Superfund Record of Decision Naval Surface Warfare-Dahlgren Site 12 Dahlgren VA


                                   EPA/ROD/R03-97/180
                                   1997
EPA Superfund
     Record of Decision:
     NAVAL SURFACE WARFARE CENTER - DAHLGREN
     EPA ID: VA7170024684
     OU01
     DAHLGREN, VA
     09/30/1997

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                                        TABLE OF CONTENTS

    SECTION                                                                                 PAGE

    1.0  THE DECLARATION	1-1
         1.1   SITE NAME AND LOCATION 	 1-1
         1.2   STATEMENT OF BASIS AND PURPOSE	 1-1
         1. 3   DESCRIPTION OF THE SELECTED REMEDY	 1-1
         1. 4   STATUTORY DETERMINATIONS 	 1-2

    2.0  DECISION SUMMARY 	 2-1
         2 .1   SITE NAME,  LOCATION, AND DESCRIPTION	 2-1
         2 . 2   SITE HISTORY AND ENFORCEMENT ACTIVITIES	 2-1
         2.2.1 History of Site Activities	 2-1
         2.2.2 Previous Investigations	 2-5
         2.2.3 Enforcement Actions 	 2-5
         2.2.4 Highlights of Community Participation	 2-5
         2 .3   SCOPE AND ROLE OF RESPONSE ACTION AT SITE 12	 2-6
         2.4   SUMMARY OF SITE CHARACTERISTICS	 2-6
         2.4.1 Sources of Contamination 	 2-6
         2.4.2 Description of Contamination	 2-9
         2.4.3 Contaminant Migration	 2-10
         2 . 5   SUMMARY OF SITE RISKS	 2-10
         2.5.1 Human Health Risks	 2-11
         2.5.2 Environmental Evaluation	 2-13
         2.5.3 Development of Preliminary Remediation Goals  (PRGs)	 2-14
         2.6   DESCRIPTION OF ALTERNATIVES	 2-20
         2 .7   SUMMARY OF THE COMPARATIVE ANALYSIS OF ALTERNATIVES 	 2-25
         2.7.1 Threshold Criteria	 2-25
         2.7.2 Primary Balancing Criteria	 2-26
         2.7.3 Modifying Criteria 	 2-28
         2 . 8   THE SELECTED REMEDY 	 2-28
         2.8.1 Performance Standards	 2-29
         2 . 9   STATUTORY DETERMINATIONS 	 2-31
         2.9.1 Protection of Human Health and the Environment 	 2-31
         2.9.2 Compliance with ARARs 	 2-31
         2.9.3 Cost-Effectiveness 	 2-32
         2.9.4 Utilization of Permanent Solutions and Alternative Treatment Technologies
               or Resource Recovery Technologies to the Maximum Extent
               Practicable 	 2-32
         2.9.5 Preference for Treatment as Principal Element	 2-32

    3.0  RESPONSIVENESSS SUMMARY 	 3.1
         3.1   BACKGROUND ON COMMUNITY INVOLVEMENT 	 3-1

    APPENDICES

    Appendix A.   Commonwealth of Virginia Concurrence with the Selected Remedy
    Appendix B    Responsiveness Summary
    Appendix C    Applicable or Relevant and Appropriate Reguirements

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                                            LIST OF FIGURES

    NUMBER                                                                        PAGE

     2-1           NSWCDL Location Map 	 2-2

     2-2           IR Site Locations 	 2-3

     2-3           Area Site Map, Site 12 - Chemical Burn Area 	 2-4

     2-4           Estimated Area of Soil Contamination Above PRGs 	 2-7

     2-5           Estimated Area of Groundwater Contamination Above PRG's 	 2-8


                                            LIST OF TABLES

    NUMBER                                                                         PAGE

     2-1          Ecological Risk Management 	 2-15

     2-2          Summary of Surface Soil PRGs 	 2-17

     2-3          Summary of Subsurface Soil PRGs 	 2-18

     2-4          Summary of Groundwater PRGs 	 2-19

     2-5          Summary of Remediation Goals 	 2-30
                                    1.0 THE DECLARATION
1.1
        SITE NAME AND LOCATION
Site 12 Chemical Burn Area
Naval Surface Warfare Center
Dahlgren, Virginia
1.2
        STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for Site 12 Chemical Burn Area
at the Naval Surface Warfare Center, Dahlgren Site (NSWCDL)  Dahlgren, Virginia.  This

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document focuses on remedial decisions for Site 12 at the NSWCDL and the term "site" in this
document refers to Site 12. This determination has been made in accordance with the
Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) , as
amended by Superfund Amendments and Reauthorization Act of 1986 (SARA) , and to the extent
practicable, the National Oil and Hazardous Substances Pollution Contingency Plan (NCP).
This decision is based on the administrative record for this site.

The Commonwealth of Virginia concurs with the selected remedy (see Appendix A).

ASSESSMENT OF THE SITE

Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the response action selected in this Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare, or the environment.

1.3 DESCRIPTION OF THE SELECTED REMEDY

The Navy will manage the remediation of the Chemical Burn Area in two phases. The remedial
action selected in this Record of Decision (ROD) addresses contamination associated with
Site 12 Chemical Burn Area contents, surface soils, subsurface soils and groundwater.
Possible contaminated surface water and sediments in Gambo Creek near Site 12 will undergo
further evaluation as part of the Gambo Creek Ecological Assessment and a separate ROD will
be issued for Gambo Creek.

The selected remedy for Site 12 is to remove volatile organic contaminants from groundwater and
soils using an air sparging/soil vapor extraction system (AS/SVE), and provide institutional
controls, and groundwater, surface water, and sediment monitoring. No action is reguired for
surface soils at Site 12.

The major components of the selected remedy are:

The Navy shall install an AS/SVE system which consists of at least two air injection wells in
the source area as defined in Figure 2-4. The vapor extraction system shall consist of at least
two vapor extraction wells located in the source area and along the downgradient plume, as
defined by the groundwater monitoring network. The optimum number of AS/SVE wells shall be
determined by the pilot-scale study.

The Navy shall monitor the extracted vapors to ensure compliance with EPA and Virginia ARARs
and TBCs as they are discharged to the atmosphere. There will be no air emission controls on
the AS/SVE system, and initially up to 25 pounds per day of VOCs removed from groundwater is
expected to be vented to the atmosphere. Emissions at these levels are expected to be short-
term during the installation and pilot-testing of the system.

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property file maintained at Engineering Field Activity, Chesapeake (EFA Ches) (US Navy) for this
site indicating the extent of the area and the fact that solid wastes are present. The
institutional controls shall also include the following: Within 90 days after completion of the
remedy, the Navy shall produce a survey plat prepared by a professional land surveyor registered
by the Commonwealth of Virginia indicating the location and dimensions of disposal area and the
extent of groundwater contamination. Monitoring well locations shall be included and identified
on the survey plat. The plat shall contain a note, prominently displayed, which states the
owner's future obligation to restrict disturbance (excavation or construction) of the property;
post-closure use of the property shall prohibit residential use, access or use of groundwater
underlying the property for any purpose except monitoring, and shall not disturb the function of
the monitoring systems. The owner of the property shall submit the survey plat to the local
recording authority when closure is complete. If and when the property is transferred out of
the federal government, the deed (or some other instrument which is normally examined during
title search at the local land recording authority) shall include the survey plat and shall
contain a notation notifying any potential purchaser of the property that the land has been used
to manage solid waste. An appropriate deed restriction shall be placed on the site-specific
deed when a deed is created in the future for property transfer.

The Navy shall institute groundwater monitoring at the perimeter of the groundwater plume. The
freguency of analysis and the length of time for monitoring shall be developed in the Operation
and Management Plan.

The Navy shall monitor the surface waters and sediments in Gambo Creek adjacent to Site 12.
The freguency of analysis and the length of time for monitoring shall be developed in the
Operation and Management Plan.

Implementation of the selected remedy will address the principal threats at the site by reducing
the potential risk to human health and the environment associated with the subsurface soils and
groundwater. Additionally, this remedy would be able to address the potential presence of Dense
Non-Agueous Phase Liguid (DNAPL) beneath the site.

1.4 STATUTORY DETERMINATIONS

The selected remedy for Site 12 is protective of human health and the environment, complies
with Federal and State reguirements that are legally applicable or relevant and appropriate to
this action, and is cost-effective.

The selected remedy for Site 12 addresses the remediation of subsurface soils and groundwater
contamination at Site 12. The selected remedy will provide for the long-term reduction of
contamination in subsurface soils and groundwater beneath the site. The installation of an air
sparging/soil vapor extraction system will reduce direct contact and ingestion threats and
reduce risks to ecological receptors from contaminated subsurface soils and groundwater by
removing contaminants from these media.

The selected remedy for Site 12 will be constructed to meet all applicable or relevant and
appropriate reguirements (ARARs) whether chemical-, action-, or location-specific. No waivers
of any ARARs are reguested. Air sparging/soil vapor extraction is a permanent solution and is
an appropriate remedy for volatile organic contamination in soils and groundwater. Air sparging
is an innovative technology whose application at Site 12 is considered technically superior to
other alternatives.

This remedy utilizes permanent solutions and alternative treatment (or resource recovery)
technologies to the maximum extent practicable for this operable unit, and satisfies the
statutory preference for treatment as a principal element.

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A review will be conducted within five years after commencement of the remedial action to
ensure that the remedy provides adequate protection of human health and the environment.

2.0 DECISION SUMMARY

2.1 SITE NAME, LOCATION, AND DESCRIPTION

This Record of Decision (ROD) is issued to describe the Department of the Navy's (Navy)
selected remedial actions for Site 12, Chemical Burn Area, at the Naval Surface Warfare Center,
Dahlgren Site (NSWCDL), Dahlgren, Virginia (Figure 2-1). The Chemical Burn Area is one of
several Installation Restoration (IR) sites (Figure 2-2) located at the NSWCDL facility. Site
12 is situated on the Mainside of the base and is bounded on its western side by Gambo Creek
(Figure 2-3).

The Chemical Burn Area, which included a small pit, was used for burning lab chemicals,
solvents, polymers, glues, metallic hardware and equipment, and small quantities of
decontaminated chemical warfare agent (CWA) solution. The former pit and associated facilities
were located in a fenced, cleared area of the site at the end of a dirt access road off of Bagby
Road (Figure 2-3). The size of the pit is estimated from aerial photography to be approximately
50 feet square. An employee of the area stated that in the early 1970s the pit was
approximately 20 feet long by 20 feet wide and 4 feet to 6 feet deep.

Adjacent land has been used for the disposal of ordnance-related wastes (Site 2), as an aerial
bombing range, and as a natural habitat for native plant and animal species. A Remedial
Investigation (RI) and Feasibility Study (FS) has been conducted at the adjacent Site 2, and a
separate Record of Decision is being prepared to address that site. Laboratory and office space
are located within 1,500 feet to the northeast of Site 12 and within 1,000 feet to the southwest
of the site.

Surface drainage from Site 12 is generally overland directly to Gambo Creek. Gambo Creek is
located approximately 350 feet west of the former burn pit. Because the highest ground is near
the center of the clearing, there is some surface runoff in the opposite direction toward a
drainage ditch east of Bagby Road, which drains into an unnamed tributary of Gambo Creek.

Groundwater production wells supplying potable water to NSWCDL are over 600 feet deep and
are located over 4,000 feet south of Site 12. These wells are unaffected by contaminants
related to Site 12. Depth to the surficial groundwater at Site 12 ranges from approximately
2-10 feet below ground surface, and is tidally influenced by Gambo Creek. Analytical results
from the surficial aquifer at Site 12 indicate that untreated groundwater is not suitable for
potable use, because of high total dissolved solids (TDS) and chloride (3,800 mg/1) levels.

The closest residences, on-base Navy housing consisting of over 150 homes, are within 6,000
feet southwest of Site 12.

