Superfund Record of Decision Aberdeen Proving Ground Edgewood Area Cluster 1 Former Nike Site Edgewood Maryland


                                    EPA/ROD/R03-96/230
                                    1996
EPA Superfund
     Record of Decision:
     ABERDEEN PROVING GROUND (EDGEWOOD AREA)
     EPA ID: MD2210020036
     OU11
     EDGEWOOD, MD
     09/27/1996

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                  CLUSTER 1,  FORMER NIKE SITE
                         EDGEWOOD AREA
                    ABERDEEN PROVING GROUND

                       RECORD OF DECISION

                          Submitted to

                  Environmental Conservation and
                      Restoration Division
              Aberdeen Proving Ground, Maryland 21010

                    Submitted and Prepared by

             HAZARDOUS WASTE REMEDIAL ACTIONS PROGRAM
         Environmental Management and Enrichment Facilities
                   Oak Ridge, Tennessee 37831
                           managed by
               LOCKHEED MARTIN ENERGY SYSTEMS,  INC.
                            for the
                    U.S. DEPARTMENT OF ENERGY
                 under contract DE-AC05-840R21400

                             And by

                          Dames & Moore
               849 International Drive, Suite 320
                     Linthicum, Maryland 21090
               Under General Order No. 70B-99786C
                         Work Release K09

                          September 1996

In accordance with Army Regulations 200-2, this document is intended to
   comply with the National Environmental Policy Act (NEPA) of 1969.

                          SEPTEMBER 1996

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CONTENTS

LIST OF FIGURES iv

LIST OF TABLES iv

LIST OF ACRONYMS vi

1. DECLARATION OF THE RECORD OF DECISION 1-1
1.1 SITE NAME AND LOCATION 1-1
1.2 STATEMENT OF BASIS AND PURPOSE 1-1
1.3 ASSESSMENT OF THE SITE 1-1
1.4 DESCRIPTION OF THE SELECTED REMEDIES 1-1
1.4.1 Selected Remedy for Contaminated Groundwater 1-2
1.4.2 Selected Remedy for Launch Southwest Landfill 1-2
1.4.3 Selected Remedy for Sanitary Sewer System 1-2
1.4.4 Selected Remedy for Nike Missile Silos 1-2
1. 5 STATUTORY DETERMINATIONS 1-2

2. DECISION SUMMARY 2-1
2.1 SITE NAME, LOCATION, AND DESCRIPTION 2-1
2.2 SITE HISTORY AND ENFORCEMENT ACTIVITIES 2-4
2.2.1 History of Cluster 1 2-4
2.2.2 Enforcement Activities 2-4
2.3 HIGHLIGHTS OF COMMUNITY PARTICIPATION 2-5
2.4 SCOPE OF ROLES OF CLUSTER 1 2-6
2.5 SUMMARY OF SITE CHARACTERISTICS 2-6
2. 6 SUMMARY OF SITE RISKS 2-9
2.6.1 Human Health Risks 2-9
2.6.2 Environmental Risks 2-19
2.7 GROUNDWATER REMEDIATION 2-21
2.7.1 Description of Alternatives 2-21
2.7.2 Summary of the Comparative Analysis of Alternatives 2-25
2.7.3 Selected Remedy 2-30
2.7.4 Statutory Determinations 2-31
2. 8 LANDFILL REMEDIATION 2-38
Description of Alternatives 2-38
Summary of the Comparative Analysis of Landfill Cleanup Alternatives 2-41
Selected Remedy 2-42
Statutory Determinations 2-44
2.9 SLUDGE (SANITARY SEWER SYSTEM) REMEDIATION 2-49
2.9.1 Description of Alternatives 2-49
2.9.2 Summary of the Comparative Analysis of Sanitary Sewer System Cleanup
Alternatives 2-51
2.9.3 Selected Remedy 2-53
2.9.4 Statutory Determinations 2-53
2.10 DOCUMENTATION OF SIGNIFICANT CHANGES 2-56

3. RESPONSIVENESS SUMMARY 3-1

4. REFERENCES 4-1

LIST OF FIGURES

Fig. 1. Former Nike Site-Location Map 2-2
Fig. 2. Former Nike Site-Site Plan 2-3
Fig. 3. Former Nike Site-Approximate Area of Groundwater Plume 2-7

LIST OF TABLES

Table 1. Summary of Chemicals of Potential Concern Detected in Surficial Aguifer
Groundwater at Cluster 1 Not Eliminated Based on Risk-Based or Background Levels .... 2-8
Table 2. Parameters Indicated by Analysis of Sludge in Septic Sewer Lines That Exceed
Preliminary screening Criteria and Cannot Be Disregarded Based on Background
or Risk-Based Levels 2-10
Table 3. Summary of Chemicals of Potential Concern at Cluster 1, Aberdeen Proving Ground .... 2-11
Table 4. Summary of Pathway Specific and Cumulative Risks, Cluster 1, Current Land-Use

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          Conditions 	
Table 5.  Summary of Pathway-Specific and Cumulative Risks,  Cluster 1,  Future Land-Use
          Conditions 	
Table 6.  USEPA Evaluation Criteria for Remediation (Cleanup)  Alternatives 	
Table 7.  Comparison of Groundwater Remedial Action Alternatives 	
Table 8.  Cost Estimate, Groundwater Alternative 5 	
Table 9.  Comparison of Landfill Remedial Action Alternatives 	
Table 10.   Cost Estimate, Landfill Alternative 2 	
Table 11.   Comparison of Sludge Remedial Action Alternatives 	
Table 12.   Cost Estimate Sanitary Sewer System Alternative 2 	
2-15

2-16
2-26
2-27
2-32
2-43
2-45
2-52
2-54
                                         LIST OF ACRONYMS
AEHA          Army Environmental Hygiene Agency
APG           Aberdeen Proving Ground
ARARs         applicable or relevant and appropriate reguirements
AWQC          Ambient Water Quality Criteria
BRAG          Base Realignment and Closure
CERCLA        Comprehensive Environmental Response,  Compensation
              and Liability Act
CFR           Code of Federal Regulations
COMAR         Code of Maryland Regulations
CPF           cancer potency factor
CWM           chemical warfare material
ERA           Ecological Risk Assessment
FS            Feasibility Study
HI            Hazard Index
HQ            hazard guotient
MCL           maximum contaminant level
MDE           Maryland Department of the Environmental
NCP           National Contingency Plan
NPDES         National Pollutant Discharge Elimination  System
NPL           National Priorities List
O&M           operations and maintenance
OSHA          Occupational Safety and Health Administration
PAHs          polynuclear aromatic hydrocarbons
PCB           polychlorinated biphenyl
RA            Risk Assessment
RAO           remedial action objective
RCRA          Resource Conservation and Recovery Act
RFA           RCRA Facility Assessment
RfDs          reference doses
RFI           RCRA Facility Investigation
RI            Remedial Investigation
RI/FS         Remedial Investigation/Feasibility Study
RME           reasonable maximum exposure
ROD           Record of Decision
SARA          Superfund Amendments and Reauthorization  Act
SBR           seguencing batch reactor
SQC           sediment guality criteria
TCE           trichloroethene,  trichloroethylene
TEU           Technical Escort Unit
TRVs          toxicity reference values
USEPA         U.S. Environmental Protection Agency
UV            ultraviolet
UXO           unexploded ordnance
VOCs          volatile organic compounds

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1. DECLARATION OF THE RECORD OF DECISION

1.1 SITE NAME AND LOCATION

Cluster 1, former Nike Missile Site (Nike Site), Edgewood Area, Aberdeen Proving Ground (APG),
Maryland.

1.2 STATEMENT OF BASIS AND PURPOSE

This Record of Decision (ROD) document presents the remedial actions selected to reduce the risks
posed by contaminated shallow groundwater, the Launch Southwest Landfill, and Launch Area septic/siphon tanks
and sewer lines (hereinafter referred to as sanitary sewer system), and six decommissioned Nike missile silos
located at the Nike Site (Cluster 1 of the Lauderick Creek Area) at APG, Maryland. These remedial actions
were developed in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act
of 1980 (CERCLA), as amended by the 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. Documents contained in the Administrative
Record are identified in Sect. 2.2.

The U.S. Environmental Protection Agency (USEPA) and the Maryland Department of the Environment (MDE)
concur on the selected remedies.

1.3 ASSESSMENT OF THE SITE

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

1.4 DESCRIPTION OF THE SELECTED REMEDIES

The Cluster 1 cleaning is part of a comprehensive environmental investigations and cleanup currently
being performed at APG under the CERCLA program. APG is divided into 13 study areas comprising 55 clusters
that encompass potential sources of contamination. Cluster 1 of the Nike Site is part of the
Lauderick Creek Study Area. The remaining clusters of the Lauderick Creek Study Area and the other study
areas are being addressed as separate actions.

This action addresses the principal threats at the Nike Site in four ways: extracting and treating
contaminated groundwater, isolating the Launch Southwest Landfill as a potential source of contamination
by installing an impermeable composite cap, removing contaminants from the sanitary sewer system and
filling the system with an inert material, and accepting the interim missile silo remedial action (removal of
contaminated liguids and filling the silos with an inert material) as the final action. This four-part
remedy minimizes the risk associated with exposures to contaminated materials by removing the source(s) of
contamination where possible, by isolating from the environment potential contaminants that will remain in
place (Launch Southwest Landfill), and by limiting access to the site and affected groundwater. The major
components of the selected remedy, arranged by site/feature, are presented in the following sections.

1.4.1 Selected Remedy for Contaminated Groundwater

Removal of groundwater using extraction wells and treatment of the water using aboveground
reductive dehalogenation.
Discharge of treated water to a tributary of the Bush River.
Long-term groundwater monitoring to ensure reduction of contaminants to clean-up levels.
Land-use restrictions prohibiting the use of on-site groundwater.

1.4.2 Selected Remedy for Launch Southwest Landfill

Installation of a composite cap over the landfill (approximately 1.1 acres).
Institution of land-use restrictions.
Installation of a chain link fence.
Installation of groundwater monitoring wells and long-term groundwater monitoring.

1.4.3 Selected Remedy for Sanitary Sewer System

Remove sludge from sewer system.
High-pressure water blast sewer lines, manhole, and tanks to clean the system.
Fill clean tanks, manholes, and pipes with inert material (e.g., concrete grout or slurry mixture).
Remove all surficial structures, regrade, and vegetate.

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Dispose of the sludge and wash water off-site.

1.4.4 Selected Remedy for Nike Missile Silos

No further action will be concluded on the Nike Missile Silos. It is recommended that the removal
action-which included pumping the lead-contaminated water from the six silos, transporting the water
off-site for treatment, and filling the six missile silos with concrete-be accepted as the final
action.

1.5 STATUTORY DETERMINATIONS

The selected remedies are protective of human health and the environment, comply with federal and
state reguirements that are legally applicable or relevant and appropriate to the remedial action, and are
cost-effective. The remedies use permanent solutions and alternative treatment technologies to the
maximum extent practicable. The selected remedy for contaminated groundwater (on-site treatment)
meets the statutory preference for remedies employing treatment that reduces the toxicity, mobility, or
volume as a principal element. The capping of the landfill and the off-site transport and disposal of sludge
reduce the mobility of contaminants by placing them in controlled, monitored locations. However, these
remedies do not meet the statutory preference for treatment that reduces the volume or toxicity of
contaminants. With respect to landfill wastes, the potential presence of unexploded ordnance (UXO), and
the fact that no major sources of contaminants have been identified, support a contaminant rather than a
removal remedy. Because some of the remedies discussed above do not allow for unrestricted future use
of the site, a review will be conducted within 5 years after commencement of remedial actions to ensure
adeguate long-term protection of human health and the environment is maintained.

2. DECISION SUMMARY

2.1 SITE NAME, LOCATION, AND DESCRIPTION

Cluster 1 is located in the Lauderick Creek Study Area of APG, in Harford County, approximately
45 miles north of Baltimore, Maryland (see Fig. 1). APG is bordered to the east and south by the
Chesapeake Bay; to the west by Gunpowder Falls State Park, the Crane Power Plant, and residential
areas; and to the north by the towns of Edgewood, Joppa, Magnolia, Ferryman, and Aberdeen. APG is
divided by the Bush River into two main areas; the Edgewood Area of APG lies to the west of the river
and the Aberdeen Area lies to the east. The Edgewood Area, including Graces Quarters and Carroll
Island, is listed in the National Priorities List (NPL) . The NPL is USEPA's list of U.S. hazardous waste
sites considered priorities for long-term remedial evaluation and response.

The Nike Site, also referred to as Cluster 1 of the Lauderick Creek Area, is located in the northeast
portion of the Edgewood Area. The Nike Site is bordered to the west and north by the installation boundary,
the Amtrak railroad tracks, and residential areas; and by wooded and marshy areas of the Lauderick Creek Area
to the south and east. The Nike Site consists of approximately 300 acres, of which a 102.2-acre portion was
originally designated for closure under the Department of Defense Base
Realignment and Closure (BRAG) program. The site is no longer considered part of this program, and all
further actions will be conducted as a standard CERCLA activity. The launch area, located at the northern
end of Cluster 1 to the west of Monks Creek (see Fig. 2), includes six abandoned missile silos, several
buildings, a 1.1-acre landfill, and a septic tank/subsurface sand filter bed system. An abandoned
underground fuel oil storage tank was removed from the launch area in 1991. The barracks area, located
southwest of the launch area (see Fig. 2), consists of five buildings, a septic tank, and a subsurface sand
filter bed. In addition, five underground fuel oil storage tanks were installed in the barracks area in
1957, four remain in use.

Cluster 1 and the surrounding area consist of forest, open field, and wetlands. The adjacent area
north of the Amtrak line consists of forest and a resident subdivision. Residential subdivisions exist and,
based on zoning, may be built throughout the area north of the Amtrak line in the near future. All residents
are expected to use the public water supply; according to the Harford County Health Department, the use of
wells for domestic water supply in homes scattered in the area was discontinued in the 1970s when public
water service was established.

Ground elevations at Cluster 1 range from bay-level along creeks to about 40 ft above mean sea level
at high points immediately south of Amtrak right-of-way. Terrain consists of subtly rolling flatlands
separated by shallow swales and a tributary to Lauderick Creek and Monks Creek. The overall slope of
the terrain is to the south and east toward the Bush River and the Chesapeake Bay. A very small portion
of the site lies in the 100-year floodplain.

There are two predominant groundwater aguifers in the vicinity of Cluster 1: the surficial aguifer

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and the confined aquifer. The surficial aquifer is hydraulically unconfined, with underwater tendinq to move
toward and discharqe to adjacent creeks and intermittent tributaries. The second aquifer is located about 40
ft below the surficial aquifer and is hydraulically confined, which impedes hydraulic communication with the
surficial aquifer.

2.2 SITE HISTORY AND ENFORCEMENT ACTIVITIES

2.2.1 History of Cluster 1

The Lauderick Creek Area cover approximately 1,530 acres and encompasses Cluster 1. It was used
by the U.S. Army Chemical School for a wide variety of chemical warfare traininq activities between
1920 and 1951. Traininq activities included the use and firinq of chemical ordnance; identification of
chemical aqents, riot control aqents, and smokes; decontamination of personnel and equipment; clothinq
impreqnation and launderinq; and handlinq and maintenance of chemical warfare equipment. The traininq
also provided instruction, and possibly field practice, in the disposal of chemical aqents, riot control
aqents, smokes, chemical ordnance, and chemical-aqent-contaminated material. The materials used in
traininq included smoke and tear qas, hiqh explosives, and lethal-agent-filled munitions. As a result of
these traininq activities, UXO has often been found and is still present in the Lauderick Creek Area.

The Nike Site, constructed in School Fields Four and Seven of the Lauderick Creek Area, was used
for the deployment of Nike antiaircraft missiles between 1954 and 1973. The Army deployed Nike missiles at
many sites throuqhout the United States to protect major cities and strateqic military installations from
aerial attack. There were two types of Nike missiles: the Nike Ajax, which was used between 1954
and 1959, and the Nike Hercules, which was used between 1959 and 1973. Both were two-staqe missiles;
the Ajax was armed with a hiqh-explosives warhead and the Hercules was armed with either a hiqh-
explosives or a nuclear warhead. The Nike missiles were removed from the missile silos when the Nike
Site was decommissioned in 1973.

The Nike Site at APG consists of the missile silo area (i.e., Launch Area), the Barracks Area, and the
Control Area. In the Nike Site missile silo area, Nike missile were assembled, stored, and maintained
within each of the six silos. The Barracks Area consists of five buildinqs used as livinq quarters and
office space. The Control Area is beinq investiqated under CERCLA as part of the Lauderick Creek Study Area
and therefore is not included as part of the Nike Site.

The Maryland National Guard has leased the Lauderick Creek Area, includinq the Nike Site, from the
Army since 1973. The Maryland National Guard uses the area for lightly infantry traininq.

UXO was recovered durinq activities at the Launch Area durinq ranqe-clearinq surface sweeps in 1977
and 1984 and durinq site clearance for the facility investiqation drilling. UXO may be present throuqhout
Cluster 1.

2.2.2 Enforcement Activities

2.2.2.1 Resource Conservation and Recovery Act Facility Assessment

In 1989, the U.S. Army Environmental Hyqiene Aqency (AEHA) conducted a RCRA Facility Assessment (RFA)
that addressed the entire Edqewood Area, includinq the former Nike Site. AEHA recommended that a number of
sites within the former Nike battery area be desiqnated as RCRA solid waste manaqement units requirinq
further investiqation and possible remediation. These sites included parts of the wastewater systems,
suspected landfill sites south and southwest of the Launch Area, an alleqed French drain near Buildinq E6871,
the vehicle washpad, and concrete-lined ditches within the Launch Area.

2.2.2.2 Resource Conservation and Recovery Act Facility Investiqation

While preparinq the RFA, AEHA also sampled areas of probable or suspected contamination in and
around the former Nike Site. The sample analyses became the basis of the RCRA Facility Investiqation
(RFI) conducted for the site in 1990 to identify contaminants related to prior usaqe of the area, verify
contaminant movement pathways, and provide source characterization data. The RFI concluded that past
Nike-related activities caused limited contamination and that contamination was probably limited to known
points of release. It was also suqqested that past chemical warfare material (CWM)-related releases miqht
be scattered throuqhout the area. The RFI concluded that any future release of this property for
"unrestricted" use would be severely affected by contamination related to UXO and to past traininq at the
Chemical Warfare School.

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2.2.2.3 Enhanced Preliminary Assessment/Sampling Design Plan

       An Enhanced Preliminary Assessment of the Nike Site,  conducted by the U.S. Army Corps of Engineers'
(USAGE'S) Toxic and Hazardous Materials Agency  (currently the U.S. Army Environmental Center) in 1990
recommended additional investigation and sampling.  This reguest resulted in the preparation of a Sampling
Design Plan in 1990 that focused on potential contaminant sources, locations of existing and former
facilities, and past installation activities.

2.2.2.4 Environmental Assessment and Remediation of Nike Missile Silos

       An Environmental Assessment for the Nike Missile Silos performed in 1993 for the USAGE by Roy F.
Weston recommended the silo water be removed and treated off-site and the silos be filled with an inert
material.  In July of 1993, a Work Plan to perform the work was prepared; the recommended remedial
actions were implemented in late 1993 and early 1994.

2.2.2.5 Remedial Investigation and Feasibility Study

       A remedial investigation and feasibility study (RI/FS) for Cluster 1 was initiated in 1990 to
determine the nature and extent of contamination and to identify alternatives available to clean up the area.

       The remedial investigation (RI)  identified four contaminated areas and media,  including the Launch
Area septic tanks and lines, the unconfined groundwater, the Launch Southwest Landfill, and UXO.  The
feasibility study  (FS) recommended the remedial actions presented herein, with the exception of UXO.
Although UXO was considered in the FS,  it is not discussed herein because it is being addressed
separately.

2.3 HIGHLIGHTS OF COMMUNITY PARTICIPATION

       The RI/FS and Proposed Plan for Cluster 1 of the Lauderick Creek Study Area were released to the
public on April 24, 1996.  The public comment period began on that date and ended on June 8, 1996.  The
documents constituting the Administrative Record were made available to the public at the following
locations:

       Harford County Public Library,  Aberdeen and Edgewood Branches;
       Essex Community College Library,  Baltimore, Maryland;
       Aberdeen Proving Ground, TECOM Public Affairs Office  (in the Aberdeen Area of APG):  and
       Miller Library Washington College,  Chestertown,  Maryland.

       The notice of availability of the Proposed Plan was published in the several local newspaper in
Harford and Baltimore Counties.  A public meeting was held at the Edgewood Middle School, Edgewood, Maryland,
on May 8, 1996, to inform the public of the preferred alternatives and to seek public comments.
At the meeting, representatives from APG,  the USAEC, USEPA,  MDE, ICF-Kaiser  (an environmental consultant),
and Dames & Moore  (an environmental consultant) answered guestions about conditions at the site and the
remedial alternatives under consideration.  Responses to the comments received during this period are
included in the Responsiveness Summary appended to this ROD.

2.4 SCOPE AND ROLE OF CLUSTER 1

       Cluster 1 represents one component of a comprehensive environmental investigation and cleanup
currently being performed at APG to comply with CERCLA reguirements.  This ROD addresses Cluster 1
of the Lauderick Creek Study Area, which includes contaminated shallow groundwater, a landfill, a
sanitary sewer system, and decommissioned Nike missile silos.  These areas pose potential future risks
because of possible human exposure to site contaminants through dermal contact, inhalation, or ingestion.
The purpose of this response is to prevent current or future exposure of individuals to the contaminated
groundwater, landfill wastes, sewer system, and decommissioned missile silos by removing contaminants
where possible or isolating the contaminants to prevent further migration  (e.g., capping the Launch
Southwest Landfill) where removal is not possible.

2.5 SUMMARY OF SITE CHARACTERISTICS

       The RI report investigated 19 sites and features at Cluster 1.  The RI concluded that widespread
low-level organic chemical contamination poses no current threat to human populations or the environment.
Sources of this contamination are neither conspicuous nor evident by sight or smell at the ground surface.
However, the RI did identify three sites and features with significant contamination, that is, where at least
one organic chemical parameter exceeded a preliminary screening criterion  (USAGE 1994).  Refer to Fig. 2 for
their locations.

