantial amounts of soil .IDW would be generated
that require sampling, analysis, and disposal. Large volumes of clean backfill material would
have to be imported and placed, electrical hookups to pumps would have to be established, and
normal activities would be disrupted to a greater extent over.a larger area. The treatment system
would have to be purchased and constructed; and water transmission pipelines from the trenches
to the treatment systems -and then to the discharge locations would have to be constructed and
buried. A NPDES permit would have to be obtained to permit discharge of treated water into the
existing surface water drainages. Site restoration/demobilization activities would be more
extensive and resource -intensive.
Installation of the interceptor trenches would employ readily available technology. Similar
35-foot-deep trenches have been successfully installed at other locations, some up to a mile in
length. The trenching machine is fitted with special attachments to install the 6-inch perforated
piping and sumps. Groundwater treatment using activated carbon is a conventional, reliable, and
cost-effective treatment technology.
Establishment of groundwater institutional controls for Alternative 3 would be similar to
Alternative 2. Surface water institutional controls would not be necessary.
Cost. The capital cost for installing injection wells and monitoring wells, purchasing substrate
for injection, performance of baseline sampling, and installing the interceptor trenches and
treatment systems would be approximately $1,259,950. The O&M costs were estimated at
approximately $2,524,150 for a 60-year period. For estimating purposes, O&M costs include 25
years of operation of the interceptor trench and treatment systems. The total cost for Alternative
3 would be approximately $3,784,100. Detailed costs for this alternative are presented in Table
5-3.
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SECTION 6
COMPARATIVE ANALYSIS OF ALTERNATIVES, CONCEPTUAL
DESIGN, AND IMPLEMENTATION PLAN
This chapter presents a conceptual design and plan for implementation of the selected
corrective action alternative. A cost-effective corrective action has been selected that will
adequately protect human health and the environment from groundwater and surface water
contamination.
6.1 COMPARATIVE ANALYSIS OF CORRECTIVE ACTIONS
A screening of remedial process options and technologies applicable for chlorinated solvents
in groundwater and surface water against site -specific conditions was performed in Sections 5.2
and 5.3, respectively, to identify applicable process options/technologies that would be effective
and implementable at SWMU 103. The process options passing the screening were combined to
form three site -wide corrective action alternatives for detailed description and analysis (Section
- 5.4). The three corrective action alternatives selected provided a range of remedial options from
r+ primarily passive treatment technologies (Alternative 1: MNA and engineered
aeration/volatilization of surface water), to a more active treatment alternative (Alternative 3:
enhanced bioremediation in the source zone and interception/treatment of contaminated
groundwater prior to its discharge to surface water), and one intermediate alternative. Section 5.4
presented an analysis of the alternatives against RCRA evaluation criteria, as summarized in
Table 5-4. All of the alternatives satisfy the RCRA criteria; however, the degree to which each
site -wide alternative satisfies the RCRA criteria, and their estimated costs, are distinguishing
factors. This section presents a comparative analysis of the alternatives against RCRA criteria,
which allows for the selection of the alternative that best balances reduction of contaminant mass
and associated risks to human health and the environment, and costs. It should be noted that the
final alternative developed for SWMU 103 may be revised by the risk managers as additional
site -specific information becomes available by either selecting a different combination of process
options or by evaluating an additional process option that has been screened out.
The following bullets summarize key aspects of SWMU 103 that were considered during the
comparative analysis of alternatives and in the selection of the recommended alternative:
Low-level groundwater plume consisting primarily of chlorinated solvents that
encompasses approximately 92 acres. The primary COC is a chlorinated alkane, 1,1,2,2-
tetrachloroethane. The maximum concentrations of this compound detected at the former,
Mallonee Village Gas Station as of April 2005 ranged from 410 to 570 µg/L. The higher
concentrations of chlorinated compounds are located in the deep surficial groundwater just
above the clay -confining layer that is below the site.
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r__
• The groundwater plume has migrated below Holbrook Elementary School. Monitoring k� 1
indicates that VOCs are not migrating from groundwater by the vapor pathway into the
school.
The source area is considered to be the former Mallonee Village Gas Station site because
this is the location of the maximum groundwater concentrations; however, no
"characteristic source area" containing high concentrations of soil and groundwater
contamination has been identified at SWMU 103. The source theory that is most
consistent with the historical record and current distribution of contaminants is that
chlorinated VOC contaminants traveled vertically downward, possibly as DNAPL, and
some remains in deeper groundwater in a clay "trough" that prevents migration with
groundwater flow to the south. Some contaminants have likely diffused into the Cape
Fear clay layer underneath the former gas station; VOCs are hypothesized to now be
diffusing back out of that clay layer into the surficial aquifer.
• Given the low concentrations of contaminants in groundwater across the approximate 92-
acre area and the lack of a well-defined source area, the contaminant mass, as represented
by 1,1,2,2-tetrachloroethane, is spread throughout the plume. The mass of contaminant in
the groundwater and mass reductions necessary to achieve various target levels for
protection of human health and the environment were presented in Section 3.11.2.
• Concentrations of 1,1,2,2-tetrachloroethane in groundwater are migrating to surface water
in the Holbrook tributary at concentrations above the North Carolina surface water
standard. Surface water in Beaver Creek is below the North Carolina surface water
standard except where the Holbrook tributary discharges into it. 1,1,2,2-
Tetrachloroethane migration in surface water appears to be attenuated by volatilization. 1
• The contaminant concentrations in groundwater are decreasing with time, and natural
attenuation appears to be occurring, primarily by abiotic processes.
• The subsurface groundwater conditions at S WMU 103 are highly aerobic, as indicated by
high DO concentrations measured during groundwater sampling.
• 1,1,2,2-Tetrachloroethane continues to be measured in the groundwater at the background
well (MW27) at a concentration of approximately 5 µg/L.
6.1.1 Protection of Human Health and the Environment
All three alternatives would be effective at protecting human health and the environment over
the short- and long term through a combination of passive or active measures. Because all of the
alternatives are effective at protecting human health, an evaluation of the estimated time required
to reach remedial levels that are protective of human health is the driver in the evaluation.
The timeframe for meeting remedial levels in groundwater that are protective of human health
are essentially the same for all alternatives due to the widespread, diffuse nature of the plume
and the reliance, in whole or in part, on natural attenuation processes. The primary difference
between the alternatives is the timeframe and extent to which the alternatives are protective of
human health and the environment in surface water. Alternative 1 relies in part on institutional
controls for at least 33 years to be protective of surface water, Alternative 2 relies in part on
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r institutional controls for at least 25 years to be protective, and Alternative 3 is protective almost
immediately without any reliance on institutional controls.
6.1.2 Attainment of Media Cleanup Standards
All of the alternatives would eventually attain the media cleanup standards of 0.17 µg/L for
groundwater and 4 µg/L for surface water. AllAhree alternatives rely in wholly or in part on
natural attenuation processes to meet groundwater cleanup standards. Because of the widespread
and diffuse nature of the plume, the fate and transport modeling performed by
SAIC indicated that there would be no significant difference between the alternatives in the
timeframe to meet groundwater cleanup standards.
Alternative 3 achieve media cleanup standards in surface water relatively quickly along the
entire contaminated reaches of Holbrook Tributary and Beaver Creek through active treatment of
the groundwater prior to discharge to surface water. Alternatives 1 and 2 attain media cleanup
standards in surface water at a downstream location through aeration/volatilization, and control
exposure to upstream, contaminated portions of the streams using institutional controls. It is
estimated that these upstream portions of the streams will remain above media cleanup standards
for at least 33 years for Alternative 1, and at least 25 years for Alternative 2.
1
6.1.3 Control,of Source of Releases
The location of the source of the contamination that caused the low-level dissolved plume is
the former Mallonee Village Gas Station. The current site conceptual model is that chlorinated
VOCs are in deeper groundwater where flow is controlled by contours (a trough) in the lower
1, f Cape Fear clay layer. VOCs are probably diffusing from the Cape Fear clay layer under the
former gas station. However, no elevated concentrations representing a significant, continuing
source were discovered during the RFI. Indications are that contaminant concentrations in
groundwater are decreasing with time across the plume. A low-level, diffuse, dissolved -phase
plume encompasses 92 acres.
Alternatives 2 and 3 incorporate active treatment (enhanced bioremediation) to treat the
source of the dissolved plume, with the ultimate goal of reducing contaminant mass in
groundwater and contaminant flux to surface water. Alternative 3 provides additional treatment
for contaminated groundwater prior to its discharge to surface water.
6.1.4 Comply with Applicable Standards for Management of Waste
All of the alternatives will comply with applicable standards of management of waste during
their implementation and performance. None of the alternatives, including the active treatment
portions of the alternatives, would generate IDW other than soil and groundwater. During the
RFI activities, no soil or groundwater IDW was identified as hazardous; therefore, no hazardous
waste is anticipated to be generated during the implementation of any of the site -wide
alternatives.
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6.1.5 Other Factors -
6.1.5.1 Long-term reliability and effectiveness
The long-term reliability and effectiveness of all three alternatives is dependent upon
maintaining institutional controls and O&M activities (primarily monitoring) at the site over the
relatively long periods required for MNA to reduce contaminant concentrations to below cleanup
goals. Because the site is a government military installation with no change in ownership
expected over the period of the implementation of the alternatives, there is a high degree of
confidence in the long-term reliability and effectiveness of the three alternatives. With MNA for
groundwater as a part of the remedial action for Alternatives 1, 2, and 3, the anticipated O&M
scopes for groundwater are similar. However, the O&M associated with ensuring the long-term
reliability and effectiveness of the protection of the surface water differs. Alternatives 1 and 2
use aeration/volatilization in the affected surface water reaches of the Holbrook tributary and
Beaver Creek, while Alternative 3 requires collection and treatment of contaminated
groundwater prior to its discharge to surface water, which is a considerably more complex and
O&M -intensive effort to address surface water contamination. The aeration/volatilization and
institutional controls of Alternatives 1 and 2 are judged to have higher long-term reliability and
effectiveness than the interceptor trenches and above -ground treatment approach outlined in
Alternative 3 (due to the complexity of the Alternative 3 approach and therefore its higher
possibility of failure). Between Alternatives 1 and 2, Alternative 2 is determined to have higher
long-term reliability and effectiveness due to the addition of source area treatment to reduce the
contaminant mass migrating toward surface water.
6.1.5.2 Reduction in the toxicity, mobility, or volume of wastes '
Alternatives 2 and 3 use a combination of active and passive remediation approaches to
reduce the toxicity of groundwater, while Alternative 1 uses only passive remediation (i.e.,
MNA). Specifically, Alternatives 2 and 3 use enhanced in situ bioremediation to reduce the
toxicity in the source area, which was defined as the former Mallonee Village Gas Station.
Alternative 1 has the least rapid reduction in toxicity because it uses passive treatment (i.e.,
natural attenuation) to reduce the toxicity of groundwater. Site conditions at SWMU 103 are not
conducive to natural anaerobic biodegradation, therefore MNA will rely primarily on abiotic
processes. The interceptor trenches and ex situ treatment associated with Alternative 3 further
reduce the toxicity of groundwater discharging to surface water.
6.1.5.3 Short-term effectiveness
The short-term effectiveness is high for all of the alternatives but varies with the level of
implementation required for the individual alternative. Alternative 1 is the most effective in the
short-term because it only involves installing fencing, signs, and an engineered
aeration/volatilization system in for surface water. There is essentially no environmental or
community impact from Alternative 1.
Alternative 3 is the least effective in the short-term because of the construction associated
with installing the interceptor trenches. The trenching will involve use of heavy machinery as
well as the transportation and disposal of excavated material. Careful planning and logistics will
minimize the potential for community and environmental impact.
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The source treatment using enhanced bioremediation for Alternatives 2 and 3 will have
minimal environmental and community impact. All amendments scoped for injection have been
approved for remediation use in North Carolina. The above -ground impacts will have a limited
footprint and then only for a short time. Direct -push technology will be used for the injection
points, which will not produce any IDW.
6.1.5.4 Implementability
All three alternatives are technically implementable; however, there are significant differences
in the degree of implementability. For Alternative 1, MNA and engineered aeration/volatilization
of surface water, a monitoring well network already exists and will only need to be supplemented
with one additional groundwater monitoring well. Monitoring of site media (i.e., soil gas, surface
water, and groundwater) was performed during the RFI for SWMU 103 without any
implementation issues arising. Installation of an engineered aeration system in surface water is
easily implementable. Alternative 1 will be the easiest alternative to implement and will cause
the least disruption to the residential area and Holbrook Elementary School.
The source treatment associated with Alternatives 2 and 3 adds a layer of complexity to
Alternative 1 as described in Section 5.4, but is also readily implementable. Enhanced
bioremediation using�carbon substrate has been implemented successfully at contaminated sites
across the nation.
The construction of interceptor trenches and operation of the pump -and -treat system to
minimize migration of groundwater contamination to surface water is implementable using
currently available trenching technology and conventional groundwater pump and treat
approaches. However, from an implementability standpoint, this is the most complex and
challenging task being considered as described in Section 5.4.2.3. The trench::instaflation would
be performed during the summer when Holbrook Elementary School is out of session to
minimize potential impact to students and school operations.
6.1.5.5 Costs
The approximate total nondiscounted costs for the alternatives are summarized in Table 5-3.
Alternative 1, MNA and natural or engineered aeration/volatilization of surface water, is the least
expensive alternative. The capital and O&M costs for Alternative 1 are $ 0.7 million (M) and
$2.6 M, respectively, for a total cost of $3.3 M.
Alternative 2, source treatment, MNA, and natural or engineered aeration/volatilization of
surface water, is the second most costly alternative. The capital and O&M costs for Alternative 2
are $1.0 M and $2.5 M, respectively, for a total cost of $3.5 M.
Alternative 3, source treatment, MNA, and collection and treatment of contaminated
groundwater prior to its discharge to surface water, is the most costly alternative. The capital and
O&M costs for Alternative 3 are $1.3 M and $2.5 M, respectively, for a total cost of $3.8 M.
6.1.4 Selected Alternative
All three alternatives are effective at protecting human health and the environment over the
short and long terms through a combination of passive or active measures. Alternatives 2 and 3
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are superior to Alternative 1 in that they provide enhanced control of the source of releases, a
greater reduction in toxicity, mobility and volume of waste, and satisfy a statutory preference for
active treatment. The enhanced bioremediation in the source area also reduces the uncertainty
inherent in a purely MNA approach at a site where existing conditions are not conducive to
natural biodegradation.
Alternative 3 provides additional control of contaminant migration in groundwater relative to
Alternative 2, but at additional cost, decreased short-term effectiveness, and possibly decreased
long-term effectiveness and implementability due to considerably more complex O&M
requirements. Given that surface water is not used for human consumption or contact, provides
limited if any ecologically significant habitat, and contaminant migration in surface water can be
controlled through engineered aeration/volatilization, Alternative 3 provides only marginal
benefits relative to Alternative 2. Therefore, Alternative 2, source treatment, MNA, and
engineered aeration/volatilization of surface water, offers the best balance in terms of RCRA
evaluation criteria and cost. The alternative is protective of human health and the environment
and is both readily implementable and cost-effective.
6.2 CONCEPTUAL DESIGN OF SELECTED ALTERNATIVE
During the period of DoD's ownership, administrative controls and groundwater -use
restrictions will be recorded in the BMP to ensure implementation. To reduce potential exposure
to contaminated surface water at SWMU 103, warning signs will be installed along the impacted
length of Beaver Creek and the Holbrook tributary.
6.2.1 Establishment of Institutional Controls
Administrative controls and groundwater -use restrictions for SWMU 103 will be incorporated
into the BMP. Administrative restrictions would involve the installation of signs along Beaver
Creek and the Holbrook tributary. Groundwater -use restrictions would be implemented through
the BMP. Currently, SWMU 103 is part of a federal installation and is expected to be retained by
the federal government for the indefinite future. Groundwater -use restrictions would be
implemented to prevent the use of the groundwater for potable water and irrigation. References
to relevant corrective action documents for this SWMU will also be included in the BMP.
Appropriate implementing documents will detail the administrative controls and groundwater use
restrictions.
6.2.2 Engineered Aeration/Volatilization for Surface Water
Surface water will be treated using aeration/volatilization within the footprint of the
groundwater plume to meet the North Carolina surface water standard (4 µg/L of 1,1,2,2-
tetrachloroethane). The most downstream extent of the groundwater plume (currently
understood to be where Beaver Creek flows under Knox Street) would be the point -of -
compliance to meet surface water standards. The engineered aeration/volatilization systems
would be implemented using the step -wise approach outlined in Section 5.3.4.1. The step -wise
process would begin with a simple passive aeration system (roughening the streambed with small
boulders) and proceed to more complex aeration solutions until monitoring shows that the
installed aeration/volatilization system is effective at meeting surface water standards at the
point -of -compliance.
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6.2.3 Warning Signs and Fencing
Fencing presently exists along the Holbrook tributary behind Holbrook Elementary School
between San Lucas Drive and Sharp Drive. Existing fencing will be repaired as necessary and
new fencing will be installed to prevent contact with the surface water along Holbrook tributary
where 1,1,2,2-tetrachloroethane concentrations exceed the surface water standard of 4 µg/L. The
new fencing will be 6-foot vinyl -coated chain -link to match the existing fencing. Permanent
warning signs will be installed along the fenced -areas of the Holbrook tributary. The warning
signs will be used to deny access and discourage contact with surface water. Specifics of sign
construction, content, and maintenance will be detailed in the implementing documents.
6.2.4 Complete Groundwater Network
One new monitoring well (MW51) will be installed to complete the groundwater monitoring
network to evaluate the performance of natural attenuation. The location of the new monitoring
well is along Sharpe Drive between MW-29 and MW-31, as presented on Figure 5-2. The initial
groundwater monitoring network will consist of 31 wells. The monitoring well network will be
evaluated annually for optimization opportunities. Some shallow wells can be eliminated from
the existing network since contamination is primarily in the deeper wells.
6.2.5 Enhanced Bioremediation in the Source Area
The purpose of applying enhanced anaerobic bioremediation technology to the SWMU-103
source area is to reduce contaminant mass present in the subsurface and thereby reduce long-
term contaminant mass loading to the Holbrook tributary and Beaver Creek. The mixed
substrate for this application will consist of a soluble substrate such as high fructose corn syrup
to provide an immediate mass of bioavailable organic carbon to drive,;geochemistry into
anaerobic conditions, and food -grade vegetable oil to provide a slow release source of organic
carbon to drive reductive dechlorination over the long term. This mixture typically supports
anaerobic biodegradation for 2 to 3 years. Organic substrate will be targeted for the lower 15
feet of the Middendorf aquifer where VOC concentrations are highest. Organic substrate will
also absorb into the top of the confining clay unit (believed to be the primary source of
continuing contamination) and enhance biodegradation of 1,1,2,2-tetrachloroethane and TCE
diffusing out of the clay. A pH amendment product such as sodium bicarbonate will also be
added to maintain neutral pH conditions within each reaction area. Degradation products (cis
1,2-DCE and vinyl chloride) are more rapidly degraded in neutral pH conditions, making pH
buffering an important factor in successful enhanced bioremediation applications.
The injection well network in the source area will consist of 42 direct push injection points
installed in a grid orientation. The spacing between the injection points will be approximately 10
feet to ensure adequate substrate distribution. Each of the injection points will be advanced to
the top of the Cape Fear Formation Clay so that the substrate is injected in the bottom portion of
the Middendorf Formation. Half of the injection points will be completed as temporary small
diameter wells to allow for future injections of amendments and additional organic substrate if
necessary. During the initial injection approximately 800 to 1,000 gallons of organic substrate
mixture and pH amendment will be injected at each point. Based on the radial flow in the deep
groundwater, this design will produce anaerobic conditions in at least a 10,000-square foot area
beneath the former solvent UST area (Figure 5-2).
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After the first six months of performance monitoring, the geochemical data and progress of
1,1,2,2-tetrachloroethane and TCE degradation in the source area will be reviewed. If
degradation is lagging and conditions are sufficiently anaerobic, a supplemental volume of
approximately 300 to 500 gallons of dilute bioaugmentation culture and a pH amendment may be
injected into each of the small diameter wells. The bioaugmentation culture will consist of a non-
pathogenic, naturally occurring microbial population of microbial strains known to be capable of
complete dechlorination of 1,1,2,2-tetrachloroethane and its degradation products (cis 1,2-DCE
and vinyl chloride). The bioaugmentation culture will be provided by SIREM Laboratories,
which has developed a bioaugmentation product called WBC-2 that was specifically developed
for the degradation of 1,1,2,2-tetrachloroethane in conjunction with the U.S. Geological Survey.
WBC-2 has been field tested at Aberdeen Proving Grounds for the Army and has been shown to
be very effective at completely degrading 1,1,2,2-tetrachloroethane. The goal of the organic
substrate injection is to achieve a 90-percent average 1,1,2,2-tetrachloroethane reduction within
the source area. A second injection of organic substrate may be applied to the SMWU-103
source area in the event that concentrations of 1,1,2,2-tetrachloroethane rebound above 100 µg/L
within the source area within 3 years of the initial injection.
6.2.6 Monitored Natural Attenuation
MNA will require the monitoring of contaminant levels to ensure that the mass of
contamination in the groundwater is reducing with time. Institutional controls and soil gas,
groundwater, and surface water monitoring will be used to ensure the protection of human health
and the environment over the long implementation time required to meet remedial goals.
The results of natural attenuation modeling performed as part of this CMS are summarized in
Appendix K. Modeling estimated that it would require approximately 60 years from CY 2005 to ?
reduce the concentration of 1,1,2,2-tetrachloroethane to less than the remedial level of 0.17 µg/L -"
if no source treatment is attempted. Even with source treatment, it will take decades to meet
North Carolina 2L standards throughout the widespread plume at SWMU 103.
.Periodic groundwater sampling (Section 6.2.7.2) will be performed to track the progress of
natural attenuation. Performance groundwater sampling will be performed on an annual basis at
31 wells to monitor the progress of the natural attenuation. If groundwater monitoring indicates a
reduction in contaminant concentrations, then the groundwater sampling will be optimized,
including a reduction in sampling frequency. Confirmatory sampling will be performed two
years after the last MNA performance sampling.
6.2.7 Monitoring
6.2.7.1 Soil gas
Soil gas monitoring will be conducted around Holbrook Elementary School. The purpose of
the soil gas monitoring would be to ensure that VOCs do not impact human health through vapor
intrusion at the school in the future. Since only a single round of sampling has occurred from the
18 soil gas sampling points, an additional year of monitoring from the entire network will be
conducted. If results confirm that VOCs in groundwater are not migrating by a vapor pathway
into the buildings, and if groundwater concentrations do not increase, soil gas monitoring would
be optimized. Optimized soil gas sampling would still be conducted annually, but would be
limited to three existing upgradient monitoring points (SG1, SG14, and SG 16). Soil gas samples
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will be collected in 6-L subatmospheric SUMMA canisters supplied by the analytical laboratory.
Soil vapor samples will be collected in accordance with EPA Method TO-15 and analyzed for
VOCs. Soil gas samples will be collected annually prior to the beginning of the school year. The
results of the soil gas sampling will be evaluated relative to EPA vapor intrusion screening
criteria to ensure that Holbrook Elementary School remains safe from vapor intrusion.
6.2.7.2 Groundwater
Performance Groundwater Sampling. Groundwater will be sampled quarterly during the
first year following carbon substrate injection to evaluate performance of anaerobic reductive
dechlorination. Thereafter, performance monitoring will be conducted annually. Groundwater
from wells in the vicinity of the carbon substrate injection will be sampled and analyzed for
VOCs, TOC, geochemical parameters and pH. Results of the groundwater sampling will be used
to evaluate the effectiveness of anaerobic reductive dechlorination and develop plans for
subsequent bioaugmentation and carbon substrate injection as necessary.
Performance groundwater monitoring for MNA will be performed on an annual basis to
evaluate the progress of the natural attenuation. The location and sampling frequency of wells for
performance sampling will be selected based on evaluation of the results of the previous year's
performance sampling. Over the first 10 years, it is anticipated that some of the interior wells
may be moved to .a biennial sampling frequency. However, wells near the Holbrook Elementary
School and residential areas would remain on an annual sampling frequency. Groundwater will
be analyzed for VOCs and natural attenuation parameters.
Confirmatory Sampling. Confirmatory groundwater sampling will be conducted for two
� years after the completion of the natural attenuation period to ensure that the groundwater
contamination does not rebound.
41
6.2.7.3 Surface water
Effectiveness monitoring will be required during the period that engineered
aeration/volatilization system(s) are implemented to establish whether the technologies in place
are achieving the necessary contaminant reduction. The effectiveness monitoring will include
sampling above and below treatment zones, conducted on a frequent basis to provide sufficient
data on which to make that determination. Once the successful technology for remediation of the
surface waters is selected, as established through the effectiveness monitoring, a reduced
monitoring schedule can be established. Surface water would bd analyzed for VOCs.
6.2.8 Investigation -Derived Waste
IDW will be generated from the installation of the new monitoring well. The IDW will consist
of soil cuttings and wastewater (i.e., development water and decontamination water), and will be
characterized for VOCs and SVOCs for determining disposal requirements. Historical
knowledge of the waste characteristics of SWMU 103 indicates that other contaminants (e.g.,
metals, pesticides, etc.) are not a concern. It was assumed that the soil and groundwater IDW will
be characterized as non -hazardous based on similar historical waste determinations. Wastewater
will also be generated during groundwater sampling events, and will be characterized and
disposed of as appropriate.
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6.2.9 Operation and Maintenance
The O&M and reporting requirements will be outlined in the Corrective Measures
Implementation Plan developed under the remedial design for the implementation of the
corrective action. The O&M requirements include site inspection, maintenance of the engineered
aeration/volatilization system, monitoring/injection well replacement/reconditioning, soil gas
monitoring, groundwater monitoring, and surface water monitoring.
6.2.10 Reporting
6.2.10.1 Periodic Progress Reports
An annual report will be issued to present the results of the annual sampling events. If the
monitoring frequency is reduced, the frequency of progress reporting will be reduced as well to
coincide with monitoring events.
6.2.10.2 Corrective Action Completion Report
A Corrective Action Completion Report will be issued at the completion of the confirmatory
sampling.
6.2.11 Monitoring Well and Soil Gas Monitoring Point Abandonment
Upon concurrence from NCDENR that the corrective action is complete, the monitoring wells
and soil gas monitoring points will be abandoned. Abandonment will consist of removing the' ;-- -
surface completions and grouting the monitoring well/point to ground surface. .
6.3 COST ESTIMATE
1
The cost estimate for implementation of Alternative 2 at SWMU 103 is provided in Table 5-3.
The estimated 60-year cost is $3,485,150. This consists of capital costs of $961,000 and O&M
costs of $2,524,150.
6.4 EVIPLEMENTATION SCHEDULE
Implementation of the corrective actions will begin once approval of this CMS has been
received from NCDENR. Enhanced bioremediation injections, engineered aeration system for
Holbrook Tributary (if necessary) and fencing will be conducted as soon as all appropriate plans
are developed. A detailed schedule will be developed as part of the O&M Plan developed for the
remedial design for the implementation of the corrective action.
rJ
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SECTION 7
REFERENCES
AFCEE (Air Force Center For Environmental Excellence) 2004. Principles and Practices of
Enhanced Anaerobic Bioremediation of Chlorinated Solvents, August.
Bouwer, H., and R. C. Rice 1976. "A Slug Test for Determining Hydraulic Conductivity of
Unconfined Aquifers with Completely or Partially Penetrating Wells," Water Resources
Research 12(3).
Bouwer, H., and R. C. Rice 1989. "The Bouwer and Rice Slug Test — An Update,"
Groundwater 27(3).
EarthTech 1996. UST Location 6-9650-A, B, C, D Tanks, Fort Bragg, North Carolina, closure
report, Earth Tech Remediation Services.
EPA 1994. Final RCRA Corrective Action Plan, Office of Waste Programs Enforcement, Office
of Solid Waste, May.
EPA 1998. "National Recommended Water QualityCriteria Notice Republication," Federal
Register 63 (237):68354-68364, December 10.
EPA 1999. Compendium of Methods for the Determination of Toxic Organic Compounds in
Ambient Air, Second Edition, Compendium Method TO-15, Determination of Volatile
Organic Compounds (VOCs) In Air Collected in Specially -Prepared Canisters and
Analyzed by Gas Chromatography/Mass Spectrometry (GC/MS), EPA/625/R-96/010b,
Center for Environmental Research Information, Office of Research and Development,
Cincinnati, Ohio.
EPA 2001. Environmental Investigations Standard Operating Procedures and Quality Assurance
Manual, U. S. Environmental Protection Agency, Region 4, Atlanta, Georgia, November.
The web site for the Region 4 Standard Operating Procedures is:
http://www.epa.gov/region4/sesd/eisopqam/eisopqam.html.
EPA 2003. Region 9 Preliminary Remediation Goals, available at
<http://www.epa.gov/region09/waste/sfund/prg/index.htm>.
EPA 2002. OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway
from Groundwater and Soils (Subsurface Vapor Intrusion Guidance). EPA530-D-02-004.
November. Available at <http://www.epa.gov/correctiveaction/eis/vapor.htm>
EPA 2004. EPA Region 9 Preliminary Remediation Goals, last updated October 2004, available
at <http://www.epa.gov/region09/waste/sfund/prg/index.htm>.
1 } 7-1
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Heath, R. C. 1984. "Basic Ground -Water Hydrology," U.S. Geological Survey Water -Supply
Paper 2220. p. 13.
Kearney, Inc., and DPRA, Inc. 1988. Interim Facility Assessment Report, Fort Bragg Military
Reservation.
Mid -Atlantic (Mid -Atlantic Associates, P.A.) 1998. Report of Environmental Services and
Closure of Four Underground Storage Tanks, Fort Bragg, North Carolina, Tank Site No.
16 (6-9650), Contract No. DACA26-C-91-0159, Raleigh, North Carolina. -
NCDENR (North Carolina Department of Environment and Natural Resources) 2002:
Groundwater Quality Standards, 15A NCAC 02L.0202, available at
<http://gw.ehnr.state.ne.us/ADA—Webpage/Adobe/gwStandards.pdf>.
NCDENR 2003. "Redbook" Surface Waters and Wetlands Standards, Division of Water
Quality's Red Rule Book (15A NCAC 0213.0100, "Procedures for Assignment of Water
Quality Standards"; 15A NCAC 02B.0200, "Classification and Water Quality Standards
Applicable to Surface Waters and Wetlands of N.C."; and 15A NCAC 02B.0300,
"Assignment of Stream Classifications"), effective April 1, 2003, available at
<http://h2o.enr.state.ne.us/admin/rules/rbO40103.pdf >.
NOAA (National Oceanic and Atmospheric Administration) 1984-1993. Climatological data,
annual summaries, North Carolina (published annually for 1984-1993, Volume 89-98,
No. 13), Asheville, North Carolina, National Climatic Center.
SAIC (Science Applications International Corporation) 2004a. Site Conceptual Model Report for
the Former Mallonee Village Gas Station and Vicinity that includes SWMUs 4 and 18 and
SWMU 5 at Fort Bragg, North Carolina. '
SAIC 2004b. RCRA Facility Investigation for the Former Mallonee Village Gas Station SWMU
103 at Fort Bragg, North Carolina, September.
SAIC 2006. Addendum No. 7 to the Sampling and Analysis Plan to Support the CMS at the
Mallonee Village Gas Station, Draft, May.
SAIC Engineering (SAIC Engineering of North Carolina, Inc.) 2000a. Field Investigation Report
for the Phase I RCRA Facility Investigation at Mallonee Village Gas Station (SWMU 103)
at Fort Bragg, North Carolina, Oak Ridge, Tennessee, November.
SAIC Engineering 2000b. Trip Report for Records Search for the RCRA Facility Investigation at
Mallonee Village (SWMU 103) at Fort Bragg, North Carolina, Oak Ridge, Tennessee,
September.
SAIC Engineering 2002. Field Investigation Report for the Extended RCRA Facility
Investigation at SWMUs 4 and 18 at Fort Bragg, North Carolina, Oak Ridge, Tennessee,
January.
SAIC Engineering 2005. Addendum No. 6 to the Sampling and Analysis Plan for the Pilot
Studies to Support the Corrective Measures Study for Mallonee Village Gas Station
(SWMU 103) at Fort Bragg, North Carolina.
7-2
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Smith, Brant A., Teel, Amy L., Watts, Richard J. 2004. Mechanism for the destruction of carbon
tetrachloride and chloroform by Modified Fenton's Reagent Department of Civil and
Environmental Engineering, Washington State University, Pullman, Washington,
September.
U. S. Census Bureau. 2000. U.S. Census Bureau State and County QuickFacts, available at
<http://quickfact.census.gov/qfd/states/370".html>.
USGS (U. S. Geological Survey) 1996. RCRA Facility Investigation SWMU 5, Fort Bragg
Installation Restoration Program, Fort Bragg, North Carolina, Volumes I and II, August.
USGS 1998. RCRA Facility Investigation at Solid Waste Management Units 4 and 18, Fort
Bragg Installation Restoration Program, Fort Bragg, North Carolina, Water Resources
Division, Raleigh, North Carolina.
Yin, Yujun and Allen, Herbert E. 1999. Technology Evaluation Report: In Situ Chemical
Treatment, prepared for the Groundwater Remediation Technologies Analysis Center
(GWRTAC), July.
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TABLES
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Table 2-1. Water Levels for April 2005, SWMU 103
Screened
Elevation of
Elevation of
Screened
Interval
Depth to
Top of Casing
Potentiometric
Interval
(ft
Water
Measuring Point
Surface
Well
Well
Date
ft BGS
ANSLL
jtkelow MP
ft AMSL)
(ft AMSL
Cate o
SWMU5
5MWD1
4/15/2005
70.0 to
200.38 to
49.72
272.88
223.16
Deep
80.0
190.38
5MWD2
4/15/2005
34.3 to
183.9 to
9.01
220.15
211.14
Deep
39.3
178.9
5MWS1
4/15/2005
31.7 to
201.9 to
14.95
235.15
220.2
Deep
41.7
191.9
5MWS2
4/15/2005
4.7 to 9.7
219.33 to
10.31
226.18
215.87
Shallow
214.33
5MWS3
4/15/2005
22.5 to
201.25 to
16.26
225.5
209.24
Deep
32.5
191.25
5MWS4
4/15/2005
14.0 to
204.45 to
14.18
221.45
207.27
Shallow
24.0
194.45
5MWS5
4/15/2005
22.0 to
195.05 to
11.84
219.05
207.21
Deep
32.0
185.05
5MWS6
4/15/2005
21.3 to
197.22 to
8.89
220.12
211.23
Deep
31.3
187.22
5MWS7
4/15/2005
12.3 to
205.68 to
8.92
220.28
211.36
Intermediateb
17.3
200.68
5MWS8
4/15/2005
2.8 to 7.8
215.19 to
9.58
220.79
211.21
Shallow
210.19
SWMU 103
MW 1
4/15/2005
5.0 to
209.9 to
8.06
217.21
209.15
Shallow
15.0
199.9
MW2
4/15/2005
26.0 to
189.5 to
7.98
217.66
209.68
Deep
36.0
179.5
MW3
4/15/2005
5.0 to
210.5 to
7.04
218.1
211.06
Shallow
15.0
200.5
MW4
4/15/2005
5.0 to
216.5 to
9.7
223.88
214.18
Shallow
15.0
206.5
MW5
4/15/2005
15.0 to
221 to
21.76
238.58
216.82
Shallow
25.0
211
MW6
4/14/2005
55.0 to
201.5 to
31.48
256.4
224.92
Deep
65.0
191.5
MW7
4/14/2005
30.0 to
226.6 to
33.12
256.48
223.36
Shallow
40.0
216.6
MW8
4/15/2005
25.0 to
228.4 to
27.58
255.98
228.4
Shallow
35.0
218.4
MW9
4/15/2005
48.0 to
205.4 to
27.99
255.97
227.98
Deep
58.0
195.4
MW10
4/15/2005
26.8 to
242.3 to
33.28
268.97
235.69
Shallow
36.8
232.3
MW 11
4/15/2005
71.7 to
197.2 to
33.15
268.64
235.49
Deep
81.7
187.2
MW12
4/15/2005
43.8 to
206.5 to
26.05
252.54
226.49
Deep
53.8
196.5
05-230(E)/052506
2-11