2.2 SITE HISTORY AND ENFORCEMENT ACTIVITIES

2.2.1 History of Site Activities

Activity in the vicinity of Site 12 first began about 1952 when a 600 by 600 foot area was
cleared of vegetation. Prior to this, the Site 12 area was densely vegetated. Aerial

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photographs from 1967 show an access road leading to a rectangular fenced area containing two
separate pits. The pits were first observed somewhere between 1964 and 1967. The two pits in
the fenced area were observed as one consolidated pit in 1981 aerial photography. It was
reported that fuel (typically No. 2 fuel oil) had been used to burn laboratory materials and
metallic hardware and eguipment at the pit.

Quantities of decontaminated CWA solution, rendered safe in the laboratory by neutralization
with caustic soda ash, bleach, and alcohol-based caustic solutions, were also destroyed by
burning at Site 12. A total of approximately 300 gallons of liguid neutralized material was
disposed of in the pit over the life of operation. The last burn was conducted in September
1980. According to NSWCDL personnel, the last use of the pit was in October 1982, when
approximately 60 guarts of a sodium hypochlorite solution of unknown strength were disposed of
in the pit, but not burned.

In 1986 aerial photography, the pit and fence at Site 12 were no longer visible due to the
amount of vegetation present within the fenced area. By November 1986, the fence and gate were
removed and the burn pit was filled in by regrading the area. Known or potential wastes
disposed of at Site 12 include fuel oils, spent solvents, metals, caustics, hypochlonte,
polymers, glues, and decontaminated CWA solution.

2.2.2 Previous Investigations

The first investigation of the Chemical Burn Area (Site 12) was the Initial Assessment Study
(IAS) conducted in 1981 by Fred C. Hart Associates, Inc. The IAS included a records review,
personnel interviews, and a site visit. The IAS identified that small metered guantities (about
1 guart) of decontaminated CWA had been burned at the site (Fred C. Hart & Associates, 1983).
The IAS recommended that a Confirmation Study be conducted at Site 12 to ascertain the potential
for impacts on the surrounding environment.

The Confirmation Study at Site 12 was conducted in 1983 and 1984. Samples of Site 12 soil and
groundwater, surface water from Gambo Creek, and standing water in the burn pit were analyzed
for chloride, iron, manganese, phenol, sodium, sulfate, total organic carbon (TOG), and total
organic halides (TOX). In addition, one pit water sample and one subsurface soil sample were
scanned for the presence of base-neutral or acid-extractable organic compounds (BNAs) and
pesticides/polychlorinated biphenyls (PCBs). Four monitoring wells were installed in 1983
outside the former fenced area. Based on projected groundwater flow directions, the wells were
situated to provide data at three downgradient and one upgradient locations with respect to the
pit. Groundwater samples were reported in 1986 (O'Brien and Gere, February 1986).

Based on the results of the Confirmation Study, which demonstrated the potential for organic
contamination in the soils and groundwater, the site was scheduled for additional Remedial
Investigation (RI) sampling.

2.2.3 Enforcement Actions

There have been no enforcement actions taken at Site 12. The Navy has owned this property
since the early 1900's and is identified as the responsible party.

2.2.4 Highlights of Community Participation

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In accordance with Section 113 and 117 of CERCLA, the Navy held a public comment period from
July 16, 1997 through August 15, 1997 for the proposed remedial action described in the
Feasibility Study for Site 12 and in the Proposed Plan.

These documents were available to the public in the Administrative Record and information
repositories maintained at the Smoot Memorial Library, King George, Virginia: the Dahlgren
Laboratory General Library, Dahlgren, Virginia: and the Dahlgren Laboratory Public Record
Room, Dahlgren, Virginia. Public notice was provided in The Freelance Star newspaper on July
15, 1997 and a Public Meeting was held in the King George Administration Building on August 6,
1997. No written comments were received during the comment period and the comments and
responses provided during the Public Meeting are presented in Appendix B.

2.3 SCOPE AND ROLE OF RESPONSE ACTION SITE 12

Past waste burning operations at the site have contaminated subsurface soil and groundwater.
The Navy has decided to manage the remediation of the site as a single unit. The proposed
remedial actions identified in this ROD address contamination associated with Site 12, Chemical
Burn Area, as identified in the Draft Final RI Report, the Addendum RI Report, and the
Feasibility Study (FS) Report for Site 12. Several alternatives for response actions for
contaminated media are identified in Section 2.6. The rationale for selecting one of those
alternatives as the remedy for this site is described in Section 2.7.

The selected remedy uses air sparging/soil vapor extraction (AS/SVE) to remove 1,1,1-
trichloroethane (1,1,1-TCA) from the groundwater and subsurface soils and to remove 1,1-
dichloroethane (1,1-DCA) from groundwater to achieve remediation goals. Should the AS/SVE
technology not be capable of achieving remediation goals within a reasonable time frame, not to
exceed 30 years, the source of the contamination, subsurface soils, shall be excavated and
appropriately disposed of at an offsite disposal facility. The remedy will reduce the potential
risk to the environment associated with 1,1,1-TCA and 1,1-DCA migrating to Gambo Creek and
impacting ecological receptors. The selected remedy will involve pumping air into the
groundwater through air sparging wells and withdrawing the volatilized contaminants through soil
vapor extraction wells.

The off-gas from the system will be monitored to comply with applicable or relevant and
appropriate reguirements (ARARs).

This selected remedy is consistent with long-term remedial goals for Site 12. The remedial
action will help to reduce the volume of wastes in soil and groundwater, thereby reducing the
principal threat to ecological receptors in Gambo Creek from the migration of subsurface soil
and groundwater contaminants to sediments.

The remedy will not address surface water and sediment at Site 12. Remediation of these media
will be deferred to the Gambo Creek Ecological Study.

2.4 SUMMARY OF SITE CHARACTERISTICS

The RI at Site 12 was completed in phases. Geophysical investigations and radiological
investigations were initiated in 1993. Sampling activities, consisting of soil sampling,
surface water and sediment sampling, and the installation and sampling of groundwater monitoring
wells, were completed in 1994. Additional RI sampling, consisting of additional surface and
subsurface soil sampling and groundwater monitoring activities were completed in 1996. The
results of the RI are summarized below.

2.4.1 Sources of Contamination

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Geophysical and hydrogeologic investigations at Site 12 were conducted to identify disturbed
areas and burned metallic hardware and eguipment, and to investigate the extent of the burn pit.
The results of the survey indicated the presence of metallic objects and other geophysical
anomalies in the pit.  Based on groundwater and subsurface soil sampling results, the source of
groundwater contamination is the wastes present in the Chemical Burn Pit Figures 2-4 and 2-5
indicate the extent of the contamination in soils and groundwater above Preliminary Remediation
Goals (PRGs) respectively.




2.4.2   Description of Contamination

Soil, groundwater, surface water, and sediment samples were collected and analyzed for a variety
of parameters to determine the nature and extent of contamination at Site 12.  The major
contamination concerns at Site 12 are associated with the former burn pit.  Subsurface soil and
groundwater have been impacted by the waste disposal activities that occurred there.  The
results of the sampling and analyses are presented below.

Surface and Subsurface Soils

Elevated concentrations (130 mg/kg maximum) of chlorinated solvents 1,1,1-TCA and
degradation products  (i.e., 1,1-DCA and 1,1-dichloroethylene [1,1-DCE]) and benzene, toluene,
ethylbenzene, and xylene  (BTEX)  compounds were detected in the subsurface soils within the
former pit.  The detected concentrations of BTEX compounds (0.001 to 4.2 mg/kg) were relatively
low compared to chlorinated solvents.  The extent of 1,1,1-TCA, 1,1-DCA, 1,1-DCE, and BTEX
contamination within the vadose zone soils appears to be limited to soils in the vicinity of the
approximate center of the former pit Phthalates, polynuclear aromatic hydrocarbons  (PAHs), and
elevated levels of arsenic (13 mg/kg), copper  (611 mg/kg), lead (182 mg/kg), and zinc (419
mg/kg),  as compared to background levels, were also determined to be limited to the subsurface
soils in the vicinity of the pit at depths exceeding 3 feet below ground surface (bgs).

Surface soils exhibited much lower concentrations of volatile organic compounds  (VOCs) and
metals as compared to the pit.  PAHs  (15-160 ug/kg) and pesticides  (4.9-150 ug/kg)  were also
detected at low concentrations in surface soils.

Groundwater

Elevated concentrations (100,000 ug/L) of chlorinated solvents (1,1,1-TCA and degradation
products) and toluene were also detected in the brackish shallow aguifer.  Federal maximum
contaminant levels (MCLs)  for 1,1,1-TCA, 1,1-DCE, and toluene were exceeded in several
samples.  The highest concentrations of VOCS (100,000 ug/L) were present in the bottom of the
shallow aguifer (GW12-8D)  at the pit.  The concentrations of 1,1,1-TCA and related compounds
are lower  (3.800 ug/L) in the upper portion of the shallow aguifer  (GW12-8) and in downgradient
monitoring wells GW12-6 and GW12-9.  The extent of 1,1,1-TCA and degradation product
contamination in the shallow aguifer may extend to Gambo Creek.  The closest well to Gambo
Creek,  GW12-7, contains trace levels of 1,1,1-TCA  (4 ug/L).  Free product was not found during
either phase of the RI investigation; however,  the highest concentration of 1,1,1-TCA of 100,000
ug/L suggests that there is a high potential for Dense Non-Agueous Phase Liguid DNAPL) to be
present at Site 12.  Inorganics were also detected in Site 12 groundwater.  Concentrations of
aluminum (73,400 ug/L), cadmium  (2.3 ug/L), chromium (104 ug/L),  iron  (67,600 ug/L), lead (82.7
ug/L),  manganese  (1,040 ug/L), mercury  (0.21 ug/L), thallium (5.3 ug/L), and zinc (270 ug/L)
exceed MCLs or Virginia Groundwater Standards or, in the case of lead, exceeds the Federal

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Safe Drinking Water Act action level of 15 ug/L.

Surface Water and Sediment

1,1,1-TCA and degradation products were not detected in any of the surface water samples
collected from Site 12, but this failure to detect may have been due to volatilization and
dilution. Trace concentrations of 1,1,1-TCA and 1,2-DCE (total) were detected in Site 12
sediment samples from Gambo Creek. This trace contamination may be the result of overland flow
of contaminants from Site 12 soils or due to groundwater discharging to Gambo Creek. Although
Aroclor-1260 and mercury were freguently detected in sediment from Gambo Creek, there is no
strong evidence that Site 12 is the sole source. Aroclor-1260 was detected only in surface soil
in 3 of 17 samples at a maximum concentration of 150 ug/kg. The location of the sample
containing the highest concentration of PCB is over 400 feet east of Gambo Creek. Mercury was
detected in only one groundwater sample and 2 of 17 surface soil samples at concentrations lower
than those detected in sediment samples. This suggests that Arochlor-1260 and mercury detected
at Site 12 may not be the sole source of the sediment contamination detected in Gambo Creek.

2.4.3 Contaminant Migration

Minor levels of contamination were detected in the surface soils that surround Site 12. Release
and transport of contamination from Site 12 surface soils may occur by volatilization and
particulate emissions during soil excavation, soil erosion, and from leaching from the soil to
the groundwater. Leaching of contaminants from the surface soils and the subsurface soils
occurs predominantly in a vertical direction. Precipitation infiltrating through the bum pit
does leach contaminants from the wastes. VOCs have been detected at high levels in the
groundwater beneath Site 12.

There is evidence that natural processes are causing concentrations of VOCs to decrease at the
site. In the absence of naturally occurring processes, and given the groundwater velocity
(approximately 300 feet per year), the elapsed period of time since the last use of the Site 12
pit(approximately 10 years), and the distance to Gambo Creek (approximately 500 feet), the
concentrations downgradient of the source should be significantly higher than current
concentrations. However, contaminant concentrations at downgradient monitoring wells are
several orders of magnitude lower then concentrations at the source. Natural processes
including dispersion, diffusion, sorption, abiotic degradation, and biodegradation typically
affect the movement of contaminants within aquifers and may be responsible for the lower
downgradient concentrations at Site 12. Of these processes, sorption probably has the greatest
effect upon contaminant migration. Sortive processes near the source would cause the bulk of
contamination to remain relatively close to the source. Degradation of 1,1,1-TCA has apparently
led to the creation of daughter products such as 1,1-DCA and 1,11-DCE through anaerobic
processes. There is, as of yet, no evidence of vinyl chloride, a by-product of 1.1-DCE
degradation. This may be due to chemical oxidation and reduction conditions that are not
suitable for the native microorganisms to degrade 1,1-DCE further.