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Surficial Aquifer Groundwater Trichloroethene (TCE)-contaminated groundwater in the surficial
aquifer is the preliminary environmental concern at Cluster 1. The contaminant plume is defined as
qroundwater with concentrations of TCE exceeding 1 microgram per liter (• g/L) as shown in Fig. 3.
Concentrations of up to 299 • g/L TCE have been detected near the center of the plume. Table 1
summarizes the chemicals of concern detected in the surficial aquifer groundwater that were not
eliminated based on risk-based or background-level screening criteria. The exact source of TCE
contamination at Cluster 1 is unknown. Based on water level data collected during the RI, it appears
the predominant direction of groundwater flow in the vicinity of the site is to the south-southeast,
toward Monks Creek. A small component of groundwater at the northern boundary appears to flow in
a northerly direction. The surficial and confined aquifers do not appear to be hydraulically
interconnected due to the presence of a continuous confining layer of clay. Therefore, the surficial
aquifer contamination is not expected to migrate downward.

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Table 1.
Summary of Chemicals of Potential
Concern Detected in Surficial Aquifer
Groundwater at Cluster 1 Not Eliminated
Based on Risk-Based or Nike Site Background Levels
Compound
delta-BHC
Benzene
Carbon disulfide
1,4-dichlorobenzene
bis (2-ethylhexyl)
phthalate
Heptachlor
Heptachlor epoxide
Tetrachloroethene
Trichloroethene
Arsenic (total)
Beryllium (total)
Mercury (total)
Nickel (total)
Arsenic (dissolved)
Beryllium (dissolved)
Mercury (dissolved)
Nickel (dissolved)
Detected
on-site concentrations
Cg/L)

0.021
1.0-6.0
11.0
3.0
3.0-109

0.018
0.018
10.0
1.0-299
4.0-5.3
0.80-1.6
0.20-2.8
31.5-207
4.3-5.8
0.71-1.1
0.47
32.3-210
Detected
background concentrations
Cg/L)
23.0

14-31
2.0
1.0
1.1-1.2
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Launch Southwest Landfill The Launch Southwest Landfill contains construction rubble with
asbestos waste. In addition, several 55-gal drums labeled hydraulic fluid were found lying empty on
their sides at the site, which suggests waste may have been disposed of there. Predesign field
investigation sampling detected asbestos in surface soil samples at the landfill. The landfill is
approximately 275 ft long by 175 ft wide and has an average depth of 8 ft. Because soil and
groundwater near the landfill were found to be uncontaminated except for the asbestos, most
contamination is believed to be limited to buried wastes.

Launch Area Sanitary Sewer System Based on results from the RI, the Launch Area septic sewer
system contains relatively small volumes of sludge and residues contaminated with a variety of
chemicals including trace metals, solvents, and pesticides. Table 2 summarizes chemicals of
potential concern detected in the sewer system sludge that could not be eliminated based on
background contaminant levels. Investigations during the RI determined that the sewer line sludge
and residue contamination are confined to within the sewer lines (USAGE, 1994). The contaminated
sludge and residue are likely distributed along the length of the 800-ft line. Although the
contamination is confined within the sewer lines, there is a small potential for contaminants to be
released to the environment if groundwater infiltrates the deteriorating lines or rainwater flushes
the contaminants out of the lines to the surrounding soils.

Nike Missile Silos In addition to the three sites/features identified in the RI, the six Nike
missiles silos were addressed in a separate interim action (USAGE 1993). Water in the missile silos
was found to contain elevated levels of lead. Therefore, the water was removed and disposed of
off-site and the silos were filled with an inert material. There is no longer a potential source of
contamination in the missile silos. It is recommended that the interim action, which has already
completed, be accepted as the final remedy for the missile silos and that no further action be
taken. For the purposes of this document, it is assumed this recommendation will be accepted and
the missile silos will not be discussed further.

2.6 SUMMARY OF SITE RISKS

2.6.1 Human Health Risks

A Human Health Baseline Risk Assessment (RA) was conducted as part of the RI to determine the
potential risk posed to human health if cleanup activities were not performed at Cluster 1. The Human
Health RA incorporated contaminant concentrations detected in samples collected during the RI, the
toxicity of those contaminants, and the possible human exposure to these contaminants. Based on this
information, conservative estimate of risk were determined using USEPA guidance to ensure potential
health effects are not underestimated. The Human Health RA consisted of contaminant identification,
exposure assessment, toxicity assessment, and risk characterization.

The purpose of contaminant identification is to evaluate the chemicals detected in various site media
and to identify the contaminants posing potential human health risk. Chemical of potential concern were
selected for evaluation in the RA based on an evaluation of the data, on a comparison to background
concentrations for inorganic chemicals, and on USEPA Region Ill's risk-based screening procedure
(USEPA 1994). Contaminants of concern were selected for groundwater (surficial and confined aguifer),
surface soil, surface water (Lauderick Creek and Monks Creek), and sediment (Lauderick Creek and
Monks Creek). Table 3 summarizes the contaminants of concern selected for each medium of concern.
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Table 2 .
Parameters Indicated by Analysis of Sludge
in Septic Sewer Lines That Exceed Preliminary
Screening Criteria and Cannot Be Disregarded
Based on Background or Risk-Based Levels
Parameter
Maximum
concentration
detected
Preliminary
screening criteria
1, 4-dichlorobenzene
bis (2-ethylhexyl)
phthalate
Aroclor-1254
Aroclor-1260
Arsenic
Beryllium
Cadmium
Chromium
Manganese
Mercury
610,000 'g/kg
20,000 'g/kg
13,000 • g/kg
1500 • g/kg
5.3 mg/kg
0.75 mg/kg
26.8 mg/kg
112 mg/kg
257 mg/kg
3.56 mg/kg
27,000 'g/kg
46, 000 • g/kg
83 • g/kg
83 'g/kg
2.3 mg/kg
0.15 mg/kg
3.9 mg/kg
3.9 mg/kg
39 mg/kg
2.3 mg/kg
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Compound
Table 3.
Summary of Chemical of Potential Concern
at Cluster 1, Aberdeen Proving Ground
Groundwater
Surface water
Sediment
Surficial
Surface soil
Confined
Lauderick
Creek
Monks Creek
Lauderick
Creek
Monks Creek
Organics

delta-BHC X
Benzene X
Benzo(a)pyrene
Carbon disulfide X
1,4-dichlorobenzene X
1,2-dichloroethene X
(total)

bis (2 ethyl-hexyl) X
phthalate
Heptachlor X
Heptachlor Epoxide X
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Table 3. (Continued)
Compound
Groundwater
Surficial
Confined
Surface soil
Surface water

Lauderick
Creek Monks Creek
Sediment
Lauderick
Creek
Monks Creek
Tetrachloroethane
Trichloroethene
X
X
Inorganics

Antimony
Arsenic
Beryllium
Cadmium
Manganese
Mercury
Nickel
Vanadium
Vanadium
X
X
X
X
X - Selected as a chemical of potential concern for this medium.
-------
The objective of the exposure assessment is to estimate the type and magnitude of potential exposures
to the contaminants of concern that are present at, or migrating from, a site. Under the current land-use
scenario, exposure pathways evaluated include incidental ingestion of chemicals in surface soil by a
caretaker or trespasser, incidental ingestion of chemicals in Lauderick Creek and Monks Creek sediment by a
trespasser, dermal absorption of chemicals in Monks Creek surface water by a trespasser, and incidental
ingestion and dermal absorption of chemicals in Lauderick Creek surface water by a trespasser. The future
uses of Cluster 1 that were considered include military, industrial, and residential. The residential
land-use scenario is the most conservative scenario and therefore it was selected for guantitative
evaluation. Exposure pathways evaluated for the future residential land-use scenario include ingestion of
groundwater from the surficial or confined aguifer by an on-site resident, inhalation of volatile organic
compounds (VOCs) in groundwater from the surficial and confined aguifers while showering by an on-site
resident, dermal absorption of chemicals in groundwater from the surficial and confined aguifers while
bathing by an on-site child, and incidental ingestion of chemicals in soil by an on-site resident. Exposures
to surface water and sediment are expected to be similar to those under the current land-use conditions and
therefore were not evaluated under the future land-use scenario.

Exposure point concentrations in soil, groundwater, surface water, and sediment were calculated as the
95% upper confidence limit on the arithmetic mean sample concentration or the maximum detected
concentration (whichever was lower). This was used as the reasonable maximum exposure (RME)
concentration (i.e., the maximum exposure that is reasonably expected to occur at a site).

Groundwater data were grouped into plumes and hot spots, and all rounds of groundwater data
available for the wells of each group were used to calculate the exposure point concentration. To evaluate
potential exposure to VOCs released from water while showering, a model was used in which indoor air
concentrations are based in the exposure point concentration in groundwater, the rate of chemical release
into the air, the buildup and decay of VOCs in shower room air, and the time-weighted average VOC
concentrations for the duration of the shower room exposure. Exposures were estimated by combining
measured or calculated environmental concentrations at the selected points with the extent,
freguency, and duration of exposure for each receptor of concern. The major assumptions about exposure
freguency and duration were consistent with USEPA guidance (USEPA 1989a, 1989b, 1991, 1992). For
example, for the future residential land-use scenario, an exposure freguency of 350 days/year (based on
exposures of 7 days/week for 50 weeks/year) and an exposure duration of 30 years [which is the USEPA
(1989a, 1991) upper bound value for living at one residence] were used.

The purpose of the toxicity assessment is to assess the toxicological hazards of contaminants of
concern as a function of the anticipated route of exposure. Quantitative indices of toxicity include cancer
potency factors (CPFs) and reference doses (RfDs). USEPA's Carcinogenic Assessment Group developed CPFs for
estimating excess lifetime cancer risks associated with exposure to potentially carcinogenic chemicals. CPFs,
which are expressed in the reciprocal dose I/(milligram per kilogram per day), [I/(mg/kg-day) ] , are
multiplied by the estimated intake of a potential carcinogen, in milligrams/kilogram/day (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 CPF. Use of
this approach makes underestimation of the actual cancer risk highly unlikely. CPFs are derived from the
results of human epidemiological studies or chronic animal bioassays to which animal-to-human extrapolation
and uncertainty factors have been applied.

RfDs have been developed by USEPA to indicate the potential for adverse health effects from exposure
to chemicals exhibiting noncarcinogenic effects. RfDs, expressed in units of 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 the effects on
humans). These uncertainty factors help ensure the RfDs will not underestimate the potential for adverse
noncarcinogenic effects. CPFs and RfDs identified for the contaminants of concern are summarized in Tables
7.9 and 7.10 of the RA.

The purpose of the risk characterization is to relate exposure estimates to toxicity data to estimate
potential health hazards/risks. Excess lifetime cancer risks are determined by multiplying the intake level
by the CPF. These risks are probabilities that are generally expressed in scientific notation (e.g., 1 x
10-6 or 1E-06). An excess lifetime cancer risk 1 x 10-6 indicates that, as a plausible upper bound, an
individual has a 1 in 1 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. USEPA's acceptable risk range for
cancer is 1 x 10-4 to 1 x 10-6, meaning there is 1 additional chance in 10,000 (1 x 10-4) to 1 additional
chance in 1 million (1 x 10-6) that a person will develop cancer.

Noncarcinogenic effects of a single contaminant in a single medium are expressed as the hazard
guotient (HQ), which is the ratio of the estimated intake-derived from the contaminant concentration in a
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given medium-to the contaminant's RfD. The Hazard Index (HI) can be generated by adding the HQs for
all contaminants within a medium or across all media to which a given population may reasonably be
exposed. The HI provides a useful reference point for gauging the potential significance of multiple
contaminant exposures within a single medium or across media. An HI of 1 or less indicates the human
population is not likely to experience adverse health effects.

Table 4 summarizes pathway-specific and cumulative risks calculated for the current land-use scenario.
All risks for pathway-specific exposures under current land-use conditions were below 1 x 10-6--the low end
of USEPA's target risk range. In addition, none of the His for any of the exposure pathways were greater
than 1, indicating adverse noncarcinogenic effects are not likely to result from exposures through any of the
pathways evaluated. Cumulative risks were calculated for multiple pathways where the same receptor could
potentially be exposed via multiple exposure scenarios. Under current land-use conditions, the combined
risks for both caretakers and trespassers were lower than USEPA's risk range for health protectiveness at
Superfund sites (see Table 4). In addition, the combined His for caretakers and trespassers were less than
1 (see Table 4), indicating noncarcinogenic effects are unlikely to occur as a result of combined exposures
through the pathways evaluated.

Table 5 summarizes pathway-specific and cumulative risks calculated for future land-use conditions at
Cluster 1. Under future land-use conditions, the pathways that resulted in potential cancer risks greater
than 1 x 10-6 were ingestion of surficial and confined groundwater by an on-site resident, inhalation of VOCs
from surficial groundwater while showering by an on-site resident, and dermal absorption of chemicals in
surficial and confined aguifer groundwater while bathing by a child resident. However, these risks were
still within USEPA's target risk range of 1 x 10-4 to 1 x 10-6; and His for these pathways were less than 1,
with the exception of one isolated detection of arsenic in a confined groundwater well. Potential cancer
risks associated with the remaining future land-use scenario pathways were below 1 x 10-6, and His were less
than 1.
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Table 4.
Summary of Pathway Specific and Cumulative Risks,
Cluster 1, Current Land-Use Conditions
Exposure pathway
Potential risks to adult
caretakers
Excess upper-
bound lifetime
cancer risk
Hazard Index
Potential risks to
child/teenage trespassers
Excess upper-
bound lifetime
cancer risk
Hazard Index
Incidental ingestion of
surface soil
NA
(4E-03)
NA
< 1 (3E-03)
Incidental ingestion of
Lauderick Creek
sediment
NE
NE
1E-C
NA
Incidental ingestion of
Monks Creek sediment
NE
NE
2E-07
(3E-03)
Incidental ingestion of
Lauderick Creek
surface water
NE
NE
NA
(4E-04)
Dermal contact with
Lauderick Creek
surface water
NE
NE
NA
(1E-03)
Dermal contact with
Monks Creek surface
water
NE
NE
4E-09
(7E-02)
Total
NA
(4E-03)
2E-07
(8E-02)
NE = Not evaluated; pathway not complete
NA = Not applicable; either no chemicals were present for this pathway or chemicals selected lacked
toxicity criteria.
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Table 5.
Summary of Pathway Specific and Cumulative Risks,
Cluster 1, Future Land-Use Conditions

Potential risks to hypothetical future residents
Exposure pathway
Excess upper-bound Hazard Index
lifetime cancer risk

Incidental ingestion of on-site surface soil by 0-30- NA <1 (2E-02)
year-old residents

Ingestion of groundwater by adult resident

Surficial aguifer

Organic chemicals

Group 1 (Wells 2A, 2B, 3A, 6B 8E-06 <1 (1E-01)
7A, 21A, 22A, 29A, 36A)

Group 2 (Wells 33A, 34A) IE-OS <1 (9E-02)

Group 3 (Well 16A) 2E-05 <1 (1E-01)

Inorganic chemicals

Group 6 (Wells ISA, 16A) 1E-04 <1 (5E-01)

Group 7 (Wells 26B, 9A) 7E-05 <1 (3E-01)

Group 8 (Wells 21A, 2A, 2B, 34A) 4E-05 <1 (4E-03)

Group 9 (Well 26B) NA <1 (3E-01)

Group 10 (Well 36A) NA <1 (2E-02)

Group 11 (Wells 22A, 2A) NA <1 (1E-01)

Group 13 (Wells 16A, 18A, 5A) NA <1 (2E-01)
9A)

Confined aguifer

Organic chemicals

Group 4 (Well 1C) 3E-05 <1 (3E-01)

Group 5 (Well 36B) 5E-07 <1 (3E-02)

Inorganic chemicals

Group 13 (Well 36B) 2E-04 <1 (9E-01)
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Exposure pathway
Table 5. (continued)

Potential risks to hypothetical future residents

Excess upper-bound Hazard Index
lifetime cancer risk
Inhalation of volatile organics released from
groundwater while showering by adult residents

Surficial aguifer

Group 1 (Wells 2A, 2B, 3A, 6B, 7A, 2E-06
21A, 2 2 A, 29A, 36A)

Group 2 (Wells 33A, 34A) 5E-07

Confined aguifer

Group 5 (Well 36B) 2E-07

Dermal absorption of chemicals in groundwater while
bathing by child residents

Surficial chemicals

Organic chemicals

Group 1 (Wells 2A, 2B, 3A, 6B, 1E-06
7A, 21A, 22A, 29A, 36A)

Group 2 (Wells 33A, 34A) 4E-07

Group 3 (Well 16A) 8E-07

Inorganic chemicals

Group 6 (Wells ISA, 16A) 1E-07

Group 7 (Wells 26B, 9A) NA

Group 8 (Wells 21A, 2A, 2B, 34A) 4E-06

Group 9 (Well 26B) NA

Group 10 (Well 36A) NA

Group 11 (Wells 22A, 2A) NA

Group 12 (Wells 16A, 18A, 5A, NA
9A)

Confined Aguifer

Organic chemicals

Group 4 (Well 1C) 2E-06
(4E-01)
(3E-01)
NA
(9E-02)

(1E-02)

(3E-02)

(2E-03)

(4E-03)

(7E-03)
(7E-02)
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Table 5. (continued)

Potential risks to hypothetical future residents
Exposure pathway
Excess upper-bound Hazard Index
lifetime cancer risk

Group 5 (Well 36B) 9E-08 <1 (1E-02)

Total Risk - Adult Resident (a) 2E-04 >1 (2E+00)

Total Risk - Child Resident (b) 6E-06 <9E-02

NA = Not applicable; pathway was not evaluated because (1) no chemicals exhibiting
carcinogenic/noncarcinogenic effects were selected as chemicals of potential concern for this
pathway/medium combination, (2) chemicals selected lacked toxicity criteria, or (3) pathway not
complete.
(a) =Total risk to adult resident assumes ingestion and dermal contact with soil and ingestion and
inhalation of groundwater. The groundwater well groupings associated with the highest risks for
organics (Group 4 for ingestion and Group 1 for inhalation) and for inorganics (Group 13 for
ingestion).
(b) = Total risk to child resident assumes ingestion and dermal contact with soil and dermal contact with
groundwater. The groundwater well groupings associated with the highest risks for organics (Group
4) and for inorganics (Group 8) were conservatively used to calculate cumulative risk.
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Under future land-use conditions, multiple pathway risks were calculated for an on-site resident.
Based on assumed exposure to the maximum detected concentration in one well for both organic and
inorganic analytes, the total cancer risk to an on-site resident for incidental ingestion of surface soil and
ingestion and inhalation of contaminants in groundwater was 2 x 10-4. The child resident's cumulative
cancer risk for incidental ingestion of surface soil and dermal contact with groundwater was 6 x 10-6. The
cumulative risk for the adult resident was just above USEPA's target risk range of 1 x 10-4 to 1 x 10-6,
while the cumulative risk for the child resident was within USEPA's target risk range. The HI associated
with the child resident is less than 1, indicating noncarcinogenic effects are not likely to occur to a child
resident as a result of combined exposures through the pathways evaluated. However, the HI for the adult
exceeds 1, which indicates a potential for noncarcinogenic effects.

In addition to the health risks caused by the chemical contaminants in groundwater, a hazard may be
posed by CWM-filled containers and asbestos found in the landfill. Containers filled with CWM present a
human safety hazard if they accidentally rupture or corrode, thereby releasing contaminants to the
environment. Asbestos is an inhalation hazard and has been shown to cause lung cancer.

As in any RA, there is a large degree of uncertainty associated with the estimates of human health
risks. Because an RME case was evaluated in the RA to place a conservative upper bound on the potential
risks, the risks presented in this RA are likely to be overestimated. Consequently, the estimates calculated
for Cluster 1 should not be construed as absolute estimates of risk but rather as conditional estimates based
on a number of assumptions regarding environmental sampling and analysis, exposure parameter estimation, and
toxicological data.

2.6.2. Environmental Risks

An Ecological Risk Assessment (ERA) was conducted as part of the RI to evaluate potential impacts
to both terrestrial and aguatic population or communities if cleanup activities were not performed at
Cluster 1. Risks were characterized by combining estimates or measures of exposure with estimates or
measures of toxicity. Toxicity is characterized by defining the relationship between chemical
concentration and a given ecological effect. Chemical and bioassay data collected as part of the RI and
biological assessment studies being conducted at Cluster 1 were used in conjunction with data from the
scientific literature to characterize exposure, toxicity, and risks.

The ERA focused on chemicals with the greatest potential to impact ecological communities.
Chemicals of potential concern in surface soils include the pesticide 4,4'-DDT,4,4'-DDE, polynuclear
aromatic hydrocarbons (PAHs) [e.g., benzo(b)fluoranthene, benzo(k)fluoranthene, chrysene, fluoranthene,
phenanthrene, and pyrene], other organics (e.g., benzoic acid, di-n-butylphthalate, ethylbenzene, styrene,
toluene, and xylenes), and metals (e.g., beryllium, iron, manganese, nickel, and zinc).

Arsenic, copper, manganese, and nickel were selected as inorganic chemicals of potential concern in
Monks Creek surface water. In Monks Creek sediment, beta-BHC, benzoic acid, 4,4'-ODD, 4,4'-DDE,
methoxychlor, 4-methylphenol, fluoranthene, pyrene, cadmium, cobalt, manganese, and selenium were
identified as chemicals of potential concern. In Lauderick Creek sediment, the PAHs [e.g.,
benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(g,h,i)perylene, benzo(k)fluoranthene,
indeno(1,2,3-cd)pyrene, 2-methyl-naphthalene, chrysene, acenaphthene, anthracene, fluoranthene,
naphthalene, phenanthrene, pyrene], 4,4'-DDT, 4,4'-ODD and 4,4'-DDE, dibenzofuran, 2-methylphenol,
nitrobenzene, and xylenes were selected for evaluation.

