NCD986187128_20000511_North Belmont PCE_FRBCERCLA LTRA_Treatability Study Evaluation Report for In Situ Bioremediation-OCR

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RESPONSE ACTION CONTRACT
FOR REMEDIAL, ENFORCEMENT OVERSIGHT, AND NON-TIME
CRITICAL REMOVAL ACTIVITIES AT SITES OF RELEASE OR
THREATENED RELEASE OF HAZARDOUS SUBSTANCES
IN EPA REGION 4
U.S. EPA CONTRACT NO. 68-WS-0022
TREAT ABILITY STUDY EVALUATION REPORT
FOR IN SITU BIOREMEDIATION AT THE
NORTH BELMONT PCE SITE,
NORTH BELMONT, GASTON COUNTY, NORTH CAROLINA
')"
"''"' -~ tlt4;-,,,,,r-.
IS'u,.. I <....'/' ,-,~ii;._ ,9 V
Work Assignment No. 071-RDRD-04QD
Document Control No. 3280-071-RT-OTHR-07776
May 11, 2000
Prepared for:
U.S. Environmental Protection Agency
Region IV
Atlanta, Georgia
Prepared by:
COM Federal Programs Corporation
2030 Powers Ferry Road, Suite 490
Atlanta, Georgia 30339
"1l <ooo
v~(Cc
~Ott,
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TABLE OF CONTENTS
Section
LIST OFT ABLES ...................................................... iv
LIST OF FIGURES ...................................................... V
LIST OF ACRONYMS AND ABBREVIATIONS ............................. vi
1.0 INTRODUCTION ................................................. 1-1
2.0 PROJECT DESCRIPTION ........................................... 2-1
2.1 SITE LOCATION AND DESCRIPTION ........................... 2-1
2.2 SITE HISTORY .............................................. 2-1
2.3 ENVIRONMENT AL SETTING .................................. 2-4
2.3.1 SITE GEOLOGY ....................................... 2-5
2.3.2 SITE HYDROGEOLOGY ................................ 2-6
2.4 REMEDIAL INVESTIGATION SUMMARY ....................... 2-8
2.4.1 REMEDIAL INVESTIGATION ........................... 2-8
2.4.2 SUMMARY OF SUPPLEMENTAL INVESTIGATIONS ....... 2-8
2.5 RECORD OF DECISION SUMMARY ........................... 2-10
2.6 REMEDIAL ACTION STRATEGY .............................. 2-10
3.0 IN SITU BIOREMEDIA TION DESCRIPTION AND RES UL TS ............ 3-1
3. I BIOASSESSMENT FIELD STUDY RES UL TS ..................... 3-2
3.1.1 VOLATILE ORGANIC GROUNDWATER CONTAMINATION 3-2
3.1.2 GROUNDWATER GEOCHEMISTRY .................... 3-11
3.1.3 BIOCHEMISTRY ..................................... 3-18
3.2 MICROCOSM STUDY ....................................... 3-30
3.2.l GENERAL TECHNICAL APPROACH .................... 3-30
3.2.2 MATERIALS AND METHODS .......................... 3-31
3.2.3 DAT A ANALYSES .................................... 3-4 I
4.0 CONCLUSIONS .................................................. 4-1
4.1 ENHANCED ANAEROBIC BIOREMEDIA TION FEASIBILITY ....... 4-1
4.2 FULL SCALE EVALUATION ................................... 4-2
5.0 REFERENCES .................................................... 5-1
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LIST OFT ABLES
Table Page
2-1 PERFORMANCE GOALS ........................................ 2-11
3-1 JANUARY1999FIELDVOCDATA ................................ 3-3
3-2 JANUARY 1999 FIELD BIOCHEMICAL AND GEOCHEMICAL
DATA ........................................................ 3-19
3-3 JANUARY 1999 LABORATORY BIOCHEMICAL AND
GEOCHEMICAL DATA ......................................... 3-20 , 3-4 SAMPLING REQUIREMENTS AND ANALYTICAL METHODS ........ 3-32
3-5 NUTRIENT STOCK SOLUTION COMPOSITION .................... 3-33
3-6 COMPONENTS OF RST TRACE METAL AND VITAMIN
SOLUTIONS ................................................... 3-34
3-7 TREATMENTS USED IN MICROCOSM STUDY .................... 3-35
3-8 VOLATILE ORGANIC COMPOUND ANALYSIS FOR THE
MICROCOSM STUDY .......................................... 3-37
3-9 MISCELLANEOUS COMPOUND ANALYSIS FOR THE
MICROCOSM STUDY .......................................... 3-39
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LIST OF FIGURES
Figure
2-1 SITE LOCATION MAP ........................................... 2-2
2-2 NORTH BELMONT PCE AREA .................................... 2-3
3-1 PERCHLOROETHENE-TOP OF BEDROCK GROUNDWATER
PLUME ........................................................ 3-4
3-2 TRICHLOROETHENE-TOP OF BEDROCK GROUNDWATER
PLUME ........................................................ 3-5 3-3 TOT AL 1.2-DICHLOROETHENE-TOP OF BEDROCK
GROUNDWATER PLUME ........................................ 3-6
3-4 PERCHLOROETHENE-BEDROCK GROUNDWATER PLUME ........ 3-7 3-5 TRICHLOROETHENE-BEDROCK GROUNDWATER PLUME ......... 3-8 3-6 TOT AL 1.2-DICHLOROETHENE-BEDROCK GROUNDWATER
PLUME ........................................................ 3-9 3-7 ALKALINITY-TOP OF BEDROCK GROUNDWATER PLUME ....... 3-13 3-8 ALKALINITY-BEDROCK GROUNDWATER PLUME ............... 3-14
3-9 TOTAL ORGANIC CARBON-TOP OF BEDROCK
GROUNDWATER PLUME ....................................... 3-15
3-10 TOTAL ORGANIC CARBON-BEDROCK GROUNDWATER
PLUME ....................................................... 3-16 3-11 DISSOLVED OXYGEN-TOP OF BEDROCK GROUNDWATER
PLUME ....................................................... 3-21
3-12 NITRATE-TOPOFBEDROCKGROUNDWATERPLUME ........... 3-22
3-13 FERROUS IRON-TOP OF BEDROCK GROUNDWATER PLUME ..... 3-23
3-14 SULFATE-TOP OF BEDROCK GROUNDWATER PLUME ........... 3-24
3-15 DISSOLVED OXYGEN-BEDROCK GROUNDWATER PLUME ....... 3-25 3-16 NITRATE-BEDROCK GROUNDWATER PLUME .................. 3-26 3-17 FERROUS IRON-BEDROCK GROUNDWATER PLUME ............ 3-27 3-18 SULFATE-BEDROCK GROUNDWATER PLUME .................. 3-28
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CAH
CDM Federal
DCE
DO
DOC
EAB
EPA
Fe(II)
HPLC
µg/L
mg/L
PCE
ppb
RAMM
RI
ROD
SU
TCE
TOC
vc
voe
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LIST OF ACRONYMS AND ABBREVIATIONS
chlorinated aliphatic hydrocarbon
CDM Federal Programs Corporation
dichloroethene
dissoh·ed oxygen
dissolved organic carbon
enhanced anaerobic biodegradation
U.S. Environmental Protection Agency
ferrous iron
high-performance liquid chromatography
micrograms per liter
milligrams per liter
perchloroethene
parts per billion
revised anaerobic minimal medium
remedial investigation
Record of Decision
standard unit
trichloroethene
total organic carbon
vinyl chloride
volatile organic compound
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1.0 INTRODUCTION
The North Be/mom PC£ Site, Nor1h Be/1110111 Gaston Co11111v. North Carolina: Record of
Decision (ROD) (EPA, 1997a) included in situ biorcmediation as a potential treatment
technology for dissolved phase groundwater contamination at the site. As indicated in the
Data Acquisitions Report for the North Belmont PC£ Site, North Be/mom. North Carolina
(EPA, 1998a), limited data collected from several monitoring wells in December 1997
indicated a low availability of electron acceptors/metabolic products at the site. Evaluation
of this and other data concluded that enhancement of intrinsic biodegradation processes may
be a feasible technology at the site and should be further investigated.
Enhanced anaerobic biodegradation (EAB) relies on the addition of sufficient organic
compounds to contaminated groundwater to induce highly reducing methanogenic conditions
necessary to~iev\ reductive dechlorination of chlorinated solvents. By inducing highly
reducing methanogenic conditions, EAB may improve both the extent and rate of
dechlorination reactions. Inherent in the technically and economically feasible
implementation of EAB is that: (I) site groundwaters have only low levels of alternative
electron acceptors, such that only a minimal addition of organic compound is necessary to
achieve and sustain a highly reduced groundwater environment, (2) the existing microbial
ecology is capable of dechlorinating perchloroethene (PCE) to innocuous end-products,
(3) the addition of electron donor/nutrient mixtures will increase the rate (and extent) of
apparent dechlorination reactions. and (4) EAB can be shown to be protective of human
health and the environment while being cost-effective.
As outlined in the Final Treatabili1y Study Work Plan for 1he North Be/mom PC£ Site, North
Belmont, North Carolina (EPA, 1998b ), additional field data were collected in January 1999,
and a laboratory microcosm treatability study was initiated in February 1999 to further
investigate the potential of enhancing in situ bioremediation processes for remediation of
groundwater contamination at the site.
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The following sections provide an evaluation of field data collected in January l 999 and a
discussion of the laboratory microcosm treatability study results. The four criteria listed
above for technical and economically feasible implementation of EAB were evaluated. It
was determined the EAB is not a feasible technology for the treatment of contaminated
groundwater at the site.
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2.0 PROJECT DESCRIPTION
2.1 SITE LOCATION AND DESCRIPTION
The site consists of two closed dry cleaning operations located in North Belmont, Gaston
County, North Carolina. These two areas are referred to as "Source Area A" and "Source
Area B" (Figure 2-1). Source Area A, which was operated by the Untz family from 1960
to 1975 as a dry cleaning business, is located at Roper's Shopping Center in Land Lot 5,
Parcel I 5-l 8A on Woodlawn Avenue. The shopping center includes Roper's Furniture
Store, a Baptist church, and a cabinet manufacturing shop. The former dry cleaning facility
is approximately 0. 75 acre in size and is bounded to the east and west by residential
neighborhoods, to the north by a cemetery and an undeveloped wooded tract, and to the south
by North Belmont Elementary School. Source Area B is located at the northeastern comer
of Acme Road and Suggs Road in Land Lot 11, Parcel 15-18. This parcel has been converted
to residential property. The majority of the area surrounding Source Area Bis residential
with a few small businesses. A cabinet shop is located to the north. A previous refrigerator
repair shop and a machine shop were also suspected to be potential sources of contamination.
The refrigerator repair shop, now closed, is located at the intersection of Julia Street and
Acme Road in land lot 15-18A, Parcel 32. This is a small commercial strip area with
residential property surrounding the site, except for a cabinet shop and a well drilling
company located to the east. The machine shop is located at the comer of Acme and
Centerview Roads and is encompassed by residential neighborhoods. Figure 2-2 shows the
approximate study area.