2.5 SUMMARY OF SITE RISKS

The human health and ecological risks associated with exposure to contaminated media at Site
12 were evaluated in the RI Report Addendum. The residential use scenario was not evaluated
because the current and anticipated future use of the site is industrial. Institutional
controls will be implemented to limit the site to future industrial use and exclude shallow
groundwater use. Due to its brackish quality and productivity constraints, groundwater in the
shallow aquifer is not a current source of drinking water and will not be used as one in the
future. Exposure to surface water is expected to be limited to fishermen in boats on Gambo
Creek.

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An ecological evaluation was also performed to evaluate potential threats to ecological
receptors. A summary of the human health and ecological risks associated with the site is
presented below.

Because many contaminants have the ability to migrate from one medium to another (e.g., soil to
groundwater), assessing risks from observed levels of contaminants is insufficient to evaluate
all the risks that may be presented at a site. Fate and transport modeling was therefore
completed to determine if levels of Contaminants of Concern might migrate to other media and
present unacceptable future risks to potential receptors. Preliminary Remediation Goals (PRGs)
were developed for COG's in all media to establish concentrations that would not produce
unacceptable risks.

2.5.1 Human Health Risks

Exposure Pathways and Potential Receptors

Access to the base is currently restricted by fences and security guards. Onsite workers visit
Site 12 infreguently. These workers may be exposed to minor surface soil contamination. Access
to Gambo Creek, is unrestricted: however, it is rarely used for recreational purposes.

Base workers, recreational users (adults and children on-site and on Gambo Creek adjacent to
Site 12), and construction workers were evaluated as potential receptors in the guantitative
risk assessment Base workers and recreational users were considered for both current and future
conditions. Construction workers were evaluated for future conditions only. Base workers,
recreational users, and construction workers were evaluated for incidental ingestion of soil and
dermal contact with soil. In addition, adult recreational fishermen were guantitatively
evaluated for fish ingestion. Construction workers were evaluated for exposure to
surface/subsurface soil (0 to 12 feet), while surface soil (0 to 2 feet) exposure was considered
for all other receptors. Potential exposure to groundwater by construction workers was not
evaluated because it was not considered to be a reasonable exposure scenario. Inhalation of
volatile emissions and fugitive dust was evaluated gualitatively via a comparison of site data
to U.S. Environmental Protection Agency (EPA) generic soil screening levels for transfers from
soil to air. Inhalation exposure was considered to be relatively insignificant for industrial
use.

Although maximum detections of 1,1-dichloroetheme and benzene in subsurface soil exceeded
Soil Screening Levels (SSLs), these chemicals are detected infreguently (i.e., in 3 out of 38
samples). Direct contact with surface water and sediment is not anticipated at the site because
inhospitable conditions associated with Gambo Creek make direct contact unlikely. Human health
risks are within acceptable ranges for industrial use at Site 12.

Exposure Assessment

Although various chemicals (i.e., VOCs, semivolatile organic compounds (SVOCs), and metals)
were detected in the environmental media for Site 12, the list of contaminants of concern (COCs)
for the site is limited under the industrial use scenario. Arsenic was the only COG identified
for soil (surface and subsurface); the only COG for fish tissue was 1,1,2,2,-tetrachloroethane.

Toxicity Assessment

Cancer potency factors (CPFs) have been developed by EPA's Carcinogenic Assessment Group
for estimating excess lifetime cancer risks associated with exposure to potentially carcinogenic
chemicals. CPFs, which are expressed units of (mg/kg-day) -1, are multiplied by the estimated

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intake of a potential carcinogen, in mg/kg/day, to provide an upper-bound estimate of the excess
lifetime cancer risk associated with exposure at that intake level. The term "upper bound"
reflects the conservative estimate of the risks calculated from the CPFs. Use of this approach
makes underestimation of the actual cancer risk highly unlikely. Cancer potency factors are
derived from the results of human epidemiological studies or chromic animal bioassays to which
animal-to-human extrapolation and uncertainty factors have been applied.

Reference doses (RfDs) have been developed by EPA for indicating the potential for adverse
health effects from exposure to chemicals exhibiting noncarcinogenic effect. RfDs, which are
expressed in units mg/kg-day, are estimates of lifetime daily exposure levels for humans,
including sensitive individuals. Estimated intakes of chemicals from environmental media (e.g.,
the amount of a chemical ingested from contaminated drinking water) can be compared to the
RfD. RfDs are derived from human epidemiological studies or animal studies to which uncertainty
factors have been applied (e.g., to account for the use of animal data to predict effects on
humans). These uncertainty factors help ensure that the RfDs will not underestimate the
potential for adverse noncarcinogenic effects to occur.

Risk Characterization

Excess lifetime cancer risks are determined by multiplying the intake level with the cancer
potency factor. These risks are probabilities that are generally expressed in scientific
notation (e.g., 1 x 10 -6). An excess lifetime cancer risk of 1 x 10 -6 indicates that, as a
plausible upper bound, an individual has a one in one million chance of developing cancer as a
result of site-related exposure to a carcinogen over a 70-year lifetime under the specific
exposure conditions at a site.

Potential concern for noncarcinogenic effects of a single contaminant in a single medium is
expressed as the hazard guotient (HQ) (or the ratio of the estimated intake derived from the
contaminant concentration in a given medium to the contaminants reference dose). By adding
the HQs for all contaminants within a medium or across all media to which a given population may
reasonably be exposed, the Hazard Index (HI) can be generated. The HI provides a useful
reference point for gauging the potential significance of multiple contaminant exposures within
a single medium or across media.

Current Base Worker. The cumulative hazard indices for ingestion of and dermal contact with
soils for Site 12, under industrial land use conditions are less than 1, which indicates that
there are no significant hazards associated with soils at Site 12. The cumulative ingestion and
dermal contact incremental cancer risk is 5.6 x 10 -7, under a "reasonable maximum exposure"
scenario, well below EPA's target risk range of 1 x 10 -6 to 1 x 10 -4.

Adult Recreational User. The cumulative noncancer hazard index (HI) from exposure via
ingestion of and dermal contact with Site 12 soils, under industrial land use conditions are
less than 1, as is the risk associated with the potential ingestion of fin fish. The cumulation
ingestion and dermal contact cancer risk is 7.4 x 10 -7 under a reasonable maximum exposure
scenario, well below EPA's target risk range of 1 x 10 -6 to 1 x 10 -6.

Child Recreational User. The cumulative hazard index and incremental cancer risk associated
with ingestion and dermal contact exposure to surface and subsurface soil at Site 12 under
industrial land use scenario are 2.2 x 10 -2 and 1.3 x 10 -4 respectively under a reasonable
maximum exposure scenario.

Construction Worker. The cumulative hazard index and incremental cancer risk associated with
ingestion and dermal contact exposure to Site 12 soil under industrial land use conditions are
5.2 x 10 -2 and 4.0 x 10 -7 respectively under a reasonable maximum exposure scenario.

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The incremental lifetime cancer risks for all receptors were less than than 1 x 10 -6 except for
the reasonable maximum exposure (RME) child. The cancer risk for the RME child (1.3 x 10 -6)
slightly exceeded 1 x 10 -6, but was within the EPA's target risk range, 1 x 10 -4 to 1 x 10 -6.

Estimated Hazard Indices (His) for all receptors under industrial land use conditions, were at
least two orders of magnitude below unity (1.0), which indicates that there are no significant
hazards associated with soils at Site 12. Therefore, exposure to noncarcinogens in site media
is not expected to cause adverse health impacts for human receptors. Human health baseline
risks are not greater than the risk range, however action is being taken at Site 12 to protect
potential environmental receptors..

There are several aspects of uncertainty associated with the risk assessment conducted at Site
12. Each is briefly discussed in this section. The major issues of uncertainty specific to
Site 12 are as follows:

While the USEPA recognizes lead as a B2 carcinogen, no cancer slope factor has been assigned
to this chemical. Currently, risks associated with lead are estimated in terms of predicted
blood lead levels in small children (ages 7 and under) by using the Integrated Exposure Uptake
Biokinetic Model. Typically, lead does not become a significant risk factor unless the
concentrations exceed 400 mg/kg in residential soil (USEPA, 1994b) and 15 ug/L in drinking
water. Lead is not considered to be a COG for soil at the site since the maximum detected
concentrations of lead are less than 400 mg/kg. Although the maximum site detection of lead in
groundwater exceeds 15 ug/L, groundwater is not expected to be used as a potable water supply
because of brackish conditions and productivity constraints. No USEPA Region III COG
screening level is available for exposure to lead in fish. However, the maximum surface water
concentration for this chemical (1.3 Ig/L) was well below the 50 ug/L Federal Ambient Water
Quality Criteria (AWQC) for the protection of human health (consumption of water and
organisms). Future impacts of groundwater contamination on surface water are not expected to
result in exceedances of Federal AWQC. Although lead was detected in a few historical
groundwater samples at concentrations exceeding the Federal AWQC, dilution in the water body
would reduce groundwater impacts. Therefore, the potential risks associated with exposure to
this chemical are considered to be minimal.

Because of the lack of toxicity criteria. USEPA Region III COG screening levels could not be
calculated for a few chemicals detected in the soil and surface water at the site
(benzo(g,h,i)perylene, calcium, magnesium, sodium, and potassium). This may lead to a slight
underestimation of potential risks. However, the underestimation is expected to be minimal
since overall exposure to PAHs is adeguately addressed by the evaluation of other PAHs, and the
remaining inorganics are essential nutrients, commonly detected in environmental media.

Because of the relatively small data set, the maximum surface water concentration was used to
assess potential RME risks for recreational users via fish ingestion. Consequently, the human
health risks associated with this exposure route may be overestimated since it is highly
unlikely that the true exposure concentration for surface water, to which a receptor is exposed
over the entire exposure period, is egual to the maximum detection.

In order to be conservative, analytical results for unfiltered surface water samples were used
to estimate potential human health risks for fish ingestion. It is believed that data for
filtered samples more closely approximates the bioavailable fraction of inorganic in surface
water than the unfiltered data. Therefore, estimates of fish uptake based on unfiltered sample
data for inorganics may result in overestimates of fish tissue concentrations and the associated
human health risks associated with fish consumption.

-------
The calculated risks for the fish ingestion pathway are based on estimates of uptake from
surface water and do not account for the uptake of contaminants from sediment. Thus, the risks
for the fish ingestion pathway may be underestimated. Chemicals present in sediments, as
opposed to surface water, may be of greater concern for bioaccumulation in fish. A presentation
of the sediment results for Site 12 is provided in the Draft Final RI Report, Volume 1, Section
9.4.4 (B&R Environmental, 1995).

2.5.2 Environmental Evaluation

The intent of the baseline ecological risk assessment (ERA) was to characterize potential
receptors and to estimate the potential hazard or risk to environmental receptors. Contaminant
pathways were identified to evaluate receptors potentially at risk. The ERA followed EPA
guidance for performing ecological risk assessments and was approved by Region III, EPA's
Biological Technical Assistance Group (BTAG). The baseline ERA is described fully in the RI
Report, and is briefly summarized here.

Analytical data compiled from the RI were analyzed using EPA Region III guidance for screening-
level risk assessments and to determine environmental effects guotients (EEQs). Data was
reviewed for surface water, sediment, and soil. Ecological receptors were assumed to be
exposed to surface soil at Site 12 as well as to surface water and sediments sampled from
adjacent portions of Gambo Creek to the southwest and an unnamed tributary of Gambo Creek
located east of the site. EEQs were determined by comparison with standard guidelines such as
EPA Region III, BTAG guidelines and Virginia water guality standards. These guidelines were
used to evaluate risks from exposure to surface waters and sediment. Similar guidelines.
protective of terrestrial wildlife, were used to evaluate surface soil contamination.
Preliminary COCs (PCOCs) were selected for each exposure media by comparing maximum site
concentrations to screening values, which typically are conservative. COCs were selected from
PCOCs by comparing maximum site concentrations to preliminary remediation goals (PRGs).
Those chemicals exceeding PRGs and potentially posing an actual risk to receptor populations
living on or near Site 12 were selected as COCs (Table 2-1). Decisions regarding whether or not
to remediate a contaminant were made by comparing maximum site concentrations to
background levels, and by considering the freguency of detection, the likelihood that a source
exists on the site, and bioavailability. The risk management process involved the use of
information from the ecological risk assessment, and Table 2-1 presents the results of that
assessment.

