PB97-964401
EPA/541/R-97/111
January 1998
EPA Superfund
Record of Decision:
Ellsworth Air Force Base, OU 11
Ellsworth Air Force Base, SD
4/28/1997
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Final
Record of Decision for
Remedial Action at Operable Unit 11
Ellsworth Air Force Base, South Dakota
United States Air Force
Air Combat Command
Ellsworth Air Force Base
April 1997
AF Project No. FXBM 94-7002
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Final Record of Decision Operable Unit 11
Ellsworth Air Force Base, South Dakota
TABLE OF CONTENTS
Chapter page
1.0 DECLARATION FOR THE RECORD OF DECISION (ROD) 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 SELECTED REMEDY l-l
1.5 STATUTORY DETERMINATION 1-2
1.6 SIGNATURE AND AGENCY CONCURRENCE ON THE REMEDY 1-3
2.0 DECISION SUMMARY 2-1
2.1 SITE NAME AND LOCATION 2-1
2.2 OU-11 DESCRIPTION/HISTORY AND REGULATORY OVERSIGHT ACTIVITIES
2-1
2.2.1 EAFB Description/History 2-1
2.2.2 OU-11 Site Description/History , 2-1
2.2.3 EAFB Hydrogeology 2-3
2.2.4 Regulatory Oversight Activities 2-4
2.3 HIGHLIGHTS OF COMMUNITY PARTICIPATION 2-4
2.4 SCOPE AND ROLE OF RESPONSE ACTION 2-6
2.5 SITE CHARACTERISTICS 2-6
2.5.1 Distribution of Contaminants 2-7
2.6 SITE RISK SUMMARY 2-8
2.6.1 Human Health Risks 2-8
2.6.2 Risk Assessment Process 2-9
2.6.3 Exposure Assessment 2-9
2.6.4 Toxicity Assessment 2-10
2.6.5 Basewide Ecological Risk Assessment 2-11
2.6.6 Risk Assessment Conclusions 2-12
2.7 DESCRIPTION OF ALTERNATIVES . 2-12
2.7.1 Area 1 Alternatives ! 2-13
2.7.2 Area 2 Alternatives 2-18
2.8 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES 2-23
2.8.1 Overall Protection Of Human Health And The Environment 2-25
2.8.2 Compliance With ARARs 2-26
2.8.3 Long-term Effectiveness And Permanence 2-27
2.8.4 Reduction Of Toxicity, Mobility, Or Volume Through Treatment 2-28
2.8.5 Short-Term Effectiveness 2-29
2.8.6 Implementability 2-29
2.8.7 Cost 2-30
2.8.8 State Acceptance 2-34
2.8.9 Community Acceptance 2-34
2.9 SELECTED ALTERNATIVE 2-34
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Final Record of Decision Operable Unit 11
Ellsworth Air Force Base, South Dakota
2.10 STATUTORY DETERMINATIONS 2-38
2.10.1 Protection of Human Health and the Environment 2-38
2.10.2 Compliance with ARARs 2-39
2.10.3 Cost Effectiveness 2-39
2.10.4 Utilization of Permanent Solutions and Alternative Treatment Technologies to
the Extent Possible 2-40
2.10.5 Preference for Treatment as a Principal Element 2-42
2.11 DOCUMENTATION OF SIGNIFICANT CHANGES 2-42
3.0 LIST OF ACRONYMS AND ABBREVIATIONS 3-1
APPENDICES
Appendix A Figures
Appendix B Tables
Appendix C Responsiveness Summary
LIST OF FIGURES
Figure 1 Area Location Map
Figure 2 Site Location Map
Figure 3 Area 1 - Area of Attainment
Figure 4 Area 2 - Area of Attainment, On-Base BG04 Area
Figure 5 Area 2 - Area of Attainment, On-Base BGOS Area
Figure 6 Area 2 - Area of Attainment, Off-Base BG04/BG05 Areas
Figure 7 Distribution of TCE in On-Base Ground Water
Figures Distribution of TCE in Off-Base BG04/BG05 Ground Water
Figure 9 Distribution of DCE, PCE, TCE in Off-Base BG04/BG05 Ground Water
LIST OF TABLES
Table 1 OU-11 Study Areas - Summary
Table 2 Area 1 and Area 2 Exposure Point Data
Table 3 Summary of Site Risks for Area 1 (South Docks)
Table 4 Summary of Site Risks for Area 2 (BG04/BG05)
Table 5 Evaluation of Federal and State ARARs
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Final Record of Decision Operable Unit 11
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1.0 DECLARATION FOR THE RECORD OF DECISION (ROD)
1.1 SITE NAME AND LOCATION
Operable Unit 11 (OU-11), Basewide Ground Water, Ellsworth Air Force Base (EAFB),
National Priorities List (NPL) Site.
• Meade and Pennington Counties, South Dakota
1.2 STATEMENT OF BASIS AND PURPOSE
This decision document describes EAFB's selected remedial action for OU-11, 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 the National Oil and Hazardous Substances Pollution Contingency Plan (NCP).
This decision is based on the contents of the Administrative Record for OU-11, EAFB. The
U. S. Environmental Protection Agency (EPA) and the South Dakota Department of
Environment and Natural Resources (SDDENR) concur with the selected alternative.
13 ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from OU-11, 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.
1.4 DESCRIPTION OF SELECTED REMEDY
Twelve operable units have been identified at EAFB. This ROD is for a remedial action at
OU-11 and is the 14th ROD for EAFB.
OU-11 has been divided into two areas to aid in project planning. Area 1 is the South Docks
Study Area, and Area 2 is the BG04 and BGOS Study Areas.
The selected alternative for Area 1, Ground-Water Extraction and Treatment with Containment,
includes the following major components:
• Ground-water removal and treatment in the South Docks Study Area.
• On-Base containment of ground water containing contaminants at concentrations above
Federal Maximum Contaminant Levels (MCLs) and State of South Dakota Ground-
Water Quality Standards.
• Institutional controls and long-term monitoring.
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The selected alternative for Area 2, Ground-Water Containment/Extraction and Treatment,
includes the following major components:
• Ground-water removal and treatment along the northeast Base boundary and at areas of
high contaminant concentrations on-Base.
• Natural attenuation of low contaminant concentration areas, primarily off-Base.
• Alternative water supply to residents affected by contamination coming from the Base.
• Additional investigation to determine the eastern extent of off-Base ground-water
contamination.
• Institutional controls and long-term monitoring.
Collectively, the selected remedies for Area I and Area 2 constitute the entire remedial action for
OU-llatEAFB.
1.5 STATUTORY DETERMINATION
The selected remedies are protective of human health and the environment, comply with Federal
and State of South Dakota requirements that are legally applicable or relevant and appropriate to
the remedial action, and are cost-effective. These remedies utilize permanent solutions and
alternative treatment technologies, to the maximum extent practicable for OU-11. These
remedies satisfy the statutory preference for treatment as a principal element
A review will be conducted at least every five years after signing the ROD to ensure that the
selected remedies continue to provide adequate protection of human health and the environment.
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1.6 SIGNATURE AND AGENCY CONCURRENCE ON THE REMEDY
BRETT M. DULA Date
Lieutenant General, USAF
Vice Commander
Max H. Dodson Date
Assistant Regional Administrator
Office of Ecosystems Protection and Remediation
U.S. Environmental Protection Agency Region 8
NETTIE H. MYERS, Secretary Date
Department of Environment and Natural Resources
State of South Dakota
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Final Record of Decision Operable Unit 11
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1.6 SIGNATURE AND AGENCY CONCURRENCE ON THE REMEDY
BRETT M. DULA Date
Lieutenant General, USAF
Vice Commander
Max H. Dodson Date
Assistant Regional Administrator
Office of Ecosystems Protection and Remediation
U.S. Environmental Protection Agency Region 8
NETTIE H. MYERS^eofetary Date
Department of Environment and Natural Resources
State of South Dakc
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2.0 DECISION SUMMARY
2.1 SITE NAME AND LOCATION
EAFB is a U. S. Air Force Air Combat Command (ACC) installation located 12 miles east of
Rapid City, South Dakota, and adjacent to the small community of Box Elder (Figure 1).
EAFB covers approximately 4,858 acres within Meade and Pennington Counties'and includes
runways and airfield operations, industrial areas, and housing and recreational facilities
(Figure 2). Open land, containing a few private residences, lies adjacent to EAFB on the north,
south, and west, while residential and commercial areas lie to the east of the Base.
2.2 OU-11 DESCRIPTION/HISTORY AND REGULATORY OVERSIGHT
ACTIVITIES
2.2.1 EAFB Description/History
EAFB was officially activated in July 1942 as the Rapid City Army Air Base, a training facility
for B-l 7 bomber crews. It became a permanent facility in 1948 with the 28th Strategic
Reconnaissance Wing as its host unit. Historically, EAFB has been the headquarters of
operations for a variety of aircraft, as well as the Titan I Intercontinental Ballistic Missile, and
the Minuteman I and Minuteman II missile systems. The Air Force has provided support,
training, maintenance, and/or testing facilities at EAFB. Presently, the 28th Bombardment Wing
(B-1B bombers) is the host unit of EAFB.
2.2.2 OU-11 Site Description/History
The OU-11 areas of investigation, indicated on Figure 2 and Table 1, are defined in this report
as:
• The Basewide Ground-Water Study
• The Basewide Ecological Evaluation
• The area surrounding well MW93BG04 (BG04)
• The area surrounding well MW93BG05 (BG05)
• . Upgradient of OU-6, near well MW930602
• The South Docks Area
• The northern edge of OU-12
• Additional investigations at OU-7
• The Pond 003 Area
• Ground water at OU-8
The Basewide Ground-Water Study listed above was a study of the overall ground-water quality
and characteristics. This study is presented in the OU-11 Remedial Investigation Report. The
remainder of the areas listed above were investigated as part of OU-11 to fill ground-water data
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gaps that remained after completion of the investigations at the other 11 OUs at EAFB, or to
further investigate areas of isolated contamination.
Based on the risk assessment and an evaluation of the data collected as part of the Basewide
Ground-Water Study and the studies of the additional areas listed above, it was determined that
three areas warrant remediation as follows: the area surrounding well BG04, the area surrounding
well BG05, and the South Docks Study Area. In addition, long-term monitoring.is needed for
the ground water at OU-8. The other areas investigated (upgradient OU-6, northern edge of OU-
12, OU-7 [additional investigation], and the Pond 003 area) did not warrant remediation because
no potential chemicals of concern (COCs) were detected or because only isolated occurrences of
low concentrations of potential COCs were detected. Areas that do not warrant remediation are
not discussed in this ROD. Detailed information on the investigation of these areas can be found
in the OU-11 remedial investigation and feasibility study (RI/FS) reports and specific OU
reports.
To facilitate project planning, OU-11 has been divided into two parts, Area 1 and Area 2. Area 1
is the South Docks Study Area. Area 1 includes the South Docks and areas of ground-water
contamination in OU-9 that were deferred to OU-11. Ground-water contamination at OU-10 was
also deferred to OU-11 for remediation; however, ground-water contamination at OU-10 is the
result of petroleum product releases and will be addressed through the State of South Dakota
Petroleum Release Program. Contaminated ground water in Area 1 lies entirely on-Base.
Remedial alternatives for these areas are collectively referred to as "South Docks" alternatives
since the South Docks area is the primary area of contamination in Area 1. Area 2 is the areas
around wells BG04 and BGOS, which includes areas where ground-water contamination has been
found to leave the Base along the eastern boundary. Area 2 will be referred to as the
BG04/BG05 Study Area. The long-term monitoring of the ground water at OU-8 will be
performed separately from the Area 1 and Area 2 remedial actions.
2.2.2.1 Areal
South Docks Study Area
The South Docks Area is located in the central part of the Base between OU-9, OU-10, and the
flightline area. Buildings of interest in this general vicinity include the Pride Hangar and hangars
in Rows 20, 30,40, and 50.
Historical aerial photographs indicate that the Pride Hangar and the hangars in the South Docks
Area have been in place since the late 1940s to early 1950s. Historically, the hangars have been
used for docking and maintenance of aircraft. The Pride Hangar is now used for storage and
maintenance of missile-support equipment and for offices and meeting rooms. In 1992, several
underground storage tanks (USTs) were removed at the Pride Hangar. Hangars in the South
Docks are now used for storage and maintenance of various support equipment, including aircraft
refueling vehicles, fire-fighting vehicles, grounds-keeping equipment, and periodic parking for
aircraft.
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Other potential sources in the area include industrial waste lines, equipment wash racks, and
historical chemical handling and disposal practices. However, no specific incidents of hazardous
material spills have been documented.
2.2.2.2 Area 2
BG04 Study Area
The BG04 Study Area is located in an open area at the northeast edge of EAFB, approximately
1,500 ft south of the explosive ordnance disposal (EOD) debris burial area perimeter (OU-8).
There are no known sources of contaminants in the immediate vicinity of BG04. A firing range
is located approximately 1,200 ft to the northwest and a housing tract is located approximately
800 ft to the east of monitoring well MW93BG04.
BG05 Study Area
The BG05 Study Area is located in a housing area in the east-central portion of EAFB,
approximately 300 ft east of LeMay Boulevard and continues off-Base to the east. There are no
known sources in the immediate vicinity of well BG05.
2.2.23 Ground Water at OU-8
Ground water at OU-8 was evaluated as part of OU-11. Ground-water remediation is not
warranted in this area; therefore a detailed analysis of alternatives was not conducted for ground
water at OU-8. However, to comply with State landfill closure requirements, compliance
monitoring will be implemented to verify that chemical concentrations in the ground water do
not pose unacceptable risk. Compliance monitoring at OU-8 will have an associated cost and
will consist of installation of monitoring wells and sampling and analysis of ground water. At
this time, OU-8 is the only area that does not require remediation that is specifically selected for
compliance monitoring; however, during development of the ~)U-11 long-term ground-water
monitoring plan, additional areas may be identified where long-term monitoring is required to fill
existing data gaps.
2.2.3 EAFB Hydro geology
A shallow unconfmed aquifer has been identified at depths of 10 feet to 50 feet beneath the
ground surface at EAFB. The shallow unconfmed aquifer at EAFB is considered a Federal Class
II-B (potential source of drinking water) aquifer and potentially a Class II-A (discharge to
surface water) aquifer (EPA, 1986). The ground water is also classified as having a beneficial
use as a drinking water supply suitable for human consumption according to State of South
Dakota (State) rules (ARSD Chapter 74:03:15, Groundwater Quality Standards).
Deep bedrock aquifers also exist beneath EAFB. These deep aquifers are separated from the
shallow aquifer by 800 feet of low-permeability clays and silts; therefore, these aquifers are not
areas where contamination will exist. In the past, EAFB used these deeper aquifers for its water
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supply. Presently, EAFB obtains its potable water from the Rapid City Municipal Distribution
System.
