NCD981021157_20020614_New Hanover County Airport Burn Pit_FRBCERCLA RA_Draft Feasibility Study Report-OCR

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REMEDIAL PLANNING ACTIVITIES AT SELECTED
UNCONTROLLED HAZARDOUS SUBSTANCES DISPOSAL
SITES FOR EPA REGION IV
U.S. EPA CONTRACT NO. 68-W9-0056
DRAFT
FEASIBILITY STUDY REPORT
FOR THE
NEW HANOVER COUNTY AIRPORT
BURN PIT SITE
WILMINGTON, NORTH CAROLINA
WORK ASSIGNMENT NO. 005-4L5Q
DOCUMENT CONTROL NO.
7740-005-DR-BFYX
May 18, 1992
Prepared for:
U.S. Environmental Protection Agency
Prepared by:
CDM Federal Programs Corporation
2030 Powers Ferry Road, Suite 490
Atlanta, Georgia 30339
**COMP ANY CONFIDENTIAL**
~l.::::)U IJ
IPA -REG1ON IV
ATLAMTA,GA
This document has been prepared for the U.S. Environmental Protection Agency
under Contract No. 68-W9-0056. The material contained herein is not to be disclosed
to, discussed with, or made available to any person or persons for any reason without
the prior expressed approval of a responsible official of the U.S. Environmental ·
Protection Agency.
CDM ARCS IV
Atlanta, Georgia
NHANFS09.035
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TABLE OF CONTENTS
Section
EXECUTIVE SUMMARY .............................. ES-I
1.0 INTRODUCTION .................................... 1-1
1. 1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . : . . . . . 1-1
1.2 Site Location and History . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1. 3 Environmental Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
1.3.1 Physical Features . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
1.3.2 Hydrology ............................... 1-8
1. 3. 3 Regional H ydrogeology . . . . . . . . . . . . . . . . . . . . . . . 1-9
1.3.4 Site Hydrogeology ......................... · 1-13
1.4 Results of Previous Investigations .................... .1-21
1.4.1 Remedial Investigation . . . . . . . . . . . . . . . . . . . . . . . 1-21
1.4.2 Baseline Risk Assessment .................. : . . 1-22
1.5 Site Restoration Objectives for Groundwater . . . . . . . . . . . . . . 1-27
1.5.1 Cleanup Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . 1-27
1.5.2 · Extent of Groundwater Contamination . . . . . . . . . . . . . 1-27
2.0 IDENTIFICATION, SCREENING, AND EVALUATION OF
TECHNOLOGIES AND PROCESS OPTIONS . . . . . . . . . . . . . 2-1
2.1 Screening of Groundwater Technologies and Process Options . . . . 2-1
2.2 Evaluation of Technologies and Process Options . . . . . . . . . . . . 2-4
2.2.1 Containment Technologies ..................... 2-4
2.2.2 Extraction Technology ........................ 2-6
2.2.3 Treatment Technologies ....................... 2-7
2.2.4 Discharge Technologies . . . . . . . . . . . . . . . . . . . . . . 2-20
2.3 Summary of Process Options Evaluation . . . . . . . . . . . . . . . . 2-23
2.4 Development of Remedial Action Alternatives . . . . . . . . . . . . . 2-23
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Section
TABLE OF CONTENTS
( continued)
3.0 EVALUATION OF REMEDIAL ACTION ALTERNATIVES ....... 3-1
3 .1 Groundwater Extraction Analysis . . . . . . . . . . . . . . . . . . . . : . 3-2
3.1.l Aquifer Characteristics ........................ 3-3
3.1.2 Groundwater Modeling Assumptions . . . . . . . . . . . . . . . 3-3
3.1.3 Theis Analysis Results ...................... : . 3-4
3.2 Alternative 1 -No Action .......................... 3-6
3.2.1 Description ............................... 3-6
3.2.2 Evaluation ............................... 3-7
3. 3 Alternative 2 -Vertical Barrier . . . . . . . . . . . . . . . . . . . . . . . . 3-8
3.3.1 Descnpuon ............................... 3-8
3.3.2 Evaluation ............................... 3-10
3.4 Alternative 3 -Groundwater Extraction and Physical Treatment
(Air Stripping) with Discharge to POTW .............. · 3-14
3.4.1 Descnpuon .............................. 3-14
3.4.2 Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16
3.5 Alternative 4 -Groundwater Extraction and Physical/Chemical
Treatment (Chromium Reduction, Metals Precipitation, and
Air Stripping) with Discharge via Spray Irrigation . . . . . . . . . 3-20
3.5.1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20
3.5.2 Evaluation .... ~. . . . . . . . . . . . . . . . . . . . . . . . . 3-23
3.6 Alternative 5 -Groundwater Extraction and Physical/Chemical
Treatment (Chromium Reduction and Metals Precipitation) with
Discharge to Surface Water . . . . . . . . . . . . . . . . . . . . . . 3-28
3.6.1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-28
3.6.2 Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-30
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Section
TABLE OF CONTENTS
( continued)
4.0 ANALYSIS AND SUMMARY OF ALTERNATIVES 4-1
4.1 Threshold Criteria ............................. : . 4-3
4.1.1 Overall Protectiveness ........................ 4-3
4.1.2 Compliance with ARARs ...................... 4-3
4.2 Primary Balancing Criteria ......................... 4-5
4.2.1 Long-Term Effectiveness and Performance .......... ·. 4-5
4.2.2 Reduction of M/T/V through Treatment ............. 4-5
4.2.3 Short-Term Effectiveness ..................... 4-11
4.2.4 Implementability . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11"
4.2.5 Cost Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
4.3 Summary ................................... 4-11
REFERENCES
APPENDICES
Appendix A -Boring and Well Logs
Appendix B -Groundwater Analytical Results
Appendix C -Cost Estimates
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LIST OF FIGURES
Figure
1-1 Site Location Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1-2 Site Features Map ................................. 1-6
1-3 Regional Hydrogeologic Cross-Section Location Map . . . . . . . . . . . 1-10
1-4 Regional Hydrogeologic Cross-Section Map A-A' ............. 1-11
1-5 Site Hydrogeologic Cross-Section Location Map . . .. . . . . . . . . . . . 1-15
1-6 Site Hydrogeologic Cross-Section B-B' . . . . . . . . . . . . . . . . . . . 1-16
1-7 Water Level Elevation Contours -April 9, 1991 . . . . . . . . . . . . . . 1-17
1-8 Water Level Elevation Contours -April 17, 1991 . . . . . . . . . . . . . 1-18"
1-9 Water Level Elevation Contours -May 7, 1991 .............. ·. 1-19
1-10 Extent of Benzene Contamination in the Surficial Aquifer 1-29
1-11 Approximate Extent of Chromium Contamination
in the Surficial Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-30
1-12 Approximate Extent of Chloroform Contamination
in the Surficial Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-31
1-13 Approximate Total Extent of Contamination in the Surficial Aquifer . . 1-32
2-1 Typical Air Stripping Tower . . . . . . . . . . . . . . . . . . . . . . . . . . , 2-11
2-2
3-1
3-2
Typical Activated Carbon Filter ........................ •2-16
Extraction Well Drawdown (15 gpm Total Pumpage) ............ 3-5
Cross-Section of Typical Impermeable Surface Cap 3-9
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LIST OF TABLES
Table
ES-I Summary of Alternatives Evaluation . . . . . . . . . . . . . . . . . . . . . ES-7
1-1 Well Construction and Water Level Data . . . . . . . . . . . . . . . . . . 1-20
1-2 Groundwater Data Summary .......................... 1-23
1-3 Summary of ARARs and Cleanup Criteria . . . . . . . . . . . . . . . . . 1-28
2-1 Initial Screening of Technologies and Process Options . . . . . . . . . . . 2-2
2-2 Optimum Treatment pH Values ......................... 2-9
2-3
2-4
2-5
2-6
4-1
4-2
4-3
4-4
4-5
4-6
4-7
Henry's Law Constants for Volatile Compounds of Concern
Freundlich Parameter K Values for Contaminant Compounds
2-13
2-17-
Effluent Criteria for Discharge Alternatives . . . . . . . . . . . . . . . . . 2-21
Evaluation of Process Options ......................... · 2-24
Summary of Institutional and Land Use Restrictions . . . . . . . . . . . . 4-2
Summary of the Public Health and Environmental Effects Evaluation 4-4
Federal Regulations Affecting Implementation of the Alternatives
Under Evaluation ............................... ,. 4-6
North Carolina Regulations Affecting the Implementation of the
Alternatives Under Evaluation . . . . . . . . . . . . . . . . . . . . . . . . 4-7
Local Regulations Affecting the Implementation of the
Alternatives Under Evaluation ........................ 4-8
Long-Term Effectiveness and Performance for
Remedial Action Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
Short-Term Effectiveness and Implementability Evaluation . . . . . . . . 4-10
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Tol1k
4-8
4-9
LIST OF TABLES
( continued)
Summary of Present Worth Costs for Remedial Action Alternatives . ; 4-13
Summary of Alternatives Evaluation .................... '. 4-14 ·
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EXECUTIVE SUMMARY
The New Hanover County Airport Burn Pit Site located in Wilmington, North
Carolina, was proposed for inclusion on the National Priorities List (NPL) on June
24, 1988, and was placed on the NPL in March 1989. Soil removal activities were
performed at the site in 1990, following a signed Administrative Order of Consent
from EPA. A remedial investigation (RI) was then conducted by EPA in 1991 (EPA,
1991). The purpose of this feasibility study (FS) is to determine the extent of
groundwater contamination and to evaluate the possible remedial action alternatives
for the site.
SITE DESCRIPTION AND ffiSTORY
The New Hanover County Airport Burn Pit Site is located on Gardner Drive,
approximately 300 feet west of the New Hanover County Airport, and about 1.5 miles
north of Wilmington, North Carolina. The site is approximately four acres in size . :
with the former bum pit area occupying about 1,500 square feet near the center of the
site.
Land use in the vicinity of the site is commercial, industrial, and residential. The
Airport Authority intends to maintain the entire west side of the airport for industrial
development and is actively marketing the available industrial property. Currently,
there are several occupants near the site, including a rental car maintenance facility, a
closed sawmill/lumberyard; and a trucking company. The closest residential area· is
separated from the site by a road, railroad tracks, and a wooded area, and is
estimated to be approximately 0.2 miles to the west. Southwest of the site are ten
underground storage tanks (USTs), reportedly owned by the U.S. Army Corps of.
Engineers, which formerly owned the airport. Approximately 600 feet from the site
is a forested area.
ES-1
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An airport facility was originally built at the site in the 1920s. The airport was used
as a military hospital during World War II. The date of construction of the original
pit is unknown, but a second pit was constructed in 1968 and used until 1979 by the
Air Force Cape Fear Technical Institute and local industries for firefighter training
purposes. The Wilmington Fire Department also used the burn pit for firefighter
training purposes during the years 1968 to 1974. It has been estimated that 100 to
500 gallons of jet fuel were burned daily in the pit during this period. Jet fuel,
gasoline, petroleum storage tank bottoms, fuel oil, kerosene, sorbent materials from
oil spill cleanups, and on at least one occasion, confiscated marijuana, were burned in
the pit. Although water was the primary extinguishing agent, carbon dioxide and dry
chemicals were also used.
The county applied for a permit to close the burn pit by land application of the pit
contents, but this request was denied by the state. Sampling by the New Hanover
County Department of Engineering in 1985 showed heavy metals and volatile organic
' compounds (VOCs) in the pit sludge. In May 1986, the North Carolina Department
of Health Services sampled the bottom sludge layer of the pit and soil adjacent to the
outside of the pit. Heavy metals, polycyclic aromatic hydrocarbons (PAI;Is), and
VOCs were detected in these samples. A survey for hazard ranking purposes was
conducted at the site on January 9, 1987 by EPA. The site was proposed for
inclusion on the National Priorities List (NPL) on June 24, 1988.
The New Hanover County Airport Burn Pit Site was placed on the NPL in March of
1989. EPA identified the potentially responsible parties (PRPs) as New Hanover
County (owner of the airport), the City of Wilmington, Cape Fear Technical Institute,
the United States Air Force (all of which trained firefighters at the site), the U.S ..
Army Corps of Engineers (constructed the site), and the United States Customs
Service (burned confiscated drugs at the site).
ES-2
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The Agency for Toxic Substances and Disease Registry (ATSDR) conducted a health
assessment of the New Hanover County Airport Bum Pit Site in March of 1989. The
health assessment concluded that the site is of potential public concern because of risk
to human health resulting from possible exposure to hazardous substances at
concentrations that may result in adverse human health effects. On March 19, 1990,
EPA repaired a break in the berm around the bum pit area. In April of 1990, EPA
collected soil and groundwater samples at the site as part of an emergency response to
the break in the berm.
EPA gave approval to the PRPs to perform removal activities at the site following a
signed Administrative Order of Consent effective May 11, 1990. Consequently, .in
November and December of 1990, the PRPs removed waste materials from the bum
pit and firefighting area along with contaminated surface and subsurface soils.
Structures associated with firefighter training activities were dismantled and removed.
All removal activities were overseen by EPA. The structures consisted of a fuel
supply tank and associated underground piping, a railroad tank car, automobile
bodies, and an aircraft mockup. Soil removal continued in these areas until no visual
contamination remained or groundwater was encountered. EPA obtained soil samples
from the bottom of the excavated areas prior to backfilling to grade with clean soil.
The sampling investigation was performed following soil removal to confirm the ·
complete excavation of contaminated soil. Several drums of paint sludge were also
found at the perimeter of the site and were removed and properly disposed of
according to Resource Conservation and Recovery Act (RCRA) regulations.
PREVIOUS INYESTIGA TIO NS
A remedial investigation was performed by EPA in 1991. Preliminary remediation
goals (PRGs) were developed for the site by EPA for groundwater and soil. The soil
PRGs were intended to be protective of exposure via both air and soil ingestion
ES-3
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pathways. These criteria were used to determine if contaminated soils had been
completely excavated and removed.
Based on the results of previous soil and groundwater confirmation sampling, it. was
determined that all soils above the PRGs had been removed and that the extent of
contaminated groundwater required further delineation. Additional temporary monitor
wells were installed and sampled to determine the placement of the permanent
monitor wells. Six permanent monitor wells were installed and sampled in April of
1991. On April 9, 1991, five soil samples, both surficial and subsurface, were
collected on the first round; on April 17, 1991, a second round of samples was
collected and analyzed for volatile organic compounds in groundwater only. A third
round of groundwater samples were obtained from the site on May 7, 1991.
In April 1992, FPC conducted a human health and ecological assessment to evaluate
the potential risks from exposure to chemicals present at the ·New Hanover County
Airport Bum Pit Site. The risk assessment concluded that soil, surface water, and
fugitive dust are not expected to be significant pathways of exposure at the site in its
existing condition. However, based on the future potential exposure to local residents
via consumption of contaminated drinking water and inhalation of contaminant vapors
by showering, six groundwater chemicals of concern at the site were identified. The
chemicals of concern in groundwater at the site are benzene, beryllium, chloroform,
chromium, 1,2-dichloroethane, and lead, based on toxicity, frequency of detection,
and exceedance of water quality standards. Finally, the risk assessment did not
identify the presence of endangered species of flora or fauna.
EXTENT OF CONTAMINATION
The chemicals of concern in groundwater at the site are benzene, beryllium,
chloroform, chromium, 1,2-dichloroethane, and lead. The derived cleanup goals for
benzene, chloroform, chromium, and 1,2-dichloroethane were based on the North
ES-4
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Carolina Drinking Water Quality Standards. The cleanup goal for beryllium was
based on the proposed Safe Drinking Water Act Maximum Contaminant Level.
(MCL). The cleanup goal for lead was based on new regulations for treatment
technique action levels.
The extent of groundwater contamination was estimated by using a compilation of
three separate plumes --benzene at I µg/1, chromium at 50 µg/1, and chloroforin at
0.19 µg/1. Because lead and beryllium were each detected in one well and during one
sampling round only, and 1,2-dichloroethane was detected only in one well during
two sampling rounds, and since these two wells are within the total extent of
groundwater contamination, specific plumes were not estimated for these compounds.
The approximate total areal extent of groundwater contamination is 3 .4 acres. The
vertical extent of contamination extends throughout the 28 feet of the surficial aquifer.
However, to better define the extent of contamination, several additional monitor
wells should be installed.
REMEDIAL ACTION ALTERNATIVES
Remedial action alternatives were formulated considering groundwater contaminant
types, contaminant concentrations, and applicable technologies. The five alternatives
assessed for this site are:
Alternative 1 -No Action
Alternative 2 -Vertical Barrier
Alternative 3 -Groundwater Extraction and Physical Treatment (Air Stripping) with
Discharge to POTW
Alternative 4 -Groundwater Extraction and Physical/Chemical Treatment
(Chromium Reduction, Metals Precipitation, and Air Stripping) with
Discharge via Spray Irrigation
ES-5
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Alternative 5 -Groundwater Extraction and Physical/Chemical Treatment
(Chromium Reduction and Metals Precipitation) with Discharge to
Surface Water
The alternatives were evaluated on the basis of long-term effectiveness, compliance
with applicable and or relevant and appropriate requirements (ARARs), reduction of
toxicity, mobility, or volume through treatment, short-term effectiveness,
implementability, and cost. A summary of this evaluation is presented in
Table FS-1.
ES-6
NHANPS09.037
-- - -
I: No Action
2: Vertical Barrier
--·--- --- -
Ongoing monitoring of
groundwater contami-
nant levels would be
conducted to assess
contaminant migration.
Does not meet
ARARs.
The potential for
offsite contamination
migration is greatly
reduced. ARARs are
not met at the site.
Length of service
unknown (not pcnna-
nent).
TABLE ES-!
SUMMARY OF ALTERNATIVES EVALUATION
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
None. None. None.
Greatly reduces Potential release of Design of slurry wall and im-
mobility. No reduc-organic volatiles permeable cap; stonnwater
tion in toxicity and during slurry wall runoff drainage and collection
volume. installation. Noise for cap. Air monitoring dur-
nuisance due to ing implementation.
operation of heavy
equipment.
- ---
0 74.7
L5 1,076.1
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- --·-
3: Groundwater
Extraction and
Physical Treatment
(Air Stripping)
With Discharge to
P01W
--
Permanent remedy.
ARARs arc met.
- - --
Eliminates MrrN of
contaminants. Elimi-
nates potential for
offsite migration.
High degree of risk
reduction for inges-
tion and inhalation of
groundwater.
TABLE ES-I
(continued)
Potential release of
organic volatiles
during extraction
and treatment sys-
tem operation.
Noise nuisance due
to operation of
drilling equipment.
---
Design of extraction, treat-
ment, and discharge systems.
Air stripping of benzene to
"below dctc.ction limit" re-
quired. Treatment of air strip-
ping off-gases may be re-
quired. Pretreatment for TSS
and iron may be required.
Discharge permit acquisition
under consideration. Ongoing
monitoring of groundwater
contaminant levels and the
treatment system should be
conducted to assess extraction
and treatment systems perfor-
mance. Must meet City of
Wilmington POTW discharge
requirements and CAA re-
quirements. No future land
use restrictions would be
required.
-
2
---
. 1,152.0
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-- -- - -
4: Groundwater Permanent remedy.
Extraction and Physi-ARARs are met.
cal/Chemical Treat-
ment (Chromium
Reduction, Metals
Precipitation, and
Air Stripping) with
Discharge via Spray
Irrigation
- --
Eliminates MrfN of
contaminants.
Eliminates potential
for offsite migration.
Greatest degree of
risk reduction for
ingestion and
inhalation of
groundwater.
--
TABLE ES-I
(continued)
Potential release of
organic volatiles
during extraction
well installation.
Noise nuisance due
to operation of
drilling equipment.
Sludge/filter cake
generation from
precipitate.
-- -
Design of extraction, treat-
ment, and discharge systems.
Metals precipitation should
achieve required North
Carolina Drinking Water Qual-
ity Standards for inorganics.
Air stripping should achieve
standards for organics.
Treatment of air stripping off-
gases may be required. Pre--
treatment for TSS and iron
may be required. Storage may
be required during wet weather
and under freezing temperature
conditions. Ongoing monitor-
ing of groundwater contami-
nant levels and the treatment
system should be conducted to
assess extraction and treatment
systems performance. Must
meet North Carolina Drinking
Water Quality Standards for
groundwater and CAA emis-
sions requirements.
----
2 1,525.1
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-·-- -
5: Groundwater
Extraction and Phys-
ical/Chemical
Treatment (Chromi-
um Reduction and
Metals P=ipitation)
with Discharge to
Surface Water
--
Permanent remedy.
ARARsarcmet.
- - -
Eliminates MrrN of
contaminants. Re-
duce source of
groundwater
contamination.
Greatest degree of
risk reduction for
ingestion and
inhalation of
groundwater.
- -
TABLE ES-1
(continued)
Potential release of
organic volatiles
during extraction
well installation.
Noise nuisance, due
to operation of
drilling equipment.
Sludge/filter cake
generation from
precipitate.
- - -
Design of extraction, treat-
ment, and discharge systems.
Metals precipitation should
achieve North Carolina Surface
Water discharge requµ-efflcnts
for inorganics. A 4,000-foot
pipeline would be required for
discharge to Smith Creek.
Permit acquisition under
consideration. Ongoing
monitoring of groundwater
contaminant levels and the
treatment system should be
conducted to assess extraction
and treatment systems
performance. Must meet
North Carolina Surface Water
discharge requirements.
-
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1.0 INfRODUCTION
1.1 PURPOSE
CDM Federal Programs Corporation (FPC) has prepared this Feasibility Study (FS)
Report for the New Hanover County Airport Bum Pit Site (the site) in Wilmington,
North Carolina, under contract to the U.S. Environmental Protection Agency (EPA).
The purpose of this report is to present viable alternatives for remediation of the New
Hanover County Airport Bum Pit Site. These alternatives are designed to be
consistent with objectives of the Superfund Amendments and Reauthorization Act of
1986 (SARA), the National Contingency Plan (EPA, 1992a) and current EPA
Guidance for Conducting Remedial Investigations and Feasibility Studies Under the
' Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
(EPA, 1988).
1.2 SITE LOCATION AND HISTORY
SITE LOCATION
The New Hanover County Airport Bum Pit Site is located on Gardner Drive,
approximately 300 feet west of the New Hanover County Airport, 1.5 miles north of
Wilmington, North.Carolina at 34°16'29" north latitude and 77°54'55" west
longitude. The site is approximately 4 acres in size with the former bum pit area
occupying about 1,500 square feet near the center of the site. The site location is
shown on Figure 1-1.
Land use in the vicinity of the site is commercial, industrial, and residential. The
Airport Authority intends to maintain the entire west side of the airport for industrial
' development and is actively marketing the available industrial property. Currently,
there are several occupants near the site, including a rental car maintenance facility, a
1-1
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I -CDM FEDERAL PROGRAMS CORPORATION
ant.idiaryal.C.-.Dlicma-1:Mi.:Lrolis.
SITE LOCATION MAP
NEW HANOVER COUNTY AIRPORT BURNPIT SITE
WILMINGTON, NORTH CAROLINA
FIGURE No. 1-1
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closed sawmill/lumberyard, and a trucking company. The closest residential area is
separated from the site by a road, railroad tracks, and a wooded area, and is :;•
estimated to be approximately 0.2 miles to the west. Southwest of the site are ten
underground storage tanks (USTs), reportedly owned by the U.S. Army Air Corps of
Engineers, which formerly owned the airport. Approximately 600 feet from the site
is a forested area.
The average annual precipitation of 53.35 inches is fairly evenly distributed
throughout the year. Historically, July is the wettest month. October through
December are generally drier than the spring and summer months. Over an annual
period, average monthly temperatures range from 45.6 degrees Fahrenheit (F) in
January to 80.3 degrees Fin July. The warm summer temperatures, combined with
heavy precipitation in these months, maintain a humid environment.
SITE HISTORY
The airport was built in the 1920s as a civil air facility owned by New Hanover
County. In 1942, the Department of Defense requisitioned the airport for the U.S.
Army Air Corps. In 1947 and 1948, the Army deeded the airport back to the county.
Formerly known as Bluthenthal Airport, in 1970 the facility was renamed as the New
Hanover County Airport.
The airport was originally developed as a military hospital during World War II. The
date of construction of the original burn pit is unknown, but a second pit was
constructed in 1968 and used. until 1979 by the Air Force, Cape Fear Technical
Institute, and local industries for firefighter training purposes. The Wilmington Fire
Department also used the burn pit for firefighter training purposes during the years
1968 to 1974. It has been estimated that 100 to 500 gallons of jet fuel were burned
daily in the pit during this period. Jet fuel, gasoline, petroleum storage tank bottoms,
fuel oil, kerosene, sorbent materials from oil spill cleanups, and on at least one
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EPA gave approval to the PRPs to perform removal activities at the site following a
signed AdmiQ.istrative Order of Consent effective May 11, 1990. Consequently, in ,.
November and December of 1990, the PRPs removed waste materials from the bum
pit and firefighting area along with contaminated surface and subsurface soils.
Structures associated with firefighter training activities (shown in Figure 1-2) were
dismantled and removed. All removal activities were overseen by EPA. The
structures consisted of a fuel supply tank and associated underground piping, a
railroad tank car, automobile bodies, and an aircraft mockup. Soil removal continued
in these areas until no visual contamination remained or groundwater was
encountered. EPA obtained soil samples from the bottom of the excavated areas prior
to backfilling to grade with clean soil. The sampling investigation was performed
following soil removal to confirm the complete excavation of contaminated soil.