EEQs for contaminants found in surface water and sediments are presented in the FS. The
concentration of surface soil contaminants at Site 12 do not pose an ecological risk and do not
warrant remediation.

Copper in surface water and mercury in sediments remain a concern for ecological risk, but since
they do not appear to be solely related to Site 12, they will be considered in the Gambo Creek
Ecological Assessment, along with the other metals and pesticides in sediment, and PCBs in fish
tissue.

2.5.3 Development of Preliminary Remediation Goals (PRGs)

Contaminant fate and transport modeling is used to evaluate the potential for COCs identified by
the human health and ecological risk assessment to migrate to other media and present
unacceptable risks. For example, contaminants present in soils could migrate to groundwater or
be carried with precipitation to surface water or sediments at a site.

In order to evaluate this potential, fate and transport modeling was conducted for Site 12 using
the ECTran model. The model uses contaminant properties such as solubility, and site-specific

-------
characteristics such as depth to groundwater, to predict acceptable levels of COCs in soil and
groundwater that would be protective of surface water and sediment.  Regulatory criteria for
surface water and sediment were used in the modeling to develop PRGs for soil and groundwater.
A complete discussion of the use of modeling and assumptions is presented in the Site 12 FS.

Potential migration of COCs evaluated for Site 12 by the ECTran model included:

            6  Surface soil to surface water via runoff
            6  Surface soil to sediment via runoff
            6  Surface soil to surface water via groundwater
            6  Subsurface soil to surface water via groundwater
            6  Subsurface soil to sediment via groundwater
            6  Groundwater to surface water
            6  Groundwater to sediment

PRGs were developed by modeling for the following COCS:



    Inorganics
           6  Aluminum
           6  Arsenic
           6  Barium
           6  Chromium
           6  Copper
           6  Iron
           6  Lead
           6  Manganese
           6  Mercury
           6  Silver
           6  Thallium
           6  Zinc

    Volatile Organic compounds
           6  1,1-DCA
           6  1,1,1-TCA
           6  Toluene

    Pesticides and Other Organics

           6  4.4-DDD
           6  4,4-DDE
           6  4,4-DDT
           6  Endrin Aldehyde

This list includes COCs identified by the human health risk assessment and most of the metals
identified as COCs in the ecological risk assessment

The COCs that were not modeled were not attributable to Site 12 as a current source,  or had
borderline toxicity potential, or were common laboratory contaminants, or had concentrations not
different from background levels.  It was determined by modeling that 1,1,1-TCA was present in
subsurface soils at levels slightly above the PRG for the protection of sediment via the
leachate to groundwater to sediment exposure scenario.  VOCs 1.1-DCA and 1.1.1-TCA were
identified at levels in groundwater exceeding PRG's for the protection of sediment at the site

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boundary.

Concentrations of the contaminants of concern in each medium of exposure are found in Tables
2-2, 2-3, and 2-4.

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                                     TABLE 2-2
                   SUMMARY OF SURFACE SOIL PRGs -  (mg/kg) - SITE 12
                             NSWCDL, DAHLGREN, VIRGINIA
                        Soil Sampling
                           Results
Preliminary Remediation Goals
                      Range of Detected   Protection of   Protection of
Chemical of Concern Values
Organics
4, 4 -DDT
4, 4 -ODD
4, 4 -DDE
Endrin Aldehyde
1, 1-Dichloroethane

0.0049
0.014
0
0.0071
0.003
1, 1, 1-Trichloroethane 0.001
Toluene
Inorganics (total
Aluminum
Arsenic
Barium
Chromium
Copper
Iron
Lead
Manganese
Mercury
Silver
Thallium
Zinc
0.002
metals)
3,890
2.1
27.9
5.5
4.1
5,460
7.9
17
0.04
0.52

15.8

- 0.018
- 0.031
.037
- 0.0097
- 0.028
- 0.220
- 0.032

- 17,400
- 5.2
- 65.5
- 28.1
- 12.9
- 21,800
- 92.4
- 116
- 0.36
- 3.6
1.1
- 44.7
Sediment

10.7
2.00
9.76
0.042
0.0818
0.378
1.77

20,000 (1)
77.4
300 (1)
409
298
32,100
241
475
0.785
4.09
NA
453
Surface Wate

12.4
4.73
21.1
NA
832
939
5,700

309,000
5.320
29.300
809
587
521,000
5,430
19,800
2.43
51.1
809
15,600
NA  Not Applicable.

1   The PRG is based on the upper range of the background concentration for the NSWCDL site
    or for the Maryland Coastal Plain  (B&R Environmental, 1995), whichever is higher.  All soil
    containing concentrations above this value will be considered site related and will be
    considered for remediation.  All soils with concentrations below this value will be
    considered naturally occurring.

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                                    TABLE 2-3

                 SUMMARY OF SUBSURFACE SOIL PRGs -  (mg/kg) - SITE 12
                             NSWCDL DAHLGREN, VIRGINIA
                        Soil Sampling Results
                      Range of Detected
                           Values
Chemical of Concern
 Organics
4,4-DDE
Benzene
1,1-Dichloroethane
1,1-Dichloroethene
1,1,1-Trichloroethane
Endrin Aldehyde
Toluene
 Inorganics (total me Is)
Aluminum                1,530 - 14.900
Arsenic                   1.3 - 13.4
Barium                     5.5 - 141
Cadmium                     32.1
Chromium                   3.1 - 58.3
Copper                    1.9 - 611
Iron                     1,540-33,200
                            0.017
                        0.014 - 2
                        0.003 - 10
                        0.004 - 0.78
                        0.003 - 130
                         0.011 - 0.028
                        0.001 - 1.1
Lead
Manganese
Silver
Zinc
                          1.9 - 182
                          2.9 - 64
                          1.6 - 15.5
                          3.4 - 419
Preliminary Remediation Goals
Protection of   Protection of
Surface Water     Sediment
0 x 10 6
292
1,300
2,060
1,180
NA
.0 x
.0 x
664,
.0 x
550,
88
78,
.0 x
.0 x
.0 x
10
10
000
10
000
,100
400
10
10
10
6
6

6



6
6
6
NA
.0 x
10
6
>1 . 0 x
12.
63.
859
39.
10
2
0
5
6
NA
>1 . 0 x
>1 . 0 x
25,
10
10
600
6
6

7,270
3,
136
99,
>1 . 0 x
347,
157,
1,
149,
490
,000
600
10
000
000
350
000



6




  Shaded   COG which exceeds PRGs.
  NA       Not applicable.

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                                              TABLE 2-4

                           SUMMARY OF GROUNDWATER PRGs - (Ig/L)
                                 NSWCDL DAHLGREN, VIRGINIA
            Chemical of Concern
     Organics
    Endrin Aldehyde
    RDX
    1,1,2,2-Tetrachloroethane
    1,1-Dichloroethane
    1,1-Dichloroethene
    1,1,1-Trichloroethane
    Toluene
     Inorganics (total and dissolved
     metals)
    Aluminum
    Arsenic
    Barium
    Cadmium
    Chromium
    Copper
    Iron
    Lead
    Manganese
    Mercury
    Selenium
    Thallium
    Zinc
  Range  of  Detected
        Values
(All  Sampling Results)
         0.19
        .2  - 4.7
           2
         -  11,000
         -  6,200
        - 100,000
           1,700
 2 -
    22.6
    1.75
       9
     0.8
       4
       3
      29
     1.3
     4.7
     73,400
     19.6
     438
     2.3
     104
     93.45
     67,600
     82.7
     1,040
  0.21
  4.2
  5.3
13 - 270
                   Preliminary Remediation Goals

                   Protection of   Protection of
                   Surface Water     Sediment
                        NA
                        NA
                        NA
                      201,000
                     1,830,000
                      208,000
                    XL.O x 10 9
XL.O x 10 9
 3,140,000
19,500,000
 1,250,000
  542,000
  250,000
839,000,000
 10,100,000
 16,800,000
   2,150
  90,000
  901,000
 16,300,000
                   1.83
                    NA
                    NA
                   9,650
                  75,600
                   5,320
                354,000,000
XL.O x 10 9
  122,000
   26,600
    7,800
  832,000
  320,000
 8,410,000
   60,700
  494,000
    788
   11,500
    NA
  339,000
     Shaded   COG which exceeds PRGs.
     NA       Not applicable.

Exposure Pathways

The exposure pathways consist of dermal absorption and ingestion of chemicals from soil,
sediments, and surface water.

Exposure Assessment

Six constituents in sediment, five constituents in surface water, and seven inorganics in
surface soils were identified as COCs for ecological receptors (Table 2-1).   The EEQ for each of
these contaminants was determined to be greater than 1.  The EEQ for each of the other
contaminants was determined to be less than one.
Potential Receptors

The organisms most likely to be receptors include mice, voles, rabbits, earthworms, other
ground insects, fish, and a variety of birds.  Because of the open nature of Site 12 and the
variety of nearby habitats, Site 12 is likely to have a great diversity of wildlife.

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Risk Characterization

Several inorganics in the sediment at Site 12 may represent a potential risk to ecological
resources  (Table 2-1).   However, sediment remediation was deferred to the Gambo Creek
Ecological Study.  Surface water and sediment monitoring will be part of the selected remedy to
ensure that excessive risks do not exist and that the source control remedy is effective.
Modeling was also performed to determine potential risks associated with contaminant migration
from surface soils, subsurface soils, and groundwater to exposure points in Gambo Creek.  It
was determined that 1,1,1-TCA and 1,1-DCA in subsurface soils and groundwater pose a
potential risk to ecological receptors in sediment (Tables 2-3, 2-4).  Table 2-2 indicates that
surface soils do not pose a risk to surface water and sediment at Site 12.

2.6     DESCRIPTION OF ALTERNATIVES

Based on an evaluation of site conditions, potential risks, and legal reguirements for Site 12,
three remediation goals were identified to protect the public from potential future health
risks, as well as to protect the environment:

              6 Compliance at Site 12 with contaminant-specific, location-specific, and
                action-specific Federal and Commonwealth of Virginia ARAR, and to be
                considereds (TBC).

              6 Remove 1,1,1-TCA until concentrations are no more than 39.5 mg/kg in
                subsurface soils in the source area,  thereby preventing 1,1,1-TCA from
                migrating to sediments via groundwater and causing adverse effects in
                ecological receptors.

              6 Remove 1,1-DCA and 1,1,1-TCA until concentrations are no more than 9,650
                ug/L and 5,320 ug/L, respectively, in groundwater in the former burn pit area,
                and thereby prevent them from migrating to sediments and causing adverse
                effects in ecological receptors.

A detailed analysis of the possible remedial alternatives for Site 12 is included in the Site 12
Feasibility Study report.  The detailed analysis was conducted in accordance with the EPA
document entitled Guidance for Conducting Remedial Investigations and Feasibility Studies under
CERCLA and the National Oil Hazardous Substances Pollution Contingency Plan (NCP).