2.2.4 Regulatory Oversight Activities
Environmental investigation activities at EAFB were initiated by the Air Force in 1985 through
an Installation Restoration Program (IRP) Phase I Installation Assessment/Records Search and
Phase II, Confirmation/Quantification. The Phase I study, dated September, 1985, identified a
total of 17 locations at EAFB where releases involving hazardous substances potentially
occurred.
In Phase II of the IRP investigation, field activities included soil vapor surveys, geophysical
surveys, surface and subsurface soil sampling, ground-water sampling, ground-water hydrologic
testing, and ecological investigations.
On August 30, 1990 (55 Federal Register 35509), EAFB was listed on the EPA's National
Priorities List (NPL). A Federal Facilities Agreement (FFA) was signed in January 1992 by the
Air Force, EPA, and the State of South Dakota, and went into effect on April 1, 1992. The FFA
establishes a procedural framework and schedule for developing, implementing, and monitoring
appropriate response actions for EAFB in accordance with CERCLA, as amended by SARA, and
the NCP. It also sets out the oversight procedures for EPA and the State to ensure Air Force
compliance with the specific requirements. The FFA identified 11 site-specific OUs and a Base-
wide ground-water OU, which is OU-11. The Base-wide ground-water OU, is primarily used to
address contaminated ground water that was not addressed during the investigation of a site-
specific OU.
Listing on the NPL and execution of the FFA required the U.S. Air Force to perform a remedial
investigation/feasibility study (RI/FS) to investigate the 12 operable units. During 1993 through
1996, an extensive Rl field program was conducted to characterize conditions at OU-11. The
program included: a soil vapor survey, geophysical survey using electromagnetics, drilling and
sampling of boreholes, installation of monitoring wells, slug testing of monitoring wells, ground-
water sampling, geotechnical analysis of soil samples, ecological evaluation, assessment of
human health risks, arid review and compilation of previous IRP investigations. Collection and
laboratory analysis of soil, ground-water, and sediment samples were included in the Rl field
program.
23 HIGHLIGHTS OF COMMUNITY PARTICIPATION
Community relations activities that have taken place at EAFB to date include:
• FFA process - After preparation of the FFA by the US AF, EPA, and SDDENR, the
document was published for comment. The FFA became effective April 1, 1992.
• Administrative Record - An Administrative Record for information was established in
Building 8203 at EAFB. The Administrative Record contains information used to
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Final Record of Decision Operable Unit 11
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support USAF decision-making. All the documents in the Administrative Record are
available to the public.
• Information repositories - An Administrative Record outline is located at the Rapid
City Library (public repository).
• Community Relations Plan (CRP) - The CRP was prepared and has been accepted by
EPA and the State of South Dakota and is being implemented. This plan was updated in
1996.
• Restoration Advisory Board (RAB) - The RAB has been formed to facilitate public
input in the cleanup and meets quarterly. In addition to USAF, EPA, and South Dakota
oversight personnel, the RAB includes community leaders and local representatives
from the surrounding area.
• Mailing list • A mailing list of all interested parties in the community is maintained by
EAFB and updated regularly.
• Fact sheet - A fact sheet describing the status of-the IRP at EAFB was distributed to the
mailing list addressees in 1992. A remedial design fact sheet was distributed in October
1996.
• Open house - An informational meeting on the status of the IRP and other
environmental efforts at EAFB was held on May 6, 1993. An open house format was
also used during the November 16,199S Restoration Advisory Board meeting. In
addition, during 1996 the Air Force has met with community members numerous times
to inform them about ongoing investigations at OU-11.
• Newspaper articles - Articles have been written for the Base newspaper regarding IRP
activity.
• Proposed Plan - The proposed plan on this action was distributed to the mailing list
addressees for the.'r comments.
A public comment period was held from February 10 to March 12,1997, and a public meeting
was held on February 19, 1997. At this meeting, representatives from EAFB answered questions
about the remedial action. A response to the comments received during this period is included in
the Responsiveness Summary, which is part of this Record of Decision (ROD).
This ROD is based on the contents of the Administrative Record for OU-11, in accordance with
CERCLA, as amended by SARA, and the NCP. The RI/FS reports and the Proposed Plan for
OU-11 provide information about OU-11 and the selected remedy. These documents are
available at the Information Repositories at EAFB and the Rapid City Public Library.
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2.4 SCOPE AND ROLE OF RESPONSE ACTION
The FFA identified 11 site-specific OUs and a Basewide ground-water OU. The 12 operable
units are identified as follows:
OU-1 Fire Protection Training Area
OU-2 Landfills Nos. 1 and 6
OU-3 Landfill No. 2
OU-4 Landfill No. 3
OU-5 Landfill No. 4
OU-6 Landfill No. 5
OU-7 Weapons Storage Area
OU-8 Explosive Ordnance Disposal Area (Pramitol Spill)
OU-9 Old Auto Hobby Shop Area
OU-10 North Hangar Complex
OU-11 Basewide Ground Water
OU-12 HardfillNo. 1
The remedial action objectives (RAOs) for OU-11 are:
• Prevent future human exposure to on-Base ground water with contaminants exceeding
State of South Dakota Ground-Water Quality Standards and Federal MCLs.
• Prevent additional ground water containing contaminants above State of South Dakota
Ground-Water Quality Standards and Federal MCLs from moving off-Base.
• Prevent human exposure to off-Base ground water with contaminants exceeding State of
South Dakota Ground-Water Quality Standards and Federal MCLs.
The area of attainment defines the area over which preliminary remediation goals would be
achieved, and is based on the RA -s. The areas of attainment for ground water at OU-11 are
illustrated on Figures 3 through 6.
2.5 SITE CHARACTERISTICS:
The OU-11 investigation included an evaluation of data collected from other OUs. The OU-11
study also included areas of potentially contaminated ground water which were not OUs or State
petroleum release investigation sites. As previously discussed, not all of these areas require
remediation. This section briefly discusses and summarizes the distribution of COCs, potential
routes of exposure, and current risks associated with the study areas of OU-11 that require action.
Only organic chemicals are discussed since the inorganic chemicals detected in these areas are
the result of natural geologic formations.
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2.5.1 Distribution of Contaminants
The following sections discuss the COCs in Area 1 and Area 2.
2.5.1.1 Area 1
South Docks Area
Volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), and
hydrocarbons, as total petroleum hydrocarbons (TPH), were reported in ground-water samples
from the South Docks Area. TCE was the most frequently reported VOC in 29 of 39 ground-
water samples, at concentrations ranging from 1 Mg/L to 7,000 ^g/L. The TCE degradation
product, total- 1 ,2-dichloroethene, was detected in 18 of 39 ground-water samples, at a maximum
concentration of 73 Mg/L. Chloroform was detected in 8 of 39 samples, at a maximum
concentration of 200 ^g/L. These three contaminants were also reported above their respective
MCLs and State standards in at least one sample each. The SVOCs pentachlorophenol and
chrysene were reported at concentrations above the MCL and State standard in one ground-water
sample. TPH was reported in eight samples. The maximum reported concentration of TPH was
2,500
2.5.1.2 Area 2
BG04 Area
TPH reported as jet fuel (JP-4), trichloroethene (TCE), and 1 ,2-dichloroethene (DCE) were
reported in the ground-water sample collected from well MW93BG04 on June 15, 1993.
Additional sampling was conducted during the OU-1 1 RJ to determine the lateral extent of these
contaminants.
Contaminants reported in ground water in the BG04 area included jet fuel, chlorinated
hydrocarbons, and benzene, toluene, ethylbenzene, xylenes (BTEX). The most frequently
reported chlorinated hydrocarbon was TCE, which was reported in five samples on-Base at a
maximum concentration of 1 10 Mg/L. Both TCE and PCE were reported at concentrations above
MCLs and State standards. Based on site geology and the shape of the TCE plume, the firing
range was suspected as a potential source of the TCE in the ground water. However, additional
investigations conducted in 1996 (including soil vapor surveys, electromagnetic surveys, test
pits, and historic literature searches) failed to locate a source of the TCE. Based on the relatively
low concentrations of COCs detected in this area, it is anticipated that a major source in this area
is probably not likely.
Additional ground- water investigations (BG04 Pre-Design Site Investigation, US AF, 1996) have
been conducted in off-Base areas beyond the northeast Base boundary to determine the extent of
off-Base contamination. Figures 8 and 9 illustrates the distribution contamination in the off-
Base areas. The Air Force believes that based on ground-water data collected from this area
during the Pre-Design Investigation, there may be at least two distinct contaminant areas in the
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off-Base region. The heavy, dashed line illustrated on Figures 8 and 9 indicates the Air Force's
estimated dividing line (based on the pre-design data) between areas suspected of being
contaminated from on-Base sources and those potentially contaminated from off-Base sources.
This ROD addresses off-Base areas west of this dividing line only; however, it is recognized that
the above estimates are based on preliminary data from the off-Base areas and that the "dividing
line" may change based on additional data collected. Additional investigations that are part of
the selected remedy will determine the extent of contamination in this area and will help further
refine estimates of the ground water relationships in this area. The area of ground-water
contamination resulting from contaminants moving from the Base may include areas to the east
of the line indicated in the figures. If this would be the situation, the remedial action will address
the newly identified area of contamination. The BG04 Pre-Design Site Investigation Report and
the Addendum to the BG04 Pre-Design Site Investigation Report Contain detailed information
regarding the off-Base investigation.
BG05 Area
TPH and TCE were reported in the ground-water sample collected from well MW93BG05 on 1 5
June 1993. Additional sampling was conducted during the OU-1 1 RI to determine the lateral
extent of these contaminants. TCA was reported at a concentration of 0.8 jug/L and TCE was
reported at a concentration of 7.6 Mg/L, slightly above the MCL and state standard of 5.0
Additional ground-water investigations (BG04 Pre-Design Site Investigation, USAF, 1996) have
been conducted in off-Base areas beyond the northeast Base boundary to determine the extent of
off-Base contamination. Figure 8 illustrates the distribution TCE in the off-Base areas. Figure 9
illustrates distributions of other VOCs (DCE, trichloroethane [TCA], PCE) detected in these off-
Base areas. Additional investigations, as part of this ROD, will determine the extent of
contamination in this area and further refine estimates of the ground water relationships in this
area. The source of the contaminants in the BGOS area is not known.
2.6 SITE RISK SUMMARY
2.6.1 Human Health Risks
A quantitative human health risk assessment (HHRA) was completed for OU-1 1 . The risk
assessment evaluated potential effects on human health posed by exposure to contaminants
within OU-1 1. The OU-1 1 HHRA was designed to provide three discrete sets of information:
• Risk to human health for two areas of concern, the South Docks Area and the BG04 Area.
• Estimation of the contaminant effects at four areas (upgradient OU-6, North OU-1 2,
BGOS, and Pond 003) after additional data collection.
• A comprehensive Basewide Ground- Water Risk Assessment, summarizing all
quantitative ground-water risk estimates and associated risk "drivers" for each OU, area
of concern, and supplemental data collection effort.
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2.6.2 Risk Assessment Process
The assessment of human health risks for this OU considered the following topics:
(1) Contaminants of concern (COCs) in ground-water samples collected at OU-11.
(2) Current and future land-use conditions.
(3) Potential environmental pathways by which populations might be exposed.
(4) Estimated exposure point concentrations of COCs.
(5) Estimated intake levels of the COCs.
(6) Toxicity of the COCs.
(7) Uncertainties in the assessments of exposure, toxicity, and general risks.
2.6.3 Exposure Assessment
Exposure pathways by which human populations may be exposed to the COCs in ground water
were identified during the OU-11 Risk Assessment. Exposure pathways generally consist of the
following four elements:
1) A source and mechanism of release.
2) A retention or transport medium.
3) A point of potential human contact with the medium.
4) An exposure route at the contact or exposure point.
An exposure pathway is considered complete only if each of these elements are present. The
South Docks (Area I) and BG04/BG05 (Area 2) areas themselves may serve as sources, while
ground water is the transport media. Exposure pathways under both current and future land use
scenarios were evaluated. Current land use onsite for Area 1 and Area 2 was assumed to be
associated with Base activities. Current land use offsite (off-Base), where relevant, was assumed
to be residential. Future land use at both Area 1 and Area 2 (onsite and offsite) was assumed to
be residential for purposes of conservatism. Receptors of concern are primarily residents who
will reside in these areas under future land use.
The potential for complete exposure pathways to exist under both current and future land use
scenarios, was evaluated for each area. For these land uses, the potential for receptors of concern
to be engaged in activities that could bring them into contact with shallow ground water
potentially contaminated with COCs, was evaluated for several exposure routes to determine the
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potential exposure groups. Carcinogenic and noncarcinogenic risks were calculated for three
potential exposure groups. These exposure groups are referred to as residential adults. Long
term (30 years) exposure to residential adults is believed to be the most appropriate potential
exposure group for ground water at OU-11. In general, if protection of this exposure group is
afforded, protection of other potential exposure groups would also be afforded. The exposure
groups are as follows:
(1) The future residential adult living in the South Docks area who is exposed to shallow
ground water.
(2) The future residential adult living on-Base in the BG04/BG05 area who is exposed to
shallow ground water.
(3) The residential adult living off-Base in the BG04/BG05 area who is exposed to shallow
ground water.
Table 2 summarizes contaminants, detection frequencies, and other pertinent data that were used
to develop a list of COCs for the OU-11 additional study areas. The list of COCs represents the
ground-water specific list of chemicals that met specific screening criteria and were carried
through the risk analysis to quantify the potential risk posed to humans from site-related
exposures. Ingestion of ground water, inhalation of COCs in ground water, and dermal contact
with ground water were all considered in the exposure assessment. The 95 percent upper
confidence limit mean (UCLM) concentrations have been estimated and were used as the
exposure point concentrations to provide reasonable maximum exposure (RME) risk estimates.
The calculated exposure point concentrations were used to calculate estimates of the average
daily intakes (intake) for all COCs. Intakes are expressed as the amount of chemical taken into
the body per unit body weight per unit time (e.g.. mg/kg-day), and are based on chemical
concentrations in 3 specific medium, intake quantity per unit time, exposure frequency and
duration, and body weight. The exposure frequency and duration used to calculate the RME risk
were 350 days/year and 30 years, respectively. Adult body weight was assumed to be 70 kg.