2.2 SITE HISTORY
Source Area A was operated by the Untz family from 1960 to 1975 as a dry-cleaning
establishment. A boiler located behind the building was used to "distill" the waste dry
cleaning solvents. The spent solvent residue from the boiler distillation unit was reportedly
disposed onto the ground surface behind the building, and spent solvents were disposed
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CDM FEDERAL RAC VIII
SITE LOCATION MAP
NORTH BELMONT PCE SUPERFUND SITE
COIi FEDERAL PROGRAMS CORPORATION .-...,..,Caa,;p-•-""'·
GASTON COUNTY, NORTH CAROLINA
2-2
NOTTO SCALE
FIGURE NO.
2-1
-
N ' \;.)
-- --
62 LOT NUMBERS
e PRf.\10l.1S ORY Cl.EMILNC fACIUTIES
a Pff£'¥10US REFRIGERATOR REPAIR fACUJTY
■ MACHINE SHOP
o· soo·
""" -w --
-
1000'
---- -- -- -
COM FEDERAL RAC VIII
NORTH BELMONT PCE AREA
NORTH BELMONT PCE SUPERFUND SITE
COIi FEDERAL PROGRAMS CORPORAnON GASTON COUNTY, NORTH CAROLINA .-..,.-~-·--
- ---
N
l
FIGURE NO.
2-2
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through the on-site septic tank system. Source Area B was also operated by the Untz family
prior to moving the dry cleaning establishment to Roper's Shopping Center. Source Area B
was discovered during the site reconnaissance in October 1995 from an interview with a
local resident.
In February 1991, the Gaston County Health Department sampled the well that provided
water to the North Belmont Elementary School and two single family dwellings. This
sampling was associated with an effort by the County to evaluate community water supplies
for volatile organic compounds (VOCs) contamination. The results of this sampling
indicated significant VOC contamination in the well.
U.S. Environmental Protection Agency (EPA) Region 4 Emergency Response was notified.
EPA and the Gaston County Health Department sampled 25 drinking water wells. PCE,
trichloroethene (TCE) and cis-1,2-dichloroethene (1,2-DCE) were detected in sixteen
samples. PCE concentrations were found as high as 15,000 parts per billion (ppb ). The
elementary school was immediately connected to the City of Belmont water system. Twenty-
nine of the neighborhood drinking water wells were taken out of service and connected to
the Belmont city water service. All but 12 of the residential wells were subsequently
abandoned by grouting them to the surface; 12 wells remained intact and were proposed as
monitoring wells. Seven residences in the neighborhood were informed of the contamination
but chose to continue to use their wells and not connect to city water.
2.3 ENVIRONMENT AL SETTING
This section provides a description of the geology and hydrogeoiogy in the site vicinity.
Refer to the North Belmont PCE Site, North Belmont. Gaston County, North Carolina:
Remedial Investigation Report (EPA, 1997b) for more information.
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2.3.l SITE GEOLOGY
The site is located within the central portion of the Charlotte Belt of North Carolina. The
rock types that underlie this terrain are dominated by granitic type rocks, metavolcanics, and
gneisses and schists of varying types. The rock types are of varying metamorphic grade, and
all rock units trend parallel with the strike of the Appalachian Mountains, which is typically
northeast to southwest. These same units typically dip to the southeast along with the
regional topographic trend.
Structurally, the area is complex with rock units displaying one or two types of
metamorphism or structural changes such as faulting or folding. A large, unnamed fault is
located approximately six miles to the west of the site.
According to the Geologic Map ofNorth Carolina, the site is underlain by foliated to massive
metamorphosed quartz diorite and massive to weakly foliated, hornblende rich granitic type
rock. These rock units have undergone periods of deformation that have produced folding
and fracture planes in the rock, as well as brittle zones where the rock is actually crushed,
sheared, or faulted in some manner. As these rock types become weathered, soil profiles
develop that are characteristic of the original rock (also referred to as saprolite).
During the field activities, the soil profile varied with each location; however, a common
pattern was observed. From top to bottom, the materials consist of a saprolite layer, a
partially weathered rock zone, and the underlying fractured crystalline bedrock. The
saprolite is clay-rich, residual material derived from in-place weathering of bedrock.
Typically, the saprolite is silty clay near the surface. With increasing depth, the amount of
mica, silt, and fine~grained sand and gravel tend to increase. Remnant fracture planes with
quartz infilling appear in this layer. The saprolite zone is thickest ( approximately 125 feet)
along the ridgeline on the western edge of the site, thinning towards the lower elevations or
stream valleys to approximately 30 feet in thickness. Underlying the saprolite is a partially
weathered rock layer derived from the weathering of bedrock which ranges in thickness from
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approximately IO to 50 feet. This layer is composed of saprolite and fragments of weathered
bedrock. Particle sizes range from silts and clays to large boulders ofunweathered bedrock.
The weathering occurs in bedrock zones less resistant to physical and chemical degradation
(i.e., fault zones. stress relief fractures, and mineralogic zones). The predominant rock types
appear to be metamorphosed quartz diorite and metamorphosed granite or granitic gneiss.
The bedrock is fractured and these fractures contain quartz deposits that remain unweathered
in the saprolite and therefore are likely to act as confining layers.
2.3.2 SITE HYDROGEOLOGY
Regionally, the water bearing units that underlie the site and surrounding areas represent an
aquifer system consisting of metamorphosed and fractured quartz diorite and granitic type
rocks in varying proportions and thicknesses. Geologic structures that produce high-yielding
wells include contact zones of multi layered rock units, zones of fracture concentration, and
stress-relief fracture zones. Previous studies have indicated that wells in Gaston County that
are set within granite have an average depth of 165 feet and an average yield of 18 gallons
per minute. Within this area, well depths range from 85 to over 1,000 feet and well yields
range from 2½ to I I 6 gallons per minute. The aquifer system underlying the site generally
consists of the saprolite/partially weathered rock aquifer and the underlying bedrock aquifer;
however, interconnection between these units is likely, thereby influencing contaminant
transport. Aquifer designations used during the remedial investigation (RI) for the site are
the saprolite aquifer. the top of bedrock aquifer, and the bedrock aquifer. These same
designations apply to this report.
In the site area, the top of the water table is typically found in the saprolite aquifer and will
generally mimic the overlying land surface. The depth to water across the area ranges from
approximately 3 to 35 feet belmv ground surface. Based on groundwater elevations collected
in November 1996 aquifers generally flow to the northeast to east across the site.
Furthermore, Roper's Shopping Center appears to be positioned within the top ofa localized
groundwater mound with potentiometric contours emanating in a semi-circular pattern from
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this point. Insufficient data of groundwater elevations along the western edge of the site
prevent completion of the potentiometric contours. Based on depth-to-water measurements
for monitoring wells MW-13 and MW-21, groundwater discharges from the saprolite and
bedrock aquifers into the small stream along the northern edge of the site: however, fractures
present in the partially weathered rock and bedrock will affect the direction of groundwater
flow, and relict fractures present in the saprolite may also control groundwater flow
directions. Most of the natural flow in the bedrock system is probably confined to the upper
30 feet of bedrock where fractures are concentrated, and the overlying transition zone which
has the highest hydraulic conductivity.
Data were collected during the 1996/1997 RI for estimating hydraulic gradient and hydraulic
conductivity at the site. The hydraulic gradients for the saprolite and bedrock aquifers were
calculated to be 0.0298 and 0.0275, respectively. Data from rising-head slug tests were used
to calculate hydraulic conductivity in the saprolite and bedrock aquifers. The resultant values
ranged from 0.24 to 1.99 feet/day in the saprolite aquifer and 0.016 to 3.41 feet/day in the
bedrock aquifer.
During the RI, five monitoring wells (MW-14, MW-15, MW-I 8, MW-20, and MW-21) were
examined for identification of geophysical fractures and indications ofhydrologic activity.
Hydrologically active fractures are those that appear to be contributing water to the water
column under static well conditions, and these hydrologically active fractures may potentially
act as contaminant transport pathways. Locations of fractures, strike and dip angles, and
potential hydrologic activity at these locations are outlined in the RI Report (EPA, 1997b).
However, the lateral and vertical extent of the hydrologically active, or potentially active,
fractures were not determined. Furthermore, the interconnectivity of the fractures was not
defined.
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2.4 REMEDIAL INVESTIGATION SUMMARY
2.4.1 REMEDIAL INVESTIGATION
A RI was conducted by EPA to determine the nature and extent of contamination at the site
(EPA. 1997b ). The following briefly summarizes conclusions from the RI Report:
1. The contaminant plume is spreading. Private wells in the vicinity of the site that were
not contaminated in 1991 when EPA first investigated the site are now contaminated.
2. Contamination detected in the shallow aquifer appears to be localized in Source Area
A (Ropers Shopping Center). See Figure 2-1 for source area locations.
3. Contaminants have migrated from the shallow aquifer into the top of bedrock zone and
into the bedrock aquifer. Maximum PCE concentrations detected in the saprolite
aquifer. the top of bedrock aquifer, and the bedrock aquifer during the 1996 RI sampling
were 2200 micrograms per liter (µg/L), 2500 µg/L, and 3500 µg/L, respectively.
4. The source of contamination in the southern edge of the plume may be either Source
Area A or Source Area B.
5. Neither source area contains residual soil volatile organic contamination. It is believed
that the contaminants migrated through the soil directly into the shallow aquifer. VOCs
in surface soil evaporated.
6. Surface water and sediment in the area are not affected by the VOCs.
2.4.2 SUMMARY OF SUPPLEMENT AL INVESTIGATIONS
As described below, two supplemental investigations were performed after the RI. The first
supplemental investigation was conducted during July and August of 1998. The second
supplemental investigation was conducted during January and February of 1999.
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2.4.2.1 .July and August of 1998
As required in the ROD. supplemental field work was conducted in July and August of 1998
to further define the nature and extent of site contamination. Three monitoring wells were
installed, groundwater samples were collected and analyzed, and a limited well survey was
conducted. Details of this investigation are outlined in the Da!a Acquisitions Report for the
North Belmont PC£ Site. North Belmont, North Carolina (EPA, 1998a). The following
briefly summarizes the conclusions of this report:
• Groundwater data indicate that the contaminants of concern identified in the RI (EPA, 1997b) have remained the same.
The data support the existing site conceptual model presented in the RI (EPA, 1997b)
with only a slight change in the distribution around the edges of the plumes.
• The data suggest that biotransformation is occurring at the site.
• A limited response was obtained from site residents during the well survey. Additional survey work will be required to determine which residents (of the ones not currently
connected to city water) desire individual well head treatment units and which residents
desire connection to city water.
2.4.2.2 January and February of 1999
A bioassessment field study was conducted in January of I 999 to further investigate the
potential for enhancing intrinsic anaerobic biodegradation at the site and to develop a
conceptual design for this technology. The study consisted of groundwater sampling and
analysis. The data suggested that enhanced anaerobic biodegradation may be a suitable
technology for the site. Details of this investigation are outlined in the Draft Conceptual
Design Report for the North Belmont PC£ Site. North Belmont. North Carolina (EPA, i 999)
and Section 3 of this report.
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2.5 RECORD OF DECISION SUMMARY
The North Belmont PC£ Site. North Belmont Gaston County. North Carolina: Record of
Decision (EPA, 1997a) recommended that the groundwater remedy consist of the following:
l. Connection of all homes, churches, and businesses in the "North Belmont PCE Area"
to the public water supply.
2. Optional installation of carbon filters on private wells, including one year of filter
operation and maintenance, and filter replacement after one year.