Several drums of paint sludge were also found at the perimeter of the site and were
removed and properly disposed of according to Resource Conservation and Recovery
Act (RCRA) regulations. Groundwater samples were collected from four temporary
monitor wells during the soil sampling activities. A discussion of more recent site
investigations and the results of all the groundwater sampling rounds are discussed in
Section 1.4.
1.3 ENVIRONMENTAL SETIING
1.3.1 PHYSICAL FEATURES
The New Hanover County Airport Bum Pit Airport, as well as the subject site, are
situated on a local topographic high point in the area. The site occupies
approximate! y 4 acres of land on the western side of the airport and is surrounded by
asphalt paved roadways. Topography at and in the vicinity of the site is relatively flat
with elevations ranging from approximately 28 to 32 feet above mean sea level
(ams!). The roadways surrounding the site are slightly elevated, creating a basin
within the site. The site is mainly open and grass-covered. Some interspersed,
1-5
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- ----- - - -------- - - - -
100
APPROXIMATE
SCALE IN FEET
LEGEND
rrrnn1m1n,rTrrr
Uf.RM/ll0AD
[XCAVAIION
200
POSSIHl [ SURFACE WATER
DRAINAC[ AREAS
ARMY CORPS .
OF [NGIN[[RS
US! tAl,M
------------------
COM FEDERAL PROGRAMS CORPORATION
a 1uti.idiary ofC.unp On: .. cr & McKee Inc.
/1 -------=:::: __
\/
'\ /0 WILM/NG/ON
SITE FEATURES MAP
NEW HANOVER COUNTY AIRPORT. BURN PIT SITE
WILMINGTON, NORTH CAROLINA
BUILDING
f"OUNDAIIONS
-~,-SUPPLY TANK
(Removed)
",;'
<>' C,
"' V, ~ h
Cl
[}
FIGURE No. 1-2
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semi-mature to mature pine trees exist along the roadways and in the southeastern
corner of the site. The area surrounding the site is mainly wooded. ~-
Existing man-made structures at the site include the remnants of a military hospital
once present at the site. The remnants consist of three concrete block buildings, two
building foundations, and a septic tank. The three concrete block buildings include
two smaller buildings in the center of the site and a larger structure in the
southeastern corner of the site. All three buildings are abandoned and in disrepair.
The two building foundations are located in the southeastern corner of the site and are
the remnants of the largest buildings constructed on the site. The septic tank utilized
by the hospital is buried and located along the southern site boundary. These site
features are shown in Figure 1-2.
All site features associated with the burn pit and the fire fighter training activities
were removed in November and December of 1990 (previously discussed in
Section 1.2). These features included the burn pit, two oil-stained areas north of the
burn pit, an above-ground 10,000-gallon supply tank, underground piping from the
supply tank to the simulation areas, a valve box, an old automobile in the auto burn
area, two tank trucks and a railroad tank car in the tank car burn area, and a mock
aircraft made from 55-gallon drums in the aircraft burn area. The exact locations
from which the old automobile and the mock aircraft were removed are unknown.
The former burn pit was a 3-foot high, 30-by 50-foot rectangular berm constructed at
land surface. All contaminated soils associated with the burn pit and the two oil-
stained areas north of the burn pit have been excavated and removed from the site.
The excavations have been backfilled and graded to land surface with clean soils.
The areas are now covered with grass.
Regional physical features in the vicinity of the site include the Cape Fear River, the
Northeast Cape Fear River and their associated tidal flats to the west of the site, Ness
1-7
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Creek to the northwest of the site and Smith creek to the south of the site (see
Figure 1-1). J,and surface elevations increase northeast of the site.
1.3.2 HYDROLOGY
The hydrology, or surface water drainage, at the burn pit site is markedly influenced
by the. surficial sands. The surficial sands are permeable, allowing most precipitation
to infiltrate into the sands and recharge the surficial aquifer or become
evapotranspirated through the grasses growing at the site. The surficial sands are
permeable enough such that overland flow does not occur during most precipitation
events. In the rare event when the precipitation rate exceeds the infiltration capacity
of the sands, overland flow is retained onsite due to the slightly elevated roadways
encircling the site. Drainage ditches exist on the site along the southern, western, and
southeastern site boundaries; however, the ditches terminate with no established
discharge points offsite. Three low-lying areas exist along the boundaries of the site
(shown in Figure 1-2) where at times standing water is present; however, it appears
that little or no off site drainage occurs. Perimeter ditches also exist along the.
roadways outside the site on the west, north, and east site boundaries.
Regionally, the burn pit site is located on the western side of a north-south trending
topographic divide. Surface water drainage features splay south and west from the
site vicinity towards the Northeast Cape Fear River and its tidal flats approximately a
mile to the west and Smith Creek, approximately 4,800 feet to the south. Smith
Creek flows west into the Northeast Cape Fear River, which flows south into the
Cape Fear River which continues south into the Atlantic Ocean. Regional surface
water features are shown in Figure 1-1.
1-8
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1.3.3 REGIONAL HYDROGEOLOGY
New Hanover County is located in the Coastal Plain Physiographic Province of North
Carolina. The regional geology and hydrogeology of the county are marked by I, I 00
to 1,500 feet of unconsolidated and consolidated sediments overlying a crystalline
basement of metamorphic and igneous rock (Bain, 1970). Three aquifers are of
importance as drinking water sources in New Hanover County: (in descending order
below land surface) the surficial aquifer of undifferentiated late tertiary and surficial
deposits, the Castle Hayne limestone of the Castle Hayne Limestone Formation, and
the sandstone aquifer of the Pee Dee Formation. A regional cross-section location
map (Figure 1-3) and a regional cross-section (Figure 1-4) shows the relationships of
these aquifers to one another.
The surficial aquifer, the uppermost in the area, is composed of undifferentiated late
tertiary sediments and surficial deposits and consists mainly of coarse to fine quartz
sands and, to a lesser extent, clays silts and marls. The hydrogeologic unit ranges
from 20 to 60 feet in thickness (Bain, 1970). In the areas of Castle Hayne in the
northern part of the county and in Wilmington south of the site, the surficial aquifer is
absent. The sediments of the surficial aquifer lie unconformably on an erosional
surface of the slightly dipping sediments of the Castle Hayne Limestone Formation
and the Pee Dee Formation (EPA, 1992b). The water in the surficial aquifer exists
under water table conditions and conforms to the topography in a subdued manner.
The water table is generally encountered less than 10 feet below land surface.
Regional groundwater flow direction in the surficial aquifer is southeast towards the
Atlantic Ocean; however, local groundwater flow directions are dictated by
topography and recharge/discharge features, such as surface water bodies.
Recharge to the surficial aquifer is through infiltration of precipitation. Studies
indicate that, in some areas of the county, up to 90 percent of precipitation infiltrates
the surficial aquifer (Bain, 1970). Water is discharged from the surficial aquifer to
1-9
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PENDER COUNTY
0
Castle
Hoyne
0 Scot:s
Hill A
Murrayville
0
-B..:. : J( ·-
I~
City of ~ . , Wilmi:,gton
I c, ,, c, I D ~,\ ~, NEW G ' ' ,a ' -~fl <·t ~' COUNTY
/G ~
I "'t L, \c Q
Myrtle o CV
""' Grn,e f'/; ~ :, Q
BRUNSWICK QI 0. ~I I
n r ~ COUNTY iO I '-\J: 10 . ..,_
lg ~7 ~
:• "'t ..,,
fl ..,_
! 1/
"'t ji
IT ' ·N-
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1 J ,~ 2 0 2
'Jt) / '.; SCALE IN \ilLES
In . (') \
REGIONAL HYDROGEOLOGIC CROSS-SECTION LOCATION MAP
--NEW HANOVER COUNTY AIRPORT BURN PIT SITE -"-'~---------CD M FEDERAL PROGRAMS CORPORATION WILMINGTON, NORTH CAROLINA a 111baidwy of ump Oraa:r .t: MdCo. Inc. FIGURE No. 1-3
- - - - --- - - - -
c
A -a
f a:
NORTHW[ST iie ~ -• a a • 0.. ...
C 50 •
• ~ ·c" --.~ I> .... o-u
Ti.] titE 5 I g~~
0, :§ .1't_,:>
SEA
L[V[l 0
~ n a ,
'-' V,
-€" .!?&: E ~~:E.'f
~~-----------~'<. ________ ~~------:~;~~~~~=---
UNOIH[R[NTIATEO LATE TERTIA NO • _
-50-·
·· 100-
• ~ -150--.
z 0 ~ ~ -200-w
-250-
-JOO-
-J50-
-400--
SILT AND CLAY AOUICLUDE
(Pee Dee rormation)
SILT ANO CLAY AQUICLUDE
{Pee Dee Formolion)
------
I 0 :-... -;;;;-
HORIZONTAL
SCAL [ IN MIL[S
- - -
C .s • -~ :s ~
2
CllM n:DERAL PROGRAMS C<iRl'ORA TION
REGIONAL HYDROGEOLOGIC CROSS-SECTION A-A'
NEW HANOVER COUNTY AIRPORT SITE
WILMINGTON, NORTH CAROLINA • .ut.idiary of Camp Dr~Hct & McKee tnc.
--
J; 2 • ~ aa >
3 ~ "~ :§.~ e .! -a ~~ .s ,.
-
C a • u 0
~ C a "' ...
,:· . •
I!!!!!!!
A'
SOUTHEAST
50
-0
--50
CLA't, SAN
& MARL
-100
• • -150 t:,
z 0 ~ -200 ...J w
--250
--JOO
--J::>O
--400
FIGURE No. 1-4
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surface water features and through infiltration to lower aquifers. Regionally, aquifer
parameters measured in the surficial aquifer indicate a range of hydraulic conductivity -,;•
values from 14 ft/day to 697 ft/day, transmissivity values from 378 ff/day to greater
than 17,425 ft2/day, storage coefficient (specific yield) values from 0.15 to 0.5
(dimensionless), and specific capacity of well values from 0.1 to 69 gpm/ft of
drawdown (Bain, 1970).
The Castle Hayne limestone lies below the surficial aquifer. The limestone ranges
from 0 to 80 feet in thickness, but is generally less than 50 feet thick and in the
northwestern portions of New Hanover County, the limestone is thin to absent. The
formation is variable lithologically and is typically composed of four units. In
descending order, the units consist of an upper light-greeri glauconitic mixture of shell
fragments containing bryozoans, a "cap rock" of chalk-white siliceous limestone
containing phosphate at its base, a glauconitic shell limestone with interbedded sand,
and a basal sandy shell conglomerate. The entire formation lies unconformably on
the erosional surface of _the upper clay aquiclude of the Pee Dee Formation .. The
water in the Castle Hayne limestone occurs under water table conditions in the
northern sections of the county but may be confined beneath clay beds in other
sections of the county (Bain, 1970).
The groundwater flow direction in the limestone is southeast toward the Atlantic
Ocean in the eastern portion of the county and west toward the Northeast Cape Fear
River and the Cape Fear River in the western portion of the county. Recharge to the
limestone is through infiltration of water from the overlying surficial aquifer and
through direct infiltration of precipitation in the Wilmington and Castle Hayne areas·
where the limestone outcrops at land surface or the surficial aquifer is thin. Aquifer
parameters measured for the limestone indicated a range of hydraulic conductivity
values from 18.7 ft/day to 375 ft/day, transmissivity values from 935 ff/day to
18,750 ft2, storage coefficient values from 0.0001 to 0.25 (dimensionless), and
specific capacity of well values from 3 to 60 gpm/ft of drawdown (Bain, 1970).
1-12
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The sandstone aquifer of the Pee Dee Formation is a major source for drinking water
in New Hanover County. It is separated from the Castle Hayne limestone by the
; ..
upper clay aquiclude of the Pee Dee Formation. This aquiclude ranges in thickness
from O to 50 feet. The undifferentiated late tertiary and surficial deposits lie
unconformably on the sandstone aquifer in the northwest areas of the county due to
the slight dip of the sandstone aquifer towards the Atlantic Ocean and an erosional
surface at the top of the aquifer. The aquifer is 35 feet in thickness throughout much
of the county and is composed mainly of quartz sands bound with a calcareous
cement. The aquifer is underlain by 150 feet of silt and clay. This silt and clay
forms an aquiclude that separates the sandstone aquifer from saline aquifers below.
Water in the sandstone aquifer occurs under artesian conditions due to the aquicludes
above and below. Recharge to the aquifer occurs through leakage from the upper
aquiclude and from the undifferentiated late tertiary and surficial deposits where they
overlay the aquifer.
Groundwater flow direction in the sandstone aquifer is toward the Atlantic Ocean in
the eastern part of the county and toward the Northeast Cape Fear River and the Cape
Fear River in the western part of the county. Discharge from the aquifer occurs
along the major stream valleys and through upward migration of water through the
upper beds along the Atlantic Coast (Bain, 1970). Aquifer parame_ters measured in
the sandstone aquifer indicate a range of hydraulic conductivities values from
28 ft/day to 268 ft/day, transmissivities values from 600 ff/day to 10,720 ft2/day,
storage coefficient values from 0.001 to 0.5 (dimensionless), and specific capacity of
wells from 0.3 to 34 gpm/ft of drawdown (Bain, 1970).
1.3.4 SITE HYDROGEOLOGY
The site-specific geology and hydrogeology of the New Hanover County Airport Bum
Pit Site has been investigated to a depth of 65 feet below land surface (bis) through
test borings and the installation of monitor wells. The investigations thus far have
1-13
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indicated three hydrogeologic units of concern beneath the site. These units include a
surficial silty ;;~d aquifer, a thin clay unit beneath the surficial aquifer, and a lower
sand and limestone aquifer. A site hydrogeologic cross-section B-B' located on
Figure 1-5 and shown in Figure 1-6 indicates the hydrogeologic units encountered
beneath the site during investigative activities. Geologic logs of the test borings and
monitor wells shown in the cross-section are given in Appendix A.
The surficial aquifer at the site, composed predominantly of silt has a thickness
between 25 and 31 feet throughout the site. Recharge to the aquifer occurs through
the direct infiltration of precipitation. All temporary piezometers, observation wells,
and monitor wells at the site have been installed in the surficial aquifer. Water level
contour maps generated from water level data collected from the wells consistently
indicate a groundwater mounding effect in the center of the site. Water level contour
maps generated from April 9, 1991, April 17, 1991 and May 7, 1991 water level data
are shown in Figures 1-7, 1-8, and 1-9, respectively. Water level data and well
construction details are shown in Table 1-1. The contours in Figures 1-7, 1-8, and
1-9 indicate an average hydraulic gradient across the site of 0.0015 ft/ft and a
groundwater flow direction radially out from the center of the site. Average aquifer
characteristics determined through an aquifer performance test performed in the
aquifer on May 8, 1991 indicate that the aquifer has an average transmissivity (I) of
146 ft2/day, an average storage coefficient (S) of 0.0063 (dimensionless), and an
average hydraulic conductivity (K) of 6.6 ft/day.
The unit beneath the surficial aquifer is a firm blue~gray clay. The clay unit was
consistently encountered in all three test borings (TB-1, TB-2, and TB-3) and deep
monitor well MWD-001 at a depth of 25 to 31 feet bis. The thickness of the unit,
determined from test boring TB-1, the only boring to penetrate the entire thickness of
the unit, is 6 feet. Permeability testing and geotechnical testing of a sample of the
clay obtained from the well boring of MWD-001 classify the clay as a sandy clay
with liquid limits of 34, a plastic index of 12, and a permeability of 2.03 x 10-7
1-14
NHANFS09.013
LEGEND
----BERM/ROAD ----
JTT1"""""'"rrr EXCAVATION
111!111 POSSIBLE SURFACE WATER
DRAINAGE AREAS ... TEMPORARY PIEZOMETER
6 OBSERVATION WELL
• SHAU.OW MONITOR W[l.t.
@ OF.EP MONITOR W[ll
.ii l[Sf BORING
ARMY CORPS
OF ENGINEERS
UST FARM
Wl-2
If
TO WILM/NG/ON
SITE HVDROGEOLOGIC CROSS-SECTION LOCATION MAP
NEW HANOVER COUNTY AIRPORT.BURN PIT SITE
• ,11t..idiuy of Camp Dn:11cr & McKee Inc.
CDM FEDERAi. PROGRAMS CORPORATION WILMINGTON, NORTH CAROLINA
0 100
APPROXIMATE
SCALE IN FEET
200
FIGURE No. 1-5
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z 0 ;= < >
B'
SOUTHWEST
40
30
20
~ 0 ------------------------------w _-_. = -----_-_-_-_-_-_-_-_-_-_-_--_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_------=--=---c'-=--=,
-10
-20
-30
LEGEND
I :;j SILTY SANO
D CLAY
□ BLUE -GRAY CLAY
MEDIUM TO COARSE SANO
SANDY FOSSILIFEROUS
LIMESTONE
B
NORTHEAST
40
30
20
10
0
-10
-20
-30
□ FINE SANO
POTENTIOMITRIC SURFACE
IN THE SURFICIAL AQUIFER
(May 7, 1991) 50 0 50
HORl20NTAL
SCALE IN FEET
SITE HVDROGEOLOGIC CROSS-SECTION B-8'
-NEW HANOVER COUNTY AIRPORT BURN PIT SITE -=-==-----------"
"ll e;,
z 0 ;= < > ~ w
CDM FEDERAL PROGRAMS CORPORATION WILMINGTON, NORTH CAROLINA
• ~blidiary of Camp~-& Mc!Cu Inc. FIGURE No. 1-6
--- - - - - - - - - - - -!!!!!!!!!I !!!!!!! !!!!!I == ;;;;;; liiiii
LEGEND
fTTlllilllliliilll!I
111111111
...
0
BERM/ROAD
EXCAVATION
POSSIBLE SURFACE WATER
DRAINAGE AREAS
TEMPORARY PIEZOMETER
OffSITE MONITOR WELL
,-27.J-'
, .. 21.J .. ,
WATER LEVEi. CONTOUR {fl. AMSL)
EXTRAPOLAIE □ WATER lEVEL
CONTOUR (11. AMSL)
0 SFC-001 {Approximate location)
iU
ARMY CORPS
OF ENGINEERS usr ,-ARM
CDM. FEDERAL PROGRAMS CORPORATION
• 1~t.idiary of Camp On::sacr & McKee b,c.
10 W//.MINGTON
WATER LEVEL ELEVATIONS -April 9, 1991
NEW HANOVER COUNTY AIRPORt BURN PIT SITE
WILMINGTON, NORTH CAROLINA
100 =---0 100
APPHOXIMAT[
SCALE IN FE[r
200
FIGURE No. 1-7
- - - - - - - - - - - - --I!!!!!!!!! !!!!!I !!!II == =a
----BERM/ROAD ----
,T11llliliHIJi11ll! EXCAVATION
111111111 POSSIBLE SURFACE WATER
ORAINAGE AREAS
• SHALLOW MONITOR WELL
@ DEEP MONITOR WELL
0 orrsrrE MONITOR WELL
,-27.J-' WATER LEVEL CONTOUR (ft.
,-27.3-' EXTRAPOLATED WATER LEVEL
CONTOUR (IL AMSL)
0 SFC~001 {Approximate location)
iU
ARMY CORPS
OF ENGINEERS
UST I-ARM
I
'
CDM FEDERAL PROGRAMS CORPORATION
a 111baidiary of Camp Dn:ncr & McKee Inc.
AMSL)
/,
// I I 1/
//
I
TO W/lMINGTON
WATER LEVEL ELEVATIONS -April 17, 1991
NEW HANOVER COUNTY AIRPORT'BURN PIT SITE
WILMINGTON, NORTH CAROLINA
100 0 100
~
APPROXIMATE
SCALE IN F[[f
200
FIGURE No. 1-8
- - - - --------
LEGEND
----BER"/ROAD ----
fTTl""'"""""r EXCAVATION
l!lllllll POSSIBLE SURFACE WATER
DRAJNACE AREAS
8 OBSERVATION WELL
• SHALLOW MON\TOR WELL
@ DEEP MONITOR WELL
0 Of FSlf[ MO NII OR WELL
,--21.J-' WAl[R LEVEL CONTOUR (It. AMSL)
.,. -27.3 .. , EXTRAPOlATfO WAH:R LEVEL .
CONIOUR (It. AMSL)
0 SFC-001 (Approximate location)
ARMY CORPS
OF ENGINEERS
UST FARM
COM FEtn;RAt. PR<K;RAMS CORPORATION
a suboidiary or Camp Drcucr &. Md{cc Inc.
TO WILMINGTON
WATER LEVEL ELEVATIONS-May 7, 1991
NEW HANOVER COUNTY AIRPOR"t° BURN PIT SITE
WILMINGTON, NORTH CAROLINA
I!!!!!!!!!! I!!!!! 1!!!!115 i:=
"!' . •
1 o._o...__....'oiiiilo~=='.10..,0==~200 ~--===
APPROXIMATE
SCAL[ IN F[ET
FIGURE No. 1-9
- - - -
Permanent Wells
MWS-001
MWD-001
MWS-002
MWD-002
MWS-003
MWS--004
Temporary Wells
WL-1
WL-2
WL-3
WL-4
WL-5
WL-o
WL-7
WL-8
OW-1
OW-2
OW-3
OW-4
OW-5
NQTI§:
• Above Mean Sea Level
-Not Available
14.88
27.81
14.88
27.42
15.01
14.96
- - -
14.7-4.9
27.6-17.9
14.7-4.9
27.2-17.5
14.8-5.1
14.8-5.0
- - -- -
TABLE 1-1
WELL CONSTRUCTION AND WATER LEVEL DATA
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
33.99 31.16
6.20 33.50 31.10
5.72 33.34 30.51
5.72 5.68 33.27 30.48
5.84 5.94 33.31 30.61
4.94 5.04 32.33 29.58
--1!!1!!11 I!!!!!!!! ~ !!!I! ==
27.30
27.62
27.55 27.59
27.47 27.37
27.39 27.29
28.47
28.15
28.46
28.00
28.11
28.18
28.52
28.39
27.30
27.31
27.32
27.44
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cm/sec. The clay unit is expected to slow or impede contaminant migration from the
upper surficial aquifer to the lower sand and limestone aquifer.
';•
The sand and limestone aquifer below the clay unit is thought to be the Castle Hayne
Limestone Formation. The boring log of test boring TB-1 indicates that below the
clay unit there is a 5.5-foot thick layer of fine sand from 34.5 to 40 feet bis, a 2-foot
layer of sand and clay lenses from 40 to 42 feet bis, and an 18-foot thick layer of
medium to coarse sand from 42 to 60 feet bis. A sandy fossiliferous limestone was
encountered to 60 feet bis. The boring was terminated while still in the limestone at
65 feet bis. Because aquifer testing has not been performed in the lower aquifer, its
characteristics are unknown.
1.4 RESULTS OF PREVIOUS INVESTIGATIONS
1.4.1 REMEDIAL INVESTIGATION
A remedial investigation (RI) was conducted by EPA in 1991. Preliminary
remediation goals (PRGs) were developed for the site by EPA, setting compound-
specific concentration goals for site contaminants. PRGs were established for
groundwater and soil. The soil PRGs were intended to be protective of exposure via
both air and soil ingestion pathways. These criteria were used to determine if
contaminated soils had been completely excavated.
Based on the results of previous soil and groundwater confirmation sampling, it was
determined that all the soils above the PRGs had been removed and that the extent of
contaminated groundwater required further delineation. Additional temporary monitor
wells were installed and sampled to determine the placement of the permanent
monitor wells. Six permanent monitor wells were installed and sampled in April of
1991. On April 9, 1991, five soil samples, both surficial and subsurface, were
collected in this first round; on April 17, 1991, a second round of samples was
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collected and analyzed for VOCs in groundwater only. As a result of the
recommendations presented in the RI (EPA, 1991), EPA obtained a third round of ~·
groundwater samples from the site on May 7, 1991. These samples were collected to
determine baseline conditions at the site since previous groundwater samples were
obtained when the site had not yet stabilized from the installation and development of
the monitor wells. A summary of all the groundwater sampling results, including
each sampling round, is presented in Table 1-2. Analytical results for groundwater
samples from all three sampling rounds are presented in Appendix B.
1.4.2 BASELINE RISK ASSESSMENT
FPC conducted a human health and ecological assessment in April 1992 to assess the
potential risk from exposure to chemicals at the New Hanover County Airport Bum
Pit Site. The baseline risk assessment evaluated current conditions in the absence of
any further remedial action at the site. Since the PRPs for this site have completed
permanent remedial activities to remove contaminated soil and other waste materials,
the risk assessment addressed only post-remediation conditions for the site.
Human health risk was quantified for the present baseline conditions. Since there are
residents within a three-mile radius of the New Hanover County Airport Bum Pit Site
who obtain drinking water from private wells, and other area residents who obtain
drinking water from a local community well system, the potential exists for migration
of contaminants from the site to private drinking water wells. Although no drinking
water wells have been found to be impacted by groundwater contamination from the
site, the risk assessment quantified the future potential exposure to local residents via
consumption of contaminated drinking water and inhalation of contaminant vapors by
showering.
Soil, surface water, and fugitive dust are not expected to be significant pathways of
exposure at the New Hanover County Airport Bum Pit Site in its present condition.