The following institutional controls are part of every alternative except the No Action
alternative, and shall be undertaken within 90 days of completion of remedial construction:  a
real property description notation, Base Master Plan notations, and limited site access.  Signs
shall be posted which state that hazardous substances are present.  Signs shall be removed at
the completion of the remedy.   The Base Master Plan shall note the area as one in which
residential development can not occur, shallow groundwater can not be used, and site access
shall be limited.  A notation shall be filed in the real property file maintained at EFA Ches
for this site indicating the extent of the area and the fact that solid wastes are present.  The
institutional controls shall also include the following:  Within 90 days after completion of the
remedy, the Navy shall produce a survey plat prepared by a professional land surveyor registered
by the Commonwealth of Virginia indicating the location and dimensions of disposal area and the
extent of groundwater contamination. Monitoring well locations shall be included and identified
on the survey plat.  The plat shall contain a note, prominently displayed, which states the
owner's future obligation to restrict disturbance  (excavation or construction) of the property;
post-closure use of the property shall prohibit residential use, access or use of groundwater
underlying the property for any purpose except monitoring, and shall not disturb the function of
the monitoring systems.  The owner of the property shall submit the survey plat to the local

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recording authority when closure is complete. If and when the property is transferred out of
the Federal government the deed (or some other instrument which is normally examined during
title search at the local land recording authority) shall contain the survey plat, a notation
notifying any potential purchaser of the property that the land has been used to manage solid
waste, and an appropriate deed restriction.

A summary of the remedial alternatives which were developed to address contamination
associated with Site 12 is presented below.

Alternative 1 - No Action

The No Action alternative is reguired under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA). Under this alternative, no actions would be taken to
reduce the toxicity, mobility, or volume of the contaminated soil or groundwater at Site 12.
Alternative 1 serves as a baseline against which the effectiveness of other alternatives is
measured.

Alternative 2 - Long-Term Monitoring (Groundwater); Long-Term Monitoring or Excavate
Source, Offsite Disposal (Subsurface Soils); Institutional Controls (Groundwater and Soils)

Description:

Under this alternative, institutional controls as outlined above, shall be implemented to
eliminate or reduce pathways of exposure to 1,1,1-TCA in subsurface soils, and 1,1,1-TCA and
1,1-DCA in groundwater.

Groundwater contaminants (1,1,1-TCA and 1,1-DCA) in the shallow aguifer shall not be treated,
but allowed to degrade over time through natural biodegradation and chemical decomposition
processes. Due to its brackish guality and productivity constraints, groundwater at Site 12 in
the shallow aguifer is not a current source of drinking water and shall not be used as one in
the future. Institutional controls shall be implemented to prevent the use of groundwater at the
site for drinking water purposes.

Groundwater, surface water, and sediment shall be monitored to ensure that dispersion/dilution,
abiotic degradation and intrinsic bioremediation of 1,1,1-TCA and 1,1-DCA are occurring.
Quarterly sampling for VOCs, SVOCs, biodegradation parameters, and metals shall be
performed. A site review including long-term monitoring costs shall be conducted every 5 years
for 30 years to evaluate the site status and provide direction for further action, if necessary.

It is noted that concentrations of metals in groundwater (chromium, copper, iron, and lead) are
significantly elevated above background levels. SVOCs were also detected above background
levels in some instances. Despite the fact that modeling has not indicated a potential threat
to ecological receptors from metals and SVOCs in surface water or sediments, monitoring shall be
conducted to measure concentrations of these constituents in groundwater, surface water, and
sediments. Long-term monitoring or the excavation and offsite disposal of subsurface soils in
the source area may be considered. The effectiveness of natural processes shall be evaluated
during the 5 year review period provided under CERCLA. Soil removal would eliminate VOCs, and
DNAPL that would eventually migrate to groundwater and speed up the natural processes.
Subsurface soils in the vicinity of the former burn pit shall be excavated if PRGs (Tables 2-2,
2-3, and 2-4) are not achieved within a reasonable time, not to exceed 30 years, and shall be
transported to an appropriate facility for disposal. Under this alternative, it is assumed that
soils will be characterized as nonhazardous waste. However, if land disposal restrictions
(LDRs) are exceeded, the soils would be considered a characteristic hazardous waste under the
Resource Conservation and Recovery Act (RCRA). The additional costs that would be incurred to

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incinerate the soils at an approved offsite facility are described in Alternative 3B.  The area
of the source is estimated to be 2,500 square feet, extending to a depth of approximately 8
feet.  The total volume to be removed is estimated to be 740 cubic yards, and the area shall be
backfilled with clean soil.

During excavation, the potential for erosion shall be minimized by following erosion and
sediment control best management practices.  Habitat alteration shall be minimal.

    The costs for this alternative are:

    Estimated Capital Cost:           $0 for long-term monitoring;
                                      $520,000 for offsite nonhazardous waste landfilling
    Estimated Annual O&M Cost:        $43,500
    Estimated 30-year Present Worth:  $1,178,000 for long-term monitoring;
                                      $1,698,000 for offsite nonhazardous waste landfilling
    Time to Implement                 Less than one year
Alternative 3A - Pump, Treat, Discharge to Gambo Creek (Groundwater); Long-Term
Monitoring  (Subsurface Soils); Institutional Controls (Groundwater and Soils)

Description:

This alternative consists of three major components:  (1) groundwater extraction, (2) onsite
groundwater treatment/discharge to Gambo Creek, and  (3)  institutional controls.

A groundwater extraction and treatment system would be installed to capture VOC contaminants
by restricting migration of the groundwater in the shallow aquifer.  Contaminated groundwater
migrating within the shallow aquifer and from Site 12 would be captured prior to its discharge
into Gambo, Creek.  Due to its brackish quality and productivity constraints, groundwater in the
shallow aquifer is not a current source of drinking water and will not be used as one in the
future.

For costing purposes, the groundwater extraction system would consist of six wells,  pumping at
an aggregate rate of 40 gallons per minute  (gpm),  located at the source and within the
downgradient boundaries of the plume.  Extracted groundwater would be pumped to a newly
constructed, centrally located treatment system.   For costing purposes, the treatment system
would consist of the following processes:  equalization,  iron oxidation and pH adjustment,
clarification, sand filtration, air stripping and sludge handling.  Treated groundwater would
then be discharged to Gambo Creek from the treatment plant

While there would be no air emissions controls on the air stripper and initially up to 25 pounds
per day of VOCs removed from the groundwater would be expected to be vented to the atmosphere,
emissions at these levels would be expected to be short term during the installation and pilot
testing of the system.  Long-term operation of the system would be controlled to address the
EPA's Office of Solid Waste and Emergency Response  (OSWER) Directive 9355.0-28 limit of
15 pounds per day VOCs for air emissions from Superfund remedial actions.  Based on the fact
that the closest potential receptors are over 2,000 feet from Site 12, it is not likely that
excess human health risks would be experienced.  In addition, prior to implementation, a risk
assessment would be conducted to demonstrate that no excess human health risks would result from
the emissions.

Contaminated subsurface soils would be addressed through natural processes such as leaching
to groundwater, volatilization, and degradation.

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Institutional controls, as outlined above, shall be implemented to eliminate or reduce pathways
of exposure to contaminants at the site.

In addition, groundwater, sediment, and surface water monitoring shall be conducted. It is
noted that concentrations of metals in groundwater (chromium, copper, iron, and lead) are
significantly elevated above background levels. SVOCs were also detected above background
levels in some instances. Despite the fact that modeling has not indicated a potential threat
to ecological receptors in surface water or sediments, monitoring shall be implemented to
measure concentrations of these constituents.

This remediation alternative would operate for 12 years. Annual O&M Costs include monitoring
costs, which would occur every 5 years for 20 years. Monitoring for 20 years is considered a
sufficient period of time to monitor site conditions in view of the length of time reguired to
complete the remediation of the site under this alternative.

The costs for this altenative are:

Estimated Capital Cost: $2,212,000
Estimated Annual O&M Cost: $140,000
Estimated 30-year Present Worth: $4,328,000
Time to Implement: Less than one year

Alternative 3B - Pump, Treat, Discharge to Gambo Creek (Groundwater); Excavate Source,
Offsite Disposal or Offsite Incineration and Disposal (Subsurface Soils); Institutional
Controls (Groundwater and Soils)

Description:

This alternative has four major components: (1) groundwater extraction, (2) onsite groundwater
treatment/discharge to Gambo Creek, (3) excavation of source area with offsite disposal, and (4)
institutional controls. The groundwater treatment component would be the same as Alternative
3A.

Contaminated subsurface soil at the source area exceeding remediation goals would be
excavated, based on COG levels, and transported offsite for disposal at a suitable facility.
The soil might reguire treatment to achieve LDRs prior to landfilling if determined to be a RCRA
characteristic waste. The area of the source is estimated to be 2,500 sguare feet, extending to
a depth of approximately 8 feet. The total volume of soil to be removed is estimated to be 740
cubic yards. The excavated area would be backfilled with clean soils. Because soils to be
excavated have not been characterized for disposal purposes, costs that have been developed
include disposal as nonhazardous waste and as hazardous waste (incineration).

During excavation, the potential for erosion will be minimized by following erosion and sediment
control best management practices. Habitat alteration will be minimal.

The institutional controls, as outlined above, shall be implemented. In addition, groundwater,
sediment, and surface water monitoring shall be conducted. It is noted that concentrations of
metals in groundwater (chromium, copper, iron, and lead) are significantly elevated above
background levels. SVOCs were also detected above background levels in some instances.
Despite the fact that modeling has not indicated a potential threat to ecological receptors in
surface water or sediments, monitoring shall be implemented to measure concentrations of these
constituents.

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This remediation alternative would operate for 12 years. Annual O&M costs include monitoring
costs, which would occur every 5 years for 20 years. Monitoring for 20 years is considered a
sufficient period of time to monitor site conditions in view of the length of time reguired to
complete the remediation of the site under this alternative.

The costs for this alternative are:

Estimated Capital Cost: $2,732,000 for offsite nonhazardous waste landfilling;
$3,420,000 for offsite incineration (including groundwater
remediation for both options).
Estimated Annual O&M Cost: $140,000/yr
Estimated 30-year Present Worth: $4,848,000 for offsite nonhazardous waste landfilling;
$5,536,000 for offsite incineration (including groundwater
remediation for both options).

Time to Implement: One to two years
Alternative 3C - Pump, Treat, Discharge to Gambo Creek (Groundwater); Excavate Source,
Onsite Thermal Treatment/Backfill (Subsurface Soils); Institutional Controls (Groundwater
and Soils)

Description:

This alternative consists of four major components: (1) groundwater extraction, (2) onsite
groundwater treatment/discharge to Gambo Creek, (3) excavation of source area soils with onsite
thermal treatment and (4) institutional controls. The groundwater treatment component would be
the same as in Alternative 3A.

Contaminated subsurface soil in the vicinity of the former burn pit exceeding remediation goals
would be excavated, based on COG levels. Following excavation, the soils would be treated
onsite. The soils would be screened prior to treatment using size separation and
crushing/grinding technigues, then treated using low-temperature thermal desorption. The
throughput is expected to be an estimated 18 tons per day. The area of the source is estimated
to be 2,500 sguare feet extending to a depth of approximately 8 feet. The total volume of soil
to be removed is estimated to be 740 cubic yards. The treated excavated soils would then be
used as backfill.

During excavation, the potential for erosion will be minimized by following erosion and sediment
control best management practices. Habitat alteration will be minimal.

The institutional controls, as outlined above, shall be implemented. In addition, groundwater,
sediment and surface water monitoring shall be conducted. It is noted that concentrations of
metals in groundwater (chromium, copper, iron, and lead) are significantly elevated above
background levels. SVOCs were also detected above background levels in some instances.
Despite the fact that modeling has not indicated a potential threat to ecological receptors in
surface water or sediments, monitoring shall be implemented to measure concentrations of these
constituents.

This remediation alternative would operate for 12 years. Annual O&M costs include monitoring
costs, which would occur every 5 years for 20 years. Monitoring for 20 years is considered a
sufficient period of time to monitor site conditions in view of the length of time reguired to
complete the remediation of the site under this alternative.

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The costs for this alternative are:

Estimated Capital Cost: $2,212.000
Estimated Annual O&M Cost: $140,000/yr
Estimated 30-year Present Worth: $4,328,000
Time to Implement: One to two years

Alternative 4 - Air Sparging/Soil Vapor Extraction (Groundwater and Soils); Institutional
Controls (Groundwater and Soils)

Description:

This alternative involves air sparging/soil vapor extraction (AS/SVE) and institutional
controls.

An AS/SVE system shall be installed in the source area (see Figure 2-4 and Figure 2-5) to
address the potential presence of DNAPL and to volatilize VOCs in the subsurface soils and
groundwater in the shallow aquifer. Due to its brackish quality and productivity constraints,
groundwater in the shallow aquifer is not a current source of drinking water and will not be
used as one in the future.