3. Groundwater treatment via in-well vapor stripping and in situ bioremediation.
The goal of this remedial action is to restore the groundwater to its beneficial use. Based on
information obtained during the RI and the analysis of all remedial alternatives, EPA and the
state of North Carolina believe that the selected remedy will be able to achieve this goal. The
selected technologies are proven methods to reduce levels of site-specific contaminants in
groundwater. However, COM Federal Programs Corporation (COM Federal) stresses that
the fractured, heterogeneous. and anisotropic geological conditions at the site make it
difficult to model the extent to which contaminant reductions will occur, especially
considering that in situ bioremediation via EAB is not feasible. The performance goals for
groundwater cleanup arc presented in Table 2-1.
2.6 REMEDIAL ACTION STRATEGY
Previously the remedial action strategy was to clean groundwater contamination using in-
well vapor stripping and EAB. In-well vapor stripping is proposed to address source area
and high concentration portions of the groundwater plume generally within the upgradient
regions of the site. The remaining downgradient portions of the plume were to be addressed
using EAB. However, since EAB is not feasible at the site. a different strategy is ,
recommended.
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TABLE 2-1
PERFORMANCE GOALS
NORTH BELMONT PCE SITE
NORTH BELMONT, NORTH CAROLINA
Contaminant
Methylene Chloride
Cis-1,2-Dichloroethene
Trichloroethene
Perchloroethenc (Tetrachloroethene)
Bis(2-ethylhexy I )phthalate
Chloroform
I, 1-Dichloroethcne
Lead
Remediation Level
5 µg/L
70 µg/L
2.8 µg/L
I µg/L
3 µg/L
I µg/L
I µg/L
15 mg/L
It is recommended that the phased approach described below should be used to address
groundwater contamination at the site.
• Phase I includes connection to city water, wellhead treatment, and in-well vapor
stripping at the source area and high concentration portions of the groundwater
contamination (not the entire plume). Phase I in-well vapor stripping activities will
include the establishment ofa baseline for evaluation of the source area treatment
(not an entire plume baseline), in-well vapor stripping system construction and
operations, followed by an evaluation to determine the effectiveness.
• Phase II operations will address the remainder of the contamination plume. The
remedial actions for Phase II will be determined using the information obtained in
Phase I operations and the EAB treatability study. Data gaps will be identified and
other studies will be completed if required.
All historical analytical data have been reviewed and the following conclusions have been
made.
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• The source area (as represented in MW-6 and CW-6) has recently had comparable
or higher VOC concentrations when compared to historical data. This suggests that
the area around these wells is the main source area. Phase I in-well vapor stripping
should be implemented in and around the main source area. Existing analytical data
is sufiicient to implement Phase I activities. No additional sampling will be
required.
• VOC concentrations in most non-source area wells have not changed significantly
from historical levels. The exceptions are MW-12 and CW-2, which show an
increase in VOC concentrations. Although it is likely that the shape for the plume
has and is changing, it is recommended that this area of the plume be addressed
during Phase II remedial action activities.
COM Federal acknowledges that although there is insufficient data to design a remedy for
cleanup of the entire plume. Additional data should not be collected at this time because
Phase I operations have not been completed and evaluated; therefore, it would not be cost-
effective to completely characterize the entire plume at this time.
It is recommended that the collection of baseline information be targeted to evaluate Phase I
operations and should be completed just prior to implementing the Phase I in-well vapor
stripping. The development and implementation of a groundwater monitoring plan for the
entire site is not recommended at this time for the reasons stated above.
00.0 I 8/3280-071,0510 2-12
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3.0 IN SITU BIOREMEDIATION DESCRIPTION AND RESULTS
The ROD included in situ bioremediation as a potential treatment technology for dissolved
phase groundwater contamination at the site. Limited data collected from several monitoring
wells in December 1997 indicated a low availability of alternate electron acceptors that
would compete with the implementation of EAB at the site (EPA, 1998a). Furthermore, the
natural anaerobic dechlorination of chlorinated aliphatic hydrocarbon (CAH) compounds at
the site is likely limited by the availability of electron donor compounds to drive
dechlorination reactions. Evaluation of this and other data concluded that enhancement of
intrinsic biodegradation processes may be a feasible technology at the site and should be
further investigated.
EAB relies on the addition of sufficient organic compounds to contaminated groundwater
to induce highly reducing methanogenic conditions necessary to achieve reductive
dechlorination of chlorinated solvents. By inducing highly reducing methanogenic
conditions, EAB may improve both the extent and rate of dechlorination reactions. Inherent
in the technically and economically feasible implementation of EAB is that: (I) site
groundwaters have only low levels of alternative electron acceptors, such that only a minimal
addition of organic compound is necessary to achieve and sustain a highly reduced
groundwater environment, (2) the existing microbial ecology is capable of dechlorinating
PCE to innocuous end-products, (3) the addition of electron donor/nutrient mixtures will
increase the rate (and extent) of apparerit dechlorination reactions, and (4) EAB can be
shown to be protective of human health and the environment while being cost-effective.
As outlined in the Final Treatability Study Work Plan for the North Belmont PC£ Site, North
Belmont. North Carolina (EPA, 1998b ), additional field data were collected in January 1999,
and a laboratory microcosm treatability study was initiated in February 1999 to further
investigate the potential of enhancing in situ bioremediation processes for remediation of
groundwater contamination at the site.
OQ.O 18/3280-07 l/OS I 0 3-1
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The following sections provide an evaluation of field data collected in January 1999 and a
discussion of the laboratory microcosm treatability study results.
3.1 BIOASSESSMENT FIELD STUDY RESULTS
A bioassessment field study ,,·as conducted in January 1999 to further investigate the
potential for enhancing intrinsic anaerobic biodegradation at the site and to develop a
conceptual design for this technology. The study consisted of groundwater sampling and
analysis. This section presents the results of groundwater sampling conducted at nine
locations in the top of bedrock aquifer and ten locations in the bedrock aquifer, as outlined
in the Final Treatability Study Work Plan.fir the North Belmont PCE Site, North Belmont,
North Carolina (EPA, 1998b). The following provides an analysis of the collected VOC and
biochemical data. A background discussion of biological systems is provided in the Final
Treatability Study Work Plan for the North Belmont PCE Site, North Belmont, North
Carolina (EPA, 1998b).
3.1.1 VOLATILE ORGANIC GROUNDWATER CONTAMINATION
Analytical results from sampling conducted in January 1999 confirmed the presence of
contaminants of concern identified in the North Belmont PCE Site. North Belmont. Gaston
County, North Carolina: Remedial Investigation Report (EPA, 1997b) and in the Data
Acquisitions Report for the North Belmont PCE Site, North Belmont, North Carolina (EPA,
1998a). The main chlorinated solvents detected (PCE, TCE, and 1,2-DCE) and their
biotransformation products [vinyl chloride (VC), ethene, and ethane] are presented in
Table 3-1. The complete set of analytical results is presented in Appendix D of the Drafi
Conceptual Design Report for the North Belmont PCE Site, North Belmont. North Carolina
(EPA, 1999). PCE, TCE, and 1,2-DCE plots for both the top of bedrock and bedrock
aquifers are presented in Figures 3-1 through 3-6. Data presented in Table 3-1 indicate a
good correlation with data collected during July and August of I 998 and are discussed
separately below for the top of bedrock and bedrock aquifers.
00-01813280-071/05 10 3-2
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TABLE 3-1
,JANUARY 1999 FIELD voe DATA
NORTH BELMONT PCE SITE
NORTH BELMONT, NORTH CAROLINA
Date PCE TCE 1,2-DCE VC
Location ID Sampled (ue/L) /ue/L) (ue/L) (uo/L)
Top of Bedrock Aquifer
TW-OIGW 28-Jan-99 250 I 9J 100 20UJ
NB-MW04DP 25-Jan-99 IOU IOU IOU IOUJ
NB-MW06DP 29-Jan-99 2800 3l0U 770 3l0UJ
NB-MW07DP 22-Jan-99 IOU IOU IOU IOU
NB-MW09DP 2 I-Jan-99 13 IOU IOU IOU
NB-MWIODP 23-Jan-99 IOU IOU IOU IOUJ
NB-MWl2DP 28-Jan-99 170 IOU IOU IOUJ
NB-MWl3SH 20-Jan-99 IOU IOU IOU IOU
NB-CW08DP 24-Jan-99 IOU IOU IOU IOUJ
Bedrock Aquifer
NB-MW03DP 25-Jan-99 59 3J 24 IOUJ
NB-MWl4DP 24-Jan-99 100 IOU 2J IOUJ
NB-MWISDP 22-Jan-99 IOU IOU IOU IOU
NB-MW17DP 20-Jan-99 IOU IOU IOU IOU
NB-MW18DP 24-Jan-99 IOU IOU IOU IOUJ
NB-MW2IDP 19-Jan-99 IOU IOU IOU IOU
NB-MW22DP 2 I-Jan-99 IOU IOU IOU IOU
NB-CW06DP 30-Jan-99 5400 350] 1900 IOOOUJ
NB-CW07DP 29-Jan-99 97 4J 7J IOUJ
NB-PW408DP 30-Jan-99 IOU IOU IOU IOUJ
NOTES:
PCE = pcrchlorocthcne
TCE = trichloroethcnc
1.2-DCE 1,2-dichlorocthcne (total)
VC vinyl chloride
J estimated value
U material was analyzed for but not detected
00-01813280.071,0!i 10
Ethane Ethene
(ue/L) (ue/L)
0.19] 0.20J
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
2.5U 2.6U
-------------------
• Monitoring Well
<10 1999 Treotability
Study Doto
(<1) 1996 RI Data
1" = 500' r-..•c-
250 0 500
MW21•
MW13•
<10 (<1)
CDM FEDERAL RAC VIII
PERCHLOROETHENE(PCE)
TOP OF BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-1
-------------------
t,.)
' V,
LEGEND
• Monitoring Well
<10 1999 Treatability
Study Data
(<1) 1996 RI Data
1" = 500' ,.._.._.
250 0 500
MW13•
<10(<1)
CDM FEDERAL RAC VIII
TRICHLOROETHENE (TCE)
TOP OF BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-2
-------------------
LEGEND
• Monitoring Well
<10 1999 Treatability
Study Data
(<1) 1996 RI Data
1" = 500'
r---?
250 0 500
--·-----.... _.., ____ , __ _
CDM FEDERAL RAC VIII
TOTAL 1,2-DICHLOROETHENE (DCE)
TOP OF BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
,.
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J:
N
FIGURE NO.
3-3
-------------------
LEGEND
• Monitoring Well
<10 1999 Treatability
Study Data
( <1) 1996 RI Data
1" = 500' r--•a-
250 0 500
coNCRETE-.
SUPPlY
---
CDM FEDERAL RAC VIII
PERCHLOROETHENE (PCE)
BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-4
-------------------
w
' 00
• Monitoring Well
<10 1999 Trecitability
Study Data
(<1) 1996 RI Data
1" = 500' r---c-250 0 500
CONCRETE __ _
SUPPlY
----
MW17
_! <10 (~1)
COM FEDERAL RAC VIII
TRICHLOROETHENE (TCE)
BEDROCK GROUNDWATER PLUME
)
I
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-5
-------------------
LEGEND
• Monitoring Well
<10 1999 Treatability
Study Data
(<1) 1996 RI Data
1" ; 500' ,._.?