1-22
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TABLE 1-2
GROUNDWATER DATA SUMMARY
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
Inorganic Elements
Aluminum 13/14 23,479.2 58,000.0
Barium 12/14 155.7 410.0
Beryllium 1/14 1.4 1.4
Calcium 14/14 15,835.7 38,000.0
Chromium 13/14 41.6 82.0
Cobalt 1/14 2.2 2.2
Copper 12/14 9.4 21.0
Iron 14/14 IS, 151.6 40,000.0
Lead 1/14 22.0 22.0
Magnesium 13/14 4,433.1 12,000.0
Manganese 13/14 153.1 490.0
Molybdenum 2/14 2.7 2.7
NOTES:
"Treatment technique action level (EPA, 1991).
References: 'North Carolina Administrative Code (!SA NCAC !SC. 1500), j9g9_
'Safe Drinking Water Act, EPA, 1991.
1,000
50
1,000
300
50
50
50-200
1,000
I
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1,300"
300
15"
50
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Nickel 12/14
Potassium 12/14
Sodium 14/14
Strontium 13/14
Titanium 14/14
Vanadium 13/14
Yttrium 7/14
Zinc 14/14
Purgeable Organic Comoounds
Benzene 12/20
Carbon Disulfide 1/20
Chloroform 8/20
1,2-Dichloroethane 2/20
Ethylbenzene 12/20
NOTES:
"Treatment technique action level (EPA, 1991).
33.2
4,356.7
82,505.0
199.6
107.8
33.7
10.4
27.7
46.8
1.8
1.9
3.6
17.9
TABLE 1-2
( continued)
110.0
11,000.0
260,000.0
640.0
310.0
73.0
17.0
62.0
110.0
1.8
3.4
4.4
43.0
'
References: 'North Carolina Administrative Code (ISA NCAC !SC. 1500), 1989.
2Safe Drinking Water Act, EPA, 1991.
150 100
5,000 5,000
5
0.19 100
0.38 5
29 700
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Toluene 9/20
Xylenes, total 13/20
Extractable Organic
Compounds
2,4-Dimetbylphenol 6/14
Methyl ethyl ketone 1/14
2-Methylnaphthalene 3/14
3-or 4-Methylphenol 1/14
2-Methylphenol 4/14
Naphthalene 5/14
NOTES:
'Treatment technique action level (EPA, 1991).
5.2
28.3
27.5
64
13.7
2.9
4.4
13.9
TABLE 1-2
( continued)
14
82
54
64
19
2.9
6.1
21
References: 'North Carolina Administrative Code (15A NCAC !SC. 1500), 19°89.
'Safe Drinking Water Act, EPA, 1991.
1,000
400
170
1,000
10,000
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••
Contaminated soil has been removed to achieve the PRGs established for the site,
limiting the potential for re-entrainment of contaminated dust or direct contact with
contaminatef soils. In addition, there are no permanent surface water bodies at the
site.
The chemicals of concern in groundwater at the site are benzene, beryllium,
chloroform, chromium, 1,2-dichloroethane, and lead due to toxicity, frequency of
detection, and exceedance of water quality standards. Tentatively identified
compounds (TICs) were not evaluated quantitatively since there is a lack of certainty
in identification and absence of critical toxicity values (i.e., reference doses and slope
factors).
Based on the human health risk assessment, the estimated carcinogenic human health
risk for benzene, chloroform, 1,2-dichloroethane, and beryllium is 1 x 104, which is
at the upper end of the acceptable risk range of 1 x 104 to 1 x 10~ as established by
EPA. The estimated carcinogenic risk is the summation of ingestion and inhalation
risks following exposure (FPC, 1992). Since chromium is not expected to volatilize,
and is not expected to be a carcinogen through ingestion, a carcinogenic human health
risk was not calculated for this chemical. Also, since toxicity criteria are not
available for lead, a carcinogenic human health risk was not calculated for this
chemical either.
An endangered species survey performed at the site did not identify the presence of
endangered species of flora or fauna. Species diversity was limited due to poor
habitat suitability. The dominant observed fauna onsite were opossum, lizard, and
perching/songbird species. Flora diversity is typical for a coastal range area that has
undergone significant disturbance, remediation, and subsequent revegetation. No
endangered flora species were identified onsite (FPC, 1992).
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1.5 SITE RESTORATION OBJECTIVES FOR GROUNDWATER
1.5.l CLEANUP CRITERIA
To obtain cleanup criteria for the New Hanover County Airport Bum Pit Site, FPC
used the applicable or relevant and appropriate requirements (ARARs) for this site,
includin~ the North Carolina Drinking Water Quality Standards and federal Safe
Drinking Water Act (SOWA) Maximum Contaminant Levels (MCLs), for each
chemical of concern. The most conservative of these values were selected as the site-
specific cleanup goals as previously presented in the risk assessment (FPC, 1992). In
addition, human ingestion and inhalation risks were estimated for each selected
cleanup goal. Table 1-3 summarizes the ARARs for the site, the cleanup criteria,
and the estimated risks for each cleanup goal.
1.5.2 EXTENT OF GROUNDWATER CONTAMINATION
The extent of groundwater contamination is a combination of the three separate
plumes for benzene at l µg/1, chromium at 50 µg/1, and chloroform at 0.19 µg/1 as
shown on Figures 1-10, 1-11, and 1-12, respectively. Because lead and beryllium
were each found in well MWS-001 in one sampling round only, and 1,2-
dichloroethene was detected only in MWD-002 in two sampling rounds (and since
these two wells are .within the total areal extent of groundwater contamination),
specific plumes were not estimated for these compounds. The approximate horizontal
extent of contamination was estimated by overlaying the individual contaminant
plumes for benzene, chromium, and chloroform and is shown on Figure 1-13. The
vertical extent of contamination extends throughout the 28 feet of the surficial aquifer.
The most conservative ARARs were selected to estimate the contaminant plumes for
each chemical of concern. Contaminant plume aerial extents were extrapolated
toward the north, east, and west of the bum pits due to lack of groundwater quality
1-27
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Organics
Benzene
Chloroform
1,2-Dichloroethane
Inorganics
· Beryllium
Chromium
Lead
TABLE 1-3
SUMMARY OF ARARs AND CLEANUP CRITERIA
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
I 5 I
0. 19 100 0.19
0.38 5 0.38
1-I
50 50 50
50 15• 15
NOTES:
• Treatment technique action level (EPA, 1991).
Proposed MCL.
Not Available.
3xJO·'
Ix 104 .
4xJO·'
5xJO·'
• ---
• ---
'Chromium is not expected to volatilize during showering, and is not considered a carcinogen by the
oral route. No remedial goal.is appropriate for chromium-based noncarcinogenic risks.
"Toxicity criteria are not available to derive a remediation goal.
References: 'North Carolina Administrative Code (15A NCAC 18C. !500), 1989.
'Safe Drinking Water Act (EPA, 1991).
'FPC, 1992.
1-28
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iU
LEGEND
rnn1111111111nrrr
•
@
NO
,-25.5_,,,
.. -25.5-'
BERM/ROAD
EXCAVAllON
POSSIBLE SURrACE WATER
ORl<NAGE AREAS
TEMPORARY MONITOR WELL
SHALLOW MON!TOR WELL
DEEP MONITOR WELL
ESTIMATED YALU[
NOT O[T[CTED
CONCENTRATION CONTOUR ("g/1)
EXTRAPOLATfD CONTOUR ("g/1) /,
// I I 1/
II
I
ARMY CORPS
OF ENGINEERS
UST FARM
NOT(: 1 ug/l is \he North Carolina
Water Quality Standard. TO WILMINGTON
100 0 100 ~--==
APPROXIMATE
SCALE IN F[F.f
EXTENT OF BENZENE CONTAMINATION IN THE SURFICIAL AQUIFER (ug/1)
NEW HANOVER COUNTY AIRPORT'BURN PIT SITE
200
CllM l'EllERAI. PRIK~RAMS CORPORATION
a 1ubaidiary of Camp lmuc, & McKee Inc. WILMINGTON, NORTH CAROLINA FIGURE No. 1-10
- - - - - - - - - - - - - - --l!!!!!!!!I l!!!!!!!!I !!!!I
LEGEND
---~ BER"/ROAD ----
fTTI\ILllllllii/Jtrr EXCAVATION
lillllil POSSIBLE SURFACE WAIER
DRAINAGE AREAS
0 TEMPORARY MONITOR WELL
• SHALLOW MONITOR Wfll
@ OEEP MONHOR WELL
NA NOT ANALY/[D
,-50_.,,, CONC[NIRAIION CONIOU!l (cg/I)
,-50-"" [XIRAPOLAIED CONJOUR (cg/I)
ARMY CORPS or ENGINEERS
UST I-ARM
NOTE: 50 ug/1 is the SOWA MCL.
TO WILMINGTON
100
~
0 100
APPROXIMAIE
SCALE IN FEE f
200
APPROXIMATE EXTENT OF CHROMIUM CONTAMINATION IN THE SURFICIAL AQUIFER (ug/1) ~ NEW HANOVER COUNTY AIRPORT·BURN PIT SITE
COM FEDERAL PR()(;RAMS CORPORATION
• .ublidiary of Camp Drcucr& Md(cc Inc. WILMINGTON, NORTH CAROLINA FIGURE No. 1-11
- - - - - - - - - - - - - - - -I!!!!!!!!! I!!!!!!!!! !!!!!!!!
LEGEND
nn"""""""'r
ND
.,,.....0.19,.,,,,,
.... 0.19 .. ,
BERM/ROAD
EXCAVATION
POSSIBLE SURFACE WATER
DRAlNAG[ AREAS
TEMPORARY MONITOR WELL
SHALLOW MONITOR WELL
DEEP MONITOR WELL
ESTIMAIEO VALU[
NOT D[l[CTED
CONCENTRATION CONTOUR (,g/1)
EXIRAPOLATED CONTOUR (,g/1) /,
// I I 1/
II
I
ARMY CORPS
or ENGINEERS
LISI rARM
NOTE: 0.19 ug/1 is lhe North Carolina
Water Quality Standard.
f)
10 WILMINGTON
100 0 100 200
~l!"'=l!"'=l!"'l!"'==l!"'l!"'""'I!"'!
APPROXIMATE
SCALE IN FEET
APPROXIMATE EXTENT OF CHLOROFORM CONTAMINATION IN THE SURFICIAL AQUIFER (ug/1)
.. . NEW HANOVER COUNTY AIRPORTBURN PIT SITE
CUM FEDERAL l'R(K;RAMS CORPORATION
a au bl id.ivy of Camp Dn::1""r & McKee Inc. WILMINGTON, NORTH CAROLINA FIGURE No. 1-12
P:::;::;--v-- - - - - - - - -. - - -11!1 I!!!!!!! !!liiil == =-iiii
LEGEND
rrrr•""'"""'"r
11!1111
0
•
@
,--'
BERM/ROAD
EXCAVATION
POSSIBLE SURFACE WATER
DRAINAGE AREAS
TEf.APORARY MONITOR WELL
SHALLOW MONITOR WELL
DEEP MONITOR WELL
APPROXIMATE LIMITS Of
GROUNOWAl[R CONTAf.llNATION
ARMY CORPS
OF ENGINEERS
UST FARM
I
'
100
fj I"!"'! -
10 WILMINGTON
0 100
APPROXIMATE
SCALE IN FEET
APPROXIMATE TOTAL EXTENT OF CONTAMINATION IN THE SURFICIAL AQUIFER
NEW HANOVER COUNTY AIRPORT· BURN PIT SITE
200
CDM FEDERAL PROGRAMS CORPORATION WILMINGTON, NORTH CAROLINA FIGURE No. 1-13
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data in this area. To better refine the extent of contamination, several additional
monitor welts. should be installed on the north, east, and west sides of the bum pits.
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2.0. IDENTIFICATION, SCREENING, AND EVALUATION OF
TECHNOLOGIES AND PROCESS OPTIONS
This section presents the identification and screening of corrective action technology
types and process options applicable to the New Hanover County Airport Burn Pit
Site. The area to be addressed through groundwater remediation (discussed in
Section 1.5) was considered throughout the development of applicable technologies.
Potential technologies for long-term extraction, treatment, containment, and discharge
were identified and screening was conducted to eliminate infeasible or impractical
extraction, treatment, containment and/or disposal options.
General response actions for groundwater remediation include several extraction,
treatment, containment, and disposal options. Technologies within these categories
have been considered for dissolved constituents in groundwater at the site. A
preliminary screening of technologies was conducted on the basis of technical
implementability by reducing the universe of potentially applicable technologies.
Those technologies that can be technically implemented at the site were further
evaluated on the basis of effectiveness, implementability, and cost.
Those technologies retained for groundwater remediation at the site have been
combined to form site-wide remedial action alternatives, which are presented in
Section 2.4 and discussed in detail in Sections 3.2 through 3.6.
2.1 SCREENING OF GROUNDWATER TECHNOLOGIES
AND PROCESS OPTIONS
The preliminarily identified technology types and process options applicable to
groundwater remediation at the New Hanover County Airport Burn Pit Site are
presented in Table 2-1. As shown, several entire technology types and process
2-1
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Gl'Ollndwater General
Response Actions Remedial Technology
TABLE 2-1
INITIAL SCREENING OF TECHNOLOGIES AND PROCESS OPTIONS
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
Process Option Description
LI _No_~_tio_n __ ~HL_No_n_e _____ _,.._--""!__N_ot_appl.c.:.._icabl __ • _____ _, No action
lnslitutional
actions
Containment
CoDection
Treatment
/589 next page I
Discharge
/589 nsxt page I
Access restrictions
Monitoring
--• Vertical barriers
-...--1 Extraction
(S89 ooxt page}
----1 Deed restrictions
---• Groundwater monitoring
Slurry wall
Grout curtain
Sheet pililg
Extraction weDs
! '? ;:,:j Process option eliminated from further consideration
Deeds for property in the area of influence
would include restrictions on wells
Ongoing monitorilg wells
T ranch around areas of contamination is filled
with a soil (or cement) bentonite slurry lo form
an impermeable barrier
Pressure injection of grout in a regular pattern
of drilled holes to form an impermeable barrier
Lengths of steel sheels are connected together
and driven Into lhe ground to form an
impermeable barrier
Series of wells to extract contaminated
groundwater
Injection wells Inject uncontaminated
water to lnaease flow to extraction wells
Perforated pipe in trenches backfilled with
porous meda to collect contaminated water
System of Injection and extraction wells Introduce
bacteria and nutrients to degrade contamination
System of wells to inject air Into groundwater to
remove volatiles by air stfWing
Downgradilnl trenches backfilled wilh activated
carbon to remove contaminants from water
System of lnjeclioo wells to inject oxidizer such
as hymogen peroxide to degrade contaminants
!!!!!!ii
Screening Comments
Reqlired for consideration by NCP
Potentially applicable
Potentially applicable
Potentially applicable
Potentially applicable
Potentially applicable
Potentially applicable
Not feasible because NCDNR
prohibils injection wells
,, .. •
iiii -
Nol feasible for intercepting contaminated
groundwater because of vertical depth
of 28 feet bis
Nol feasible because of low concentrations of
organic contaminants and ineffectiveness In
removing inorganic contaminants
Nol feasille because of potential for volalizing organic
contaminants and recontaminating dean soils and
ineffectiveness in removing inorganic contaminants
Nol feasille because of lneffeclivell9SS In removing
inorganic contaminants
Not feasille because of polential for volalizing organic
contaminants and recontaminating dean soils and
ineffectiveness in removing inorganic contaminants
- - - - -
Groundwater General
Response Actions Remedial Technology
Collection (see
pmvious page}
Treatment/see
pmvious page)
PhysicaVChemicaf
1-.... -treatment
Discharge
Offsite treatment
Onsite discharge
Offsite discharge
- - -
Process Option
Precipitation
Air Stripping
Hazardous Wastewater
Treatment Facility (TSD)
Spray irrigation
POTW
Plpeline to surface wa!Br
h's .,,,q Process option eliminated from further consideration
-- - - - -
-I!!!! ==
TABLE 2-1 (Continued)
Description Screening Comments
Aiteration of chemical equilibria to reduce
solubility of the contaminants
Mixing large volumes of air with water in a
packed column to promote transfer of VOC's to air
Adsorption of contaminants onto activated carbon
by passing water through carbon column
Potentially applicable
Potentially applicable
Potentially applicable
Use of high pressure to force water through a Contaminanl concentrations too low for
membrane leaving contaminants behind treatment
Conlaminated water is passed through a resin bed Potentially applicable
where ions are exchanged betwoon resin and water
Reduction of Cr" to Cr' followed by Cr' removal
through hydroxide precipitation
Extracted groundwater transported to a TSD facility
for treatment
Degradation of 019anics using miaoorganisms
in an aerobic environment
Degradation of organics using miaoorganisms
in an aerobic environment
Injection wells inject extracted and treated
water into aquifer
Extracted and treated water discharged to
onsite infiltration basins
Extracted and treated water discharged through
perforaled pipe in trenches backfilled with
poroos media
Extracted and treated water discharged through
plant '4'taka and .....,,ation (evapotranspi'ation)
and percolation through soil
Extracted and treated wa!Br dischared to City of
Wilmington Northside POTW for treatment
Extracted and tre;!ted water discharged to
Smith Creek
Potentially applicable
Not feasble due to excessive cost
Not applicable as organic conlaminants are more
volatile than biodegradable at the site
Not applicable as organic contaminants are more
volalie than biodegradable at the site
Not feasible because NCDNR p,ohibifs
injection wells
Not feasible because of shallow groundwater
!able and expected mounding effects
Not feasible because of shallow groundwater
table and expected mounding effects
Potentially applicable
Potentially applicable
Potentially applicable
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options are eliminated from further consideration solely on the basis of technical
implementability or cost effectiveness at this specific site. The retained technologies
";•
are further evaluated in Section 2. 2.
The no action technology was retained to be combined with the groundwater
monitoring process option. The no action alternative is further evaluated in
Section 3.0. In addition, deed restrictions are also considered for each alternative
evaluated in Section 3. 0.
2.2 EVALUATION OF TECHNOLOGIES AND PROCESS OPTIONS
The following sections present a detailed description and an evaluation based on
effectiveness, implementability, and cost for each of the retained remedial
technologies and associated process options under the groundwater containment,
collection, treatment, and discharge response actions. ·
2.2.1 CONTAINMENT TECHNOLOGIES
The containment process options under evaluation consist of three types of vertical
barriers: slurry wall, grout curtain, and sheet piling. Because initial screening
indicated all three options are potentially applicable to the site, one will be selected
for the purpose of developing and evaluating site-wide alternatives. However, if an
alternative involving containment were to be selected for implementation at the site,
these process options should be evaluated in detail during the remedial design phase
of the project.
Slurry Wall
Containment of the contaminant plume can be achieved through plume encapsulation
by placing an impermeable slurry wall at the limits of the plume. In this method, a
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trench is excavated in the presence of a bentonite-water slurry beyond the depth of the
plume. After excavation is complete, the trench can be backfilled with a mixture of ~-the excavated material and bentonite, or a cement-bentonite mixture. This technique
is an effective method of creating an impermeable barrier to prevent further migration
of the contaminant plume. The slurry wall would have to extend over the entire
perimeter of the plume, approximately 1,600 feet in length, and to a depth of at least
30 feet bis. This approach can be implemented using standard .engineering techniques
and methods. An impermeable cap will be required in conjunction with the slurry
wall to minimize the potential of groundwater mounding at the site.
Grout Cunain
Because of the sandy soil conditions at the site, the grout curtain process option seems
to provide a viable alternative to the slurry wall and other vertical wall technologies.
However, because of the presence of the organic and inorganic contaminants in
groundwater, proprietary fixation chemicals would have to be injected to ensure the
presence of an impermeable barrier. This technology relies on boring head that
includes five in-line drill bits powered by submersible motors. The entire boring head
is suspended by cables from a conventional construction crane. The barrier wall
chemicals are supplied under low pressure through the auger head and mixed during
extraction. The low pressure prevents the grout outflow that is common with
conventional injection methods. An impermeable cap will be required in conjunction
with the grout curtain to minimize the potential for groundwater mounding at the site.
Because this technology is innovative with respect to the groundwater chemical
environment present at the site, the cost of implementing this technique would be very
high compared to that of a slurry wall. Therefore, the grout curtain process option is
eliminated from further consideration.
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Sheet Pilin~
This technology involves driving lengths of connected steel sheets into the ground to
form an impermeable barrier. Steel is the best form of sheet pile, compared to wood
and concrete) since corrosion has not been shown to be a factor in causing failures.
Initially, sheet piles are not totally impermeable; however, after a period of time,
gaps in the sheet pile connections are formed as fine particles in the groundwater clog
the gaps (Knox, R.C., et al., 1986). To date, use of sheet piling has been proposed
to control groundwater pollution, but few specific applications have been conducted
(Knox, R.C., et al., 1986). An impermeable cap would be required in conjunction
with the sheet piling to minimize the potential for groundwater mounding at the site.
Although sheet piling can be an effective technique for groundwater containment and
it could be easily implemented, its cost would be high when compared to the slurry
wall process option. Due to relatively high costs and a limited history of use, sheet
piling is eliminated from further consideration.
2.2.2 EXTRACTION TECHNOLOGY
Removal of the groundwater contaminant plume can prevent contaminant migration
offsite. The principal means of optimizing contaminated groundwater recovery is
through the alteration of the groundwater gradient to enhance and/or control
contaminant movement. This can be accomplished by placing an extraction system
downgradient of the contaminated area or artificially influencing an existing gradient
via groundwater extraction.
The reduction of contaminant concentrations over time is the primary indicator of the
effectiveness of an extraction system for aquifer restoration. The ideal scenario
would be a steady decrease in contaminant concentrations until the target level is
attained. However, performance records suggest that although concentrations may
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drop initially, decline is often followed by a leveling of concentrations with little or
no further dectease over time (EPA, 1989). . .
Extraction wells are commonly used as an extraction method to influence groundwater
flow and recover dissolved constituents. Extraction wells are used to contain the
migration of a contaminant plume or reduce its size, and would be located
downgradient of the original source area, surrounding the bum pits. In general,
extraction wells are versatile under a variety of site conditions and have design and
operating flexibility. Although single or multiple wells can be used to sufficiently
contain the spread of the dissolved constituent plume, multiple wells should be
positioned in such a way that the cones of influence overlap. Due to their ease of
installation, effectiveness at other groundwater remediation sites, and low capital and
maintenance costs, extraction wells will be retained for further consideration.
2.2.3 TREATMENT TECHNOLOGIES
A review of the retained process options, all of which are representative of
physical/chemical treatment technologies, was conducted to determine the most
appropriate treatment process for the removal of dissolved organic and inorganic
contaminants in the groundwater. As discussed previously in this report, the organic
chemicals of concern are benzene, chloroform, and 1,2-dichloroethane. Lead,
beryllium, and chromium are the inorganic chemicals of concern present in
groundwater at concentrations above cleanup criteria, although required removal
efficiency will be dictated by the selected discharge option. Applicable treatment
options include precipitation, air stripping, carbon adsorption, ion exchange and
chromium reduction, included as a contaminant-specific treatment option to enhance
removal of hexavalent chromium (Cr+6), in the event it is present at the site. These
process options are described and evaluated below. Because initial screening
indicated all five process options are potentially applicable to the site, specific
combinations of options will be selected for the purpose of developing and evaluating
2-7
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sitewide alternatives. However, if an alternative involving physical/chemical
treatment were to be selected for implementation at the site, these process options :;•
should be evaluated in detail during the remedial design phase of the project.
Precipitation
Precipitation involves the addition of a treatment chemical (i.e., sodium hydroxide,
calcium hydroxide, hydrochloric acid, sulfuric acid, sodium sulfide) to vary pH and
transform a contaminant from the dissolved to the solid (salt) form so that it can be
removed by clarification and/or filtration. Metals removal is the most common
application of the precipitation process. The treatment agent may chemically alter the
contaminant, or it may create a more rapidly settling material. In the case of metal
ions, a treatment chemical is added to the wastewater, forming relatively insoluble
compounds (generally hydroxides or sulfides) with the metal ions present. The degree
to which any dissolved metal is precipitated depends on the solubility of the resultant
metal hydroxide or sulfide (which is generally pH dependent) and on the pH at which
the process is operated. Usually, the insoluble compounds are then flocculated with
polyelectrolytes, to aid in clarification, and settled out of solution in a clarifier. A
properly designed and operated precipitation system can result in effluent metals
concentrations ranging from 10 to 100 µg/1, depending on influent loadings and the
solubility of the metal salt. Filtration reduces the levels even further by removing
residual suspended solids.
Since the treatment system at the New Hanover County Airport Burn Pit Site must
address three different metals (beryllium, chromium, and lead), bench-scale
treatability studies should be conducted to select the appropriate treatment chemical
and optimize the pH for effective removal of all three metals, to define design criteria
for darification and to determine if filtration will be necessary to meet discharge
limitations. Table 2-2 presents optimum treatment pH values for the metals of
concern at the site.
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TABLE 2-2
~• OPTIMUM TREATMENT pH VALUES
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
Beryllium
Chromium, trivalent
Lead
NOTES:
Insoluble1 Insoluble1
7.5 102 9.8 10.0
9 10 8 10
1Source: Choppin and Johnson, 1972.
2Considerable disagreement exists regarding the effect of pH on the solubility
of chromium hydroxide.
Source: J. W. Patterson, 1985.
2-9
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The precipitation process generates a significant volume of solids because it does not ~-
effectively distinguish between the chemical of concern and other easily precipitated
ions, such as calcium and iron. Proper management of these solids is necessary in
order to prevent short-or long-term negative impacts to the environment. Any design
must also include provisions for the proper handling of the treatment chemicals.