Aguatic organisms could potentially be exposed to chemicals in Lauderick Creek and Monks Creek
by direct contact with contaminated water and sediment, by the respiration of chemicals in water and
sediment, and by ingestion of contaminated sediment and food. Terrestrial plants may be exposed to
chemicals of potential concern in soil as a result of direct contact and uptake via the roots. Soil-dwelling
invertebrates may be exposed to chemicals via dermal absorption and via the ingestion of contaminated soils.
Because of their intimate contact with soil and the availability of data, earthworms were used as the
receptor species for evaluating potential impacts to terrestrial invertebrates. Terrestrial vertebrates may
be exposed to chemicals of concern through the ingestion of contaminated food items (e.g., soil dwelling
invertebrates). Shrews were used as the receptor species for evaluating potential impacts to small mammals
because they are insectivorous and thus have a significant potential exposure to chemicals from soil
invertebrates. Birds were not selected for evaluation because they are likely to have less intimate contact
with the soil than small mammals. Birds generally have a larger home range than small mammals and are not
likely to receive as much exposure to the site.

Potential risks to aguatic organisms were calculated by comparing surface water concentrations
(average and RME) of the chemicals of potential concern in Monks Creek with available toxicity reference
values (TRVs) [e.g., Ambient Water Quality Criteria (AWQC), toxicity data for aguatic life]. Sediment
concentrations of the chemicals of potential concern in Lauderick Creek and Monks Creek were compared
with available TRVs [e.g., sediment quality criteria (SQC)] and the results of invertebrate bioassay tests.
-------
Potential risks to terrestrial organisms were evaluated by comparing surface soil concentrations (average and
RME) with derived TRVs. TRVs were derived from available toxicity data.

A comparison of surface water concentrations in Monks Creek with TRVs indicates the calculated
RME for copper exceeds its TRV. However, copper was detected in only 1 of 9 surface water samples
collected, and the average concentration was below the TRV. Therefore, adverse chronic effects to
aguatic life in Monks Creek are not expected. Comparison of sediment concentration data to site-specific
TRVs suggests benthic invertebrates may be at risk for chronic toxicity as a result of exposure to DDT
metabolites in Monks Creek. However, bioassays conducted with Monks Creek sediment and C. tentans
and H. azteca suggest the chronic toxicity potential is low. The sediment bioassay test result should be
weighted more heavily than the predicted potential toxicity resulting from comparison of exposure point
concentrations with TRVs.

Samples from two locations in the sediment from Lauderick Creek showed concentrations of a
number of organic contaminants [anthracene, benzo(a)anthracene, 2-methylnaphthalene, fluorene, pyrene,
2-methylphenol, 4,4'-DDE and 4,4'-ODD] that exceed site-specific TRVs, which indicates benthic
invertebrates in Lauderick Creek may potentially be effected as a result of exposure to these compounds in
sediment. However, this area is outside the Former Nike Site and is not addressed in this document. A
comparison of surface soil concentrations to derived TRVs indicates terrestrial organisms-including
plants, soil invertebrates, and small mammals-are not expected to be adversely affected by exposure to
the potential contaminants of concern because surface soil concentrations were below derived TRVs.

It should be noted there is a large degree of uncertainty associated with the estimation of toxicity
and exposure of ecological receptors. Uncertainty exists in the toxicity data used to develop TRVs for
terrestrial plants, wildlife, and aguatic organisms, in the development of exposure point concentrations, in
the derivation of SQC from AWQC, and in the assumptions regarding bioconcentration of DDT from soil
by earthworms and their consumption by shrews. Therefore, the results of the ERA should not be
construed as absolute conclusions but instead as general indications of potential ecological effects.

2.7 GROUNDWATER REMEDIATION

The Army used the conclusions from the RI, the remedial action objectives (RAOs) listed in the FS,
and applicable or relevant and appropriate reguirements (ARARs) to set cleanup objectives for
groundwater contamination at Cluster 1. The cleanup objectives for groundwater are to prevent human
exposure to on-site contaminated groundwater, to prevent off-site migration of contaminated groundwater,
and to remediate on-site groundwater to the maximum contaminant level (MCL) of 5 • g/L. Actual or
threatened releases of hazardous substances from surficial groundwater at this site, if not addressed by
implementing the response action selected in this ROD, may present an imminent and substantial
endangerment to public health, welfare, or the environment.

2.7.1 Description of Alternatives

2.7.1.1 Alternative 1: No Action

The no-action alternative includes no remedial actions to contain, remove, or treat the contaminant
plume at Cluster 1. Evaluation of the no-action alternative provides a baseline against which no measure
other alternatives. Groundwater monitoring, including annual sampling and analysis for 30 years, will
determine whether contaminant migration is occurring.

The following major ARARs are cited as part of Alternative 1:

Because of the presence of contaminants in the surficial aguifer, federal MCLs [40 Code of Federal
Regulations (CFR) 141, 143], Maryland groundwater guality criteria (COMAR 26.08.02.09), and
Maryland drinking water standards (COMAR 26.04.01) are exceeded. This alternative does not
achieve cleanup to a level that meets these standards. The human health risks present in Sect.
2.6.1 under a future land-use scenario for on-site residents are not reduced, and TCE contamination
in groundwater as high as 299 • g/L can continue.

The costs for Alternative 1 are as follows:

Capital costs: $0
Operations and maintenance (O&M) cost: $12,570/year
Net present worth: $193,232 for 15 years
There is no implementation time reguired for this alternative.

2.7.1.2 Alternative 2: Treatment in Biological Seguencing Batch Reactors
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This alternative involves the extraction of groundwater, treatment in sequencing batch reactors
(SBRs), and discharge of treated water to a tributary of the Bush River. The major components of this
remedial alternative are described below.

Groundwater is removed by extraction wells in accordance with Maryland water appropriation or use
regulations (COMAR 08.05.02), which govern the construction of monitoring wells and the
extraction of groundwater from the subsurface.

The extracted groundwater is treated in an aboveground SBR system that employs microorganisms to
reduce TCE levels in the aguifer to below 5 •g/L to meet federal MCLs. The treatment system will
be designed, operated, and closed in accordance with Maryland standards for chemical, physical, and
biological treatment of hazardous waste (COMAR 26.13.05.18) and in accordance with air guality
requirements for construction and operation of processes that generate potentially hazardous air
emissions (COMAR 26.11.01 and .06). Hazardous sludge that may be generated as a result of the
treatment process will be stored, handled, characterized, and disposed of in accordance with
Maryland hazardous waste management regulations (COMAR 26.13) and likely disposed of off-site,
depending on its characteristics. The specific treatment system configuration and operational
procedures for the SBR will be developed during the design phase.
The treated groundwater is discharged to a tributary of the Bush River. The treatment system will be
designed and implemented in accordance with the substantive requirements of the National Pollutant
Discharge Elimination System (NPDES) program. Long-term groundwater monitoring is performed in
accordance with RCRA closure and postclosure requirements (COMAR 26.13.05.06-.07). Land-use
restrictions are implemented to minimize human exposure to contaminants.

This alternative meets groundwater cleanup objectives by treating the contaminated surficial aquifer
to 5 • g/L TCE, by preventing human exposure through treatment and land-use restrictions, and by
preventing off-site migration of contaminants through groundwater extraction.

The costs for Alternative 2 are as follows:

Capital costs: $1,465,830
O&M cost: $103,763/year
Net present worth: $2,542,890 for 15 years
This alternative is expected to reach the MCL within 15 years.

2.7.1.3 Alternative 3: Treatment by Ultraviolet-catalyzed Oxidation

This alternative involves the extraction of groundwater, treatment by ultraviolet (UV)-catalyzed
oxidation, and discharge of treated water to a tributary of the Bush River. The major components of this
remedial alternative are described below.

Groundwater is removed by extraction wells in accordance with Maryland water appropriation or use
regulations (COMAR 08.05.02) that govern the construction of monitoring wells and the extraction of
groundwater. The extracted groundwater is treated in an aboveground UV-oxidation system that employs
UV irradiation in conjunction with oxidizers such as ozone or peroxide to reduce TCE levels in the
aquifer to below 5 • g/L to meet the federal MCL. The treatment system will be designed, operated,
and closed in accordance with Maryland standards for chemical, physical, and biological treatment of
hazardous waste (COMAR 26.13.05.18) and in accordance with air quality requirements for
construction and operation of processes that generate potentially hazardous air emissions (COMAR
26.11.01 and .06). The specific treatment system configuration and operational procedures will be
developed during the design phase. The treated groundwater is discharged to a tributary of the Bush
River. The treatment system will be designed and implemented in accordance with the substantive
requirements of the NPDES program.

Long-term groundwater monitoring is performed in accordance with RCRA closure and postclosure
requirements (COMAR 26.13.05 . 06-.07) .
Land-use restrictions are implemented to minimize human exposure to contaminants.

This alternative meets groundwater cleanup objectives by treating the contaminated surficial aquifer
to 5 • g/L TCE, by preventing human exposure through exposure treatment and land-use restrictions,
and by preventing off-site migration of contaminants through groundwater extraction.

The costs for Alternative 3 are as follows:

Capital costs: $511,491
O&M cost: $144,991/year
Net present worth: $2,018, 106 for 15 years
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This alternative is expected to reach the MCL within 15 years.

2.7.1.4 Alternative 4: Treatment in Place Using Reductive Dehalogenation

This alternative involves funneling groundwater through permeable subsurface treatment sections,
performing long-term groundwater monitoring, and imposing land-use restrictions on groundwater use
during the remediation period. The major components of this remedial alternative are described below.

This in situ reductive dehalogenation system design consists of a "funnel and gate" system in which
the funnel is a scalable joint sheet pile wall that directs groundwater flow to the gate, which is
filled with an iron-sand mixture that provides a reducing environment capable of abiotic
degradation of TCE. The groundwater is treated until it reaches TCE concentrations below the MCL of
5 • g/L as it flows through the iron and sand mixture. Construction is performed in accordance with
Maryland standards for chemical, physical, and biological treatment of hazardous waste (COMAR
26.13.05.08) and air guality reguirements for construction and operation of processes that generate
potentially hazardous air emissions (COMAR 26.11.01 and .06). All trenching and other construction
activities will be performed in accordance with Occupational Safety and Health Administration
(OSHA) Standards (29 CFR 1926) governing construction safety. The approximately 16,518 cubic yards
of soil excavated during construction will be characterized in accordance with RCRA Subtitle C
Reguirements (40 CFR 261) to determine its hazard characteristics. The excavated material is
expected to be nonhazardous and will be used as backfill material during construction in accordance
with Maryland erosion and sediment control regulations (COMAR 26.09.01). Laboratory
permeability tests and a treatability study are performed before full-scale implementation of this
alternative.

Long-term groundwater monitoring is performed at the site. Monitoring wells are installed
upgradient and downgradient of the treatment sections in accordance with Maryland groundwater
monitoring and protection reguirements (COMAR 26.13.05.06) and regulations governing the
construction of monitoring wells and extraction of groundwater (COMAR 08.05.02) to evaluate the
long-term effectiveness of treatment and to accurately determine whether contaminant migration is
occurring. Sampling would occur annually for a period of 60 years-the estimated duration of the
groundwater treatment process.

Land-use restrictions. Temporary land-use restrictions are implemented to prohibit on-site use of
contaminated groundwater for the duration of the groundwater treatment process (60 years). This
alternative meets groundwater cleanup objectives by treating the contaminated surficial aguifer to
5 • g/L TCE; by preventing human exposure through groundwater treatment and land-use restrictions;
and by preventing off-site migration of contaminants through groundwater extraction and treatment.

The costs for Alternative 4 are as follows:

Capital costs: $3,565,095
O&M cost: $52,860/year
Net present worth: $4,565,698 for 60 years
This alternative is expected to reach the MCL within 60 years.

2.7.1.5 Alternative 5: Treatment by Aboveground Reductive Dehalogenation

This alternative involves:

Extraction of contaminated groundwater as described in Sect. 2.7.1.2. A treatability study is
performed before the alternative is implemented, and pump tests are conducted before final design of
the system. Treatment using aboveground reductive dehalogenation. Reactive media composed of
grindings of metallic iron produce a reducing environment capable of abiotic degradation of TCE.
The treatment system will be designed, operated, and closed in accordance with Maryland standards
for chemical, physical, and biological treatment of hazardous waste (COMAR 26.13.05.18) and with
air guality reguirements for construction and operation of processes that generate potentially
hazardous air emissions (COMAR 26.11.01 and .06). Hazardous sludge that may be generated as a
result of the treatment process will be stored, handled, characterized, and disposed of in
accordance with Maryland hazardous waste management regulations (COMAR 26.13) and likely disposed
of off-site, depending on its characteristics. The specific treatment system configuration and
operational procedures for the reductive dehalogenation system will be developed during the design
phase. Discharge of treated groundwater to a tributary of the Bush River. The treatment system will
be designed and implemented in accordance with the substantive reguirements of the NPDES program.
Long-term groundwater monitoring is performed in accordance with RCRA closure and postclosure
reguirements (COMAR 26.13.05.05.06-.07). Land-use restrictions are implemented to minimize human
-------
exposure to contaminants.

This alternative meets groundwater cleanup objectives by treating the contaminated surficial aguifer
to 5 • g/L TCE, by preventing human exposure through groundwater treatment and land-use
restrictions, and by preventing off-site migration of contaminants through groundwater extraction.

The costs for Alternative 5 are as follows:

Capital costs: $706,901
O&M cost: $83,850/year
Net present worth: $1,737,266 for 15 years
This alternative is expected to reach the MCL within 15 years.

2.7.1.6 Alternative 6: Treatment by Air Stripping

This alternative involves:

Extraction of contaminated groundwater as described in Sect. 2.7.1.2, including a treatability study
and pump test. Air stripping using stripping towers to reduce TCE concentrations in the aguifer to
below the MCL of 5 • g/L by volatilizing the TCE from the groundwater. The treatment system will be
designed, operated, and closed in accordance with Maryland standards for chemical, physical, and
biological treatment of hazardous waste (COMAR 26.13.05.18) and air guality reguirements for
construction and operation of processes that generates potentially hazardous air emissions (COMAR
26.11.01 and .06). Hazardous sludge that may be generated as a result of the treatment process will
be stored, handled, characterized, and disposed of in accordance with Maryland hazardous waste
management regulations (COMAR 26.13) and likely disposed of off-site, depending on its
characteristics. The specific treatment system configuration and operational procedures will be
developed during the design phase. Treatment of effluent gases using granular activated carbon in
accordance with air emissions regulations previously discussed. Contaminated air passes through an
activated carbon adsorption unit if treatment of off-gases is necessary. Spent carbon is picked up
and disposed of by the vendor. Discharge of treated groundwater to a tributary of the Bush River.
The treatment system will be designed and implemented in accordance with the substantive
reguirements of the NPDES program. Long-term groundwater monitoring is performed in accordance with
RCRA closure and postclosure reguirements (COMAR 26.13.05.06-.07). Land-use restrictions to
minimize human exposure to contaminants.

The costs for Alternative 6 are as follows:

Capital Costs: $1,143,104
O&M cost: $81,467/year
Net present worth: $1,988,708 for 15 years.
This alternative is expected to reach the MCL within 15 years.

2.7.2 Summary of the Comparative Analysis of Alternatives

As reguired by CERCLA, the remedial alternatives listed above were evaluated using nine criteria
specific by USEPA (see Table 6). This section and Table 7 summarizes the relative performance of each
of the landfill remediation alternatives with respect to seven of the nine CERCLA evaluation criteria. The
last two evaluation criteria, state and community acceptance, are evaluated in Section 2.7.2.3.
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Table 6.
USEPA Evaluation Criteria for
Remediation (Cleanup) Alternatives
1. Overall Protection of Human Health
and the Environmental addresses
whether a cleanup method provides
adequate protection to human health and

the environment and describes how risks
presented by each pathway are
eliminated, reduced, or controlled
through treatment, engineering controls,
or institutional controls.

2. Compliance with ARARs addresses
whether a cleanup method will meet all
applicable or relevant and appropriate
requirements (federal and state
environmental requirements).

3. Long-Term Effectiveness and
Permanence is the ability of a cleanup
method to maintain reliable protection of
human health and the environment over
time after the action is completed.

4. Reduction of Toxicity, Mobility, or
Volume Through Treatment is the
anticipated ability of a cleanup method to
reduce the toxicity, mobility, or volume
of the hazardous substances present at
the site through treatment.
5. Short-Term Effectiveness addresses the
period of time needed to complete the
cleanup and any adverse impacts on
human health and the environment that

may occur during the construction and
operation period.

6. Implementability is the technical and
administrative feasibility of a cleanup
method, including the availability of
materials and services required by the
method.

7. Cost includes the estimated capital and
operation and maintenance costs of each
cleanup method.

8. State Acceptance indicates whether the
State of Maryland agrees with the
preferred cleanup method.

9. Community Acceptance indicates
whether concerns are addresses by the
cleanup method and whether the
community has a preference for a
cleanup method. Public comment is an
important part of the final decision.
This ROD represents APG's request to
the community to provide comments on
the proposed cleanup.
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Remedial
alternativ
Compliance with
ARARs
$4,800
No construction, equipment, O&M
storage, or disposal needs. $12,570/year
environment
8 to 13 years are required to
reduce all TCE contamination volume.
below MCL. Lonq-term O&M
is hiqh.
toxicity, mobility, and
Process is
destructive and
nonreversible. Contaminated
and materials are readily Capital
Minor short term available. Presence of CWM- O&M
increase in noise and filled containers could delay $103,763/year
dust. implementation. Proven NPW $2,542,890
sludqe may be qenerated. Technoloqy.
toxicity, mobility, and and materials are readily Capital
Minor short-term available. Presence of CWM- $511,491
Approximately 60 years are
required to reduce all TCE
contamination below MCL.
Lonq-term O&M is low.
Extensive excavation Required labor, equipment,
Permanent reduction of required, moderate and materials are readily
toxicity, mobility, and increase in noise and available. Presence of CWM- Capital
volume, mobility, and dust. Greater potential filled containers could delay
destructive, nonreversible, for workers to contact implementation. Most O&M
and no hazardous byproducts qroundwater and previous studies have been $52,860/year
are expected. CWM-filled bench-scale; may be more
difficult to implement.
containers.
Compliance with
ARARs
Reduction of Toxicity, Short-Term
Mobility, and Volume Effectiveness Implementability
8 to 13 years are required to toxicity, mobility, and
reduce all TCE contamination volume. Process is
below MCL. Lonq-term O&M destructive nonreversible and dust.
is hiqh. no hazardous byproducts are
expected.
Permanent reduction of Required labor, equipment,
Minor short-term and materials are available.
increase in noise and Presence of CWM-filled
containers could delay O&M
implementation. Proven at the $83,850/year
bench scale level. NPW $1,737,266
With Gas Treatment
Alternative 6--
air strippinq
mobility. Process is Minor short-term
nondestructive. Contaminant
8 to 13 years are required to
reduce all TCE contamination
$1,143,104
below MCL. Lonq-term O&M is trans ferred to atmosphere
is hiqh. or qas treatment unit.
available. Presence of CWM- Capital
increase in noise and filled containers could delay
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Overall protection of human health and the environment. The five treatment alternatives involve
groundwater treatment and provide adequate protection of human health and the environment by reducing TCE
concentrations to below the MCL of 5 • g/L. Because contaminant concentrations will be reduced through
treatment, the discharge of treated groundwater to a tributary of Bush River is not expected to have any
adverse environmental impacts. Alternative 1, no action, provides no protection of human health and the
environment, even though monitoring determines if the TCE plume is approaching the site boundary or Monks
Creek. Achievement of ARARs All five treatment alternatives comply with all ARARs including reducing TCE
concentrations below the MCL of 5 • g/L. Alternative 1 does not comply with ARARs.

2.7.2.2 Primary Balancing Criteria

Long-term effectiveness Alternatives 2, 3, 5 and 6 (SBRs, UV-oxidation, aboveground reductive alogenation,
and air stripping, respectively) provide relatively similar high levels of long-term effectiveness and
permanence. Alternative 4 (in situ reductive dehalogenation) requires considerably more time than the other
treatment alternatives to achieve the same level of remediation. Alternative 1 (no action) does not provide
long-term effectiveness and permanence. Reduction in toxicity, mobility, or volume of contaminants
Alternatives 2 through 5 (SBRs, UV-oxidation, in situ reductive dehalogenation, and aboveground reductive
dehalogenation, respectively) reduce the contaminant toxicity, mobility, and volume in a relatively similar
manner by a magnitude assumed to be comparable to the destruction of the contaminant. Alternative 2 and 6
(SBRs and air stripping, respectively) result in hazardous byproducts (sludge or carbon filters). In
addition, Alternative 6 (air stripping) is a nondestructive technology (TCE is not destroyed but merely
transferred to another medium). Alternative 1 does not reduce the toxicity, mobility, or volume of
contaminated groundwater. Short-term effectiveness Alternative 1 is highly effective in the short term
because public access to Cluster 1 is currently restricted. Alternatives 2 through 6 involve extensive
construction activities that may pose some short-term risks to workers, the community, and the environment
through dust generation, exposure to potentially contaminated soil and groundwater during construction, and
potential encounters with UXO. These risks would be mitigated by using engineering controls and personal
protective equipment during construction activities. Alternative 4 (in situ reductive dehalogenation) may
pose the greatest short-term risk because of the increased potential for workers
to contact contaminated groundwater and the extensive excavation that would be required to install a
slurry/treatment wall around the plume. The extensive excavation may also increase the likelihood of
accidental UXO detonation. Alternatives 2, 3, 5, and 6 are expected to reduce TCE concentrations
below the MCL within 15 years, while Alternative 4 (in situ reductive dehalogenation) may require
60 years, resulting in lower short-term effectiveness. Implementability Alternative 1 (no action) is easily
implementable because it requires minimal construction, no equipment, and minimal handling of contaminated
materials. Alternatives 2, 3, and 6 (SBRs, UV-oxidation, and air stripping, respectively) are relatively
easy to implement because the required labor, equipment, and materials are readily available and because they
are proven technologies commonly used to treat contaminated water. As with all the treatment alternatives,
UXO presence may delay implementation. In addition, air emission permits may be required for Alternatives 2,
3, and 6. Alternative 5 (aboveground reductive dehalogenation) is expected to be moderately easy to
implement. The required labor, equipment, and materials are readily available.