250 0 500
ration
MW21•
<10 (<1)
CDM FEDERAL RAC VIII
MW17
• <10 (~1) . _
TOTAL 1,2-DICHLOROETHENE (1,2-DCE)
BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
• • I Ji
N
FIGURE NO.
3-6
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Top of Bedrock Aquifer
Figures 3-1 through 3-3 present top of bedrock aquifer field data (PCE, TCE, and 1,2-DCE)
for January 1999. The 1996 top of bedrock field data produced during the RI are also
presented in the figures for comparison purposes. The extent of chlorinated solvent
contamination in the top of bedrock aquifer is similar to that presented in the RI and the Data
Acquisition Report. The highest concentration of PCE was recorded at MW-6 (2,800 µg/L)
and corresponds with elevated biodegradation daughter product concentrations (1,2-DCE =
770 µg/L). Chlorinated contaminants were also detected at TW-0 I (PCE = 250 µg/L, TCE =
19 µg/L, 1,2-DCE = 100 µg/L): MW-9 (PCE = 13 µg/L); and MW-12 (PCE = 170 µg/L).
The presence of PCE and its biodegradation daughter products at MW-6 and TW-0 I provide
evidence ofactive reductive dechlorination reactions in the top of bedrock aquifer. Although
analytical results from the July and August 1998 sampling event at MW-6 indicate
concentrations of PCE (910 µg/L) and 1,2-DCE (310 µg/L) that are substantially less than
those collected in January I 999 [PCE (2800 µg/L) and 1,2-DCE (770 µg/L)], the general
distribution of contaminants is similar. Furthermore, PCE concentrations recorded at MW-9
(13 µg/L) and MW-12 (170 µg/L) in January 1999 are similar to those recorded in July and
August of 1993 (MW-9 = 16 µg/L: MW-12 = 160 µg/L), indicating a good correlation
between the two data sets.
The downgradicnt extent of contamination is defined by CW-8 which had non-detect levels
of chlorinated contaminants. Monitoring wells downgradient of CW-8 (MW-7, MW-I 0, and
MW-13) also had non-detect levels of chlorinated contaminants, indicating that the
chlorinated solvent plume is confined to the upgradient regions of the aquifer.
Bedrock Aquifor
Figures 3-4 through 3-6 present bedrock aquifer field data (PCE, TCE, and 1,2-DCE) for
January 1999. The 1996 bedrock aquifer field data produced during the RI are also presented
in the figures for comparison purposes. The extent of chlorinated solvent contamination in
00-018/]280-071/0510 3-10
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the bedrock aquifer is similar to that presented in the RI (EPA, 1997b) and the Data
Acquisition Report (EPA. 1998a). In general, contaminant (PCE, TCE, 1,2-DCE)
concentrations recorded at CW-6 during 1999 were 20% to 50% higher than those recorded
in 1996. The highest concentration of PCE was recorded at CW-6 (5,400 µg/L) and
corresponds with elevated bi ode gradation daughter product concentrations (TCE = 350 µg/L,
I ,2-DCE = 1,900 µg/L). Chlorinated contaminants were also detected at MW-03 (PCE =
59 µg/L. TCE = 3 µg/L, 1,2-DCE = 24 µg/L); MW-14 (PCE = 100 µg/L, 1,2-DCE = 2 µg/L);
and CW-07 (PCE = 97 µg/L, TCE = 4 µg/L, 1.2-DCE = 7 µg/L). The presence of PCE and
its biodegradation daughter products at several groundwater wells provides evidence of
active reductive dechlorination reactions in the bedrock aquifer.
3.1.2 GROUNDWATER GEOCHEMISTRY
General groundwater chemistry parameters were measured to better define environmental
conditions that can affect the presence and activity of microbial populations across the site.
These general groundwater chemistry parameters are similar for both the top of bedrock and
bedrock aquifers and are therefore discussed together below.
Groundwater pH
Groundwater pH has an effect on the density and activity of microbial populations in
groundwater. Generally, microbes prefer pH values varying from 6 to 8 standard units (SU),
although lower activity levels of some microbes can extend substantially beyond this range.
Non-optimal pH conditions tend to slow reaction rates but do not necessarily inhibit
biological activity unless the specific process (enzyme) is very sensitive to pH. Groundwater
pH values range from 5.5 to 8. 7 SU, with only wells falling slightly outside the optimal pH
6 to 8 range (MW-10, MW-13, MW-03. MW-14, and PW-4.08). This range in pH values
is expected to support biological activity throughout the site.
00-01813280.071,0510 3-11
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Groundwater Temperature
Groundwater temperature directly affects the rate of microbial metabolic activity.
Biodegradation rates roughly double for every I 0-degree Celsius ( 0 C) increase in
temperature. between the temperature range of 5 °C and 25 °C. At temperatures below 5 °C,
metabolic rates are generally too low to be significant, while temperatures above 35 °Care
generally inhibitory to groundwater microbial populations. Groundwater temperatures
ranged from 1·1.3°C (PW-4.08) to 19.2°C (MW-04), and are expected to support moderate
biological activity.
Groundwater Alkalinity
The total alkalinity of a groundwater system is indicative of the capacity of the water to
neutralize acid. Alkalinity results from the presence of hydroxides, carbonates, and
bicarbonates of elements/compounds such as calcium, magnesium, sodium, potassium, or
ammonia. The1;e species result from the dissolution of rock, transfer of carbon dioxide from
the atmosphere, and respiration of microorganisms.
Total alkalinity values throughout the site range from 30 to 195 milligrams per liter (mg/L)
as CaCO3• with background alkalinity values in the top of bedrock aquifer (55 mg/L as
CaCO3) and bedrock aquifer (30 mg/L as CaCOi) among the lowest at the site (Figures 3-7
and 3-8). Alkalinity values elevated above background levels are likely due to influences
from biological activity within contaminated regions. Furthermore, regions of elevated total
alkalinity indicate a moderate ability of groundwater to buffer against pH changes.
Groundwater TOC
Total organic carbon (TOC) groundwater concentrations throughout the site are generally
low, ranging from 3 to 13 mg/L (Figures 3-9 and 3-10). TOC is an indicator of the total
electron acceptor demand within an aquifer and a measure of the energy substrate available
00-018/3280-071,05 I 0 3-12
-------------------
w
' -w
LEGEND
• Monitoring Well
1" = 500' ,._._.
250 0 500
---
MW13•
50
----
COM FEDERAL RAC VIII
ALKALINITY
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I
TOP OF BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-7
-------------------
• Monitoring Well
1" = 500'
~2"
250 0 500
CONCRETE--.
SUPPLY
----
MW21
70 •
CDM FEDERAL RAC VIII
ALKALINITY
MW17 • 115 . -.. -
BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
,
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FIGURE NO.
3-8
-------------------
w ' -Vo
LEGEND
• Monitoring Well
, .. = 500'
ri-----250 0 500
COM Federal Pro
----------
CDM FEDERAL RAC VIII
TOTAL ORGANIC CARBON (TOC)
TOP OF BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-9
-------------------
<.;J
' -°'
LEGEND
• Monitoring Well
1" = 500'
Pi----250 0 500
CONCRCTE -
SUPPLY
COM FEDERAL RAC VIII
MW17 • 3 -----
TOTAL ORGANIC CARBON (TOC)
BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
..
' /:
J
N
FIGURE NO.
3-10
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to drive biodegradation of the CAH compounds. These low TOC levels indicate only limited
electron donors available to: (I) reduce groundwater redox conditions. and (2) drive
reductive dechlorination reactions. Thus. the anaerobic biological dechlorination of CAI-I
compounds at the site is likely to be limited by the availability of sufficient electron donors
(TOC) and suggests enhancement should include the addition of a carbon source.
Macronutrient Availability
Ammonia and ortho-phosphate are essential macronutrients for biodegradation processes.
Ammonia concentrations are generally very low throughout the site (i.e., less than
0.05 mg/L). with the exception of MW-03 (1.76 mg/L). Similarly, ortho-phosphate
concentrations are low throughout the site, with values all falling below 0.5 mg/L. Although
the observed ammonia and ortho-phosphate concentrations are not expected to limit intrinsic
biodegradation processes, amendment of such nutrients would likely be necessary during the
implementation of EAB technologies.
Additional Groundwater Parameters
In addition to the above-mentioned parameters, groundwater samples were analyzed for
chloride, specific conductivity, and turbidity. Chloride and. specific conductivity
measurements were used to distinguish between potentially different hydrologic zones.
Although chloride and specific conductivity values varied throughout the site, values for each
generally fall within one order of magnitude and support the assumption that groundwater
within the top of bedrock and bedrock aquifers is hydraulically connected. Turbidity
measurements were used to determine when groundwater purge water reached "stable"
conditions, thereby verifying that purge water was representative of the local aquifer
formation.
00-01813280-071/0510 3-l 7
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3.1.3 BIOCHEMISTRY
Field and analytical laboratory results for; biochemical and geochemical data are provided in
Tables 3-2 and 3-3 and discussed below. Electron acceptor/metabolic by-product
concentrations are presented in Figures 3-1 I through 3-18.
Electron acceptor/metabolic by-product concentrations were compared at locations within
and outside of contaminated areas to assess intrinsic biodegradation processes occurring at
the site. The comparison required identification of background conditions (i.e .• reference
points) that were representatiw of groundwater upgradient of contaminated regions and
therefore outside the influence of contaminant stimulated microbial activity. Background
conditions for the top of bedrock aquifer are defined by monitoring well MW-04, while
background conditions for the bedrock aquifer are defined by PW-4.08.
Top of Bedrock Aquifer
Electron acceptor and metabolic byproduct data suggest that much of the site is oxidized and
under aerobic conditions (i.e., dissolved oxygen concentrations > 1.0 mg/L). Dissolved
oxygen (DO) concentrations are highest at the background well (MW-04 = 7.1 mg/L) and
only slightly depleted at downgradient locations. The lowest levels of DO are recorded at
TW-01 (3.2 mg/L) and CW-08 (2.0 mg/L) and correspond with the highest levels of TOC
in the top of bedrock aquifer (TW-01 = 12 mg/L; CW-08 = 11 mg/L). These findings
suggest that TOC concentrations may be depleting DO concentrations within the top of
bedrock aquifer; however, sufficient TOC is not available to drive DO concentrations low
enough to be conducive to the reductive dechlorination of chlorinated solvents.