Precipitation (along with required clarification and filtration) is a proven technology in
removing the indicator metals at the site and is retained for further evaluation.
Air Stripoin~
Air stripping towers have been used effectively for removing of dissolved VOCs from
groundwater. A typical air stripping tower is shown in Figure 2-1. Contaminated
water enters the stripping tower at the top and is evenly distributed across the internal
packing media through distributor nozzles. Clean air is introduced into the bottom of
the tower below the packing using a .forced air blower, and flows upward through the
packing. As the falling contaminated water flows countercurrent to the rising air
stream, VOCs are stripped from the water and enter the air stream. These organics
are carried by the air stream out of the tower to the atmosphere. The internal packing
media acts to increase the total surface area available for mass transfer of the organic
contaminants from the liquid to the vapor stream. Treated water falls from the
packing into the stripper basin and exits the tower as contaminant-free water. Since
contaminant levels in groundwater are fairly low, it is likely that further treatment of
off-gases from air stripping will not be required; however, off-gas concentrations
should be calculated during the preliminary design stage to determine the need for
treatment in order to meet state and federal air quality regulations.
The extent of compound removal by air stripping is governed by many factors,
including contaminant concentrations in groundwater, air and water temperatures, the .
air-to-water ratio, and contaminant physical properties. One such physical property is
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WATER DISTRIBUTION
NOZZLES OR
DISTRIBUTION PLATE
PACKING MEDIA
AIR BLOWER
t TO ATMOSPHERE
INFLUENT WATER
FROM
CONTAMINATED
WELL
.,,..--TREATED WATER
TYPICAL AIR STRIPPING TOWER -NEW HANOVER COUNTY AIRPORT BURN PIT SITE
CDM FEDERAL PROGRAMS CORPORATION WILMINGTON, NORTH CAROLINA &Sllbsidiary ofCm!p DrCZIIIJ,l ~ !De. FIGURE No. 2-1
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the Henry's Law constant. Henry's Law states that the partial pressure of a
compound (a measure of the concentration in the gas phase) at equilibrium is equal to ,,.
a constant (Henry's Law constant) multiplied by the concentration of the compound in
the liquid phase. The Henry's Law constant is a partition coefficient that describes
the relative tendency for the compound to partition between the gas and liquid phases
at equilibrium conditions. The larger the Henry's Law constant, the greater the
equilibrium concentration of the contaminant in the air phase. High Henry's Law
values indicate compounds that are more easily removed from solution than those
having lower values. Volatile compounds typically have dimensionless Henry's Law
constants greater than 0.1 (Patterson, 1985).
The Henry's Law constant for both benzene and 1,2-dichloroethane is 0.23 and for
chloroform is 0.14 (Patterson, 1985). As shown in Table 2-3, benzene, chloroform,
and 1,2-dichloroethane should be easily removed by air stripping due to high Henry's
Law constants.
Air stripping tower performance also depends largely on the presence or absence of
various inorganic compounds and suspended solids in the groundwater. Groundwaters
with elevated hardness will result in calcium and magnesium salt deposits in the tower
packing media. Elevated iron concentrations, when oxidized in the air stripper, will
result in iron hydroxide precipitation, which can severely foul the packing media and
reduce its effectiveness to remove VOCs. In addition, elevated total suspended solids
(TSS) concentrations in the groundwater can also result in solids deposition on the
tower packing and reduce liquid-to-air mass transfer. Groundwater at the New
Hanover County Airport Burn Pit Site apparently contains relatively high
concentrations of iron (up to 40 ppm have been reported in site monitor wells) and
may contain moderately high concentrations of TSS, which are unreported for the
site. The use of air stripping would require pretreatment to remove iron and TSS.
2-12
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TABLE 2-3 ..•
HENRY'S LAW CONSTANTS FOR VOLATILE COMPOUNDS OF CONCERN
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
Benzene
Chloroform
1,2-Dichloroethane
NOTES:
0.23(1)
0.14(2)
0.23(1)
en Source: James W. Patterson, 1985, pp. 320-322. ·
(2) Experimentally determined values (Moore, 1976).
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Pretreatment equipment could consist of clarification/equalization basins or
multi-medi\tilters to remove TSS followed by greensand filters to remove iron.
Multi-media filters remove suspended particles by filtration using several layers of
filter media, usually consisting of coarse anthracite coal above various gradations of
finer silica sand. When the filter bed becomes loaded with suspended matter, it is
backwashed with treated water to remove the solids deposited on the filter media. In
the case of greensand filtration, dissolved iron is oxidized to the insoluble iron
hydroxide form by contact with a chemically treated filter media called manganese
greensand. The insoluble iron hydroxide along with particulate iron in the
groundwater is then filtered by the greensand media, and removed by backwashing.
When the oxidizing capacity of the greensand media is exhausted, the filter bed is
regenerated with a weak potassium permanganate solution, thus restoring the
oxidizing capacity of the bed.
An alternative approach to pretreatment equipment may be the use of proprietary
chemical complexing agents that prevent iron from precipitating in the air stripping
tower combined with more innovative "lower profile" towers and/or trayed towers
that reduce the total surface area available for fouling. In these stripping towers,
slotted trays and/or customized baffles are used to achieve the appropriate liquid-to-air
mass transfer instead of conventional packing media. The need for pretreatment
should be explored during the remedial design phase and the appropriate combination
of pretreatment steps identified.
Air stripping is an effective and relatively low-cost process option to remove VOCs
from groundwater and is therefore retained for further discussion.
Carbon Adsorption
A second process option for organics removal from groundwater is activated carbon
adsorption. This option is widely used for the removal of both volatile
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and non-volatile organic compounds. Activated carbon adsorption is most often
carried out i1!.,a pressurized vessel that contains a bed of granular activated carbon.
Figure 2-2 shows a typical activated carbon filter. Contaminated water enters the
pressurized vessel at the top and is evenly distributed over the granular activated
carbon. As contaminated water flows downward through the activated carbon media,
organic compounds are adsorbed onto the microporous surfaces of the activated
carbon by an electrical attraction. When the microporous surfaces of the carbon
become saturated with adsorbed organics, the carbon must be replaced with new or
thermally regenerated carbon media. Operating time before carbon exhaustion is a
function of both the flow rate and the concentration of organic compounds in the feed
stream. Treated water flows through a header and lateral collection assembly
positioned at the bottom of the vessel and then exits the carbon filter.
Activated carbon adsorption is a surface attraction phenomenon influenced by several
factors. These include physical properties of the carbon and contaminant compounds
and.system characteristics such as dissolved solids concentration, water temperature,
and pH. The combined quantitative effect of all these factors can be expressed by the
_ Freundlich adsorption equation, in which the amount of compound adsorbed per unit
mass of carbon is equal to a constant (K) multiplied by the final concentration of the
compound after treatment and raised to the power of another constant (n). Both K
and n, known as Freundlich parameters, are determined empirically on a
compound-specific basis. K is an approximate indicator of adsorption capacity and n
of adsorption intensity. Table 2-4 shows the Freundlich adsorption parameter K for
the contaminants of concern at hypothetical contaminant concentrations of 1.0 mg/I
and a neutral pH.
The performance of activated carbon filters depends in part on the concentration of
suspended solids in the influent stream. High concentrations of suspended solids and
oxidized iron, if not removed, will plug the carbon media and negatively affect
system hydraulics. As a result, multi-media filtration or clarification/equalization to
2-15
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MANWAY
CJ.
,
/
EFFLUENT
HEADER AND
LA TI:RALS
.. -.,,. ..
GRANULAR
ACTIVATED
CARBON
MEDIA
Gfi.AVEL
Sl?PORT
BED
ROCK
SUPPORT
BED
CONTAMINATED
WATER IN
TYPICAL ACTIVATED CARBON FILTER
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
CDMFEDERALPROGRAMSCORPORATION WILMINGTON, NORTH CAROLINA FIGURE No. 2·2
•
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TABLE 2-4
FREUNDUCH PARAMETER K VALUES FOR CONTAMINANT COMPOUNDS
• NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
Benzene
Chloroform
1,2-Dichloroethane
NOTES:
J.Q(l)
2.6(2)
3.6(1)
oi Source: James W. Patterson, 1985, pp. 331-333.
C2l Source: EPA, 1980.
NA -Not available.
2-17
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remove suspended solids may be required as pretreatment to activated carbon. In
some cases, [lirther filtration using in-line cartridge filters may be required to remove
smaller suspended matter. The cost involved in changing out the carbon at bed
exhaustion and disposal of the spent carbon as hazardous waste are negative impacts .
of using activated carbon as a process option.
Due to relatively high K values (>0.1) shown for the contaminants at the site, it is
expected that activated carbon would be an effective groundwater treatment technique.
However, due to relatively high O&M costs when compared to air stripping and
because the organic contaminants at the site would be more readily volatilized than
adsorbed, for the purposes of alternative evaluation, carbon adsorption will be
dropped in favor of air stripping for organics removal.
Ion Exchanee
Ion exchange treatment uses resins to remove dissolved metals and other inorganic
compounds from aqueous streams. Contaminant ions removed from the aqueous
solution are replaced with relatively harmless ions held by the exchange resins.
Specific ion exchange and sorptive resin systems are designed on a case-by-case basis.
The ion exchange would occur in a pressurized vessel where the matrix of the ion
exchange resins react with the contaminated water. The reactions continue until the
resins and the solution (water) in which the resin is immersed all reach equilibrium;
and consequently, the resins remove the metals. Resins lose their exchange/sorptive
abilities as they become saturated, and after a period of time, they must be
regenerated. Regeneration is a process whereby a resin-specific solution is passed
through the column, exchanging one ion (such as sodium or hydrogen) for the
contaminant ion. Significant amounts of this regenerant solution must then be
disposed of, typically as a hazardous waste. This technology is applicable for the
removal of contaminants from dilute solutions. High concentrations, however, rapidly
exhaust the resins and require frequent regeneration.
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Selective ion exchange using a special exchange resin is an effective option for
chromium (c;r+• and cr+3) removal and lead removal at the New Hanover County
Airport Burii"Pit Site. Significant experience using ion exchange to remove low
levels of beryllium from groundwater is limited. Since chromium must exist in the
hexavalent state for effective removal using ion exchange, further analysis on the
groundwater is necessary to determine the ionic form of the chromium at the site.
Bench-scale testing would also be required to demonstrate its effectiveness relative to
conventional chromium reduction followed by chemical precipitation. For the
purpose of alternative evaluation, this process option is dropped from further
consideration for reduction of concentrations of lead, chromium, and beryllium at the
site, due to its questionable effectiveness in removing the inorganics of concern. If
physical/chemical treatment is ultimately selected for implementation at this site, it
may be worthwhile to evaluate this option in more detail during the design phase.
Chromium Reduction
Chromium occurs in aqueous systems in both the trivalent (Cr+3) and the hexavalent
(Cr+0) ionic form, with er+• being much less likely to form an insoluble precipitate
than cr+3• Reduction of er+• to cr+3, and subsequent hydroxide precipitation of the
trivalent chromium ion, is the most common method of chromium removal. The
most common technique is to lower the waste stream pH to 2.0 -3.0 with sulfuric
acid, and convert er+• to cr+3 with a chemical reducing agent such as sulfur dioxide,
sodium bisulfide, metabisulfite or hydrosulfite, or ferrous sulfate. The cr+3 is then
removed, usually by hydroxide precipitation at an elevated pH. However, effective
reduction of er+• to cr+3 depends on the time allowed for reduction to occur, pH of
the reaction mixture, and concentration and type of reducing agent employed. Use of
sulfuric acid to reduce pH followed by sulfur dioxide to reduce Cr+• has been
reported to achieve er+• reductions from an initial concentration of 900 µg/1 to a final
concentration of 10-30 µg/1 (Patterson, 1985).
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Although it is unknown whether chromium exists in the cr+6 or cr+3 state in the
groundwate~it the New Hanover County Airport ·Bum Pit Site, this process option is
retained for application in conjunction with chemical precipitation. Bench-scale
treatability studies should be conducted prior to finalizing the process scheme.
2.2.4 DISCHARGE TECHNOLOGIES
Because the water treatment system design is dependent on the effluent criteria for the
discharge of treated groundwater from the site, several discharge alternatives were
considered. Each discharge option is discussed and evaluated below.
Discharge to Publiczy Owned Treatment Works CPQTWJ
Sanitary sewers that serve the New Hanover County Airport eventually discharge to
the James A. Loughlin Northside Wastewater Treatment Plant (Northside POTW)
operated by the City of Wilmington, North Carolina. Under a city code prohibiting
discharge of wastewaters containing explosive material (including petroleum-related
compound) (Wilmington City Code Section 12-137(3)), the groundwater may would
need to be treated for benzene prior to discharge to the North side POTW, depending
upon permit conditions. The Northside POTW discharge criteria are presented in
Table 2-5. This option has been retained for further consideration.
The exact address of the POTW under consideration is as follows:
James A. Loughlin Northside Wastewater Treatment Plant
2311 North 23rd Street
Wilmington, North Carolina 28405
Contact: Jerry Nichols, Plant Manager
Telephone: [phone]
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TABLE 2-5
EFFLUENT CRITERIA FOR DISCHARGE ALTERNATIVES
• NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
Organics
Benzene
1, 2-Dichloroethane
Chloroform
Inorganics
Beryllium
Chromium
Lead
NOTES:
NS -No Standard
NS
NS
NS
6.5
50
25
1
0.38
0.19
NS
50
155
1 NCDNR Administrative Code Section 15 NCAC2B.0211(b).
2 State Drinking Water Quality Standards, 15A NCAC lSC.1500.
3 Wilmington City Code Section 12-137(3).
:5 1•
NS
NS
NS
2,000
NS
4 Benzene is not permitted into the POTW; therefore, groundwater must be treated to ·
below the detection limit (BDL) of benzene (1 µg/1).
5 The cleanup goal for lead is based on new EPA regulations for treatment technique
action levels (TTALs), (EPA, 1991). The SDWA MCL for lead is currently
50 µg/1. However, effective December 1992, the TTAL for lead, 15 µg/1, will
become the SOWA MCL. [The TTAL is based upon the need for water at the tap
to be less than 50 µg/1, and takes into account any lead pipe and other fixtures that
may contribute to lead contamination prior to leaving the tap (EPA, 1991).]
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Surface Water Discharge
Nearby surface water bodies were evaluated as potential receiving waters for the
treated effluent from the groundwater treatment system. The surface water of
primary interest is Smith Creek, located offsite, south of the New Hanover County
Airport.
Disposal of treated effluent to Smith Creek would include approximately 4,000 feet of
buried piping and a low pressure distribution system to convey treated groundwater.
National Pollutant Discharge Elimination System (NPDES) permitting would be
required for offsite discharge. Standard construction practices would be used for
installing the buried pipeline. The treated effluent would be monitored to ensure
compliance with NPDES permitting requirements. Surface water discharge criteria,
which apply to inorganic contaminants, are listed in North Carolina Administration
Code 15A NACAC 2B.0211 and are also presented in Table 2-5. Since this option is
a viable alternative for treated water disposal, surface water discharge has been
retained for further consideration.
Onsite Discharge
The onsite discharge technology retained for the New Hanover County Airport Bum
Pit Site is spray irrigation. Spray irrigation incorporates the disposal of water through
plant uptake and evaporation (evapotranspiration) and percolation through the soil.
The hydraulic loading is limited by the infiltration capacity of the soil. Major factors
for site selection include: the type of soil, the depth to groundwater, groundwater
control and movement, and distance from the source. In addition, the efficiency of
soil infiltration would decrease under freezing conditions. As a result, an alternate
disposal or storage technology (i.e., storage tanks) would be required. The
groundwater discharge criteria that apply to both organics and inorganics present at
the New Hanover County Airport Bum Pit Site are also presented in Table 2-5.
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Since land is available at the site for spray irrigation, which can be implemented
through standard engineering methods, this discharge process option has been retained s;;•
for further consideration.
2.3 SUMMARY OF PROCESS OPTIONS EVALUATION
Based on the evaluation of the retained process options, groundwater would be
contained by a slurry wall or extracted using recovery wells. The extracted
groundwater would be pumped through a groundwater treatment system, which may
vary depending on the discharge alternative selected. The discharge options for
treated groundwater include: onsite spray irrigation, discharge to the City of
Wilmington Northside POTW, or discharge to Smith Creek. The evaluation of the
process options is summarized in Table 2-6.
2.4 DEVELOPMENT OF REMEDIAL ACTION ALTERNATIVES
In combining groundwater containment, collection, treatment, and disposal process
options to develop remedial action alternatives, all technologies feasible for the New
Hanover County Airport Burn Pit Site were considered. As previously discussed,
where more than one process option is appropriate within a given technology group,
one option or combination of options is used in the development of alternatives for
ease in evaluation. Further, more detailed, evaluation of specific processes should be
conducted after remedy selection (remedial design phase). The following are the
sitewide alternatives developed for the site.
Alternative 1 -No Action
Alternative 2 -Vertical Barrier
Alternative 3 -Groundwater Extraction and Physical Treatment (Air Stripping) with
Discharge to POTW
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TABLE2-6
EV ALUA TION OF PROCESS OPTIONS
Groundwater General
Response Actions
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
Remedial Technology Process Option
~~I N_o_ne ____ ~--~I _No_t_app!_icab_l_e ____ ~
Institutional
actions
Containment
Coledion
Treatment
Discharge
Access restrictions
Monitoring
1----~ Vertical barriers
Extraction
i----; Physical/chemical
treatment
Onsits discharge
Offsite <isdlarge
Deed restrictions
i----Groundwater monitoring
Slunywall
Precipitation
--~ Spray irrigation
POTW
Pipeline to surface water I ? )/t I Process option eliminated from further consideration ~-------~
Effectiveness -
Does not achieve remedial action objectives
Effectiveness depends on continued future
implementation. Does not reduce contamination.
Useful lor documenting conditions. Does not
reduces risk by itself.
Effective, but susceptible to weathering. capping
required to prevent mounding.
Effective if proprietary fixation chemicals are
used to ensure impermeable barrier. Capping
required to prevent mounding.
lmplemenlablllty
Not acceptable to local/public
government
Legal requirements and authority
Alone, not acceptable to publidlocal
government
Cost
None
Negligible cost ., .. •
Low capital, low O&M
Readily implernenlable, adequate safety High capital, low
measures required when digging trench maintenance.
Appropriate fixation chemicals Very high capital, low
would be required. TrealabDitiy maintenance.
tests may be required.
Effective, least susceptible to aacking. capping Readily implementable Very high capital, low
maintenance. required to prevent mounding.
Effective and reliable; conventional technology
Effective and reliable; conventional technology.
Requires sludge disposal.
Effective and reliable; Proper pretreatment
required.
Effective and reliable; Proper pretreatment
required. Requires disposal of used carbon.
Not effective for removal of beryllium.
Readily implementable
Readily implementable
Readily implementable
Readily implementable
Readily implementable
Effective and reliable; Proper monltorilg required. Permit required; must praolide storage
<ilrilg cold and wet weather.
Effective and reliable; Effluent needs to meet
required discharge lin its.
Effective and reliable; Efflueot needs to meet
required discharge fimits.
Effective and reliable; Effluent needs to meet
required discharge linits.
Further negotiations may be required
to ensure acceptance ol treated watsr
byPOTW
Permit required
Permit required
Low capital, moderats O&M
High capital,
high O&M
Low capital,
lowO&M
High capital, high O&M
High capital, moderats O&M
Moderate capital,
moderats O&M
Moderate capital,
moderats O&M
Low capital,
lowO&M
Moderate capital,
lowO&M
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Alternative 4 -Groundwater Extraction and Physical/Chemical Treatment (Chromium
. Reduction, Metals Precipitation, and Air Stripping) with Discharge
~• via Spray Irrigation
Alternative 5 -Groundwater Extraction and Physical/Chemical Treatment (Chromium
Reduction and Metals Precipitation) with Discharge to Surface Water
These alternatives are discussed further in Section 3.0.
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3.0 EVALUATION OF REMEDIAL ACTION ALTERNATIVES
In this section, a description and evaluation of each remedial action alternative is
provided. The evaluation of alternatives generally involves developing a conceptual
design for the corrective action and identifying key factors relating to the remediation.
This section describes five remedial action alternatives for the New Hanover County
Airport Bum Pit Site. In accordance with the NCP, these alternatives were evaluated
based on the following factors:
• Overall protectiveness
• Compliance with ARARs
• Long-term effectiveness and permanence
• Reduction of mobility/toxicity/volume (M/T/V)
• Short-term effectiveness
• Implementability
• Cost
First, by using the overall protectiveness criterion, each alternative was assessed to
determine its ability to adequately protect human health and the environment (both
short-and long-term) from unacceptable risks posed by the groundwater contaminants
present at the site. Second, the alternative was assessed to determine whether its
compliance with ARARs under federal, state, and local environmental laws applicable
to this specific site. Third, the alternative was also evaluated for the long-term
effectiveness and permanence it affords, along with the degree of certainty that the
alternative will prove successful. Fourth, the degree to which the alternative reduces
toxicity, mobility, and volume was assessed. Fifth, the short-term impact of the
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alternative was assessed. Sixth, the ease or difficulty of implementing the alternative
was assessed. Finally, the capital, annual operation and maintenance (O&M) costs, ~· and net present value of capital and O&M costs were evaluated.
3.1 GROUNDWATER EXTRACTION ANALYSIS
In order to identify operating criteria for the long-term corrective action alternatives
involving groundwater extraction, FPC developed a groundwater model for the New
Hanover County Airport Burn Pit Site to simulate an extraction scenario using
extraction wells. The results of the groundwater extraction analysis are presented as
the first component in the evaluation of corrective action alternatives.
FPC developed a two-dimensional groundwater flow model for conditions at the site
to help estimate the duration of pumping required to capture the dissolved
contaminant plume. The flow model was also developed to predict the impact of
pumping on local groundwater levels. FPC selected the model for this analysis based
on the Theis groundwater flow equation (Theis, 1935). This analytical equation
describes transient flow to a well pumping from a homogeneous, isotropic aquifer of
uniform thickness and infinite extent, where wells are screened throughout the depth
of the aquifer and have an infinitesimally small diameter. Simulated water level
drawdown contours were performed by superimposing the field-measured regional
hydraulic gradient to determine the resultant hydraulic gradient at the site. Based on
the resultant hydraulic gradient and Darcy's Law for calculating groundwater flow
velocities, approximate durations of extraction required to capture the contaminant
area were calculated. Generally, this method applies only to flow in confined
aquifers, but the error involved in applying it to unconfined situations, such as the
New Hanover County Airport Burn Pit Site, is small (EPA, 1989).
Several assumptions were made to simulate groundwater extraction at the site.
Sufficient monitoring should be performed during the design, installation, and
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operation of the final extraction system to confirm these assumptions and fully assess
the effectivt;p.ess of the extraction system.
3.1.1 AQUIFER CHARACTERISTICS
For the purposes of groundwater modeling, an average storativity of 6.3 x 10-3
(unitless) and effective porosity of five percent were assumed to sufficiently represent
the hydrogeologic conditions at the site. In addition, a static head of 28 feet of water
column is used as a representative value for the average static head conditions within
the area modeled. The average hydraulic gradient is assumed to be relatively flat
based on the inconsistent and relatively small variations in water level measurements
presented in EPA' s remedial investigation report, and the fact that water level
elevations tend to follow surface topography, which is relatively flat within the New
Hanover County Airport Burn Pit Site. A hydraulic conductivity of 6.6 ft/day and a
transmissivity of 146 ft2/day are assumed to be representative of the saturated
thickness of the unconfined aquifer (EPA, 1992b).
3.1.2 GROUNDWATER MODELING ASSUMPTIONS
In order to model the groundwater conditions at the site, the following assumptions
were made.
1.
2.
3.
Estimates of the duration of pumping required to capture the area of
contamination assumes only advective transport. Properties such as
sorption, retardation, dispersion, and biodegradation are not modeled.
Groundwater flow during continuous pumping conditions is assumed to
be steady-state.
The aquifer is assumed to be homogeneous and isotropic.
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4.
5.
3.1.3
The extraction wells are assumed to be screened throughout the depth
of the aquifer and have an infinitesimally small diameter.
The source of groundwater contamination is assumed to be removed or
non-existent. ·
THEIS ANALYSIS RESULTS
The principal means of optimizing contaminated groundwater recovery is through the
alteration of the water gradient to enhance and/or control contaminant movement.
This can be accomplished by placing an extraction system downgradient of the
contaminant area, inducing a water gradient, or artificially influencing an existing one
via groundwater extraction.
Three groundwater extraction wells, placed downgradient within the contaminant
plume (see Section 1.5.1) to contain the plume and prevent further migration of
contaminated groundwater offsite, were evaluated. The groundwater extraction wells,
depicted in Figure 3-1 as EX-I, EX-2, and EX-3, are approximately 120 feet apart,
overlapping the cones of influence to ensure complete capture of the contaminant
plume. A production rate of 5 gpm per well (15 gpm total) for the three extraction
wells was assumed based on the Theis analysis and results from the aquifer test
presented in EPA's remedial investigation. Although actual flow rates are not
expected to vary significantly from those assumed, exact capacities should be
determined in the field during installation of the extraction wells.