The air sparging system shall consist of at least two air injection wells in the source area.

The vapor extraction system shall consist of at least two vapor extraction wells located in the
source area (see Figure 2-4 and Figure 2-5) and along the downgradient boundaries of the plume,
as defined by the groundwater monitoring well network. The air sparging wells shall be placed
approximately 30 feet apart, and the extraction wells shall be placed midway between the air
sparging wells. The system shall be designed to accommodate up to six additional AS wells and
seven additional SVE wells to address the potential need for future expansion of the system.
Extracted vapors shall be monitored to ensure compliance with EPA and Virginia ARARs and
TBCs and discharged to the atmosphere. While there will be no air emission controls on the
AS/SVE system, and initially up to 25 pounds per day of VOCs removed from the groundwater is
expected to be vented to the atmosphere, emissions at these levels are expected to be short-term
during the installation and pilot-testing of the system.

Long-term operation of the system shall, if needed, be controlled to meet the OSWER Directive
9355.0-28 limit of 15 pounds per day VOCs for air emissions from Superfund remedial actions.
Controls may include reducing air flow into the aquifer, the use of carbon adsorption, or other
means acceptable to EPA and VDEQ. Based on the fact that the closest potential receptors are
over 2,000 feet from Site 12, it is not likely that excess human health risks will be
experienced. In addition, prior to implementation, a risk assessment shall be conducted to
demonstrate that no excess human health risks would result from the emissions.

This remediation alternative shall operate for 12 years. Annual O&M costs include monitoring
costs, which shall occur every 5 years for 20 years.

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The costs for this alternative are:

    Estimated Capital Cost:              $293,000
    Estimated Annual O&M Cost:           $73,000/yr
    Estimated 30-year Present Worth:     $1,393,000
    Time to Implement:                   One to two years
2.7     SUMMARY OF THE COMPARATIVE ANALYSIS OF ALTERNATIVES

The remedial alternatives described in Section 2.6 were evaluated in the Feasibility Study
against nine criteria identified in the NCP, as presented below.

2.7.1   Threshold Criteria

Overall Protection of Human Health and the Environment

To be protective of ecological receptors in the environment the following Remedial Action
Objectives  (RAOs) have been developed for Site 12 soil and groundwater to address the
primary exposure pathways:

    6 Remove 1,1,1-TCA until concentrations are no more than 39.5 mg/kg in subsurface soils in
      the source area, thereby preventing 1,1,1-TCA from migrating to sediments via groundwater
      and causing adverse effects in ecological receptors.

    6 Remove 1,1-DCA and 1,1,1-TCA until concentrations are no more than 9,650 Ig/L and
      5,320 Ig/L, respectively, in groundwater in the former burn pit area, and thereby prevent
      them from migrating to sediments and causing adverse effects in ecological receptors.

Alternative 4 provides the highest level of overall protection of human health and the
environment because remediation goals would be achieved guicker and more efficiently than
the other alternatives.  Alternatives 3A, 3B, and 3C would be protective of the environment,
however the time frame for remediation is less certain than Alternative 4.

Institutional controls will limit the use of groundwater and any future residential use of the
site. Long-term monitoring of groundwater, surface water, and sediments will also ensure overall
protection of human health and the environment.  Alternative 2 would be protective of human
health and the environment but the remediation time would reguire an extended monitoring
period.  Alternative 1 would not be protective of the environment because no measures are
taken to achieve RAOs for the site.

Compliance with Applicable or Relevant and Appropriate Reguirements (ARARs)

Alternative 4 would comply with all ARARs and To Be Considered  (TBC)  and in addition shall
limit the types and amounts of wastes generated and treated materials to be handled, thereby
limiting potential exposures and reducing additional ARARs.  Alternatives, 3A, 3B, and 3C
would comply with TBCs and ARARs, however achieving the ARARs is less certain and shall
reguire more time.  Alternative 3A would not reguire compliance with any soil-disposal ARARs.
The offsite disposal options under Alternative 2 and 3B would reguire compliance with RCRA
land disposal reguirements.  Alternative 2 would comply with remediation goals for protection of
ecological receptors, however long-term monitoring will be reguired.   Alternative 1 will not
achieve remediation goals for protection of ecological receptors, nor meet all the ARARs and
TBC.

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2.7.2 Primary Balancing Criteria

Reduction of Toxicity, Mobility, and Volume

Alternatives 3A, 3B, 3C, and 4 would not achieve a significant reduction of toxicity, mobility,
or volume of contaminants through treatment because VOC's would be discharged to the
atmosphere. Alternative 4 does not increase the volume of wastes, while Alternatives 3A. 3B,
and 3C would increase the volume of wastes by an estimated 500 pounds per week (wet
weight) of dewatered sludge from groundwater treatment would be generated and need
disposal offsite. The offbase landfilling option under Alternatives 2 and 3B would relocate the
waste, the offsite RCRA incineration option under Alternative 3C would treat the soils by
desorbing VOCs for eventual recycling or destruction offsite. Alternatives 1 and 2 would not
achieve reduction in toxicity, mobility, or volume through active treatment of VOCs.

Long-term Effectiveness

Alternative 4 would remove VOCs from both soils and groundwater to achieve RAOs faster and
more efficiently than the other alternatives, and therefore would be the best alternative for
long-term effectiveness. In Alternative 4, the use of air sparging has the potential to be more
effective in removing VOC's and treating DNAPLs than simple pump and treat alternatives.
Alternatives 3A, 3B, and 3C would be effective in the long term because remediation goals for
the environment could be achieved, after some time. It should be noted that Alternatives 3A
and offbase landfilling options under 2 and 3B would be less effective than Alternative 4
because the source area would be either left in place in Alternative 3A or merely relocated to
an offsite location. However, under the RCRA incineration option under Alternatives 2 and 3B,
and for Alternative 3C, the source soils would be treated for removal of COCs. Alternative 3B
would be more effective than 3A because the removal of contaminated soils in 3B would reduce the
magnitude of residual risks to a greater degree than in 3A. Alternative 2 depends on natural
processes and monitoring to be effective in preventing the migration of COCS into the
environment. Attainment of remediation goals would be prolonged if DNAPL is present, and the
data indicate that DNAPL is, most likely, under the Chemical Burn Pit. Alternative 2 would
depend on the implementation of remedial actions (i.e., soil excavation and removal) as
appropriate if natural processes failed to meet remediation goals. Also, Alternative 2 would
depend on long-term implementation of institutional controls for its effectiveness. Alternative
1 would not be effective in the long term because RAOs would not be achieved and there would
not be a mechanism in place to ensure protection of the environment.

Short-term Effectiveness

Alternative 4 would have the best potential for short-term effectiveness, because the AS/SVE
system takes less time to reach remediation goals and is more efficient than the other
alternatives. Alternative 4, the contaminanted soils would be remediated in-situ, while
Alternatives 3A, 3B, and 3C would require excavation to treat the soils, therefore Alternative 4
would have relatively fewer concerns for exposure to contaminants. Remediation under
Alternatives 3A, 3B, and 3C would require longer periods of operation in order to achieve RAOs,
and would have additional concerns with respect to producing treatment residuals for disposal,
and the need to discharge large quantities of treated water. Alternative 3C would have
concerns associated with worker protection during treatment of soils onsite, although
appropriate personal protective equipment and site monitoring will reduce the risk.
Alternatives 3B and 2 would have additional concerns as associated with potential exposure
during the excavation and offsite transport of source soils. Transport vehicles would be
covered to reduce spillage and control dust. Although the source would be left in place in
Alternative 3A, the duration for attainment of remediation goals would be comparable to
Alternatives 3B and 3C, in which the contaminated soils would be removed and/or treated.

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Alternative 2 would not be effective in the short-term because natural processes require a long
period of time. However, monitoring would provide a mechanism to take further action to
mitigate adverse impacts to sediments. The excavation and disposal option under Alternative 2
would provide a measure of short-term effectiveness. Alternative 1 would not be effective in
the short term because RAOs would not be achieved and the potential for sediments to be
adversely impacted would remain.

Implementability

Alternative 3A, 3B, 3C, and 4 would have similar implementability concerns. Alternative 4
would not have the delays associated with administrative negotiations with the Commonwealth
of Virginia for discharges of treated groundwater to Gambo Creek, however, a pilot-scale
treatability study will delay full implementation. All equipment and services would be
available for AS/SVE implementation. Alternatives 3A, 3B, and 3C would all have common
implementability issues with the groundwater remediation system, such as the need to conduct
bench-scale treatability studies and, in addition, the need to negotiate with the Commonwealth
of Virginia for discharge standards to Gambo Creek. All equipment, services, and disposal
facilities would be available for groundwater remediation. Alternative 3A would have no
implementability concerns for soil remediation. Alternative 2 and 3B would involve excavation
and offsite transport of contaminated soils. For these alternatives, the soil might require
treatment to achieve LDRs prior to landfilling if determined to be a RCRA characteristic waste.
Alternative 3C would have the greatest implementability concerns with regard to the excavation
of source soils and onsite treatment. These concerns would include the need for trained
personnel onsite, access to utilities, and bench-scale treatability studies. Alternative 2
would have implementability concerns, such as excavation, transportation, and disposal issues,
associated with source removal. Alternative 1 requires no implementation.

Cost

Alternative 4 would be the most cost effective remedy for active remediation. The time to
completion for Alternative 4 would be much shorter than the other alternatives, thereby reducing
O&M costs. Alternative 4 would have relatively low capital costs, as compared to the pump and
treatment alternatives. Capital costs would be relatively high for Alternatives 3A, 3B, and 3C.
O&M costs would all be similar for Alternatives 3A, 3B, and 3C. Alternative 2 would have low
capital costs associated with the source removal option. Alternative 2 would have relatively
low O&M costs compared to the other alternatives. There would be no capital costs and no O&M
costs associated with Alternative 1.

The least to most expensive alternatives, based on estimated net present worth, are $0
(Alternative 1), $1,178,000 or $1,698,000 (Alternative 2), $1,393,000 (Alternative 4),
$4,328,000 (Alternative 3A), $4,328,000 (Alternative 3C), and $4,848,000 or $5,536,000,
depending on the disposal alternative chosen (Alternative 3B).

2.7.3 Modifying Criteria

State Acceptance

The Virginia Department of Environmental Quality, on behalf of the Commonwealth of Virginia,
has reviewed the information available for this site and has concurred with this ROD and the
selected remedy identified below.

Community Acceptance

Community Acceptance summarizes the public's general response to the alternatives described

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in the Proposed Plan and the Feasibility Study. No written comments were received during the
thirty-day comment period which began on July 16, and ended on August 15, 1997. There were
no comments or guestions received at the Proposed Plan Public Meeting held on August 6,
1997. The background on Community involvement is included in the Responsiveness
Summary, Section 3.0 of the ROD.

2.8 THE SELECTED REMEDY

The selected remedy for Site 12 is Alternative 4 which involves the installation of an AS/SVE
system to address the potential presence of DNAPL and to volatilize VOCs in the subsurface
soils and groundwater in the shallow aguifer and implementation of institutional controls to
limit the site to future industrial use and to exclude shallow groundwater use. Surface water
and groundwater shall continue to be monitored.

The major components of the selected remedy are:

The Navy shall monitor the extracted vapors to ensure compliance with EPA and Virginia
ARARs and TBCs as they are discharged to the atmosphere.

There will be no air emission controls on the AS/SVE system, and initially up to 25 pounds per
day of VOCs removed from groundwater is expected to be vented to the atmosphere.
Emissions at these levels are expected to be short-term during the installation and
pilot-testing of the system. Long-term operation of the system shall, if needed, be controlled
to meet the OSWER Directive 9355.0-28 limit of 15 pounds per day VOCs for air emissions from
Superfund remedial actions. Controls may include reducing air flow into the aguifer, use of
carbon adsorption, or other means acceptable to EPA and VDEQ.