Table 2-1. Water Levels for April 2005, SWAM 103 (continued) _
Screened•
Elevation of
Elevation of
Screened
Interval
Depth to
Top of Casing
Potentiometric
Interval
(ft
Water
Measuring Point
Surface
Well
Well
Date
ft BGS
AMSL
ft below MP
ft AMSL
ft AMSL
Cate o °
MW 13
4/15/2005
20.8 to
229.6 to
25.86
252.73
226.87
Shallow
30.8
219.6
MW14
4/15/2005
4.85 to
224.9 to
6.92
229.46
222.54
Shallow
14.85
214.9
MW 15
4/15/2005
29.6 to
199.0 to
7.10
228.14
221.04
Deep
39.6 1
189.0
MW16
4/15/2005
3.6 to
212.1 to
8.81
218.49
209.68
Shallow
13.6
202.1
MW 17
4/15/2005
9.1 to
206.6 to
7.03
217.04
210.01
Deep
19.1
196.6
MW 18
4/15/2005
16.4 to
200.4 to
8.45
216.75
208.3
Deep
26.4
190.4
MW19
4/15/2005
4.2 to
212.6 to
8.47
216.66
208.19
Shallow
14.2
202.6
MW20
4/15/2005
20.45 to
218.2 to
18.92
240.95
222.03
Deep
30.45
208.2
MW21
4/15/2005
12.2 to
226.2 to
18.70
240.92
222.22
Shallow
22.2
216.2
MW22
4/13/2005
26.8 to
227.6 to
32.2
254.03
221.83
Shallow
36.8
217.6
MW23
4/12/2005
47.2 to
207.2 to
31.74
254.14
222.4
Deep
57.2
197.2
MW24
4/15/2005
18.5 to
197.8 to
8.84
218.46
209.62
Deep
28.5
187.8
MW25
4/15/2005
18.5 to
197.6 to
9.21
218.64
209.43
Deep
28.5
187.6
MW26
4/13/2005
34.0 to
230.0 to
23.8
263.64
239.84
Deep
44.0
220.0
MW27
4/13/2005
20.0 to
244.1 to
21.32
263.89
242.57
Shallow
30.0
234.1
MW28
4/15/2005
28.0 to
230.0 to
28.28
261.01
232.73
Deep
38.0
220.0
MW29
4/15/2005
34.0 to
203.6 to
11.35
240.39
229.04
Deep
44.0
193.6
MW30
4/15/2005
19.0 to
210.8 to
9.98
232.87
222.89
Deep
29.0
200.8
MW31
4/15/2005
19.0 to
207.6 to
13.50
229.52
216.02
Deep
29.0
197.6
MW32
4/15/2005
6.0 to
207.9 to
10.64
216.78
206.14
Shallow
16.0
197.9
MW33
4/15/2005
11.0 to
202.8 to
10.66
216.61
205.95
Deep
21.0
192.8
MW34
4/15/2005
55.0 to
N/A
30.54
253.97
223.43
Deep
65.0
MW35
4/14/2005
6.0 to
220.0 to
7.71
225.85
218.14
Shallow
16.0
210.0
MW36
4/14/2005
17.0 to
208.9 to
8.02
225.6
217.58
Deep
27.0
198.9
05-230(E)/052506 2-12