Referring to Figure 3-1, the scenario presented above was simulated for steady-state
conditions at the 15 gpm total pumping rate, and the resulting hydraulic gradient
shows capture of the contaminant plume. However, due to the tendency for
petroleum hydrocarbons to adsorb to soil particles, extraction of several pore volumes ·
of contaminated groundwater is often required for adequate capture of the dissolved
constituents. As a result, this can increase the duration of cleanup required by a
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LEGEND
----□ERM/ROAD ----
!TfT"1TTTTITrmnn-EXCAVAIION
11!!111 POSSIBLE SURFACE WAT(R
DRAINAGE AREAS ., SIMULAl(D
EXTRACTION WELL ,2,-ORAWDOWN CONTOUR
(Fee()
ARMY CORPS
OF [NGINEEHS
usr FARM
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I; 1;
/ 1 GROUNDWATER / I SIMULAIION
-~OUN DARY
It ----------------------11
fj
10 WILM/NG/ON
EXTRACTION WELL DRAWDOWN -15 GPM TOTAL PUMPAGE
NEW HANOVER COUNTY AIRPORl'·BURN PIT SITE
a a11boidiary of C&mp l>n:ua &. McKee Inc.
COM FEDERAL PRO<;RAMS CORPORATION WILMINGTON, NORTH CAROLINA
APPROXIMATE TOTAL
EXTENT Of CONTAMINATION
IN GROUNDWATER
100 0 ~--100
J APPROXIMATE
SCA!.[ IN FE [ f
200
FIGURE No. 3-1
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factor of three or more. The reduction of contaminant concentrations over time is the
primary indicator of the effectiveness of an extraction system. The ideal scenario ,.
would be a steady decrease in contaminant concentrations until a target level is
attained. However, performance records suggest that although concentrations may
drop initially, decline is followed by a leveling of concentrations with little or no
further decrease over time (EPA, 1989). The number of estimated pore volumes
required to capture the dissolved constituents can be approximated based on cleanup
goals for the site. Generally, it is assumed that three to five pore volumes (500,000
to 900,000 gallons) will flush the site of dissolved contamination.
Based on the aquifer and contaminant characteristics and Darcy's Law for calculating
flow rates, the estimated duration to capture three pore volumes of the contaminant
plume at a pumping rate of 15 gpm is estimated to be 48 weeks. However, this is
only an approximation, and could be predicted more accurately at the design stage
through field tests (i.e., grain size, total organic content, and pump tests).
3.2 ALTERNATIVE I -NO ACTION
3.2.1 DESCRIPTION
This alternative provides the baseline case for comparing remedial actions and the
level of improvement achieved. This alternative consists of leaving the site as it is
without conducting any further remedial actions. However, long-term groundwater
monitoring of six existing monitor wells would be conducted to track changes in
environmental quality over an estimated 30-year period.
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3.2.2 EVALUATION
Overall Protectiveness
The no-action alternative does not eliminate any exposure pathways or reduce the
level of risk. The risk assessment concludes that existing contamination would result
in an excess lifetime cancer risk exceeding 10-6 for groundwater at the site.
Compliance with ARARs
This alternative does not achieve the remedial action objectives or ARARs established
for the site.
Long-Term Effectiveness and Permanence
The continued contaminant migration via groundwater transport to potential offsite
receptors is a long-term impact of this alternative.
Reduction of M/T/V
No reductions in contaminant MIT /V are realized and groundwater cleanup goals
would be exceeded. The no-action alternative, therefore, is not considered to be
protective of human health and the environment.
Short-Term Effectiveness
Since no further remedial actions would be implemented at the site, this alternative
poses no short-term risks to onsite workers. It is assumed that Level D personal
protection would be used when sampling the existing wells for groundwater
monitoring purposes.
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Implementability
This alternative could be implemented immediately.
~
The estimated annual operation and maintenance (O&M) cost for this alternative is
approximately $7,920. The present net worth O&M costs for this alternative is
approximately $74,661, a discount rate of 10 percent over 30 years. Detailed cost
estimates are presented in Appendix C.
3.3 ALTERNATIVE 2 -VERTICAL BARRIER
3.3.1 DESCRIPTION
This alternative involves cont.µning the groundwater plume with a vertical barrier
(i.e, slurry wall) and constructing an impermeable cap to prevent groundwater
mounding. When using a slurry wall, a trench would be excavated around the
approximate extent of contamination shown in Figure 1-13. The trench would extend
over a length of approximately 1,600 feet and a depth of at least 30 feet bis and
should be anchored to the confining layer. After excavation, the trench can be
backfilled with a mixture of cement-bentonite to create an impermeable vertical
barrier that would prevent potential migration of the plume. Some dewatering may be
.required during implementation of this technology. For ease in implementation and to
minimize worker exposure risks, the excavation would be performed in phases. This
technology would have to be used in conjunction with capping of the site to prevent
any mounding that could occur due to the rainfall infiltration that would be captured
by the vertical barrier. A cross-section of the cap is shown on Figure 3-2.
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2% MINIMUM SLOPE
VVVVVVVVVVVVVVVVVV V vvvvvvvvvvvvvvvvvvv' V VVVVVVVVVVVVVVVVVVV / vvvvvvvvvvvvvvvvvvvv V /VVVVVV.' ,,, ,,, ,,, ,,, "' "~VVVVVVV / · r v v v v v v -c;OMl;'ACJED_SO~ c9vqi. v v v v v v v,
V VVVVVVVVVVVVVVVVVVVV / vvvvvvvvvvvvvvvvvvvv, V VVVVVVVVVVVVVVVVVVVV / vvvvvvvvvvvvvvvvvvvv,
40 Mil HOPE
SYNTHETIC LINER
GEOTEXTILE
(8 Ounces)
CROSS-SECTION OF TYPICAL IMPERMEABLE SURFACE CAP • .,,,=e~ __ _:_N::..=E_W_H_::_:A_::_:N--=----=OVER COUNTY AIRPORT BURN PIT SITE
CDMFEDERALPROGRAMSCORPORATION WILMINGTON, NORTH CAROLINA
1 n.t.idlary ofCaip Dr-,l Mc.Xoc !oc. FIGURE No. 3·2
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Capping would prevent infiltration and applicable drainage structures (i.e., ditches and
retention basins) may be required to redirect surface runoff. The cap would be ;•
installed over the approximate extent of contamination (shown in Figure 1-13), which
extends over an approximate area of 3.5 acres. An impermeable cap typically
consists of four layers. A minimum of 6 to 12 inches of cover material would be
placed over the existing soils to provide a foundation to support the cap. An
impermeable membrane (i.e., 40 mil HDPE liner) would be placed over the cover
material and would be underlain by a protective geotextile fabric to protect it from
puncture. A I-foot drainage layer above the liner would be constructed of sand. The
top foot of the cap would consist of topsoil to provide a root zone for vegetative
growth to prevent erosion. The cap would have a minimum slope of 2 percent.
Surface runoff would be directed through appropriate drainage channels. Precipitation
that percolates through the topsoil would flow laterally through the sand drainage
layer and into the drainage channels.
3.3.2 EVALUATION
Overall Protectiveness
The contaminated groundwater would be contained, therefore minimizing the risk of
contaminating downgradient drinking water wells. This alternative greatly reduces the
risk of groundwater ingestion and inhalation during showering for potential receptors.
Compliance with ARARs
Containment of the plume would be achieved. Groundwater contaminant
concentrations, however, would not meet the established cleanup goals for the New
Hanover County Airport Burn Pit Site.
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Long-Term Effectiveness and Permanence
The potential for long-term migration of the contaminant plume would be greatly
reduced. Although weathering of the slurry wall may occur, slurry walls are typically
expected to have a serviceable life of at least 30 years. Installation of an
impermeable cap would result in increased runoff, which could cause offsite erosion.
Although liners are typically warranted for 20 years, the serviceable life could well
extend beyond this timeframe. Restrictions on future land use would be required.
This remedy is not considered permanent.
Reduction of M/T/V
No reductions in contaminant toxicity or volume are realized and groundwater cleanup
goals would be exceeded. However, the mobility of the groundwater contamination
would be greatly reduced.
Short-Term Effectiveness
Adequate shoring mechanisms (i.e., sloping and use of retaining walls) should be
considered when excavating the trenches to minimize risks to workers. Construction
activities at the site could result in the release of toxic gas emissions from the
contaminated groundwater. Also, operation of heavy equipment during construction
would produce some noise nuisance. It is assumed that Level D personal protection
would be used during construction activities.
Equipment and personnel decontamination facilities would also be necessary. A
heavy equipment washdown pad would be constructed and trench excavation
equipment, if in contact with contaminated groundwater, would be .decontaminated
prior to leaving the site. Washwater would be stored in drums and removed for
offsite treatment.
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Implementability
Preliminary Schedule
Approximately six months would be required for design and contractor selection.
Construction of the vertical barrier would require approximately six months.
Construction of the surface cap would require approximately two months. Assuming
no major delays, this alternative could be implemented in approximately 1.5 years.
Engineering Considerations for Vertical Barrier
The major engineering considerations for the implementation of a slurry wall are:
•
•
•
•
Selection of slurry materials to be compatible with groundwater
contaminants
Design and installation of offsite downgradient monitor wells
Design and determination of barrier depth
Design and construction of subsurface drains for dewatering purposes
Engineering Considerations for Impermeable Cap
The major engineering considerations for the implementation of the cap are:
• Anticipated serviceable life of the liner
•
•
•
Liner permeability, tensile strength, resistance to shrinkage, punctures
and tears, handling, and seaming
Cap thickness and infiltration potential
Capping materials
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• Design and construction of a stormwater runoff collection system
• ,:. Environmental factors, including temperature, rainfall, wind, and
sunlight
• Design and construction of subsurface drains
Equipment and Materials
The major construction equipment and materials required for implementing this
alternative include:
• Contractor's temporary facilities and utilities
• Soil cover
• Synthetic liner materials
• • Bulldozer
• Backhoe
• Front-end loader
• Dump trucks
• Hydroseeding equipment
• Cement and bentonite for slurry wall
• Water source for barrier construction
Operation and Maintenance
Short-and long-term monitoring would be required for this alternative. Air
monitoring during trench excavation activities would be necessary to ensure that a
safe working environment is maintained and that no threat to the public health or the
environment is created by the volatilization of groundwater contaminants at the site.
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For costing purposes, it was assumed that four new downgradient monitor wells
would be sampled annually for 30 years. Samples would be analyzed for benzene, ·-· chloroform,
0
1,2-dichloroethane, beryllium, chromium, and lead.
The present net worth O&M cost for this alternative is approximately $1,076,103,
including capital costs of $914,337 and present worth O&M costs of $161,766, using
a discount rate of 10 percent over 30 years. The estimated annual O&M cost for this
alternative is approximately $17,160. Detailed cost estimates are presented in
Appendix C.
3.4 ALTERNATIVE 3 -GROUNDWATER EXTRACTION
AND PHYSICAL TREATMENT (AIR STRIPPING)
WITH DISCHARGE TO POTW
This alternative includes groundwater extraction, VOC removal using air stripping,
and discharge to the Northside POTW, owned by the City of Wilmington. A detailed
description of the remediation to be conducted under this alternative is provided
below.
3.4.1 DESCRIPTION
Groundwater would be extracted as described in Section 3. I. The estimated locations
of groundwater extraction collectors are represented in Figure 3-1. Groundwater
would be extracted from extraction wells located within the dissolved plume.
Groundwater would be pumped directly to the onsite treatment system. Groundwater
recovery would be accomplished at an approximate steady-state rate of 15 gpm.
Groundwater remediation is estimated to take approximately 48 weeks.
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-
As previously discussed, groundwater contaminants to be removed from the site are
benzene, chloroform, 1,2-dichloroethane, chloroform, beryllium, chromium, and lead.
"·•
After extracting the contaminated groundwater exceeding cleanup goals, benzene
would be treated onsite by air stripping to meet the "below detection limit"
(i.e., 1.0 µg/1)) requirement for ultimate discharge to the POTW. Existing
chloroform and 1,2-dichloroethane concentrations would also be significantly reduced
through air stripping. Treated groundwater would flow from the air stripper to a
sewer connection to the POTW. Sewer lines exist along the perimeter roads of the
New Hanover County Airport. Pretreatment equipment may be required to remove
TSS and iron prior to air stripping. For costing purposes, the use of a pretreatment
system is assumed to avoid the potential fouling of the air stripper.
The groundwater treatment system would be designed to operate 24 hours per day.
System controls would allow for complete automatic operation with minimal operator
attention. Alarms and switches would be furnished as required for fail-safe operation.
Instruments to monitor key operating parameters, such as water flow rate, system line
pressure, and multi-media filter differential pressure, would be included.
For costing purposes, it is assumed that all treatment equipment would be leased. To
the extent possible, major equipment would be furnished skid-mounted and complete
with all piping and controls mounted on structural steel support skids. It is assumed
that no air quality control equipment would be needed to capture VOCs released from
the air stripper, due to their low concentrations in the groundwater.
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3.4.2 EVALUATION
Overall Protectiveness
The greatest reduction in the potential risk of groundwater ingestion and inhalation
would be achieved since all contaminated groundwater would be extracted, and treated
to levels acceptable for POTW discharge.
Compliance with ARARs
Groundwater contaminant concentrations would meet the established cleanup goals for
the New Hanover County Airport Bum Pit Site. The treated effluent would meet the
POTW requirements.
Long-Term Effectiveness and Permanence
The potential of offsite contaminant migration via groundwater would be eliminated
permanently. The groundwater treatment system would require performance
specifications to ensure the adequate operation of the system. Long-term public
health risks associated with groundwater ingestion and inhalation would be eliminated.
No future site use restrictions would be required once groundwater extraction
treatment is completed.
Reduction of M/T/Y
Extraction and treatment of contaminated groundwater would achieve a maximum and
permanent reduction of contaminant mobility, toxicity, and volume in the
groundwater.
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Short-Term Effectiveness
Small-scale construction activities during installation of the extraction wells and
during air stripper operation may result in the release of minimal volatilized
contaminants, and the operation of drilling equipment would produce additional noise.
Therefore, health and safety requirements while implementing this alternative would
include periodic monitoring of organic vapors and the use of personal protection
equipment by all personnel at the site. It is assumed that Level D personal protection
would be used. Equipment and personnel decontamination facilities would also be
necessary.
Implementability
Preliminary Schedule
Approximately six months would be required for design and contractor selection.
Groundwater extraction and remediation would require approximately one year.
Assuming no major delays, this alternative could be implemented in approximately ·
two years.
Engineering Considerations for Groundwater Extraction and Discharge
The major engineering considerations to implement the groundwater extraction and
discharge systems include:
• Design, installation, and testing of extraction well system
• Potential for well plugging (reduction in flows) over time
• Monitoring requirements
• Difficulty in capturing residual contaminant concentrations
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g
•
•
•
•
Cleanup verification
;.well abandonment
Piping of treated effluent to sewer line connected to POTW
Permit requirements for the Northside POTW and ability to obtain a
discharge permit
Engineering Considerations for Groundwater Treatment
The major engineering considerations to implement the groundwater treatment system
include:
• The need to implement pretreatment equipment
• Siting and design of pretreatment units (if required) and air stripper
•
•
•
Monitoring the effluent water quality for POTW discharge
The need to implement treatment equipment for off-gases from the air
stripper and monitoring the effluent air quality from the air stripper
Process effectiveness monitoring
• Potential for fouling of media
Equipment and Materials
The major system components required for operations under this alternative include:
•
•
•
Submersible groundwater pumps
Air stripping tower (with packing) for the groundwater treatment
system and only pretreatment equipment required
Piping, fittings, and valves for fluids transport
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• Electrical conduit and wiring for electric power and sensors
• ; • System instrumentation and controls
The major construction equipment and materials required to implement this alternative
include:
• Contractor's temporary facilities and utilities
· • Well drilling equipment
• Front-end loader
• Backhoe
Operation and Maintenance
Long-term groundwater monitoring for cleanup verification purposes would be
required for this alternative. It is assumed that six existing wells would be sampled
and water levels recorded on a quarterly basis for the first year (assuming one year
for plume capture) and on an annual basis for the following 29 years. Samples would
be collected and analyzed for benzene, chloroform, 1,2-dichloroethane, beryllium,
chromium, and lead.
The groundwater treatment system would also require monitoring and maintenance
during its approximate 48-week operational life. Monitoring of the treatment system
would include periodic sampling of the influent and effluent from the treatment
system and analyzed in accordance with the POTW discharge permit requirements.
Sample collection is assumed to be on a weekly basis. Samples are anticipated to be
analyzed for benzene, pH, and any other parameters required by the Northside POTW
discharge permit.
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Maintenance of the extraction and treatment systems would be performed in
accordance with O&M requirements developed after equipment specification and
procurement~~e completed. At a minimum, it is expected that regular periodic
maintenance would be required on the submersible pumps, valves, and fittings of
fluids piping systems, as well as on the treatment system components (i.e., tower
packing media cleaning and/or replacement) to ensure the efficient operation of the
system.
The present net worth O&M cost for this alternative is approximately $1,152,033,
including capital costs of $794,067 and present worth O&M costs of $357,966, using
a discount rate of 10 percent over 30 years. The estimated annual O&M cost for this
alternative is approximately $312,855 for the first year and $7,200 for the remaining
29 years. Detailed cost estimates are presented in Appendix C.
3.4 ALTERNATIVE 4 -GROUNDWATER EXTRACTION AND
PHYSICAL/CHEMICAL TREATMENT (CHROMIUM
REDUCTION. METALS PRECIPITATION, AND AIR STRIPPING)
WITH DISCHARGE VIA SPRAY IRRIGATION
This alternative includes groundwater extraction, chromium reduction, metals
precipitation, air stripping, and onsite discharge by spray irrigation. A detailed
description of the remediation to be conducted under this alternative is provided
below.
3.4.1 DESCRIPTION
Groundwater would be extracted as described in Section 3.1. The locations of
groundwater extraction collectors are represented in Figure 3-1. Groundwater would
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be extracted from extraction wells located within the dissolved plume. Groundwater
would be pumped directly to the onsite treatment system. Groundwater recovery ~· would be accomplished at an approximate steady-state rate of 15 gpm. Groundwater
remediation is estimated to require approximately 48 weeks.
As previously discussed, groundwater contaminants to be removed from the site are
benzene, chloroform, 1,2-dichloroethane, beryllium, chromium, and lead. After
extracting the contaminated groundwater exceeding cleanup goals, the groundwater
would be treated onsite by chromium reduction, metals precipitation, and air stripping
to meet state requirements for ultimate groundwater discharge via spray irrigation.
To meet these requirements, concentrations of all six site contaminants must be
reduced. Treated groundwater would be pumped from the metals precipitation system
into the air stripper and finally to a pipeline with sprinklers to be spray irrigated
onsite.
For evaluation purposes, it is assumed that this alternative would consist of chromium
reduction, metals precipitation using sodium hydroxide, flocculation, clarification, and
filtration. Flocculation and clarification are necessary to enhance solids removal,
reducing the load on filtration, and minimizing filter backwashing frequency. The
treatment scheme involves pumping the contaminated groundwater into a series of
mixing tanks where it is rapidly combined with chemicals for pH adjustment,
chromium reduction, precipitation, and flocculation. Following the mixing stage, the
water flows into a clarifier, where the solids-liquid separation occurs. Due to the low
effluent limits for metals, it is expected that sand or multi-media filtration will be
required to remove residual solids after settling.
The settled sludge is then pumped to a storage tank for subsequent dewatering using a
filter press. The water recovered from the dewatering operation would be recycled to
the treatment's influent stream, and the concentrated sludge/filter cake analyzed and
disposed offsite at a hazardous or solid waste landfill, as applicable. The treated
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effluent from the filter would be discharged to the air stripper to remove VOCs of
concern. All metal and organic concentrations would be reduced to below state -,;•
groundwater discharge permit requirements. The treated groundwater would then be
pumped to an onsite spray irrigation system. Operation of the extraction system
during wet weather or freezing temperature conditions requires provisions for
sufficient storage of treated groundwater, anticipating an appropriate design rainfall.
A variation to this treatment scheme should be considered during the design phase.
Although hexavalent chromium can be reduced in a pretreatment step prior to
precipitation, it can also be removed as cr+6 by an ion exchange column after the
filtration step has effectively removed other metal hydroxide solids.
The groundwater treatment system would be designed to operate 24 hours per day.
System controls would allow for complete automatic operation with minimal operator
attention. Alarms and switches would be furnished as required for fail-safe operation.
Instruments to monitor key operating parameters, such as water flow rate, system line
pressure, and multi-media filter differential pressure, would be included.
For costing purposes, it is assumed that all treatment equipment would be leased. To
the extent possible, major equipment would be furnished skid-mounted and complete
with all piping and controls mounted on structural steel support skids. It is assumed
that no air quality control equipment would be needed to capture VOCs released from
the air stripper, due to their low concentrations in the groundwater.
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3.4.2 EVALUATION
~·
Overall Protectiveness
The greatest reduction in the potential risk of groundwater ingestion and inhalation
would be achieved since all contaminated groundwater would be extracted and treated
to levels acceptable for onsite groundwater discharge.
Compliance with ARARs
Groundwater contaminant. concentrations would meet the established cleanup goals for
the New Hanover County Airport Bum Pit Site. The treated effluent would meet
state groundwater discharge permit requirements.
Long-Term Effectiveness and Permanence
The potential for offsite contaminant migration via groundwater would be eliminated
permanently. The groundwater treatment system would require performance
specifications to ensure the adequate operation of the system. Long-term public
health risks associated with groundwater ingestion and inhalation would be eliminated.
No future site use restrictions would be required once groundwater extraction and
treatment are complete.
Reduction of M/T/V
Extraction and treatment of contaminated groundwater would achieve a maximum and
permanent reduction of contaminant mobility, toxicity, and volume in the
groundwater.
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Short-Tenn Effectiveness
Small-scale construction activities during installation of the extraction wells and
during air stripper and mixing equipment operation may result in the release of
minimal volatilized contaminants, and the operation of drilling equipment would
produce additional noise. Therefore, health and safety requirements while
implementing this alternative would include periodic monitoring of organic vapors and
the use of personal protection equipment by all personnel at the site. It is assumed
that Level D personal protection would be used. Equipment and personnel
decontamination facilities would also be necessary.
Implementability
Preliminary Schedule
Approximately six months would be required for design and contractor selection.
Groundwater extraction and remediation would require approximately one year.
Assuming no major delays, this alternative could be implemented in approximately
two years.
Engineering Considerations for Groundwater Extraction and Discharge
The major engineering considerations to implement the groundwater extraction and
discharge systems include:
• Design, installation, and testing of extraction well system
• Potential for well plugging (reduction in flow) over time
• Monitoring requirements
• Cleanup verification
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• Well abandonment
• ;;• Spray irrigation system
• Permit requirements for the onsite groundwater discharge
Engineering Considerations for Groundwater Treatment
The major engineering considerations to implement the groundwater treatment system
include:
•
•
•
·•
•
•
•
•
•
•
Siting and design of metals removal system and air stripper
Volume of sludge generated from metals precipitation
Monitoring the effluent water quality for groundwater discharge
Monitoring the sludge/filter cake generation from the metals removal
system
Determining the need for treatment of off-gases and monitoring the
effluent air quality from the air stripper
Ease in treatment system operation
Determining if system-generated waste materials are hazardous wastes
under RCRA
Process effectiveness monitoring
Potential for fouling of stripper media
Provision for chemical storage
Equipment and Materials
The major system components required for operations under this alternative include:
• Submersible groundwater pumps
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• Tankage, mixers, controls associated with metals removal system
• ;. sodium hydroxide, sulfuric acid, required flocculants and coagulants,
and other treatment chemicals
• Air stripping tower
• Pumps, piping, fittings, and valves for fluids transport
• Electrical conduit and wiring for electric power and sensors
• Instrumentation and controls
• Spray irrigation system
The major construction equipment and materials required to implement this alternative
include:
• Contractor's temporary facilities and utilities
• Front-end loader
• Backhoe
Operation and Maintenance
Long-term groundwater monitoring for cleanup verification purposes would be
required for this alternative. It is assumed that six existing wells would be sampled
and water levels recorded on a quarterly basis for the first year (assuming one year
for capture plume) and on an annual basis for the following 29 years. Samples would
be collected and analyzed for benzene, chloroform, 1,2-dichloroethane, beryllium,
chromium, and lead.
The groundwater treatment system would also require monitoring and maintenance
during its approximate 48-week operational life. Monitoring of the treatment system
would include normal troubleshooting and periodic water sampling of the influent,
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midpoint, and effluent from the treatment system and analysis in accordance with the
groundwater. discharge permit requirements. Collection of samples is assumed to be
'" on a weekly· basis. Samples are anticipated to be analyzed for benzene, chloroform,
1,2-dichloroethane, beryllium, chromium, lead, pH, and any other parameters
required by state groundwater discharge permit. In addition, any sludge generated
would have to be packaged and disposed offsite at a hazardous or solid waste landfill,
as applicable. Finally, downgradient groundwater monitoring would be required to
ensure that the permit conditions are met, including groundwater table level
requirements.
Maintenance of the extraction and treatment systems would be performed in
accordance with O&M requirements developed after equipment specification and
procurement are completed. At a minimum, it is expected that regular periodic
maintenance would be required on the pumps, valves, and fittings of fluids piping
systems, as wells as on the treatment system components (i.e., cleaning of pH probes,
filter backwashing, replacement of consumable items, and sludge generation) to
ensure the efficient operation of the system.
The present net worth O&M cost for this alternative is approximately $1,525,141,
including capital costs of $1,042,388 and present worth O&M costs of $482,753,
using a discount rate of 10 percent over 30 years. The estimated annual O&M cost
for this alternative is approximately $450,120 for the first year and $7,200 for the
remaining 29 years. Detailed cost estimates are presented in Appendix C.