2.6.4 Toxicity Assessment
Slope factors (SFs) have been developed by EPA's Carcinogenic Assessment Group for
estimating excess lifetime cancer risks associated with exposure to potentially carcinogenic
chemicals. SFs, which are expressed in units of (mg/kg-day)'', are multiplied by the estimated
intake of a potential carcinogen, in mg/kg-day, to provide an upper-bound estimate of the excess
lifetime cancer risk associated with exposure at that intake level. The term "upper bound"
reflects the conservative estimate of the risks calculated from the SF. Use of mis approach
makes underestimation of the actual cancer risk highly unlikely. Slope factors 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.
Reference doses (RfDs) have been developed by EPA for indicating the potential for adverse
health effects from exposure to chemicals exhibiting noncarcinogenic effects. RfDs, which are
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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 chemical ingested from contaminated drinking water) can be compared to the RfD.
RfDs are derived from human epidemiological studies or animal studies to which uncertainty
factors have been applied (e.g., to account for the use of animal data to predict effects on
humans). These uncertainty factors help ensure that the RfDs will not underestimate the
potential for adverse noncarcinogenic effects to occur. The RfDs and SFs for COCs are
presented in Tables 3 and 4 for Area 1 and Area 2, respectively.
Excess lifetime cancer risks are determined by multiplying the intake level with the slope factor.
These risks are probabilities that are generally expressed in scientific notation (e.g., IxlO'6). An
excess lifetime cancer risk of 1x10"* indicates that, as a plausible upper bound, an individual has
a one in one million chance of developing cancer as a result of site-related exposure to a
carcinogen over a 70-year lifetime under the specific exposure conditions at a site. According to
the NCP and EPA's Risk Assessment Guidance for Superfiind (EPA/540/1-89/002) the
acceptable carcinogenic risk range is between 1 x 10"4 to 1x10"*. Depending upon site-specific
information, remediation may or may not be warranted if the total site risk lies within the
acceptable risk range.
Potential concern for noncarcinogenic effects of a single contaminant in a single medium is
expressed as the hazard quotient (HQ) (or the ratio of the estimated intake derived from the
contaminant concentration in a given medium to the contaminant's reference dose). By adding
the HQs for all contaminants within a medium or across all media to which a given population
may be reasonably exposed, the Hazard Index (HI) can be generated. The HI provides a useful
reference point for gauging the potential significance of multiple contaminant exposures within a
single medium or across media.
Tables 3 and 4 summarize the noncarcinogenic and carcinogenic risks for the South Docks
(Area 1) and BG04/BG05 Study Areas (Area 2), respectively.
2.6.5 Basewide Ecological Risk Assessment
A Basewide ecological evaluation was also conducted as part ocOU-l 1. Based on the size of the
individual OUs and the nature and use of the localized areas by potential receptors, detailed OU-
specific assessments of ecological risks were not warranted during the OU RIs. Therefore, a
Basewide Ecological Risk Assessment was conducted as part of OU-11. This study considered
impacts to the environment as a whole at EAFB and incorporated data collected during the
individual OU studies. The study concluded that terrestrial and aquatic risks are low Basewide;
therefore, remediation of ecological risk is not warranted. Volume III of the Final RI Report for
OU-11 presents the complete Basewide Ecological Risk Assessment.
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2.6.6 Risk Assessment Conclusions
At Area 1, the total carcinogenic risk to potential future residents from ingestion, inhalation, and
dermal contact with contaminated ground water is 1.77 x 10"4. This risk level exceeds the
acceptable risk range of 1 x IQ"4 to IxlO'6. At Area 2, the total carcinogenic risk to potential
future residents from ingestion, inhalation, and dermal contact with contaminated ground water is
2.27 x 1O'5. This risk level is within the acceptable risk range. However, the ground water at
Area 2 contains contaminants at concentrations greater than the MCL and contaminants have
already moved beyond the Base boundary. Remediation of ground water in Area 1 and Area 2 is
warranted because of the unacceptable risk to human health from exposure to contaminated
ground water and to prevent further offsite movement of ground water containing contaminants
at concentrations greater than the State of South Dakota Ground-Water Quality Standards or
Federal MCLs. Actual or threatened releases of hazardous suostances from OU-11, 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 DESCRIPTION OF ALTERNATIVES
In developing remedial alternatives for OU-11, information from feasibility studies (FSs) at other
OUs (and several additional areas of study) was compiled and examined to help develop
response actions for OU-11. Many of these other OUs (e.g., OUs 1,4, and 9) had contaminated
ground water within their boundaries. At OUs 1 and 4, ground-water alternatives were
developed to address localized ground-water contamination. At OU-9, the extent of ground-
water contamination was large and/or the contamination originated outside the boundaries of the
OU. Remediation of ground water at OU-9 was deferred to OU-11.
The development of alternatives for OU-l 1 was conducted in part using EPA's Presumptive
Remedies Approach Presumptive Response Strategy and Ex-Situ Treatment Technologies for
Contaminated Ground Water at CERCLA Sites (OSWER Directive 9283.1-12). This allows for
a streamlined selection of alternatives for remediation by using preferred technologies based on
historical patterns of remedy selection and EPA's scientific and engineering evaluation of
performance data on technology implementation. Use of the presumptive remedy does not
preclude the analysis of other technologies.
A brief description of the major components each ground-water remedial action alternative is
presented below. The alternatives are presented for Area 1 and Area 2, respectively.
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2.7.1 Area 1 Alternatives
Alternative 1 - No ActiQp
• The No Action Alternative is presented as a baseline to which other remedial measures
are compared. The EPA, through the March 1990 National Contingency Plan (NCP)
revisions, requires that the No Action Alternative option be examined in detail during the
remedial alternatives evaluation phase. Under this alternative, no treatment or
containment of contaminated ground water would be conducted.
Alternative 2 - Natural Attenuation with Supplemental Source Removal and Treatment
Treatment Components
• Contaminant concentrations will be reduced through natural attenuation throughout most
of Area 1. Natural attenuation processes include chemical (biodegradation, chemical and
biochemical stabilization) and physical processes (dispersion, dilution, sorption,
volatilization).
• Supplemental ground-water extraction would be conducted in the areas of highest
contamination (generally areas with TCE concentrations greater than 100 ppb). Based on
ground-water flows and using a conservative radius of influence of 50 ft, it is estimated
that 13 extraction wells would be required in these areas. Ground-water removal and
treatment would continue until all contaminant concentrations are below the regulatory
standard or until the removal and treatment of the ground water is no longer effective.
• Removed ground water would be treated using a stand-alone onsite air stripper with
carbon offgas treatment or an activated carbon treatment unit. Existing ground-water
treatment facilities at the Base may be used to treat removed ground water, if feasible
• Treated ground water would be discharged to a surface drainage, the Base waste water
treatment plant (WWTP), or injected back into the aquifer. The discharge option will be
determined during the remedial design phase. The main criteria for determining the
preferred discharge option effects on existing surface drainage areas and cost
effectiveness. For cost estimate purposes it is assumed that discharge would be to the
Base WWTP.
General Components
• Institutional controls would be implemented to prevent the use and consumption of
untreated ground water containing chemicals above MCLs and limit development on-
Base. Institutional controls would include: (1) issuing a continuing order to restrict
onsite worker access to contaminated soil/ground water; (2) filing a notice to the deed
detailing the restrictions of the continuing order and ground-water well restrictions; and
(3) a covenant to the deed in the event of property transfer.
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Long-term ground-water monitoring would be used to monitor the movement of
contaminants in the ground water and to monitor the effectiveness of natural attenuation.
Monitoring would be conducted using a combination of new and existing wells and
would be implemented as part of the Basewide, long-term ground-water monitoring plan.
It is estimated that 1 2 new monitoring wells would be installed and 30 wells would be
sampled and analyzed each sampling round in this area. Sampling would initially be
conducted on a quarterly basis, with the potential to reduce the frequency at a later time,
if warranted. Ground-water samples would be analyzed for VOCs, SVOCs, TPH, and
natural attenuation parameters. Ground-water monitoring will be continued until ground-
water concentrations are below State of South Dakota and Federal MCLs.
Ground-water sampling results will be ur?d to verify that natural attenuation is reducing
contaminant concentrations in the ground water at a rate that is protective of human
health and the environment. If, during subsequent reviews, sampling results indicate that
contaminant concentrations in the ground water are not being reduced through natural
attenuation, prior to movement off-Base, the pump and treat portion of this alternative
would be expanded to treat additional areas of contaminated ground water. A SO percent
cost contingency has been included in this alternative to cover the potential added cost of
expanding the system. Ground- water monitoring will be continued until ground-water
concentrations are below State of South Dakota and Federal MCLs.
Implementation of this alternative does not pose any unusual or extraordinary conditions.
Based on estimates of remediation time frames for Area 2, which has similar soil
characteristics as Area 1, it is estimated that natural attenuation would reduce
contaminant concentrations to levels below MCLs in approximately 20 years. Ground-
water data in the South Docks area indicate that natural attenuation is taking place. The
data indicate that contaminant concentrations have been decreasing during the last four
years. It is estimated that the supplemental extraction wells would be operated for 1-3
years, based on the estimated volume of ground water present in these areas. These
estimates would be refined during remedial design.
ARARs
A risk assessment was conducted for OU-1 1 ; however, the COCs for Area 1 have Federal
and State MCLs. The Federal and State MCL for TCE is 5 ppb. Ground water would be
treated until MCLs are met. If necessary, off gas emissions from air strippers would be
treated to meet requirements of the Clean Air Act (C AA) and State air quality
requirements. Ground water would be further treated, if necessary, to meet Clean Water
Act (CWA) requirements for surface water discharges of treated ground water. Wastes
(e.g., drill cuttings) generated during implementation would be disposed of in accordance
with RCRA Hazardous Waste requirements, if necessary.
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Alternative 3 - Ground-Water Extraction and Treatment with Containment
Treatment Components
• A combination of extraction wells and/or trenches would be used to remove contaminated
ground water in Area 1. Wells and/or trenches would be located throughout Area 1.
Some wells would be located in the Pride Hangar area where the concentration of
contaminants is the highest. Some wells may also be located as containment wells to
prevent off site movement of contaminants. Based on ground-water data from the South
Docks area, it is estimated that 5 extraction wells would be located in the Pride Hangar
area. It is estimated that 20 extraction wells and approximately 1,100 lineal feet of
interceptor/extraction trenches would be installed in the main area of the South Docks
(i.e., Rows 20 through 50) and the OU-° area.
• Removed ground water would be treated using a combination of air strippers with carbon
offgas treatment and activated carbon treatment units. Based on the predicted ground-
water flow from the extraction wells and trenches, it is estimated that three treatment
units would be required. For cost estimate purposes, it is assumed two air stripper units
and one carbon unit would be used.
• Treated ground water would be discharged as described in Alternative 2.
General Components
• Institutional controls as described in Alternative 2 would be implemented as part of this
alternative.
• Long-term ground water monitoring to detect potential movement of contaminants and to
determine the effectiveness of the alternative would be implemented. Long-term ground-
water monitoring would be the same as described in Alternative 2, except that natural
attenuation monitoring would not be conducted. It is estimated that 12 new monitoring
wells would be installed and a total of 20 wells (new and existing) would be sampled
each sampling round in this area.
• This alternative could be implemented using standard methods and equipment that are
readily available. Based on the volume of ground-water to be treated in the South
Docks/OU-9 areas, and considering the influence of the extraction wells, it is estimated
that it would take 5-10 years to remediate ground water in Area 1. Predesign studies
would be conducted to finalize design parameters and determine the number and
placement of wells.
Major ARARs
The major ARARs for this alternative are the same as those described in Alternative 2.
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Alternative 4 - Aquifer Air Sparging (AASVSoi! Vapor Extraction fSVF>
Treatment Components
• AAS would be used to remove contaminants out of the ground water and transport them
into the unsaturated zone where they would be removed using SVE. AAS/SVE wells
would be located only in the areas of highest contaminant concentrations (generally those
areas with TCE concentrations above 100 ppb). Based on data collected from other
studies at EAFB (CAP, ST-21), it is estimated that approximately 1,050 AAS and 975
SVE wells would be required to treat the areas of highest contamination.
• Extracted vapors would be trer *ed using a vapor-phase carbon adsorption system.
• Natural attenuation will reduce concentrations of contaminants in the ground water in
areas of lesser contamination that are not being actively addressed with AAS/SVE. The
application of natural attenuation is described under Alternative 2.
General Components
• Institutional controls as described in Alternative 2 are part of this alternative.
• Long-term ground water monitoring to detect potential movement of contaminants, to
determine the effectiveness of the alternative, and to monitor natural attenuation would be
implemented. Long-term ground-water monitoring would be the same as described in
Alternative 2.
• AAS is an in situ treatment process; therefore, there is no ground water to discharge.
AAS/SVE may be difficult to implement over large areas because of the large number of
wells required and the potential for short circuiting. A pilot test will be required to
determine whether AAS/SVE can be implemented and if so, to determine the final design
parameters of the system. The large areal extent of the contaminant plumes will require a
large number of AAS and SVE wells. The implementation of this alternative assumes
that separate AAS and SVE systems would be installed; however, there is the potential
reduce costs by overlapping system components. For cost purposes, it is estimated that
the AAS/SVE systems would require five years of operation; however, this estimate
would be refined during pilot studies. As discussed above, reduction of contaminant
concentrations in the ground water to levels below MCLs through natural attenuation is
estimated to take 20 years.
Major ARARs
• Ground water would be treated until MCLs are met. Emissions from vapor-phase carbon
treatment units would meet requirements of the Clean Air Act (CAA) and state air quality
requirements. Because AAS is an in situ process, there is no ground water to discharge.
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Wastes (e.g., drill cuttings) generated during implementation would be disposed of in
accordance with RCRA Hazardous Waste requirements, if necessary.
Alternative 5 - Containment
Treatment Components
• Ground-water extraction wells and trenches would be used to contain contaminated
ground water onsite. Extraction wells and trenches would be located along the leading
edges of the contaminant plumes to intercept contaminated ground water before it moves
offsite. Wells and trenches would be located along the eastern and southern edges of the
ICE plume. Based on a conservative estimated radius of influence of 50 ft,
approximately 25 extraction wells would be located along the eastern edge of the
contaminant plume.
• The 400-ft interceptor trench, constructed as part of the Corrective Action Plan (CAP)
implemented to address jet fuel releases from the flightline area, would be incorporated
into this alternative. The existing trench, located near the southern leading edge of the
contaminant plume, would be extended approximately an additional 400 ft to the east-
northeast.
• Removed ground water would be treated using a combination of air strippers with carbon
offgas treatment (two units estimated) and activated carbon treatment units (one unit
estimated), similar to Alternative 3.
• Treated ground water would be discharged as described in Alternative 2.
General Components
• Institutional controls as described in Alternative 2 would be implemented as part of this
alternative.
• Long-term ground water monitoring as described under Alternative 3 would be
implemented.