Alternate electron acceptor concentrations within the top of bedrock aquifer that have the
potential to compete with chlorinated solvent biodcgradation (i.e., nitrate, ferric iron, and
sulfate) are low. Nitrate concentrations at the background location (MW-04 = 0.9 mg/L) and
the highest nitrate concentration within the contaminant plume (TW-0 I = 8.6 mg/L) suggest
oo.o 1813:!80-07110510 3-18
----- -- -- --- --- -- ---
TABLE 3-2
JANUARY 1999 FIELD BIOCHEMICAL AND GEOCHEMICAL DATA
NORTH BELMONT PCE SITE
NORTH BELMONT, NORTH CAROLINA
pH Temperature Conductivity Turbidity Alkalinity Chloride Ammonia Phosphate TOC
Location ID Date Sampled (SU) (C) (mS/cm) (NTU) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L)
Top of Bedrock Aquifer
TW-0IGW 28-Jan-99 6.62 17.6 0.26 72 120 6.4 0.01 0.05 12
NB-MW04DP 25-Jan-99 6.93 19.2 0.085 0 55 I. 7 0.01 0.28 3.9
NB-MW06DP 29-Jan-99 7.07 17.2 0.077 0 50 1.9 0.01 0.31 3.2
Nll-MW07DP 22-Jan-99 6.41 17.6 0.244 7.72 85 10.8 0 0.25 4.4,\
Nl3-MW09DP 2 I-Jan-99 6.36 17.4 0.178 29 75 4.3 0.01 0.23 5.2*
NB-MW!0DP 23-Jan-99 5.49 18 0. 198 19.2 70 7.7 0 0.22 10
NB-MWl2DP 28-Jan-99 NA NA NA NA 80 2.2 0.1)1 0.15 8.1
Nll-MWl3SII 20-Jan-99 5.7 16.6 0.18 1.5 50 6 0 0.15 .t.X*
'-'' ' NB-CW081JI' 24-Jan-99 6.52 15.4 0.286 0 105 11.7 !l.ll I 0.21 II
'-0 Bedrock Aquifer
Nll-MW03DI' 25-Jan-99 8.48 18.8 0.348 0 195 7.2 1.76 0.21 8,1
Nll-MWl4IJ1' 24-Jan-99 8.66 17.3 0.134 0 80 2.1 0.01 0.21 4.8
Nll-MWl5DP 22-Jan-99 6.32 17.2 0.236 43 125 23.6 0.04 0.1 13
Nll-MWl7DP 20-Jan-99 7.55 15.7 0. 192 605 115 5.2 0 0.19 3'
NB-MW18DP 24-Jan-99 7.12 16.3 0.223 0 85 10.9 0.02 0. 12 6.8
Nll-MW21DP I 9-Jan-99 6.04 16.4 0.191 4.8 70 5.5 0.01 0.1 2.3A*
NB-~'1\V22DP 2 I-Jan-99 6.48 16.8 0.198 14.2 80 9.3 0 0.17 5.2*
Nll-Cll'06DP 30-Jan-99 7.07 16.2 0.143 0 85 2.4 0 0.31 6.5
N13-CW07DP 29-Jan-99 6.88 17.2 0.223 0 100 4.9 0.0 I 0.19 8.4
NB-PW408DP 30-Jan-99 5.92 14.3 0.095 0 30 4.6 0.01 0.02 7.3
NOTES:
Alkalinily = Alkillinity as cakium carbonate
TOC = Total Organic Carbon. dissolvi.xl
A = Avcragc value
* Includes dissolved and suspended
--- - ------------ ---
TABLE 3-3
JANUARY 1999 LABORATORY BIOCHEMICAL AND GEOCHEMICAL DATA
NORTH BELMONT PCE SITE
NORTH BELMONT, NORTH CAROLINA
DO Nitrate Ferrous Iron Sulfate HS Methane Carbon Dioxide Red ox
Location ID Date Sampled (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (µg/L) (mg/I,) (mV)
Top of BedrtKk Aquifer
TW-OIGW 28-Jan-99 3.23 8.6J 0.04 2 0 I.SJ 30 46.5
NB-MW04DP 25-Jan-99 7.14 0.9J 0 0 0 l.3U IO 188.5
Nll-Mll'06DP 29-Jan-99 7.14 0.05UJ 0.06 4 0 0.54J 15 196
Nll-Mll'07DP 22-Jan-99 6.01 6.2J 0.01 0 0 l.3U 35 136
Nll-MW09Dl' 21-Jan-99 4.75 1.5 0.01 I (I 23A 35 126
Nll-MWIODP 23-Jan-99 6.39 l.6J 0.02 0 0 l.3U 75 238
Nll-Mll'l2DP 28-Jan-99 NA l.3J 0.03 0 I. IJ 35 NA
Nll-MWl3S1-1 20-Jan-99 NA 2.3 0.04 16 0 l.3U 35 205
<.,; Nll-CW08D1' 24-Jan-99 1.98 7.8J (1.01 21 0 l.3IJ 30 197.3 ' Iv Be,lrot·k Aquifer 0
Nll-MW031ll' 25-Jan-99 1.36 4.6J 0 0 0 3400 10 48
NB-MWl4DP 24-Jan-99 5.21 l.4J 0 0 II 0.25J 15 166.J
Nil-MW I 51ll' 22-Jan-99 3.5.l 20J 0.63 0 0 l.3J 60 77
NB-MWl71ll' 20-Jan-99 0.65 2.8 0 II 20 0.38AJ 0 -5,1
NB-MW 181ll' 24-Jan-99 2.65 4.6J 0.12 0 0 l.6AJ 15 30.3
Nll-MW21DP I 9-Jan-99 NA 1.7 0.08 18 0 l.3U 20 126
NB-rv1W22DP 21-Jan-99 3.25 7A 0.07 0 0 16 30 84
NB-CW06DP 30-Jan-99 5.15 l.2J 0 0 0 0.42AJ 15 278
NB-CW07DP 29-Jan-99 4.09 -7.2J 0.1 0 l.2J 15 61.7
NB-PW408DP 30-Jan-99 5. 19 3J 0 0 0 l.3U 30 274
NOTES:
DO Dissolved oxygen
11S Hydrogen sulfide
A A veragc value
J Estimated value
lJ t\faterial was an.:ilyzi:J for but not detected
-------------------
• Monitoring Well
1" = 500'
l"'r--250 0 500
-CONc:RET£--._
SUPPLY
MW12•
---
CDM FEDERAL RAC VIII
DISSOLVED OXYGEN
TOP OF BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-11
- ---- - - - - - -----·-- - -
w ' N N
• Monitoring Well
, .. = 500'
,-.-.. -250 0 500
-CONCRITE---
SUPP>.Y
MW12•.
1.3
---
COM FEDERAL RAC VIII
NITRATE
!
TOP OF BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
• l
)'
N
FIGURE NO.
3-12
-------------------
w ' N w
• Monitoring Well
, .. = 500'
Pi---c-
250 0 500
CDM FEDERAL RAC VIII
FERROUS IRON
TOP OF BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-13
------ - - ----- - - --- - - -
LEGEND
• Monitoring Well
1" = 500' r---.-250 0 500
COM FEDERAL RAC VIII
SULFATE
TOP OF BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-14
--------~----------
w ' N V,
• Monitoring Well
1" = 500' ,-..-?
250 0 500
----
----------------
COM FEDERAL RAC VIII
DISSOLVED OXYGEN
BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
,
l
J.'
N
FIGURE NO.
3-15
-------------------
l,.)
' N
°'
• Monitoring Well
, .. = 500' ,.._..a-
250 0 500
--
MW17 •2.8
--------------·---
COM FEDERAL RAC VIII
NITRATE
/
BEDROCK GROUNDWATER PLUME
/
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-16
--- - - --· ----·-- --- - - -
w ' N --.J
• Monitoring Well
1" = 500' ~--250 0 500
COHCROE ·-
SUPPlY
---
COM Federal Pro ams Co raUon
CDM FEDERAL RAC VIII
FERROUS IRON
BEDROCK GROUNDWATER PLUME
/
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-17
-------------------
l;.)
' N 00
• Monitoring Well
1" = 500' ~-250 0 500
CONCRat ~--
SUPf'LY
~(lil_ --
CDM FEDERAL RAC VIII
SULFATE
BEDROCK GROUNDWATER PLUME
NORTH BELMONT PCE SUPERFUND SITE
NORTH BELMONT, NORTH CAROLINA
N
FIGURE NO.
3-18
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that nitrate is not a significant electron acceptor for this aquifer. The background
concentration of ferrous iron [Fe(II)], the metabolic by-product of ferric iron reduction, is
non-detect and low throughout the site (less than 0.1 mg/L). Finally, sulfate concentrations
at the background location arc non-detect (MW-04) and generally below 5 mg/L, with
exceptions at MW-13 (l 6 mg/L) and CW-08 (21 mg/L). Elevated levels of sulfate at MW-13
and CW-08 may be the result of low-level localized sulfate sources, and do not indicate that
sulfate is a significant electron acceptor for the top of bedrock aquifer. Methane
concentrations are generally below detection limits throughout the site ( ~ 1.5 µg/L ), with the
highest methane concentration at MW-09 (23 µg/L ). Low methane concentrations suggest
that groundwater is not highly reduced and that methanogenic conditions, which are
conducive to the rapid and complete biodegradation of PCE, have not been achieved.
Electron acceptor and metabolic by-product concentrations suggest that the groundwater
within the top of bedrock aquifer is fairly oxidized. However, the minimal presence of
alternate electron acceptors supports the economic and technical feasibility of EAB
technologies for this aquifer since only minimal addition of organic compounds (i.e., electron
donors) should be necessary to achieve and sustain highly reduced groundwater conditions.
Bedrock Aquifer
Electron acceptor and metabolic byproduct data suggest that much of the site is oxidized and
under aerobic conditions. DO concentrations are highest at the background well (PW-4.08 =
5.2 mg/L) and slightly depleted at downgradient locations. The lowest DO concentration was
recorded at MW-17 (0.65 mg/L) and indicates the presence of anaerobic groundwater
conditions. All other downgradient monitoring wells have DO concentrations greater than
l mg/L, thereby indicating aerobic groundwater conditions.
Alternate electron acceptor concentrations within the bedrock aquifer that have the potential
to compete with chlorinated solvent biodegradation (i.e., nitrate, ferric iron, and sulfate) are
low. Nitrate concentrations at the background location (PW-4.08 = 3 mg/L) and the highest
00-018/3280•071/0510 3-29
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nitrate concentration within the contaminant plume (MW-15 = 20 mg/L) suggest that nitrate
is not a significant electron acceptor for this aquifer. The background concentration ofFe(ll)
is non-detect and low throughout the site (less than I mg/L). Finally, sulfate concentrations
at the background location are non-detect (PW-4.08) and generally below I mg/L, with MW-
21 as an exception (18 mg/L). Elevated levels of sulfate at MW-21 may be the result ofa
low-level localized sulfate source and do not indicate that sulfate is a significant electron
acceptor for the top of bedrock aquifer. Methane concentrations are generally low
throughout the site ( ~ 1.5 µg/L). with the primary exception at MW-03 (3,400 µg/L). The
elevated methane concentration at MW-03 indicates highly reduced groundwater conditions
at this location (i.e., methanogenic) which are conducive to the rapid and complete
biodegradation of PCE, provided a fully dechlorinating microbial culture exists.
Similar to the top of bedrock aquifer, electron acceptor and metabolic by-product
concentrations suggest that the groundwater within the bedrock aquifer is fairly oxidized.
However, the minimal presence of alternate electron acceptors supports the economic and
technical feasibility of EAB technologies for this aquifer since only minimal addition of
organic compounds (i.e., electron donors) should be necessary to achieve and sustain highly
reduced groundwater conditions.
3.2 MICROCOSM STUDY
3.2.1 GENERAL TECHNICAL APPROACH
During the January 1999 bioassessment field study, soil and groundwater samples were
collected from a PCE-contaminated region of the top of bedrock aquifer and shipped on ice
to the laboratory. Upon arrival, site soils and groundwater were used to prepare microcosm
test studies, and in some instances, amended with various electron donors (i.e., organic
substrates) and nutrients to determine the dechlorination ability of organisms found at the
site. The following provides a more detailed description of the microcosm setup, operation,
and data interpretation.