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3.5 ALTERNATIVE 5 -GROUNDWATER EXTRACTION AND
.· PHYSICAL/CHEMICAL TREATMENT <CHROMIUM REDUCTION ~-
AND METALS PRECIPITATION} WITH DISCHARGE
TO SURFACE WATER
This alternative includes groundwater extraction, metals precipitation, and discharge
to Smith Creek located approximately 4,000 feet south of the site. A detailed
description of the remediation to be conducted under this alternative is provided
below.
3.5.1 DESCRIPTION
Groundwater would be extracted as described in Section 3.1. The locations of
groundwater extraction collectors are represented in Figure 3-1. Groundwater would
be extracted from extraction wells located with the dissolved plume. Groundwater
would be pumped directly to the onsite treatment system. Groundwater recovery
would be accomplished at an approximate steady-state rate of 15 gpm. Groundwater
remediation is estimated to require approximately 48 weeks.
As previously discussed, groundwater contaminants to be removed from the site are
benzene, chloroform, 1,2-dichloroethane, beryllium, chromium, and lead. After
extraction of the contaminated groundwater exceeding cleanup goals, the groundwater
would be treated onsite by chromium reduction and metals precipitation to meet the
State of North Carolina requirements for ultimate surface water discharge. Treated
groundwater would flow from the treatment system to a pipeline that follows Gardner
Street into 23rd Street and eventually discharging into Smith Creek.
The primary objective of treatment would be reduction of chromium concentrations.
The treatment portion of this alternative would consist of chromium reduction metals
precipitation using sodium hydroxide, flocculation, clarification, and filtration:
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Flocculation and clarification are necessary to enhance metal removal, reducing the
load on fil~pon, and minimizing backwashing. The treatment scheme involves
pumping the contaminated groundwater into a series of mixing tanks where it is
rapidly combined with chemicals for pH adjustment, chromium reduction,
precipitation, and flocculation. Following the mixing stage, the water flows into a
clarifier, where the solids-liquid separation occurs.
The settled sludge is then pumped to a storage tank for subsequent dewatering using a
filter press. The water recovered from the dewatering operation is returned to the
treatment's influent stream, and the concentrated sludge/filter cake is analyzed and
disposed offsite at a hazardous or solid waste landfill, as applicable. All metal
concentrations would be removed to below the state surface water discharge permit
requirements. The treated groundwater would flow from the treatment system to a
pipeline that runs offsite to Smith Creek.
A variation to this treatment scheme should be considered. Although hexavalent
chromium can be reduced in a pretreatment step prior to precipitation, it can also be
removed as cr+6 by an ion exchange column after filtration step has removed any
solids. There are also other newly-developed process technologies for removal of
multivalent cations, such as ion-specific resin and magnesium oxide media. The
ultimate selection of the most appropriate process would be best accomplished during
the design stage.
The groundwater treatment system wou_ld be designed to operate 24 hours per day.
System controls would allow for complete automatic operation with minimal operator
attention. Alarms and switches would be furnished as required for fail-safe operation.
Instruments to monitor key operating parameters, such as water flow rate, system line .
pressure, and multi-media filter differential pressure, would be included.
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For costing purposes, it is assumed that all treatment equipment would be leased. To
the extent possible, major equipment would be furnished skid-mounted and complete
:;•
with all piping and controls mounted on structural steel support skids.
3.4.2 EVALUATION
Overall Protectiveness
The greatest reduction in the potential risk of groundwater ingestion and inhalation
' would be achieved since all contaminated groundwater would be extracted and treated
to levels acceptable for offsite surface water discharge.
Compliance with ARARs
Groundwater contaminant concentrations would meet the established cleanup goals for
the New Hanover County Airport Bum Pit Site. The treated effluent would meet the
state surface water discharge permit requirements.
Long-Term Effectiveness and Permanence
The potential for offsite contaminant migration via groundwater would be eliminated
permanently. The groundwater treatment system would require performance
specifications to ensure the adequate operation of the system. Long-term public
health risks associated with groundwater ingestion and inhalation would be eliminated.
No future site use restrictions would be required once groundwater extraction
treatment is complete.
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Reduction of M/T/V
:;•
Extraction and treatment of contaminated groundwater would achieve a maximum and
permanent reduction of contaminant mobility, toxicity, and volume in the
groundwater.
Short-Term Effectiveness
Small-scale construction activities during installation of the extraction wells as well as
operation of the mixing equipment may result in the release of minimal volatilized
contaminants, and the operation of drilling equipment would produce additional noise.
Therefore, health and safety requirements while implementing this alternative would
include periodic monitoring of organic vapors and the use of personal protection
equipment by all personnel at the site. It is assumed that Level D personal protection
would be used. Equipment and personnel decontamination facilities would also be
necessary.
Implementability
Preliminary Schedule
Approximately six months would be required for design and contractor selection.
Groundwater extraction and remediation would require approximately one year.
Application and successful acquisition of an NPDES permit would require
approximately six months. Assuming no major delays, this alternative could be
implemented in approximately 2.5 years.
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Engineering Considerations for Groundwater Extraction and Discharge
The major engineering considerations to implement the groundwater extraction and
discharge systems include:
• Design, installation, and testing of extraction well system
• Potential for well plugging (reduction in flow) over time
• Monitoring requirements
• Difficulty in capturing residual contaminant concentrations
• Cleanup verification
•
•
Well abandonment
Pipeline to Smith Creek
• NPDES permit requirements for the surface water discharge
Engineering Considerations for Groundwater Treatment
The major engineering considerations to implement the groundwater treatment system
include:
• Siting and design of treatment system
• Volume of sludge generated from metals precipitation
• Monitoring the effluent water quality for surface water discharge
•
•
•
Monitoring the sludge/filter cake generation from the metals removal
system
Determining if system-generated waste materials are hazardous wastes
under RCRA
Process effectiveness monitoring
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• Ease in system operation
• ~ "Provision for chemical storage
Equipment and Materials
The major system components required for operations under this alternative include:
• Submersible groundwater pumps
• Tankage, mixers, controls associated with metals removal system
• Sodium hydroxide, acid required flocculants and coagulants, and other
treatment chemicals
• Pumps, piping, fittings, and valves for fluids transport
• Electrical conduit and wiring for electric power and sensors
• Instrumentation and controls
The major construction equipment and materials required to implement this alternative
include:
• Contractor's temporary facilities and utilities
• Pipeline to Smith Creek
• Front-end loader
• Backhoe
Operation and Maintenance
Long-term groundwater monitoring for cleanup verification purposes would be
required for this alternative. It is assumed that six existing wells would be sampled
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and water levels recorded on a quarterly basis for the first year (assuming one year
for plume capture) and on an annual basis for the following 29 years. Samples would
be collected ~d analyzed for benzene, chloroform, 1,2-dichloroethane, beryllium,
~
chromium, and lead.
The groundwater treatment system would also require monitoring and maintenance
during its approximate 48-week operational life. Monitoring of the treatment system
would include normal troubleshooting and periodic water sampling of the influent,
midpoint, and effluent from the treatment system and analysis in accordance with the
NPDES discharge permit requirements. Collection of samples is assumed to be on a
weekly basis. Samples are anticipated to be analyzed for beryllium, chromium, lead,
pH, and any other parameters required by state surface water discharge permit. In
addition, any sludge generated would have to be packaged and disposed at an
hazardous or solid waste landfill, as applicable.
Maintenance of the extraction and treatment systems would be performed in
accordance with O&M requirements developed after equipment specification and
procurement are completed. At a minimum, it is expected that regular periodic
maintenance would be required on the pumps, valves, and fittings of fluids piping
systems, as well as on the treatment system components (cleaning of pH probes, filter
backwashing, replacement of consumable items, and sludge generation) to ensure the
efficient operation of the system.
The present net worth O&M cost for this alternative is approximately $1,587,181,
including capital costs of $1,120,928 and present worth O&M costs of $466,253,
using a discount rate of 10 percent over 30 years. The estimated annual operation
and maintenance (O&M) cost for this alternative is approximately $431,970 for the
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first year and $7,200 for the remaining 29 years. Detailed cost estimates are
presented in-Appendix C. :;•
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4.0 ANALYSIS AND SUMMARY OF ALTERNATIVES
This section compares and summarizes the effectiveness of each remedial action
alternative. In general, cost-effectiveness is an important criterion in comparing
treatment alternatives that provide similar levels of protection. However, cost alone
cannot be used to evaluate treatment alternatives in comparison to no action, or to
screen treatment versus non-treatment alternatives. Because the lowest cost
alternative may not satisfy remediation objectives or be protective of human health
and the environment, several factors other than cost are considered in the evaluation.
These non-economic factors include threshold criteria (overall protectiveness and
compliance with ARARs) and primary balancing criteria (long-term effectiveness,
reduction of MIT /V through treatment, short-term effectiveness, and
implementability).
In order for a specific alternative to be selected for remediation of the New Hanover
County Airport Bum Pit Site, three main criteria must be met: the threshold criteria,
the primary balancing criteria, and the modifying criteria. This section summarizes
the evaluation of each alterative based on the threshold and primary balancing criteria.
The modifying criterion, which includes state and community acceptance, would be
evaluated by EPA and the state prior to final selection of a remedy.
Restrictions that should be considered to reduce future potential for ingestion of
contaminated groundwater are outlined in Table 4-1. Restrictions might also be
placed upon future use of the site that could compromise the integrity of the remedial
actions. For offsite areas, restrictions would be implemented to limit the use of
property where contaminated groundwater may exist in the future.
4-1
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TABLE 4-1
SUMMARY OF INSTITUTIONAL AND LAND USE RESTRICTIONS
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
Yes Yes Yes
I: No Action
2: Vertical Barrier Ycs Yes Yes
3: Groundwater Extraction and Physical Treatment (Air Yes No No
Stripping) with Discharge to POTW
4: Groundwater Extraction and Physical/Chemical Treatment Yes No No
(Metals Pr«ipitation and Air Stripping) with Discharge Via
Spray Irrigation
S: Groundwater Extraction and Phy1ical/Chemical Treatment Ye, No No
(Metals Precipitation) with Discharge to Surface Water
!:!2!!!.'
m Fencing restrictiooa apply to the period of remediation only (except for no action).
Y ca Rcstrictio111 apply.
No No restrictions after remediation assuming that ARARs and cleanup goals arc met.
---!!!!!!I ==
Yes Ye,
Ye, Ye,
No No
No No
No No
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4.1 THRESHOLD CRITERIA
Overall protection of human health and the environment and compliance with ARARs
are threshold requirements that each alternative must meet in order to be eligible for
selection.
4.1.1 OVERALL PROTECTIVENESS
Each alternative was evaluated to determine whether it is likely to effectively mitigate
and minimize the long-term risk of harm to public health and the environment
currently presented by the site. A summary of this evaluation is presented in
Table 4-2.
4.1.2 . COMPLIANCE WITH ARARs
A goal of Superfund remedial activities under SARA is to attain ARARs of federal,
state, or local environmental statutes, whichever are more stringent. Federal
standards may include RCRA, the Clean Air Act, Safe Drinking Water Act, Ground
Water Protection Strategy, Clean Water Act, Toxic Substances Control Act, or Water
Quality Criteria. State standards include any promulgated by the North Carolina
Department of Environment, Health, and Natural Resources (NCDNR) and local
statutes include those promulgated by the City of Wilmington. Each remedial
alternative was evaluated with regard to its ability to comply with the ARARs, which
are generally based on acceptable levels of contamination to preserve the
environment, public health and welfare. ARARs for the site were presented in
Section 1.0.
Because the New Hanover County Airport Burn Pit Site is on the NPL, Superfund
policy and procedures are applicable. CERCLA compliance policy distinguishes
between onsite and offsite remedial actions. Environmental permits are not required
for fund-financed or enforcement actions taken at an NPL site if these actions are
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TABLE 4-2
SUMMARY OF THE PUBLIC HEALTH AND ENVIRONMENTAL EFFECTS EVALUATION
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
1: No Action
2: Vertical Barrier
3: Groundwater Extraction and
Physical Treatment (Air Stripping)
with Discharge to POTW
4: Groundwater Extraction and
Physical/Chemical Treatment
(Metals Precipitation and Air
Stripping) with Discharge via Spray
Irrigation
5: Groundwater Extraction and
Physical/Chemical Treatment
(Metals Precipitation) with
Discharge to Surface Water
Does not eliminate any exposure
pathways or reduce the level of risk.
Offsite contaminant migration would be
eliminated. Greatly reduces potential
risk of ingestion and inhalation.
Offsite contaminant migration would be
eliminated. Minimal operation and
maintenance of treatment system.
Eliminates potential risk of ingestion
and inhalation.
Same as Alternative 3.
Same as Alternative 3.
4-4
Not in compliance
Not in compliance
In compliance
In compliance
In compliance
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completely confined to the site (i.e., no discharge or implementation activities
performed offsite). It is anticipated that EPA will take lead responsibility in the
design and implementation of site remediation.
Compliance with ARARs for the five site remediation alternatives was evaluated in
Table 4-I. Table 4-3 identifies the federal regulations applicable to the five
alternatives under evaluation, with the exception of regulations under the Superfund
program. Table 4-4 identifies North Carolina regulations pertaining to the
alternatives. The City of Wilmington regulations are shown in Table 4-5.
4.2 PRIMARY BALANCING CRITERIA
The five primary balancing criteria are long-term effectiveness and permanence;
reduction of M/T/V through treatment: short-term effectiveness; implementability;
and cost. These are discussed below.
4.2.l LONG-TERM EFFECTIVENESS AND PERMANENCE
These two aspects of remedial actions determine their desirability on the basis of
effectiveness and effective life. Effectiveness refers to the degree to which an action
will meet the site cleanup goals, which were derived to minimize risk to public health
and the environment. The effective life is the length of time this level of
effectiveness can be maintained. The long-term effectiveness and permanence factors
associated with each alterative is summarized in Table 4-6.
· 4.2.2 REDUCTION OF M/T/V THROUGH TREATMENT
The degree to which the remedial action alternative reduces the mobility, toxicity,
and/or volume of contamination is a second factor used to determine its .desirability.
An evaluation of each alternative on the basis of M/T/V reduction is presented in
Table 4-7.
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TABLE 4-3
FEDERAL REGULATIONS AFFECTING IMPLEMENTATION OF THE
ALTERNATIVES UNDER EVALUATION
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
National Interim Primary 40 CPR 141
Drinking Water
Standards
National Secondary 40 CPR 143
Drinking Water
Standards
Clean Air Act 40 CPR 61
Maximum contaminant levels (MCLs) for
heavy metals, anions, bacteria, pesticides,
radionuclides, and organic chemicals of
concern in drinking water. These MCLs have
been adopted as groundwater standards for the
surficial aquifer at the site because the
groundwater at the New Hanover County
Airport Bum Pit Site is classified as Class I.
EPA' s cleanup policy is most stringent for
Class I groundwater, and involves cleanup to
background or drinking water levels. Several
of these MCLs have been adopted as cleanup
goals for the site.
Maximum contaminant levels (MCLs) for
constituents affecting the aesthetic quality and
use of drinking water.
National emission standards for hazardous air
pollutants. Applicable to air stripping of
contaminants.
4-6
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TABLE 4-4
NORTH CAROLINA REGULATIONS AFFECTING THE IMPLEMENTATION OF THE
ALTERNATIVES UNDER EV ALU A TI ON
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
North Carolina Drinking
Water Quality Standards
Classification of
Surface Waters
Surface Water
Quality Standards
Coastal Waste
Treatment Disposal
Wastewater Discharge to
Surface Waters
Wastewater Discharge
to Waters other than
Surface Waters
of the State
15 NCAC !SC.1510 Drinking water quality standards applicable to
through lSC.1518 groundwater at the New Hanover County Airport
Bum Pit Site. Applicable to Alternatives
2, 3, 4, and 5.
15A NCAC 2B.0100 Procedures for assignment of water quality
standards for surface waters. Smith Creek is a
Class C surface water. Applicable to
Alternative 5.
15A NCAC 2B.0200 Classifications and water quality standards
applicable to surface waters of North Carolina.
Applicable to Alternative 5.
15A NCAC 24.0400 Treatment standards to ensure compliance with
water quality standards promulgated by the
North Carolina Environmental Management
Commission for propagation of shellfish in
coastal waters (i.e., class C waters). Applicable
for discharge to Smith Creek. Applicable to
Alternative 3.
15A NCAC 2H.0100 Requirements and procedures for application and
issuance of State NPDES permits. Applicable to
Alternative 5.
15A NCAC 2H.0200 Requirements and procedures for application and
issuance of permits for discharge to sewer
systems, disposal systems, treatment works, and
sludge disposal systems. Applicable to
Alternative 3.
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TABLE 4-5
LOCAL REGULATIONS AFFECTING THE IMPLEMENTATION OF THE
ALTERNATIVES UNDER EVALUATION
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
Discharge to POTW City of Wilmington Article III,
Sections 12-76 to 12-162
4-8
The City of Wilmington has
established minimum quality
standards for disposal to the
Northside POTW. Applicable
to Alternative 3.
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-- ------- - - --- --
TABLE 4-6
WNG-TERM EFFECTIVENESS AND PERMANENCE EVALUATION FOR REMEDIAL ACTION ALTERNATIVES
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
No Action
Vertical Barrier
Groundwater Extraction and Physical
Trcatmcnl (Air Stripping) with Di1ehargc
10 POTW
Groundwater Extraction and
Physical/Chemical Treatment {Chromium
Reduction, Metals Precipitation, and Air
Stripping) and Discharge Via Spray
Irrigation
Groundwater Extraction and
Physical/Chemical Treatment (Chromium
Reduction and Metals Precipitation) and
Discharge to Surface Water
WILMINGTON, NORTH CAROLINA
Doe■ not limit migration of or remove
contaminanta. ARARB are exceeded.
Doc1 not remove contaminants, but will limif
off'sitc migration of contaminant.I. ARARI arc
not met.
Remove• contaminanll. AR.Alu arc met.
Eliminates off site migration of contaminant.I.
Same aa Alternative 3.
Same H Alternative 3.
Not applicable.
At least 30 yeara, but not
considered permanent.
Permanent remedy.
Permanent remedy.
Permanent remedy.
Not applicable.
Weathering and cracking of ■luny wall or
other vertical barrier.
Operator error or aystem failure could rcauh
in release of contaminated effluent to tcwer
connection. Pump-and--treat 1y1tem, have
difficulty removing final low concentratiom
from aquifer.
Operator error or 1yst.cm failure could re.ult
in release of contaminated effluent to
groundwater. Pump-and-treat 1y1tenu have
difficulty removing final low concentration,
from aquifer.
Operator error or 1ystem failure could result
in release of contaminated effluent to surface
water. Pump-and--treat 1yst.cnu have difficulty
removing final low concentratioOll from
aquifer.
l!!!!!l!!!!I
NHANFS09.0'l7
I!!!!!!!
- -
I:
2:
3:
4:
S:
----
No Action
Vertical Barrier
Groundwater Extraction and Physical
Treatment (Air Stripping) with
Discharge to P01W
Groundwater Extraction and
Physical/Chemical Treaunent
(Chromium Reduction, Metals
Precipitation, and Air Stripping) with
Discharge Via Spray Irrigation
Groundwater Extraction and
Physical/Chemical Treatment
(Chromium Reduction and Metals
Precipitation) with Discharge to Surface
Water
----- - -- -
TABLE 4-7
SHORT-TERM EFFECTIVENESS AND ™PLEMENTABILITY EVALUATION
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WIIMINGTON, NORTH CAROLINA
Posca no short-term risks.
Small-acale construction may rc111lt i.n the potential
release of a minimal amount of volatile organic a.
Noise nuisance from treatment equipment.
Small-1Cale construction may result in the rcleatc of
volatile organic cmiaaiom from the groundwater. Air
cmiaaiom and noise nuiaaocc from treatment
equipment.
Same as Alternative 3 and residual aludge/filtcr cake
would be generated from filter backwashingprocc~.
Air emissions and noisc nuisance from treatment
equipment.
Residual sludge/filter cake would be generated from
filter backwashing process.
None.
Design and construction of impermeable cap and
vertical barrier.
Recovery of the full extent of the estimated
groundwater plume could take a long time.
Trcatability testing of treatment aystem would be
required to demonstrate ultimate effectiveneaa.
Possible difficulties in acquiring P01W discharge
pennit.
Same as Alternative 3. Design and construction of
spray irrigation 1ysteril neceaaary and special
consideration, for wet weather under freezing
temperature conditiom.
Same as Alternative 3. Design and construction of
4,000-foot discharge pipeline and outfall necessary.
Poasible difficulties in acquiring NPDES discharge
permit.
- -
11!!!!!!!1 -
hnmediately
1.5 years
2 years
2 years
2.5 years
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4.2.3 SHORT-TERM EFFECTIVENESS
Each alternative was examined to determine whether the alternative itself or its
implementation would present any significant risks to public health or the
environment. This evaluation generally involves short-term risks that would occur
only while the alternative is being implemented. A temporary disruption to the
habitat in the immediate New Hanover County Airport Burn Pit Site area would result
from implementing any of the groundwater remedial alternatives. Additional possible
risks include airborne releases of pollutants. The short-term effectiveness evaluation
of each alternative is summarized in Table 4-7.
4.2.4 IMPLEMENTABILITY
For each alternative, constraints to implementation, such as difficult engineering
requirements, the availability of equipment or offsite facilities, and permit and
treatability/pilot study requirements, are considered. Also evaluated under this
category are the labor and time requirements to attain the desired results should the
alternative be implemented. These considerations are summarized in Table 4-7.
4.2.5 COST EVALUATION
The present worth of each alternative provides the basis for the cost comparison. The
present worth cost represents the amount of money that, if invested in the initial year
of the remedial action at a given rate, would provide the funds required to make
future payments to cover all costs associated with the remedial action over its planned
life.
The present worth analysis was performed on all remedial alternatives using a 10
percent discount (interest) rate over a period of 30 years. Inflation and depreciation
4-11
NIIANFS09.024
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were not considered in preparing the present worth costs. The present worth costs for
the remedial action alternatives are summarized in Table 4-8. Appendix C contains
spreadsheets showing each component of the cost summarized in Table 4-8.
4.3 SUMMARY
A detailed evaluation of the remedial action alternatives in terms of cost and non-cost
criteria was described in Section 3. A summary of this evaluation is presented in
Table 4-9 to concisely show the major differences among the remedial action
alternatives with regard to the criteria used: technical effectiveness and
implementability, environmental and public health risk, institutional requirements, and
costs.
4-12
NHANFS09 .024
- - -- --- -- - ---
TABLE 4-8
SUMMARY OF PRESENT WORTH COSTS FOR REMEDIAL ACTION ALTERNATIVES
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
· WILMINGTON, NORTH CAROLINA
1: No Action
2: Vertical Barrier
3: Groundwater Extraction and Physical Treatment (Air Stripping) with Discharge to P0TW
4: Groundwater Extraction and PhysicaVCbemical Treatment (Chromium Reduction, Metals
Precipitation, and Air Stripping) with Discharge Via Spray Inigation
5: Groundwater Extn:ction and Phy1ical/Chcmical Treatment (Chromium Reduction and
Metals Precipitation) with Discharge to Surface Water
NOTES,
(I} Present worth of O&M com for 30 years using a 10 percent interest rate.
Detailed costs arc presented in Appendix C.
0
914.3
794.1
1,042.4
1,120.9
74.7
161.8
357.9
482.7
466.3
- - ---
74.7
1,076.1
1,152.0
1,525.1
1,587.2
- --- - -
I: No Action Ongoing monitoring of
groundwater contami-
nant levels would be
conducted to assess
contaminant migration.
Does not meet
ARARs.
2: Vertical Barrier The potential for
offsite contamination
migration is greatly
reduced. ARARs are
not met at the site.
Length of service
unknown (not perma-
nent).
-
None.
- - - - - -
TABLE 4-9
SUMMARY OF ALTERNATIVES EVALUATION
NEW HANOVER COUNTY AIRPORT BURN PIT SITE
WILMINGTON, NORTH CAROLINA
None. None.
-
Greatly reduces Potential release of Design of slurry wall and im-
mobility. No reduc-organic volatiles . penneable cap; stonnwater
tion in toxicity and during slurry wall runoff drainage and collection
volume. installation. Noise for cap. Air monitoring dur-
nuisance due to ing implementation.
operation of heavy
equipment.
- - ---
0 74.7
1.5 1,076.1
NHANF&J9,0),t
- - - -
3: Groundwater
Extraction and
Physical Treatment
(Air Stripping)
With Discharge to
POlW
--
Permanent remedy.
ARARsarcmet.
---- - - - -
Eliminates MrrN of
contaminants. Elimi-
nates potential for
offsite migration.
High degree of risk
reduction for inges-
tion and inhalation of
groundwater.
TABLE 4-9
(continued)
Potential release of
organic volatiles
during extraction
and treatment sys-
tem operation.
Noise nuisance due
to operation of
drilling equipment.
Design of extraction, treat-
ment, and discharge systems.
Air stripping of benzene to
Nbelow detection limit" re-
quired. Treatment of air strip-
ping off-gases may be re-
quired. Pretreatment for TSS
and iron may be required.
Discharge permit acquisition
under consideration. Ongoing
monitoring of groundwater
contaminant levels and the
treatment system should be
conducted to assess extraction
and treatment systems perfor-
mance. Must meet City of
Wtlmington POlW discharge
requirements and CAA re-
quirements. No future land
use restrictions would be
required.