/rr i
Table 2-1. Water Levels for April 2005, SWMU 103 (continued)
Screened
Elevation of
Elevation of
Screened
Interval
Depth to
Top of Casing
Potentiometric
Interval
(ft
Water
Measuring Point
Surface
Well
Well
Date
ft BGS
AMSL)
(ft below MP
ft AMSL
ft AMSL
gategorf
MW37
4/11/2005
6.0 to
220.6 to
10.66,
226.47
215.81
Shallow
16.0
210.6
MW38
4/13/2005
17.0 to
209.7 to
10.68
226.44
215.76
Deep
27.0
199.7
MW39
4/15/2005
19.5 to
202.8 to
9.60
222.07
212.47
Deep
29.5
192.8
MW40
4/15/2005
16.0 to
205.1 to
8.19
220.94
212.75
Deep
26.0
195.1
MW41
4/12/2005
34.2 to
212:13 to
27.04
246.15
219.11
Deep
44.2
202.13
MW42
4/14/2005
26.7 to _
219.34 to
26.71
245.93
219.22
Shallow
36.7
209.34
MW43
4/13/2005
43.7 to
210.56 to
31.00
254.14
223.14
Deep
53.7
200.56
MW44
4/13/2005
26.7 to
227.61 to
31.20
254.18
222.98
Shallow
36.7
217.61
MW45
4/14/2005
26.7 to
226.92 to
29.21
253.52
224.31
Shallow
36.7
216.92
MW46
4/14/2005
26.7 to
227.98 to
30.90
254.57
223.67
Shallow
36.7
217.98
MW47
4/12/2005
26.8 to
227.73 to
32.94
254.36
221.42
Shallow
36.8
217.73
MW48
4/12/2005
33.2 to
221.38 to
33.03
254.45
224 A2
Deep
43.2
211.38
MW49
4/12/2005
26.7 to
227.52 to
32.80
253.93
221.13
Shallow
36.7
217.52
MW50
4/13/2005
41.7 to
212.51 to
32.60
253.8
221.20
Deep
51.7
202.51
IWl
4/13/2005
28.7 to
225.83 to
32.63
254.28
221.65
Deep
43.7
210.83
IW2
4/13/2005
28.8 to
225.96 to
33.04
254.52
221.48
Deep
43.8
210.96
IW3
4/13/2005
29.5 to
224.76 to
32.77
254.08
221.31
Deep
44.5
209.76
MW69344C
4/15/2005
24 to 34
1 31.02 1
254.37
223.35
Shallow
SWMUs 4 and
18
4MWS1
4/15/2005
20.5 to
201.3 to
10.75
223.43
212.68
Deep
30.5
191.3
4MWS3
4/15/2005
38.5 to
203 to
21.8
242.69
220.89
Deep
48.5
193
4MWS4
4/15/2005
14.0 to
202.3 to
4.72
217.49
212.77
Deep
24.0
192.3
4MWS5
4/15/2005
2.5 to 7.5
212.5 to
8.28
NA
NA
Shallow
207.5
4MWS6
4/15/2005
28.0 to
195.9 to
14.4
226.69
212.29
Deep
38.0
185.9
4MWS7
4/15/2005
13.0 to
211.0 to
13.98
226.96
212.98
Shallow
23.0
201.0
05-230(E)/052506
2-13

I
Table 2-1. Water Levels for April 2005, SWMU 103 (continued)
Screened
Elevation of
Elevation of
Screened
Interval
Depth to
Top of Casing
Potentiometric
Interval
(ft
Water
Measuring Point
Surface
Well
Well
Date
ft BGS
AMSL
ft below MP
ft AMSL
ft AMSL
Cate o
4MWS8
4/15/2005
26.0 to
200.5 to
15.42
229.67
214.25
Deep
36.0
190.5
4MWS9
4/15/2005
30.0 to
198.3 to
13.74
231.39
217.65
Deep
40.0 -
188.3
4MWS10
4/15/2005
54.0 to
199.5 to
32.15
256.65
224.5
Deep
64.0
189.5
4MWS11
4/15/2005
19.0 to
202.6 to
7.65
224.47
216.82
Deep
29.0
192.6
AEHA4-1
4/15/2005
14.45 to
224.4 to
20.22
241.2
220.98
Shallow
23.45
215.4
AEHA4-2
4/15/2005
8.89 to
217.6 to
11.12
228.12
217
Shallow
17.89
208.6
AEHA4-3
4/15/2005
5.21 to
218.2 to
12.06
225.58
213.52
Shallow
24.21
199.2
AEHA4-4
4/15/2005
4.88 to
218.1 to
11.98
225.65
213.67
Shallow
23.88
199.2
AEHA4-5
4/15/2005
7.68 to
209.0 to
8.94
219.27
210.33
Shallow`
16.68
200.0
AEHA4-6
4/15/2005
8.98 to
207.2 to
9.03
218.39
209.36
Shallow`
17.98
198.2
SJ MU8
8AMWS1
4/15/2005
16.3 to
199.59 to
10.92
218.46
207.54
Deep
26.3
189.59
'Shallow wells were screened across the water table. Deep wells were screened at the clay -confining layer (Cape Fear).
bThe water table is approximately 5 ft above the top of the screen. The screen elevation for 5MWS7 is between the screen
elevations for 5MWS6 and 5MWS7, which form a well cluster.
`The top of the screen is approximately 2 ft below the water table. There is no indication of clay in the boring log. It appears as
though the well was intended to be screened across the water table. The water level above the screen may be due to seasonal
fluctuations.
AMSL = Above mean sea level.
BGS = Below ground surface.
MP = Measuring point (top of casing).
SWMU = Solid waste management unit.
05-230(E)/052506 2-40

Table 2-2. Summary of Horizontal Gradients, SWAM 103
Field
Investigation
May 2001
March 2002
1 January 2003
1 September 2003
Aril 2005
Surficial
aquifer
Shallow
Deep
Shallow
Deep
Shallow
Deep
Shallow
Deep
Shallow
Deep
Predominant
groundwater
SW
SW
SW
SW
SW
SW
SW
SW
SW
SW
direction
Hydraulic
gradient
0.013
0.013
0.01
0.01
0.013
0.012
0.012
0.01
0.01
0.018
(ftifi)
SWMU = Solid waste management unit. SW = southwest.
2-18

Table 2-3. Summary of.Vertical Hydraulic Gradients at Well Pairs, SWMU 103
Well Pair
Vertical
Gradient
(ft/ft)
Vertical
Gradient
(ft/ft)
Vertical
Gradient
(ft/ft)
Vertical
Gradient
(ft/ft)
Vertical
Gradient
(ft/ft)
Flow
Direction
5/2/01
3/25/02
1/15/03
9113103
MWl and MW2
-0.023
-0.025
-0.029
-0.029
-0.0260
Upward
MW6 and MW7
-0.067
-0.059
-0.059
-0.054
-0.0622
Upward
MW8 and MW9
-0.0074
0.027
0.027
0.034
0.0183
Reverses
MW10 and MW11
0.0040
0.0
0.0011
0.0044
0.0044
Downward
MW12 and MW13
0.017
0.017
0.016
0.017
0.0165
Downward
MW14 and MW15
0.025
0.021
0.022
0.060
0.0579
Downward
MW16 and MW17
-0.031
-0.049
-0.058
-0.062
-0.0600
Upward
MW18 and MW19
-0.0082
-0.0090
-0.0041
-0.0090
-0.0090
U ward
MW20 and MW21
0.034
0.055
0.044
0.033
0.0237
Downward
MW22 and MW23
-0.026
-0.025
-0.027
-0.021
-0.0279
Upward
MW26 and MW27
NA
0.20
0.21
0.19
0.1936
Downward
MW32 and MW33
NA
0.0078
0.022
0.035
0.0373
Downward
MW35 and MW36
NA
NA
0.039
0.045
0.0505
Downward
MW37 and MW38
NA
NA
0.0046
-0.085
0.0046
Reverses
MW41 and MW42
NA
NA
NA
NA
0.0153
Downward
MW43 and MW44
NA
NA
NA
NA
-0.0094
Upward
MW47 and MW48
NA
NA
NA
NA
0.0000
Equal
MW49 and MW50
NA
NA
NA
NA
-0.0047
Upward
Note: Negative sign indicates upward hydraulic gradient.
NA = Not available.
SWMU = Solid waste management unit.
2-19

Table 2=4..Monitoring Well Construction Summary for March 2005, SWMU 103
Total.
,: Screened .
Top: of Filter.
Top of Casing
Date
Size/
Depth .
Interval :
Pack Elevation
Elevation
'Well No.
Installed
T i'
' .Coordinates
ft
ft.BGS :
ft BGS
.
Monitot Wells
MW41
3/19/05
2;in: PVC
N 50502.43
47.0
34.2 to 44.2
324.
246.15
E 2 007,428:83
MW42
3/19/0
24n. PVC:
N $05,863.65.
37.0
26.7.to 36.7
24.9.
245.93
E 2,007,436.56
MW43
3/17/051'.2-,in..
PVC
N 506,159.8i.
57.0
43:7 to 53.7
41.9.
254.14
E 2,007,699.31
MW44
3/18/05 =
24n.'PVC
'N 506,160.13
37.0
26.7.to 36.7
25.0
254.18.
E 2,007 692.77
MW45
3/18/05
24n. PVC.
N:506,259.97'
37.0
26.7to36.7
24.8 -
25152-
E 2,007,74235
MW46
3/18/05 :
14h. PVC
N 506,250.90
37.0
26.7 to 363
24.6
254.57.
E 2,007;626.49
MW47
3/16:05 '
2-in: PVC
:N 5.06,339,54
37.1
26:8.to 36.8
:24.0
254.36
E 2,007,110.33
MW48
3/16/0 .
2-in. PVC
N`506;336.84
44.0
33.2 to 43.2
31.0
254.45
E 2,007,113.49
MW49
3/15/05
2-in. PVC
N 506,322.39
37.5
267 to 36-3
24.5
253.93
E 2,007, T00.42 .
MW50
3/15/05
24n.. PVC •
.: N:506,318.84
52.4
41.7 to 51.7.
5214
253.8
E 2,007,105.02
Injection Wells.
IWl
3/17/05,
2-in. PVC.
: 'N:506;345.79
47.0
28.71to 43.7
26.8 .. ,_.:
254.28
E 1007,117.46
.
IW2
3/17/05, .
• 2-in: PVC
N 506,329.54.
.41.0
28:8't643.8
27.0`-
254.52
E 2,007,119.92
IW3
3/16/05
2-in.:PVC
N 506,341.86
57.0
29.5 to 44.15 ::
28.6 1
.254.08. .
E 2,007,100.83
Note: All elevations are National Geodetic Vertical Datum 1929.
PVC = Polyvinyl chloride.
2-25

i
Table 2-5. Field Parameter Measurements during Groundwater Sampling, SWMU 103
Field Re ding at Monitoring Well
Location
Date I
Well I
Type
pH I
S.U.(MS/cm)
Conductivity
Temperature
Turbidity
TUS)
DO
(m
Redoz
m
April 11-15, 2005
Monitorin Wells
MW6
4/13/05
Deep 1
4.53
0.050
19.47
8.9
7.31
147
MW7
4/12/05
Shallow
4.72
0.056
20.87
0.5
2.64
273
MW22
4/12/05
Shallow
5.10
0.040
20.10
10.4
7.16
222
MW23
4/11/05
Dee
4.81
0.043
19.43
17.8
7.80
247
MW26
4/14/05
Deep
4.37
0.061
17.86
14.1
6.79
26
MW27
4/14/05
Shallow
4.89
0.076
16.95
0.0
6.76
-95
MW35
4/14/05
Shallow
4.90
0.077
15.49
Clear
3.57
117
MW36
4/14/05
Shallow
4.20
0.062
15.93
Clear
5.51
217
MW37
4/11/05
Shallow
4.87
0.131
16.54
Clear
3.01
130
MW38
4/13/05
Shallow
4.53
0.060
17.27
Clear
0.29
192
MW41
4/12/05
Deep
6.04
0.079
19.22
Clear
1.01
-269
MW42
4/14/05
Shallow
4.88
0.059
18.75
0.0
5.00
-158
MW43
4/13/05
Dee
5.19
0.063
19.89
0.0
6.06
62
MW44
4/13/05
Shallow
4.82
0.066
19.92
0.0
6.38
71
MW45
4/14/05
Shallow
4.89
0.061
19.50
Clear
3.53
226
MW46
4/15/05
Shallow
5.84
0.106
16.99
Clear
3.21
-100
MW47
4/12/05
Shallow
6.32
0.171
18.98
Clear
1 0.78
2
MW48
4/12/05
Deep
5.27
0.049
19.63
Clear
4.14
165
MW49
4/12/05
Shallow
6.36
0.231
19.86
Clear
0.37
-52
MW50
4/13/05
Deep
4.59
0.041
18.06
Clear
5.65
125
In'ection Wells
IWl
4/14/05
Deep
5.34
0.067
19.18
Slightly
cloud
4.35
154
IW2
4/13/05
Deep
4.44
0.046
17.64
Clear
6.08
207
IW3
4/13/05
Dem
5.04
0.047
18.59
Clear
3.50
111
June 2-3 2005
Monitorin Wells
MW22
6/2/05
Shallow
5.76
0.161
19.47
86.7
0.35
190
MW23
6/2/05
Deep
4.02
0.043
19.71
144.0
7.00
305
MW47
6/2/05
Shallow
5.73
0.201
19.73
24.5
0.79
-385
MW48
6/2/05
Deep
5.50
0.082
20.03
15.8
0.87
-344
MW49
6/2/05
Shallow
5.84
0.222
19.85
1.4
0.62
42
MW50
6/2/OS
e
0.040
20.12
0.0
6.71
400
in* dion Wells
IWl
6/3/05
Deep
11.59
2.590
20.35
54.0
4.48
-444
IW2
6/3/05
Deep
11.92
5.080
21.81
1
325.0
19.70
-45
IW3
6/2/05
Dee
11.53
2.140
19.98
193.0
6.67
-103
June 28-29 2005
Monitoring Wells
MW22
6/29/05
Shallow
6.07
0.120
21.16
52.4
0.89
-43.5
MW23
6/29/05
Deep
4.50
0.042
20.85
46.0
6.89
405.3
MW47
6/28/05
Shallow
6.12
0.197
20.80
-2.9
0.25
-27.3
MW48
6/28/05
Deep
5.58
0.051
21.96
-1.8
4.66
148.5
05-230(E)/052506 2-27

Table 2-5. Field Parameter Measurements during Groundwater Sampling, SWMU 103 (continued)
Field.Readin .at Monitorin .Well:
Location
Date
Well
T . e.
pH : -
§:u.
Conductivity Temperature
mS/cm = . °C • ..
I Turbidity
TUs
I DO
m
Redo.x
m
MW49:
6/29/05•
Shallow
6.0
0.278 1 21.18 f
18.0 : J
. 0.32 1,
.-29.8:.
MW50
6/29/05..
.. Deep: "
4.79
0.042.:. 22.45.
-5.5
6.38
1.88.9
In'ecdon Wells . .
IWl
6/28/05..
:. Dee " : '-
:. 12.11 .
. , 4.376.
22.70 ' :.
. 84.9..
28.14
.-32.1
IW2
: 6/28/05 .
Deep::.:
12.23 .
• 8.162
22.82 :
483.0 ' :
15.14:
.-73.4 .
IW3.
6/28/05
-Deep
12.12.
5.114
21.99. • ..
263.3.
..12.31-
- -65-5
Jul 6-7 2005
MonitoringWells
MW22
7/06/05
Shallow. :::6.45
0.117
22.85.
8.2.
0.96
-13.7..
MW23
7/06/05 .
'Dee
.4.53
0.042.
21.50• :•
6:8 . ..
7.76
409,
MW47
7/07/05
Shallow.
UL
0:257 • .
21:28
2.0 .
0.75
-305
MW.48. .:
7/07/05
Dee
-5.18- _
0.287
21'.46 ` .:..::
102.4
0.22
54.1
MW49
7/06/05 :
Shallow- :
6.35
0.216
21.39 :: -
S 1.2 .
0.30
-42.7.
MW50.
7/06/05
Deep
4.73-
0.041
23.08:
-4.2 .
5.81
188.9
In'ection Wells
IW1
7/06/05'?.
:
11.19
4.451
23.1.
.6457.
3.41.
0.3.
.
IW2
7/06/05
EDEee
11.92
7.57
28.82.
438.0
14.40
-29.6
.IW3
7/06/05
Deep:
12.43
2.927. .
. 23.8: •
231.0 :.
12.42 .
-8.1
Au ust 2-5 2005 .
Monitorin Wells.:... :.
MW22 ....
8/04/05.,
',Shallow'.
6.04 •
0.140
23.20 ; .
116.0:.
0.48 _
-82 .
MW23::
-.8/04/05....:.Dee
.
4.59..
0.044
22:04
.14.3
.-.8.00
213
MW35.
8/04/05
:Shallow:
5.08:.
0.094.
21.95:
89:0
`2.42:
:21:.
MW37
8/04/05. -
- Shallow :
4.93 :
0.127
22.96.:.
142.0:.
2.99.
-9.. .
MW42
8/04/05:
Shallow.
4.51 :.
0.065
22.M...
33.3
2.64
.45•
MW47,
8/04/05 .
Shallow .
". 6.10
0.212
21.02 ..
0.8 .:
0:12
=50.
MW48
8/04/05 .
Dee
5.76.
0.117
23:00: , :
' 2.8 .
.2.09 .
89. .
MW49 '.
8/05/05.'
.. Shallow,
`• .6.28
0.291
22.12 •
. 53.4 :.
0.17 •
..-166..:
MW50
8/04/05.
Dmp
6.08.:
0.356.
21.57.
1.30,
4.28.
2...-
In'ection Wells
IWl
8/05/05 :
" :..Dee
: 12.07
6.29
21.17
307::::
29.37 .
-68:.
IW2
8/05/05
..•'Dee
12.05.
11.380
27.01....
499 : ..
.25A7
-155::
IW3
8/05/05
..Deep,'
6.70
4.140..
21.4a-,
658.0 •
0.98.
-233
DO = Dissolved oxygen.
NTU = Nephelometric turbidity unit.
Redox = Oxidation-reduction potential.
s.u. = Standard unit.
SWMU = Solid waste management unit.
05-230(E)/052506
2-44