00-0 I 8/3280-071/05 JO
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3.2.2 MATERIALS AND METHODS
3.2.2.1 Microcosm Preparation
Microcosms were prepared in an anaerobic glove box containing an atmosphere of 1 to 5%
hydrogen in nitrogen. Fifty (50) grams of homogenized soil were weighed out and dispensed
into 160 mL serum bottles with Tef1on"'-lined, butyl-rubber septa and aluminum crimp caps
(Wheaton 224100-175, autoclaved prior to use for sterilization and to drive off organics that
could potentially interfere with the assay).
Site groundwater was used during preparation of the microcosms. Groundwater was sparged
with nitrogen gas to remove any pre-existing PCE and daughter products-TCE, DCE. and
VC. Sparged groundwater was sampled and analyzed for VOCs, dissolved organic carbon
(DOC), alkalinity, pH, and DO by methods presented in Table 3-4. Supplemental nutrients
were added to the sparged groundwater to achieve final nutrient concentrations equivalent
to those presented in Tables 3-5 and 3-6. Tables 3-5 and 3-6 list nutrient solutions and trace
metal solutions used in the anaerobic biodegradation studies. Groundwater pH was adjusted
to between 6.5 and 7.5 using a phosphate buffer, as necessary. Resazurin, a redox-sensitive
color indicator, was added to the groundwater mixture at 0.5 mg/L. Each serum bottle was
filled with the prepared groundwater mixture to zero-headspace conditions to prevent
partitioning of volatile contaminants into the vapor phase.
Microcosms were prepared as described in Table 3-7. Three separate electron donors
(lactate. benzoate, and molasses) were tested. These electron donors were selected due to
their proven effectiveness in similar anaerobic treatability studies, and their availability in
bulk quantities as commodity products (i.e .. cost-effectiveness). Additional electron donors
were added as required to reach a final equimolar carbon concentration (2.0 mole carbon/L)
for the three various substrates. Sodium lactate (74.7 g/L), sodium benzoate ( 41.2 g/L), and
molasses ( 42 mL/L) were added to the prepared groundwater mixture using concentrated
aqueous stock solution.
00-0 I S/3280-071,0510 3-31
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TABLE 3-4
SAMPLING REQUIREMENTS AND ANALYTICAL METHODS
NORTH BELMONT PCE SITE
NORTH BELMONT, NORTH CAROLINA
Analvte I Method/Reference
Electron Acceptors/Metabolic Byproducts
Dissolved oxygen Dissolved oxygen meter
Nitrate/nitrite EPA 353.1
Iron (II) HACH 8146
Sulfate HACH 8051
Methane/ethane/ethene RSKSOP-175 or SW38 IO modified
Electron Donors
Lactate
Benzoate Fennel et al. (1997)
Acetate
Additional Geochemical Parameters
pH pH meter
Alkalinity HACH 8221
Dissolved organic carbon EPA 9060
Volatile organic comoounds EPA 8021 or 8260 modified*
* See Section 3.2.2 for details on the modified methods.
00-018/3280-07 [105] 0 3-32
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KH,PO,
KH,PO,
NH,CI
CaCl,2H,O
MgCl,2H,O
FeCl,4H,O
TABLE 3-5
NUTRIENT STOCK SOLUTION COMPOSITION
NORTH BELMONT PCE SITE
NORTH BELMONT, NORTH CAROLINA
Comeonent I Concentration (g/L)
RAMM Solution I (use IO mUL of medium?
27.20
34.80
RAMM Solution 2 (use I(} mUL of medium?
53.50
7.35
10. 15
2.00
Trace Metal Solution (use I mL/L of medium)'
Vitamin Solution (use I mL/L of medium)'
1 RAMM = Revised anaerobic minimal medium as per Shelton and Tiedje (I 984). 2 See Table 3-6
00-01 S/3280-071/0510 3-33
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TABLE3-6
COMPONENTS OF RST TRACE METAL AND VITAMIN SOLUTIONS
NORTH BELMONT PCE SITE
NORTH BELMONT, NORTH CAROLINA
Comeonent I Concentration
RST Trace Metal Solution
Nitrilotriacetic acid (adjusted to pH 6.0 with KOH) 2.0 g/L
MnSO,H,O 2.0 g/L
F e(NH, ),(SO,),6H,O 2.0 g/L
CoCI,6H,O 2.0 g/L
ZnS0,7H,O 2.0 g/L
CuCl,2H,O 2.0 g/L
NiCl,6H,0 2.0 g/L
Na,Mo0,2H,0 2.0 g/L
Na,SeO, 2.0 g/L
Na,WO, 2.0 g/L
Vitamin Solution
Biotin 5.0 mg/L
Folic acid 5.0 mg/L
Pyridine-HCI 5.0 mg/L
Riboflavin 5.0 mg/L
Thiamine 5.0 mg/L
Nicotinamide 5.0 mg/L
Pantothenic acid 5.0 mg/L
Cyanocobalamin 5.0 mg/L
p-Aminobenzoate 5.0 mg/L
Lipoic acid (thiotic acid) 5.0 mg/L
00.0 l 8/J280-071/05 IO 3-34
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I Treatment No.
1-3
4-6
7-9
10-12
13-15
16-18
TABLE 3-7
TREATMENTS USED IN MICROCOSM STUDY
NORTH BELMONT PCE SITE
NORTH BELMONT, NORTH CAROLINA
I Descrietion
Unamended Control-Site soil and groundwater only
Killed Control-Site soil and groundwater only, autoclaved with
mercuric chloride added
Positive Control-Lactate, nutrients, site soil and groundwater
inoculated with yeast extract or organisms from Moody Air Force
Base (if available)
Lactate, nutrients. site soil and groundwater
Benzoate. nutrients. site soil and groundwater
De-sulfured molasses. nutrients. site soil and groundwater
I
Microcosm controls consisted of site soil and groundwater without the addition of electron
donors or nutrients, and were used to determine the extent and rate of dechlorination
expected without added organic substrates. Killed microcosm controls consisted of site soil
and groundwater, autoclaved twice over a two-day interval, with mercuric chloride added at
500 ppb to inhibit microbial growth. The killed controls are used to determine loss of
contaminants due to abiotic processes. The positive microcosm controls consisted of site soil
and groundwater, inoculated with yeast extract (200 mg/L final concentration) known to
mediate complete PCE dechlorination to ethene and ethane. The positive control can be used
to indicate the extent of dechlorination expected if all required microorganisms are present
in the soils used in the inoculum.
As a final preparation step, all microcosms were spiked with neat, analytical grade PCE using
autoclaved. gas-tight micro-syringes (glass) to an approximate concentration of I mg/Land
immediately sealed. All microcosms were prepared in triplicate, mixed and allowed to
equilibrate.
00-01813180-071. OS 10 3-35
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Microcosms were incubated at ambient temperatures (20 to 25°e) under quiescent
conditions. Although such temperatures are likely higher than subsurface field conditions,
higher temperatures should accelerate the completion of the microcosm studies. without
seriously altering the relative results and overall outcome of the electron donor comparisons.
3.2.2.2 Sampling and Analyses
Sampling and analysis were performed as described below. Results are presented in
Tables 3-8 and 3-9.
Microcosms were sampled regularly (on the same day) to evaluate the effectiveness of each
treatment. Microcosms were sampled (February 22, 1999) after a 2-day incubation period
(time point "O" zero) to allow for sorption and other processes to reach equilibrium.
Additional samples for voes were collected on the days indicated on Table 3-8. Sampling
volume was minimized to the extent possible to prevent loss of reactive volume during the
long-term testing. Aqueous samples were retrieved by removing the cap and rapidly
sampling the liquid. In addition, sample volume removed was replace by adding solvent-
cleaned, autoclaved (sterile) glass beads. The beads will normalize volume and minimize
headspace in the microcosms which will prevent partitioning of the test contaminant into the
vapor phase.
voe analyses were performed using a modified version of EPA Method 8260 (as shown in
Table 3-4). Modifications to this method were required so that sample extraction volumes
could be minimized.
Analyses for methane, ethene, and ethane were conducted on a limited basis as determined
by visual inspection (i.e., color changes indicated by the presence of Resazurin) and
analytical observations (e.g., gas production, and eAH depletion). Methane, ethane, and
ethene analyses were performed as indicated on Table 3-9. Analyses for methane, ethene,
and ethane were performed using modified versions of SW38 IO to limit sample volume.
OO-0\S/3280•07110510 3-36
--------- --- - ---
<.,J
' <.,J ___,
TABLE 3-8
VOLATILE ORGANIC COMPOUND ANALYSIS FOR THE MICROCOSM STUDY
NORTH BELMONT PCE SITE
PCE
Samr,lc No. (nnb)
I 982
2 1028
3 I 102
Unamended Contrnl Avera2c 1037
4 1239
5 1233
6 1347
Killed Control Averae.e 1273
7 1183
8 1373
9 I 190
Positive Control A veraee 1249
10 1261
11 1214
12 1271
Lactic Acid Substrate Averae.e 1249
13 872
14 929
15 1073
Benzoate Substrate Averae.e 958
16 659
17 857
18 8119
Molasses Substrate Averae.e 775
Incubation Days 2
Time Point 0
NOTES:
Microcosms prepared on 22-Feb-99.
13: Result not significantly greater than blank
ND = Not detected
22-Fcb-99
TCE c-DCE
(nnb) (nnb)
ND ND
ND ND
Nil ND
Nil Nil
ND Nil
Nil Nil
Nil Nil
Nil Nil
Nil ND
ND ND
ND ND
ND ND
ND ND
ND ND
ND ND
ND ND
ND ND
ND ND
ND ND
ND Nil
Nil Nil
Nil Nil
Nil Nil
Nil ND
" Significant pressure buildup noted in several of the bottles.
NORTH BELMONT NORTH CAROLINA .
9-:-..•tar-99" 22-Mar-99~
VC l'CE TCE c-DCE vc PCE TCE c-DCE
(nnb) (nnb) (nnb) (nnb) (nnb) (nnb) (nnb) (nnb)
ND I 151 2.32 ND ND 1368 0.835 ND
ND 1162 1.37 ND ND 1235 0.795 Nil
ND 1120 2.12 ND Nil I 2 I 0 0.733 Nil
Nil 1144 1.94 Nil Nil 1271 0. 788 Nil
ND 1477 0.673 Nil Nil 1748 0.916 Nil
Nil 1096 0.955 Nil Nil 1368 0.770 Nil
ND 1259 0.899 Nil Nil 1611 0. 729 Nil
ND 1277 0.842 ND ND 1576 0.805 ND
ND 1247 0.531 Nil Nil 1867 1.084 Nil
ND 1242 0.816 ND ND 1763 0.842 ND
ND 1312 0.626 ND ND 1472 0.653 ND
ND 1267 0.658 ND ND 1701 0.860 ND
ND 1140 0.563 ND ND 1575 0.856 ND
ND 1327 0.527 ND ND 1552 0.426 ND
ND 1257 0.588 ND ND 1794 0.609 Nil
ND 1241 0.559 ND ND 1640 0.630 ND
ND 1086 0.478 ND 0.455 1250 0.693 ND
ND 1031 0.525 ND 0.496 1092 0.664 ND
ND 1221 0.563 ND ND 1156 0.481 ND
ND 1113 0.522 ND ND 1166 0.613 ND
Nil 1031 2.25 ND 0.870 1356 0. 726 Nil
ND 1175 4.18 ND Nil 19118 0. 718 Nil
Nil 1144 2.74 Nil ND . 888 · 0.640 I ND
ND 1117 3.06 ND ND 1632 0.722 Nil
15 28
13 26
h Sample # I 8 bottle cap popped off on 3/17/99. resulting in the loss of some liquid and an unknown mass of VOCs. Data not used for averaging.
vc
(nnb)
ND
ND
Nil
Nil
Nil
Nil
Nil
ND
Nil
ND
ND
ND
ND
ND
ND
ND
0.263
0.123
0.228
0.193
Nil
Nil
Nil
Nil
PCE
(nnb)
1259
1055
I 198
1170
1865
1409
1445
1573
1359
1304
1227
1297
1221
1730
1756
1569
1368
967
1371
1235
664
789
503
652
42
40
---
5-Anr-99'.