• This alternative could be implemented using standard methods and equipment that are
readily available. It is estimated that movement of contaminants in the ground water to
the containment wells/trenches (where they will be extracted and treated) would take 50-
75 years. However, natural attenuation is estimated to reduce chemicals in the ground
water to levels below MCLs in approximately 20 years. The system would have to be
operated for 20 years before ground water is below MCLs. A predesign study would be
conducted to further refine these estimates.
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Major ARARs
The major ARARs for this alternative are the same as those described in Alternative 3.
2.7.2 Area 2 Alternatives
Alternative 1 - No Action
• The No Action Alternative is described under Area 1, Alternative 1.
Alternative 2 - Natural Attenuation with Supplemental Source Removal and Treatment
Treatment Components
• Contaminant concentrations (primarily TCE) will be reduced through natural attenuation
throughout most of Area 2, including both the on-Base and off-Base areas.
• Supplemental ground-water extraction in the areas of highest contamination (on-Base in
the central BG04 area where TCE concentrations are greater than 100 ppb). Based on
ground-water flows and the BG04 Pre-Design Site Investigation, it is estimated that 6
extraction wells would be required in these areas. Ground-water removal and treatment
would continue until all contaminant concentrations in this area are below the regulatory
standard or until the removal and treatment of the ground water no longer is effective.
• Extracted ground water would be treated using a stand-alone onsite air stripper with
carbon offgas treatment, or an activated carbon treatment unit.
• Treated ground water would be discharged to surface drainage, the Base waste water
treatment plant (WWTP), or injected back into the aquifer. For cost estimate purposes it
is assumed that discharge would be to the Base WWTP.
General Components^
• Institutional controls similar to those described under Area 1, Alternative 2 would be
implemented on-Base.
• Institutional controls off-Base may consist of requiring restrictive easements, providing
alternative potable water supplies to off-Base residents whose drinking water wells may
be impacted by ground water contaminants from the Base, and/or other measures. EAFB
currently has a proactive program in which they will provide, at no cost, an alternative
potable water supply to off-Base residents whose drinking water has been adversely
impacted by Base activities. This program is administered on a case-by-case basis and
consists of agreements with individual landowners. The program will be incorporated as
part of this alternative (and all subsequent Area 2 alternatives), if necessary, and will be
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continued (on a case-by-case basis) until the ground water is safe to drink, which is
estimated to be up to 16 years (see below).
• Long-term ground-water monitoring would be used to monitor the movement of
contaminants in the ground water and to monitor the effectiveness of natural attenuation.
Monitoring would be conducted using a combination of new and existing wells and
would be implemented as part of the Base wide, long-term ground-water monitoring plan.
It is estimated that 30 new monitoring wells would be installed and 40 wells would be
sampled and analyzed each sampling round in this area. Sampling would initially be
conducted on a quarterly basis, with the potential to reduce the frequency at a later time,
if warranted. Ground-water samples would be analyzed for VOCs and natural attenuation
parameters.
• As described under Area 1, Alternative 2, a 50 percent cost contingency is included in
this alternative to cover the potential added cost of expanding the system.
• Implementation of this alternative does not pose any unusual or extraordinary conditions.
Ground-water modeling (batch-flush) was conducted for Area 2 (BG04/BG05) to
determine the approximate time frame for natural attenuation to reduce the concentrations
of contaminants in the ground water to levels below MCLs. Based on this modeling, it is
estimated that natural attenuation would reduce chemical concentrations to levels below
' MCLs in approximately 14-16 years. Based on the length of time to actively remediate
ground water in this area, the natural attenuation time frame is considered acceptable.
However, the time frame could be shortened if more active remediation were to take
place. Ground-water data in the BG04 area indicate that natural attenuation is taking
place. The data from recent ground-water samples collected indicate that contaminant
concentrations have been decreasing during the last four years. It is estimated that the
supplemental extraction wells would be operated for 1-3 years, based on the estimated
volume of ground water present in the areas proposed for supplemental ground-water
rerrn • ^al. These estimates would be further refined in a predesign study.
Maior ARARs
• The major ARARs for this alternative are the same as those for Area 1, Alternative 2.
Alternative 3 - Iron Induced Dehalogenation
Treatment Components
• Treatment walls composed of impermeable barrier sections and innovative, permeable,
chemical treatment sections would be constructed underground to provide in situ flow-
through treatment of shallow ground water. Treatment walls would be located along the
east Base boundary to contain contaminated ground water on-Base, and in the central
portion of BG04 where the highest concentration of contaminants exist. The treatment
walls are constructed across the flow paths of the contaminated ground water where the
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impermeable sections direct flow to the treatment sections. The treatment sections
consist of a porous media such as sand, mixed with a catalyst, typically iron filings.
Contaminants (TCE) are degraded into non-toxic chemicals as ground water flows
through the wall. It is estimated that a 1,500-ft long wall would contain the majority of
the contaminant plume along the Base boundary east of BG04. Similarly, a 750-ft long
wall would be located along the Base boundary east of BG05. A 2,500 ft-long treatment
wall would be placed in the central BG04 area.
• Once the ground-water containment and treatment systems are in place in the most
contaminated areas (all of which are on-Base), the amount of off-Base contamination will
be reduced to levels below MCLs through natural attenuation.
• Cottonwood, poplar, or other suitable trees would be planted in selected on-Base and/or
off-Base areas to further control shallow ground water and potentially uptake some
contaminants. The use of trees is for enhancement only and is not part of the primary
remedy. Even without the trees, chemical concentrations off-Base would be reduced
through natural attenuation.
General Components
• Institutional controls (both on-Base and off-Base) would be implemented as described
under Alternative 2.
• Long-term ground-water monitoring would be implemented as described under
Alternative 2.
• A 30% cost contingency is included in this alternative to expand active treatment if
natural attenuation does not provide adequate protection of human health and the
environment off-Base.
• Implementation of this alternative would require heavy construction equipment. The
treatment walls must be keyed into the bedrock. Either sheet piling or slurry could be
used for the barrier sections. Implementation requires extensive predesign studies to
establish the final design parameters and locations of the treatment walls. This
technology is proprietary and requires obtaining a license. The availability of vendors
who install these systems is limited. The treatment sections may require replacement or
regeneration during the life of the system depending on local conditions. This would be
determined during predesign studies.
• It is estimated that it will take 50-100 years for contaminated ground water to move from
the western extent of the plume to the Base boundary. Because of the placement of a
central treatment wall and natural attenuation, the actual time for concentrations of
chemicals in the ground water to be reduced below MCLs will be much less. It is
estimated that it will take only 14-16 years for concentrations of chemicals in the ground
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water (and their associated degradation products) to be reduced to levels below MCLs by
natural attenuation alone.
Major ARARs
• Ground water would be treated until MCLs are met. This system uses a passive,
destructive, in situ technology and does not produce any contaminated residuals once
implemented. Wastes (e.g., excavated soil, drill cuttings) generated during
implementation would be disposed of in accordance with RCRA Hazardous Waste
requirements, if necessary.
Alternative 4 - Ground-Water Containment/Extraction and Treatment
Treatment Components
• A combination of extraction wells and/or trenches would be used to contain and remove
contaminated ground water in Area 2. Wells and/or trenches would be located along the
Base boundary east of BG04 and BG05 to prevent off-Base movement of contaminated
ground water. Some wells would also be located in the areas of highest contaminant
concentrations in the central BG04 area to reduce the contaminant concentrations in
ground water flowing toward the Base boundary. Based on ground-water data obtained
during the BG04 Pre-Design Site Investigation, it is estimated that four extraction wells
would be located in the gravel seams east of BG04, two wells would be located east of
BGOS, and six wells would be located in the central BG04 area.
• Removed ground water would be treated using a combination of air strippers with carbon
offgas treatment and/or activated carbon treatment units. For cost estimate purposes, it is
assumed two air stripper units would be used.
• Treated ground water would be discharged as described in Alternative 2.
• On-Base ground-water containment and treatment systems will reduce source area
chemical concentrations. Off-Base contamination will be reduced to levels below MCLs
through natural attenuation.
• Cottonwood, poplar, or other suitable trees would be planted at selected on-Base and/or
off-Base areas as described in Alternative 3.
General Components
• Institutional controls as described in Alternative 2 would be implemented as part of this
alternative.
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• Long-term ground water monitoring to detect potential movement of contaminants and to
determine the effectiveness of the alternative would be implemented. Long-term ground-
water monitoring would be the same as described in Alternative 2.
• This alternative could be implemented using standard methods and equipment that are
readily available. Based on ground-water velocities in the BG04 area, and considering
the influence of the extraction wells, it is estimated that it would take 25-50 years for
contaminated ground water to move from the western extent of the plume to the Base
boundary, and be removed and treated by the wells along the eastern Base boundary. The
actual remediation time would be less if natural attenuation is factored in. Based on
modeling conducted during the BG04 Pre-Design Site Investigation, it is estimated that it
will take 14-16 years for concentrations of chemicals in the ground water (and their
associated degradation products) to be reduced to levels below MCLs by natural
attenuation. Predesign studies would be conducted to finalize design parameters and
determine the number and placement of wells.
Maior ARARs
• The major ARARs for this alternative are the same as those described in Alternative 2.
Alternative S - Dual-Phase Extraction
Treatment Components
• In situ dual-phase extraction wells would be used to remove soil gas and ground water in
Area 2. This alternative is similar to Alternative 4 except for the type of wells used.
Wells would be located in the same areas as described under Alternative 4. Based on
vendor information, it is estimated that each dual-phase well would have a radius of
influence of 100 ft. Based on that estimate, approximately 10 dual-phase wells would be
located along the Base boundary east of BG04, 5 wells would be located east ot'BGOS,
and 15 wells would be located in the central BG04 area.
• Removed ground water would be treated using air strippers with carbon offgas treatment
(two units estimated). Removed air would be treated using vapor-phase carbon
adsorption units (two units estimated).
• Treated ground water would be discharged as described in Alternative 2.
• On-Base ground-water containment and treatment systems will reduce source area
chemical concentrations. Off-Base contamination will be reduced to levels below MCLs
through natural attenuation.
• Cottonwood, poplar, or other suitable trees would be planted in selected on-Base and/or
off-Base areas as described in Alternative 3.
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General Components
• Institutional controls as described in Alternative 2 would be implemented as part of this
alternative.
• Long-term ground water monitoring to detect potential movement of contaminants and to
determine the effectiveness of the alternative would be implemented. Long-term ground-
water monitoring would be the same as described in Alternative 2.
• This alternative could be implemented using standard methods and equipment that are
readily available. Low permeability soils typical of EAFB may reduce effectiveness of
this alternative. Additional pilot tests may be required to verify the implementability of
this alternative. Based on ground-water velocities in the BG04 area, and considering th"
influence of the dual-phase extraction wells, it is estimated that it will take 20-40 years
for contaminated ground water to move from the western extent of the plume to the Base
boundary, and be removed and treated by the wells along the eastern Base boundary. The
actual time would be somewhat less if natural attenuation is factored in. Based on
modeling conducted during the BG04 Pre-Design Site Investigation, it is estimated that it
will take 14-16 years for concentrations of chemicals in the ground water (and their
associated degradation products) to be reduced to levels below MCLs by natural
attenuation.
Major ARARs
• The major ground-water ARARs for this alternative are the same as those described in
Alternative 2. Emissions from vapor-phase carbon treatment units would meet
requirements of the Clean Air Act (CAA) and state air quality requirements. Wastes
(e.g., drill cuttings) generated during implementation would be disposed of in accordance
with RCRA Hazardous Waste requirements, if necessary.
2.8 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The analysis of alternatives coupled with the use of the presumptive remedy provides a narrower
range of feasible remedial actions for ground water at OU-11.
The RAOs for OU-11 are as follows:
• Prevent future human exposure to on-Base ground water with contaminants exceeding
State of South Dakota Ground-Water Quality Standards and Federal MCLs.
• Prevent additional ground water containing contaminants above State of South Dakota
Ground-Water Quality Standards and Federal MCLs from moving off-Base.
• Prevent human exposure to off-Base ground water with contaminants exceeding State of
South Dakota Ground-Water Quality Standards and Federal MCLs.
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The area of attainment is defined as the area which will achieve the remedial action objectives
after remediation is completed. The physically or geographically distinct areas of OU-11 make it
feasible to divide the OU into separate areas for purposes of evaluating attainment status and
determining appropriate response actions. The areas of attainment for OU-11 are discussed
below.
Area 1 (South Docks't
As described previously, Area 1 includes the South Docks and the northern part of OU-9.
Ground water in OU-9 was initially investigated separately during the OU-9 RI. Because of the
proximity to the South Docks area and the potential for commingled plumes in these areas,
development of ground-water remediation alternatives was deferred to OU-11. The area of
attainment is illustrated in Figure 3.
Area 2 ffiG04/BG05^
Area 2 includes the on-Base areas surrounding monitoring wells BG04 and BGOS and the off-
Base areas to the east. The area of attainment for the on-Base areas of Area 2 are illustrated on
Figure 4 (BG04 area) and Figure 5 (BGOS area). The off-Base area of attainment for Area 2 is
illustrated on Figure 6.
Pursuant to Section 300.430(e)(9)(iii) of the EPA's revised National Oil and Hazardous
Substances Pollution Contingency Plan (NCP), the remedial action to be implemented should be
selected based upon consideration of nine evaluation criteria. These criteria are as follows:
Threshold Criteria
1. Overall protection of human health and environment.
2. Compliance with applicable or relevant and appropriate requirements (ARARs).
Primary Balancing Criteria
3. Long-term effectiveness and permanence.
4. Reduction of toxicity, mobility, or volume of contamination.
5. Short-term effectiveness.
6. Implementability.
7. Cost.
Modifying Criteria
8. State acceptance.
9. Community acceptance.
The following sections provide a brief review and comparison of the remedial alternatives
according to EPA's evaluation criteria.
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2.8.1 Overall Protection Of Human Health And The Environment
The assessment of this criterion considers how the alternatives achieve and maintain protection
of human health and the environment.
Area 1
Alternative 1 does nothing to reduce risk levels associated with consumption and contact with
shallow ground water. Alternative 2 reduces the potential for exposure to untreated shallow
ground water through the use of natural attenuation with supplemental source removal and
treatment, and institutional controls. Alternative 2 includes a contingency because it relies on
natural attenuation. Natural attenuation will be further evaluated during preliminary ground-
water monitoring to determine if contaminants in the ground water will be reduced to levels
below regulatory standards prior to movement off-Base. Alternative 3 provides protection of
human health and the environment by actively removing and treating contaminated ground water
and implementing institutional controls to prevent use of untreated ground water until it meets
MCLs. Alternative 4 uses a combination of active treatment (AAS/SVE) and natural attenuation
to protect human health and the environment. As in Alternative 2, Alternative 4 requires a
contingency because of the partial reliance on natural attenuation. Alternative 5 is similar to
Alternative 3 in that it removes and treats ground water; however, this alternative relies on
interception of contaminated ground water as it flows to the boundary of the contaminated area
rather than placing wells/trenches within the plume as in Alternative 3. All alternatives use
institutional controls to prevent use of contaminated ground water.