- - - - -
2 1,152.0
NHANFS09.03-4
- - - - --
4: Groundwater Permanent remedy.
Extraction and Physi-ARARs arc met.
cal/Chemical Treat-
ment (Chromium
Reduction, Meta~
Precipitation, and
Air Stripping) with
Discharge via Spray
Irrigation
--- - - - --
Eliminates MrfN of
contaminants.
Eliminates potential
for offsitc migration.
Greatest degree of
risk reduction for
ingestion and
inhalation of
groundwater.
TABLE 4.9
(continued)
Potential release of
organic volatiles
during extraction
well installation.
Noise nuisance due
to operation of
drilling equipment.
Sludge/filter cake
generation from
precipitate.
Design of extraction, treat-
ment, and discharge systems.
Metals precipitation should
achieve re.quired North
Carolina Drinking Water Qual-
ity Standards for inorganics.
Air stripping should achieve
standards for organics.
Treatment of air stripping off-
gases may be required. Pre-
treatment for TSS and iron
may be required. Storage may
be required during wet weather
and under freezing temperature
conditions. Ongoing monitor-
ing of groundwater contami-
nant levels and the treatment
system should be conducted to
assess extraction and treatment
systems performance. Must
meet North Carolina Drinking
Water Quality Standards for
groundwater and CAA emis-
sions requirements.
-- - --
2 1,525.1
NHANFSl'.19.1134
- - -
S: Groundwater
Extraction and Phys-
ical/Chemical
Treatment (Chromi-
um Reduction and
Metals Precipitation)
with Discharge to
Surface Water
- -
Permanent remedy.
ARARsarcmct.
- - - - -
1!!!!!!!11 l!!!!!!!I
Eliminates MrrN of
contaminants. Re-
duce source of
groundwater
contamination.
Greatest degree of
risk reduction for
ingestion and
inhalation of
groundwater.
TABLE 4-9
(continued)
Potential release of
organic volatiles
during extraction
well installation.
Noise nuisance, due
to operation of
drilling equipment.
Sludge/filter cake
generation from
precipitate.
Design of extraction, treat-
ment, and discharge systems.
Metals precipitation should
achieve North Carolina Surface
Water discharge requirements
for inorganics. A 4,000-foot
pipeline would be required for
discharge to Smith Creek.
Permit acquisition under
consideration. Ongoing
monitoring of groundwater
contaminant levels and the
treatment system should be
conducted to assess extraction
and treatment systems
performance. Must meet
North Carolina Surface Water
discharge requirements.
== iiiii liiiiiil
2.5 1,587.2
NHAN'F509.034
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REFERENCES
Bain, G.L. 1970. Geology and Groundwater Resources of New Hanover County,
North Carolina. U.S. Geological Survey Division of Groundwater, Groundwater
Bulletin Number 17, 72 p.
COM Federal Programs Corporation. April 1992. Final Risk Assessment Report for
the New Hanover County Airport Burri Pit Site, Wilmington, North Carolina.
Choppin and Johnson. 1972. Introductory Chemistry.
Cushnie, George C., Jr. 1984. Removal of Metals from Wastewater. Noyes
Publications, Park Ridge, New Jersey.
Knox, R.C., et al. 1986. National Center for Ground Water Research, University of
Oklahoma, Aquifer Restoration State of the Art.
Noonan, D. and Curtis, J. 1990. Groundwater Remediation and Petroleum: A
Guide for Underground Storage Tanks. Lewis Publishers. ·
Patterson, James W. 1985. Industrial Wastewater Treatment Technology.
Butterworth Publishers, Boston, Massachusetts.
U.S. Environmental Protection Agency, Office of Research and Development,
Cincinnati, Ohio. April, 1980. Carbon Absorption Isotherms for Toxic Organics.
U.S. Environmental Protection Agency. 1989. Evaluation of Groundwater
Extraction Remedies.
U.S. Environmental Protection Agency, Office of Groundwater and Drinking Water.
May 1991. Fact Sheet: National Primary Drinking Water Regulations for Lead
and Copper.
U.S. Environmental Protection Agency, Office of Emergency and Remedial
Response. October 1988. Guidance for Conducting Remedial Investigations
Under Comprehensive Environmental Response, Compensation, and Liability Act
of 1980 --Interim Final.
U.S. Environment Protection Agency. January 1992a. National Oil and Hazardous
Waste Contingency Plan Under Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA).
R-1
NHANFS09.019
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U.S. Environmental Protection Agency, Region IV, Environmental Co.mpliance
Branch, Hazardous Waste Section. January 1992b. Remedial Investigation, New
Hanover ·county Airport, North Carolina.
U.S. Environment Protection Agency. January 1992c. National Emission Standards
for Hu.ardous Air Pollutants, Code of Federal Regulations, Title 40, Part 61,
U.S. Government Printing Office, Washington, D.C., 1973-1990.
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I BORING AND WELL LOGS
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I NHANFS09.022
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A USEPA Region JV MWD-001 Boring Log and Page ~ ESD/ECB/HWS Well Construction Details I of I
PROJECT f: 91£-019 DRILLER: Cl'larles Till, PG
SITE: New Hanover Burn. Pit GEOLOGIST: Jonatl'lan Vail
LOCATION: Wilmington, NC DATE: 04/12/91
~ u ~-.., ..
!~ !JAMPlfl f8 "' .... bl GEOLOGIC OESCRIPT!ON WELL DIAGRAM WELL SPECIFICATIONS w" OE IGNA ON ~~ o-:,
"'?a "'
-5-
.
. •le l op 01 ~asing z.4 H aoove gound,
.
0 -I • SM ~Ill SANO, .,tn ,, sand 'tiers lZ ~ Concrete t'ad 8" thick, •--s0ua,e
. riling performed with 8.2 •, ' Concrete to 2 ft BLS
hoU01111 stem augers. .o .. O< 0 . ""' 7' vi'i'n B1•trtg Grout ~· ~ / 1 . L to. 10s/ga1
/ . ; .. " > 5 -r " " i . , , . .. /
/ . r; r✓ . I/ c:: 10-I/
. ~'. (/ .
r/ V, / . / 1·/
. , / , 1/
15-·' / , ,·, ..; I-Sand Pack to <O It BLS
: . ~ , op or ~creen •17.ow fl-al.S-
. ~ 20-" Screen is 2' 0.01r w~, . Wound Slllnless teet ASTM 304)
" i Fille< Paek ii 20-40 Flin! SanCI.
.. cu•l7Q
..
"
25-:/: ~ .
i,;iottom of ,r-reen e2f_ 19 ft Ql c:: -PrMif -
iX
CL Hollow stem au~rirP ~otlom of Wed wU.BI II BLS IL Y terminate~ at I f BLS . AMPLE 3" sno10y uoe ample collecled
30-for permeabilitr anatosis,
samote inter"a 28·3 .5 ft ,_
Bottom Terminated at JO-:s'ltc!Ls . Bottom 01 ~•ring RJ0.5 II BLS
.
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A USEPA Region IV MWS-001 Boring Log and Page ~ ESD/ECBIHWS Well Cons true tion Details I of/
PROJECT I: 91£-019 DRILLER: Charles Till, PG
SITE: New Hanover Burn-Pit GEOLOGIST: Jonathan Vail
LOCATION: Hilmington, NC DATE: 04/11191
:z: ... :1. !:! "' :.:i iffi OE!l~ON :tg bi GEOLOGIC 0ESCRIPT!ON WELL DIAGRAM WELL SPECIFJCA TI0NS ~ "'3 ~~ ::,
-5-NA
.
. -~ i Top of Casing 2.83 ft aoove ground,
.
G ~ 0 -Concrete Pad e·· thick. J sQuare
SM silty SANO. tan Concrete to lS ft BLS 0 .. b' . ~--.,!a. 0 .
1/ ~ Votctay _Bentonito urout to . ~ 2.4 ft BLS (10.2 lbs/gal)
Bontonite Pellets to . 8 ~ 3.4 ft BLS
SM Silty SANO, oro•n ~ Sand Pack to IS.S ft BLS .
5 -.. = " Top of ScrNn 14.8 ft..,~ ... · -§ .
~ -. § SM SANO. creamy wr.te to
'tts,:•o . Sil y N 111,ith SP send layers ~ ~
~ ~.
. ] Screen is 2" O.Olr Wir, Wound Stainless teOI ASTM 304)
10-~ Filter Peck is 20-40 Flint Sand, cu•l.7Q . . ..
. ~
. ,,
.-. ~
15-=ottom ot r e14_1.n ft
Bottom of Woll 11~.88 ft BLS
Boring Terminated at ts.S ft. Bottom of Boring 015.S It BLS .
.
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.. ·--._ A USEPA Region JV MW0-002 Boring Log and ~ Page
ESO/ECB/HWS Well Cons true tion Details I of/
PROJECT I: 9/E-019 DRILLER: Charles Till, PG
SITE: New Hanover Burn Pit GEOLOGIST: Jonathan va,1
LOCATION: Hllmington, NC DATE: 04/16/91
~ !,! ~-... "' .... f~ ~AMPli il:8 !;! GEOLOGIC DESCRIPTION WELL DIAGRAM WELL SPECIFJCA TIONS ~ OE IGNA ION ~~ "'3 ::,
-5-NA .
.
. • Ii l op of Cuing 2.IQ It aoo,e gound,
.
0 -SM oil~* SANu, i.1th ~,.. _sanct 1g:ters 8 ~ i;;oncrete t'ad e" tl'uck, l sciuare •' . rll ing per I or med 110th 6.2 0 " Concrete to 1.5 fl 8LS hollow stem augers. f -, -Vol~ai{ s1entonit~ Groul to r/ / I•. LS (IQ, lbs/ gal) -~ /
/ -/ ~ 5 -I/ .
[/ . ~ , . /
/ 1/ ~ [/
/ .· .
/
10-. / > , /
. ''., I/ r;, / . I> ~ 1/
/ / ~ I/ . .... ,:.. . . .. . Sand 'ack to ••.• It BL~ 15-.. . . . -.. -.
-: 1 op 01 ~creen w,1 .u It BLS
-.. § "
20-" ., Screen is 2' O.Olf Wlr~ . Wound Stainless tee! ASTM JO•)
., § Filter Pack is 2O-•o Fllnt Sand, . Cu•l.7i
.
.
I 25-
. . . .. .... . ·.· '. II
Boring l erminated at 27.5 It BLS R '"',,llom of :::acrffi ·.rn ft cu c-. ttr,m of W~II 1/."I p cu c:
. Bottom ot ~oring 127.S fl 8LS
30-
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'3i-USEPA Region IV tvlWS-002 Boring Log and Page
ESD/ECBIHWS Well Construction Details I Of/
PROJECT f: 91E-0l9 DRILLER: Cllartes Till, PG
SITE: New Hanover Burn °Pit GEOLOGIST: Jonatllan va,1
LOCATION: Wilmington, NC DATE: 04/15/91
:c ii " ... -OE!~.l'.l.rtoN lg "' .. z ~ GEOLOGIC 0ESCRIPTION WELL 0IAGRAM WELL SPECIFICATIONS
~ cni $~ ::,
-5-NA
.
. -:= i Top of Casing 2.oJ ft at>ove ground,
.
.
G ~ 0 -
Concrete ra<:1 5 .. thick., J. SQuare
.. SM Silly SANO, \llilh ::ir seno layers Concrete to 1.0 fl BLS
~ p
•,' ..
•·
iS
.. .. • e3:31rt"IIE/elleU to ,· [,
-
,· '/ ,· ·:,, 1-;. -,
-
..:. ..:. Sand Pack· to ..... 11 aL:.
.
5 -I: l OP of ScrHn ··~· fl OL~
.
..
~
.. ~ .
~
~
. ..
~ Screen is 2• o.01g-w~,
.. E Wound Sllinltss teet ASTM 304)
10-.. ~ ~ Filter Pack is 20-40 Flint Sand,
~
.. .. § cu•L7i
. ·. : . :, . ~ ~
. •. ~
. ~
.. ~ ~
~
E
15-' • .... .,, ... t r , i!14 K fl
Bottom of Well V14.88 11 BLS
. Soring Terminated at 15.5 II. Bottom of Boring 115.5 11 BLS
.
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A USEPA Region IV MWS-003 Boring Log and ~ Page
ESD/ECBIHWS Well Construction Details I of/
PROJECT f: 91£-019 DRILLER: Charles Till, PG
SITE: New Hanover Burn.Pit GEOLOGIST: Jonathan Vail
LOCATION: 1,mmington, NC DATE: 04/13/91
~ !:! ~-we ., ... ~ ,~ fAMPrfl I§ l;l GEOLOGIC OESCR!PT!ON MELL DIAGRAM WELL SPECIFICATIONS ~ DE IGHA OH
"'3
::,
-5-NA
.
. --,
i Top of Casing 2.,a rt aoo,1 gound,
.
G ~ 0 --Concrete •aa 11· m1ck, J. square
SM silty SANO, aark Dlack 0 ' Concrete to LO ft BLS .. i . 7/ ~ vooc1ay T\ntonite .,,_out le . :/'. 2.0 fl BL (ID.I IDs/gal) . ,;a ~ BentoniJr PeUets 10 ~' , 3.0 ft LS .,,. ,' . -' -' SIOCI Pack to 17.o rt 8L5
' ..
5 -.. ~ TOP oTTcreen a:>.U/ ft BLS .. ·.· .
SM s11p SANO, <lark 0ro1111n. with -S sand layers = ~ -.. ~ . . . .. ~ .. . .
~ Screen ~s 2' 0.01i' Wlr~ Moun4 tlinltss teet ASTM JO•l
10-.. Filter Prk is 20-•0 Flint Sand, . . eu•L7 .. . ~ .. . . .
~ .. .. i .
··•.
: ..
15-. · ffl .. , ~ a, ... ti
.. . Bollom of MeU lt~.01 ft 8L5 . . .
. . . Boring Terminated at 11.0 ft. Bottom of Boring 117.0 ft BLS
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A USEPA Reg,on IV MWS-004 Boring Log ana ~ Page
ESD/ECB/HWS Well Construction Details I of I
PROJECT 1#: 911:-019 DRILLER: Charles Tlll, PG
SITE: New Hanover Burn Pit GEOLOGIST: ·Jonathan Vail
LOCATION: Wilmington, NC DATE: 04/13/91
:z: ... ~ u ~-ii oe:i1t;".l'H10N 1~ ~ ..... GEOLOGIC DESCRIPTION NELL DIAGRAM NELL SPECIFICATIONS ~ "'! ::::,
-5-NA
.
. -~ i Top ol Casing 2.,o It a0O,e ground •
.
.
s ~ 0 -concrete Pad e·· th,ck. 3· sQuare
SM silty SAN□, lllilh :,,-sana laytrs ,, Concrete to LO It BLS .. ,, ,. .
. . . 2. .. .. / ~ Volclay -~\ntonite Griut to 1/, 2.0 fl BL 110.3 lt>s gal) . . -f :.:: e_entoni!e .Pellets to
.. ·, ;, 3.0 It BLS . ;.. :..: sand Pack to 18.0 ft BLS
.
5 -.. .. ·.·. Top of screen ••.u2 tt ~l~ ~ .
. ..
. Screen is 2• o.o~· Nir1
I= Nound St•nlttu teet ASTM 304)
10-Filler ff=k is 20-•0 Flint Sand. : cu•l.
..
.. .. ~ . ·.· .. . .
.. . i
15-.. .. I "ffl r --1•. fl
l:lottom of Ned 114.98 It BLS
Boring Terminated at 18.0 ft. ~ottom or 1:1oring •le.o ft BLS
.
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A USEPA Region IV TB-01 Boring Log aria Page ~ ESDIECB/HWS Well Construction Details I of/
PROJECT II: 91£-019 DRILLER: Cflarles Till, PG
SITE: New Hanover Burn· Pit GEOLOGIST: Jonstflsn Vail
LOCATION: Nilmington, I{(; DATE: 04/09/91 .
~-w-' u .... 5~ fAHPLf lg ~ GEOLOGIC DESCRIPTION WELL DIAGRAM WELL SPECIFICATIONS ~ OE !GNA !ON i~ :::, "'!
0 -~ ~ r\ R'ack sandx L~AH, root zone. r No Wea Installed . rillint"J Ov I lat Auri•r. SM Silty fine SANO, 01ack and grey . .
5 -SM sill Y. fine, ~ANO, yellow-tan-... hite, . wet at S ft. . SP fine SANO, non-plastic white .
10-.
. . SM Silto_ iAr-:(U, with ~,.. sand layers 15-UA 13'
Una01e to continue drilling with . . --slat auger dlJe to cave ,n . . Drilling continued ""'ith mua rotary . . -20-. . . . . . .
25-. . .
11r 30-Silty CL.AY' fitm, light to Clark grey
.
. .
35-SP fine >AND . .
.
40-.. _-~ ~ SAND and CLAY lenses .
SP m_edlum to coarse gr11ne<1 Qllal'tz SANL . lignt grey
45-. . . . .. so-.. . . --. . . . . . . . . . .. 55-.. --. .
60--NX CORE Au usat NX fl! \Y o~ rt . iARRE~ r . X AMPL sanoy tosslliterous L l:f :6'.~N•. ~ . ~ -nnn..nna.tic calcit@. 60• I ft . toudifl!rous
9
Li'!~ S, Nt, 65-~ c•lcite. 61•6 ft. . sandy fossiliferous UME~, ONt., . ca1c,t•. 62-6,.S ft. . f~:silill!rO!~•sll(f i',' ~No, . lc,te. 6 . -6 ft.
70-~oring , erm,nated at oo ft.
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~ USEPA Region IV
ESO/ECB/HWS
PROJECT f: 91£-019
SITE: New Hanover Sur~.Pit
LOCA T!ON: Hilmington, NC
:z: ...
TB-02 Boring Log and
Well Construction Details
DRILLER: Cl'lartes Tlil. PG
GEOLOGIST: Jonatl'lan Vail
DA TE: 04/11/9/
Page
I of I
.. ii Ci:: SAMPLE ~ ~ DESIGNATION
~
GEOLOGIC DESCRIPTION WELL DIAGRAM WELL SPECIFICATIONS
0 -
.
'
.
.
s -.
.
.
.
10-
.
'
'
.
15-
'
.
.
20-
.
.
.
'
25-
'
'
30-
'
'
35-
NA
' .
. :_ ... : .... .. ,·
.· •,
. : .
' ..
. ,,
..
. : ..
SM
SM
CL
lilty SANO Clark Clack
Soring per)ormed -.ith ,. .. solid
stem augers to ascertain depth
ot clay rayer across site ..
Silty SANO, aark brown with :::it"
sand taye,s
Boring T erminat~ at 32 tt
No Wei lnsleUed
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USEPA Region IV
ESD/ECBIHWS
PROJECT t: 91E-019
SITE: Neit Hanov~r Burn Pit
LOCATION: ,,mmington. NC
TB-03 Boring Log and
Well Construction Details
DRILLER: Charles rm. PG
GEOLOGIST: Jonathan Vail
DA TE: 04/11/91
Page
I of/
GEOLOGIC DESCRIPTION WELL DIAGRAM WELL SPECIFICATIONS
0 -NA
.
.
.
5 -
.
.
.
.
.
.
.
15-
.
20-
.
.
.
.
25-
.
.
.
.
30-
. .. . . .
..
.
" .. . . .
.. ..
SM lilly SANOl -ill'I :;.I" sand layers
aorlng per ormed with ~" solid
stem auaers to ascertain depth
of clay rayer across site .
~ CL ~LAY. Otue-gray
--Soring 1 erminal~ at 26 ft
No wen Instaneo
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~-
APPENDIXB
GROUNDWATER ANALYTICAL RESULTS
NHANPS09 .022
--- ---
Inorganic Elemenrs (µg/1)
Aluminum
Barium
Calcium
Chromium
Copper
Iron
Magnesium
Manganese
Nickel
Potassium
Sodium
Strontium
Titanium
Vanadium
Yttrium
Zinc
Pesticide/PCB Compounds
NOTES:
J -Estimated value
------ -
TABLE 2-1
FIRST ROUND GROUNDWATER DATA SUMMARY -APRIL 1991
NEW HANOVER COUNTY AIRPORT SITE
WILMINGTON, NORTH CAROLINA
52,000 56,000 36,000 46,000
99 160· 370 290
25,000 22,000 38,000 28,000
82 72 60 58
21 17 17 12
12,000 28,000 40,000 22,000
3,200 7,700 12,000 7,000
99 360 490 130
36 23 69 69
3,200 4,800 9,000 11,000
37,000 37,000 260,000 250,000
250 480 640 160
180 310 300 220
56 73 63 67
IOU 17 13 17
52 53 62 40
N -Presumptive evidence of presence of material (tentative identification).
U -Material was analyzed for but not detected. Value is quantitation limit.
-Not detected in the sample.
-----
58,000 16,000
92 50
6,300 8,600
65 71
14 IOU
11,000 6,100
2,800 2,600
61 59
33 110
3,500 2U
9,700 6,100
56 59
190 85
60 20
!OU !OU
40 40
NHAN009.0l7
-- ---- -
Extractable Org_anic Come,ounds (µg/1)
Bicycloheptyl
[ (B utoxyetho x y )etho xy ]ethanol
Dihydrodimethylindene
Dihydromethylindene
Dihydronaphthalenone
Dimethylnaphlhalene
2,4-Dimethylphenol
Dimethylphenol (Not 2,4-)
Elhyldimethylbenzene (2 Isomers)
Ethyldimethylbenzene (3 Isomers)
Elhyldimethylbenzene (6 Isomers)
1-Methylnaphthalcne
2-Methylnaphlhalenc
2-Methylphcnol
Methylbcnzcncacetic Acid
Methylbenzenemethanol
Methylpyrrolidinone
Naphthalene
Naphthalic Anhydride
Tetrahydromethylnaphthalene
Tetrahydronaphthalenc
- -
IOU
IOJN
4JN
!OU
IOU
IOJN
3JN
20JN
IOU
3JN
4JN
--
TABLE 2-1
( continued)
3JN
3JN
SJN
6JN
2.31
4JN
20JN
20JN
601
2.71
20JN
6JN
NOTES:
J -Estimated value
N -Presumptive evidence of presence of material (tentative identification).
u -Material was analyzed for but not detected. Value is quantitation limit.
-Not detected in the sample.
--------
40JN
SIN
42J 54 IOU 20U
60JN
201N
JN 100
161 IOU 20U
6.IJ 5.IJ IOU 20U
SOJN
llJ 91 IOU 20U
NHAN009.027
- ----- --- --
TABLE 2-1
(continued)
--- -- - -
11111111111 I'.
Extractable Organic Compounds (µg/1)
(continued)
Tetrahydrothiophencdioxidc
Trimethylbenzoic Acid (3 Isomers)
Trimcthylhcxanoic Acid
2 Unidentified Compounds
5 Unidentified Compounds
Purgeab/e Organic Compounds (µg/1)
Benzene
Carbon Disulfide
Chloroform
1,2-Dichloroethanc
Ethyl Ether
Ethyl Benzene
Ethylmethylbenzene
Methoxymethylpropane
Toluene
Total Xylcnes
Trimethylbenzene
Trimethylbenzene (3 Isomers)
Trimethylbcnzene (2 Isomers)
NOTES:
J -Estimated value
20JN
41N
3.51
25U
2.IJ
IOU
90JN
3.31
10.81
40JN
1.91
25U
IOU
IOU
3001N
8.51
!OJN
2.0J
25.31
80JN
N -Presumptive evidence of presence of material (tentative identification).
U -Material was analyzed for but not detected. Value is quantitation limit.
-Not detected in the sample.
SOOJN
7001N
2001
110
62U
25U
4.41
34
141
821
80JN
600JN
l,OOOJN
900!
110
120U
sou
sou
431
200JN
5.81
19.41
60JN
IU
1.81
2.91
0.891
SU
1U
12U
1.21
SU
SU
NHAN009.027
-
- -----
Purgtabk O!JI.anic Come,ounds (µg/1)
Benzene
Chloroform
l ,2-Dichloroethanc
Dimethyl Pcntanonc
Ethyl Ether
Ethyl Benzene
Ethylmethylbcnzcnc (2 Isomers)
Mcthoxymcthylpropanc
Mcthoxypropanol
Methyl Ethyl Ketone
Mcthylpropanol
Tctrahydrochiophcne
Toluene
Total Xylcncs
Trimethylbcnzcne
Trimcthylbcnzcne (2 Isomers)
Trimcthylbcnzcnc (3 Isomers)
~:
J Estimated value
-------
TABLE 2-3
SECOND ROUND GROUNDWATER DATA SUMMARY -MAY 1991
NEW HANOVER COUNTY AIRPORT SITE
WIIMINGTON, NORTH CAROLINA
I.I 7.7 I.OU I.OU
3.4J 1.11 1.61 0.SIJ
s.ou s.ou s.ou s.ou
JOIN 200JN
1.21 7.4 s.ou s.ou
20JN
sou sou sou sou
IOJN
s.ou Ul s.ou s.ou
4.IJ 21.91 s.ou o.n1
SIN
60JN
N Presumptive evidence of presence of material (tentative identification).
U Material was analyzed for but not detected. Value is quantiiation limit.
Not detected in the sample.