TCE c-DCE VC
(nnb) (nnb) (nnb)
0.9885 ND ND
0 879 ND Nil
Nil Nil Nil
o.,,23 Nil ND
0.6805 Nil Nil
0.6545 · Nil Nil
0.706 Nil Nil
0.6803 ND Nil
1.586 ND ND
0.871 ND ND
ND Nil Nil
0.819 ND ND
ND ND ND
0.7055 Nil Nil
0.541 ND Nil
0.416 ND ND
0.383 ND ND
ND ND ND
0.5255 ND ND
0.303 Nil Nil
Nil Nil Nil
Nil Nil Nil
Nil Nil Nil
Nil ND Nil
' All samples taken from bottles #7 through #18 were depressurized prior to GC injection. Bottles #7, 8, and 9 were later shaken for I hour and reanalyzed with the following results: Sampk No. 7-
PCE = 1308, TCE = ND: Sample No. 8-PCE = 1572, TCE = ND; and Sample No. 9-PCE = 1830.5, TCE = ND .
.1 All samples depressmized
' Standards tested. I mg/L tested as 0.89 mg/L. I I.Itch Method #8146.
1 Standards tested-JO mg/L, 20 mg/L, 30 mg/L. Test rcsults-14 mg/L, 22 mg/L, 29 mg/L. I latch Method #8051.
Jl Standards tested. 0.1 mg/L tested as 0. IO I mg/L. Hatch Method #8507.
'' Standards tested. 0.1 mg/L tested as 0.12 mg/L. Hatch Method #8192.
-
---- -- -- - -----
L,;
' w
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TABLE 3-8 (CONTINUED)
VOLATILE ORGANIC COMPOUND ANALYSIS FOR THE MICROCOSM STUDY
NORTH BELMONT PCE SITE
!'CE
Sample No. (nnb)
I 576
2 517
3 580
Unamended Control Anrae:e 558
4 1064
5 677
6 851
Killed Control AveraPe 864
7 1087
8 675
9 962
Positin Control A vera2e 908
JO 723
I I 803
12 830
Lactic Acid Substrate A veraPe 785
13 893
14 520
15 673
Benzoate Substrate Averaee 695
16 332
17 435
18 262
Molasses Substrate AveraPe 343
Incubation Days 56
Time Point 54
NOTES:
Microcosms prcpan:d on 22-Fl:h-99.
B= Result nol significantly greater than hlank
ND = Not detected
19-Aor-99J
TCE c-DCE
(nnb) (nnb)
1.49 ND
0.87 ND
0.68 ND
I.OJ ND
0.89 ND
0.79 ND
0. 76 ND
0.82 NJJ
1.07 Nil
0.92 Nil
1.80 NIJ
1.26 Nil
ND NIJ
NIJ NIJ
1.88 NIJ
0.63 ND
0.90 ND
0.72 ND
ND ND
0.54 ND
ND ND
ND ND
2.06 ND
0.69 ND
" Significant pressure buildup noted in several of the bottles.
NORTH BELMONT NORTH CAROLINA .
19-Mav-99 3-Jun-99
VC PCE TCE c-DCE VC PCE TCE c-DCE
(nnh) (nnb) (nnh) (nob) (nob) (nob) (nob) (oob)
ND 941 4.04 ND ND 1298 3.25 ND
ND 843 0.31 ND ND 1191 ND ND
ND 860 0.57 ND ND 1935.8 ND ND
ND 881 1.64 ND ND 1475 1.08 ND
ND 848 0.90 ND ND 1118 ND ND
ND 699 ND ND ND 1001 ND ND
ND 836 1.20 ND ND 1112 ND ND
ND 794 0.70 NJJ NJJ 1077 NJJ NJJ
NIJ I 135 0.'13 ND ND 1538 Nil ND
ND 859 2.00 ND Nil 13711 Nil ND
ND 1018 0.38 NIJ NIJ 1430 NIJ NIJ
Nil 1004 1.10 Nil Nil 1446 Nil ND
ND )003 2.68 NIJ NIJ 1292 ND NIJ
ND 1220 0.34 NIJ ND 1121 NIJ NIJ
NJJ 1202 ND NIJ NIJ 1090 ND NIJ
ND 1142 I.OJ ND ND 1168 ND ND
ND 908 ND ND ND 705 ND ND
ND 1561 ND ND ND 661 ND ND
ND 900 ND ND ND 785 ND ND
ND 1123 ND Nil Nil 717 ND Nil
ND 516 ND ND ND 495 ND NIJ
ND 665 ND ND ND 959 ND ND
ND 332 ND ND ND 436 ND ND
ND 504 ND ND ND 630 ND ND
86 JOI
84 99
h Sample # 18 bottle cap p(ipped off on 3/17/99, resulting in the loss of some liquid and an unknown mass of VOCs. Data not used for averaging.
VC
(nob)
ND
ND
ND
ND
ND
ND
ND
NJJ
ND
ND
NIJ
ND
NIJ
ND
NJJ
ND
ND
ND
ND
Nil
NIJ
ND
ND
ND
---
12-Anr-00
PCE TCE c-DCE VC
(nnh) (nnb) (nnh) (nnb)
68 58 ND ND
364 ND ND ND
827 ND ND ND
420 19 ND ND
115 ND ND ND
102 ND ND ND
281 ND ND Nil
166 NJJ NJJ Nil
315 Nil Nil Nil
208 ND Nil Nil
310 Nil Nil Nil
278 ND Nil Nil
284 ND ND ND
372 ND ND ND
375 NIJ ND ND
344 ND ND Nil
359 34 ND ND
278 ND ND ND
23 ND ND ND
220 11 ND ND
175 . ND ND ND
263 NIJ NIJ ND
151 ND NIJ ND
196 Nil ND ND
413
415
' All samples taken from bottles #7 through# 18 were deprcssurizcd prior lo GC injection. Bottles #7, 8, and 9 were later shaken for I hour and reanalyzed with the following results: Sample No. 7-
PCE = 1308, TCE = ND; Sample No. 8-PCE = 1572, TCE = ND; and Sample No. 9-PCE = 1830.5, TCE == ND .
., All samples deprcssurized
~ Standards tested. I mg/L tested as 0.89 mg/L. Hatch Method #8146.
1 Standards tested-IO mg/L, 20 mg/L, 30 mg/L. Test results-I 4 mg/L. 22 mg/L, 29 mg/L. Hatch Method #8051.
11 Standards tested. 0.1 mg/L tested as 0.101 mg/L. Hatch Method #8507.
h Standards tested. 0.1 mg/L tested as 0.12 mg/L. Hatch Method #8192.
-
---- ---- -------- -
TABLE 3-9
MISCELLANEOUS COMPOUND ANALYSIS FOR THE MICROCOSM STUDY
NORTH BELMONT PCE SITE
NORTH BELMONT NORTH CAROLINA
I 3-Anr-99 7-Jun-99 20-Mav-99 4-Jun-99 8-Jun-99 14-Anr-00
Acetate Benzoate Acetate Bcnzoate
Samolc No. (nnm) (nnm) (n•m) (nnm)
I
2
3
Unamended Control AveraPe
4
5
6
Killed Control Averai?e
7
8
9
Positive Control Avernee
10
11
12
Lactic Acid Substrate Averave
13
14
15
Benzoate Substrate AveraPe
16
17
18
Molasses Substrate Averaee
NOTES:
Incubation Days
Time Point
150
259
443
284
50
48
Microcosms prep~n:~ on 22-Feb-99.
B= Result not s1gmficantl} greater lhan blank
ND = Not detected
7802
7461
6011
7091
" Significant pressure 1:mildup noted in several of the hollies.
190
2IO
512
304
l05
l03
I 1596
12404
14244
12748
l\-1cthanc
(nnmv)
ND
ND
ND
ND
0.49
ND
ND
o.i6
39.85
ND
ND
13.28
4.61
0.80
5.20
3.54
Nil
ND
ND
ND
9.28
0.62
2.97
4.29
87
85
Methane
("0 /L)
ND
ND
ND
ND
I. I 6E-02
ND
ND
3.86E-03
9.43E-0l
ND
ND
3.14E-01
1.09E-0I
J.89E-02
l.23E-0 I
8.37E-02
2.20E-01
J.47E-02
7.03E-02
I.0IE-01
Background =
3.831 ppmv
Methane
(nnmv)
ND
ND
7.30
2.43
ND
9.91
ND
3.30
32.87
2.4 I
3.96
13.08
7.99
3.62
7.31
6.31
Nil
ND
1.35
0.45
12.05
ND
3.21
5.09
102
l00
Methane
(ue/L)
ND
ND
1.73E-0l
5.76E-02
ND
2.34E-0l
ND
7.82E-02
7.78E-0l
5.70E-02
9.37E-02
3.09E-0I
l.89E-0l
8.5r,E-02
I. 731'-0 I
1.491:-0 I
Nil
Nil
3.19E-02
l.06E-02
2.85E-0l
ND
7.59E-02
l.20E-01
Background =
3.22 ppmv
Fl..'.2+'-' SO/
(me/L) (mP/1.)
ND 40
I 10
I 10
0.7
I
I
ND
0.7
4
5
6
5
5
4
5
4.7
Nil
ND
ND
ND
1900
400
640
980
l06
104
20
10
ND
ND
3.3
40
50
50
47
60
40
30
43.3
10
ND
10
6.7
50
140
JOO
96.7
l06
l04
~ Sample # 18 bottle cap popped off on 3/17/99, resulting in the loss of some liquid and an unknown mass of VOCs. Data no1 used for averaging.
Fc2+'·
(m<•/1.)
ND
ND
ND
ND
ND
ND
ND
ND
121
106
116
115
121
81
66
89
JO
ND
ND
3.4
3606
1051
1379
2012
417
415
SO/
(me/I.)
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Nil
ND
ND
ND
Nil
ND
ND
ND
ND
ND
ND
ND
417
415
N-NO{
(me/L)
0.2
1.6
2.2
1.3
0.3
0.4
0.3
0.3
0.6
0.4
0.3
0.4
0.3
0.5
0.4
0.4
0.5
0.8
0.4
0.6
0.8
0.4
0.4
0.5
107
l05
-
14-Acr-00
N-NO,'
(me/I.)