Area 2
Alternative 1 does nothing to reduce risk levels associated with consumption and contact with
shallow ground water. Alternative 2 reduces the potential for exposure to untreated shallow
ground water through the use of natural attenuation with supplemental source removal and
treatment, and institutional controls including :roviding alternate sources of water to off-Base
residents whose water supplies have been adversely impacted by the Base. Alternative 2
includes a contingency because it relies on natural attenuation. Natural attenuation will be
further evaluated during preliminary ground-water monitoring to determine if contaminants in
the ground water will be reduced to levels below MCLs in a reasonable time frame. Alternative
3 is protective of human health and the environment by containing and passively treating
contaminated ground water as it flows through treatment walls that destroy the contaminants, and
the use of institutional controls to prevent use of untreated ground water until it meets MCLs.
Alternative 4 uses wells and/or trenches and treatment systems to prevent ground water with
chemical concentrations above MCLs and risk-based concentrations from moving off-Base and
to remove and actively treat contaminated ground water until it meets MCLs. Alternative 5 is
similar to Alternative 4 in that it removes and treats ground water; however, this alternative uses
dual-phase extraction wells to protect human health and the environment. Alternatives 3,4, and
5 rely on natural attenuation to reduce low concentrations of contaminants off-Base. A long-
term monitoring program will be used to determine long-term protection to human health and the
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environment and to determine the need for additional remedial measures off-Base. All
alternatives incorporate institutional controls to help protect human health and the environment
2.8.2 Compliance With ARARs
Alternatives are assessed under this criterion in terms of compliance with ARARs. Applicable
requirements include cleanup standards, standards of control and other substantive environmental
protection requirements, criteria or limitations promulgated under federal or state laws that
specifically address a hazardous substance, pollutant, contaminant, remedial action, location or
other circumstances at a CERCLA site.
i
Relevant and appropriate requirements address problems or situations sufficiently similar to
those encountered at a CERCLA site that their use is well suited to the environmental and
technical factors at a particular site. The determination of "relevant and appropriate" emphasizes
the similarity and appropriateness of the requirement to a site. ARARs are grouped into these
three categories:
• . Chemical-Specific ARARs are health or risk-based numerical values or methodologies
which, when applied to site-specific conditions, result in establishment of the amount or
concentration that may be found in, or discharged to, the environment.
• Location-Specific ARARs restrict the concentration of hazardous substances or the
conduct of activities solely because they are in specific locations such as flood plains,
wetlands, historic places, and sensitive ecosystems or habitats.
• Action-Specific ARARs are usually technology or activity-based requirements or
limitations on actions taken with respect to hazardous wastes.
A summary evaluation of Federal and State ARARs pertinent »o this remedial action is provided
in Table 5 at the end of Section 2.0 and a narrative discussion _i compliance with ARARs is
provided below for the alternatives considered.
Area 1
Alternative 1 does not meet the chemical-specific ARARs for ground water. Alternative 2 will
meet chemical-specific ARARs only if site conditions are favorable for natural attenuation (this
will be determined during the predesign study, and ground-water monitoring). Alternatives 3
and 5 would meet the chemical-specific ARARs for ground water by actively treating ground
water with chemical concentrations above MCLs. Alternative 4 would likely meet chemical-
specific ARARs for the areas actively treated; however, the alternative also relies on natural
attenuation as does Alternative 2. Ground water contaminated above MCLs would be contained
on-Base under Alternatives 3 and.5 and may be contained on-Base under Alternatives 2 and 4,
depending on the effectiveness of natural attenuation. Alternatives 2, 3,4, and 5 would meet
location and action specific ARARs identified in Table 5.
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Area 2
Alternative 1 does not meet the chemical-specific ARARs for ground water. Alternative 2 (on-
Base and off-Base) and Alternatives 3,4, and 5 (off-Base) will meet chemical-specific ARARs
only if site conditions are favorable for natural attenuation (this will be determined during the
predesign study, and ground-water monitoring). Alternatives 3, 4 and 5 would meet the
chemical-specific ARARs for ground water by actively treating (pump and treat) on-Base ground
water with chemical concentrations above MCLs. Natural attenuation will reduce contaminant
concentrations off-Base to levels below MCLs over time. Further off-Base movement of ground
water contaminated above regulatory standards would be reduced and eventually eliminated or
contained under Alternative 3,4, and 5, allowing natural attenuation to proceed at a faster rate. If
natural attenuation proves to be ineffective in a reasonable time frame, additional remedial
measures will be conducted so that ground water will meet MCLs. Alternatives 2, 3,4, and 5
would meet location and action specific ARARs identified in Table 5.
2.8.3 Long-term Effectiveness And Permanence
The assessment of this criterion considers the long-term effectiveness of alternatives in
maintaining protection of human health and the environment after response action objectives
have been met.
Area 1
Alternative 1 would not provide long-term effectiveness in reducing the potential for movement
of VOCs in ground water. Alternative 2 uses a combination of natural attenuation, extraction
and treatment, and institutional controls to reduce the potential for movement of solvents and
other contaminants in ground water and prevents the use of untreated ground water until it meets
MCLs. The long-term effectiveness of natural attenuation will be evaluated during ground-water
monitoring. Alternatives 3 and 4 provide long-term effectiveness in reducing the potential for
movement of chemicals of concern in ground water by t. Bating ground water and using
institutional controls to prevent use of untreated ground water; however, Alternative 4 also relies
partly or natural attenuation. Alternative 5 provides long-term effectiveness using a combination
of containment and institutional controls; however, Alternative 5 does not provide long-term
effectiveness to the extent provided under Alternatives 3 and 4 due to the reduced amount of
extraction systems. Alternatives 2, 3, 4, and 5 use long-term monitoring to detect potential
offsite movement of ground water above MCLs. Because of the uncertainties of natural
attenuation associated with Alternative 4, Alternative 3 would provide the greatest long-term
effectiveness and permanence.
Area 2
Alternative 1 would not provide long-term effectiveness in reducing the potential for movement
of VOCs in ground water. Alternative 2 uses natural attenuation and institutional controls to
reduce the concentration of TCE in ground water and prevents the use of untreated ground water
until it meets MCLs. The long-term effectiveness of natural attenuation is not known at this time
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but will be evaluated in the early stages of implementation of this alternative. Alternatives 3,4,
and 5 offer equal long-term effectiveness in reducing the potential for movement of chemicals in
ground water by containing and treating ground water on-Base and using institutional controls to
prevent use of untreated ground water above MCLs. However, Alternative 4 may be the most
effective in the long term due to simpler operating requirements. Alternative 3 and 5 require the
use of technologies and equipment that are not as widely used or accepted. Alternatives 2,3,4,
and 5 use long-term monitoring to monitor movement of contaminated ground water and the
potential impact to off-Base water supplies.
2.8.4 Reduction Of Toxicity, Mobility, Or Volume Through Treatment
The assessment of this criterion considers the anticipated performance of specific treatment
technologies an alternative may employ.
Area 1
Alternative 1 does not reduce toxicity, mobility, or volume of contaminated ground water, except
through natural processes and has no provision for monitoring. Alternative 2 uses natural
attenuation to reduce the toxicity and volume of contaminated ground water, and supplemental
extraction and treatment in the areas with the highest concentrations of contaminants, to reduce
the toxicity, mobility, and volume of affected ground water. Alternatives 3 and 5 reduce the
toxicity, volume, and mobility of contaminated ground water through extraction/treatment and
containment (with extraction and treatment at the containment points), respectively. Alternative
4 reduces the volume and toxicity of contaminated ground water through treatment and natural
attenuation; however, in some cases AAS has been shown to increase the movement of
contaminated ground water. Due to the extent of the extraction systems, Alternative 3 will be
most reliable and efficient in reducing the toxicity, mobility, and volume of contaminants in
ground water.
Area 2
Alternative 1 does not reduce toxicity, mobility, or volume of contaminated ground water, except
through natural processes and there is no provision for monitoring. Alternative 2 relies on
natural attenuation to reduce the toxicity and volume of contaminated ground water and
supplemental extraction and treatment to reduce the toxicity, mobility, and volume of affected
ground water with the highest concentrations of contaminants. Alternatives 2, 3, 4, and 5 rely on
natural attenuation to reduce the volume of contaminants in off-Base areas. However, if natural
attenuation does not reduce contaminant concentrations, the cleanup components under
Alternative 4 would be the easiest to implement in off-Base areas. Alternatives 4, and 5 reduce
the toxicity, volume, and mobility of contaminated ground water through extraction and
treatment of affected ground water on-Base. Alternative 3 reduces the volume and toxicity of
contaminated ground water through treatment as it passes through a treatment wall. Under
Alternatives 3,4, and 5, toxicity and volume of affected ground water off-Base is reduced
through natural attenuation. Alternative 4 would be the most reliable in reducing toxicity,
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mobility, and volume because the alternative relies on proven technologies in comparison to
Alternatives 3 and 5.
2.8.5 Short-Term Effectiveness
The assessment of this criterion considers the effectiveness of alternatives in maintaining
protection of human health and the environment during the construction of a remedy until
response action objectives have been met.
Area 1
It is not anticipated that the proposed alternatives would significantly impact worker or
community health and safety during the implementation period. Alternative 2,3,4, and 5 may
impact worker health and safety through dust emissions and exposure to chemicals in the soil and
ground water during the initial construction phase. PPE will be used to mitigate potential risks to
workers during implementation of the remedial alternative. If necessary, VOCs emitted from the
air stripper will be treated prior to release. Alternative 3 would most readily address risk in the
short term due to the ease of implementation and the extent of extraction and treatment as
compared to Alternative 4. Alternative 5 only involves containment of the contamination,
thereby requiring a longer remediation time frame.
Area 2
It is not anticipated that the proposed alternatives would significantly impact the surrounding
people or the environment or worker health and safety during the implementation period.
Alternatives 2, 3, 4, and 5 may impact worker health and safety through dust emissions and
exposure to chemicals in the soil and ground water during the initial construction phase. PPE
will be used to mitigate potential risks to workers during implementation of the remedial -
alternative. If necessary, VOCs emitted from the air stripper will be treated prior to release.
Short-term risk is addressed equally under Alternatives 2, 3,4, and 5 by implementation of the
alternate water supply. Alternative 2 would not contain contaminated ground water on-Base,
which would not address short-term risk as adequately as Alternatives 3,4, and 5.
2.8.6 Implementability
The assessment of this criterion considers the administrative and technical feasibility of
implementing the alternatives and the availability of necessary goods and services for
implementation of the response action.
Area 1
There is nothing to implement under Alternative I. The remaining alternatives require no special
or unique activities and could be implemented with readily available equipment, materials, and
methods. Alternatives 2, 3, 4, and 5 would require a predesign study prior to implementation to
determine effectiveness and final design parameters. Alternative 2 may not be as implementable
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as the other alternatives based on the ability of the natural processes to remediate the ground-
water contamination in a reasonable time frame. The need for many AAS points and SVE wells
makes Alternative 4 harder to implement than Alternatives 3 and 5. At Area 1, the largest
ground-water extraction systems will be the most difficult to implement because of ongoing Base
activities (i.e., operation of the flightline). Although Alternative 3 is implementable, Alternative
5 may be the easiest to implement due to the minimal amount of extraction systems needed.
Area 2
Alternative 1 requires no implementation. The remaining alternatives require no special or
unique activities and could be implemented with readily available equipment, materials, and
methods. Alternative 3 may require deep trenching methods. Alternatives 2, 3,4, and 5 would
require a predesign study prior to implementation to determine final design parameters.
Alternatives 3 and 5 would require more detailed predesign studies than Alternative 4. It is
expected that Alternative 3 would be the most difficult to implement due to the depth of trench
needed and characteristics of underlying geology. If natural attenuation does not reduce
contaminant concentrations, the cleanup components under Alternative 4 would be the easiest to
implement in off-Base areas. Because Alternative 4 uses proven technologies with known
results, it would be the most implementable alternative.
2.8.7 Cost
The assessment of this criterion considers the capital and operation and maintenance (O&M)
costs associated with each of the alternatives. Costs were developed using the Remedial Action
Cost Engineering and Requirements System (RACER), Means Building Cost Index, vendor
estimates, and contractor experience. Alternatives are evaluated for cost in terms of both capital
costs and long-term O&M costs necessary to ensure continued effectiveness of the alternatives.
Capital costs include the sum of the direct capital costs (materials and labor) and indirect capital
costs (engineering, licenses, permits). Long-term O&M costs include labor, materials, energy,
equipment replacement, disposal, and sampling necessary to ensure the future effectiveness of
the alternative.
The objective of the cost analysis is to evaluate the alternatives based on the ability to protect
human health and the environment for additional costs that may be incurred. Cost varies
between the alternatives as a result of differences in the amount of materials and the level of
effort required for each alternative. The least costly alternative for Area 1 and Area 2 is the No
Action alternative.
Area 1
For Area 1, the least costly alternative which includes a remedial action is Alternative 2.
Alternative 3 is the next more costly alternative. The most costly alternative is Alternative 4,
which is more than twice the cost of Alternative 3. Alternative 5, Containment, is more costly
than Alternative 3, Ground-Water Extraction and Treatment with Containment. Alternative 5
requires a longer remediation time frame which accounts for most of the cost difference as
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compared to Alternative 3. Even though Alternative 3 is not the least costly alternative, the
added capital costs versus the benefit gained, as compared to the other alternatives, indicate that
Alternative 3 is the most cost effective alternative.
Area 2
For Area 2, the least costly of the alternatives that include remedial actions is Alternative 2.
Alternative 4 is the next more costly alternative. The most costly alternative is Alternative 3
which is more than twice the cost of Alternative 4. Long-term monitoring costs for remedies
that include remedial actions are similar for each alternative. With added capital costs,
Alternative 4, Ground-Water Containment/Extraction and Treatment, would be the most cost
effective alternative.