However, this alternative has not been demonstrated on a full-scale basis at similar sites, so unforeseen
implementation difficulties may arise. This possibility is believed to be offset by the advantage gained by
demonstrating an innovative technology. As with the other treatment alternatives, UXO presence may delay
implementation, and an air emissions permit may be required. Alternative 4 (in situ reductive dehalogenation)
is expected to be moderately difficult to implement. Although the labor, equipment, and materials are readily
available, the construction of a slurry wall around the entire plume or plumes will be complicated by
shoring, dewatering of the trench, and the presence of UXO. In addition, this alternative has not been
employed on a full-scale basis at other similar sites, so unforeseen implementation difficulties may be
encountered. Cost The estimated capital, O&M, and net present worth costs for each groundwater remedial
alternative are summarized in Table 7.

2.7.2.3 Modifying Criteria

State Acceptance MDE has been involved in the selection of the alternatives for groundwater cleanup at
Cluster 1 and in identifying cleanup objectives for groundwater (concentrations of TCE below the MCL of 5
• g/L) . In addition, the State of Maryland is satisfied that the appropriate remedial action process was
followed in evaluating remedial action alternatives for the groundwater at Cluster 1 and concurs with the
selected remedy. Public Acceptance APG solicited input from the public on the development of alternatives and
on the alternatives identified in the proposed plan. The public is in agreement with the cleanup objectives,
and most of the commenters were in agreement with the preferred alternative. Several members of the public
preferred a different treatment system, such as air stripping, for cleanup of the groundwater. During the
comment period, APG provided these commenters with additional information regarding their concerns. It
appears the additional information satisfied their concerns A detailed summary of comments and APG's
responses are presented in section 3.0.
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2.7.3 Selected Remedy

The selected remedy to clean up the groundwater contamination at Cluster 1 is Alternative 5,
aboveground reductive dehalogenation, using a groundwater cleanup objective of 5 • g/L for TCE, based on
ARARs. Alternative 5 is highly protective of human health and the environment; complies with all ARARs; has
a high level of long-term effectiveness and permanence; reduces the toxicity, mobility, and volume of
contamination through treatment; has a high level of short-term effectiveness; is expected to be easily
implementable; and is relatively cost-effective. Because the TCE plume is not an immediate threat to human
health or the environment, this alternative presents a unigue and ideal opportunity to evaluate an
innovative technology that has already been shown to effectively treat site groundwater in bench-scale
testing. There are no negative impacts to human health or the environment by employing such an innovative
technology. Alternative 5 will contain the plume on-site (by groundwater extraction) and will provide
treatment to reduce TCE levels to below the MCL of 5 • g/L.

The major components of the selected remedy include:

Extraction of contaminated groundwater using extraction wells to include an artificial cone of
depression within the water table and to remove contaminated groundwater from the aguifer. The
well characteristics are based on groundwater modeling. Pump tests are conducted before final
design of the system to determine/confirm the transmissivity, pumping rate, hydraulic conductivity,
and cone of influence of the recovery wells. A pilot-scale treatability study is performed before
implementation of the alternative.
Treatment using aboveground reductive dehalogenation vessels, which contain reactive media
composed of metallic iron filings. The readily oxidizable medium produces a reducing environment
capable of abiotic degradation of TCE.
Discharge of treated groundwater to a tributary of Bush River. Sampling will be conducted before
and after discharge to ensure that the discharge is not causing an exceedence of Ambient Water
Quality Criteria.
Long-term groundwater monitoring including annual sampling for 15 years.
Land-use restrictions to prohibit the on-site use of groundwater.
The costs for Alternative 5 are summarized in Table 8.

The goal of this remedial action is to restore groundwater to its beneficial use, which is, at this
site, as a potential drinking water source. Based on information obtained during the remedial investigation
and on a careful analysis of all remedial alternatives, it is believed the selected remedy will achieve this
goal. It may become apparent, during implementation or operation of the groundwater extraction system and its
modifications, that contaminant levels have ceased to decline and are remaining constant at levels higher
than the remediation goal over some portion of the contaminated plume. In such a case, the system
performance standards and/or the remedy may be reevaluated.

The selected remedy will include groundwater extraction for an estimated period of 15 years, during
which the system's performance will be carefully monitored on a regular basis and adjusted as warranted
by the performance data collected during operation. Modifications may include any or all of the following:

Cessation of pumping at individual wells where cleanup goals have been attained.
Alternating pumping at wells to eliminate stagnation points.
Pulse pumping to allow aguifer eguilibration and to allow adsorbed contaminants to partition into
groundwater. Installation of additional extraction wells to facilitate or accelerate cleanup of the
contaminant plume.

At those wells where pumping has ceased, the aguifer will be monitored every 5 years following
discontinuation of groundwater extraction to ensure cleanup goals continue to be maintained.

The estimated net present worth cost of Alternative 5 is $1,737,266. The estimated time for
remediation is 15 years.

2.7.X Performance Standards

The contaminants plume of TCE will be contained and treated until the MCL of 5 ug/L is attained
within the Former Nike Site and areas affected by this TCE plume. Groundwater monitoring will be
conducted to ensure the plume is not migrating and that levels of TCE are being reduced to 5 ug/L.
Discharge of the treated water will meet the substantive reguirements of the NPDES Permit program.

2.7.4 Statutory Determinations

The selected remedy discussed in Sect.2.7.3 satisfies the reguirements under Sect.121 of CERCLA to:
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Protect human health and the environment.
Comply with ARARs.
Be cost-effective.
Use permanent solutions and alternative treatment technologies or resource recovery technologies to
the maximum extent practicable.
Satisfy the preference for treatment as a principal element.

2.7.4.1 Protection of Human Health and the Environment

The selected remedy, Alternative 5, will reduce risks to future users of Cluster 1 by treating the
groundwater via extraction, followed by treatment using aboveground reductive dehalogenation then
discharge of the treated groundwater to a tributary of the Bush River. After groundwater is treated, no
adverse health effects are anticipated if humans, animals, or vegetation are exposed to the treated
groundwater. Groundwater extraction and treatment are expected to reach the MCL of 5 • g/L TCE within
15 years, which is protective of human health and the environment. Temporary land-use restrictions will
minimize the risks to human health and the environment until the MCL is reached. Groundwater extraction
prevents the off-site migration of contaminants and the potential discharge of groundwater to Monks Creek by
creating a hydraulic gradient in the direction of the pumping wells. No unacceptable short-term risks or
cross-media impacts will be caused by implementing Alternative 5 because UXO clearance will be performed
before excavation or drilling begin. During remediation, short-term increases in noise and dust are not
expected to affect adjacent communities; remediation workers will wear adeguate personal protective
eguipment.

2.7.4.2 Compliance with ARARs

The selected remedy will comply with all chemical-, location-, and action-specific ARARs. Through
the use of a reductive dehalogenation treatment system with appropriate engineering controls to minimize
release of pollutants to air, land, or water, the remedy will achieve the ARARs listed below.

Chemical-specific ARARs

Maryland standards applicable to generators of hazardous waste (COMAR 26.13.03), which
apply to the generation of potentially contaminated spent media from the reductive
dehalogenation unit (applicable).

Maryland regulations for groundwater monitoring and protection (COMAR 26.13.05.06), which
apply to groundwater monitoring and groundwater guality criteria (applicable).

Maryland NPDES regulations (COMAR 26.08.04) apply to treated effluent discharged to surface
water of the state (applicable).

Maryland surface water guality criteria (COMAR 26.08.02.03) may apply to treated effluent
discharged to surface water (relevant and appropriate).

Maryland drinking water guality standards (COMAR 26.04.01) apply to potable groundwater
(relevant and appropriate).

Maryland air guality regulations (COMAR 26.11.01-26.11.02) apply to general or toxic process
emissions and construction activities that generate particulates (applicable).

Location-specific ARARs

None.

Action-specific ARARs

Maryland standards applicable to tanks and containers (COMAR 26.13.05.09-.10) such as may
be sued to temporarily store groundwater before treatment/disposal (applicable).

Maryland transportation and disposal standards (26.13.04) which apply to off-site shipment of
potentially contaminated spent reductive dehalogenation media (applicable).

Maryland landfill standards (COMAR 26.13.05.14) apply to disposal of potentially contaminated
spent reductive dehalogenation media (applicable).

Maryland chemical, physical, and biological treatment standards (COMAR 26.13.05.18) apply to
treatment systems such as the aboveground reductive dehalogenation system (applicable).
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Federal standards for miscellaneous units (40 CFR 264 Subpart X) may apply to any UXO
encountered during construction activities (relevant and appropriate).

Federal Fish and Wildlife Coordination Act applies to the conservation of wildlife resources
(such as bald eagle) that may nest in the Edgewood area (applicable).

Maryland nontidal wetlands regulations (COMAR 08.05.04) apply to any actions, such as
groundwater extraction, that may affect wetlands near Cluster 1 (applicable).

Maryland water appropriation or use regulations (COMAR 08.05.02) apply to groundwater
extraction (applicable).

Maryland regulations for well drillers (COMAR 26.05) apply to groundwater monitoring and
extraction well construction (applicable).

2.7.4.3 Cost-Effectiveness

The selected remedy is cost-effective because it has been determined to provide overall effectiveness
proportional to its cost (the net present worth is $1,737,266). Of the five action alternatives, the
selected remedy is more cost-effective than the other alternatives. This technology is further recommended
because of the destructive nature of the technology and for the advancement of this innovative technology
during a full-scale application of this system at a hazardous waste site. USEPA and Department of Defense
guidance encourages implementation of innovative technologies at federal facilities.

2.7.4.4 Utilization of Permanent Solutions and Alternative Treatment Technologies to the
Maximum Extent Practicable

The selected remedy, Alternative 5, is a permanent solution that uses alternative treatment
technologies to the maximum extent practicable and provides the best balance of tradeoffs among the
alternatives. Alternative 1 fails to meet several criteria and thus appears to be unacceptable. The
remaining five treatment alternatives meet the threshold criteria and are comparable in terms of long-term
effectiveness, and permanence; reduction in toxicity, mobility and volume of contaminants; and short-term
effectiveness. They differ in terms of implementability and cost. Alternatives 2 and 4 are the most costly.
Alternative 6, while least costly, is a nondestructive technology. Unlike the other alternatives, the
selected remedy uses an innovative technology but requires treatability testing to determine its
effectiveness before implementation. There will be no negative impacts to human health or the environment
from using an innovative technology.

The support of the state and community in the evaluation process and the selection of Alternative 5
further justify its selection.

2.7.4.5 Preference for Treatment as a Principal Element

The statutory preference for treatment is satisfied by using aboveground reductive dehalogenation to
treat TCE-contaminated groundwater at Cluster 1.

2.8 LANDFILL REMEDIATION

The Army set cleanup objectives for the launch Southwest Landfill by using the conclusions from the
RI, and RAOs listed in the FS, and ARARs.

Although the Launch Southwest Landfill was reportedly used for the disposal of construction debris,
approximately 10 empty 55-gal drums were encountered there. It is possible that other wastes were
disposed of at the landfill. These wastes could include currently intact containers of potential
contaminants that may be released in the future. Therefore, the cleanup objectives for the landfill are to
prevent the contamination of groundwater or surface water by any potential contaminants of concern that may
be present in the landfill and to minimize the potential for human contact with the water.

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

2.8.1 Description of Alternatives

2.8.1.1 Alternative 1: No Action.

The no-action alternative involves no remedial action. No efforts are made to contain or remove the
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landfill contents. However, long-term monitoring will be conducted. Evaluation of the no-action
alternative provides a baseline against which to measure other alternatives.

With respect to ARARs, RCRA reguirements for a general closure (COMAR 26.13.05.07) and
closure of a landfill (COMAR 26.13.05.14) are not met because controls to reduce contaminated runoff
and to protect human health and the environment are not implemented. In addition, long-term liguid or
precipitation migration through the closed landfill are not minimized. However, the reguired groundwater
monitoring is performed through the installation of additional monitoring wells and annual groundwater
sampling and analysis. This alternative does not achieve the protection of human health and the
environment within the guidelines of the NCP. The safety risks presented in Sect. 2.6.1 for on-site
residents are not reduced.

The costs for Alternative 1 are as follows:

Capital costs: $51,500
O&M cost: $4,100
Net present worth: $94,058 for 15 years
This alternative is expected to reguire 7 months to implement.

2.8.1.2 Alternative 2: Installation of a Composite Cap

This alternative includes the following:

Clearance of the entire landfill site for UXO before and during excavation; Technical Escort Unit
(TEU) will be notified of and responsible for the disposal of any UXO identified on-site in
accordance with ARMY regulations.
Performance of site grading, sediment and erosion control, and installation of a geonet to convey
landfill gases to a venting system, if reguired.
Installation of a capping system in accordance with USEPA guidance for the closure of a hazardous
waste landfill.
Maintenance and repair operations as needed (e.g., cutting vegetation, regrading, revegetating).
Long-term groundwater monitoring in accordance with RCRA closure and postclosure reguirements
(COMAR 26.13.05.06-.07).
Future land-use restrictions prohibiting construction on the landfill cap or any activities that
might compromise the integrity of the landfill cap.
Installation of a perimeter chain link fence.

This alternative meets the cleanup objectives for the landfill. It prevents contamination of
groundwater or surface water and minimizes the potential for human contact with the waste by isolating the
source with an impermeable cap to prevent infiltration of liguids; this also minimizes contaminant transport
to groundwater or surface water.

The costs for Alternative 2 are as follows:

Capital costs: $1,041,132
O&M cost: $25,860/year
Net present worth: $1,438,665 for 30 years
This alternative is expected to reguire 12 to 24 months to implement.

2.8.1.3 Alternative 3: Conventional Excavation of Landfill Contents in an Armored, Filtered-Air
Shelter and Off-site Disposal of Excavated Waste

This alternative involves:

Clearance of the entire landfill site for UXO before and during excavation with TEU notified of, and
responsible for, the disposal of any UXO identified on-site in accordance with Army regulations.
Conventional excavation within an armored, filtered-air shelter of the entire volume of waste in the
landfill (estimated 18,538 cubic yards of material) in accordance with OSHA construction safety
reguirements (29 CFR 1926) and Maryland erosion and sediment control regulation (COMAR 26.09.01).
Segregation of waste into soil, debris, and rubble fractions.
Off-site disposal of excavated waste fractions in accordance with Maryland Solid Waste Regulations
(COMAR 26.04.07) and Maryland Hazardous Waste Regulations (COMAR 26.13) governing storage,
transport, characterization, and disposal of hazardous waste. Disposal location will depend on
whether the waste is hazardous or nonhazardous.
Backfill, compaction, seeding, and mulching of landfill area.
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Table 8

COST ESTIMATE
GROUNDWATER ALTERNATIVE 5

Groundwater Extraction with Vertical Well Manifolds;
Treatment by Above Ground Reductive Dehalogenation;
Discharge of Treated Water to Surface Water;
Long Term Groundwater Monitoring; Land Use Restrictions
Cluster 1, Aberdeen Proving Ground

CAPITAL COSTS
Item
Rate ($)
Quantity
Unit Cost ($)
Site Preparation
- Site clearing, grubbing, hauling and disposal
- UXO clearance (10-hour day)(a)
Site Preparation Subtotal

Groundwater Extraction System
- Vertical Well Installation (b) (c)
Includes labor, materials, well development, containerization of cuttings/fluids
- Disposal of Cuttings (d)
- Transportation/Disposal of Cuttings (e)
- Soil Sample collection/ TCLP chemical profiling of soil cuttings (f)
- Baker Tanks (3) 6,500 gallon (g) (h)
- Tank Delivery/Pickup (3 tanks) (h)
- Water Samples (Full Suite TCL) (f)
- UXO Support (10-hour day)(a)
- Field installation oversight (labor and materials - 3 sites) (i)
Groundwater Extraction System Subtotal
3825 /acre
1350 /day
180 /foot

35 /ton
100 /ton
1,200 /sample
600 /tank/mo.
800 /trip
1,200 /sample
1,350 /day
640 /day
Groundwater Conveyance System
- IHp Submersible pumps (7), piping; sensors; pitless adapters - installed (j) 1,350 /well
- ALT.l 160 psi, 2"/6" Dual-wall piping/connectors, installed (k)(1) 29 /If
- ALT.l Trenching/backfilling (12" W by 36" D; includes mob/demob.) (m) 1.59 /If
Electrical, installed (15% of other conveyance system cost)
4" PVC treatment discharge piping/connectors, installed (m)
Trenching/backfilling (12" W by 36" D) (m)
Rip-rap (18" thickness), installed (m)
Installation oversight (i)
UXO support (8-hour day) (a)
Groundwater Conveyance System Subtotal
(i)
16.34 /If
0.59 /If
56 /sy
840 /day
940 /day
0.09
2
310
3.5
3.5
3
3
2
3
3
21
acre
days
foot
ton
ton
sample
tank
trips
samples
days
days
344
2,390
55,800
123
350
3, 600
1, 600
1,600
3,600
4,050
17,640
2,734
7 well 9,450
600 If 17,400
600 If 954

5,489
150 If 2,450
150 If 89
3 sy 168
5 days 4,200
2 days 1,880
42,079
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This alternative meets the cleanup objectives for the landfill of preventing contamination of
groundwater or surface water and minimizing the potential for human contact with the waste by removing
the source from the site.

The costs for Alternative 3 are as follows:

Capital costs: $9,787,633 (excavated waste is considered hazardous)
$3,954,862 (excavated waste is considered nonhazardous)
O&M cost: $0/year
Net present worth: (egual to capital costs)
This alternative is expected to reguire 18 to 24 months to implement.

2.8.1.4 Alternative 4: Telerobotic Excavation of Landfill Contents in an Armored, Filtered-Air
Shelter and Off-site Disposal of Excavated Waste

This alternative involves:

Clearance of the entire landfill site for UXO before and during excavation, with TEU notified of,
and responsible for, the disposal of any UXO identified on-site in accordance with Army
regulations. Telerobotic excavation of the entire volume of waste in the landfill (estimated 18.538
cubic yards of material) within an armored, filtered-air shelter to provide additional safety and
to reduce the likelihood of a release to the environment in the unlikely event of accidental
detonation of UXO. The shelter will be tested after assembly to determine if chemical agents could
leak in the event of accidental detonation of chemical agent UXO. Real-time are monitoring for
chemical agents may be used to protect workers and nearby residents. This work is performed in
accordance with OSHA construction safety reguirements (29 CFR 1926) and Maryland erosion and
sediment control regulations (COMAR 26.09.01). Segregation of waster into soil, debris, and rubble
fractions. Off-site disposal of excavated waste fractions in accordance with Maryland solid waste
regulations (COMAR 26.04.07) and Maryland hazardous waste regulations (COMAR 26.13) governing
storage, transport, characterization, and disposal of hazardous waste. Disposal location will
depend on whether the waste is hazardous or nonhazardous. Backfill, compaction, seeding, and
mulching of landfill area.

This alternative meets the cleanup objectives for the landfill of preventing contamination of
groundwater or surface water and minimizing the potential for human contact with the waste by removing
the source from the site.

The costs for Alternative 4 are as follows:

Capital costs: $9,662,333 (excavated waste is considered hazardous)
$3,829,562 (excavated waste is considered nonhazardous)
O&M cost: $0/year
Net present worth: (egual to capital costs).

This alternative is expected to reguire 18 to 24 months to implement.

2.8.2 Summary of the Comparative Analysis of Landfill Cleanup Alternatives

As reguired by CERCLA, remedial alternatives listed above were evaluated using nine criteria
specified by USEPA (see Table 6). This section and Table 6 summarizes the relative performance of each
of the landfill cleanup alternatives with respect to the nine CERCLA evaluation criteria.

2.8.2.1 Threshold Criteria

Overall protection of human health and the environment.
Alternative 2 (composite cap) provides a high level of overall protection to human health and the
environment by preventing transport of, and human contact with, contaminants through the containment of
wastes beneath an impermeable cap. In addition, the disturbance of the wastes during construction is
minimized, thereby minimizing short-term risks to human health and the environment. Alternatives 3 and
4 (conventional excavation and telerobotic excavation, respectively) also have high levels of overall
protection to human health and the environment because the waste is removed from the site. However, there
may be significant short-term risks to human health and the environment during transport of the wastes.
Alternative 1 (no action) does not provide overall protection of human health and the environment.

Achievement of ARARs. Alternatives 2, 3, and 4 comply with all ARARs. Alternative 1 (no action)
does not comply with ARARs.
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Primary Balancing Criteria

Long-term effectiveness Alternatives 3 and 4 may provide greater long-term effectiveness and
permanence than Alternative 2 because the landfill contents are permanently removed from the site thereby
eliminating any potential for leaching of contaminants into groundwater or surface water. However, if the cap
is properly maintained, Alternative 2 can also provide a high level of long-term effectiveness. Alternatives
1 (no action) provides no long-term effectiveness. Reduction in toxicity, mobility, or volume of contaminants
Alternatives 3 and 4 result in a permanent reduction in the toxicity, mobility, and volume of the waste
because it is excavated and removed from the site. Alternative 2 reduces the mobility of contaminants in the
landfill but does not reduce their toxicity or volume. Alternative 1 (no action) provides no reduction in
toxicity, mobility, or volume of contaminants.
Short-term effectiveness Alternatives 2, 3, and 4 involve construction activities that can generate
short-term impacts from dust, soil erosion, or accidental detonation of UXO. However, Alternative 2
(composite cap) provides fewer short-term impacts than Alternatives 3 and 4 because the waste is not
disturbed. Short-term impacts may be greater for Alternatives 3 and 4 because of the extensive excavation
conducted, the greater potential for encountering UXO, and the need to transport wastes. However, the use of
an armored, filtered-air shelter during excavation can mitigate some of these risks. Alternative 1 (no
action) provides no short-term effectiveness.
Implementability Alternative 2 (composite cap) is expected to be relatively easy to implement because
the labor, equipment, and materials are readily available and because capping is a well-demonstrated
technology at similar sites. Alternatives 3 and 4 (conventional excavation and telerobotic excavation,
respectively) are expected to be moderately difficult to implement because the use of an armored,
filtered-air shelter or telerobotic excavation is not well demonstrated at similar sites and may result in
encountering unforeseen implementation difficulties. In addition, the excavation and transport of waste
materials is more difficult than the construction of a cap. Alternative 1 (no action) requires no effort to
implement.
Cost The estimated capital, O&M, and net present worth cost for each landfill remedial alternative
are summarized in Table 9.