Table 2-6. Slug Test Results for Wells at SWMU 103
Well ED
Test a
Hydraulic
Conductivity
cm/sec
Hydraulic
Conductivity
ft/da
IWl
Rising
4.70E-03
1.33E+01
IW2
Rising
4.04E-04
1.14E+00
IW3
Rising
1.47E-03
4.17E+00
MW6
Rising
2.21E-03
6.25E+00
Failing
4.21E-03
1.19E+01
MW7
Rising
1.96E-03
5.54E+00
MW9
Rising
6.21E-04
1.76E+00
Falling
4.23E-04
1.20E+00
MW22
Rising
3.59E-03
1.02E+01
MW23
Rising
1.13E-03
3.18E+00
Failing
8.01E-04
2.27E+00
MW34
Rising
3.21E-04
9.08E-01
Falling
3.69E-04
1.04E+00
MW45
Rising
1.52E-03
4.30E+00
Average:
1.69E-03
4.79E+00
Geometric mean:
1.16E-03
3.28E+00
Average for injection wells:
2.19E-03
6.20E+00
Geometric mean for injection wells:
1.41E-03
3.98E+00
SWMU = Solid waste management unit.
05-230(E)/052506 2-31

05-230(E)/052506
Table 2-7. Summary of Results for Bench -Scale Studies
Using CL-OutTM (April 2005), SWMU 103
Test Sequence
Test A
Test A
Test A
Sample ID
32231A
32231A
Test Type
Control
Inoculated
% Removal
1 1 2 2-Tetrachloroethane
48.0,J°
410 J°
15
Acetone
<50 UJ
57 J
NA
Chloroform
<5 UJ
<5.5 UJ
NA
Trichloroethene
21 J°
25 J°
-19
X lenes, total
<10 UJ
<10 UJ
NA
Test Sequence
Test B
Test B
Test B
Sample ID
32231B
32231B
Test Type
Control
Inoculated
% Removal
1,1 2 2-Tetrachloroethane
520 J°
390 P
25
Acetone
<50 UJ
36 J
NA
Chloroform
<5.4 UJ
<5 UJ
NA
Trichloroethene
27 J°
16 J°
41
X lenes total
<10 UJ
<10 UJ
NA
• I
Test Sequence
Test C
Test C
Test C
Sample ID
32231C
32231C
Test Tvve
Control
Inoculated
% Removal
1 1 2,2-Tetrachloroethane
500 J°
430 J°
14
Acetone
4.8 J
44 J
NA
Chloroform
<5 UJ
<5 UJ
NA
Trichloroethene
19 J°
21 P
-11
X lenes total
<10 UJ
<10 UJ
NA
Test Sequence
Test D
Test D
Test D
Sample ID
32231D
32231D
Test Type
Control
Inoculated
% Removal
1,1,2 2-Tetrachloroethane
510 J°
410 J°
20
Acetone
<50 UJ
62 J
NA
Chloroform
<5 UJ
<5 UJ
NA
Trichloroethene
22 J°
15 J°
32
X lenes total
4.7 J
<10 UJ
NA
° Results exceed the screening criteria.
SWMU = Solid waste management unit.
2-32

Table 2-8. Summary of Perme0x@, CL-OutTM, and Potable Water Injections u
Conducted during the SWMU 103 Pilot Study
Injection
Well
PermeOx@'
bs
CL-OutTm
al
Potable Water
(gal)
05/25/05
1 06/28/05
05/25-05/26/05
06/29-06/30/05
05/26/05
6/29-06/30/05
IW-1
—206
—16
55
55
117
138
IW-2
—206
—16
55
55
45
52
IW-3
_20b
—16
55
55
117
138
'Powdered form of Perme0x® was mixed with potable water to produce a slurry for injection.
bApproximately 5 lbs placed into in -situ diffusers suspended in each well for additional time -release of Perme0x®
05-230(E)/052506 2-32

Table.2-9. Comparison -of Critical_ Field Parameters Collected during In -Situ Pilot- Study, SWMU 103
Location
MW22
Shallow
MW23(Dee
Baseline
Pert. #1
Perf. #2
- Perf. #3 •
Perf. #4
Baseline
Perf. #1.
Perf: #2
Perf. #3
Perf #4
Parameter
04/12/05
1 06/62/05 "
.06/29/05
07/06/05
.08/02/O5.
.-64111105
.06/02/05.
. 06/19/05
01/06/05-
08/02/05
DO
7.16.
0.35
0.89.
0.96.
0.48'..
7.8
7.
6.89.
7.76.
18
H
51
1 5.76.
6.07
6.45 .
604.
4.81
4.02
4.5
4.53
4.59
Redox
222
190 '
-43.5
-13.7
-82
247...
305
405.3 .
409 .
213
Location
MBV47.
Shallow
MW48. ee
Baseline
Pert. #1
Perf.-.#2
Perf #3
Perf.#4
Baseline
Perf..#1
' Perf.-#2 ..
Perf.'.#3
- -Pert. #4
Parameter
04/12/05
06/02/05 -1
06/29/05
07/06/05 .
08/02/05
04/12/05
1 06/02/05
1 66/29/05
1 07/06/05 "
08/02/05
00'.
0.78 "
0:79 .
0.25 " .
035
-0.12 "-
4.14'
0.87
4.66
0.22
2.09
H
...6.32
533
6.12
6:0.1 .
6.1 . " "
5.27 ..'
5.5
5:58 ..
5.18
5.76" .
Redox
2
-385
-21.3
-305"
-50
165
-344
148.5.
54.1...
89 ,.
Location:
MW49. Shallow
MW50
ee
Baseline
Perf. #1
1 Perf.' #2.
1 Perf. #3
Perf. #4.
Baseline
Perf.#1
Perf. #2
1, Perf..#3
Perf #4
Parameter
04/12/05
06/02/05
1 06/29/05
1 07/06/05
1 08/02/05
04/13/05
1 06/02/05
06/29/05 "
. 07/06/05
08/02/05
DO
0:37
0.62
0.32
0.3
0.17
"5.65
6.71_
638
5.81
4.28
H
6.36
5.84-
6.13
6.35 -
6.28
4.59-
4.67
4.79-
4.73
6.08
Redox
-52
42
-29.8
-42.7
-166
125
400
188.9
188.9
2
Location
IW1(Deep)
IW2 ee
Baseline .
Perf #1
Perf #2
Perf. #3
Perf. #4..
Baseline
Perf. #1..
Perf #2
1. Perf.' #3.
Perf #4
Parameter
04/14/05 .1
06/03/05
1 06/29/05- .
07/06/05
08/02/05 .
" Q4/13/05
1 06/03/05:.
06/29/05
1 07/66/05
' 08/02/05
DO
4.35
4.48
28.14 "
3.41
.. .29.37 "
6.08 . "
19:7 ....
.15.14
14.4 _
." .25.41 "
H
5.34
11.59
12.11
-11.19
12.07'
4.44
11.92
12.23
11.92
A2.05 "
Redox
154
.-444
-32.1
-60.3
-68
207
-45
-73.4
-29.6
-155
Location .
_
IWa(Deep).
Baseline
"Perf. #1
Perf: #2
Perf. #3
::"Perf #4
Parameter
04/12/05 .
06/02/05.
06/29/05
07/06/05 "
08/02/O5
DO
3.5
6.67.,
12.31 .
12.42.
0.98 .' =
H
5.04.
1l'.53.
12.12.E
12.43
6.7
Redox
111
-403.
-65.5: -
781
-233
DO = Dissolved oxygen. Redox = Oxidation;reduction potential.

Table 2-M Summary of Results of Groundwater for. Pilot Study (April. =.August2005); SWMU_103
Station
NC GW
IW-1 ."
IW-1
Iw-1
IW-1
IW-1 .
IW-2
IW-2tlW-2:1W-2
Sam le ID
Standard 2L
350111
350113.
350114
-350115
350116
350211
350213350215Date
or IMAC
04/14/05
06/03/05
06/28/05
07/06/05
08/05/05
04/13/05
06/03/0507/06/O5
T e.of Sam fin durin Pilot Stud
Baseline
1st Perform,
7 da s
2nd Perform,
30 da s
3rdPerform;
7 da s
4th Perform;
30 da s.Baseline
1st Perform,3rdPerform,
7 da s7
da s
T e of Well
Dee
Dee
Dee "
Dee -
Dee
Dee
Dee
Dee
Volatile Organics Compounds L
1,1 2;2-Tetrachloroethane
1 1 2-Trichloroethane
0.17
280 =*= .
<10 U
1.5 =*
<1 U
<1 U'.
<I U
<1 U
<1 U
<1 U
2.2 =* _
570 =*
<I.U-
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
1 1-Dichloroethene
7
<10 U
<I UJ
0.54 J
<l U
2.7 =
<1 U
<1 UJ
<1 U
<1 U
1 2-Dichloroethane
0.38
<10 U -
<1 U
<1 U,
<1 U
<I U
<1 U
<1 U
.<I U
<1 U"
1 2-Dichloroethene
100
<10 U
R:C04,CO5
<1 UJ
<1 UJ
4.7 =
0.61 J.
R.-004 CO5
<1 UJ
<1 UJ .
2-Butanone
4,200
1 <I00 U
86 J
<200 UJ
110 =
<290 U
<10 U
32 =
35 =
260 J
2-Hezanone
280
<100 U.
<10 U
<10 U
<10 U
<10 U
<I0 U-
<10 U -
<10 U - -
<10 U
4-Meth 1-2- entanone
<100 U
<10 U
<10 U
3.1 J
<10 U : "
<10 U.
<10 U -
2.31.
.9.5. J
Acetone
700
<100 U
<150 U
<200 UJ
210 =
<700 UJ
<l0 U
160 =
3,800 =*
1,500 = %
Benzene
1
20 =*
16 =*
24 =*
12 =*
21 =*
<1 U
13 =*
1.9 =*
4.3 =*
Bromodichloromethane
0.6
<10U
<1 U
<1 U
..<I U
<1 U
<1.U.
<1 U
<1 U
0.38"J*
Bromoform
0.19
<10 U
<1 U
<1 U
<1 U
<1 U
<1 U ..
<1 U
<1-U
<1 U .
Chlorobenzene -
50
<10 U
<l. U
<1 U
<l. U
<1 U
<1' U
<1 U "
<1 U-
<1 U
Chloroform
70
3.4 J*
5.3 =*
0.94 J* -
7.5 =* "
0.61 J* -
1.4 =*
5.7 =*
2 =*
10 =*
Chloromethane
2:6
<10 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<I U
Dibromochloromethane
0.41
<10 U
<1 U
<1 U
<1 U
1.5 =*.
<1 U
<1 U
<1 U
<1 U
Eth lbenzene
550
180 =*
190 =*
210 J* -
170 =*
170 =*.
<1 U
110 =
11 =
14 =
Methyl tertiary butyl ether MTBE
200
<10 U
32 J*
<1 U
<1 U
39 =*
7 =*
34 J*
10 =*
17 J*
Meth lene .Chloride
4.6
<10 U-
<1 "U.
<I. U
<l U.
<1 U .
<1 U
<1 U
<1 U:
<1 U
Styrene
100" .
<10 U.
<1 U .
<1 U
<I U
<l U.
<1-U
<1 U
<1 U-
<1 U .
Tetrachloroethene
0.7
<10 U
1.1 =*".
0.96 J*
<1 U.
0.92 J*
2.6 =*
0.63 J*"
<1 U
<1 U.
Toluene
1 000
84 =*
110 =*
1907"
92 =* "
<120 U
<I U
<68 U
8.3 =
15 _.
Trichloroethene
2.8
40 =*.
140 =*
96 J*
34 =*
67.=*
78 =*
95 =*
9:3.=*
13 ="
X lenes total
530
2;100 =*
1 700 =*
2 500 J*
1,400 =* .
770 =*..
0.83 J
580 =*
67 =*
72 =*
Anions /L)
Chloride
250 000
5 400 =
I 1 000 =
6,500 = 10,000 =
6,400 =
4;800 =
7,700 =
14,000 =
19;000 =
Nitrate
10,000
1,000 =
151000 =*
500 = 21,000 =*
320 =
1 700 =*.
32,000 =*
14 000 =*
30 000 =*
Miscellaneous ftlL
Total Organic Carbon .1 410 J 2,130,000 = " 95,600 = 11,930,000 =1 69,700 = 1,350 J . 1,420,000 _ . 1 080 000 = 909,000. =
Bacteria. L)
Total Aerobic Plate Count.
160,000
7,000,000
- .800 000 . -1
400,000 .
300,000
60 000.
I.3E8
10 000 .
: 2 500 000
Total Pseudomonad Plate Count
NA-
1,000,000
.. 100 000
100 000.
200,000.
NA...
4 000,000
<10 000
1,000,000
Miscellaneous (' L
Chemical Oxygen Demand 7,000 J NA .. NA NA NA 16,000 = NA NA" . NA

Station
. NC GW
IIW-2 .
IW-3.
IW-3 .
IW-3
IW-3 -
IW-3
NM-22
MW-22
NM-22
Sam le ED
Standard 2L.
350216
350311 '
350313..
350314
.350315
350316
322212
322214
322215. .
Date.
or IlVIAC
08/05/05
' 04/13/05
06/02/05
06/28/05
07/06/05' .
08/05/05
04/12/05 .
06/02/05 .
06/27/05 .
T e of Sam lin durin Pilot $tud
4th Perform,
- 30 days
Baseline
1st Perform,
7 da s .
2nd Perform,
30. days
3cd Perform;
7 days
4th.Perfor
30 days
Baseline
1st Perform,
7 days
2nd Perform,
30.da s
Type of Well .
Dee6
Deep
Dee
Mep
mDeep
beep.
Shallow
Bk d.
Shallow
Ble d.
Shallow
Bk d.
Volatile Or aiiics Com ourids /L
1,1,2 2-Tetrachloroethane
0:17
<1 U.
250.=*
17 =* . -
<1 U
3.3 =*
32 =*
100.=*:
36 =*
5&=*
1,3,2-Trichloroethane
<1 U
<1 U
<1 U : -
- <IU
<l U
4.S.J*.
<SO U
<1 U.
<1 U
1 1-Dichloroethene_
..7
0:69 J -
<1 U
<1 U
<1.U.
<I U
<5.0
<50 U..
<1-U :.
<1 U.
1 2-Diebloroethane
0.38
<1 U
<1 U.,
<1.0
<1 U .
<l U.-
<5-U .'.
<50 U
<1 U:
<I U
1 2-Dichloroethene
100
1.4 =
1.1'=
<1 U
<1 UJ
<1 UJ
<5 U
<50 U,
<l U
<1 UJ
2-Butanone
4 200
2,400 J*
.<I0 U ' .
29 =
110 J
230'J
3,500 J* •
<500 U
<10 U
<10 U
2=Hexanorie.
280
11.=-
<10 U
<10 U
<10 U
<10 U
<50 U...
<500 U.
<10 U..
<10 U .
4-Meth1-2- entanone
<l0 U -.
<10 U
' <10 U .
5.9 J
<10 U
<50 U
.<500 U
.<10.0
<l0 U
Acetone
700.
5 900 P -
<10,U .
180 .=
170 J
<500.0
.7 000 J*
<500 U
<10 U
<10 U
Benzene
1
25 =* _
..0.46J*
3.8 =*
14 =*
58 =*
130 =*.
66 =*
31, _*.
37.=*
Bromodichloromethane .
0.6
<1 U
<1 U
<1 U
<1 U
<1 U
<5 U
<50 U.
: <1 U .
<I U
Bromoform
0.19
<1,U.
<I U
<1.0
<1 U,
<1 U
<5 U
<50 U
<1 U
<1 U
Chlorobenzerie
50
<1.0
<1.0
<1 U
<1 U
<1 U
<5 U
<50 U
<I U
<1 U
Chloroform
.70.
.0.91 J*
0.91 J*
3.6 =*
1.2 =*
8.1 =*
<5 U
82 =*
: ° <I U'
<1 U
Chloromethane
2.6
0.55 J
<1 U
<1 U
<1 U
<1 U
<5 U
<50 U
<1 U
1.9 =
Dibromochloromethane
0:41
<l U.
<1 U
<1-U
<I-U
<1 U
<5•U
<50 U
<l U
<1 U
Eth lbenzene
550
95 J
12 =
69 =
96=
610 =*
1,200 =*
1200 =*
800 =*
510 =*
Meth l .tertia butyl ether MTBE
200
140 J*
<l U
2.2 =
<I U
28 J*
80 =
<50 U -
. <I U.
<t U
Methylene Chloride
'4.6
<1 U
<1 U
.<1 U
<1-U
<I U.
<5 U
<50 U -
-<1 U ..
<1 U
Siyr6ne
100
<1.U-
<1 U.
- <l U
<l U.
<l U
<5 U,
<50.0
<1.0 : -
<l .0
Tetrachloroethene
0.7
0:36 7* •
1.4 =* '
0.92 J*
0.58 J*
<1 U
<5 U
<50 U.
0.39 J*
0.51 P
Toluene
1,000
<100 U
4 =
43 J
120 =*
700 =*
1,700 =*
490 =*
Q90 U
<180 U
Trichloroethene
2.8
38 =*.
34 =*
93 _*
. 31 =*
21.=*
25 =*.
<50 U
7.6 =*
9.6.=
X leries total
530
590 J*
83. _* .
210 =*
770 =*
3,100.=" :
7,200 J* 1
6,500 =*j
5,100 =*
3,500 =*
Anions
( /L) - -
Chloride
250 000:
1.7 000=
5 100 =
-. 7,300 =
9,900 =
.12,000 =...
9,100 =
6 900-=....
4 900 =." ..
7 500 =
Nitrate
10,000
15,000 =*
1,200 =*
=17 000 =*.
2 800 =*
20,000 =*
1 400.=*
<100.0
290.=
<100 U
Miscellaneous /L
Total Organic Carbon 956,000 J I . 1 800 J 1,300 000 = - 400 000 = 1 760,000 =1 855,000 J 3,190 = 3,500 J 3,980 =
Bacfe'vla /L) . .
Total Aerobic Plate Count.
400 000 -.
30,000 - 1
7,000,000.
: 1300 000
3.3E7
500,000
110,000 .
IE7 .
250 000 .
Total-Pseudomonad Plate. Count
<I O 000 I
NA .. 1.
1 000 000 -
. - 200 000 I.
3.2E7
200,000
NA 1
1,000 000 -1
<10 000
Miscellaneous %L ..
Chemical Oxygen Demand NA <10 000 U NA NA NA NA 21,000 = NA. NA.