A summary of the costs for each alternative is as follows:
Area 1
Alternative 1 (No Action)
Total Capital Costs
30- Year Present Value for Annual Costs
Annual Cost = SO
Years - 30
Discount Rate = 5%
TOTAL 30- Year Present Value
Alternative 2 (Natural Attenuation w/ Supplemental Source Removal)
Total Capital Costs
30- Year Present Value for Annual Costs
Annual Cost - Years 1-3 = $243,000
Annual Cost - Years 4-20 *• $70,000
Years - 30
Discount Rate « 5%
TOTAL 30- Year Present Value
Alternative 3 (Ground- Water Extraction and Treatment w/ Containment)
Total Capital Costs
30-Year Present Value for Annual Costs
Annual Cost - Years I- 10 = $254,400
Years = 30
Discount Rate = 5%
TOTAL 30- Year Present Value
SO
$0
SO
SI, 224,000
SI, 344,000
52368,000
$2,780,000
51,964,000
S4,744,000
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Alternative 4 (AAS/SVE)
Total Capital Costs
30- Year Present Value for Annual Costs
Annual Cost -Years 1-5 = $509.000
Annual Cost - Years 6-20 = $ 1 25,000
Years = 30
Discount Rate = 5%
TOTAL 30- Year Present Value
Alternative 5 (Containment)
Total Capital Costs
30- Year Present Value for Annual Costs
Annual Cost - Years 1-20 = $262,400
Years = 30
Discount Rate - 5%
TOTAL 30-Year Present Value
$8,588,000
$3,224,000
SI 1,812,000
$2,095,000
$3,270,000
$5365,000
Area 2
Alternative 1 (No Action)
Total Capital Costs
30- Year Present Value for Annual Costs
Annual Cost = SO
Years = 30
Discount Rate = 5%
TOTAL 30- Year Present Value
Alternative 2 (Natural Attenuation w/ Supplemental Source Removal)
Total Capital Costs
30-Year Present Value for Annual Costs
Annual Cost - Years 1-3 = $139,500
Annual Cost - Years 4-16 = $89,500
Years = 30
Discount Rate = 5%
TOTAL 30-Year Present Value
SO
$0
SO
$802.000
$1,106,000
$1,908,000
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Alternative 3 (Iron Induced Dehalogenatioo)
Total Capital Costs
30- Year Present Value for Annual Costs
Annual Cost - Years 1-16 = $136,000
Years = 30
Discount Rate = 5%
TOTAL 30-Year Present Value
Alternative 4 (Ground-Water Containment/Extraction and Treatment)
Total Capital Costs
30- Year Present Value for Annual Costs
Annual Cost - Years 1-3 = $188,500
Annual Cost - Years 4-16 = $144,000
Years = 30
Discount Hate = 5%
TOTAL 30-Year Present Value
Alternative 5 (Dual-Phase Extraction)
Total Capital Costs
30- Year Present Value for Annual Costs
Annual Cost - Years 1-3 = $184,000
Annual Cost - Years 4-16 = $137,000
Years = 30
Discount Rate = 5%
TOTAL 30-Year Present Value
$4,941,000
$1,474,000
$6,415,000
$1,124,000
$1,682,000
52,806,000
$1,695,000
$1,611,000
$3,306,000
OU-8 Compliance Monitoring
OU-8 Compliance Monitoring*"
Total Capital Costs
Total Annual Sampling & Analysis Costs
TOTAL 1 YEAR COST
25,000
21,000
S46.000
NOTES: (a) OU-8 compliance is not part of Area I or Area 2 alternatives. Compliance monitoring at OU-8
will be conducted regardless of the alternative.
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2.8.8 State Acceptance
The assessment of this criterion considered the State's preferences for or concerns about the
alternatives.
The State concurs with the selected remedy. The State provided comments on the remedial
investigation, feasibility study, and Proposed Plan. In accordance with the requirements of the
NCP, the State of South Dakota was also provided the opportunity to review and comment on the
ROD. As a result of that review and after incorporating adequate responses to the comments into
the respective documents, the State concurred with the remedy.
2.8.9 Community Acceptance
Comments offered by the public were used to assess the community acceptance of the proposed
alternative. The community expressed their concerns about the selected remedy during the
public comment period and during the public meeting. There were no written comments
received during the public comment period. Questions were posed to the Base during the public
meeting. In general, public.comments were directed at specific components of the remedy, rather
than the remedy itself. There were no objections to the selected remedial alternative. Public
questions about the remedy posed during the public meeting appeared to be satisfactorily
addressed during the meeting. The questions and concerns of the community are discussed in
detail in the Responsiveness Summary, which is Appendix C of the ROD.
2.9 SELECTED ALTERNATIVE
Based on the requirements of CERCLA, comparative analysis using the nine criteria, public
comments, and in consultation with EPA and the State, the Air Force has determined that the
selected alternative for Area 1 is Alternative 3, Ground-Water Extraction and Treatment with
Containment; and for Area 2 is Alternative 4, Ground-Water Containment/Extraction and
Treatment. The^e alternatives include institutional controls in conjunction with ground-water
containment and treatment of extracted ground water to reduce potential risk. Five-year reviews
of the remedy will be required because potential contaminants will remain at OU-11 above
health-based levels following completion of the installation ground-water extraction systems, and
the use of natural attenuation in the off-Base BG04/BG05 area.
Major components of Alternative 3 for Area 1 arc;
• Removal and containment of ground water containing contaminants at concentrations
above MCLs.
• Ground-water treatment and discharge.
• Institutional controls and long-term monitoring.
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Ground-Water Removal and Containment
A pre-design study mutually agreeable to the Air Force, EPA, and the State of South Dakota
would be conducted to determine the final number and location of ground-water extraction
wells/trenches required to remove and/or contain ground water. Based on the results of the
predesign study, extraction wells and/or trenches will be located to remove ground water
contaminated above MCLs. Some wells may be located as containment wells along the
perimeter of the area, to prevent offsite movement of ground water containing contaminants
above MCLs.
Ground-Water Treatment and Discharge
Removed ground water will be treated using a combination of air strippers and/or activated
carbon ground-water treatment units. Air strippers will be equipped with off gas treatment, if
necessary. Treated ground water will be discharged to the Base WWTP, surface discharge, or be
injected back into the aquifer based on the results of predesign studies.
Institutional Controls and Long-Term Monitoring
Institutional controls will be implemented to prevent the use and consumption of untreated
ground water. These controls will include: (1) issuing a continuing order (by the Installation
Commander) to restrict or place limitations on the installation of any new ground-water wells;
(2) filing a notice in environmental and real estate records at the Base or Installation, detailing
the restrictions of the continuing order and ground-water well restrictions; and (3) compliance
with the provisions of CERCLA Section 120(h)(3) or other applicable statutory requirements in
the event of property transfer.
A long-term monitoring program will be developed and implemented during remedial action and
is subject to approval of both EPA and SDDENR. Contaminant concentrations in the ground
water will be monitored to evaluate the effectiveness of the remediation system and to determine
if contaminants in the ground water are moving offsite. If it is determined that contaminants in
the ground water are moving offsite, appropriate action will be taken to remedy this situation.
Continued analysis and monitoring of the ground-water remediation system will be conducted to
determine if the remediation system is approaching an asymptotic level due to physical
limitations of the site, or the benefits of the remedial action no longer justify the long-term
operation of the system. Remediation goals and the remedial alternative will be re-evaluated at
that time. Long-term monitoring will continue until State of South Dakota Ground-Water
Quality Standards and Federal MCLs are met.
This alternative will meet the remedial action objectives and reduce the potential risk for OU-11
by preventing future exposure to contaminants in the ground water.
F:\PROJ\60J7S90\FS\ROD\Ff:\AL\OUI IRODFIH Z-35 April. 199'
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Final Record of Decision Operable Unit II
Ellsworth Air Force Base. South Dakota
The major components of Alternative 4 for Area 2 are:
• Ground-water removal along the northeast Base boundary and at areas with high
contaminant concentrations on-Base.
• Ground-water treatment and discharge.
• Natural attenuation of off-Base ground water.
• Alternative water supply to off-Base residents affected by contamination coming from the
Base.
• Additional investigation to determine the eastern extent of off-Base ground-water
contamination
• Institutional controls and long-term monitoring.
Ground-Water Removal
A pre-design study would be conducted to determine the final number and location of
ground-water extraction wells/trenches required to contain contaminated ground water on-Base
and remove ground water in the areas of highest contaminant concentrations on-Base. Generally,
wells will be located on-Base in the BG04 area and the BG05 area.
Ground-Water Treatment and Discharge
Removed ground water will be treated using a combination of air strippers and/or activated
carbon ground-water treatment units. Air strippers would be equipped with off gas treatment, if
necessary. Treated ground water will be discharged to the Base WWTP, a surface water
drainage, or be injected back into the aquifer based on the results of predesign studies.
Natural Attenuation
Contaminants in off-Base ground water will be reduced to concentrations below MCLs through
natural attenuation. Once the ground-water containment and treatment systems are installed in
the most contaminated areas, all of which are on-Base, the amount of off-Base contamination
will also be reduced to levels below MCLs. The physical and chemical characteristics of the off-
Base soil and ground water are capable of dispersing and reducing the relatively low
concentrations of ground-water contamination.
In addition, cottonwood, poplar, or other suitable trees will be planted at selected locations on-
Base and/or off-Base as an innovative way to further control shallow ground-water movement.
Cottonwood and poplar trees are fast growing and are known to use significant quantities of
water. There is also evidence to suggest that trees take in organic contaminants with the water,
reducing contaminant concentrations. The quantity and location of trees will be determined
F:\PROJ\6037890\FS\ROD\FIMAL\OUIIROD.FIN 2-36 April. 1997
-------
Final Record of Decision Operable Unit 11
Ellsworth Air Force Base. South Dakota
during the remedial design and will be done in a manner not to effect the availability of water in
downgradient drinking water wells. The contaminants do not accumulate in the trees, but are
either broken down through the respiration process or emitted to the atmosphere. These
emissions would be negligible due to the already low amounts of contaminants in the ground
water. The use of trees is experimental and is solely to enhance natural attenuation. If the trees
do not function as planned, reduction of chemicals in the ground water off-Base will still take
place through other natural attenuation processes.
If, during subsequent reviews, sampling results indicate that contaminant concentrations in the
ground water are not being reduced through natural attenuation prior to movement off-Base or at
the predicted rate to be protective of human health and the environment, the use of additional
remedial activities will be evaluated and conducted. The extent of additional remediation will be
dependent on the amount of remaining contamination in the ground water. The pump and treat
portion of this alternative could be expanded to treat additional areas of contaminated ground
water both on-Base and off-Base as necessary.
Alternative Water Supply for Off-Base Residents
The Air Force will provide a clean water supply to residents whose drinking water contains
contaminants at concentrations above State of South Dakota or Federal MCLs due to movement
of contaminants beyond the Base boundary. EAFB currently has a proactive program in which
they will provide, at no cost, an alternative potable water supply to such residents. This program
is administered on a case-by-case basis and consists of agreements with individual landowners.
Enough water would be supplied to the landowners to cany out normal domestic activities,
which includes drinking, bathing, cooking, lawn and garden watering, and other residential
outdoor activities. The program can be used to fulfill the alternative water supply requirement
and will be continued (on a case-by-case basis) until contaminant concentrations are below State
of South Dakota or Federal MCLs.
Additional Investigation
Based on predesign investigations conducted in the BG04 area, ther? may be additional off-Base
sources contributing to ground-water contamination off-Base. An additional investigation will
be conducted to determine the extent of contamination moving beyond the Base boundary. This
will clarify the extent of Air Force's liability under CERCLA for remediation of the off-Base
areas. The Air Force will address all ground-water contamination coming from the Base,
including any new areas discovered through the additional investigation.
Institutional Controls and Long-Term Monitoring
Institutional controls similar to those described under Alternative 3 for Area 1 will be
implemented. In addition, a monitoring program will be implemented to monitor the
effectiveness of natural attenuation in providing protection to human health and the environment.
F:\PKOJ\60tr89n\FS\ROD\FI\AL.OUIIKOD.FIN2-3"/ April, 1997
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Final Record of Decision Operable Unit 11
Ells-worth Air Force Base, South Dakota
2.10 STATUTORY DETERMINATIONS
The selected remedies meet the statutory requirements of CERCLA as amended by SARA and
the NCP. These requirements include protection of human health and the environment,
compliance with ARARs, cost effectiveness, and utilization of permanent solutions and
alternative treatment technologies to the extent practicable. Containment, by definition, does not
attempt to reduce the toxicity or volume of potentially hazardous materials; rather, it reduces the
likelihood of exposure to contaminants by preventing the movement of materials beyond the
boundaries of the site. The selected remedies represent the best balance of tradeoffs among the
alternatives considered, with respect to pertinent criteria.
The manner in which the selected remedies meets er :h of the requirements is discussed in the
sections below.
2.10.1 Protection of Human Health and the Environment
Area 1
The selected remedy addresses health and environmental issues that were identified in the OU-11
RI report. Specifically, the ground-water extraction and treatment alternative:
• Eliminates exposure to contaminated ground water by removing it from the ground and
treating it to meet MCLs.
• Reduces risk by reducing the concentration of contaminants in the ground water.
• Provides onsite containment of contaminated ground water.
• Prevents the use of untreated ground water.
• Provides for long-term monitoring of ground water to identify potential future risks
associated with OU-11.
Area 2
The selected remedy addresses health and environmental issues that were identified in the OU-11
RI report. Specifically, the ground-water extraction and treatment alternative:
• Reduces exposure to contaminated ground water by containing it on-Base.
• Reduces risk by reducing the concentration of contaminants in the ground water to levels
below MCLs.
• Prevents the use of untreated ground water.
F\PROJ\6037890\FS\ROD\Ff\AL\OUl I ROD.F/.V 2-38 April. 1997
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Final Record of Decision Operable Unit 11
Ellsworth Air Force Base. South Dakota
• Provides for long-term monitoring of ground water to identify potential future risks
associated with OU-11 and monitor the effectiveness of natural attenuation.
2.10.2 Compliance with ARARs
Alternative 3 for Area 1 and Alternative 4 for Area 2 both will meet Safe Drinking Water Act
MCLs and State Ground Water Quality Standards. If necessary, offgas emissions from air
strippers would be treated to meet requirements of the Clean Air Act (CAA) and state air quality
requirements. Ground water would be further treated, if necessary, to meet Clean Water Act
(CWA) requirements for surface water discharges of treated ground water. Wastes (e.g., drill
cuttings) generated during implementation would be disposed of in accordance with RCRA
Hazardous Waste requirements, if necessary. Additional information about ARAR compliance is
contained in Section 2.8.2.
2.10.3 Cost Effectiveness
The selected remedies are cost effective because they have been determined to provide overall
effectiveness in reducing human health risks relative to its costs.
Area 1
The net present worth of Alternative 3 for Area 1 is $4,744,000. The estimated costs of the
selected remedy are within an order of magnitude of (less than two times) the costs associated
with natural attenuation alternative, and yet the selected remedy provides active treatment in a
much shorter time frame, reducing the potential for offsite movement of contaminants. The
selected remedy is less costly than the remaining alternatives for Area 1.