2.8.2.3 Modifying Criteria

State Acceptance MDE took part in the selection of the remediation alternatives for landfill cleanup at
Cluster 1 and in identification of cleanup objectives (preventing accidental detonation of UXO and leakage
of contaminants to the environment). In addition, the State of Maryland is satisfied that the
appropriate remedial action process was followed in evaluating remedial action alternatives for the landfill
at Cluster 1 and concurs with the selected remedy. Public Acceptance APG solicited input from the public on
the development of alternatives and on the alternatives identified in the proposed plan. The public is in
agreement with the cleanup objectives, and most of the commenters were in agreement with the preferred
alternative. One community group requested additional site characterization for the landfill and other
members of the public preferred the landfill be excavated. During the comment period, APG provided those
commenters with additional information on their concerns. It appears the additional information satisfied
their concerns. A detailed summary of concerns and APG's responses are contained in section 3.0.

2.8.3 Selected Remedy

The selected remedy for the cleanup of the Southwest Launch Landfill is Alternative 2, composite cap.
This alternative is highly protective of human health and the environment, complies with all ARARs, has a
high level of long-term effectiveness and permanence if the cap is properly maintained, reduces the
mobility of contaminants through containment, has a high level of short-term effectiveness, is expected to
be easy to implement, and is relatively cost-effective. Alternative 2 involves:

Site preparation: clearing the area of trees, vegetation, root mat, and debris, and stripping an
average of 6 in. of soil. Debris is disposed of at an off-site landfill or wood chipping facility in
accordance with Maryland solid waste regulations (COMAR 26.04.07) governing disposal of debris. This work is
performed in accordance with Maryland erosion and sediment control regulations (COMAR 26.09.01) and OSHA
construction safety guidelines (29 CFR 1926). Clearance of the entire landfill site for UXO, TEU will be
notified of, and responsible for, the disposal of any UXO identified on-site in accordance with Army
regulations. Stabilization of seep areas or soft, loose soil with geogrid to support the cap.
Performance of site grading, sediment and erosion control, and installation of a geonet to convey
landfill gases to a venting system, if required. Installation of a capping system in accordance with USEPA
guidance for the closure of a hazardous waste landfill, including:
- A geosynthetic clay layer substituted for the typical compacted 2-ft-thick clay layer of low
permeability.
- A layer of synthetic geomembrane.
- A drainage layer overlain by filter fabric to prevent clogging by fines.
- A final earthen cover with a 3% minimum slope and vegetative stabilization.
-------
Inspection of cap system at regular intervals to check for signs of erosion, settlement, or invasion
by deep-rooted vegetation and burrowing animals in accordance with Maryland hazardous waste management
regulations governing closure and postclosure care (COMAR 26.13.05.07). Maintenance and repair operations as
needed (e.g., cutting vegetation, regrading, revegetating). Installation of groundwater monitoring wells in
accordance with Maryland water appropriation and use regulations (COMAR 08.05.02) governing well construction
and groundwater extraction and Maryland hazardous waste regulation (COMAR 26.13.05.06) governing closure
reguirements to detect off-site contaminant migration, with sampling and analysis conducted annually. Future
land-use restrictions prohibiting construction on the landfill cap or activities that compromise the
integrity of the landfill cap.

Installation of a perimeter chain link fence.

This selected remedy meets the landfill cleanup objectives by containing the waste to prevent
migration of contaminants to the environment and to prevent human contact with waste materials.

The costs for Alternative 2 are summarized in Table 10.
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Table 9.
Comparison of Landfill Remedial Action Alternatives

Evaluation criteria
Remedial alternative Overall protection Compliance with Long-term Reduction of toxicity, Short-Term
to human health and ARARs effectiveness and permanence mobility, and volume effectiveness Implementability Cost
the environment
the environment

Does
not provide adequate No impacts on community or No construction, No associated No Action protection. RAOs are not Not met.
toxicity, worker health or the equipment, storage, or capital or O&M met.
mobility, and volume. environment.disposal needs. costs.

Significantly reduces risks as a
Landfill Alternative Complies with all resultofleachingof contaminating Reduces contaminated Required labor, materials,
Capital $1,041,132;
2--RCRA cap High level of protection. ARARs. into groundwater or surface mobility but not Minor, short-term increases and equipment are readily O&M $25,860/year;
runoff of contaminant volume or contaminated volume or noise and dust. available.
NPW $1,438,665.
water. O&M is required. toxicity.
Mor
ore effective because the Permanent reduction in innoise and dust. Potential for Required labor and

Complies with all source of potential contamination toxicity, mobility, and accidental detonation of UXO. equipment are readily
nonnazar clous
-conventional High level of protection. ARARs. is removed. No O&M is volume. Greater risk because of available.
capital $3,954,862.
excavation required. disturbance of waste.
No O&M.

Moderate short-term increase
Required labor and
Landfill Alternative More effective because the Permanent reduction in in dust. Potential for equipment are available.
Hazardous capital
1 ' High level of protection. Complies with all source of potential contamination toxicity, mobility, and accidental UXO detonations. Useofspecialized $9,662,333;
ARARs. is removed. No O&M is volume. Greater risk because of equipment
nonhazardous
required. disturbance of waste.
implemenation. capi'
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2.8.X Performance Standards

The landfill cap will prevent migration of contaminants from the waste to the groundwater. The cap
will have a permability of 1X10-7 cm/s. The cap and groundwater will be monitored in accordance with
an approved Operation and Maintenance Plan. A 5 year review will be conducted in accordance with Section
121(c), CERCIA Cleanup Cleanup Standards, to ascertain if the cap has maintained its integrity and
ontamination is not leaching to the groundwater.

2.8.4 Statutory Determinations

The selected remedy discussed in Section 2.8.3 satisfies the reguirements under Section 121 of
CERCIA to:

Protect human health and the environment.
Comply with ARARs.
Be cost-effective.
Use permanent solutions and alternative treatment technologies or resource recovery technologies to
the maximum extent practicable.
Satisfy the preference for treatment as a principal element.

2.8.4.1 Protection of Human Health and the Environment

The selected remedy, Alternative 2, composite cap, will reduce risks to future users of Cluster 1
through containment of the entire volume of waste in the landfill with an impermeable cap. Alternative 2
is highly protective of human health and the environment because it prevents migration of contaminants to
the environment by preventing infiltration of precipitation and eliminating the potential for direct contact
with the waste. Also, the potential for surface waster contamination due to runoff is eliminated, as is the
potential for airborne dispersion of potentially contaminated dust, except during construction activities.
However, surrounding communities are sufficiently distant to be relatively unaffected by noise and dust.
Precautions will be taken to ensure the safety of site workers, who will wear appropriate personal protective
eguipment. Dust and erosion control measures are implemented to minimize off-site migration of sediment and
particulates. All work is conducted in compliance with applicable OSHA regulations, and workers have all
appropriate health and safety certifications.

No adverse environmental impacts are expected from capping activities under this alternative.

2.8.4.2 Compliance with ARARs

The selected remedy will comply with all chemical-, location-, and action-specific ARARs. By
containing the waste beneath an impermeable cap and using appropriate engineering controls during
construction, operations, and maintenance to prevent release of pollutants to air, land or water, the
selected remedy will achieve the ARARs listed below.
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Table 8 (Con't)

COST ESTIMATE
GROUNDWATER ALTERNATIVE 5

CAPITAL COSTS

Item Rate ($) Quantity Unit Cost ($)

Groundwater Treatment (**)
ALT.l - Vessels at 3 Sites (*)
- (3) 10,000 gallon vessels (8370x1.5=$12,555) (n) 12,555 /tank 3 tanks 37,665
- (1) 5,000 gallon vessels (2977 x 1.5 = $4,465) (o) 4,465 /tank 1 tanks 4,465
- Reactive Media (p) 477 /ton 472 tons 225,144
- (3) Pre-fabricated treatment system buildings, including heating, insulation 57,000
vents, etc. Footings and concrete slab ($6000 additional) for (2) sites. (i)
Groundwater Treatment Subtotal 324,274

Land Use Restrictions for Groundwater 4,000

Construction Subtotal 461,650

Construction Contingencies (20%) 92,330

Health and Safety Training and Eguipment (2.5%) 11,541

Total Construction Cost 565,521

Design, Engineering, and Construction Management (25%) 141,380

TOTAL CAPITAL COST 706,901

NOTE:
* ALT 1 = Treatment units at 3 contamination sites; 1-10,000 gallon at each and an additional 5,000 gallon tank at silos.

** The capital costs for the above ground treatment units shown in this table are estimates based on bench scale results for TCE degradation rates
The costs for implementation of full scale operation will vary based on the results of a pilot scale field testing program.
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Table 8 (Con't)

COST ESTIMATE
GROUNDWATER ALTERNATIVE 5
O&M COSTS

Item

Annual Groundwater Monitoring
- Sample Analysis (VOCs) (30-day turnaround) (f)
- QA/QC Sample analysis (field and trip blanks) (f)
- Sample containers and shipment (i)
- Labor (i)
- Field supplies (i)
- Report preparation and sample management (i)
Annual Sampling Subtotal

Above Ground Reductive Dehalogenation System
- Visual Inspection (2 hours per day) (i)
- Influent and effluent sampling including VOC's analysis, blanks, containers,
shipping, field supplies, and report preparation (8 [Alt 1]x!2x$145xl.5)(f)
(6[Alt 2]xl2x$145xl.5)(f)
- Spare parts (average) (i)
System Subtotal

Pumps

Annual O&M Subtotal

Contingency and Overhead (20%)

Annual O&M Cost

TOTAL O&M COST (15 YEARS @ 5% DISCOUNT FACTOR)

Reactive Media Replacement (Assumed at 7.5 years $250,000 PW @ 5%)

NET PRESENT WORTH OF GROUNDWATER ALTERNATIVE 5
Rate ($)
Quantity
Unit
Cost ($)
145 /sample
145 /sample
100 ea
1,200 /day
225 /sample
3,000 ea
40 /day
0.653 /1000 gal.
7 sample 1,015
4 sample 580
2 ea 200
2 days 2,400
7 sample 1,575
1 ea 3,000
8,770
365 days 14,600
20,880
1, 600
37,080
36792 24,025
69,875
13,975
83,850
870,365
160,000
1,737,266
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Table 8 (Con't)

COST ESTIMATE
GROUNDWATER ALTERNATIVE 5
NOTES
Unless otherwise stated costs were obtained from R.S. Means, 1993.
(a) Vendor Quote: Human Factors Applications, Maryland.
(b) Vendor Quote: Hardin-Huber, Inc., Baltimore, Maryland.
(c) Drilling length of 310 feet = 2 wells @ 30', 2 wells @ 50', and 3 wells @ 50' (silos)
(d) Approximately 3.5 tons = 310 linear feet x 6" dia borehole x 100 Ib/CF
Soil will be stored on plastic sheeting onsite; should testing reveal the presence of minimal to no contamination,
cuttings may be disposed by spreading them onsite.
(e) Typical cost for loading, hauling, and incineration of soil at Soil Safe, Baltimore, MD (if necessary).
(f) Vendor Quote; General Physics, Gaithersburg, Maryland.
(g) One 6,500 tank per treatment site; volume development water = 20gpm x 2 hours x 2 wells (or 3 wells).
(h) Vendor Quote; Baker Tanks
(i) Dames & Moore estimate
(j) Vendor Quote: Drillers Services, Inc. Millersville, Md/Hardin-Huber, Inc., Baltimore, Maryland
(k) Pipe length/trenching estimate from southern and northern contamination areas to central treatment facility at silo pad.
(1) Material based on vendors guote: J.P. McElvenny Co., Inc., Exton, Pa. Installation cost based in R.S. Means.
(m) Rates were obtained from R.S. Means, 1992. Unit costs for hazardous waste were increased by 50%.
(n) Vendor Quote: Chem-Tainer, West Babylon, New York.
(o) Vendor Quote: Tarus Eguipment Co., Columbus Ohio
(p) Vendor Quote: Environmental Technologies, Inc., Ontario, Canada.
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Table 10

COST ESTIMATE
LANDFILL ALTERNATIVE 2

Installation of a Composite Cap and Land Use Restrictions
Cluster 1, Aberdeen Proving Ground

CAPITAL COSTS
Item

Site Preparation
- Site clearing, grubbing, hauling and disposal (a)
- UXO clearance (h)
- Site grading material (a)
- Proofrolling (a)
Site Preparation Subtotal
Rate ($)(a)
Quantity Unit Cost ($)
3825 /acre
1195 /day
19.97 /cy
1.43 /sy
Landfill Cap
- Geosynthetic Clay Liner (c) 0.55 /sf
- Synthetic geomembrane (installed and tested) (d) 3.62 /sf
- Synthetic geonet for drainage (installed and tested) (d) 0.90 /sf
- Geotextile filter fabric (installed) (d) 4.00 /sy
- Topsoil (2 ft., installed) (a) 21.07 /cy
- Vegetation (a) 1.96 /sy
- Vent system (including 2 wells, filter fabric, and geonet for gas collection) (d,f)
- Anchor trench (including excavation, loading, hauling, disposal, gravel, topsoil and filter fabric) (a,d)
- Mobilization/demobilization (f)
Landfill Cap Subtotal
Land Use Restrictions
(including perimeter chain link fence and land use restrictions)
1.1
10
2228
5347

49,000
49,000
49,000
5400
4456
1,815

acre
days
cy
sy

sf
sf
sf
sy
cy
sf

4,028
11,950
44,493
7,646
68,297
26,950
177,380
44,100
21,600
93,888
3,557
68,700
106,118
9,000
551,293
27,000
(a,f)
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Table 10

COST ESTIMATE
LANDFILL ALTERNATIVE 2
CAPITAL COSTS
Item
Well Abandonment
- Abandon 2 well (160 feet) (b, f)
- Chemical analysis of drummed waste (TCLP)(i)
- Disposal of drummed solid waste (f)
- Disposal of drummed decon rinseate (RCRA organic extraction) (f)
- Transportation of drum shipment (solid & liquid) (f)
Well Abandonment Subtotal

Installation of Monitoring Wells (b)

Construction Subtotal

Construction Contingencies (20%)

Health and Safety Training and Equipment (including dust control equipment) (2.5%)

Total Construction Cost

Design Engineering, and Construction Management (25%)

TOTAL CAPITAL COST
Rate ($)(a)
1,600 /sample
390 /drum
1.25 /gal
300 /shipment
3,225 /well
Quantity Unit
Cost ($)

3 samples
1 8 drums
110 gals
1 shipment

3 wells

11700
4,500
7,020
138
300
23, 658
9, 675
679,923
135,985
16,998
832,905
208,226
1,041,132
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Table 10 (con't)

COST ESTIMATE
LANDFILL ALTERNATIVE 2
O&M COSTS
1,225 /sample
1,225 /sample
100 ea
1,200 /day
225 /sample
3,000 ea
sample
sample
ea
days
sample
ea
Item Rate ($)(a) Quantity

Annual Groundwater Monitoring
- Sample Analysis (VOCs, semi VOC's, metals, and pesticides) (g)
- QA/QC sample analysis (field and trip blanks) (g)
- Sample containers and shipment (f)
- Labor (f)
- Field supplies (f)
- Report preparation and sample management (f)
Annual Sampling Subtotal

Inspection and Maintenance of Landfill Cap
- Routine Inspection and minor repairs (20 days/year) (f) 500 /day 20 days
- Mowing of the cap (assume mowed 3 times/year) (f) 225 /ac 2 ac
Inspection and Maintenance Subtotal

Annual O&M Subtotal

Contingency and Overhead (20%)

Annual O&M Cost

TOTAL O&M COST (FOR 30 YEARS @ 5% DISCOUNT FACTOR)

NET PRESENT WORTH OF LANDFILL ALTERNATIVE 2-SYNTHETIC CAP

(a) Unless otherwise stated costs were obtained from R.S. Means, 1993
(b) Vendor guote; Environmental Drilling, Inc., Baltimore, Maryland.
(c) Vendor guote; James Clem, Corp., Fairmont, Georgia
(d) Vendor guote; Miller Company, Fallston, Maryland.
(e) Vendor guote; Hardin and Huber, Baltimore, Maryland
(f) Dames & Moore estimate.
(g) Vendor guote; Savannah Laboratories, Savannah, Georgia
(h) Vendor guote; UXB International, Inc., Chantilly, Virginia.
(i) Includes one sample of soil cutting from each well abandonment borehole and one sample of rinsewater.
Unit
Cost ($)
3,675
2,450
100
1,200
675
3,000
11,000
10,000
450
10,450

21,550

4,310

25,860

397,533

1,438,665
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Chemical-Specific ARARs

- Maryland standards for groundwater monitoring and protection (COMAR 26.13.05.06) apply to
groundwater guality in the vicinity of the landfill as determined by periodic groundwater
monitoring (applicable).

- Maryland air guality regulations (COMAR 26.11.01-26.11.02.21) apply to cap construction,
operations, and maintains activities that may result in the discharge of pollutants to the
atmosphere (applicable).

Location-Specific ARARs

- Maryland Natural Resources Code annotated, Sects. 8.1801 to 8.1816, applies to construction
activities in the Chesapeake Bay critical area (applicable).

Action-Specific ARARs

- Maryland hazardous waste management reguirements for closure and postclosure (COMAR
26.13.05.07) that apply to wastes left in place, reguiring a cover (applicable).

- Maryland hazardous waste management landfill standards (COMAR 26.13.05.14) that provide
design reguirements for hazardous waste landfill caps (applicable).

- RCRA Subtitle C Standards for miscellaneous units (40 CFR 264 Subpart X) may apply to UXO
encountered during cap construction activities (relevant and appropriate).

- Fish and Wildlife Coordination Act, which governs the conservation of wildlife resources (such as
the bald eagle) that may rest in the Edgewood Area and be distributed during constructions
activities (applicable).

- Maryland erosion and sediment control regulation (COMAR 26.09.01) apply to disturbance of
significant guantities of earth such as would be expected with construction of a cap (applicable).

- Maryland regulations for well drillers (COMAR 26.05) apply to construction of monitoring wells
near the landfill (applicable).

2.8.4.3 Cost-Effectiveness

The selected remedy is cost-effective because it has been determined to provide overall effectiveness
proportional to its cost, the net present worth being $1,438,665. The estimated cost of the selected remedy
is less than the cost of conventional excavation or telerobotic excavation of the landfill contents.

2.8.4.4 Utilization of Permanent Solutions and Alternative Treatment Technologies to the
Maximum Extent Practicable

Alternative 2 is a permanent solution that uses alternative treatment to the maximum extent
practicable. Alternative 1 fails to meet the threshold criteria of overall protection and compliance with
ARARs and is thus clearly unacceptable. Alternatives 2, 3, and 4 meet the threshold criteria. Alternative 2
is preferred because although landfill contents are not removed-and the toxicity and volume of contaminants
are not reduced-the mobility of the contaminants and short-term risks are minimized. Alternatives 3 and 4
are comparable in terms of the degree of long-term effectiveness and reduction in toxicity, mobility, and
volume of waste. They differ primarily in terms of short-term impacts and implementability. The selected
remedy provides more short-term protection than Alternatives 3 and 4 because no wastes are disturbed and
therefore risk to the community is minimized. Alternatives 3 and 4 are more difficult to implement because
of the innovative nature of the air shelter and the significant amount of waste that must be excavated.

The support of the state and community in the evaluation process and the selection of Alternative 2
further justify the selection of Alternative 2.

2.8.4.5 Preference for Treatment as a Principal Element

The statutory preference for treatment is not satisfied by the selected remedy because neither the
volume nor toxicity of the waste is reduced. However, the size of the landfill, the potential presence of
UXO in the waste, and the fact that no major sources of contamination have been identified support a
containment rather than a removal remedy. Because this remedy will result in hazardous substances
remaining on-site above health-based levels, a review will be conducted within five years after
commencement of remedial action to ensure that the remedy continues to provide adeguate protection of
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human health and the environment.

2.9 SLUDGE (SANITARY SEWER SYSTEM) REMEDIATION

The Army used the conclusions from the RI, the remedial action objectives listed in the FS, and
ARARs to set cleanup objectives for the sludge in the sewer lines at Cluster 1. Four septic tanks and one
siphon tank in the launch area and the sewer line and manhole that connect Building E6872 with the septic
tanks and distribution box are considered to be of concern. Elevated levels of both organic and inorganic
contaminants were detected in sludge samples (see Table 2) collected from several of the septic tanks and
the manhole. The cleanup objective for the sanitary system is to prevent the migration of
contamination from the sludge to groundwater and surface water/sediment.

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

2.9.1 Description of Alternatives

2.9.1.1 Alternative 1: No Action

In this alternative, no remedial actions are performed at the site. No efforts are undertaken to
contain, remove, or treat contaminants. However, annual sampling and analysis of septic/syphon tanks and/or
the sand filters is performed for 15 years. Evaluation of the no-action alternative provides a baseline
against which to measure other alternatives.

With respect to ARARs, although no receptors are currently exposed to the sludge, the RCRA
reguirements for closure and postclosure, as implemented by COMAR 26.13.05.07, are not met because
no controls are implemented to protect human health and the environment from the contaminated sludge
over the long-term.

This alternative does not achieve the protection of human health and the environment within the
guidelines of the NCP. The safety risks presented in Sect. 2.6.1 for on-site residents are not reduced.

The costs for Alternative 1 are as follows:

Capital costs: $0
O&M cost: $3,430
Net present worth: $35,603 for 15 years
This alternative is expected to reguire no time to implement.

2.9.1.2 Alternative 2: Clean and Close Sanitary Sewer System in Place

This alternative involves:
Pumping contaminated sludge from four 1,000-gal septic tanks and one 1,000-gal siphon tank.
Cleaning the tanks, one manhole, and the launch area sewer lines by high-pressure water blasting.
Filling tanks with inert material.
Removing surface structures, grading, and vegetating of disturbed areas.
Disposing of contaminated sludge and wash water at a licensed RCRA facility in accordance with
Maryland regulations governing the transportation and disposal of hazardous waste (COMAR
26.13.04) at a licensed RCRA facility.

This alternative meets the sanitary sewer system cleanup objective of preventing the migration of
contamination from the sludge to groundwater or surface waster/sediment by eliminating the source of
contamination from the site and eliminating the containment transport pathway.