Table 2-10. Summary of Results of Groundwater for Pilot Study (April - August 2005), SWMU 103 (continued)
Station
NC GW
NM-22
MW-22
MW-23
MW-23
MW-23
NM-23
NM-23
MW47
MW47
Sample ID
Standard 2L
322216
322217
322312
322314
322315
322316
322317
324711
324713
Date
or IMAC
07/06/05
08/04/05
04/12/05
06/02/05
06/27/05
07/06/05
08/04/05
04/12/05
06/02/05
Type of Sampling during Pilot Study
3rd Perform,
7 days
4th Perform,
30 days
Baseline
1st Perform,
7 days
2nd Perform,
30 days
3rd Perform,
7 days
4th Perform,
30 days
Baseline
1st Perform,
7 days
Tvve of Well
Shallow
Bk d.
Shallow
Bk d.
Deep
Bkgd.
Deep Bkgd.1
Deep Bkgd.,
Deep Bk d.
Deep Bk d.
Shallow
Shallow
Volatile Or anics Compounds /L
1 1 2 2-Tetrachloroethane
0.17
53 =*
59 =*
420 =*
1 460 =*
380 =*
440 =*
340 =*
110 =*
<1 U
1 1 2-Trichloroethane
<1 U
<1 U
<5 U
0.34 J*
<1 U
0.32 J*
<1 U
<100 U
<1 U
1 1-Dichloroethene
7
<1 U
<1 U
<5 U
<1 U
<1 U
<1 U
<1 U
<100 U
<1 U
1 2-Dichloroethane
0.38
<1 U
<1 U
<5 U
<1 U
<1 U
<1 U
<1 U
<100 U
<1 U
1 2-Dichloroethene
100
<1 UJ
<1 UJ
<5 U
<1 U
<1 UJ
<1 UJ
<1 UJ
<]00 U
<1 U
2-Butanone
4,200
<10 U
<10 U
<50 U
<10 U
<10 U
<10 U
<10 U
<1000 U
<10 U
2-Hexanone
280
<10 U
<10 U
<50 U
<10 U
<10 U
<10 U
<10 U
<1000 U
<10 U
4-Meth 1-2- entanone
<10 U
<10 U
<50 U
<10 U
<10 U
<10 U
<10 U
<1000 U
<10 U
Acetone
700
<10 U
<10 UJ
<50 U
0.87 J
<10 U
<10 U
<10 UJ
<1000 U
<10 U
Benzene
1
35 =*
39 J*
<5 U
<1 U
<1 U
<1 U
<1 U
140 =*
120 =*
Bromodichloromethane
0.6
<1 U
2.5 J*
<5 U
<1 U
<1 U
<1 U
<1 U
<100 U
<1 U
Bromoform
0.19
<1 U
<1 U
<5 U
<1 U
<1 U
<1 U
1.4 =*
<100 U
<1 U
Chlorobenzene
50
<1 U
<1 U
<5 U
<1 U
<1 U
<1 U
<1 U
<100 U
<1 U
Chloroform
70
<1 U
<1 U
5.5 =*
<1 U
0.9 J*
0.95 J*
0.87 J*
<100 U
<1 U
Chloromethane
2.6
<1 U
<1 U
<5 U
<1 U
<1 U
<1 U
<1 U
<100 U
<1 U
Dibromochloromethane
0.41
<1 U
<1 U
<5 U
<1 U
<1 U
<1 U
<1 U
<100 U
<1 U
Eth Ibenzene
550
790 =*
760 =*
<5 U
<1 U
<1 U
0.5 J
<1 U
1,600 =*
1,700 =*
Methyl tertiary butyl ether MTBE
200
<1 U
<1 U
<5 U
<1 U
<1 U
<1 U
<1 U
150 =*
160 =*
Methylene Chloride
4.6
<1 U
<1 U
<5 U
<1 U
<1 U
<1 U
<l U
<100 U
<1 U
Styrene
100
<1 U
<1 U
<5 U
<1 U
<1 U
<1 U
<1 U
<100 U
<1 U
Tetrachloroethene
0.7
0.53 J*
0.48 J*
<5 U
2.6 =*
2.4 =*
2.8 =*
2.4 =*
<100 U
0.44 J*
Toluene
1,000
<270 U
290 =*
I <5 U
<1 U
<I.1 U
<1 U
<1 U
940 =*
1 960 =*
Trichloroethene
2.8
9.9 =*
9.6 J*
22 =*
61 J*
33 =*
51 J*
45 =*
<100 U
15 =*
X lenes total
530
4,900 =*
1,500 J*
<10 U
<2 U
<2 U
<3.8 U
<2 UJ
10 000 =*
19,000 =*
Anions L)
Chloride
250,000
7,300 =
6,400 =
4 300 =
4,700 =
4,900 =
5,200 =
4,100 =
7.006 =
7,600 =
Nitrate
10,000
<100 U
<100 U
1 1 600 =*
2,300 =*
2,400 =*
2 300 =*
2,100 =*
<100 U
1 100 =*
Miscellaneous
Total Organic Carbon 4 120 = 1 140 J 1 070 J <2 000 U 1 150 J 1 640 J <2 000 U 5 820 = 199 000 =
Bacteria
Total Aerobic Plate Count
1 600 000
600,000
60,000 3 000 000
200 000
200 000
900 000
380,000
IE7
Total Pseudomonad Plate Count
<100 000
200,000
NA <100 000
100,000
<100 000
<10 000
NA
2,000,000
Miscellaneous
Chemical Oxygen Demand NA NA <5 300 U NA NA NA NA 55 000 = NA

y
Table 2-10. Summary of Results of Groundwater for Pilot Study (April - August 2005), SWMU 103 (continued)
Station
NC GW
MW47
MW47
MW47
MW48
MW48
MW48
MW48
MW48
MW49
Sample ID
Standard 2L
324714
324715
324716
324811
324813
324814
324815
324816
324911
Date
or IMAC
06/28/05
07/07/05
08/04/05
04/12/05
06/02/05
06/28/05
07/07/05
08/04/05
04/12/05
Type of Sampling during Pilot Study
2nd Perform,
30 days
3rd Perform,
7 days
4th Perform,
30 days
Baseline
1st Perform,
7 days
2nd Perform,
30 days
3rd Perform,
7 days
4th Perform,
30 days
Baseline
Type of Well
Shallow
Shallow
Shallow
Deep
Deep
Deep
Deep
Deep
Shallow
Volatile Or anics Compounds /L
1 1 2,2-Tetrachloroethane
0.17
210 =*
90 =*
96 =*
340 =*
250 =*
330 =*
<5 U
300 =*
86 =*
1 1 2-Trichloroethane
<1 U
<5 U
<1 U
<10 U .z
<5 U
2.7 =*
<5 U
11 =*
<50 U
1,1-Dichloroethene
7
<1 U
<5 U
<1 U
<IO U
<5 U
<1 U
<5 U
<1 U
<50 U
1 2-Dichloroethane
0.38
<1 U
<5 U
<1 U
<IO U
<5 U
<1 U
<5 U
<1 U
<50 U
1,2-Dichloroethene
100
<1 UJ
<5 UJ
0.35 J
<10 U
<5 U
<1 UJ
<5 UJ
3.1 J
<50 U
2-Butanone
4,200
<10 U
<50 U
40 =
I <100 U
<50 U
<10 U
<50 U
<I O U
<500 U
2-Hexanone
280
<10 U
<50 U
<10 U
<100 U
<50 U
<I O U
<50 U
<I O U
<500 U
4-Meth1-2- entanone
<10 U
<50 U
<I O U
<100 U
<50 U
<10 U
<50 U
<10 U
<500 U
Acetone
700
<10 U
<50 U
<10 UJ
<100 U
<50 U
<I O U
<50 U
<100 U
<500 U
Benzene
1
61 J*
96 =*
100 =*
4.7 J*
7.6 =*
<1 U
2.7 J*
1.8 =*
100 =*
Bromodichloromethane
0.6
<1 U
<5 U
<1 U
<10 U
<5 U
<1 U
<5 U
<1 U
<50 U
Bromoform
0.19
<1 U
<5 U
<1 U
<10 U
<5 U
<1 U
<5 U
<1 U
<50 U
Chlorobenzene
50
<1 U
<5 U
<1 U
<IO U
<5 U
<1 U
<5 U
<1 U
<50 U
Chloroform
70
<1 U
<5 U
<1 U
17 =*
3.3 J*
1.2 =*
<5 U
0.62 J*
<50 U
Chloromethane
2.6
<1 U
<5 U
<1 U
<10 U
<5 U
<1 U
<5 U
<1 U
<50 U
Dibromochloromethane
0.41
<1 U
<5 U
<1 U
<I O U
<5 U
<1 U
<5 U
<1 U
<50 U
Eth ]benzene
550
1,100 =*
1,400 =*
1,300 =*
31 =
82 =
0.36 J
40 =
23 =
1,000 =*
Methyl tertiary butyl ether MTBE
200
<1 U
<5 U
110 =*
18 =*
15 =*
<1 U
3 J
2.6 =
99 =*
Methylene Chloride
4.6
<1 U
<5 U
<1 U
<10 U
<5 U
<1 U
<5 U
<1 U
<50 U
Styrene
100
<1 U
<5 U
<1 U
<I O U
<5 U
<1 U
<5 U
<1 U
<50 U
Tetrachloroethene
0.7
<1 U
<5 U
0.49 J*
<I0 U
<5 U
2.1 =*
2.1 J*
2.2 =*
<50 U
Toluene
1,000
560 =*
710 =*
770 =*
32 =
51 =
<l.l U
39 =
14 =
490 =*
Trichloroethene
2.8
14 =*
<5 U
14 =*
50 =*
39 =*
28 =*
42 =*
40 =*
17 J*
X lenes, total
530
7,200 =*
8,300 J*
8,900 J*
420 =*
860 =*
<3.1 U
310 =*
52 J*
6,000 =*
Anions /L
Chloride
250,000
7,600 =
7,600 =
6,700 =
5,200 =
6,000 =
5,600 =
6,800 =
4,700 =
6,700 =
Nitrate
10,000
<100 U
610 =
:. <100 U
1,200 =*
360 =
1,900 =*
1,600 =*
570 =
<100 U
Miscellaneous /L
Total Organic Carbon 12,000 = 164,000 = 1 1,8,800 = 1,720 J 146,000 = 3,830 = 297,000 = 9,200
Bacteria /L)
Total Aerobic Plate Count
120,000
600,000 °
200,000
60,000
1.8E8
20,000
1,500,000
400,000
260,000
Total Pseudomonad Plate Count
100,000
200,000 a
<10 000
NA
5E7
1,000
1,300,000
<10 000
NA
Miscellaneous /L
Chemical Oxygen Demand NA NAI NA 1 12,000 = NA NA NA NA 39,000 =

Table 2-10. Summary of Results of Groundwater for Pilot Study (April - August 2005), SWMU 103 (continued)
Station
NC GW
MW49
MW49
MW49
MW49
MW-50
MW-50
MW-50
NM-50
MW-50
Sample ID
Standard 2L
324913
324914
324915
324916
325011
325013
325014
325015
325016
Date
or 1MAC
06/02/05
06/29/05
07/06/05
08/05/05
04/13/05
06/02/05
06/29/05
07/06/05
08/04/05
Type of Sampling during Pilot Study
1st Perform,
7 days
2nd Perform,
30 days
3rd Perform,
7 days
4th Perform,
30 days
Baseline
1st Perform,
7 days
2nd Perform,
30 days
3rd Perform,
7 days
4th Perform,
30 days
Tvve of Well
Shallow
Shallow
Shallow
Shallow
Deep
Deep
Deep
Deep
Dee
Volatile Or anics Com ounds /L
1 1 2 2-Tetrachloroethane
0.17
71 =*
69 J*
69 =*
70 =*
470 =*
370 =*
350 =*
400 =*
360 =*
1 1 2-Trichloroethane
<1 U
<1 U
<1 U
<1 U
<1 U
0.36 J*
<1 U
0.32 J*
11=*
1 1-Dichloroethene
7
<1 U
<1 U
0.54 J
<1 U
<1 U
<1 U
<1 U
<1 U
2.8 J
1 2-Dichloroethane
0.38
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
2.1 J*
1 2-Dichloroethene
100
<1 U
<1 UJ
<1 UJ
3 J
0.48 J
<1 U
<1 UJ
<1 UJ
8.3 J*
2-Butanone
4,200
<10 U
<10 U
<I O U
<21 U
<10 U
<10 U
<10 U
<10 U
<50 U
2-Hexanone
280
<10 U
<10 U.
<I O U
<10 U
<10 U
<10 U
<I O U
<10 U
<50 U
4-Meth 1-2- entanone
<10 U
<I O U
<10 U
<10 U
<10 U
<I O U
<10 U
<I O U
<50 U
Acetone
700
<10 U
<10 U
<10 U
<270 UJ
<10 U
<10 U
<10 U
<10 U
<72 U
Benzene
1
83 =*
59 J*
66 =*
54 =*
0.42 J*
<1 U
<1 U
<1 U
<5 U
Bromodichloromethane
0.6
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<5 U
Bromofonn
0.19
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<5 U
Chlorobenzene
50
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<5 U
Chloroform
70
<1 U
<1 U
<1 U
<1 U
1.9 =*
1.5 =*
1 =*
1.2 =*
<5 U
Chloromethane
2.6
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<5 U
Dibromochloromethane
0.41
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<5 U
Eth ]benzene
550
990 =*
490 =*
840 =*
730 =*
3.8 =
<1 U
0.44 J
0.52 J
2.4 J
Methyl tertiary butyl ether MTBE
200
67 =*
<1 U
<1 U
97 =*
<1 U
<1 U
<1 U
<1 U
<5 U
Methylene Chloride
4.6
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
0.31 J
<1 U
<5 U
Styrene
100
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<1 U
<5 U
Tetrachloroethene
0.7
0.5 J*
0.52 J*
0.49 J*
0.54 J*
2.2 =*
2.1 =*
2.3 =*
2.5 =*
2.4 J*
Toluene
1,000
500 =*
330 J*
350 =*
320 =*
5 =
<1 U
<1 U
<1 U
<5 U
Trichloroethene
2.8
12 =*
12 =*
1 12 =*
13 J*
66 =*
54 =*
27 =*
57 =*
1 53 =*
X lens, total
530
10,000 =*
3,500 =*
1 5,300 =*
1,500 =*
30 =*
1.1 J
3.4 =
<3.9 U
<27 UJ
Anions L)
Chloride
250,000
7,30=
7,700 =
1 7,500 =
1 6,500 =
4.900 =
5,000 =
5,100 =
4,800 =
5,000 =
Nitrate
10,000
<100 U
<100 U
I <100 U
I <100 U
1,600 =*
2 300 =*
2 600 =*
2,600 =*
1,400 =*
Miscellaneous
Total Organic Carbon 4,710 J 9,610 = 5,920 = 5,510 = 1,250 J <1 450 U 1,700 J 1,750 J 27,200 =
Bacteria /L
Total Aerobic Plate Count
4E7
70,000
1,500,000
400,000 °
40,000
NA
100,000
100,000
900,000
Total Pseudomonad Plate Count
1,000,000
<10 000
400,000
100,000 °
NA
NA
10,000
<100 000
200,000
MiscellaneousftlL
Chemical Oxygen Demand NA NA NA NA 7200 J NA NA NA NA
Note: Bacteria results for April 12-14, 2005, were collected on May 23, 2005, prior to the first injection.
° Bacteria result from the duplicate sample. * Result exceeds screening criteria.
* Indicates concentration above the screening criteria.
t

9pn1611n'2_1 Cllmm9rc7 Ctatietirc nf-Annlvtac DpfiartPrl in Cnhcllrfnrp gnil_:-RVOMTA03
to .
Results > .
Detection
Limit _ .
Minimum
Detect
Maximum
Detect
Station at
Maximum
EPARegi
on 9 Res.
Soil PRG
Max- Detect.LDeAnal
>Res. PRG
HHCOPC?
Justification .
Volatile Organics Coin ounds (m /k" )
1,1,2,2-Tetrachloroethane
2/33
0.0029'
0.023
103SB-8
0.41
No
0/33
No
Max Detect <Residential PRG
2-Butanorie
7/33
0.0017
' 0.078
4PH41 .
2,200 : "
No..0/33.
No
Max Detect < Residential PRG
4-Meth 1-2- entanone
5/33
0.0014
0.0027
4PH42 .
-530 .".
No
0/33
No
Max Detect < Residential PRG.
Acetone
17/33
0.0056
0.079
MW23 ..
1,400.. -
No
0/33.
No
Max Detect < Residential PRG .
. Benzene
3/33 .
0.0001
0.036
.4PH40 - .
0.64 :..
No .
0/33'
-No:. •
'Max Detect <Residential PRG
Carbon Disulfide
6/33
0.0019
0.0057
4PH43
36.
No
0/33
No.
Max Detect < Residential PRG
- Chloroform.
4/33
0:00051
0.044
4PH41 " .
0.22 -
No
0/33
No
Max Detect :< Residential PRG
Eth lbenzene
5/33
0.00034
11
103SB-8
190
No
0/33
No
Max Detect < Residential PRG
Methyl.Tertiary Butyl
Ether
5/19
0.0014
0.014-, .
IW2
17
No...
0/19
No.
Max Detect .< Residential PRG
Methylene Chloride
9/32
0.00067
' 0.0016 .
MW49
9.1_
No..
0/32
No
Max Detect <Residential PRG
Styrene
.1/33.
0.35
0.35
4PH40
440.
No
0/33
No
Max Detect <Residential PRG
Toluene
8/33
0.0002
3.7
103S13-8
66
No
0/33 .
No
.Max Detect <Residential PRG
Trichloroethene
2/33
0.002
0.0051
MW 11.:
0.053
No -
0/33
No
Max Detect <Residential PRG
X lenes; total
6/33
0.0006
69
103SB-8
27
Yes
2/33
Yes
Max:Detect > Residential PRG
Semivolatile Organics Cont ounds (m /k )
2-Meth lna hthalene
3/33
0.59
2.1
4PH43
5:6
No
0/33
No
Max Detect < Residential PRG
Acena hthene
2/33
0.1
0.16
103SB-8
370
No
0/33
No
Max Detect < Residential PRG
Anthracene
1/32
0.12.:
0.12
.103SB-8
2,200
No
0/32
No
Max Detect <Residential PRG
Benz(a)anthracene
1/33
0.021 :
0.021
4PH40.
0.62
No.
0/33
No .
-Max Detect <Residential PRG ..
Benzo(a) 'rene
1/32
0.019
0.019
4PH40
0.062
No
0/32
No
Max Detect < Residential PRG
Berizo(b)fluoranthene
1/32
0.033
0.033
4PH40
0.62
No
0/32,
No
Max Detect < Residential 'PRG .
Bis 2-eth ]hex 1 hthalate
6/33
0.031"
0.067
4PH46
35 ...
No
0/33
No
-Max Detect < Residential PRG
Ch sene
1/33 _
0.028 : -
0.028
4PH40.
62 - . -
No
0/33
No
G
Max Detect <Residential PR.. .
Di-N-bu 1 hthalate
3/33 .
0.021
0.048
MW36
610
No'
0/33
No
Max Detect < Residential PRG.
Dili6nzofuran
1/33
0.091 - '
0.091
4PH43 .-
15 ...
No,
0/33.•
No
Max Detect < Residential PRG
Fluorarithene
1/33
0.048
0.048
4PH40.
230 ' ..
No.
0/33..
No
Max Detect < Residential PRG
Fluorene
2/33
0:18
0.21
103SB-8
270
No.
0/33
No
Max Detect <.Residential PRG
Naphthalene
3/33
0.073 .
0.26.
4PH43 . -
5.6
No .
0/33.
No
Max Detect <.Residential PRG
Phenarithrene
3/33-
0.031.
0.45-
103SB-8
230
No
0/33
. No'
Max Detect <-ResidentialPRG-
Pyrene
3/33 ..
0.038
0.062
103SB=8
230.
No
0/33 ..
No
Max Detect <Residential PRG . .
EPA = U. S. Environmental Protection Agency. FFW = Preliminary. remeoiation goal ritiwrL..= riuman neaim consatuem of Potenuat cu„ccm. o winU - uUuu waaLc.
maiiagement,unit.