The Navy shall institute the following institutional controls within 90 days of completion of
the installation of the AS/SVE system: a real property description notation, Base Master Plan
notations, and limited site access. Signs shall be posted which state that hazardous
substances are present. The signs shall be removed at the completion of the remedy. The
Base Master Plan shall note the area as one in which residential development can not occur,
shallow groundwater can not be used, and site access shall be limited. A notation shall be
filed in the real property file maintained at Engineering Field Activity, Chesapeake (EFA Ches)
(US Navy) for this site indicating the extent of the area and the fact that solid wastes are
present. The institutional controls shall also include the following: Within 90 days after
completion of the remedy, the Navy shall produce a survey plat prepared by a professional land
surveyor registered by the Commonwealth of Virginia indicating the location and dimensions of
disposal area and the extent of groundwater contamination. Monitoring well locations should be
included and identified on the survey plat. The plat shall contain a note, prominently
displayed, which states the owners future obligation to restrict disturbance (excavation or
construction) of the property; post-closure use of the property shall prohibit residential use,
access or use of groundwater underlying the property for any purpose except monitoring, and
shall not disturb the function of the monitoring systems. The owner of the property shall
submit the survey plat to the local recording authority when closure is complete. If and when
the property is transferred out of the federal government, the deed (or some other instrument
which is normally examined during title search at the local land recording authority) shall
include the survey plat a notation notifying any potential purchaser of the property that the

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land has been used to manage solid waste, and an appropriate deed restriction.

The Navy shall institute groundwater monitoring at the perimeter of the groundwater plume. It
is noted that concentrations of metals in groundwater (chromium, copper, iron, and lead) are
significantly elevated above background levels. SVOC's were also detected above background
levels in some instances. Despite the fact that modeling has not indicated a potential threat
to ecological receptors in surface water or sediments, monitoring shall be implemented to
measure concentrations of these constituents. The freguency of analysis, types of analyses, and
the length of time for monitoring shall be developed in the Operation and Management Plan.

The Navy shall monitor the surface waters and sediments in the Gambo, Creek adjacent to Site
12. The freguency of analysis, types of analyses, and the length of time for monitoring shall
be developed in the Operation and Management Plan.

Based on available information and the current understanding of site conditions, Alternative 4
appears to provide the best balance with respect to the nine NCP evaluation criteria. In
addition, the selected alternative is anticipated to meet the following statutory reguirements:

6 Protection of human health and the environment.
6 Compliance with ARARs.
6 Cost-effectiveness.

The institutional controls will further protect human health and the environment by limiting
future land use and by providing continuous monitoring. As discussed previously in this ROD, a
separate study will be prepared which addresses possible surface water and sediment
contamination in Gambo Creek.

2.8.1 Performance Standards

Air Sparging/Soil Vapor Extraction System

The selected remedy shall consist of a minimum of two air sparging and two soil vapor extraction
wells placed in the source area (see Figure 2-4 and 2-5) and along the downgradient plume, as
defined by the groundwater monitoring network. (The optimum number of AS/SVE wells shall be
determined by the pilot-scale study). The remedy shall achieve the remediation goals provided
in Table 2-5 within the area of Site 12.

The Navy shall conduct risk assessment, prior to implementation of the selected remedy, to
demonstrate that no excess human health risks result from the planned emissions.

RCRA Groundwater Monitoring Wells

A groundwater monitoring network will be installed around the perimeter of the unit to evaluate
the progress of the AS/SVE system and any future contaminant transport. The location and number
of monitoring wells, the freguency of analyses, the types of analyses, and the length of
monitoring shall be determined in the site design and operation and management documents. These
documents must be approved by the EPA and the Commonwealth of Virginia. The wells will be
installed according to RCRA and Commonwealth of Virginia construction reguirements.

TABLE 2-5

SUMMARY OF REMEDIATION GOALS
NSWCDL DAHLGREN, VIRGINIA

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                                             Media
Chemical of Concern    Maximum Groundwater            Maximum Subsurface
                       Concentration  (Ig/1)        Soils Concentration  (mg/kg)
1,1,1-Trichloroethane        5,320                          39.5
1,1-Dichloroethane           9,650                           N/A
Surface Water and Sediment Monitoring

A surface water and sediment sampling and monitoring plan shall be developed as part of the
Operation and Management  (0 & M) Plan.  The location and number of sampling locations, the
freguency of analyses, the types of analyses, and the duration of monitoring shall be determined
in the 0 & M Plan.  This plan must be approved by the EPA and the Commonwealth of Virginia.

Institutional Controls

The Navy shall institute the following institutional controls within 90 days of completion of
the installation of the AS/SVE system:  a real property description notation, Base Master Plan
notations, and limited site access.  Signs shall be posted indicating hazardous substances are
present.  The signs shall be removed at the completion of the remedy.  The Base Master Plan
shall note the area as one in residential development can not occur, shallow groundwater can not
be used, and site access shall be limited.  A notation shall be filed in the real property file
maintained by Engineering Field Activity, Chesapeake (EFA Ches) (US Navy) for this site
indicating the extent of the area and the fact that solid wastes are present.  The institutional
controls shall also include the following:  within 90 days after completion of the remedy, the
Navy shall produce a survey plat prepared by a professional land surveyor registered by the
Commonwealth of Virginia indicating the location and dimensions of disposal area and the extent
of the groundwater contamination plume.  Monitoring well locations shall be included and
identified on the survey plat.  The plat shall contain a note, prominently displayed, which
states the owner's future obligation to restrict disturbance  (excavation or construction)  of the
property; post-closure use of the property shall prohibit residential use, access or use of
groundwater underlying the property for any purpose except monitoring, and shall not disturb the
function of the monitoring systems.  The owner of the property shall submit the survey plat to
the local recording authority when closure is complete.If and when the property is transferred
out of the federal government, the deed  (or some other instrument which is normally examined
during title search at the local land recording authority) shall include the survey plat and
shall contain a notation notifying any potential purchaser of the property that the land has
been used to manage solid waste, and an appropriate deed restriction.

In the yearly 0 & M Report, the Navy shall certify that the institutional controls as outlined
above are still in-place and effective.  The Navy shall notify USEPA and VDEQ 60 days before
changing any of the use restrictions in the Base Master Plan related to Site 12.

2.9     STATUTORY DETERMINATIONS

Remedial actions must meet the statutory reguirements of Section 121 of CERCLA as discussed
below.

Remedial actions undertaken at NPL sites must achieve adeguate protection of human health and
the environment, comply with applicable or relevant and appropriate reguirements of both Federal
and state laws and regulations, be cost-effective, and utilize, to the maximum extent
practicable, permanent solutions and alternative treatment or resource recovery technologies.
Also, remedial alternatives that reduce the volume, toxicity, and/or mobility of hazardous waste
as the principal element are preferred.

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The following discussion summarizes the statutory requirements that are met by the selected
remedy.

2.9.1 Protection of Human Health and the Environment

The selected remedy will be protective of human health and the environment because the primary
COCs present in the groundwater (1,1,1-TCA and 1,1-DCA) will be removed until risk-based
remedial action objectives are achieved. These RAOs were developed during the ecological risk
assessment and are based on modeling. The removal of VOCs in the subsurface soils will
eliminate potential ecological risks associated with potential VOC migration to groundwater and
sediments.

2.9.2 Compliance with ARARs

The selected remedy will achieve all ARARs. ARARs that have been identified for Site 12 are
presented in Appendix C.

Discharges of off-gases during the long-term operation of the AS/SVE system shall be monitored
and the system operated to maintain compliance with Commonwealth of Virginia regulation 9 VAC
5-50 as well as the EPA OSWER Directive (9355.0-28) limit of 15 pounds per day VOCs for air
emissions from Superfund remedial actions, and the Clean Air Act requirements. In addition
prior to implementation, a risk assessment shall be conducted to demonstrate that no excess
human health asks will result from the emissions. The AS/SVE treatment facility shall be
constructed outside the 100-year floodplain, fulfilling the Clean Water Act requirements.

New monitoring wells shall be installed in accordance with Commonwealth of Virginia
requirements. The specific analytical methods, procedures and sampling frequency will be
specified in the O&M plan. Substantive permit and licensing requirements shall be followed.
Land-use and access restrictions, described in Section 2.8, shall limit the use and development
of the property.

2.9.3 Cost-Effectiveness

The selected remedy is cost-effective because it will provide overall effectiveness proportional
to the cost. Although more costly than long-term monitoring, the selected remedy will achieve
remediation goals more quickly and efficiently than other alternatives, provide greater
long-term protection of human health and/or the environment, and meet all identified ARARs.

2.9.4 Utilization of Permanent Solutions and Alternative Treatment Technologies or
Resource Recovery Technologies to the Maximum Extent Practicable

The selected remedy uses an alternative treatment technology, AS/SVE. AS/SVE is a permanent
solution and is an appropriate remedy for soils and groundwater contaminated with VOCs.

2.9.5 Preference for Treatment as a Principal Element

The selected remedy does not satisfy the statutory preference for treatment as a principal
element. Because low levels of VOCs (less than 15 pounds per day) are planned to be
generated, no treatment of emissions is planned. If additional volumes of VOCs are generated,
the option exists to treat the off gasses. Therefore, this action may satisfy this preference.

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                                           3.0 RESPONSIVENESS SUMMARY

The selected remedy for Site 12 is an air sparging/soil vapor extraction system.  No written
comments, concerns, or guestions were received by the Navy, EPA, or the Commonwealth of
Virginia during the public comment period from July 16, 1997 to August 15, 1997.  A public
meeting was held on August 6, 1997 to present the Proposed Plan for Site 12 and to answer any
guestions on the Proposed Plan and on the documents in the information repositories.  No
formal guestions were asked during the meeting.  Based on the limited comments, the Public
appears to support the selected remedy.
A
copy of the certified transcript of the Public Meeting is attached as Appendix B.
The Virginia Department of Environmental Quality, representing the Commonwealth of Virginia,
concurs with the selected remedy.

3.1     Background on Community Involvement

The Navy and NSWCDL have had a comprehensive public involvement program for several
years.  Starting in 1993, a Technical Review Committee  (TRC) would meet on average twice a
year to discuss issues related to investigative activities at NSWCDL.  The TRC was comprised of
mostly governmental personnel, however a few private citizens attended the meetings.

In early 1996, the Navy converted the TRC into a Restoration Advisory Broad (RAS)  and 8-10
community representatives joined.  The RAB is co-chaired by a community member and has
held meetings approximately every four to six months since.  The Feasibility Study for Site 12
and the Proposed Plan were both discussed at the RAB meetings and a Site 12 tour was
undertaken during a special RAB meeting.

Community relations activities for the final selected remedy include:

The documents concerning the investigation and analysis at Site 12, as well as a copy of the
Proposed Plan was placed in the information repository at the NSWCDL library and the King
George Public Library.

Copies of the documents, including the Proposed Plan were sent to members of the RAB.

Newspaper announcements on the availability of the documents and the public comment
period/meeting date was placed in the Freelance Star Newspaper on July 15, 1997.

The Navy established a 30-day public comment period starting July 18, 1997 and ending August
15, 1997 to present the Proposed Plan.  No written comments were received during the 30-day
public comment period..

A Public Meeting was held August 6, 1997 to answer any guestions concerning the Site 12
Proposed Plan.  Approximately 20 people, including Federal, State and local government
representatives attended the meeting.
                                      APPENDIX A

                               VIRGINIA CONCURRENCE LETTER

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                             APPENDIX B

                       RESPONSIVENESS SUMMARY

                      NAVAL SEA SYSTEMS COMMAND

                     NAVAL SURFACE WARFARE CENTER
                           DAHLGREN DIVISION

                            PUBLIC MEETING


                 WEDNESDAY, AUGUST 6, 1997, 7:00 P.M.