The costs for Alternative 2 are as follows:

Capital Costs: $89,884 to $151,632 (depending on sludge disposal method)
O&M cost: $0
Net present worth: (Egual to capital costs)
This alternative is expected to reguire 1 to 2 months to implement.

2.9.1.3 Alternative 3: Clean and Excavate the Sanitary Sewer System

This alternative involves:

Pumping contaminated sludge from four 1,000-gal septic tanks and one 1,000-gal siphon tank.
-------
Cleaning the tanks, one manhole, and the launch area sewer lines via high pressure water blasting.
Excavating the sewer lines, manhole, and five tanks after cleaning in accordance with Maryland
erosion and sediment control regulations (COMAR 26.09.01) and OSHA construction safety guidelines
(29 CFR 1926).

Disposing of contaminated sludge, washwater, and excavation debris (tanks, manhole, pipes) at a
licensed RCRA facility in accordance with hazardous waste management regulations (COMAR
26.13.04). The excavation debris may be disposed of at a sanitary landfill if it is deemed
nonhazardous in accordance with Maryland solid waste management regulations (COMAR 26.04.07).
Temporary stockpiling of excavated hazardous waste to await off-site disposal in accordance with
hazardous waste management regulations for waste piles (COMAR 26.13.05.12).
Shipping hazardous waste off-site in compliance with Maryland regulations governing the
transportation and disposal of hazardous waste (COMAR 26.13.04).

This alternative meets the sanitary sewer system cleanup objective of preventing the migration of
contamination from the sludge to groundwater or surface water/sediment by eliminating the source of
contamination from the site and eliminating the contaminant transport pathway.

The costs for Alternative 3 are as follows:

Capital costs: $205,031 to $291,068 (depending on sludge and debris disposal method)
O&M cost: $0
Net present worth: (Egual to capital costs)
This alternative is expected to reguire 4 to 6 months to implement.

2.9.2 Summary of the Comparative Analysis of Sanitary Sewer System Cleanup Alternatives

As reguired by CERCLA, the remedial alternatives listed above were evaluated using the nine criteria
specified by USEPA (see Table 6). This section and Table 11 summarize the relative performance of each
of the Sanitary Sewer System remediation alternatives with respect to the nine CERCLA evaluation
criteria.

2.9.2.1 Threshold Criteria

Overall protection of human health and the environment Alternatives 2 and 3 (clean and close in situ and
clean and excavate, respectively) provide overall protection of human health and the environment by removing
the source of contamination and eliminating the contaminant migration pathway. Alternative 1 (no action)
provides no overall protection of human health and the environment.

Achievement of ARARs Alternatives 2 and 3 comply with all ARARs. Alternative 1 (no action) does
not comply with ARARs.

2.9.2.2 Primary Balancing Criteria

Long-term effectiveness Although both Alternatives 2 and 3 provide long-term effectiveness, Alternative 3 may
provide a slightly greater degree of long-term effectiveness because the sewer lines, manhole, and tanks are
permanently removed from the site, thereby eliminating and potential for water to infiltrate the
loose-fitting pipes and mobilize any potentially present contaminant residues. Alternative 2 minimizes this
possibility by filling the lines, tanks, and manhole with an inert material. Alternative 1 (no action)
provides no long-term effectiveness.

Reduction in toxicity, mobility, or volume of contaminants Alternatives 2 and 3 achieve relatively similar
degrees of reduction in the mobility, toxicity, and volume of waste because the contaminated sludge is
removed in both cases. Alternative 1 (no action) provides no reduction in toxicity, mobility, or volume of
contaminants.

Short-term effectiveness Both alternatives may involve short-term impacts from worker exposure to
contaminated sludge and confined space entry. Alternative 2 has a slightly higher level of short-term
effectiveness than Alternative 3 because disturbance of the system and surrounding solid is minimized by
leaving the system components in place. Alternative 3 has a lower level of short-term effectiveness than
Alternative 2 because of the potential for accidental detonation of UXO during excavation activities. In
addition, because the sewer lines are composed of cement-asbestos pipes, Alternatives 3 reguires more
extensive health and safety precautions that Alternative 2. Alternative 1 (no action) provides no short-
term effectiveness.
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Compliance with Long-term Reduction of toxicity, Short-Term
ARARs effectiveness and permanence mobility, and volume Effectiveness Implementability
No reduction of toxicity, No impacts on community or No construction,

No action protection. RAOs are not Not met. Risks are not reduced. mobility, and volume. worker health or the equipment, storage,

environment.
Highly effective in removing
High level of protection contaminants. Eliminates
Capital $89,884 or
Sludge Alternative Potential source of Compliance with all
2-clean and close contamination is removed ARARs.
in situ and the physical hazard of
Depends on sludge
tank collapse is eliminated.
High level of protection. Impact on community health or
Potential source of Highly effective in removing the environment is greater
Capital $205,031 or
Sludge Alternative contamination is removed. contaminants. Eliminates Permanent reduction in because of excavation. Required labor, materials, capital
$291,068,
3-clean and Sewer lines, manhole and Complies with all potential source of groundwater toxicity, mobility, and
excavate tanks are removed, thus ARARs. or surface water/sediment volume.
Depends on sludge
preventing water infiltration
and debris disposal.
into sewer system.
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Implementability The labor, equipment, and material necessary to implement Alternatives 2 and 3 are readily
available. Alternative 2 is expected to be relatively easy to implement. Alternative 3 is expected to be
more difficult to implement that Alternative 2 because the system will be excavated, involving significant
demolition and grading activities, along with increased risk for encountering
UXO. Alternative 1 (no action) requires no effort to implement.

Cost The estimated capital, O&M, and net present worth costs for each sewer system remedial alternative are
summarized in Table 11.

2.9.2.3 Modifying Criteria

State Acceptance MDE took part in selecting the remedial alternatives for sewer system cleanup at Cluster 1
and identifying cleanup objectives (preventing accidental detonation of UXO and leakage of contaminants to
the environment). In addition, the State of Maryland is satisfied that the appropriate remedial action
process was followed in evaluating remedial action alternatives for the sewer system at Cluster 1 and concurs
with the selected remedy.

Public Acceptance APG solicited input from the public on the development of alternatives and on the
alternatives identified in the proposed plan. The public is in agreement with the cleanup objectives,
and most of the commenters were in agreement with the preferred alternative. Several members of the public
preferred that the sanitary sewer system be excavated. During the comment period, APG provided these
commenters with additional information on their concerns. It appears the additional information satisfied
their concerns. A detailed summary of concerns and APG's responses are contained in section 3.0.

2.9.3 Selected Remedy

The selected remedy to clean up the sewer system at Cluster 1 is Alternative 2, Clean and Close
Sanitary System in Place. This alternative is highly protective of human health and the environment,
meets all ARARs, has a high level of long-term effectiveness and permanence, reduces the mobility and
volume of waste by removing the sludge from the site, has a high level of short-term effectiveness, is
expected to be easily implementable, and is relatively cost-effective. The selected remedy involves:

Pumping contaminated sludge from four 1,000-gal septic tanks and one 1,000-gal siphon tank.
Cleaning the tanks, one manhole, and the launch area sewer lines via high-pressure water blasting.
Filling the tanks, manhole, and lines with inert material.
Removing surface structures, grading, and vegetating disturbed areas.
Disposing of contaminated sludge and washwater at a licensed RCRA facility.

The costs for Alternative 2 are summarized in Table 12. This alternative would prevent the migration
of contamination from the sludge to groundwater or surface water/sediment by removing the sludge from the
site and eliminating the potential transport pathway.

2.9.X Performance Standards

The system will be cleaned by water blasting and filled with an inert material to prevent collapse of
the piping system. Sludge, wash water, and any other generated waste will be removed and disposed of or
treated in accordance with Federal and state requirements.

2.9.4 Statutory Determinations

The selected remedy discussed in Sect. 2.9.3 satisfies the requirements under Sect. 121 of CERCLA
to:

High Pressure Water Blast Sewer Lines, Manhole, and Septic Tanks;
Fill Tanks, Sewer Lines with Inert Material
Offsite Disposal of Sludge/Cleaning Fluid at a Licensed RCRA Facility
Cluster 1, Aberdeen Proving Ground
Item
Removal of Sludge
CAPITAL COSTS

Rate ($)(a) Quantity

1.45 /gal 5,000
1.04 /gal
390.00 /drum 100
775.00 /drum 100
0.52 /gal
1.25 /gal
5,000
drums
drums

2,500
High Pressure Water Blast using line pigging
(including eguipment, labor, and materials)

Inert Fill Material (Flo-Ash assumed)

Disposal
- Septic waste (RCRA stabilization)
- Septic waste (RCRA incineration)
- Rinse Water (RCRA treatment) 0.52 /gal 2,500
- Rinse Water (RCRA organic extraction)

Transportation
- Drum Shipment (sludge) 100
- Vacuum Truck (rinse water)

Subtotal

Contingency (20%)

Health and Safety Plan and Equipment (2.5%)

Subtotal

Design, Engineering, and Management (25%)

TOTAL CAPITAL COST

(a) All guotes were provided by the Clean Harbors Environment Services, Inc.
(b) Assumes RCRA stabilization of septic waste, RCRA treatment of rinse waters.
(c) Assumes RCRA incineration of septic waste, RCRA organic extraction of rinse waters.
Unit

gal

gal
Cost 1 ($) (b)

7,250

5,000

5,200
39,000
77,500
gal
drums
1,300
gal
300
1,468
650

58,700

11,740

71,908

17,977
Cost 2 ($)(c)

7,250

5,000

5,200
3,125
89,884
300
650

99,025

19,805

2,476

121,306

30,326

151,632
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2.9.4.1 Protection of Human Health and the Environment

The selected remedy, Alternative 2, will reduce risks posed to future users of Cluster 1 through
high-pressure water blasting of sewer system components and tanks, filling of components with an inert
material, and off-site disposal of sludge and wash water. Under this alternative, the source of potential
contamination (sludge) is removed and the physical hazard of tank collapse is eliminated. Although the
potential for water to infiltrate the loose-fitting pipes still exists, it is minimized by filling the system
with an inert material. In addition, the permanent removal of contaminated sludge from the sewer lines
reduces the potential for migration of any residual contamination to groundwater and surface water. However,
the transportation of the contaminated sludge to be disposed of poses some risks to human health and the
environment because fluid may leak from the vehicle during transport or an accident may release
contaminated fluid to the environment. Engineering controls and rigorous safety practices will minimize
such risks. No construction activities are anticipated with this alternative. Exposure of workers to
contaminants via inhalation and dermal contact is possible, especially during removal of contaminated
sludge from the 1,000-gal tanks and the manhole. However, workers will wear protective clothing to
minimize contact with contaminated sludge.

2.9.4.2 Compliance with ARARs

The selected remedy will comply with all ARARs. The selected remedy will achieve the ARARs listed
below by removing the sludge from the site and filling the sewer system with an inert material, thereby
preventing future release or transport of contaminants to the environment. In addition, appropriate
engineering controls will be employed during a remediation to prevent release of pollutants to air, land, or
water.

Chemical-Specific ARARs

- Maryland standards applicable to generators of hazardous waste (COMAR 26.13.03) apply to the
generation of hazardous sludge and washwater as a result of cleaning the sewer lines (applicable).

- RCRA Subtitle C identification and listing of hazardous waste (40 CFR 261) applies to the
characterization of sludge and washwater before disposal (applicable).

- Toxic Substances Control Act polychlorinated biphenyl (PCB) reguirements (40 CFR 761) apply to
PCB-containing materials (applicable).

Location-Specific ARARs

None.

Action-Specific ARARs

- Maryland standards applicable to tanks and containers (COMAR 26.13.05.09-.10) apply if
hazardous sludge or washwater is stored in tanks or containers prior to disposal (applicable).

- Maryland transportation and disposal standards (COMAR 26.13.04) apply to shipment of hazardous
sludge and washwater off-site (applicable).

- Federal Fish and Wildlife Coordination Act reguirements govern the conservation of wildlife
resources (such as bald eagles) that may be present as the Edgewood Area and may be disturbed
during construction activities (applicable).

2.9.4.3 Cost-Effectiveness

The selected remedy is cost-effective because it has been determined to provide overall effectiveness
proportional to its cost, the net present worth cost being $89,884 or $151,632, depending on the sludge
disposal method. The estimated cost of the selected remedy is less than the cost of cleaning the sewer
system and excavating it.

2.9.4.4 Utilization of Permanent Solutions and Alternative Treatment Technologies to the
Maximum Extent Practicable

The selected remedy, Alternative 2, is a permanent solution that uses treatment to the maximum extent
practicable. Alternative 1 fails to meet the threshold criteria of overall protection and compliance with
ARARs and is thus clearly unacceptable. Both Alternatives 2 and 3 meet the threshold criteria. They are
also comparable in terms of reduction in toxicity, mobility, and volume of contaminants; implementability;
and degree of protection. They differ primarily in terms of cost. Alternative 3 may generate additional
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short-term impacts as a result of activity-generated dust, soil erosion, or accidental detonation of UXO. The
increase in long-term protection afforded by Alternative 3's permanent removal of sewer system components is
only slightly greater than that of Alternative 2. Because Alternative 2 is less costly while providing a
high degree of protection and fewer short-term impacts, it is the preferred alternative.

The support of the state and community in the evaluation process and the selection of Alternative 2
further justify the selection of Alternative 2.

2.9.4.5 Preference for Treatment as a Principal Element

The statutory preference for treatment is satisfied by using off-site treatment of the sludge (by
stabilization or incineration) and washwater (by organic extraction or RCRA treatment) as the primary
means for disposing of the contaminants.

2.10 DOCUMENTATION OF SIGNIFICANT CHANGES

The selected remedies were the preferred alternatives presented in the Proposed Plan. No changes
have been made.

3. RESPONSIVENESS SUMMARY

The final component of the Record of Decision (ROD) is the Responsiveness Summary. The purpose of
the Responsiveness Summary is to provide a summary of the public's comments, concerns, and guestions about
the groundwater, landfill, sanitary sewer system, and former missile silos at the Aberdeen Proving Ground
(APG) Nike Site and the Army's responses to these concerns.

During the public comment period, written comments, concerns, and guestions were received by APG and
the Environmental Protection Agency (EPA) .

APG held a public meeting May 8, 1996, to formally present the Proposed Plan and to answer guestions
and receive comments. The transcript of this meeting is part of the Administrative Record for the site. All
comments and concerns summarized below have been considered by the Army and EPA in selecting the final
cleanup methods for the groundwater, landfill, and sanitary sewer system at the Nike Site.

This responsiveness summary is divided into the following sections:

3.1 Overview
3.2 Background on Community Involvement
3.3 Summary of Comments Received During Public Comment Period and APG's Responses
3.4 Sample Newspaper Notice Announcing Public Comment Period and the Public Meeting

3.1 OVERVIEW

At the time of the public comment period, the Army had endorsed preferred alternatives for the cleanup
of the groundwater, landfill, and sanitary sewer system at the Nike Site. For the groundwater, APG
recommended aboveground treatment by reductive dehalogenation. APG's preferred alternative for the
landfill was to construct a composite cap. For the sanitary sewer system, APG proposed cleaning and properly
closing the system. As part of the Proposed Plan, APG also recommended taking no further action
at the missile silos. EPA concurred with the preferred alternatives. Maryland Department of the Environment
supported the Army's plan and stated it would finalize its position after the public comment
period.

The public agreed there was a need to remediate the groundwater. The majority of the commenters
agreed with treatment by aboveground reductive dehalogention. A few community members and a community group,
Neighbors Involved in the Community of Edgewood (NICE), preferred treatment by air stripping. Aberdeen
Proving Ground Superfund Citizens Coalition (APGSCC) agreed with the Army's preferred alternative but
believed the ROD should not be signed until additional site characterization had been completed.

The majority of the public who returned comment forms agreed with the preferred alternative for the
landfill of installing a composite cap. Approximately 45% of the individuals who returned comment forms
expressed a preference for conventional or telerobotic excavation. The community group NICE also preferred
excavation. APGSCC commented that additional characterization of the landfill should be performed before
making a decision on a cleanup method.

Approximately 70% of the community members who returned comment forms agreed with cleaning and
closing the sewer system in place. Several commenters, including the community group NICE, recommended
the sewer system be excavated. APGSCC originally supported the preferred alternative, assuming the property
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remained under Army control, in later comments, APGSCC supported excavation, considering it
quite possible that parts of APG would be returned to civilian ownership.

The public indicated support for the preferred alternative for the missile silos of closure in place.

APG has summarized and addressed questions and concerns raised by the public in Sect. 3.3. APG
hopes this additional information will clarify further the rationales for the decisions made for the Nike
Site cleanup.

3.2 BACKGROUND ON COMMUNITY INVOLVEMENT

Citizen's interest in the Nike Site increased substantially in the sprinq of 1995 after the appearance
of several newspaper articles about the Nike Site. Prior to this time, interest primarily came from the
Restoration Advisory Board meetinqs (formerly Technical Review Committee meetinqs) and from the
Executive Director of the APGSCC.

Concerns raised before the Proposed Plan included interest in the extent of the qroundwater
contamination and whether it had moved off-post. APG has been keepinq the community informed about its
investiqation results throuqh the monthly Restoration Advisory Board meetinqs, fact sheets, and personal
discussions. Residents also were concerned about the possibility of munitions' still beinq present at the
site. APG is addressinq munitions as a separate removal action and will continue to work closely with the
community on this project.

APG has maintained an active public involvement and information proqram for the Nike Site. Hiqhliqhts
of the community's involvement in the site and APG's activities durinq the last 2 years follows.

APG beqan discussinq possible cleanup methods for the Nike Site at Technical Review Committee
meetinqs in July 1994. Other Technical Review Committee/Restoration Advisory Board meetinqs where
APG presented information on the Nike Site cleanup included February 1995, April 1995, Auqust 1995,
October 1995, November 1995, January 1996, February 1996, March 1996, and April 1996.

APG's Commandinq General, Major General Traqemann, sent a letter in March 1995 to more than
20,000 residents who live alonq APG's Edqewood Area northern boundary. Althouqh the letter
primarily discussed the possibility of ordnance alonq the boundary, it also invited residents to
join the restoration proqram's mailinq list. The letter also invited residents to attend one of the
availability sessions scheduled for April.

APG held availability sessions on April 1, April 8, and April 19, 1995. More than 500 people
attended and had information available to them on the proposed cleanup plans for the Nike Site.

APG held four tours of the APG Edqewood Area for the public on May 6, 1995. The tours included the
0-Field qroundwater treatment facility, the Nike Site, and the Lauderick Creek Study Area. Displays
on APG's cleanup activities were set up at the Conference Center. Approximately 100 citizens
attended.

On May 10, 1995, APG met with representatives of NICE to answer their questions about the Nike Site
cleanup plans.

On May 12, 1995, APG met with representatives of the APGSCC and their advisors reqardinq the Nike
Site. APG staff have met on several other occasions with the Executive Director of the coalition and
their advisors to discuss the Nike Site.

APG made presentations on the Nike Site to the National Association of Independent Fee Appraisers on
May 9, 1995; the Harford County Homebuilders on May 11, 1995; Edqewood Middle School students
on May 31, 1995; and the Harford County Board of Realtors on June 20, 1995.

APG prepared a question and answer fact sheet on ordnance and mailed the fact sheet in July 1995 to
approximately 23,000 residents in the Edqewood, Joppa, and Abinqdon area and to all citizens on its
mailinq list. APG aqain invited residents to join the mailinq list.

APG made a presentation on the Nike Site to the Harford County Realtors Million Dollars Association
on Auqust 2, 1995.

In December 1995, APG sent a letter to 450 residents on its mailinq list who live near the Nike Site
askinq if they were interested in attendinq small qroup interview sessions on the Nike Site planned
for early 1996. Interested residents returned postcards notinq the best days and times to hold the
meetinqs.
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In February 1996, APG held five small interview sessions with citizens residing closest to the Nike
Site to hear their concerns. APG held similar meetings for on-post residents living near the site
and employees who work near the site.

APG released the Proposed Plan for the Nike Site for public comment from April 24 to June 8, 1996.
In response to a reguest from Congressman Ehrlich and a citizens group. APG and EPA extended the
comment period an additional 30 days to July 8, 1996. Copies were available to the public at APG's
information repositories at the Aberdeen and Edgewood Branches of the Harford County Library, Miller
Library at Washington College, and the Baltimore County Department of Environmental Protection.

APG issued a press release announcing the availability of the Proposed Plan, the dates of the public
comment period, and the date and time of the public meeting in The Aegis, The Cecil Whig, and
Avenue, and the Kent County News.

APG prepared and published a fact sheet on the Proposed Plan. APG mailed copies of this fact sheet
to more than 2,500 citizens and elected officials on its Installation Restoration Program mailing
list. The fact sheet included a form that citizens could use to send their comments to APG.

On May 4, 1996, APG held a tour of the Nike Site for the public.

On May 8, 1996, APG held a public meeting at the Edgewood Middle School. Representatives of the
Army, EPA, and the Maryland Department of the Environment answered guestions about the proposed
alternatives under considerations.

3.3 SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC COMMENT PERIOD AND AGENCY RESPONSES

Comments raised during the Nike Site public comment period on the Feasibility Study and the Proposed
Plan are summarized below. The comments are categorized by topic and by source.

COMMENTS FROM QUESTIONNAIRE INCLUDED WITH FACT SHEET

As part of its fact sheet on the Proposed Plan, APG included a guestionnaire that residents could
return with their comments. APG received 31 completed returns.

Groundwater

Responses on the completed returns were:

1 Alternative A: Take no action
2 Alternative B: Treatment in seguencing batch reactors
1 Alternative C: Treatment by ultraviolet catalyzed oxidation
1 Alternative D: Treatment in place using reductive dehalogenation
20 Alternative E: Treatment by aboveground reductive dehalogenation
4 Alternative F: Treatment by air stripping
2 Have no preference

Comment 1: One person recommended taking no action and testing every month.

APG Response: APG appreciates the desire for effective use of resources. However, it is important to take
action now to restore the groundwater as a resource. One of the EPA'a criteria for evaluating cleanup
actions is whether the action complies with all applicable or relevant and appropriate reguirement, which
includes federal and state regulations. The groundwater at the Nike Site is considered potential drinking
water. Therefore, it is a reguirement that the groundwater be cleanup up to EPA drinking water standards.