TnhlP 3_2_ Rnmmnry Rtntictive nf.V(l(":c l)PtP.etP.d in Grneandwnter- 4;%ATWT 163.
Analyte
Results
>Detection
Limit
:Minimum
Detect
Maximum
Detect.
. Average
Result
95%
UCL
of
Mean
Station
at Max
EPA
Region 9
Tap
WaterYRG
Detects
>PRG.
Federal
MCL
Detects
>MCL
NC
Groundwater
Standard 2L
or IMAAC
DdectO-
NC GW
COPC?
Justification
Volatile Organic Com ounds(Ao L) not associated with petroleum roducts
Acetone
6/103
7.5
3130
59.2
1.12
MW11
550
2/103
No MCL
700
1/103
No
Isolated high detection not
repeated
2-Butanone
1/103
2.6
2.6
14.5
. 24.3
MW33
700
0/103-
No MCL
4200
0/103
No
Max Detect < Risk Criteria
Carbon Disulfide
1/103
0.2.
0.2
1.53
2.5 -
MW21
100
0/103
No MCL
700
0/103
No
Max Detect < Risk Criteria
Chlorobenzene
4/103
1
3
1.58
2.55
MW17 .
11
0/103
100
0/103
50
0/103
No
Max Detect <Risk Criteria
Chloroform
74/103
0.2
82
2.58
4.17
MW22
0.17
741103 .
100
0/103
70
1/103-
Yes
Max Detect- PRG/NC
Chloromethane
10/103
2.9
6.9
2.09
3.06
MW6
16
0/103
No MCL
2.6
10/103
Yes
Max Detect - NC
Dibromochloromethane
1/103
0.38
0.38
1.54
2.51
MW35
0.13
1/103
100
0/103
0.41
0/103
No
Max Detect <NC/MCL
1 2-Dichloroethene "
6/60
1 0.48
13.
2.77
4.44
MW41
6.1
1/60
70
0/60
100
0/60
No
Max Detect < NC/MCL-
cis- 1,2-Dichloroethene
4/79
0.2
0.58- ..
0.458
-0.478
MW40 .
6.1
0/79 '.
70
0/79
70
0/79
No
Max"Detect<Risk Criteria
trans-1,2-Dichl6roethene
2/79
0.2
0.4
0.453
0.476
MW3
12
0/79
16o
0/79
70
0/79-
No _
Max Detect z Risk Criteria
Methylene Chloride . .
7/103
0.94
3.5:
1.83 -
2.8
MW32 "
4.3'
0/103
5
-0/103
4.6
0/103
No
Max Detect < Risk Criteria
4-Methyl-2-pentanone
1/103
9.3
9.3
13.6
23.4
MW7
200
0/103
No MCL
No
NCGW
No
Max Detect < Risk Criteria
Styrene
1/103
8.4
8.4"
1.61
2.59
MW22
160
0/103
100
0/103
100
0/103
No
Max Detect <Risk Criteria
Tetrachloroethane
85/103
0.71
660
101
126
MW23
0.055
85/103
No MCL
. 0.17'
85/103
Yes
Max Detect = PRG/NC
Tetrachloroethene
35/103
0.2
3.2
1.78
2.75
MW12
0.1
35/103
1 5
0/103
0.7
20/103
Yes
Max Detect -PRG/NC
1,1,2-Trichloroethane
11/103
0.2
4.
1.63
2.6
MW3
0.2
10/103'
5
0/103
NCGW NoNo
Max Detect < MCL
Trichloroethene
70/103
0.3
78 .
12.8
15.7
IW2
0.028
70/103
5
45/103
2.8
54/103
Yes
Max Detect
-PRG/MCL/NC "
Volatile Organic Com ounds ( L associated with petroleum products
Benzene
15/103
0.2
300
- 8
13.9
MW22
0.35
14/103
5,
8/103
1-
10/103.
No
VOCs associated with
Eth (benzene .'.
14/103
0.3
1600
56.1
97
MW47
130
6/103
700
4/103 -
550 -.
4/103 '
No
petroleum products are not
MTBE
8/63
7
430
12.9
25.1
MW22
6.2
8/63
No MCL
200
1/63
No
considered HHCOPCs for
Toluene
- 14/103
0.2
940
35.3
60.6
MW47
72'
6/103
1000
0/103
1000
0/103
No
SWIVIU 103 because they are
Xylenies, total
21/103
0.4
10000
361
618
MW47
21
11/103
10000
0/103
530
6/103
No
regulated under NC UST
regulations
1BOId indicates HHCOPC.. COPC = Constituent -of potential -concern._
EPA ,= U.S.. Environmental Protection Agency. GW = Groundwater..
HHCOPC = Human health constituent of potential concern. IMAC = Interim maximum acceptable concentration.
MCL = Maximum contaminant level. MTBE = Methyl tert butyl ether.
NC = North Carolina... PRG = Preliminary remediation goal.
SWMU = Solid waste management unit. UCL = Upper confidence limit. =
VOC =.Volatile organic compound.

EPA
Results
Region
NC GW
>
Station
. 95% ".
" 9 Tape..
Standard
Detect:'
Min.
Max.
at.
Average"
" UCL of,
Water.'
. Detects.
Federal
Detects "
.2L or
Detects> .
.
Anal te.
Limit.-
Detect.
Detect
Max: "
Result .
" Mean
"' PRG .
>PRG
MCL...
>MCL
IMAC.
NCGW
COPC?
Justification
SendvolatileOrganics Conr ounds
( "YL) not associated with etroleuni
roducts
Bis(2--
12/58
1"
5.6
MW.7
1.65 : "
1.97
4.8.6
.1/58
6
0/58
2.5 ...
2/58
No
Common lab
etliylhexyl)phthalate
contaminant;
isolated "high"
detections. are not
significant
Diethyl phthalate
3/58
L4 ".
2.6
MW34
3.68
4.12
2900 nc
0/58
NOMCL
5000
0158 .
No
Max Detect < Risk.'
Criteria.
2,4=Dirriethylphenol
1155
4.3
4.3
MW22
3:88
4.27.
73 nc
0/55
NoMCL
140
.0/55
No
Max Detect < Risk
Criteria .
Di-n-butyl-phthalate
1/58.
1.1
1.1
MW 11
2:31
2.62
360'nc
0/58
NoMCL.
700
0/58
No
Max Detect < Risk
Criteria
3+4-Methylphenol
1150
1.5
1.5
- 'MW7
6.94..
. 7.97
18 ne,k
0150
NoMCL
3.5
0150
No
Max Detect < Risk
Criteria
Sentivolatile Organics "Conr ounds
/L associated withpetroleum prodircts
2-Meth Ina hthalene
4/58
1.9
76
MW22.
4.37
7.25
0'.62 nc
_ 4/58
NoMCL .
14
3/58 "
No
SVOCs associated
with petroleum
product are not
Naphthalene
3/58'
103..
160
MW22
8.57
15.2
0.62 nc
3/58
NoMCL-:
21 _
3/58
No
Phenanthrene
2/58
0.7
1.6
MW 11
1.71
2.02
18 1 nc
0/58
NoMCL'
210
0/58
No
Considered,
HHCOPCs for
SWMU 103 because
they are regulated
under NC UST
regulations
ADoes not include site -specific background wells (MW26 or MW27) or monitoring wells installed "around former heating -oil UST (MW69344C, MW43, MW44; MW45 or MW46). .
Bold, indicates concentration above screening criteria: COPC = Constituent of potential concern. " EPA = U. S. "Environmental Protection"Agency.
GW'= Groundwater. IMAC = Interim_ maximum acceptable concentration: MCL = Maximum contaminant level..'.
NC = North Carolina: PRG"= Preliminary remediation -goal. SWMU = Solid waste management unit. '
UCL = Upper confidence limit.

Table 3-4: Historical groundwater VOC data support reductive dechlorination in the
SWMU 103 source area
Compound
Concentration
/L
MW7
Shallow
Well
MW6
Deep Well
MW22
Shallow
Well
MW23
Deep Well
1,1,2,2-Tetrachlorethane
30J
390
29J
660
Tetrachlorethene
ND
2.4
ND
2.3
Trichloroethene
ND
55
14J
69
cis 1,2-dichloroethene
ND
ND
ND
ND
Vinyl chloride
ND
ND
ND
ND
BTEX
213
ND
10,880
ND
Notes: ND = non -detect

Table 3-5: Vapor Intrusion Tier II Screening Summary
Target Groundwater
Target
Concentration
Indoor. Air
Target Deep (> 5
Corresponding to
Concentratio
ft bgs) Soil Gas
Target Indoor Air
n to Satisfy
Concentration
Concentration Where
Both the
Corresponding to
Soil Gas to Indoor
Prescribed
Target Indoor Air
Air Attenuation
Risk Level
Concentration
Factor = 0.001 and
and the
Measured
Where the Soil
Partitioning Across
Measured
Target
Crawlspace Air
Gas to Indoor Air
Measured Deep (8 —
the Water Table
Groundwater
Hazard Index
Concentration
Attenuation
10 ft bgs) Soil Gas
Obeys Henry's Law
Concentratio
Chemical
Risk Level
by
by
Factor = 0.01
Concentration by
n
R=10-5,HI=1
Acetone
6
R=10',HI=1
f 50
_< 5.88
15,000
5114
220,000
:546
R = 10"5, HI = 1
0.22
22
Chloroform
ND
<_ 5.78
80
<_ 0.74
R = 10 HI = 1
0.022
2.2
Dibromochloro-
R = 10-5 HI = 1
0.12
12
32
methane
ND
ND
5 0.38
R = 10-6 HI = 1
0.012
1.2
3 2
Cis 1,2-
R = 10, HI = 1
8.8
ND
880
ND
210
<_ 0.54
R = 10-6, HI = 1
Dichloroethene
1,1,2,2-
R = 10-5 HI = 1
0..061
ND
6.1
ND
30
Trichloroethane
(MDL = 0.034
(0.034 _< MDL <_ 0.34)
< 310
—
R = 10"6, HI = 1
0.0061
0.61
3.0
R = 10-5 HI = 1
1.2
120
11
Tetrachlorethene
0.192
_< 1.13
< 2
R = 10-6 HI = 1
0.12
12
5
R = 10-5, HI = 1
0.041
ND
.1
4.1
ND
5
5 29
R = 10 6, HI = 1
0.0041
0.41
Note: bgs = below ground surface; ft.= feet; HI = Hazard Index; MDL = Minimum Detection Level; ND = Non -detect; ppbv = parts per billion (volume); R =
Risk Level; µg/L = micrograms per liter

Results
95%.
Detect,
Min._
Max.-
Average
' 1(JCL of
Station
Anal to
Limit
Detect.
Detect:
Result
Mean
at Max:
NC SWS
. HIiCOPC?a
Justification:
Volatile Organic Compounds
(µg/L) . .
1 1 -Tetrachloroethane
6/6
1.4-
12
4.9
8.2
SWS10.
4
Yes
Max. detect. > NC. SWS
Chloromethane -
3/6
0.6
3 . -
1.2
2.0. _ .
SWS6..
96 ..
No ..
Max. detect: <NC SWS. ".
Tetrachloroethene
4/6
0:2 .
0:5
0:38
0:49
SWS6.
3:3
No
Max: detect: <NC SWS-
toluene
2/6
0.4
0.1
0.52
0.60
SWS10
11- _
No
Max. detect:.<NC SWS
Trichloroethene
4/6
0.2
0.6
0.43
0.55
SWS10
30.
No
Max. detect. <NC SWS
cis7-1,2-Di6hloroethene
2/6 .'.
.0.2-.
.. 0.4,
0.43 :=.
- 0:53 ...1.
SWS4. 'I
4,900..
. No
My x_detect. <NC SWS ...
Ma1hrnnk Trlhutarv. .. -
11 2 2-Tetrachloroethane
. 5/6
0.7
59.6
21 _ .
40
SWS14
4
Yes
Max. detect. >'NC SWS
Acetone
1/6
11
11
15
24 '.
SWS2.
2,000
No
Max. detect. <.NC SWS
Chloroform
1/6
0.2
0.2
0.70
0.98
SWSH
5.7
No
Max. detect. <.NC.SWS
Chloromethane
2/6
1.9
2.9
1A . -
.2.1
SWS11
96
No
Max. detect: <NC SWS
Trichloroethene
3/6
1.6 '
5.9
2:0
3.6
SWS14.
30
No
Max: detect:.-5 NC SWS .
Vinyl chloride
1/6
0.4
0.4
0.90 .
1.1
SWS2.
2A
No. .
Max.. detect. <NC SWS
cis-1,2-Dichloroethene
1/6
0.7
0.7
078
0.98
S.WS2
4,900
No
.Max. detect. <NC SWS
trans-.1,2-Dichloroethene
1/6
0.4
0.4.
0.73.
- 0.97,
SWS2
10,000
No
Max. detect. <NC SWS'
This table summarizes data from the REI and.was-updated only to reflect the most. current North Carolina surface water standards. March 2006 surface water sampling results are
summarized in Appendix F but do not change conclusions.about surface water HHCOPCs: Constituents whose.maximum detected concentrations.are larger than'their NC SWSs.
are surface water HHCOPCs;,constituents without NC.SWSs are also retained as surface.water HHCOPCs. NC = North Carolina. HHCOPC Human health constituent, of
potential, concern. SWS = Surface water'standard. UCL =Upper confidence limit. Bold indicates HHCOPCs. Italics indicates where detection limits resulted in'average values
greater than the maximum detect value.

Tahla 1-7- rmmnarican of CRC' in Cnhenrfaee Cnil to Nnrth. r..arnlinn CST:c_ SWMiT 1113
Anal te.
Results >.
Detection_
Limit
Minimum
Detect .
Maximu
m Detect :
Station
at Max.
NC
HWS
SSL
Mai
Detect•
>NC. SSL
Detects
> SSL:
CMCOPC?
Justification
Volatile Or anic Cout ounds rn lk
11-Tetrachloroethane
2/33
0:0029
0.023
103894
0.00095
Yes .
2/33 .
Yes
Max. detect>=NC SSL
2-Butanone
7/33
010017
0.078
4PH41
0.692
No
0/33
No
Max: detect <NC SSL;
4-Meth l-2- entanone.
5/33
0.0014 -
0.0027:-
4P942
2.28.
No..
0/33'
No
Max: detect<NC SSL
Acetone
17/33 :
0:0056
0.079-
MW-23
2.911
No.:
0%33
-No. :
Max: detect <NC SSL
Benzene
3/33 .:
OA001
.0.636
4PH40
0.00562
Yes ..
1/33 :.
Yes.
Max: detect >=NC SSL
Carbon Disulfide
6/33 .
.0.0019
0.0057 .
4PH43 ..
4.94 .
No :.
0%33 .'...
No ..
Max: detect < NCSSL
Chloroform .
4/33 ..
0'.00051 -
: 0.044 .
4PH41
0.00101
- Yes
1/33'
Yes..
Mai: detect >=NC SSL
Eth lbenzene-
5/33 - .
'0.00034
: 11
.103SB-8-.
0.241.
Yes- :
.2/33
Yes-
Max: detect>=NC SSL
Methyl Tertiary Butyl Ether
MTBE
5/19
0.0014
0.014
IW-2
None
No SSL
No
No. SSL
Meth lene Chloride
9/32
0.00067
0.0016
MW-49
0.022
No
0/32
No ...
Max: detect <NC SSL
S rene
1133
0.35
0.35
4PH40
2.24
No
0/33
No
Max. detect <NC SSL
Toluene
8/33
0.0002
3.7
103SB-8
7.27
No
0/33
No.
Max..detect <NC SSL
Trichloroethene
2/33-
0.'002
0.0051
MW-11
0.0183
No
0/33
No.
Max. detect <NC SSL
X lens total
6/33'
0.0006
69
103SB68
4.96
Yes
2/33-
Yes.
Max. detect>=NC SSL
Seneivoladle Organics Compounds sn: 7k )
2-Meth Ina hthalene
3/33.
0.59
2.1 .
4PH43
3.45
No
0/33
No .
Max. detect <NC SSL
Acena hthene
2/33'
0.1
0.16.
103SB-8
8.16
No
0/33 -
No
Max: detect <NC SSL
Anthracene
1/32.
0.12
0.12.
103SB-8 -
... 995.
No
0/32 .
No
Max. detect <NC SSL
Benz a anthracene
1/33..
0.021 .:
0:021
4PH40.
- 0.358
No .--..
:0/33.
No
Max. detect <NC SSL
13enzo a rene
.1/32.'-
0.019
0.019
4PH40.
0.0911..
No
0/32
No -
Max: detect'<NC SSL
Benzo b fluoranthene
1/32
0.033
0.033
4PH40
1.16
No
0/32.
No
Max: detect'<NC SSL
Bis 2-eth the I hthalate
6/33 . -
0.031
0.067,
4PH46
6.67
No
0/33
No
Max: detect <NC SSL
Chrysdrie
1/33 ,
0.028 .
-0.028.
- 4PH40.
39.8
No.0/33'.
No'- . -.
: Max: detect<NC SSL
Di-X-butyl phthalate
3/33 .
0.021
0.048.
MW-36 '.
24.8
No .
-0/33
No
Max. detect <NC SSL
Dibenzofuran
1/33:.
0.091
0..091.
4PH43
4.66
No .
0/33 . -
No
Max. detect <NC SSL

Table 3-7. Comparison of Site -Related Contaminant in Subsurface Soil to North Carolina SSLs, SWA U 103 (continued)
Anal to
Results >
Detection
Limit
Minimum
Detect
Maximum
Detect
Station
at Max.
NC
HWS
SSL
Max
Detect
>NC SSL
Detects
> SSL
CMCOPC
?
Justification
Fluoranthene
1/33
0.048
0.048
4PH40
276
No
0/33
No
Max. detect <NC SSL
Fluorene
2/33
0.18
0.21
103SB-8
44.3
No
0/33
No
Max. detect <NC SSL
Naphthalene
3/33
0.073
0.26
4PH43
0.585
No
0/33
No
Max. detect <NC SSL
Phenanthrene
3/33
0.031
0.45
103SB-8
59.6
No
0/33
No
Max. detect <NC SSL
Pyrene
3/33
0.038
0.062
103SB-8
286
No
0/33
No
Max. detect <NC SSL
CMCOPC = Contaminant migration of contaminant of potential concern.
HWS = Hazardous waste section.
NC = North Carolina.
SRC = Site -related constituent.
SSL = Soil screening level.
SWMU = Solid waste management unit.

Table 3-8. Natural Attenuation Time to
Multiple Target Groundwater Concentrations at SWMU 103
Target
Concentration
Total Mass
Percentage of
total Mass %
MNA (years)
Baseline a
0.17 b
77.56
100
60
1.0 c
77.53
99.96
44
4 d
77.29
99.64
33
5 e
77.18
99.50
30
a. Assumed biological half-life (tin) = 7.9 years. This is not site -specific, but it is based on conservative literature values;
therefore, the results should be used with caution.
b. Target concentration equals the North Carolina 2L standard for groundwater.
c. Target concentration equals= the analytical detection level.
d. Target concentration equals the North Carolina surface water standard for 1,1,2,2-tetrachloroethane for surface water.
e. Target concentration equals the groundwater concentration of 1,1,2,2-tetrachloroethane being detected in deep surficial
groundwater at the background location (MW27).
r��

Table 3-9
HRl^nPC'c in Grnnndwater and Surface Water at SWMU 103
Groundwater
Surface Water
Anal to
Max. Cone.
in GW
GW
Location
Anal to
Max. Cone. in
Beaver Creek
Surface Water
Beaver Creek
Surface Water
Location
Max. Cone. in the
Holbrook Tributary
Surface Water
Holbrook Tributary
Surface Water Location
Volatile Organic Com ounds /L
Chloroform
82
MW22
1,1,2,2
Tetrachloroethane
12
SWS10
59.6
SWS14
Chloromethane
6.9
MW6
1,1,2,2
Tetrachloroethane
660
MW23
Tetrachloroethene
3.2
MW12
Trichloroethene
78
IW2
Conc. = Concentration.
GW = Groundwater.
HHCOPC = Human health constituent of potential concern.
Max. = Maximum.
SWMU = Solid waste management unit.