Area 2
The net present worth of Alternative 4 for Area 2 is $2,806,000. The estimated costs of the
selected remedy are within an order of magnitude of (less than two times) the costs associated
with Alternative 2, which does not fully meet remedial action objectives because it does not
provide containment of contaminated ground water. The selected remedy is less costly than the
remaining alternatives for Area 2.
2.10.4 Utilization of Permanent Solutions and Alternative Treatment Technologies to the
Extent Possible
EPA has established that ground-water extraction and treatment has proven effective in
remediating contaminated ground water. The selected remedies for Area 1 and Area 2 utilize
permanent solutions and treatment technologies to the maximum extent practicable. Alternative
treatment technologies, including natural attenuation and phytoremediation, were also evaluated
and incorporated into the selected remedies for Area 1 and Area 2. The selected remedies
provide the best tradeoff among alternatives relative to the five primary balancing criteria.
F:\PROA6037890\FS\ROD\FINAL\OUI I ROD F/.V 2-39 April. 1997
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Final Record of Decision Operable Unit II
Ellsworth Air Force Base. South Dakota
Area 1
Alternative 3, the selected alternative, provides a permanent solution to exposure to contaminated
ground-water, by removing and treating contaminated ground water and preventing unauthorized
use of untreated ground water until MCLs have been met. A long-term ground-water monitoring
system will be implemented to detect potential movement of chemicals from the area of
attainment.
Because Alternative 3 utilizes proven technologies and is more reliable for treating contaminated
ground water as compared to the other alternatives, it will provide the greatest efficiency in
reducing contaminant toxicity, mobility, and volume through treatment. Because the selected
alternative is less technically complex as compared to Alternative 4, and provides for more active
remediation as compared to Alternatives 5 and 2, Alternative 3 will address risk in the shortest
time frame. Although Alternative 3 is not the easiest alternative to implement, long-term
effectiveness and cost effectiveness out weigh any difficulties that may be encountered during
implementation of the remedy. The relatively small increase in capital costs for Alternative 3, as
compared to the other alternatives, greatly increases the cost effectiveness of the remedy.
Alternative 3 was chosen because it can address risk to human health in a reasonable time frame,
it is a proven technology in treating contaminated ground water, and it is the most cost effective
remedy as compared to the other alternatives.
The State accepts the use of the selected alternative. The State has been involved with the
remedial investigation and remedy selection process. Concerns regarding the development of the
alternatives were identified by the State and were adequately addressed.
Anticipated community concerns were addressed during the development of alternatives. During
the public comment period, the community did not identify any additional concerns for the
selected remedy at Area 1.
Area 2
Alternative 4, the selected alternative, provides a permanent solution to exposure to contaminated
ground-water, by removing and treating contaminated ground water on-Base and preventing
unauthorized use of untreated ground water until MCLs have been met. A long-term ground-
water monitoring system will be implemented to detect potential movement of chemicals from
the area of attainment. Once the areas of ground water with the highest concentrations of
contaminants are contained and treated on-Base, natural attenuation will reduce lower
concentrations of contaminated ground water off-Base to levels below MCLs. Alternative water
supplies will be provided to off-Base residents to reduce risk until the ground water quality meets
MCLs.
Alternative 4 is the most effective in the long term due to simpler operating requirements of the
remedial action as compared to other alternatives. Natural attenuation is relied upon only in
areas where contaminant concentrations are low, greatly increasing the reliability of the remedy.
Alterative 4 uses the most proven technologies as compared to the other alternatives. This
F: \PKOJ\603 7890\FS\RODVrl\AL\OLIIROD. FIN 2-40 ~ April. 1997
-------
Final Record of Decision Operable Unit 11
Ellsworth Air Force Base. South Dakota
increases the reliability in reducing contaminant toxicity, mobility, and volume through
treatment. Alternative 4 includes measures to address short-term risk to nearby residents.
Alternative 4 requires simple operating procedures which will allow for it to be implemented
most efficiently as compared to other alternatives. The ground water treatment systems could be
easily implemented in off-Base areas if natural attenuation is not remediating the ground water in
a reasonable time frame. Alternative 4 is the most cost effective alternative, particularly as
compared to Alternatives 3 and 5. Although Alternative 4 does not use the most innovative
technologies as compared to other alternatives evaluated, it will provide for reliable ground-water
treatment, it includes measures to address short-term risk, and it is the most cost effective
alternative.
The State accepts the use of the selected alternative. The State has been involved with the
remedial investigation and remedy selection process. Concerns regarding the development of the
alternatives were identified by the State and were adequately addressed.
The community did not object to the use of Alternative 4 for Area 2, but individuals had
concerns with the implementation of the remedy. These concerns were adequately addressed by
clarifications about the performance of the remedy. The selected alternative provides for enough
flexibility to address any additional concerns during the long-term operation and maintenance of
the remedial action.
A five-year review of the selected remedy will be performed due to the time frame needed to
meet cleanup goals and the uncertainty of natural attenuation. The review will be conducted no
less often than every five years after the signing of the ROD to ensure the remedy continues to
provide adequate protection of human health and the environment.
2.10.5 Preference for Treatment as a Principal Element
The selected remedies for Areas 1 and 2 both provide treatment of contaminated ground water as
their principal element. The selected remedy for Area 2 utilizes natural attenuation in the off-
Base areas. This is justified for the following reasons:
• The sources of the highest concentrations of contaminants in the ground water will be cut
off from off-Base ground water, allowing natural attenuation to proceed at a faster rate.
• The concentrations of chemicals in the ground water off-Base are relatively low.
• Alternative water supplies are being provided to residents whose water supplies have
been impacted by the Base.
F\PROJ\60rS90\FS\ROD\FINAL\OUIIRODFM 2-41 April. 1997
-------
Final Record of Decision Operable Unit 11
Ellsworth Air Force Base. South Dakota
2.11 DOCUMENTATION OF SIGNIFICANT CHANGES
The Proposed Plan for Area 1 indicated the selected remedy for Area 1 included remediation of
ground water in the North Docks and the area surrounding Building 102 located in the eastern
part of OU-9. Review of the ground-water data from these areas indicate that the contamination
in the ground water is the result of petroleum product releases. Only isolated occurrences of
solvents were detected at low concentrations. Based on this information, remediation of the
ground water in these areas will be addressed by the Air Force through the State of South Dakota
Petroleum Release Program and not under CERCLA. Therefore, the selected remedy for Area 1
no longer includes remediation of ground water in the North Docks area or the area around
Building 102. The Air Force will continue to clean up these sites under the State program in an
efficient, expedient manner similar to other areas directed for cleanup through the OU-11 ROD.
F:\PROJ\60 J7a90\FS
-------
Final Record of Decision Operable Unit 11
Ellsworth Air Force Bate. South Dakota
ACC:
AF:
AFB:
ARARs:
CERCLA:
COC:
DCE:
EOD:
EAFB:
EPA:
FFA:
HHRA:
HI:
HQ:
IN SITU:
IRP:
JP-4:
MCL:
mg/L:
NCR:
NPL
OU:
PCE:
ppm:
RCRA:
RfD:
RI/FS:
RME:
ROD:
SARA:
SACM:
SDDENR:
SF:
3.0 LIST OF ACRONYMS AND ABBREVIATIONS
Air Combat Command
Air Force
Air Force Base
Applicable or Relevant and Appropriate Requirements
Comprehensive Environmental Response, Compensation and Liability Act
Chemical of Concern
Dichloroethene
Explosive Ordnance Disposal
Ellsworth Air Force Base
Environmental Protection'Agency
Federal Facilities Agreement
Human Health Risk Assessment
Hazard Index
Hazard Quotient
In the original place
Installation Restoration Program
Jet Propulsion Fuel Number Four; contains both kerosene and gasoline fractions.
Maximum Contaminant Level
Micrograms per liter
Milligrams per liter
National Oil and Hazardous Substances Contingency Plan
National Priorities List
Operable Unit
Perchloroethylene; liquids used in degreasing or paint removal.
Parts per million by weight
Resource Conservation and Recovery Act
Reference Dose
Remedial Investigation/Feasibility Study
Reasonable Maximum Exposure
Record of Decision
Superfund Amendments and Reauthorization Act
Superfund Accelerated Cleanup Model
South Dakota Department of Environment and Natural Resources
Slope Factor
F:\fflOJ\60i7890\FSUlOD\FINAL\OUIIROD.FIN
3-1
April. 1997
-------
Final Record of Decision Operable Unit II
Ellsworth Air Force Base, South Dakota
SVOC: Semi volatile Organic Compound
TCA: 1, 1,1,-tetrachloroethane
TCE: Trichloroethylene
UCLM: Upper Confidence Limit Mean
USAF: United States Air Force
UST: Underground storage tank
VOC: Volatile Organic Compound
WWTP: Wastewater Treatment Plant
F:\PROM03789OifSmOD\FINAL\OUI IKOD.FIN '. 3£Z April. 1997
-------
Final Record of Decision Operable Unit 11
Ellsworth Air Force Base, South Dakota
APPENDIX A
FIGURES
F:\PROJ\6037890\FS\ROD\FINAL\OUI1RODFIN April. 1997
-------
210
x"
ELLSWORTH AFB
Scote in Mites
APPROXIMATE
'*•".'""•'
EI_t_S WORTH
AIR F-ORCE BASE
ELLSWORTH AFB
MHO cnr. sown
OU-11 ROD
AREA LOCATION MAP
PTOOECT HCR
ar
DRAWN ar
URG
CHECKED 91
SCALE I DATE
AS SHOWN I JUNE 95
PROJECT NO
60378.90
flCURE:
-------
'•"'
S -j^
'£ ~
INSTALLATION " 80UNOARY* "T|
•> ) •
OU-1
OU-2
OU-3
OU-4
OU-5
OU-6
OU-7
OU-8
OU-9
OU-10
ou-n
OU-12
JtOOOtfTTLE DR. S HOUSING |
OU-2
INDUSTRIAL
GATE
(SS-11)
OPERABLE UNITS
FIRE PROTECTION TRAINING
AREA (FT-01)
LANDFILLS 1 it 6 (LF-02)
LANDFILL 2 (LF-03)
LANDFILL 3 (LF-04
LANDFILL 4 (LF-05'
LANDFILL 5 (LF-06^
LOW LEVEL RADIATION WASTE BURIAL AREA (RW-07)
EXPLOSIVE ORDNANCE DISPOSAL AREA & PRAMITOL SPILL
OLD AUTO HOBBY SHOP AREA (OT-15)
NORTH HANGAR COMPLEX (ST-19)
BAsennoe GROUNO WATER sruor
HAROFILL NO. 1
OPERABLE UNITS
OU11 ADDITIONAL STUDY AREAS
El_l_SWORTM
AIR FORCE BASE
ELLSWORTH AF8
RAPID OTT. SOUTH DAKOTA
OU-11 ROD
SITE LOCATION MAP
PROJECT MCR
DESIGNED BY
DRAWN BY
STAFF
CHECKED ar
SCALE
AS SHOWN
DATE
SEP 95
PROJECT NO
60378.90
FIGURE:
-------
a im n UOMTOMNC WELL/
— —— LOCATION (ouii)
a iM3 » UOMTOMNC
WELL/MIL 8OMNO LOCATION
TOPOCMAPHC ELEVATION A8OVC
USL - CONTOUR INTEKVAL«10'
MCA Or AHAINMCNT
oocx STUOT MEA
MCA OT AfT/UNUCNT
MOKTMCAM OU9 STUOT AREA
vor >tMMU eotonexi IAUO
west K ti*tcna.
i) ogn vuova ««t eauato *
-------
feCK . • « • ........ •• •• . . . I « ..•^r'.t ..'«.... » „ ..»•* "..'•' ^•Vfi!°r'.iiKft'%Y«-«i'iVTj*''
Kv*' ' • ' ' • ' i ' " '• -'' •-• ••^w-'-jifL'l/''w .
^r^tix---, -: .'."., •!'''-.v^f^:.:y:.:--;|^p
j^ssS^i ••. -••"..•)• ^";"""'-'1^l!*
mMOMVOriMMMW
!i
U
V •GUMWCILVMOfCMIDNIIAIIIMIAST WW ' *''
^ UM. IHMUMWMMCTIDaMMOMMHOON \" • "•-•.,• • '" • •.•f.
v~ . ' \ ' ' ''!• • " ;' '• \ : % • i i
\» jfe -V '•.'.. !..•.«• vl I
rtfr • > \ * v' *i •"* '•' '. *:v Vl: '-i* ; ' v * *•- • * iv?-
JJTA. " '. --•, \' • "•• ''"i ' * \ \i ' V'j ' y
V\^s& V "'" ! >v v~-.. V.* ti-, .-i'/O1* /'"•->..'
— — — — — — — -S —••'V—J Vt' '1 >..' ; V^- j—I
J» f- ( -• '<-. .• •-. '
* ? '.,
> - I
' • •• 4|* « * « * i'" * *'^1
' / .-,v —'- ;l
.• * • r* • • „-••••—•• ••-•j <• ii
• * •
* ' *
• * \ *
___ ^
1U OMATW IMAM I ffk
AfPHOUMATI OHOUND HMTM
OFF4Aa|
AREA Of AT
-------
TCE PLUME BASED ON FIGURE J-4 FROM
THE ADDENDUM TO 8C04 PRE-DESIGN SITE
VESTICATION REPORT DATED DECEMBER 1996.
TO THIS REPORT FOR OFF-SITE CONTINUATION
BASE BOUNDARY FENCE
APPROXIMATE GROUND-WATER
FLOW DIRECTION
1994 Rl MONITORING WELL/
SOIL BORING LOCATION
1994 Rl SOJL BORING LOCATION
PRIVATE WELL
AREA OF ATTAINMENT
TCE PLUME '
SCALE
£L.l_S WORTH
AIR FORCE BASE
ELLSWORTH AFB
we on. SOUIH OMOIA
AREA 2
ON-BASE BG05
AREA OF ATTAINMENT
OU-11 FS
OCSIGNEO BY
CHECKED BY
DRAWN BY
STAFF
PROJECT UCR.
ROT
UAIE
JAN 97
SCALE
AS SHOWN
PROJECT NO.
60378.90
SHEET NO.
5
-------
-------
/
-a
i 9
1M3/9* *t UONfTORMC
WO1/SOI. 8CMNC LOCATION
1OT3/9* M F1EIO SCREEN/
SO*. 90RMC LOCATION
TCE CONCENTRATION
SURFACE OONNACC
BASE BOUNDARY FENCE
TOPOCRAPMC aEVATiON ABOVE
USL - CONTOUR INTERVAL-10'
AIM rowcc
COSHORTH
OU-11 flOO
srasunoN OF ret
« ON-BASE
CMUNO
Mil
JUNE 9S
AS SHOWN
MU7&M
-------
* *V **"•"*--x, •/ *
o >
s. ^ / .
m*ui \\ \ ,' ^
^ '' v'" '
\w®m
:: »v>j*»/{!