Comment 2: One person preferred air stripping because it would be "simpler to run, easier to control
reaction, no sludge generated, no sludge handling costs, proven technology." Another person preferred air
stripping because it "should clean the water better than the rest."

APG Response: All treatment alternatives were shown to be egually effective in treating the water at the
Nike Site. A treatment study was conducted for the preferred alternative, reductive dehalogenation, which
showed reductive dehalogenation would be effective in treating the groundwater. Air stripping does not break
down the trichloroethene (TCE); it merely transfers the TCE to another media such as a carbon filter. The
filter must then be handled as waste. Reductive dehalogenation, however, completely breaks down the TCE into
nontoxic compounds and does not produce any sludge or by-products. Reductive dehalogenations is also easy to
run and maintain.
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Comment 3: One resident commented "I just hope it's not too late for those in Harford County who have
been exposed for years unknowingly." Another resident expressed concern for her mother who died from
cancer and had drank the well water at their home in Edgewood.

APG Response: APG places a high priority on protection of human health. The area of groundwater
containing the TCE is mostly on-post with only a very small area extending onto the Amtrak property. There
are no residential water wells near this groundwater. Because no one is drinking the water, no one has been
exposed to the TCE.

Comment 4: Several residents asked about how and when the discharge would be monitored and the impacts
on Bush River or marine life.

APG Response: The discharge would be monitored in accordance with state reguirements under the National
Pollution Discharge Elimination System (NPDES). These state reguirements are in place to ensure protection
of the streams and marine life receiving the discharge. In addition, these reguirements dictate where and
when samples would be collected to evaluate the discharge. Generally, samples are collected at the discharge
point on a regular basis. A sampling program will be developed to collect samples during and after startup
from the treatment system before water is discharged to the Bush River or a tributary of the Bush River to
verify the treatment system is working correctly and in accordance with the NPDES permit.

Comment 5: One resident commented that "It is difficult for a lay person to judge which is a safer, more
efficient, and cost-effective approach."

APG Response: APG understands that many issues are complex and technical in nature and will, therefore,
strive to provide the public with accurate and understandable information. The public is encouraged to ask
guestions at meetings or call APG for more details. An Information Line is available to ask guestions or
obtain information 24 hours a day; the number is (410) 272-8842 or 800-APG-9998.

Comment 6: A resident asked "What is the effectiveness of ultraviolet oxidation versus iron treatment?"

APG Response: They are both egually effective in treating the contaminated groundwater.

Comment 7: Two residents asked about the 60 years reguired for in-place reductive dehalogenation and
whether the cost was per year or total.

APG Response: The cost shown for in-place reductive dehalogenation is the total estimated cost to install
and operate the system for 60 years. This alternative employs a technology that is installed below ground
(in situ) to treat the groundwater in place. The groundwater is treated as it flows through the iron media.
The other technologies extract the groundwater and treat it above ground. Extracting the groundwater at
various locations in the plume allows a larger area of the plume to be treated at one time. This decreases
the amount of time it takes to treat the plume to concentrations below EPA reguired limits. This is why the
in situ technology has an estimated time for cleanup of 60 years and the other pumping and treatment
technologies reguire only 15 years.

Landfill

Responses on the completed returns were:

0 Alternative A: Take no action
17 Alternative B: Installation of a composite cap
8 Alternative C: Conventional excavation and off-site disposal
6 Alternative D: Telerobotic excavation and off-site disposal
0 Have no preference on the alternative

Comment 8: Several residents expressed a preference for conventional excavation and off-site disposal.
They believe it fixes the problem and eliminates the need to take any other action in the future. One person
preferred Alternative C "only if it could be guaranteed that no gases and chemicals would become airborne
during detonation." Another suggested the telerobotic excavator being used at 0-Field could be used to
validate the cost estimate for excavation.

APG Response: The telerobotic excavator is being used to place sand on top of the 0-Field Landfill.
Because it is not being used for excavation with all the ancillary safety reguirements, the costs would not
be comparable to excavation of the landfill contents at the Nike Site. APG agrees that excavating the
landfill provides a permanent solution for the Nike Site. Capping the landfill was chosen because it is an
egually effective solution and provides the same level of risk reduction as would be achieved with
excavation. Capping of the Nike Site landfill is especially effective because the waste is located above the
groundwater table and the cap prevents water from infiltrating into the waste, thus preventing unknown
-------
hazardous substances from moving out of the landfill.

Comment 9: One person agreed with the composite cap solution but expressed a concern about the "slow
breakdown of containers and leaking of chemicals into the soil."

APG Response: APG shares this concern and has investigated this possibility through its sampling program.
The available information about the landfill indicates construction debris was disposed of at the site. As
part of the remedial investigation of the landfill, APG collected groundwater, sediment, surface water, and
soil samples. The analytical results identified no hazardous waste leaching from the landfill. Because the
landfill is more than 40 years old, and leaching from containers would have begun by now. Capping the
landfill will eliminate infiltration of water into the landfill, which will prevent unknown hazardous
substances from moving out to the landfill. Strategically placed monitoring wells around the landfill will
provide an early warning of any unanticipated problems with the groundwater under the landfill.

Comment 10: One person asked "What are the federal and state reguirements for disposal?"

APG Response: Federal reguirements for disposal include Title 40 Code of Federal Regulations (CFR) Part
264, Standards for Owners and Operators of Hazardous Waste Treatment, Storage, and Disposal Facilities.
State reguirements include Title 26, Subtitle 13, Disposal of Controlled Hazardous Substances. These
regulations described how waste defined as hazardous will be managed during the cleanup process. They
implement the statutory reguirements under the Resource Conservation and Recovery Act (RCRA), which
regulates waste from "cradle to grave." This means that once a waste is created, RCRA imposes
reguirements on those who generated it; those who transport it; and those who ultimately treat, store, or
dispose of it. These federal and state reguirements will dictate how the landfill at the Nike Site is
properly closed.

Sanitary Sewer System

Responses on the complete returns were:

0 Alternative A: Take no action
22 Alternative B: Clean and close in place
8 Clean and excavate
1 No preference on the alternative

Comment 11: Several residents preferred the sanitary sewer system be excavated; their comments included a
preference for what seemed to be a more permanent solution, a concern for civilian or recreational use of the
land in the future, and a concern that cost not be a factor in the decision.

APG Response: Cleaning and closing the system in place is an egually effective and permanent solution as it
removes contaminants and is in accordance with industry standard practices. There are many man-made
features at the Nike Site, such as the missile silos, that will remain in place along with the sanitary sewer
system. If the land were to be turned over, which the Army does not foresee, these features would be handled
at that time. Furthermore, cleaning and closing the sanitary sewer system in place effectively removes any
risks associated with the substances that currently remain in the system. In addition, the EPA reguires cost
be considered when evaluating each alternative, however, protection of human health and the environment is
the more important criteria for evaluation.

Missile Silos

Responses on the completed returns were:

20 Take no action
4 Have no preference
6 No response indicated

Comment 12: One resident asked if the silos are "absolutely harmless" and if not, suggested they be
removed. One resident suggested capping the silos like the landfill. Another resident asked if there were
any alternatives.

APG Response: Because an action has already been taken at the Nike Missile Silos, there are no alternatives
to present. Alternatives were evaluated before the removal action was conducted. This action is in the
Proposed Plan without remedial alternatives because EPA reguires removal actions be presented in the
Proposed Plans to obtain final approval of the action.

The contamination associated with the missile silos was contained within the silos. All contamination
inside the silos was removed and the silos were filled with flowable fill concrete. Removing the
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contamination eliminated any threat it posted. Filling the silos with concrete prevents groundwater from
infiltrating into the silos. The structure that make up the silos are not contaminated. It was the
contamination inside the silos that was the problem; therefore, the silos no longer pose any threat to human
health and the environment.

Miscellaneous Comments

Comment 13: Several residents expressed their appreciation for APG's continuing to take action and
encouraged APG to "keep up the good work."

APG Response: APG acknowledges and appreciates the feedback.

Comment 14: One resident commented that "the briefings and communications, like this booklet, give me
confidence you are doing a good job. You should know that reducing fear and worry is a very important
health benefit of your good work. Thank you."

APG Response: APG acknowledges and appreciates the feedback.

Comment 15: A resident commented "the inclusion of this guestionnaire causes me to pay much closer
attention to the details of information provided. My input makes me feel more involved and responsible in
this clean-up task."

APG Response: APG acknowledges and appreciates the feedback.

COMMENTS AT MAY 8, 1996, PUBLIC MEETING

Following are comments that were raised verbally at the May 8 public meeting on the Proposed Plan. A
full transcript of the meeting is at APG's information repositories.

Groundwater

Comment 16: If charcoal filters were used in the air stripping treatment method, is disposal at a landfill
the only disposal option?

APG Response: Charcoal filters can be regenerated using steam so the filters can be reused. This is
generally more expensive than disposal at a hazardous waste landfill. The solvent, TCE, which would be
removed from the filters, would then reguire proper disposal as a hazardous waste.

Comment 17: What is the least number of years the cleanup using reductive dehalogenation would take?

APG Response: The cleanup could be completed in as few as 7 years or could take as many as 20. This will
be better evaluated through the startup of the system and initial results.

Landfill

Comment 18: When was the landfill first found?

APG Response: The records search done as part of an environmental study in the late 1980s found the first
evidence of the landfill in records and aerial photos from the 1950s.

Comment 19: A resident asked if there is a State of Maryland law that reguires landfills under 10 acres to
be excavated? He strongly prefers the landfill to excavated and believes it is not because of the cost.

APG Response: There is not a Maryland State Law that reguires landfills under 10 acres to be excavated.
Through information searched and discussions with Maryland Department of Environment (MDE) it was
determined there is no law, regulation, or guideline that reguires landfills to be excavated. MDE allows
site closure alternatives to be proposed on a site-by-site basis. MDE allows either excavation or capping to
be considered, regardless of the size.

Comment 20: A resident asked the state if they had data that showed the cap will safety contain a detonation
from a high explosive round with possible chemical rounds nearby.

APG Response: The landfill cap will be designed to contain chemical rounds. The design of the landfill will
be based on the largest expected chemical munition at the Nike Site.

Comment 21: One resident was concerned the landfill is having an impact on his property values. Two other
residents were concerned about their property values' being impacted by the Nike Site in general.
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APG Response: APG appreciates the concern over what is, for most people, their largest financial asset. In
discussions with the community, APG has heard concerns from many people about property values. APG
will continue to distribute accurate information about the Nike Site to the community and, as requested, to
potential home buyers.

Sewer System

Comment 22: Should the land be turned over and someone want to build on that land, won't they have to dig
the sanitary sewer system up? More cost-effective for taxpayer to dig it up so the next guy coming along
doesn't have to dig it up.

APG Response: There are many man-made features at the Nike Site (such as the missile silos) that will be
remaining in place along with the sanitary sewer system. If the land were to be turned over, which the Army
does not foresee, these features would be handles at that time. Cleaning and closing the sanitary sewer
system in place effectively removes any risks associated with the substances that currently remain in the
system. This alternative is also in accordance with industry standard practice for abandonment of sanitary
sewer lines.

Miscellaneous

Comment 23: A resident suggested advertising meetings on Channel 4.

APG Response: We agree this is a good idea and have been discussing the use of cable television in our
public information program. We will keep the community informed on this idea.

Comment 24: A resident stated insufficient amounts of information are being disclosed to buyers of new
homes.

APG Response: While mandatory disclosures of information in under the county's control, APG continues to
be in favor of information on former activities' at APG being disclosed to new buyers. APG has made several
presentations to organizations such as the Harford County Board of Realtors, Harford County Homebuilders,
National Association of Independent Fee Appraisers, and the Harford County Realtors Million Dollars
Association. Many realtors are giving prospective buyers copies of APG fact sheets, and many of the buyers
contact us through our Information Line to obtain additional information. APG will continuing preparing fact
sheets and issuing news releases.

COMMENTS FROM ABERDEEN PROVING GROUND SUPERFUND CITIZENS COALITION

At the public meeting on May 8, 1996, the APGSCC submitted comments on various APG documents,
including the Proposed Plan. Following is a summary of the comments from these documents. (APGSCC is
the recipient of two Technical Assistance Grants from the U.S. Environmental Protection Agency.)

Groundwater

Comments from Aberdeen Proving Ground Superfund Citizens Coalition dated February 28, 1996

Comment 25: APGSCC agrees with the Army's preferred alternative but recommends the selected
alternative not become part of a ROD until the plume is sufficiently characterized.

APG Response: The preferred treatment alternatives is capable of effectively treating the contaminants in
the plume regardless of the size of the plume and will not affect the selection of the treatment alternative
in the ROD. Delineation of the plume will be completed before final design of the system.

Specific guestions raised by APGSCC are:

(a) Is a groundwater flow model being considered for this site similar to that being conducted in the
Westwood Area?

APG Response: A model similar to that as Westwood will not be conducted. However, modeling will be
conducted to determine the placement of the extraction well to ensure the entire groundwater plume will be
captured.

(b) "Have any efforts been made to predict the effects of different seasons on groundwater flow?"

APG Response: Yes, groundwater contour maps have been made at different times of the year to assess
seasonal changes in flow. Water level measurements continue to be collected periodically as more monitoring
wells and piezometers are installed. Groundwater contour maps will continue to be updated.
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(c) "Are other effects on groundwater flow (e.g., shallow residential wells or historical activities) going
to be considered when analyzing surficial aguifer flow direction?"

APG Response: There are no documented shallow wells that would have any influence on surficial aguifer
flow direction. Historical activities have no influence on the current groundwater flow direction. All
pertinent information for analyzing surficial aguifer flow direction will be taken into account.

(d) "Are piezometers going to be used off-base to characterize the extent of hydrogeological flow off-
base?"

APG Response: Yes, piezometers are located off-base to the north of the Nike Site near the Amtrak
Property.

(e) "What is the current plan regarding the utilization of HydroPunch to characterize contamination off-
base?"

APG Response: Hydropunch has been used to characterize the plume along the Amtrak Property. Hydropunch and
monitoring wells will be installed north of the Amtrak property to fully delineate the plume.

(f) "Have chemical data from the 'background' wells been compared to results from the Reference
Sampling Program to verify that using on-base wells as representatives of natural background for the
study area is appropriate?"

APG Response: No, the data were not available at the time the Remedial Investigation was conducted.
However, the background samples that were collected were approved by the EPA for use in the risk
assessment and are upgradient in areas that were unaffected by Army activities.

(g) "Has APG considered the fact that past activities and the millions of unexploded ordnance (UXO) may
have increased the natural background levels of certain compounds making the use of on-site
concentrations for comparison unreliable (e.g., arsenic, gross beta)?

APG Response: Background samples for the Nike Site were collected from areas that are upgradient and
unaffected by past activities at the Nike Site. Therefore, they were appropriate background samples to use
in the risk assessment for comparison to site inorganic concentrations.

Comment 26: "It is the Installation Restoration Program's (IRP) consistent stance that groundwater is not
flowing off-base even though their data indicate otherwise." "APG should present clear evidence that
worse-case scenarios regarding water flow potentials towards the communities have been constructed and that,
regardless of what is encountered, the current water-treatment concept can be modified to resolve any
problems." Record of Decisions (RODs) present cost for remedial alternatives and actually rule out certain
alternatives based in projected costs. Therefore, it is important to have a clear grasp on the extent of
contamination and the major forces which will affect design since these directly affect the cost of the
operation. One design phase issue worth mentioning in these comments is that the selected alternative for
the treatment of groundwater cannot be supported by the citizens without proper chemical analysis of the
effluent of the proposed treatment process, including monitoring for chemical agent breakdown products and
radionuclides."

APG Response: It is the Army's policy to present draft data and documents at Restoration Advisory Board
meetings to provide the community with the most current information. As the data are analyzed and as
studies progress and new data are obtained, material being presented to the community may change. The
initial information on the groundwater did not indicate it was flowing off-base, and APG presented this
information to the Restoration Advisory Board. As APG's studies continued and as EPA and the U.S.
Geological Survey continued to examine the data, a small area at the northern boundary where the
groundwater flow appears to be reversing was discovered. APG immediately presented these data to the
Restoration Advisory Board and the community.

APG's design for the groundwater treatment system will be completed only after the area of affected
groundwater is fully characterized. Because the plume is close to being fully characterized, there will be
minimal impact on cost of the alternative. The type of contamination was identified in the Remedial
Investigations Report making selection of the treatment alternative feasible at this time. A bench-scale
treatability study was performed over a 2-month period on the groundwater that contained the highest
concentration of TCE from the Nike Site using reductive dehalogenation (the preferred alternative). Chemical
analyses were performed before, during, and after the study to determine the effectiveness of the treatment
technology. Reductive dehalogenation proved to completely destroy chemicals of concern. In addition, when
the treatment system is installed, water entering the system, water being treated, and final effluent will be
monitored. Substantive monitoring and reporting reguirements of an NPDES permit will be followed to ensure
the discharged water has no adverse effect on the environment.
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Comments in Undated One-page Handout Regarding Aberdeen Proving Ground's Proposed Plan

Comment 27: "Local communities could be at risk from private shallow wells which may exist. There is also a
possibility of exposure to TCE vapors in basements of homes if the plume was to migrate to the
communities." "TCE has been detected off APG property at concentrations above the acceptable level,
making the map in the PP wrong."

APG Response: Data are currently being evaluated and maps are being constructed to show the full area of
known contamination. The contaminated groundwater that exists off-post has recently been discovered and
information regarding the concentrations of TCE were not available when the Proposed Plan was written.
There are no documented residential wells in the shallow groundwater that could be affected by the off-post
contamination. Extraction wells and a pumping system will be installed to capture any contamination and
reverse the flow of the contaminated groundwater pulling it toward the base boundary, not to other
communities.

To date, the contamination off-base has very low concentrations and is small is size. Efforts are currently
being taken to find the farthest extent of the plume. The residential homes closest to the area of
groundwater receive their water supply from the county. The TCE concentrations in the groundwater are too
low to present a vapor hazard to any residents who might have basements.

Landfill

Comments dated February 28, 1996

Comment 28: APGSCC does not support capping the landfill at the present time. APGSCC recommends
APG "wait for the data to determine if capping is the best route to take, or if long-term monitoring would be
more practicable." "This citizens group would like to hear from APG and the regulatory agencies why they
believe that capping this site is the best alternative, in light of the lack of contamination, costs of the
project, and limited remedial funds for the fiscal year."

APG Response: The landfill has been fully delineated; there are no outstanding data. The Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA) process reguires that applicable or
relevant state and federal reguirements be followed when considering the type of remediation to be instituted
at a given site. Two pieces of evidence that suggest the Nike Site landfill could be a problem are the drums
that once contained hydraulic fluid found on top of the landfill and tiles containing asbestos that were
found within the landfill. Given this information, the CERCLA process and the EPA reguired that APG look at
alternatives for remediating the landfill; therefore, capping and excavation alternatives were evaluated.
Long-term monitoring is not considered remediation and could not be used as a separate remediation
alternative. Long-term monitoring can be used in conjunction with other alternatives such as institutional
controls or capping.

Capping the landfill was chosen because it is an egually effective solution and provides the same level of
risk reduction as would be achieved with excavation. Capping the Nike Site landfill is especially effective
because the waste is located above the groundwater table and the cap prevents water from infiltrating into
the waste and thus prevents unknown hazardous substances from moving out of the landfill. Given the known
information about the landfill, sufficient data have been gathered to make an informed decision regarding the
landfill.

Comment 29:

(a) "How many drums were labeled as hydraulic fluid?"

APG Response: The labels on three drums indicated they contained hydraulic fluid.

(b) "Were any or all of these drums swiped or sampled to determine their original contents?"

APG Response: Thirteen drums were rusty and empty. One additional drum contained 3 in. of bright-red
liguid. Organic vapor levels taken from the drum indicated the contents of the drum contained volatile
organics. The contents of the drum were sampled for organics and inorganics.

APG Response: Two composite surface soil samples were collected in February 1995. Composite surface
soil samples were collected from six locations at 60°-are intervals and 10 ft from center point location.

Discrete sample for volatile compounds were collected from the center points. One sample were collected
from the site of the ten toppled drums at the northwest potion of the landfill. A second soil sample was
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collected from the site of the four upright drums at the east end of the landfill. In addition, a sludge
sample of the red liquid removed from the rusted drums was collected.

(d) "What contamination was documented from such effects?"

APG Response: The contamination assessment is documented in the "Nike Missile Battery Site Removal
Actions Report," which is located in the Administrative Record. The Administrative Record is located at four
separate locations: Harford County Library, Aberdeen Branch; Harford County Library, Edgewood Branch; Kent
County, Washington College Miller Library; and the Baltimore County Department of Environmental Protection.

The soil was sampled for volatile organic compounds (VOCs), semivolatile organic compounds,
pesticides/polychlorinated biphenyls, and total metals. No contamination was detected in the samples. The
red liguid found in the drum did not indicate the presence of organics or inorganics above the detection
limits using the Toxicity Characteristic Leaching Procedure. The liquid was disposed of by APG's waste
contractor.

(e) "In addition to 25 (a single sampling point for VOCs), were any other soil samples tested for VOCs at
the landfill?"

APG Response: Yes, sample 3S was analyzed for VOCs. Sample 25 was centrally located near the drums
and 3S was taken downslope of the site. The samples did not contain VOCs above the detectable limit.
These data are available in the Remedial Investigation Report for Cluster 1 contained in the Administrative
Record.

(f) "Did the perimeter of the composite sample (25) fall outside the location of the drums?"

APG Response: The sample was taken before the drums were removed and had to be taken outside of the
location of the drums. However, 25 was taken near the drums.

(g) "What current characterization efforts are underway for this Operable Unit?"

APG Response: Two monitoring wells existed at the landfill. Additional characterization at the landfill
included push-probe sampling at 5 locations where samples were collected from multiple depths and 24
groundwater samples were collected. Installation of four 3/4-in. drive-point piezometers and installation of
eight 1-in. monitoring wells occurring during April 1996.

(h) "Have the proposed piezometer and geoprobe locations been altered since the October RAB
presentation, since these locations are too close to the landfill itself and appear to largely
neglect directions considered to be downstream by previous APG investigations?"