- --·-- -
31 94
UJ 2.IU
IOU 2.71
40JN
9.21 30
IOOJN IOOJN
S0JN
641 2.IOU
201N
201N
2.Sl 131
9.ll 821
SOJN
JOIN
- - -- --
Inorganic Elemenls (µg/1)
Aluminum
Barium
Beryllium
Calcium
Chromium
Cobalt
Copper
Iron
Le.,d
Magnesium
Manganeae
Molybdenum
Nick.cl
Pot.aaaium
Sodium
Strontium
Titanium
Vanadium
Yttrium
Zinc
~:
J Estimated value.
--- -- ---TABLE 2-4
THIRD ROUND GROUNDWATER DATA SUMMARY -NOVEMBER 1991
NEW HANOVER COUNTY AIRPORT SITE
WILMINGTON, NORTH CAROLINA
16000 6600 6200 4500 4700
260 77 75 12 130
1.4 I.OU I.OU I.OU I.OU
13,000 18,000 18,000 2,800 17,000
34 14 12 4.2 II
2.0U 2.0U 2.0U 2.0U 2.2
11 6.2 5,2 2.0U 3.2
16,000 17,000 16,000 1,200 19,000
22 8.0U 8,0U 8.0U 8.0U
1,900 4,600 4,600 230 3,800
41 280 280 2.6 84
2.0U 2.0U 2.0U 2.0U 2.0U
18 4.9 4,1 4.0U 8.1
1,600 2,900 2,800 540 6,600
330
410
I.OU
31,000
30
2.0U
2.7
33,000
8.0U
8,800
350
2.0U
5.8
7,500
31,000 43,000 43,000 870 140,000 240,000
120 290 290 '16 100 350
64 44 41 42 19 10
19 9.S 9.3 6.0 41 12
7,7 2.8 2.7 2.0U 12 3.6
23 17 IS 2.6 14 6.1
N Presumptive evidence of presence of material (tentative identification).
U Material waa analyzed for but not detected. Value is quantitation limit.
Not detected in the sample.
- - -- -
.. '
2400 6700 40U
40 34 2.0U
I.OU I.OU I.OU
5,800 6,100 100
8.1 31 2.0U
2.0U 2.0U 2.0U
2.3 3,2 3.4
5,000 1,800 22
8.0U 8.0U 8.0U
1,300 1,700 20U
21 13 2.0U
2.7 2.7 2.0U
5.S 16 4.0U
880 76-0 400U
10,000 8,400 82,000
40 34 2.0U
17 22 6,1
S.l 6.7 2.0U
2.0U 2.0U 2.0U
9,7 21 7.7
-- - ----
Extraclilbk Organic Compounds (µg/1)
Bcnzoic Acid
Butoxycthanol
Dicthylbenzene
Dihydrodimcthylindcnc
Dihydromethylindcnc
Dihydromethylindenc (2 isomers)
Dihydromethylindcnone
Dihydromcthylnaphthalcnc
Dihydronaphthalcnonc
Dimethylbcnzofuranonc
Dimcthylbcnzoic Acid
DimcthylilObcnzofurandione (2 isomen)
Dimethyli&Obcnzofurandione
Dimethylnaphthalcnc (3 isomen)
Dimethylnaphthalcnc (2 isomcn)
2,4-Dimcthylphcnol
Dimethylpbcnol {not 2,4)
(Dimcthylphcnyl)ethanone
Ethyldimethylbenzenc (2 isomers)
Hcxanoic Acid
Mcthoxymcthylbcnzenc
Mcthyl(propcnyl)benzenc
Mcthylbenzeneacctic Acid
Mcthylbenzcncacctic Acid (2 isomers)
(Mcthylmelhylpropyl)bcnzenc
J Estimated value.
6JN
2JN
IJN
IOU
IJN
N Presumptive evidence of presence of material (tentative identification).
U Material waa analyzed for but not detected. Value ia quantitation limit.
Not detected in the sample.
JJN
IJN
2JN
20JN
8JN
71N
JOJN
3.6J
JIN
8JN
51N
JOJN
- -TABLE 2-4
(continued)
IJN
51N
IOJN
JOJN
3.4J
91N
2JN
IOJN
20JN
8JN
-
IOU
-·-
IOOJN
22J
70JN
-
60JN
41J
40JN
40JN
200JN
- -
20JN
IOU
JJN
-- -
_., .
IOU IOU
-- -- - - --
E:crractabk Organic Compounds (µgn)
(condnued)
1-Mcthylnaphthalenc
2-Mcthylnaphthalcne
Mcthylnaphthalcncacetic Acid
2-Mcthylphcnol
3-and/or 4-Mcthylphcnol
Mcthylpyrrolidinonc
Mcthylpyrrolidone
Naphthalene
Naphthalcneacctic Acid
Naphthalcnccarboxylic Acid
Napbthalcoedicarboxylic Acid
Octahydroindcnone
Petroleum Product
Tctrahydromcthylnaphthalcnc
Tctrahydronaphthalcnc
Tctrahydrothiophcncdioxidc
Tetramcthylbcnzene (2 isomcn)
Tctramcthylbcnzcne
Trimcthylbcnzoic Acid (3 isomers)
Trimethylbcnzoic Acid, Methyl Est.er
Trimethylbcnzoic Acid (2 isomers)
Trimethylphcnol
4 Unidentified Compounds
7 Unidentified Compounds
J Estimated value.
8JN
IOU
IOU
IOU
I.SJ
N
JIN
JIN
JIN
20JN
N Presumptive evidence of presence of material (tentative identification).
U Material was analyzed for but not detected. Value is quantitation limit.
~ot detected in the sample.
20JN
19
3.8J
2.91
40JN
21
IOJN
N
JIN
7JN
60JN
100!
- -TABLE 2-4
(continued)
20JN
18
20JN
3.71
2.61
20JN
20
IOJN
9JN
JIN
N
4JN
6JN
40JN
2JN
50!
---
60JN
IOU IOU
IOU IOU
IOU IOU
IOU 171
40JN
N
200JN
- -- -- -
., . •
IOU IOU IOU IOU
IOU IOU IOU IOU
IOU IOU IOU IOU
IOOU IOU IOU IOU
N
400JN
---- - - - --
Pesticide/PCB Compounds
Pur,g,eable Qrg_anic Come,ounds (µg/1)
Benzene 4.2 7.7
Ethyl Benzene 4.51 8.8
Ethyl Ether 701N 200JN
Ethylmethylbcnzene (2 isomers) 20JN
Mcthoxymethylpropanc
0-Xylcne 9.4 16
Tcrt-Butyl Alcohol
Tctrahydrolhiophcnc
Toluene 5.0U l.lJ
Trimethylbcnzcne (2 isomers) 20JN
Trimethylbcnzeoc (3 isomen) 501N
Trimethylbcnzene
(M-and/or P-)Xylcne 3.71 9.0
NOTES:
J Estimated value.
N Presumptive evidence of presence of material (tentative identification).
U Material was analyzed for but not detected. Value is quantitation limit.
Not detected in the sample.
-TABLE 2-4
(continued)
7.8
8.7
200JN
101N
17
l.lJ
50JN
8.9
-
I.OU
5.0U
5.0U
5.0U
5.0U
--
74
28
lOOJN
7.8J
40JN
30JN
25U
301N
25U
-
llO
371
200JN
271
5.91
60JN
391
-·-
I.OU
5.0U
5.0U
5.0U
5.0U
-
I.OU
5.0U
. '
5.0U
5.0U
5.0U
-
I.OU
5.0U
5.0U
s.ou
s.ou
-
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APPENDIXC
COST ESTIMATES
NHANPS09.022
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Table Nunber: B· 1 :,;• Alternative No.: ,
No Action
Site Name: New Hanover County Airport
Site Location: Wilmington, North Carolina
ITEM DESCRIPTION UNITS
LONG-TERM GROUNDWATER MONITORING
Personnel hour
Supplies each
Annual Well Sa"'1ling & sarrple
Laboratory Testing (6 Wells)
SUBTOTAL
CONT I NGENCY -Cost Based on 10% of Subtotal
TOTAL
ALT1.WK1
PRESENT IIORTH COST
Project Manager: TRC
Date: 05/18/92
ANNUAL UNIT PRICE TOTAL ANNUAL OPERATION PRESENT
QUANTITY DOLLARS COST, DOLLARS TIME, YEARS IIORTH
24 $50 $1,200 30 S11,312
12 S250 $3,000 30 $28,281
6 $500 S3,000 30 S28,281
$7,200 $67,874
$720 $6,787
$7,920 $74,661
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Table Nlllber: 8-2 ~-Alternative No.: 2
Vertical Barrier
Site Name: New Hanover County Airport
SHe Location: ~ilmington, North Carolina
ITEM DESCRIPTION UNITS
FENCING ft
MOBILIZATION
Transport Equipment & Staff each
TefT'f)Orary Facilities each
CAPPING
Site Preparation acre
Cap Mate~ial • 40 ml Liner sqft
Cap Installation acre
Cover Material, Placement, cy
& Grading
Final Grading Material cy
Grading and Compacting acre
Seed and Mulch acre
Geotextile Fabric sqft
Filter Fabric sqft
Bedding Material -Sand & Gravel cy
Oetent ion Pond each
Surface Runoff Collection System each
VERT I CAL BARR I ER
Excavation cy
Cement-Bentonite Slurry sf
Monitor ~ell Installation well
EQUIPMENT & MATERIALS
Health & Safety Equipment each
AIR QUALITY MONITORING week.
MISCELLANEOUS EQUIPMENT & SUPPLIES lt.Jll) sun
Subtotal -Capital Cost
Contractor•s Fee ( 15% of Capital Cost )
Legal Fees, Licenses & Permits C 10X of Capital Cost
Engineering & Acininistrative ( 15X of C8pital Cost)
Subtotal
Contingency ( 10X of Subtotal )
TOTAL CONSTRUCTION COST
PRESENT ~ORTH o&M COST
TOTAL PRESENT IIORTH COST
PRESENT IIORTH COST
Project Manager: TRC
Date: 05/18/92
UNIT PRICE TOTAL COST
QUANTITY DOLLARS DOLLARS
2,000 $20 $40,000
1 $15,000 $15,000
1 $10,000 S10,000
3.4 $3,000 $10,200
150,000 0.45 $67,500
3.4 $4,400 $14,960
1,075 S8 SS,600
530 S8 $4,240
3.4 $7,000 $23,800
3.4 $2,000 $6,800
150,000 0.17 S25 ,500
150,000 0.24 $36,000
1075 $7 $7,525
1 $10,000 $10,000
1 $30,000 $30,000
5,300 S10 $53,000
48,000 $4 $192,000
4 $3,500 $14,000
1 $5,000 $5,000
48 $200 $9,600
1 $10,000 $10,000
$593,725
$89,059
) $59,373
$89,059
$831,215
$83,122
$914,337
$161,766
$1,076,102
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I Table Nurber: B-2 (Cont.$gued) OPERATION & MAINTENANCE COSTS
Alternative No.: 2 Period of Monitoring: 30 years
Vertical Barri er Discount Rate: 10%
Project Manager: TRC
I Site Name: New Hanover County Airport Date: 05/18/92
Site Location: Wilmington, No.rth Carolina
ANNUAL UNIT PRICE TOTAL ANNUAL OPERATION PRESENT
I ITEM DESCRIPTION UNITS QUANTITY DOLLARS COST, DOLLARS TIME, YEARS WORTH
CAP MAINTENANCE AND REPAIR
I Personnel hour 96 $50 $4,800 30 $45,249
Supplies each 12 $500 $6,000 30 $56,561
LONG-TERM GROUNDWATER MONITORING
Personnel hour 16 $50 $800 30 $7,542
I Supplies each 8 $250 $2,000 30 $18,854
Annual Well Sarrpling & SSITf'le 4 $500 $2,000 30 $18,854
laboratory Testing (4 Wells)
I SUBTOTAL $15,600 $147,060
CONTINGENCY -Cost Based on 10% of Subtotal $1,560 $14,706 .
I TOTAL $17,160 $161,766
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I Table Ni..rrber: B-3 ~-PRESENT IIORTH COST
Alternative No.: 3
Alternative: Groundwater Extraction and Physical Treatment
(Air Stripping) with Discharge to POTW
I Site Name: New Hanover County Airport Site Project Manager: TRC
Site Location: Wilmington, North Carolina Date: 05/18/92
UNIT PRICE TOTAL COST
I ITEM DESCRIPTION UNITS QUANTITY DOLLARS DOLLARS
FENCING ft 1,800 $20 $36,000
I MOBILIZATION
Transport Equipment & Staff each 1 $15,000 $15,000
Terrporary Facilities each 1 $10,000 $10,000
I GROUNDWATER EXTRACTION
Site Preparation acre 0.5 $3,000 $1,500
Extraction Well well 3 $3,500 $10,500
Pipes, Valves, & Fittings ft 400 $20 $8,000
I WATER TREATMENT FACILITY
Site Preparation acre 0.5 $3,000 $1,500
Earthwork cy 250 $15 $3,750
I WATER TREATMENT PROCESS UNITS
Equalization Tank each 4 $15,000 $60,000
Pretreatment Facility lurp sun 1 $100,000 $100,000
Air Stripping Unit lurp sun 1 $35,000 $35,000
I T ranfer Pumps each 4 $4,500 $18,000
Piping, Valves, & Appurtenances llfll'I sum 1 $10,000 $10,000
Filter Press each 1 $10,000 $10,000
Instrl.Jllents and Controls turp sun 1 $15,000 $15,000
Electrical lurp sun 1 $10,000 $10,000
I Equipnent Installation lurp sun 1 $49,875 $49,875
DISCHARGE TO POTW
VolllT'IE! Fee 748 gal 9,703 $2.01 $19,503
I Surcharge llJ!l) scm 1 $10,000 $10,000
MISCELLANEOUS EQUIPMENT, & SUPPLIES lurrp sun 1 $20,000 $20,000
ANALYTICAL LABORATORY
I Testing for Process Verification sarrple 144 $500 $72,000
Subtotal -Capital Cost $515,628
I Contractor's Fee ( 15% of Capital Cost ) $77,344
Legal Fees, Licenses & Permits ( 10% of Capital Cost ) $51,563
I Engineering & Adninistrative ( 15% of Capital Cost> $77,344
Subtotal $721,879
I Contingency ( 10% of Subtotal ) $72, 188
TOTAL CONSTRUCTION COST $794,067
PRESENT IIORTH o&M COST $357,966
I TOTAL PRESENT WORTH COST $1,152,033
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Table Nllfber: B·3 (Cont~ed)
Al ternetive No.: 3
Alternative: Groundwater Extraction and Physical Treatment
(Air Stripping) with Discharge to POTW
Site Name: New Hanover County Airport Site
Site Location: Wilmington, North Carolina
ANNUAL
ITEM DESCRIPTION UNITS QUANTITY
GRCXJNDWATER TREATMENT SYSTEM MONITORING
(15 gpm)
ENERGY (15 HP) kwhr 97,985
MAINTENANCE & REPAIR month 11
OPERATING LABOR (24 hours per day) hour 2,920
MISCELLANECXJS CHEMICALS month 11
SHORT-TERM GRCXJNDWATER MONITORING
Personnel hour 288
Supplies each 24
.Weekly Well Sampling & sarrple 144
Laboratory Testing (6 Wells)
LONG-TERM GROUNDWATER MONITORING
Personnel hour 24
Supplies each 12
Annual Well Sampling & safll)le 6
Laboratory Testing (6 Wells)
SUBTOTAL
CONTINGENCY -Cost Based on 10% of Subtotal
TOTAL
OPERATION & MAINTENANCE COSTS
Period of Monitoring: 30 years
Discount Rate: 10%
Project Manager: TRC
Date: 05/18/92
UNIT PRICE TOTAL ANNUAL OPERATION PRESENT
DOLLARS COST, DOLLARS TIME, YEARS IIORTH
$0.07 $6,859 1 $6,235
$3,000 $33,000 1 $30,000
$50 $146,000 1 $132,727
$500 $5,500 1 $5,000
$50 $14,400 1 $13,091
$250 $6,000 1 $5,455
$500 $72,000 1 Jl,5,455
$50 $1,200 29 $11,244
$250 $3,000 29 $28, 109
$500 $3,000 29 $28, 109
$290,959 $325,424
$29,096 $32,542
$320,055 $357,966
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I Table Nl.lTlber: 8·4 :.:• PRESENT IIORTH COST
Alternative No.: 4
Alternative: Groundwater Extraction and Physical/Chemical Treatment
(Chromiun Reduction, Metals Precipitation, and Air
I Stripping) with Discharge Via Spray Irrigation
Site Name: New Hanover County Airport Site Project Manager: TRC
Site Location: Wilmington, North Carolina Date: 05/18/92
I UNIT PRICE TOTAL COST
ITEM DESCRIPTION UNITS QUANTITY DOLLARS DOLLARS
I FENCING ft 3,000 S20 $60,000
MOBILIZATION
Transport Equipment & Staff each 1 $25,000 $25,000
Terrporary Facilities each 1 $15,000 $15,000
I GROUNDWATER EXTRACTION
Site Preparation acre 1 S3,000 $3,000
Extraction Well well 3 $3,500 $10,500
I Pipes, Valves, & Fittings ft 400 $20 SB,000
WATER TREATMENT FACILITY
Site Preparation acre 0.5 $3,000 $1,500
Earthwork: cy 250 S15 $3,750
I Treatment Facility Housing lunp sun 1 $10,000 S10,000
WATER TREATMENT PROCESS UNITS
Equalization Tank each 4 S10,000 $40,000
I Metals Removal Facilities l~ sun 1 $150,000 $150,000
Air Stripping Unit t~ sun 1 $35,000 $35,000
Tranter PllrpS each 4 $2,500 $10,000
Piping, Valves, & Appurtenances l~ sun 1 $15,000 $15,000
Filter Press each 1 $10,000 $10,000
I Instrunents and Controls lunp sum 1 $20,000 $20,000
Electrical lunp SI.Ill 1 $15,000 $15,000
Equi~nt Installation l lfll' s I.Ill 1 $64,375 $64,375
I DISCHARGE VIA SPRAY IRRIGATION
Punps, Piping, Sprinkler Heads llJ'll) SI.Ill 1 $20,000 $20,000
Storage Tanks each 4 $15,000 $60,000
Installation lunp S\.Jll 1 $8,750 $8,750
I MISCELLANEOUS EQUIPMENT & SUPPLIES llfll' SI.Ill 1 $20,000 $20,000
ANALYTICAL LABORATORY
Testing for Process Verification sample 144 $500 $72,000
I Subtotal -Capital Cost $676,875
Contractor's Fee C 15% of Capital Cost) $101,531
I Legal Fees, Licenses & Permits ( 10% of Capital Cost ) $67,688
Engineering & Acininistrative ( 15¾ of Capital Cost) $101,531
I SubtOtal $947,625
Contingency ( 10X of Subtotal ) $94,763
I TOTAL CONSTRUCTION COST $1,042,388
PRESENT IIORTH O&M COST S482, 753
I TOTAL PRESENT IIORTH COST $1,525,140
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Table Nunber: B-4 ( Co~ i,nued)
Alternative No.: 4
Alternative: Groundwater Extraction and Physical/Chemical Treatment
(Chromillll Reduction, Metals Precipitation, and Air
Stripping) with Discharge Via Spray Irrigation
Site Name: New Hanover County Airport Site
Site Location: Wilmington, North Carolina
ANNUAL
ITEM DESCRIPTION UNITS QUANTITY
GROUNDWATER TREATMENT SYSTEM MONITORING
(15 gpm)
ENERGY (20 HP) k.whr 130,650
MAINTENANCE & REPAIR month 11
OPERATING LABOR (12 hours per day) hour 4,380
FLOCCULANTS/COAGULANTS month 11
SLUDGE DISPOSAL drun (55-gal) 33
MISCELLANEOUS CHEMICALS month 11
SHORT-TERM GROUNDWATER MONITORING
Personnel hour 288
Supplies each 24
Weekly Well Salf!)ling & sarrple 144
Laboratory Testing (6 Wells)
LONG-TERM GROUNDWATER MONITORING
Personnel hour 24
Supplies each 12
Annual Well Sarrpling & sample 6
Laboratory Testing (6 Wells)
SUBTOTAL
CONTINGENCY -Cost Based on 10% of Subtotal
TOTAL
OPERATION & MAINTENANCE COSTS
Period of Monitoring: 30 years
Discount Rate: 10X
Project Manager: TRC
Date: 05/18/92
UNIT PRICE TOTAL ANNUAL OPERATION PRESENT
DOLLARS COST, DOLLARS TIME, YEARS IIORTH
$0.07 $9,146 1 $8,314
$4,0DD $44,00D 1 $40,00D
$50 $219,000 1 $199,091
$2,000 $22,000 1 $20,000
$500 $16,500 1 $15,000
$500 $5,500 1 $5,000
$50 $14,400 1 $13,091
$250 $6,000 1 $5,455
$500 $72,000 1 $65,455
$50 $1,200 29 $11,244
$250 $3,000 29 $28,109
$500 $3,000 29 $28,109
$415,746 $438,866
$41,575 $43,887
$457,320 $482,753
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I Table Nllllber: 8-5 ... PRESENT IIORTH COST
Al ternetive No.: 5
Alternative: Groundwater Extraction and Physical/Chemical Treatment
(Chromiun Reduction and Metals Precipitation) with
I Discharge to Surface Water
Site Name: New Hanover County Airport Site Project Manager: TRC
Site Location: Wilmington, North Carolina Date: 05/18/92
I UNIT PRICE TOTAL COST
ITEM DESCRIPTION UNITS QUANTITY DOLLARS DOLLARS
-
I FENCING ft 2,DDO $20 $40,000
MOBILIZATION
Transport Equipment & Staff each 1 $15,000 S15,000
Terrporary Facilities each 1 $1D,DDO $10,000
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GRCXJNDWATER EXTRACTION & REINJECTION
Site Preparation acre 1 $3,000 $3,000
Extraction Well wet l 3 $3,500 $1D,5DD
Pipes, Valves, & Fittings ft 400 $20 SB,000
WATER TREATMENT FACILITY
Site Preparation acre 0.5 $3,000 $1,500
Earthwork cy 250 $15 S3, 750
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WATER TREATMENT PROCESS UNITS
Equalization Tank each 4 $15,000 $60,000
Metals Removal Facility lunp sun 1 $150,DOO $150,000
Equipment Installation lunp sun 1 $66,000 $66,000
Tranfer PLITlps each 4 $2,500 $10,000
Piping, Valves, & Appurtenances lunp sun 1 $10,000 $10,000
Filter Press each 1 $10,000 $10,000
Instrunentation and Controls lunp sun 1 $15,000 $15,000
Electrical lunp sun 1 $10,000 $10,000
EquiJ:,ment Installation l~ sun 1 $69,625 $69,625
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DISCHARGE TO SURFACE WATER
Piping lf 4,000 $25 $100,000
Transfer P~ each 1 $3,500 $3,500
Installation l~ sun 1 $40,000 $40,000
MISCELLANECXJS EQUIPMENT & SUPPLIES lurp sun 1 $20,000 $20,000
I ANALYTICAL LABORATORY
Testing for Process Verification sample 144 $500 $72,000
I Subtotal -Capital Cost $727,875
Contractor's Fee ( 15% of Capital Cost) $109,181
I Legal Fees, Licenses & Permits C 10% of Capital Cost ) $72,788
Engineering & Administrative ( 15% of Capital Cost) $109,181
I Subtotal $1,019,025
Contingency ( 10% of Subtotal ) $101,903
TOTAL CONSTRUCTION COST $1,120,928
I PRESENT IIORTH o&M COST $466,253
TOTAL PRESENT IIORTH COST $1,587,180
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Table Nurber: B-5 (Con"jguedl
Alternative No.: 5
Alternative: Groundwater Extraction and Physical/Chemical Treatment
(Chromiun Reduction and Metals Precipitation) with
Discharge to Surface Water
Site Name: New Hanover County Airport Site
Site Location: Wilmington, North Carolina
ANNUAL UNIT PRICE
ITEM DESCRIPTION UNITS QUANTITY DOLLARS
GROONDWATER TREATMENT SYSTEM MONITORING
(15 91"')
ENERGY (20 HP) lc:whr 130,650 $0.07
MAINTENANCE & REPAIR month 11 $3,000
OPERATING LABOR (12 hours per day) hour 4,380 $50
FLOCCULANTS/COAGULANTS month 11 $2,000
SLUDGE DISPOSAL drun (55-gal) 33 $500
SHORT-TERM GROONDWATER MONITORING
Personnel hour 288 $50
Supplies each 24 $250
Weekly Well Sarrpling & sarrple 144 $500
Laboratory Testing (6 Wells)
LONG-TERM GROONDWATER MONITORING
Personnel hour 24 $50
Supplies each 12 $250
Annual Well Sampling & sample 6 $500
Laboratory Testing (6 Wells)
SUBTOTAL
CONTINGENCY · Cost Based on 10% of Subtotal
TOTAL
OPERATION & MAINTENANCE COSTS
Period of Monitoring: 30 years
Discount Rate: 10%
Project Manager: TRC
Date: 05/18/92
TOTAL ANNUAL OPERATION PRESENT
COST, DOLLARS TIME, YEARS WORTH
$9,146 1 $8,314
$33,000 1 $30,000
$219,000 1 $199,091
$22,000 1 $20,000
$16,500 1 $15,000
$14,400 1 sf3,091
$6,000 1 $5,455
$72,000 1 $65,455
$1,200 29 $11,244
$3,000 29 $28, 109
$3,000 29 $28,109
$399,246 $423,866
$39,925 $42,387
$439,170 $466,253