IV/ i
Table 3-10. Recommended RGOs for Potable Use of Groundwater. SWMU 103
Maximum
North
Concentration
Carolina 2L
in
or U"C
Recommended
Anal to
Groundwater
Standard
RGO
COC
Justification
Volatile Organic Compounds (uvIL)
Chloroform
82
70
70
Yes
Max. detect > RGO
Chloromethane
6.9
2.6
2.6
Yes
Max. detect > RGO
Tetrachloroethene
3.2
0.7
0.7
Yes
Max. detect > RGO
1 1 -Tetrachloroethane
660
0.17
0.17
Yes
Max. detect > RGO
Trichloroethene
78
2.8
2.8
Yes
Max. detect > RGO
COC = Constituent of concern.
IMAC =Interim maximum acceptable concentration.
RGO =Remedial goal option.
SWMU = Solid waste management unit.
Bold indicates COC requiring corrective action.
M

Tahl a '2-1 I ilptPrminatinn of [' r, and Reenmmended RGOs for Surface Water. SWMU 103
Beaver
Holbrook
Maximum
Creek
Holbrook
Tributary
Detect in
Surface
Tributary
Surface
Beaver
Water
Surface
Water
Recommended
Analyte
Creek
Location
Water
Location
NCSWS
RGO
COC
Justification
Volatile Organic Compounds (µg/L)
1,1,2,2-
Tetrachloroethane
12
SWS10
59.6
SWS14
4
4
Yes
Max. detect> RGO
COC = Constituent of concern.
NC = North Carolina.
ND = Not detected
RGO = Remedial goal option.
SWMU = Solid waste management unit.
SWS = Surface water standard.
Bold indicates final COC.

r 1
Table 4-1
Recommended Remedial Levels for COCs in Groundwater and Surface Water at SWAM 103
Anal to
Maximum
Concentration
Recommended
Remedial Level
Groundwater
Volatile Organic Compounds (µg/L)
Chloroform
82
70
Chloromethane
6.9
2.6
1,1,2,2-Tetrachloroethane
660
0.17
Tetrachloroethene
3.2
0.7
Trichloroethene
78
2.8
Surface Water
Volatile Organic Compounds (µg/L)
1,1,2,2-Tetrachloroethane 1 59.6 4
COC --'Constituent of concern.
SWMU = Solid waste management unit.
��1

Table 5-1. Evaluation of Corrective Action Technologies/Process Options for Groundwater, SWMU 103
Action
Description
Effectiveness
Implementability
Cost
Further
Evaluation
No Action
The no action option provides
This alternative would not
This alternative is implementable
There would be no
Eliminated
a baseline against which other
address remedial response
because no actions are involved.
cost associated
from further
process options/technologies
objectives for the site. It
with the no action
evaluation
can be compared. Groundwater
would not provide protection
alternative
and surface water would be left
of human health because there
"as is" without any removal,
would not be sufficient
treatment or other mitigating
controls to prevent inadvertent
actions to reduce existing or
human exposure to
potential future risks to human
contaminated water.
health and the environment No
monitoring would be
performed to assess the future
levels of contamination or
trends.
Institutional
Land and groundwater -use
Land- and groundwater -use
Institutional controls are
The cost would
Retained
controls
restrictions reduce hazards by
restrictions would effective and
implementable. The property is
be low.
for further
limiting access to contaminated
provide long-term reliability to
part of a federal installation and
evaluation.
areas or media. Access can
prevent inadvertent human
is expected to be retained by the
also be physically restricted
exposure to groundwater. Use
federal government for the
through use of barriers
restrictions will prevent use of
indefinite future. As such, land -
(fences). Land- and
contaminated groundwater for
and groundwater -use restrictions
groundwater -use restrictions
drinking water or irrigation.
would be implemented as
are implemented through the
Land- and groundwater -use
specified in the facility BMP.
BMP.
restrictions would be
documented and implemented
Existing fencing and warning
at Fort Bragg through the
signs could be repaired/upgraded
BMP.
and new fencing could be
installed to prevent contact with
surface water.

Table 5-1. Evaluation of Corrective Action Technologies/Process Options for Groundwater, SWMU 103 (Continued)
Action
Description
Effectiveness
Implementability
Cost
Further
Evaluation
MNA
MNA is the reduction in the
This technology has been
Technologies and resources are
MNA is relatively
Retained for
concentration and mass of
proven effective and provides
readily available for collection
inexpensive
further
contaminants through naturally
long-term reliability with
and analysis of groundwater. A
evaluation
occurring processes.
respect to VOCs.
network of groundwater
monitoring wells presently exists
Monitoring would provide an
at the site.
effective method for evaluating
the variation of constituent
concentrations in groundwater
over time
Phytoremediation
Use of plants to remove,
This emerging technology has
Resources are readily available
Phytoremediation
Eliminated
degrade, or contain chemical
been proven effective for
for the installation of a
is relatively
from further
contaminants found in soil and
chlorinated compounds;
phytoremediation network.
inexpensive
evaluation
groundwater
however, the hydraulic uptake
Existing hardwoods limit the
is drastically reduced during
number of phreatophytic trees
winter months when the
that could be emplaced at the site.
plant/trees are dormant.
Phytoremediation would not be
effective for the entire plume
because the depth of
contamination in portions of
the plume is deeper than that
which phytoremediation has
been found to be effective.

Table 5-1..Evaluation of Corrective Action Technologies/Process Options for Groundwater, SWAIU 103 (Continued)
Action
Description
Effectiveness
hnplementability
Cost
Further
Evaluation
PRB
Trenches excavated
PRBs using zero-valent iron is
PRBs at the SWMU 103 will be
PRBs can be
Eliminated
perpendicular to the
a passive in -situ treatment that
difficult to implement due to the
relatively
from further
groundwater flow path and
has been effective in treating
large size of the plume and the
expensive due to
evaluation
backfilled with a reactive
chlorinated solvents
numerous underground utilities in
extreme
medium. As the contaminants
contamination in groundwater.
the area. It would difficult or
fluctuations in the
pass through the walls, the
However, due to the size of the
impossible not to impact
price of iron.
contaminants are removed
groundwater plume and the
Holbrook Elementary School
depth of contamination on
during construction of a PRB.
certain areas, PRBs alone
would not be effective for
entire plume treatment
Pumping and
A series of groundwater
Pump -and -treat is an effective
Pump -and -treat will be difficult
Pump -and -treat has
Retained for
Ex -Situ Treatment
extraction wells manifolded
method for treating limited
to implement at the SWMU 103
a high cost and
further
of Groundwater
together, or a series of
plumes. Activated carbon and
site due to the large size of the
long term
evaluation
subsurface drains, remove
air stripping treatment
plume and the large number of
operational costs,
groundwater for above -ground
technologies are effective for
extraction wells required. A
but a system
treatment
treating chlorinated solvents in
limited system, to intercept and
designed to protect
groundwater
treat contaminated groundwater
surface water could
prior to its discharge to surface
have a limited life
water, may be implementable,
cycle.
but will be logistically
challenging to install around the
school.

Table 5-1. Evaluation of Corrective Action Technologies/Process Options for Groundwater, SWMU 103 (Continued)
Action
Description
Effectiveness
Implementability
Cost
Further
Evaluation
Air Sparging
Air is injected into the
Air sparging has been found
Air sparging will be difficult to
Air sparging has a
Eliminated
groundwater through injection
effective for removing VOCs
implement at the SWMU 103 site
medium to high
from further
wells where the air then
in groundwater. Containment
due to the large size of the plume
cost and medium
evaluation
volatilizes and strips VOCs
and capture of the vapors is the
and the large number of
term operational
from the groundwater
problematic around structures.
extraction wells required for
costs
Containment and capture of the
vapor containment/control. In
vapors can be effected by
addition the manifolding and
heterogeneities in the
piping of the wells to a central
subsurface that create
treatment system would prove
preferential flow paths for
difficult
vapors (i.e., highly permeable
sand lenses, clay lenses, buried
utilities). Some uncertainty is
associated with potential
mobilization (short-circuiting)
of vapors potentially causing
increased vapor intrusion in
buildings
In -Situ Chemical
An oxidant and catalyst is
Chemical oxidation is not very
Multiple injections would be
Costs for chemical
Eliminated
Oxidation (ISCO)
injected into the groundwater
effective at remediation of
required given the relatively low
oxidation are
from further
through injection wells to
chlorinated alkanes. The
concentration in groundwater.
relatively high
evaluation
degrade the chlorinated
predominant contaminant at
Typically, chemical oxidation is
compounds.
the SWMU 103 site is 1,1,2,2-
used to treat higher concentrated
tetrachloroethane, a chlorinated
source areas rather than low-
alkane.
concentration plumes. Higher
quantities and longer residence
times would be required to treat
chlorinated-alkanecontaminated
groundwater

Table 5-1. Evaluation of Corrective Action Technologies/Process Options for Groundwater, SWMU 103 (Continued)
Action
Description
Effectiveness
Implementability
Cost
Further
Evaluation
Enhanced
Anaerobic microorganisms
Proven effective for
Readily implementable at the
Costs for reductive
Retained for
Bioremediation
substitute hydrogen for
remediation of chlorinated
SWMU 103 by injecting carbon
dechlorination are
further
using Anaerobic
chlorine on the chlorinated
compounds in anaerobic
substrate (vegetable oil) in the
moderate
evaluation
Reductive
solvent
environments. The SWMU 103
source area near the interface of
Dechlorination
site exhibits highly aerobic
the Cape Fear clay formation to
conditions that will have to be
reduce VOC flux to groundwater.
overcome for this approach to
be successful.
Enhanced
Aerobic blend of bacteria
Bench scale and pilot study
Enhanced bioremediation using
Costs for aerobic
Eliminated
Bioremediation
specifically for remediation of
tests were performed to
cometabolic mechanism is
bacteria, repeated
from further
Using Cometabolic
chlorinated solvent
evaluate the effectiveness of
implementable at the SWMU 103
carbon substrate
evaluation
Mechanism
contamination is injected into
the cometabolic mechanism
site. Aerobic conditions need to
and oxygen..,
the groundwater through
using a representative aerobic
be maintained; therefore,
injections are
injection wells. Aerobic
bacteria and the substrate
additional oxygen must be added
relatively high
bacteria have been shown to
dextrose at the conditions
degrade CVOCs through
found at the SWMU 103 site.
cometabolic pathway that
Although some biodegradation
requires a primary substrate
was observed, concentrations
(dextrose) under aerobic
rapidly rebounded. Soluble
conditions
substrates such as dextrose will
not remain at contaminant
source, repeated injections
would be required.
Monitoring
Monitoring of groundwater,
Monitoring would provide an
Technologies and resources are
Monitoring is
Retained for
and soil gas, could be
effective method for, evaluating
readily available for collection
relatively
remediation
performed to provide
the variation of constituent
and analysis of groundwater, and
inexpensive, but
monitoring
information concerning trends
concentrations in groundwater
soil gas samples
costs add up over
combined
associated with the
and soil gas over time and the
time.
with other
concentrations of constituents
performance of a corrective
technologies
over time
action

Table 5-2
'Pualnatinn of ('.nrrPetive Action Technnlnaiec/Prncecc nntians far Surface Water. SWIVIU 103
Action
Description
Effectiveness
Implementability
Cost
Further
Evaluation
No Action
The no action option provides a
This alternative would not address
This alternative is
There would be
Eliminated
baseline against which other process
remedial response objectives for
implementable because no
no cost
from further
options/technologies can be
the site. It would not provide
actions are involved.
associated with
evaluation
compared. Surface water would be
protection of human health
the no action
left "as is" without any removal,
because there would not be
alternative
treatment or other mitigating actions
sufficient controls to prevent
to reduce existing or potential future
inadvertent human exposure to
risks to human health and the
contaminated surface water.
environment No monitoring would be
performed to assess the future levels
of contamination or trends.
Institutional
Institutional controls consisting of
Land -use restrictions would be
Institutional controls would
The cost would
Retained for
controls
land -use controls and administrative
partially effective with respect to
be readily implementable.
be low
further
controls would be instituted. Land-
preventing inadvertent human
The property will remain
evaluation
use restrictions would reduce
exposure to surface waters.
under federal ownership for
potential hazards by limiting
Fencing would prevent contact of
the foreseeable future.
inadvertent human exposure to
surface water to nearby residents
Enforcement through the
contaminated surface water.
and children. The BMP is an
BMP is implementable
Contaminated surface water is
effective tool for ensuring
because procedures and
located near Holbrook Elementary
establishment of land -use
policies are in place at Fort
School and residential areas;
restrictions because requirements
Bragg to facilitate its
therefore, institutional controls will
of the BMP are enforced by Fort
implementation
need to include physical controls (i.e.,
Bragg in accordance with written
fencing) and administrative controls
policies and procedures.
Physical barriers could also
(i.e., signs) to prevent potential
be easily implemented, if
exposure to residents, specifically
Warning signs would inform
necessary
children. Landuse restrictions would
persons of the potential
be enforced through the BMP
contaminated surface water along
Beaver Creek and Holbrook
tributary, thus reducing potential
exposure and risk to humans

Table 5-2 (Continued)
Evaluation of Corrective Action Technoloeies/Process ODtions for Surface Water. SWMU 103
Action
Description
Effectiveness
Implementability
Cost
Further
Evaluation
Ex -situ
A variety of ex -situ water treatment
Activated carbon and air stripping
Variable flow (e.g.,
High, due to
Not retained
Treatment:
technologies are available to treat
would be effective at treating
stormwater versus dry
uncertainty in
due to
Activated
VOCs in surface water. The most
VOCs in surface water
summer conditions, etc) in
design and O&M
implement -
Carbon and Air
applicable and representative of
Holbrook tributary and
costs
ability and high
Stripping
potential technologies are air
quality of surface water (i.e.,
cost
stripping and activated carbon.
particulates in surface water
Surface water in the Holbrook
are uncertainties in the
tributary would be diverted to
implementability of the ex -
treatment processes where package
situ units). Units may require
treatment unit would treat the water.
an equalization basin to
O&M would be required for either
equalize variable flows and
system
pretreatment to remove
solids. High natural organic
carbon in surface water (> 3
ppm) will consume activated
carbon capacity. No utilities
are present at the location,
thus the treatment units
would likely be installed.
O&M will be required
In -situ
In -stream aeration/volatilization
Level of effectiveness varies for
Most aeration/volatilization
Simple systems
Step -wise
Technologies and
technologies for removing VOCs in
the different technologies. Some
techniques are implementable
have low cost.
implementation
Process Options:
surface water are low -technology
(boulders, drop structures) are
in Holbrook tributary
Costs
of in -stream
Aeration /
systems that facilitate gas transfer,
dependent on flow and elevation
progressively
aeration/
Volatilization
thus resulting in the volatilization of
change in the Holbrook tributary.
increase as more
volatilization
the VOCs to the atmosphere. These
active systems
systems are
systems can range from simply
(air sparging,
retained for
installing small boulders in the
fountains) are
further
streambed to cause increased
employed.
evaluation.
agitation, to installing active systems
such as air sparging or fountains to
more aggressively facilitate gas
transfer. Prudent approach would be
step -wise implementation starting

Table 5-2 (Continued)
Evaluation of Corrective Action Technologies/Process Options for Surface Water, SWMU 103
Action
Description
Effectiveness
Implementability
Cost
Further
Evaluation
with simple systems and progressing
to more -active systems until a
technology can be found that will
meet surface water standards.
In -situ
Wetlands would use native wetland
Literature indicates that
A constructed wetlands
Constructed
Not retained
Technologies and
plants to remove, degrade, or adsorb
applications to date are not
require only standard
wetlands are
due to
Process Options:
chemical VOC contaminants found in
typically used for treatment of
technology to build, however,
relatively
implement -
Constructed
surface water. Native wetland plants
VOCs in surface water. Example
limited space is available
inexpensive
ability
Wetlands
would be planted in either a
of applications include treated
near the confluence of the
concerns and
submerged or overflow system
sewage wastewater, stormwater,
Holbrook tributary and
uncertainty of
located within the existing channel of
acid mine drainage, and
Beaver Creek may be
its application
the Holbrook tributary.
agricultural runoff. Theoretically,
limiting
wetlands would be as successful
for the treatment of VOCs.
However, to date, wetland plants
have not been specifically
evaluated for VOC removal
In -situ
Biological mats, containing organic
This technology has been used
Biological mats could be
Moderate
Not retained
Technologies and
material and bacteria capable of
successfully at Aberdeen Proving
installed, but conditions
due to
Process Options:
biodegrading dissolved solvent
Ground for 1,1,2,2-
cannot be maintained to keep
effectiveness
Biological Mats
contaminants, would be placed in the
tetrachloroethane. However, to be
the mats anaerobic.
concerns
stream -bed to treat contaminated
effective, the mats must stay
groundwater as it upwells into
substantially submerged to
surface water.
maintain anaerobic conditions.
Water depths in SWMU 103
streams are too shallow to
maintain anaerobic conditions.
In -situ
Holbrook tributary between
Encasing Holbrook tributary in an
Stream restoration,
Moderate to high
Not retained
Technologies and
Doughtery Road and Beaver Creek
underground pipe may prevent
concreting, or encasement in
due to
Process Options:
would be contoured and either an
contaminated groundwater from
an underground pipe is
effectiveness
Stream
impermeable liner (i.e., clay, HDPE,
intercepting the surface water, but
implementable. A
concerns
Restoration /
concrete, etc.) would be installed or
contaminated groundwater would
topographic survey of
Segregation
Holbrook tributary would be encased
simply be diverted to Beaver
Holbrook tributary and
in a pipe to prevent groundwater
Creek. No net benefit would be
adjacent area would be
from intercepting surface water in the
I achieved.
I needed and stormwater

Table 5-2 (Continued)
Evaluation of Corrective Action Technologies/Process Options for Surface Water, SWMU 103
Action
Description
Effectiveness
Implementability
Cost
Further
Evaluation
Holbrook tributary
requirements would have to
be determined to develop
final design. Less uncertainty
associated with encasement
in pipe, which allows more
usable recreational land in the
area. Fort Bragg DPW
indicated drainage ditches
similar to Holbrook tributary
have been concreted to
prevent erosion
Monitoring
Monitoring of surface water could be
Monitoring would provide an
Technologies and resources
Monitoring is
Retained for
performed to provide information
effective method for evaluating
are readily available for
relatively
remediation
concerning trends associated with the
the variation of constituent
collection and analysis of
inexpensive
monitoring
concentrations of constituents over
concentrations in surface water
surface water samples
combined with
time
over time and the performance of
other
a corrective action
technologies
BMP = Base Management Plan.
DPW = Directorate of Public Works.
HDPE = High -density polyethylene.
O&M = Operations and maintenance.
SWMU = Solid waste management unit.
VOC = Volatile organic compound.