APG Response: Yes, the locations were altered. They were moved further from the limits of the waste in the
landfill and placed radially around the landfill in locations agreed upon by APG and the EPA.

(i) "Besides empty drums on the surface and the known disposal of asbestos, is there any historical
information suggesting significant contamination?"

APG Response: "Historical information is contained in the RCRA Facility Assessment Report (AEHA,
1990). There is no information suggesting "significant contamination".

(j) "What data supports the assumed landfill depth of 8 feet?"

APG Response: Electromagnetic and ground-penetrating radar, two types of geophysical techniques, were
used to determine the depth of the landfill.

(k) "Does any part of the landfill site below the water-table level on a seasonal or permanent basis?"

APG Response: No.

(1) "How much soil covers the actual debris in the landfill?"

APG Response: In some places there is no soil covering the debris; in other locations there is as much as 1
ft of cover.

(m) "If it is capped, what follow-up would there be?"

APG Response: There would be inspection of the cap at regular intervals to check for signs of erosion,
settlement, or invasion by deep-rooted vegetation or burrowing animals; maintenance and repair operations as
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needed such as cutting vegetation, regarding or revegetating; and installation of monitoring wells with
sampling and analysis conducted annually.

(n) "Has spontaneous detonation been considered with regards to the selected alternative?" "Can the type
of cap selected withstand and contain an explosion? If so, how large of an explosion?"

APG Response: Yes, detonation of unexploded ordnance has been considered with regard to all alternatives.
The landfill cap will be designed to contain a high explosive round and/or chemical rounds. The design of
the landfill will be based on the largest expected unexploded ordnance at the Nike Site.

Comment 30: "Due to the limited characterization of this landfill, it is not possible to assess the
protective value of capping the site." "APGSCC has had difficulty in determining if the cap will be
protective. Characterization issues remain unresolved regarding he actual contents of the landfill, and
APGSCC believes the UXOs, as well as the other contents, should be excavated. Many concerned citizens agrees
that removal of the landfill is most protective of future generations. APGSCC supports excavation in light
of the unknown contents. Capping the site will leave the site without a permanent solution, posing unknown
risks for years to come."

APG Response: As discussed in response to Comment 28, capping the landfill was chosen because it is an
egually effective solution and provides the same level of risk reduction as would be achieved with
excavation. Capping of the Nike Site landfill is especially effective because the waste is located above the
groundwater table and the cap prevents water from infiltrating into the waste and prevents hazardous
substances from moving out of the landfill. In addition, further characterization of the landfill such as
intrusive work including drilling or digging through the landfill was not approved by the EPA. Therefore,
given the known information about the landfill, sufficient data have been gathered to make an informed
decision regarding capping the landfill.

Comment 31: "The originally selected alternative for remediating this site was the telerobotic excavation
alternative. In addition to permanence and long-term effectiveness, a major reason for the original
selection was the fact that MDE guidelines reguire excavation of landfills less than two acres in area. The
most recent PP should address this issue, and explain why the MDE guidelines are not going to be followed.
Furthermore, APGSCC is interested in why the selected alternative was changed."

APG Response: Through information searches and discussions with MDE, it was determined there is no law,
regulation, or guideline that reguires landfills that are less than 2 acres in area to be excavated. MDE
allows site closure alternative be proposed on a site-by-site basis. MDE allows either excavation or capping
to be considered, regardless of the size. Therefore, through further evaluation using the nine criteria it
was determined capping the landfill is the best solution.

Comment 32: "A review of the information in the RI/FS did not turn up any contaminants at concentrations
believed to be a concern at the site. This conclusion, however, is based on limited data since sampling of
soil and groundwater was limited. While the data collected there has not uncovered a problem, it is not
clear that it is comprehensive enough to determine that there isn't any contamination. We are confused by
the fact that contamination has not been found at the SW Landfill to date, yet the IRP intends to place an
impermeable cap over the landfill which is estimated to cost 1.4 million dollars."

APG Response: It was determined by APG and EPA that the sampling at the landfill was sufficient for
characterization. Soil, surface waster, and groundwater sampled were collected. See Comment 29 for more
details. Because contamination was not found in soil on top of the landfill or in groundwater around the
landfill does not mean there is not waste in the landfill that could cause a problem in the future if no
action is taken.

Sanitary Sewer System

Comments Dated February 28, 1996

Comment 33: APGSCC supports the selected alternative, assuming the Lauderick Creek Study Area
permanently remains the property of the U.S. Army. "APGSCC has raised various concerns regarding the
integrity of the system, the potential for the sewer system to contaminate the surrounding soil during
blasting, the permanence of excavation, and how it may be easier to remove the system now instead of twenty
years down the road when it is being returned to civilian ownership. These issues do not concern APG and
their intention to leave the system in place has not changed. In response, APGSCC strongly urges APG to
explore routes to ensure that this property is not returned to private ownership." APGSCC expressed a
concern that "in a future residential land-use scenario, the risk of cancer and non-cancer health outcomes
are above acceptable guidelines for the adult based on the RI/FS calculations, as well as above regulatory
limits for children based on our calculations (Attachment I).
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APG Response: There are many man-made features at the Nike Site (such as the missile silos) that will be
remaining in place along with the sewer system. If the land were to be turned over, which the Army does not
foresee, these features would be handled at that time. Cleaning and closing the sanitary sewer system in
place effectively removes any risks associated with the substances that currently remain in the system, and
the flowable fill will ensure the structural integrity. Because of the concerns raised by APGSCC and
further evaluation of the solution of closing the sanitary sewer system in place, APG will be performing a
camera survey of the piping system to ensure its integrity before proceeding.

Comment 34: APGSCC has asked why this action is part of the Proposed Plan as opposed to being
conducted as a removal action.

APG Response: The sewer system could have been dealt with as a removal action; however, it would still
have to be brought to closure by presenting it in the Proposed Plan.

Comment 35: "APGSCC is concerned with leaving this system in place. APGSCC believes such sources
should be removed, when possible. It is guite possible that parts of APG will be returned to civilian
ownership in the future, so citizens should have a significant part in deciding if such operable units are
removed or left behind. Excavation of this site would allow APG to assess if the soil beneath the system is
contaminated and in need of remediation."

APG Response: Soil sampling and soil gas survey did not detect or show any indication of contamination
outside of the piping system. APG agrees the citizens should have a part in deciding which remediation
alternative will be chosen. Because of concerns regarding the structural integrity of the piping system, the
sewer system will be surveyed to ensure the system is intact and cleaning and closing the system in place
will be the most appropriate solution for this problem.

Missile Silos

Comments Dated February 6, 1996, and February 28, 1996

Comment 36: "APGSCC supports the interim removal action being accepted as a permanent action."
APGSCC has the same concerns regarding long-term ownership as discussed above on the sanitary sewer
system. APGSCC feels monitoring should be conducted around the silos to ensure the actions taken by the
Army continue to be effective.

APG Response: Long-term monitoring of this area is already proposed in conjunction with the groundwater
cleanup alternative.

Miscellaneous

Comments Dated February 28, 1996

Comment 37: APGSCC has objected of ordnance cleanup being handled as a removal action instead of being
part of the Proposed Plan and has submitted guestions regarding this project.

APG Response: APG acknowledges APGSCC's objectives to the ordnance cleanup being handled as a
removal action. APG will be issuing an Engineering Evaluation/Cost Analysis for this removal action, which
is similar to a Proposed Plan. At the end of the public comment period on this document, APG will prepare a
Responsiveness Summary, similar to this document. The Responsiveness Summary will respond to guestions on
the ordnance removal action.

Comment 38: "APG stated that EPA's acceptable risk for cancer is 1 in ten-thousand to 1 in one-million.
What is the reference for this range? Is one more appropriate than the other depending on the scenario (i.e.
industrial vs. residential setting)?"

APG Response: The reference for the EPA document that discusses the target risk range of 1 x 10-6 to 1 x
10-4 is USEPA 1991, Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions,
OSWER Directive 9355.0-30, April 2, 1991. The document states that "EPA uses the general 1 x 10-6 to 1
- 10-4 risk range as a 'target range' within which the Agency strives to manage risks as part of a Superfund
cleanup process. This risk range is not specific to a particular type of exposure scenario (i.e.,
residential or industrial). The EPA risk manager of the site made the ultimate decision as to what the
target risk is for the site.

Comment 39: "Will creek data be reviewed and strengthened during future remedial efforts in the Lauderick
Creek Study Area, or is this the total extent to which APG plans to investigate Monks Creek? How can APG
feel confident that the few detected localized hot spots mentioned in this section represent most of the
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contamination in these surface water bodies? Doesn't it seem quite possible that many more contaminated
sites exist in Lauderick and Monks creeks but were missed due to limited sampling sites in these
tributaries?"

APG Response: Sampling of streams and tributaries was conducted in conjunction with possible contaminant
sources. The Remedial Investigations was designed to identify and define hot spots. The risk assessment
determined there was no unacceptable risk; therefore, there is no justification for further sampling.

Comment 40: "The nine criteria are divided into three groups: threshold criteria, primary balancing
criteria, and modifying criteria. This terminology is new to us and we would like to show what agency
devised this approach, and why this change was made.

APG Response: The nine criteria are divided into three groups in accordance with the EPA Guidance for
Conducting Remedial Investigations and Feasibility Studies under CERCLA and the EPA Proposed
Plan/Record of Decision Guidance Document. There has been no change in the evaluation criteria; they have
just been grouped in accordance with EPA requirements. The EPA Proposed Plan/Record of Decision
Guidance Document states the following regarding the three groups:

The nine criteria are categorized into three groups: threshold criticism primary balancing
criteria, and modifying criteria. The threshold criteria must be satisfied in order for an
alternative to be eligible for selection. The primary balancing criteria are used to weigh major
tradeoffs among alternatives. Generally, the modifying criteria are taken into account after public
comment is received on the Proposed Plan.

Comment 41: "What was the logical basis for discontinuing testing for explosives after two rounds of
sampling? Was this approach taken for all the different types of media sampled? Were various media
samples tested for degradation products of explosives? Were various media samples tested for degradation
products of explosives? Were various media samples tested for chemical agents and their degradation
products?"

APG Response: If explosives were not found after two rounds of sampling that were conducted quarterly,
testing was discontinued. This approach was taken for groundwater samples that were sampled in two
rounds. Samples were taken for degradation products of explosives. Samples were also taken for mustard
and their breakdown products.

Comments Dated January 31, 1996

Comment 42: APGSCC submitted comments regarding the risk calculations contained in the Nike Site risk
assessment including comments on why additional calculations were not performed for children, particularly
under the future-use scenario, and why additional possible exposure pathways were not included.

APG Response: The exposure pathways that were evaluated in the Nike Site risk assessment were selected
based on the likelihood they would account for the greatest risks at the site. The selection of the most
important pathways was based on an understanding of which pathways are typically of most concern in risk
assessments and on having evaluated other pathways for other assessments (e.g., ingestion of game) and
knowing they would not likely drive risks in the Nike Site risk assessment. In addition, it should be noted
the pathways evaluated in the Nike Site risk assessment were approved by EPA Region III, indicating the
estimation of the most significant pathways was appropriate.

It is recognized that risks to other receptors could occur at the Nike Site (especially under hypothetical
future land use conditions); however, as noted above, instead of evaluating all possible pathways through
which individuals could be exposed to chemicals of potential concern, the pathways through which the greatest
risks could occur were evaluated. It should be noted the final conclusions of the risk assessment (i.e.,
groundwater is contaminated with chemicals that would result in unacceptable risks if consumed by
hypothetical future residents) would not change if other exposure pathways had been evaluated.

COMMENTS FROM NEIGHBORS INVOLVED IN THE COMMUNITY OF EDGEWOOD

Representatives of the community group (NICE) submitted questions and comments to APG through a
letter from their President and through individual comments. The comments from the six individuals
indicated five preferred treatment by air stripping and one preferred treatment in place using reductive
dehalogenation. Five preferred telerobotic excavation and off-site disposal as the remedy for the landfill,
and one individual preferred the composite cap be installed. Cleaning and excavating the sewer system was
selected by five individuals, and one individual agreed with the preferred alternative of closing the sewer
system in place. The individual who preferred closing the system in place noted "this ground could never
become civilian property because of the ground's history and uncertainty of content." Five individuals
agreed no further action was needed for the former missile silos, and one individual indicated no preference.
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The following is a summary of other comments and questions from NICE.

Groundwater

Comment 43: Prefer air stripping as treatment method.

APG Response: All of the treatment alternatives were known to be equally effective in treating the water at
the Nike Site. A treatment study was conducted for the preferred alternative, reductive dehalogenation,
which showed that reductive dehalogenation would be effective in treating the groundwater. Air stripping
does not break down the TCE; it merely transfers the TCE to another media such as a carbon filter. The
filter must then be handled as waste. Reductive dehalogenation, however, completely breaks down the TCE into
nontoxic compounds and does not produce any sludge or by-products. Reductive dehalogenation is also easy to
operate.

Landfill

Comment 44: Army has no idea what is in the landfill; landfill is a hazardous waste landfill and may also
contain unexploded ordnance. Since the Army does not know what is buried at this site, there is no way of
knowing if this site contains other hazardous waste that will potentially cause further contamination of the
groundwater.

APG Response: The available information about the landfill indicates construction debris was disposed of at
the site. However, 14 drums were found on top of the landfill, and tiles containing asbestos were found
within the landfill. As part of the remedial investigation of the landfill, groundwater, sediment, surface
water, and soil samples were collected. The analytical results identified no hazardous waste leaching from
the landfill. Because the landfill is more than 40 years old, any leaching from containers would have begun
by now. Capping the landfill will eliminate infiltration of water into the landfill, which will prevent
unknown hazardous substances from moving out of the landfill.

The landfill cap will be designed to contain a high explosive round and/or chemical rounds. The design of
the landfill will be based on the largest expected unexploded ordnance at the Nike Site.

Comment 45: Original plan called for excavation of the landfill and off-site disposal.

APG Response: APG is trying to be as responsive as possible to citizens' requests for information and thus
supplies draft documents to the public. These are, however, draft documents that are still being reviewed
within the Army and by regulators; information may change by the time a final document is issued. This
occurred with the draft Proposed Plan.

As discussed in response to Comment 28, capping the landfill as chosen because it is an equally effective
solution and provides the same level of risk reduction as would be achieved with excavation. Capping of the
Nike Site landfill is especially effective because the waste is located above the groundwater table and the
cap prevents water from infiltrating into the waste, thus preventing hazardous substances from moving out of
the landfill.

Comment 46: Army is placing economic considerations above the health and safety of residents.

APG Response: Protection of human health and the environment is the first criteria any cleanup method must
meet; cost only becomes a factor after alternatives are shown to be equally effective.

Comment 47: Landfill was not a planned facility.

APG Response: The landfill was not a "permitted" facility because permits for landfills were not issued in
the 1950s.

Comment 48: TCE is leaching toward water sources that lead into nearby streams that feed the Chesapeake
Bay.

APG Response: The RI sampling did not detect TCE in the groundwater at the landfill location. It is not
leaching from the landfill, and it was not detected in streams. The groundwater contaminated with TCE is
located at the Missile Silo area. The groundwater will be cleaned up without an impact on any streams or the
Chesapeake Bay.

Comment 49: Several wells that provide drinking water to residents of the area are within one mile of the
facility.

APG Response: A well survey was conducted in the winter of 1993. The survey identified two wells in
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Edgewood near the Nike Site boundary. Only one the wells, on Freys Road, is used for drinking. These
wells could not be impacted by the contaminated groundwater as they are too far away and too shallow. In
addition, the contaminated groundwater will be cleaned up using extraction wells that will be placed to
capture the contaminated groundwater and reverse the flow of groundwater to the Base boundary.

Comment 50: If the landfill is capped, there is no way for the site to be used for future development.

APG Response: The Army has no plans to release the site for future development. With existing technology
limitations, APG could not declare the site free of unexploded ordnance, even after the proposed clearance.
Therefore, any future plans for uses of the site would be very speculative.

Comment 51: The cost of $1.6 million for capping the landfill does not take into account that the Army will
need to monitor this site for 20 to 30 years.

APG Response: The costs for monitoring for 30 years are included in the $1.4 million to $1.6 million
estimated cost of installing the landfill cap.

Comment 52: If during the monitoring period, waste from the landfill is found to be causing further
contamination, the Army will have to excavate the site, potentially causing many times the 10 million dollar
estimate at this time.

APG Response: Capping the landfill will effectively eliminate the route of migration from the landfill to
the groundwater by stopping infiltration of water. Therefore, it is highly unlikely the groundwater will
become contaminated from the landfill. If this were to happen, the landfill would not be excavated; the
groundwater would be treated.

Sewer system

Comment 53: Prefer sewer system be excavated.

APG Response: Cleaning and closing the sewer system in place effectively removes any risks associated with
the substances that currently remain in the system. The procedure also is in accordance with industry
standards for the closure of sewer systems.

Unexploded Ordnance

Comment 54: Opposes decision to handle as removal action; believe the U.S. Army needs to be held
accountable to an outside agency, preferably the EPA.

APG Response: The removal action will be conducted under CERCLA. EPA has oversight of all CERCLA
actions, both removal and remedial.

Comment 55: Strongly encourage the investigation of all anomalies, regardless of their depth below the
surface, and safe removal of all UXO from the facility. Strongly oppose any open detonation of recovered
rounds, particularly in the "boundary area."

APG Response: Each metallic anomaly will be detected and investigated by the best technology available.

APG agrees open denotation near the boundary is undesirable. Open detonation is always a last resort. The
first preference is to move and store the item. The second choice, if the item is not safe to store, is to
move the item to a remote, approved location and detonate the item there. The last alternative, detonation
in place, is used only when an item cannot be moved without risking the lives of the ordnance experts
handling the item. At the present time, detonation in place is the only option when a unexploded ordnance
cannot be moved. For the removal action, APG is looking at ways to mitigate to the greatest extent possible
any impacts to the community. Any other necessary protective actions also would be taken.

Comment 56: Current infrastructure could not support an evacuation.

APG Response: For the removal action, an evacuation is highly unlikely. The most likely protective action
would be to shelter in place for a very brief time. It is also possible a small portion of the community
might occasionally be asked to evacuate for a short time. An evacuation would be planned and therefore could
be done without changes to the current infrastructure. APG is working with the Harford County Department of
Emergency Operations in preparing a response plan for the project. It is recognized that an extensive
community information and education effort will be needed.

COMMENTS FROM MR. JAMES GAIBROIS
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Comment 57: Mr. Gaibrois questioned why there were substantial differences in the length of time it would
take to clean up the groundwater under the different alternatives.

APG Response: The cost shown for in-place reductive dehalogenation is the total estimated cost to install
and operate the system for 60 years. This alternative employs a technology that is installed below ground
(in situ) to treat the groundwater in place. The groundwater is treated as it flows through the iron media.
The other technologies extract the groundwater and treat it above ground. Extracting the groundwater at
various locations in the plume allows a larger area of the plume to be treated at one time. This decreases
the distance the TCE must move to be treated and, therefore, decreases the amount of time it takes to treat
the plume to concentrations below the EPA required limits. This is why the in situ technology has an
estimated time for cleanup of 60 years and the other pumping and treatment technologies require only 15
years.

Comment 58: Mr. Gaibrois questioned whether the cost estimates included costs for any possible law suits or
road improvements.

APG Response: Costs were considered for just activities associated with the remedial actions; therefore, law
suits were not included in the cost estimate. Road improvements are not needed and, therefore, not included.

Comment 59: Mr. Gaibrois stated the cost figures should use worse case scenarios so adequate funding
would be allocated for the project and to prevent delays from having to request additional funding.

APG Response: The EPA requires cost estimates in the Proposed Plan to be within +50 and -30%. These
cost estimates were conducted in accordance with these requirements. A more detailed cost estimate will be
performance during the remedial design phase.

Comment 60: Mr. Gaibrois questioned the use of present worth in estimating the cost of the alternatives. He
also questioned whether federal government procurement staff reviewed the cost estimates presented in the
Proposed Plan and whether the cost estimates shown are adequate for contracting purposes.

APG Response: The EPA requires that present worth be calculated for each alternative. These costs are used
for comparing one alternative to another. They are not used for contracting purposes.

Comment 61: Mr. Gaibrois questioned some of the assumptions used in the cost estimates, including general
installation support costs and operation and maintenance costs. Mr. Gaibrois also questioned why there are
costs shown for the no action alternative.

APG Response: All items included in the cost estimate are required for the remedial actions. The final cost
estimate, provided with the remedial design, will be more detailed and accurate. The no action alternative
can include sampling for any contaminants left in place to monitor possible movement.
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4. REFERENCES

Code of Federal Regulations (CFR), 1995. Labor, 29 (various parts).

CFR, 1995. Protection of Environment, 40 (various parts).

Code of Maryland Regulations (COMAR), 1995. Title 26, Department of the Environment (various subtitles).

Environmental Protection Agency (EPA) , 1989a. Risk Assessment Guidance for Superfund.
Volume I: Human Health Evaluation Manual. Part A. Interim Final, EPA/540/1-89/002.

EPA, 1989b. Exposure Factors Handbook. Office of Health and Environmental Assessment, Washington, B.C.

EPA, 1991. Risk Assessment Guidance for Superfund. Volume 1: Human Health Evaluation
Manual Supplemental Guidance. Standard Default Exposure Factors. Interim Final, OSWER
Directive 9285.6-03, Washington, D.C.

EPA, 1992. Guidelines for Exposure Assessment. Federal Register, 57:22888-22938.

EPA, 1994. Selecting Exposure Routes and Contaminants of Concern by Risk-Based Screening.
Region III Technical Guidance Manual, Risk Assessment. EPA/903/R-93-001, Hazardous Waste
Management Division, Office of Superfund Programs, Region III, Philadelphia.

U.S. Army Corps of Engineers (USAGE), 1993a. Environmental Assessment for the Proposed Removal
Action at the Six Nike Missile Silos.

USAGE, 1993b. Remediation of the Six Nike Missile Silos at Edgewood Area, APG, Maryland.

USAGE, 1994. Remedial Investigation and Feasibility Study, Cluster 1, Edgewood Area, APG, Part I:
Remedial Investigation.
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