              KING GEORGE COUNTY ADMINISTRATION BUILDING
                         KING GEORGE, VIRGINIA

                       PROPOSED REMEDIAL ACTION PLAN
                        Site 12, Chemical Burn Area
USEPA Region III
Hazardous Waste Management Division
Federal Facilities Section
Mr. Bruce Beach
841 Chestnut Building, Philadelphia, Pennsylvania, 19107

Virginia Department of Environmental Quality
Mr. David Gillispie
629 East Main Street, Richmond, Virginia 23225

Public Affairs Office
Commander, Naval Surface Warfare Center
Ms. Jennifer Wilkins
17320 Dahlgren Road, Dahlgren, Virginia 22448
                           Reported by:  Paula J. Evans

          FRANCES K. HALEY & ASSOCIATES, Court Reporters
     10500 Wakeman Drive, Suite 300, Fredericksburg, VA 22407
           PHONE:   (540)898-1527    FAX:   (540)898-6154

August 6, 1997:
          There were no formal guestions on the floor at this Meeting.

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                    FRANCES K. HALEY ASSOCIATES, Court Reporters
              10500 Wakeman Drive, Suits 300, Fredericksburg, VA 22407
                     PHONE:  (540)898-1527    FAX:  (540)898-6154
                            CERTIFICATE OF COURT REPORTER


I, Paula J. Evans, hereby certify that I was the

Court Reporter at the Public Meeting held at King George

county Administration Building, King George, Virginia, on

August 6, 1997, at the time of the meeting herein.

I further certify that the foregoing transcript is a

true and accurate record of the proceeding herein.

            Given under my hand this 19th day of August, 1997.




          FRANCES K. HALEY & ASSOCIATES,        Court Reporters
     10500 Wakeman Drive, Suite 300, Fredericksburg, VA 22407
            PHONE:   (540)898-1527   FAX:   (540)898-6154

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ARAR or TBC

I.  LOCATION
   SPECIFIC
                                                  APPENDIX C
                             Applicable or Relevant and Appropriate Requirements
                                          Site 12 Chemical Burn Area
                                          NSWCDL, Dahlgren, Virginia
  Regulation
                                      Classification
                         Requirement Synopsis
   Applicability to Remedial
        Alternatives
Endangered
Species Act of
1978

Virginia
Endangered
Species
Regulations

Virginia Board of
Game and Inland
Fisheries: Virginia
Endangered Plant
and Insect Species
Regulations
16 USC 1531-1544
C.F.R. Part 402

VR 325-01-1
4 VAC 15-20-130
Code of Virginia
Sections 29.1-100
and 29.1-563

VR 115-04-01
2VAC 5-320-10
Applicable      Act requires federal agencies to ensure that
                any action authorized by an agency is not
                likely to jeopardize the continued existence
                of any endangered or threatened species or
                adversely affect its critical habitat. Similar
                Virginia requirements for submittal and
                review of environmental assessments.
Applicable      The Department of Game and Inland
                Fisheries (DGIF)  determines if rare,
                threatened or endangered animal species or
                their habitats are threatened by remediation
                of the site. Certain species of fish and
                wildlife are afforded special preservation
                and protection measures. The Department
                of Conservation and Recreation (OCR)
                determines if any ecologically significant
                areas are threatened by the remediation of
                the site.
Potentially affected endangered
species have not been
identified. The remedial action
will be implemented so
resources are not adversely
affected should any be
identified in the future.
Potentially affected endangered
species have been identified.
The remedial action will be
implemented so resources are
not adversely affected should
any be identified in the future.

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                                                  APPENDIX C
                             Applicable or Relevant and Appropriate Requirements
                                          Site 12 Chemical Burn Area
                                          NSWCDL, Dahlgren, Virginia
ARAR or TBC

The Archaeological
and Historical
Preservation Act of
1974

Virginia Historic
Resources Law
Regulation

16 U.S.C ° 469
Classification

Applicable
VR 10.1-2200-2214
    Requirement Synopsis

Requires actions to avoid potential loss or
destruction of significant scientific,
historical, or archaeological data.
  Applicability to Remedial
        Alternatives
Site is not known to be within a
historically significant area. If
future resources are identified
actions will be taken to ensure
compliance.
Migratory Bird
Treaty Act
16 USC Section 703  Applicable
                  Protects almost all species of native birds
                  in the U.S. from unregulated "take" which
                  can include poisoning at hazardous waste
                  sites.
                                               Remedy will be implemented
                                               to ensure that hazardous wastes
                                               have no impacts to native birds.
Chesapeake Bay
Preservation Act
VR 173-02-01
9 VAC 10-20-10
Applicable        Requires certain locally designated tidal
                  and non-tidal wetlands and other sensitive
                  areas be subject to limitations regarding
                  land-disturbing activities, removal of
                  vegetation, use of impervious cover,
                  erosion and sediment control, and
                  stormwater management.
                                               Remedy implementation will
                                               require construction activities.
                                               Actions will address the
                                               regulatory requirements.

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ARAR or TBC

Resource
Conservation and
Recovery Act
Virginia Solid and
Hazardous Waste
Management
Regulations

Virginia Water
Control Board
Regulations
Executive Order
11990, Protection
of Wetlands
                                                  APPENDIX C
                             Applicable or Relevant and Appropriate Reguirements
                                          Site 12 Chemical Burn Area
                                          NSWCDL, Dahlgren, Virginia
Regulation

40 C.F.R. 264.18
(b)
40 C.F.R. 262.10
(a)
40 C.F.R. 262:11

9VAC 20-80-10
9VAC 20-60-10
VR 680-21-04
9 VAC 25-260-10
Classification

Applicable
Virginia Wetlands
Regulations
40 C.F.R. 6,
Appendix A

Clean Water Act of
1972  (CWA)

Section 404

VR 450-01-0051
4 VAC 20-390-10
Relevant and
Appropriate
Applicable
     Reguirement Synopsis

Applies to generation, treatment, storage,
or disposal of solid and hazardous waste.
Facility or activity design must adeguately
address the issues arising from locating in
wetlands, delineated (wellhead protection
areas determined vulnerable).
Action to minimize the destruction, loss, or
degradation of wetlands.
                  Any Activity to take place in, or impact on,
                  a tidal wetland must meet the provisions of
                  Virginia Wetlands Act and regulations as
                  applicable.
 Applicability to Remedial
        Alternatives
Remedy implementation may
produce incidental hazardous
wastes which will be managed
consistent with federal and
Virginia reguirements.
Remedy implementation is not
expected to involve wetland or
wellhead protection areas. If
identified, actions will address
the regulation.

Portions of the site adjacent to
Gambo Creek are characterized
as wetlands. Remedy
implementation will be
completed to avoid wetland
impacts.

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ARAR or TBC

II. ACTION
    SPECIFIC
                                                  APPENDIX C
                             Applicable or Relevant and Appropriate Requirements
                                          Site 12 Chemical Burn Area
                                          NSWCDL, Dahlgren, Virginia
Regulation
                                          Classification
                       Requirement Synopsis
                                                  Applicability to Remedial
                                                        Alternatives
Solid Waste
Management Act
Virginia
Regulations
Governing
Transportation of
Hazardous
Materials
(VRGTHM)

Erosion and
Sediment Control
VR 625-02-00
9 VAC 20-80-10
VR 670-30-01
9 VAC 20-110-10
Relevant and
Appropriate
Applicable
VR 625-02-00
4 VAC 50-30-10
Applicable
Permanent Closure Criteria governing:
Access Restriction, site monitoring, and
compliance with other permanent closure
requirements.

The VRGTHM designates the manner and
method by which hazardous materials are
loaded, packed, identified, marked,
placarded, stores and transported.
Erosion and sediment control plans are to
be submitted for land-disturbing activities,
and be in compliance with of the locality
and/or local soil and water conservation
district.
Installation of the remedy will
require on-going institutional
controls which will be
addressed by the regulations.

Transportation of Hazardous
waste must be conducted in
compliance with VRGTHM
will be addressed by the
regulations.
Construction activities will
disturb the land in the vicinity
of the site. Activities will
address Virginia erosion and
sediment control requirements.

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                                                 APPENDIX C
                            Applicable or Relevant and Appropriate Requirements
                                         Site 12 Chemical Burn Area
                                         NSWCDL, Dahlgren, Virginia
AIR

Clean Air Act
Virginia
Regulations for the
Control and Abate-
ment of Air
Pollution
Air Emissions
Clean Air Act 40
C.F.R. 61 Subpart C

Virginia VRCAAP
VR 120-01-01
through 120-08-
0605

9 VAC 5-10-10
through 5-80-350

OSWER Directive
9355.0-28
Applicable
                                              To Be
                                              Considered
Stipulate requirements for compliance with
emissions of toxic pollutants in attainment
and non-attainment areas; permitting
procedures and monitoring requirements
for processes emitting pollutants.
             For air stripping operations that have no
             mechanism to capture or treat emissions,
             emissions are limited to a maximum of 3
             pounds per hour or 15 pounds per day of
Remedy implementation will
involve discharges of VOCs to
the atmosphere. Emissions
will be consistent will federal
and state regulations.
                                              Emissions of VOCs from the
                                              AS/SVE system will consider
                                              limitations on quantity of
                                              VOCs discharged.
                                                           VOCS in ozone non-attainment areas.
Virginia Ambient
Air Quality
Standards
VR120-03-01
9 VAC 5-30-01
Applicable   Stipulates requirements for compliance
             with emissions of toxic pollutants in
             attainment and non-attainment areas;
             permitting procedures and monitoring
             requirements for processes emitting
             pollutants; any emission from the
             disturbance of soil must meet Virginia air
             emission standards for toxic pollutants
             particualtes and VOC's.
                                              Remedy implementation will
                                              involve discharges of VOC's to
                                              the atmosphere.  Emissions
                                              will be consistent with federal
                                              and state regulations.

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                                                  APPENDIX C
                             Applicable or Relevant and Appropriate Requirements
                                          Site 12 Chemical Burn Area
                                          NSWCDL, Dahlgren, Virginia
WATER
Water Quality
Standards
VR 680-15-02
9 VAC 25-210-10
Water Quality
Standards
VR 680-15-02
9 VAC 25-210-10
Water Quality
Standards
VR 680-21 -00
9 VAC 25-260-10
Relevant and   Criteria and standards for groundwater
Appropriate    quality. Virginia regulation provides basis
               for risk-based remediation and discharge
               limitations.
Relevant and   Subsurface borings of all types shall be
Appropriate    constructed, operated and closed in a
               manner which Protects groundwater.
Applicable     Groundwater monitoring stations shall be
               located and constructed in a manner that
               allows accurate determination of
               groundwater quality and levels, and
               prevents contamination of groundwater
               through the finished well hole or casing.
               All groundwater monitoring stations shall
               be accurately located utilizing latitude and
               longitude by surveying, or other acceptable
               means, and coordinates shall be included
               with all data collected.
Provides basis for risk-based
decision making,  establishes
standards for groundwater
quality. Ongoing monitoring at
Site 12 will address the
requirement.

Completion of additional soil
borings, monitoring wells and
subsurface investigations will
be consistent with regulatory
requirements.

Completion of additional soil
borings, monitoring wells and
subsurface investigations will
be consistent with regulatory
requirements.

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                                                   APPENDIX C
                             Applicable or Relevant and Appropriate Requirements
                                          Site 12 Chemical Burn Area
                                          NSWCDL, Dahlgren, Virginia
Pollution Discharge
Elimination System
(VPDES); Virginia
Pollution
Abatement (VPA)
Permit Program
VR 680-14-01
9 VAC 25-30-10
Applicable
Procedures and requirements for
discharging pollutants into surface waters,
or any activity which impacts physical,
chemical or biological properties of surface
waters.
Water Quality
Standards
VR 672-10-01
Water Quality
Standards
VR 672-10-01
Virginia
Stormwater
Management
Regulation
VR 215-02-00
4 VAC 3-20-10
                  Relevant and
                  Appropriate
                  Relevant and
                  Appropriate
Applicable
               Monitoring well design Standards.
               Monitoring well Drillers certification.
All land disturbing activities must be in
compliance with local stormwater
management programs, where they exist.
Air sparging of groundwater at
Site 12 is not expected to
produce waste liquids that
would be discharged to surface
waters. Any future activities or
groundwater monitoring (e.g.

generation of purge water) will
address regulatory
requirements.

Completion of additional soil
borings, monitoring wells and
subsurface investigations will
be consistent with regulatory
requirements.

Completion of additional soil
borings, monitoring wells and
subsurface investigations will
be consistent with regulatory
requirements.

Remediation activities must
meet requirements.

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