Table 5-3. Cost Comparision of Remedial Alternatives for SWMU 103
Alternative 1: MNA, Engineered Aeration/Volatilization of Surface Water, Institutional
Controls, and Monitoring
Captial Costs:
Mobilization and Plans
$182,000
Remediation (Construction & active operations)
$479,000
$661,000
O&M Costs (monitoring):
Unit Cost
Events
Cost
First Year Monitoring/Reporting
$114,550
1
$114,550
Year 2 - 6 Monitoring/Reporting
$53,500
5
$267,500
Year 7- 16 Monitoring/Reporting
$43,500
29
$1,261,500
Year 17 - 60 Monitoring/Reporting
$32,000
25
$800,000
5 Year Reviews
$16,300
12
$195,600
$2,639,150
Total:
$3,300,150
Alternative 2: Source Area Treatment Using Enhanced Bioremediation, MNA, Engineered
Aeration/Volatilization of Surface Water, Institutional Controls, and
Monitoring
Captial Costs:
Mobilization and Plans
$182,000
Remediation (Construction & active operations)
$779,000
$961,000
O&M Costs (monitoring):
Unit Cost
Events
Cost
First Year Monitoring/Reporting
$114,550
1
$114,550
Year 2 - 6 Monitoring/Reporting
$53,500
5
$267,500
Year 7- 10 Monitoring/Reporting
$43,500
19
$826,500
Year 11 - 60 Monitoring/Reporting
$32,000
35
$1,120,000
5 Year Reviews
$16,300
12
$195,600
$2, 524,150
Total:
$3,485,150
Alternative 3: Source Area Treatment Using Enhanced Bioremediation, MNA, Pump -and -
Treat Contaminated Groundwater to Protect Surface Water, Institutional Controls,
and
Monitoring
Captial Costs:
Mobilization and Plans
$182,000
Remediation (Construction & active operations)
$1,077,950
$1,259,950
O&M Costs (monitoring):
Unit Cost
Events
Cost
First Year Monitoring/Reporting
$114,550
1
$114,550
Year 2 - 6 Monitoring/Reporting
$53,500
5
$267,500
Year 7- 10 Monitoring/Reporting
$43,500
19
$826,500
Year 11 - 60 Monitoring/Reporting
$32,000
35
$1,120,000
5 Year Reviews
$16,300
12
$195,600
$2, 524,150
Total:
$3,784,100

J-
a nced
contaminated
Alternative -I!. MNA, _Engitstitutional
Criterion
Surface.Water; Institution'
Short.? Perm
Low potential of exposure tjtndwater to human
Effectiveness
environment during installal°f the interceptor-
(Workers,
monitoring events. (brook Elementary
Community, and
iciently far enough
I Elementary
Environment)
.�ntation is
iygineered bacteria.
Implementability
Institutional controls and.m'NPDES permits
water)'are readily implemeitund injection
surface water approaches fi Irceptor trenches
concerns.. -; .
Cost
Capital Cost =. $661,000- ..
O&M (monitoring)
Total Cost = $3,300,150 ..
BMP = Base Management Plan. -
COC = Constituent -of concern.
CY = Calendar year.
MNA = Monitored natural attenuation.
UIC = Underground Injection Control.
VOC = Volatile organic compound.

5-4
Groundwater and Surface Water by Evaluation Criteria
Alternative 3: Source Treatment with Enhanced
ent with Enhanced
Bioremediation, MNA, Pump -and -Treat Contaminated
eered Aeration/Volatilization of
Groundwater to Protect Surface Water, Institutional
�ontrols, and Monitoring
Controls, and Monitoring
zal controls (fencing and signs)
Risk reduced through institutional controls (fencing and signs)
nated groundwater and surface
preventing exposure to contaminated groundwater and surface
in will reduce source flux and
water. Enhanced bioremediation will reduce source flux and
in groundwater and eventually
therefore overall concentrations in groundwater and eventually
for removes VOCs in surface water.
surface water. Interceptor trenches will remove and treat
rm overall protection
contaminated groundwater prior to discharge to surface water.
Monitoring and reporting confirm overall protection
)undwater cleanup standards are
Modeling has estimated that groundwater cleanup standards are
om CY 2005. Enhanced
attained by MNA in 60 years from CY 2005. Enhanced
zndwater concentrations and result
bioremediation will reduce groundwater concentrations and
rds in approximately 25 years.
result in meeting surface water standards in approximately 25
on will ensure compliance with
years. Interceptor trenches will protect surface water in the
ation near Knox Street in the
interim.
o presently identified at SWMU 103
No remaining primary source is presently identified at SWMU
iremediation targets the interface of
103 for groundwater. Enhanced bioremediation targets the
ape Fear formation clays, which is
interface of the surficial aquifer with the Cape Fear formation
'groundwater contamination.
clays, which is conceptualized as the source of groundwater
ilso ultimately reduce contamination
contamination. Enhanced bioremediation will also ultimately
ater.
reduce contamination of surface water from groundwater. The
interceptor trenches will protect surface water in the interim.
regulations. UIC permit required
Complies with state and federal regulations. UIC permit
hanced bioremediation. Engineered
required for injection of materials for enhanced bioremediation.
:s from surface water may require a
NPDES permit needed for discharge of treated groundwater to
�orps of Engineers.
surface water.
i
lent on institutional controls
Long-term effectiveness dependent on institutional controls
restricting groundwater use and
implemented through the BMP restricting groundwater use and
-. Groundwater is not presently used
limiting access to surface water. Groundwater is not presently
water monitoring will assure
used or expected to be used. Groundwater monitoring will
are reducing by natural attenuation
assure concentrations in groundwater are reducing by natural
Engineered volatilization will
attenuation and enhanced bioremediation. Interceptor trenches
ter.
will protect surface water until groundwater concentrations are
reduced.
toxicity of COCs in groundwater,
Natural attenuation will reduce toxicity of COCs in
rovide active treatment to decrease
groundwater, and enhanced bioremediation provide active
;lay into the aquifer. Engineered
treatment to decrease the flux of contaminants from clay into the
tream surface water.
aquifer. Interceptor trenches will protect surface water until
groundwater concentrations are reduced.

FIGURES
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Figure 2-8. Surface Water Drainage
UM-UZ000

Figare 2-9. Sentinel Wells at Holbrook Elementary School, SWMU 103

Around,the Former Heiting-OiLUSTs at.SWMU 103

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Figure 3=1: 1;1,2;2-Tetrachloroethane and Trichloroethene Concentrations:
Groundwater in the SWMU 103 Source Area.

I
Tetrachloroefhetrachlorom
(PCE) Cl
Cl
/; C—C—CI
CI�C C� \ H
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(TCE) .. (TCA)
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ND 1s0 0 6so :ri"r a�`, ?nt, 711014 sse Al a5 !`� �W 17.6
14d j 5�
IJ, D Qi/—11
1"i-3-'• JG.�DW1 28 9
Gr n {�
r, �—
A1W 17J 74;'t.'t�s
a I u: �SH� CRtV.8
� •I ..' .-
n fr� h15'J=35 / . ` AU7E 13 1ns+�r
�1rPx' ci
a;, SENTINEL. WELLS' FOR
. ¢ " a SW 8.7
5 HEATING -OIL UST
I h'ti b u
Saw .�.z� (MW-.43/MW-44)
�Snl x Q
0`MW3 \6,7 U
\ V
s 22 SENTINEL WELLS' FOR a
0.9-i200' 25.3 �'j.....1 HOLBROOK�'.:SCHOOL .d.'o.d% :
t('V4-f e '
'. S 7 (MW-41/MW-42).
,ate:
,o ' 22.9 LBROOK
EME'NTARY•> d �c3.p`
9SE.�%� - MURRA
�'M7.1
�O1 s 23.9 SCHOOL. Ci PJ PLACE; Q
NA\ Y Y.IR CH CtP 1 CPL7.
\ w \ vl�'{-.�G'O' Q / t� l (�j►' MC CABER
6.(i 24\ Q O OQ BIS j] •�,� TREET05\ ..
3.5 SW3 iJ�j BSH� Q p O A40 :�
\ \ . I - 21.4 'SIRE .0 O ' Q 'v b �� 1 'r - RUCKERQ \' �
G
W1 19
SW d
STREET INO.Q �'ri .\;
-32 SOUTHSTREET Q\N -( L
6C /• . SEARIGHT .a n IRVIiN
n 0 ^, RIYE',..
LEGEi�: N
m:............ SHALLOW MONITORING .WELL. LOCATION
.'.............: DEEP. MONITORING WELL LOCATION FIGURE.3-3-
-_....'......... SURFACE. PLATER FEATURE
... 1,1,2',2-TETRACHLOROETHANE
`""" EXTENT OF GROUNDWATER.
...:................:......:.. BENZENE
_.......................:TRICHLOROETHENE AND. SURFACE WATER
EkVWLE: . .. ..... ..
"''' -' CONTAMINATION. AT
29J'............. :....... 1,1,2,2-TETRACHLOROETHANE 0 250' 50C
'00........................ BENZENE
too.:...........::.APHTHLENEW
SWMU 103'
41............,..................... r TRICHLOROETHENE SCALE: V = 500'
Fort Bragg, NC
Note: Width of the arrow lndicates Contaminant Concentrations.
Source: U.S.%Army Engineer District Corps of Engineers Savannah, Georgia. PARSONS'
draw1974586AItema6ve2:cdr ma '7/23107.'Da4'

77,
Not to Scale-
LEGEND j
Mounds -1 Sand
solvents and their Clay
products r_
Aual chlorinated solvent V Water table
1 surface of clay
is/2-methylnaphthalene/BTEX _ Monitoring wall
T G05-0250 3D Mode13

4ALLY LEFT BLANK

8 w 4. R ulslf u tr Irr11i! �1.51
tP l! l Rural l LLtr nl h r i /O
I&N _7 (POTENTIAL U
R.
e .COSACKGROUND JOCATION)., �. r
V�
SPEAR'
0.: 20 500 .. l 0RtQE
5
��r Of 1,1;2 2-TETRACHLOROETHPi1E
sPFMA110� \.
SCALE: I" 500'
SW14.
r Iati1 11` It . P.I1R4:O9MSWMU 103-CUT S�W'l$ ..� O
GANAND
DRIVfi0N`1l•,=f, M J 1�
FORMER !k SW12 c
n S HEATING L -
01T
US.,fir �. SW71 r 16:6 , � I
ND j m a ' ; 4/,5Wi�
Id: 4• ` Il14
O
41 UU
;� s I ' �• Q'\ S}tAR _ R7VE'
D{21VE .
'W 3 ,�f V ®ii✓?i�tiD9 - `�. u
c ,�� 1111 0
16
SW9 p
IMw9� :6 8.7
MN 3 IYM1 . °,.� t
O Hf OOK .. �.
.SWB .ELEMENTARY :� . q d:
SCHOOL'tx'
Imp
.SW'1I �
\ Dµr^1\� 22.9�.�Y�,PCACE'
\ " i a 6ttlU CP?. y Li �7
d, • 1 �. A+C CAB[
} rtW t9. HOP 23.9 DSIr�� ` b�REET
stnr�.. ' p O A ja b'1 Q. c�.o\ �. Dish t� C4 0
\ ` sT 21.4 pRUCKEFZ`!
4 `r.
_ 1 1
3 5 � � �• p 0 O /��r>o p��a .,a � C? .� .`Q� Cj
q a
//
ATKPlSOFI.0. � Q STREET � Q
O LT�
lit M3? SSRTEE
Y
El 417
5 A i cH. (� ti `- 7 /� �RI�E ..
LEGEND:. •
0 ...:.......:.-.. ....:..:::.....BUILDING.
_ .. ...:.:....:..'..:. ASPHALT ROAD,
.,................,..GRAVEL ROAD.
}� ................ RAILROAD TRACKS
SURFACE. WATER FEATURE
..:....... 1,1, 2, 2 JE T RAC HLO ROE THANE
.........................:.....:..PROPOSED DEEP MONITORING WELL mFIGURE 5.1•
,
.. TRICHLOP,OETHENE.
O3.5r. . USACE SURFACE, WATER :SAMPLE: PCA(ppb) SWMU•1,03,ALTER NATIVE .1'. REMEDY:
,
:..........SHALLOW MONITORING WELL. LOCATION
z .:...... ::;DEEP. MONITORING WELL LOCATION MONITORED NATURAL ALTERNATION
..............:.:' INTERPRETED CONTAMINANT
MIGRATION_DIRECTiON : OF GROUNDWATER AND
COMBINATION EXISTING FENCING AND
SURFACE W TEIt AERATION
ENGINEERED AERATION/'
VOLATILIZATION OF SURFACE WATER
Fort'Pr agg, NC:
Note: Width of the arrow indicates Contaminant�Condentrations. PARSONS
Source: U.S. Army Engineer District Corps of Engineers, Sayannah, Georgia.:
draw1974586AltemaUve l.cdr ma 1123101 pgl

1r
0 250 500 4�f
SCALE:1" = 500'
SWMU 103
f i
r
QSwg.. f PdW-22 ''
I L J:�
`ND 1 p
MW -4
td'rJ-5'
\` q iMW-
�� 1J -trlw 3 ti��!
f W :;.
s
111wA, ;;l
fnl� h i1
`V iA;0 19
\ f SW2
q
STI
_?�\\. 3.5
'5-a ZSa
A1bV e [PU'fEiTT nZ c15,V
tBACKGR,OUNG' L
sT�E MWrV .'(POTENTIAL
ACKGROUtJOC�TION)o
to
O %VE
'PET p, 1 I'2 2-TETRACHLOROETHANE
5�Fd'cV=1F ' 4 O
1
o SW14
Roan SW13
iNEYCUTT _� DRIV .ND
MW-sND
.W,7 6 aMW-�3
FORMER SW12OIL c
71
— Hti=ATUST
ING .
MYJ69344C'
�$WW 17.6 0 a
tvI v- 2849
.DRIVE f '; EGI.. �Pr1YJ8i2�. -
OgNE .
SHARP
�' 1,11V-3o•e'-r�' 61dB SMW-51
I, U
87
�-• �� SW8 -HO OOK
ELEMENTARY a -0 a
S1AR SCHOOL s�Ta.a �'�ry
25.3 '
�Db P�ACEN
22.9 00 Q a4/1 \ �y QtRSCH "CIR. ¢ 1 . .19j o-i
jl Y^ 111 MC CA131 '
/ EISHOP . TP.EE'
sj3 0 o
p CpEQ. \`�
P rA-�Srtow.
f,� l ATKmsoN
i STP.EET Q
crz,
'mP11W-32 i1. a '=.r SON o- SOUTH LUCAS. (�N
p1K �- .ST
El REET
El p Q" .4.4� 4 b
k" dEl IRWINLEGFM: V.t - rr _n l 7 O ^ . DRWE a 1
0 ..................:..:..-.BUILDING
................. ASPHALT. ROAD.
— . ..:..........'... GRAVEL . ROAD
}—i—}_ • • . • .....'......"'RAILROAD TRACK$
— _ _ _ _........., .,.SURFACE WATER FEATURE
..: 1,1,2, 2=TETRACHLOROE THAIJE
.PROPOSED DEEP MONITORING WELL
.: TRICHLOROETHENE O FIGURE.••••USACE SURFACE WATER SAMPLE PCA(ppb)
2'... ...,..'.SHtiLLOW MONITORING WELL LOCATION MONITORING WELL LOCATION SWMU.103:ALTERNATIVE:2:REMEDY:.
,�'.::......:..:DEEP.
:.::..,.:........INTERPRETED CONTAMINANT
MIGRATION DIRECTION SOURCE AREA TREATMENT USING:.'
. "COMBINATION OFNEWANDEXISTING FENCINGAND ENHANCED" EIOREMEDIATI.ON
SURFACE WATER AERATION'
AND ENG.INEERED:AERATiON/.
PARSONS PROPOSED SOURCE AREA APPLICATION VOLATILIZATION OF"SURFACE 'WATER.: .
Fort.Brag9r NC
Note:.YVidth of the "arrow indicates Contaminant Concentrations. PARSONSSource: U.S: Army Engineer District.Corps of Engineers Savannah, Georgla:
dravA974586AItemative 2.cdr ma 7/23107 pg2

�i�r SWMU 103-V l/
t
Z,tW
! r ►r _
r �
ND
Inv
HARP
?y� ��•' I�r s,�f(tJtlll.4 t'`J�".�1il�fl��0�
MW.27 (POTENTIAL
ACKG�R�OUND L_OCATION)�
7 IV
N D
GANAIV
DRIV
r{
l SW1 16.6 tom"'
Al
} d`SWi 17.6
K93'44C
r' �0/ SW7 @ 28.%%!n
9
R+VE• 1..1
�
xE nn P1V1.3a.J ®MW-51
0
HOLBROOK. a`
0
ELEMENTARY ..�.t�
:,d
253 D
B2 SCHOOL . p Iva c+s'
sBI 229❑ :.C.
]
PLACE
1t F•:� tns C11'` Lail 'd:'10 - O jA Q• HOSCH CIR: � E.� �f P.C'CASE
Q'BISHOP 'a ..�]:I('�-•1\ �j TPEEST
T�
S 21.4 p Q l,W O 4'\ . ,A b 144�`'
��. STRE a .. P . Ly'A� �. RUCKED \ r
Q
Ak
o o Ol a p �I�
19 W 0 r -raowQ 'CsAQ
�'
•4 ATKINSON
! "STREET. - Q - ��
Tya- ¢ +rl-s3 �• [P'C7tT,�'
\
Y \-
�-- �
rsay Gy SOUTH LUG"
STREET" '-!10N .
SEARI ?RIGt`1 " 0 n t l �. • ^ DRI�+E b,
LEGEND:
( •.:.:...::..:.•.:.....:::..:::BUILDING
... ASPHALT ROAD -
ROAD.
.:.... , ; i
B.',.. • RAILRDAD :TRACKS
_ . ..: SURFACE.'WATER FEATURE
.. .1,1,2,2-TE TRACHLOROETHANE:'
® ........::......:.................PROPOSED DEEP MONITORING WELL
TRICHLOROE'THENE'
USACE SURFACE .WATER. SAMPLE- PCA(ppb)
.:SHALLOW MONITORING. WELL :LOCATION .
..:.. ..:DEEP. MONITORING : WELL LOCATION
....
................ INTERPRETED CONTAMINANT
MIGRATION DIRECTION
PROPOSED GROUNDWATER DRAIN AND.SUMP
®. PARSONS PROPOSED SOURCE AREA APPLICATION
Note: Width of the arrow Indicates Contaminant Concentrations.
-Source: U.S. Array Engineer District Corps of, Engineers Savannah, Gec
draM974586 A8ernative 2.cdr ma 7123107 pg3
FIGURE.5.3
SWMU-103 i4LTERNATIVE: 3 :REMEDY:.
SOURCEAREA TREATMENT USING
ENHANCED BIOREMEDIATIONi—
PUMP=AN®-TREAT CONTAMINATED
GROUNDWATER TO..
PROTECT SURFACE. -WATER
Fort Beagg, NC "
PARSONS :

Typical Section Trench Al (35 feet deep) .' .. .
NORTH
SOUTH. .
MW-9(2541:at surface)
Carbon--
Elevations
_
MW-43
(amsi);
2541.
2501. .
�.
Treated" Water .
Drain Clean Out
Discharged.
Soil-Backfill
to Creek ..:
r
18" Sump
f
y
228'
amsF =
N
Gravel ". A
r OS
titer. Level
223
Pumping -Water Level
_
219
HDPE:Perforated Drain
'— — -218'
0 5%.Slope "—� . "'` ,'
215'
500' .
(not to scale). .
WEST.
EAST
Treated Water
MIpical Section Trench B1 (304eet deep).
Elevations:.
Discharged
(amsl):
to Creek
Carbon
. .
18" Sump
MW-40
.
• 219'.
221'
-Soil Backfill
Pre located 16"
21,0' A 3r.05 Water Level
212'
Sewer Line .0
M
Gravel
Pumping
Range-
o
N
6;'
y.
Perforated
i