(1.08
().()5
0.10
0.IO
(1.05
0.20
0.08
0.IO
0.15
0.18
0. 13
0.20
0.18
11.15
0.211
0.20
11.13
0.15
0.13
0.10
0.13
0.05
0.08
0.10
417
415
' All samples taken from bottles #7 through # 18 were depressurizcd prior to GC injection. Bolllcs #7, 8, and 9 were later shaken tlir I hour and reanalyzed with the following re:;ulh: Sample No. 7-
PCE = 1308. TCE = NJ); Sample No. 8-PCE = 1572. TCE = ND; and Sample No. 9-!'CE= 1830.5,-TCE = ND.
" All samples depressurized
e Standards tested. I mg/L tested as 0.89 mg/L. I latch Method #8146.
1 Standards tested-IO mg/I., 20 mg/L, 30 mg/L. Test rcsults-14 mg/I,, 22 mg/I., 29 mg/L. I latch Method #8051.
~ Standards tested. 0.1 mg/L tested as 0.10 I mg/L. Hatch Method #8507.
1, Standards tested. 0.1 mg/L tested as 0.12 mg/L. !latch Method #8192.
-
--- -- - -- - ----
TABLE 3-9 (CONTINUED)
MISCELLANEOUS COMPOUND ANALYSIS FOR THE MICROCOSM STUDY
NORTH BELMONT PCE SITE
J 1-Jun-99
N-NO/
Samrlt.: No. (mg/L)
I 1.8
2 4.4
3 9.8
Unamended Control Avera!?e 5.3
4 9.7
5 3.7
6 13.6
Killed Control Averae:e J0.7
7 6.7
8 5.4
9 4.6
Positive Control Averai:,e 5.6
JO 8.7
11 8.5
12 9.6
Lactic Acid Substrate Averai;ioe 8.9
13 11.5
14 14.2
15 13.6
Benzoatc Substrate Avera!?e 13.1
16 2.2
17 3.6
18 6.6
Molasses Substrate Ave.-a!?e 4.1
Incubation Days J09
Time Point 107
NOTES:
Microcosms prepared on 22-Fch-99.
B::: Result not significanlly greater than blank
ND "" Not cklcctcd
" Significant pn:ssure buildup noted in sever.ii of the bottles.
NORTH BELMONT NORTH CAROLINA
14-Aor-00 6-Aor-99 7-Jun-99 2 I-Acr-00 18-Anr-00
N-NO,/' Lactate Lactate ()xygcn Methane
(mg/L) (g/L) (e/L) (%) (ncm)
5.2 --6.7 ND
5.5 --11.8 NJ>
6.2 --I 7.5 NIJ
5.6 --12.0 Nil
6.2 --19.5 ND
7.3 --18.5 Nil
7.3 --I 8.3 ND
6.9 18.7 ND
1.0 28.7 25.6 ND 9.8E-0.J
2.1 61.7 16.9 8.6 3.4E-04
1.0 28.3 25.9 ND 7.2E-0.J
1.4 39.6 22.8 2.9 6.8E-04
4.9 26.3 14.5 I I.I 7.6E-05
4.9 30.4 9.6 ND 5.4E-04
3.9 72.4 17.4 ND 6.9E-04
4.6 43.0 13.8 3.7 4.3E-04
ND --2.9 4.1 E-05
NJ> --15.9 8.8E-06
11.5 --18.2 NIJ
0.2 --12.3 J.7E-05
JO --ND I.I E-03
68 --0.2 I. I E-114
36 --23.5 1.9E-04
38 --7.9 4.6E-04
417 43 105 424 421
415 41 J03 422 419
~ Sample # 18 bottle cap popped off on 3/17/99, resulting in the loss of some liquid and an unknown mass of VOCs. Data not used for averaging.
-- -
I 8-Anr-00 18-Acr-00
Ethane Ethc111.:
(""m) (nrm)
ND 2.0E-114
NJ> NJ>
NJ> NJ>
Nil Nil
ND Nil
ND ND
Nil Nil
ND ND
Nil 2.7E-0.J
Nil 2.3 E-0.J
Nil ND
NO l.7E-04
ND l.8E-11.J
Nil ND
ND NJ>
ND ND
I .5E-114 .1.5E-114
Nil NI>
Nil NI>
5.0E-05 l.2E-114
ND 3.SE-114
NIJ 6.6E-11.1
Nil 7.8E-03
Nil 4.9E-03
421 421
419 419
,. All samples taken from bottles #7 through# 18 were de pressurized prior to GC injection. Bottles #7, 8, and 9 were later shaken for I hour and reanalyzed with the following results: Sam pk No. 7-
PCE = 1308, TCE = ND: Sample No. 8-PCE = 1572, TCE = ND; and Sample No. 9-PCE = 1830.5, TCE = ND.
" All samples depressurized
·· St:mdards tested. I mg/L ksted as 0.89 mg/L. Hatch Method #8146.
1 Standards tested-IO mg/L, 20 mg/L, 30 mg/L. Test results-14 mg/L. 22 mg/L, 29 mg/L. Hatch Method #8051.
1 Standards tested. 0.1 mg/L tested as 0.101 mg/L. llatch Method #8507.
1' Stand:irds tested. 0.1 mg/I, tcslcd as 0.12 mg/L. I latch Method #8192.
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Intermittent analysis for electron donors was performed using high-performance liquid
chromatography (HPLC) methods. These analyses were. required for the three sets of
electron donor amended microcosms (lactate. benzoate, and molasses) since depletion rates
of the electron donors are unknown and microcosms may become electron donor-limited
during the duration of the studies. The frequency of electron donor sampling was based on
visual inspection (i.e .. color changes indicated by the presence ofResazurin) and analytical
observations (e.g., gas production and CAH depletion). Analyses for lactate and benzoate
were measured using HPLC equipped with an ultraviolet detector. Lactate and benzoate
analyses were conducted twice for Treatments 7 through 15 (Table 3-7) as indicated on
Table 3-9. Analyses for acetate (an indicator of molasses persistence) were conducted by
aqueous injection to a gas chromatograph equipped with a flame-ionization detector. Acetate
analyses were conducted twice for Treatments 16 and 18 (Table 3-7) as indicated on
Table 3-9.
Analyses for electron acceptors [ nitrate/nitrite, iron (II), and sulfate] were performed on the
days indicated on Table 3-9 using the methods listed on Table 3-4.
3.2.3 DAT A ANALYSES
The following text is an analysis of the data presented in Tables 3-8 and 3-9.
The results from the 421-day microcosm study suggest little enhancement of PCE reductive
dechlorination. In general, average PCE concentrations for each set of microcosm treatments
remained stable through day IO I of incubation. ·Although extended incubation of the
microcosm studies through day 415 indicated an overall loss in average PCE concentrations,
the presence of PCE reductive dechlorination products (e.g., TCE, cis-1,2-DCE, VC, and
ethene) was insignificant, suggesting that PCE losses were due to abiotic mechanisms (e.g.,
sorption and/or volatilization). The relative absence of PCE reductive dechlorination
products suggests that EAB technologies are not a viable option for enhancing the total mass
reduction of target VOCs in situ.
oo.o 18/3280-071/0510 3-41
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Periodic monitoring of amended electron donor compounds (e.g., lactate, benzoate, and
molasses) and their intermediate by-products suggests that sufficient electron donor was
present to drive reductive dechlorination reactions through day 105, and presumably through
the remainder of the study. However. the presence of alternate electron acceptors that
compete with CAI-I reductive dechlorination were elevated throughout the study period, in
particular ferrous iron (Fe''), and suggest a barrier to complete reductive dechlorination of
PCE using EAB technologies. Ferrous iron production results from the biological reduction
of ferric iron in the presence of excess electron donor. Ferrous iron concentrations were
elevated as high as 3.600 parts per million in treatment vessel #16 (Molasses amendment)
and suggest an extremely high concentration ofbioavailable iron that must be overcome prior
to achieving complete anaerobic reductive dechlorination of PCE. The ability to overcome
such a barrier suggests that EAB technologies are likely not cost-effective for treatment of
PCE at the site. It should be noted that high concentrations of bioavailable iron were not
evident from previous field investigations, presumably due to low natural electron donor
availability as indicated by total organic carbon concentrations ( < IO mg/L) recorded during
the January 1999 groundwater sampling event. Consideration of future remedial
technologies at the site should take into account this availability ofbioavailable iron in their
feasibility analyses.
00--018/3280-071105 I0 3-42
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4.0 CONCLUSIONS
4.1 ENHANCED ANAEROBIC BIOREMEDIATION FEASIBILITY
Based on evaluations of field and laboratory data collected to date and discussed above,
enhancement of intrinsic biodegradation processes is not a feasible technology for
remediation of chlorinated solvent contaminated groundwater at the site. The presence of
PCE and its anaerobic biodegradation daughter products (TCE and 1,2-DCE) at numerous
wells \\'ithin both the top of bedrock and bedrock aquifers provided evidence of active
reductive dechlorination reactions. However. a complete anaerobic reductive dechlorination
pathway of PCE to TCE, 1,2-DCE, VC and ultimately innocuous ethene was not evident
from the microcosm study, as the latter two constituents were not detected. Several potential .
reasons for the lack ofVC and ethene detection have been presented in Section 3.2.3.
Groundwater redox conditions, as defined by the distribution of electron acceptors and
metabolic by-products, suggest that the top of bedrock and bedrock aquifers are aerobic and
fairly oxidized. Such conditions are not conducive to the ~eductive dechlorination of PCE
to TCE and 1,2-DCE. The presence of TCE and 1,2-DCE, which are both anaerobic
reductive dechlorination products of PCE, suggests that discrete zones within both aquifers
may exist in which groundwater conditions are highly reduced. These discrete zones may
be present on a micro-scale (e.g., soil grains) or on a macro-scale (e.g., lithologic zones
within a well screen or open borehole). In the latter case, severe concentration well
averaging, resulting from monitoring wells with large screened intervals or. open boreholes,
may be mixing groundwaters from various redox zones, thereby masking the presence of
highly reduced groundwater zones necessary to achieve PCE dechlorination. Evidence
supporting well averaging of various redox zones is apparent at wells in which ferrous iron
or methane were detected with DO concentrations greater than 1 mg/L ( e.g., MW-03, MW-5)
since ferrous iron is rapidly oxidized to an iron oxide under aerobic conditions while
methane is a rapidly consumed substrate.
00-01 s,nso-o; 1,os 10 4-1
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In summary, current data suggest that EAB is not a feasible technology for treatment of
contaminated groundwater at the site. The results of the laboratory microcosm study
suppons this conclusion.
4.2 FULL SCALE EVALUATION
As discussed in Section 4.1, this technology is not recommended for the site. Therefore, a
full-scale evaluation of the technology and a sensitivity analysis identifying the key
parameters affecting full-scale operations was not performed.
00-0 t 813280-071105 !O 4-2
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5.0 REFERENCES
North Belmont PCE Site. North Belmont Gaston County, North Carolina: Record of
Decision (ROD) (EPA. 1997a).
North Belmont PCE Site. North Belmont. Gaston County. North Carolina: Remedial
Investigation Report (EPA, 1997b ).
Data Acquisitions Report/or the North Belmont PCE Site. North Belmont. North Carolina
(EPA, 1998a).
Final Treatahility Study Work Plan/or the North Belmont PCE Site. North Belmont. North
Carolina (EPA, 1998b ).
Draji Conceptual Design Report for the North Belmont PCE Site. North Belmont. North
Carolina (EPA, 1999).
00-01813280-071/05 ]0 5-1