A.^x^.
FIOURE I
DISnUBimONOFTCC
OFF-BASE BOM/KMS
ICt OMAIM IMAM • |»*
AFMIOUMATI OHOUMDIMT1H
-------
_ ___
. • ,\ — ,— . .1
! \ ^— '
.. -
— . \ I ^Sj V
\ \ ffl >
V / ^ „-'' \^-- .
\— . t •-• — , . » .» • x-r< •
'. » '
• • • .
~
NC OMEARM HUN 1 Mfe
•UTUMTHMMwb
nOURE 9
DISTRIBUTION OF DCS, KB. TCA
OFF-BASE BOMAOOf
^ APPROMMATC OftOUNO-WATEM
7
-------
Final Record of Decision Operable Unit 11
Ellsworth Air Force Base, South Dakota
APPENDIX B
TABLES
F\PROJ\6037890\FS\ROD\FIXAL\OUIIROD.FIN April. 1997
-------
TABLE I OU-II STUDY AREAS - SUMMARY
Study Area
BG04
BG05
OIT-Basc
BG04/BG05"'
UptraJkmOU-6
South Docks
PMnlUI COCt**
TCE
U-DCE
PCE
BCIUjCfMI
toluene
ayknet
Bis(2-«thylheiyl phthaiate)
beuBIIC
gammt-chkndane
p,p'-DDT
I.I.I-TCA
TCE
TCE
DCE
PCE
TCA
TCE
1,2-DCE
P.P--DDE
AWrin
gamma cMordane
TCE
U-DCE
Bis(2-ethylhexyl) phlhiltlc.
beuBHC
FrecjMMjr
of
4/11
VII
l/ll
l/ll
l/ll
l/ll
l/ll
VII
1/10
1/10
mo '
1/1
1/1
NA
NA
NA
NA.
20
IO
IO
in
10
27O5
I7O4
605
205
Riige tf
Delected
VtlMt
net
23-110
0.1-5
23
O.t
1
2
13
6-1
0.023
0.025
005
01
7
NA
NA
NA
NA
1-4
52
O.M
0.22
0.25
1-7.000
0.9-73
3-17
0.025
95%
UCLM*
C.Dt.
43.7
2.15
7.47
102
3.05
1.29
4.52
6.10
0017
0.017
00)4
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
610
13.1
6.07
0.014
Elect* MCL?
Yet
No
Yet
No
No
No
No
No
No
No
No
No
Yet
Yet
No
No
No
No
No
No
No
No
Yet
No
No
No
Related u
COC*»
No*
No
Yerf"
No
No
No
No
No
Yet
No
No
No
Grwud- Water ActU*
Ana «m evaluated Hiiitt preliminary remediation g<*b in Chapter 2. Indadet off-
Bate Altai catt of BMC boundary.
^tt^~™^*~~*>~*»'"*-'**-«
Aiu _1J 1 1 iliMiil ' •linn ml fTllaH' IB •' ntb^HMililu
ofcMMinM.
plao. Mmtd to Stale POL prafniD because of PRKDCC of |e«fuelialBTEX
coostituenu.
-------
TABU I (Com )
Study Art*
OU-9
OU- 10 (Nonh Docks)
North OU- 12
OU-7
Pond OOJ
Potential COCiM
1.1 -DC A
1.2-DCE
acetone
benzene
limmndirMnfomnKjnf
chloroform
rfthmfnMhlntnfnethaUia*
PCE
TCE
di-n-butyl ptnhaUle
bis(2-elhylhexry)phthalalc
acenaphihene
1.2-DCE
•cclone
benzene
carbon disutfide
ethytbenxenc
MIK
PCE
toluene
TCE
xylenes
TCE
1.2-DCE
None
Benzene
Frequency
•r
DciertiM
2/17
10/17
7/17
1/17
1/17
1/17
VI7
1/17 '
3/17
10/17 .
1/17
4/17
1/17
Ml
4/21
3/21
1/21
4/21
V2I
1/21
4/21
1/21
4/21
Ml
I/I
I/I
NA
I/I
Raage «f
Detected
Value*
jjg/L
0.6-1
0.5-51
4.5-420
2
1
0.2
0.1-0.3
0.9
0.1-20
0.5-190
1
1-7
1
0.7-16
II-J50
39-3100
0.7
0.2-13
6-220
44
0.7-10
250
0.9-5
2-220
10
16
NA
2
95%
UCLM*1
Cone.
PI/l
. 1.01
Ml
117
l.ll
1
1.05
1.02
1
4.51
496
5.26
5.29
526
622
620
411
1.02
2.61
39.4
7.12
5.11
17.6
1.64
64.1
NA
NA
NA
NA
Eteccdi MCL?
No
No
No
No
No
No
No
No
Yes
Ye*
No
No
No
No
No
Yei
No
No
No
No
Yes
No
Yes
No
Yes
No
NA
No
Retalaed M
COC«
No
No
No
No
No
No
No
: No
No
Yes
No .
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Crvrad- Water Artlra
The nonhern part of OU-9 was evaluated, aloof with the South Docks area, against
preliminsiy remediation goals in Chapter 2. The Building 102 area (eastern part of OU-
9) will be addressed under stale petroleum release programs and not under CERCLA.
led Corrective Acuoo lo taonu POL cocttavnin>uon.
and reialed component* (BTF\).
No remediation required. CoMinued monitoring as pan of Buewide plan.
No remediation required.
ofjetruelandBTEXooostHuems.
NOTES:
(•) TtitK ckcmkih were drttCKd during dw OU-II ••cBijtiwii Md bccMM of **• ctMracwiiukv wtie nclwM • DM rnk mniaMal.
(») tlMt>*oMtciiiik«cfnceaMnctlfeBil«dWMMi(*>1kUCLM).
(O COCdtu(iMnor*(ibkiu«MM«. not ifctmiciti m fnvmt »*<& tao tcuttmrnmu tt toauieim M
lfc«« WM!I*< 'I » 10* (or cMcimtnuciokOf (HI >l (or
(d) focinwdiMioiipyfpowtaiily. TktOU-ll HUBMHokkRnkAucuaMMdWaMiarliidiBGOf OKHMMlyloveaiKtiwiuonorTCEweMdtMCieA HoiiieMr.
(t)
tdtnclfcrti
Mioii(BC04Pre-Doig.StetovmitaMi.ItUSTItH)«aicoa*iniil• tfxoff BM.BfiOXBCM«na
-------
TABLE 2 AREA 1 AND AREA 2 EXPOSURE POINT DATA
AREA
Area l(d)
Area 2 - BG04
Area 2 - BG05
POTENTIAL COCs('>
TCE
1,2-DCE
Bis(2-ethylhexyl) phthalate
beta BHC
1,2-DCE
benzene
ethylbenzene
PCE
toluene
TCE
xylenes
Bis(2-ethylhexyl) phthalate
beta BHC
gamma-chlordane
p,p'-DDT
TCE
Frequency
of
Detection
27/35
17/34
6/35
2/35
3/11
1/11
1/11
1/11
1/11
4/11
1/11
3/11
1/10
1/10
1/10
1/1
Range of
Detected
Values
Mg/L
1-7000
0.9-73
3-17
0.025
0.8-5
0.8
2
23
8
23-110
13
6-8
0.025
0.025
0.05
7
95%
UCLM
Cone.
Mg/L
680
13.1
6.07
0.014
2.15
1.02
1.29
7.47
3.05
43.7
4.52
6.10
0.017
0.017
0.034
NA
Retained
as
coc (e)
Yes
No
No \
No
No
No
No
Yes
No
Yes
No
No
No
No
No
Yes(e>
NOTES:
(a) These chemicals were detected during the OU-11 investigation and because of their characteristics.
were included in the risk assessment.
(b) The 95th percentile upper confidence limit on the mean (95% UCLM).
(c) COC designates chemicals of concern based on the results of the risk assessment. These chemicals
are present at high enough concentrations to contribute to risk above the minimum established level
for a particular risk assessment. For the EAFB risk assessment, these levels are >1 x 10"* for
carcinogenic risk or a HI >1 for noncarcinogenic risk. These are EPA guideline values and
remediation of chemicals above these risk levels is not always required.
(d) Data presented is from South Docks samples only. North Docks area is being addressed outside
CERCLA.
(e) For remediation purposes only. The OU-11 Human Health Risk Assessment did not include BG05
because only low concentrations of TCE were detected. However, because the concentration of TCE
in the ground-water sample collected during the RJ slightly exceeded the MCL and because of the
proximity of BG05 to the Base boundary, it is included as part of Area 2 (along with BG04) in
development of remedial alternatives.
JRON>0)7l'W/S\*OO\F(NAl-.TABJ FIN
-------
TABLE 3 SUMMARY OF SITE RISKS FOR THE SOUTH DOCKS AREA
Total Exposure Point Exposure Pathway
Future Onsiic 1 . Ground- Water
Residential Adults Ingestion
2. Volatile Inhalation/
DcmulContact
(Showering)
Chemical
of Concern
TCE
1,2-DCC
Bis(2-elhylhcxyl) phlhalate
betaBHC
PATHWAY TOTAL
TCE
1.2-DCE
Bis(2-ethylhexyl) phthalale
bcuBHC
PATHWAY TOTAL
Noncancer
Chronic Daily
Intake (COI)
(mg/kg-day)
I.86E-02
362E-04
I.67E-04
3.84E-07
I.86E-02
3.62E-04
I.67E-04
3.84E-07
TOTAL FOR FUTURE ONSITE RESIDENTIAL
Cancer
Chronic Daily
Intake (CDI)
(mg/kg-day)
7.98E-03
NA
7.I6E-OS
I.64E-07
7.98E-03
NA
7.I6E-05
I.64E-07
•
ADULTS
Cancer
SF
(mg/kg-day)1
I.IE-02
NA
I.4E-02
I.8E+00
I.IE-02
NA
I.4E-02
I.8E+00
Risk
(CDI x SF)
8.78E-05
NA
I.OOE-06
2.96E-07
8.91 E-OS
8.78E-05
NA
NA
NA
8.7SE-OS
I.77E-04
Noncancer
RID
(mg/kg-day)
6E-03
IE-02
2E-02
NA
6E-03
IE-02
NA
NA
Hazard Imlc*
(CDI /Rid)
3.IIE40U
3.62E-02
8.35E-OJ
NA
3.40E+00
3.IIE+00
3.62E-02
NA
NA
3. HE+OO
6.54E+00
-------
TABLE 4 SUMMARY OF SITE RISKS FOR THE BG04/BG05 AREA
Toial Exposure Point Exposure Pathway Chemical of Concern
Future Onsite 1. Ground- Water TCE
Residential Adults Ingestion PCE
xylenes
toluene
I.2-. c
ethylbenzene
benzene
Bis(2-elhylhcxyl) phthalale
betaBHC
gamma chlordane
p.p'-DDT
PATHWAY TOTAL
2. Volatile Inhalation/ TCE
Dermal Contact PCE
(Showering?* xylenes
toluene
1.2-DCE
elhylbenzene
benzene
Bis(2-elhylhexyl) phUuiate
beta Bl 1C
gamma chlordane
p.p'-DDT
PATH WAY TOTAL
Noncancer
Chronic Daily
Intake (CDI)
(mg/kg-day)
I.20E-03
2.04E-04
I.24E-04
8.37E-OS
5.90E-05
3.55E-05
2.I9E-OS
I.67E-04
4.66E-07
4.66E-07
9.32E-07
I.20E-03
2.04E-04
I.24E-04
8.37E-05
5.90E-05
3.55E-05
2.I9E-05
I.67E-04
4.66E-07
4.66E-07
9.23E-07
Cancer
Chronic Daily
Intake (CDI)
(mg/kg-day)
5.I3E-04
8.75E-05
NA '
NA
NA
NA
9.39E-06
7.I6E-05
2.00E-07
2.00E-07
3.99E-07
5.I3E-04
I.75E-05
NA
NA
NA
NA
9.39E-06
7.I6E-05
2.00E-07
2.00E-07
3.99E-07
Cancer
SF
(mg/kg-day)'1
I.IE-02
5.2E-02
NA
NA
NA
NA
2.9E-02
I.4E-02
I.8E+00
I.3E+00
3.4E-OI
I.IE-02
5.2E-02
NA
NA
NA
NA
2.9E-02
I.4E-02
I.8E+00
I.3E+00
3.4E-OI
TOTAL FOR FUTURE ONSITE RESIDENTIAL ADULTS
Risk
(CDI x SF)
5.64E-06
4.55E-06
NA
NA
NA
NA
2.72E-07
I.OOE-06
3.59E-07
2.59E-07
I.36E-07
I.22E-05
5.64E-06
4.SSE-06
NA
NA
NA
NA
2.72E-07
NA
NA
NA
NA
I.05E-05
2.27E-05
Noncancer
RID
(mg/kg-day)
6E-03
IE-02
2E+00
2E-OI
IE-02
IE-01
NA
2E-02
NA
6E-OS
SE-04
6E-03
IE-02
2E+00
2E-OI
IE-02
IE-01
NA
2E-02
NA
6E-OS
SE-04
Hazard Index
(CDI/Rfd)
I.99E-OI
2.04E-02
6.ISE-OS
4.I8E04
5.90E-03
3.55E-04
NA
8.35E-03
NA
7.76E-03
I.86E-03
2.47E-OI
I.99E-OI
2.04E-02
6.I5E-05
4.I8E-0-1
5.90E-03
3.55E-04
NA
NA
NA
NA
NA
2.27E-OI
4.74E-OI
-------
TABLE 4 (CONT1UNED)
Tola) Exposure Point Exposure Pathway Chemical of Concern
Noncancer Cancer
Chronic Daily Chronic Daily
Intake (CDI) Intake (CDI)
(mg/kg-day) (mg/kg-day)
Cancer
Noncancet •
SF Risk RfD Hazard Index
(mg/kg-day)'1 (CDIxSF) (mg/kg-day) (CDI/Rfd)
Future Offsile
Residential Adults
1. Ground- Water TCE I.20E-03 S.I3E-04
Ingestion
PATHWAY TOTAL
2. Volatile Inhalation/ TCE I.20E-03 5.I3E-04
Dermal Contact
(Showering?"
PATHWAY TOTAL
TOTAL FOR FUTURE OFFSITE RESIDENTIAL ADULTS
I.IE-02 3.64E-06 6E-03
5.64E-06
I.IE-02 5.64E-06 6E-03
S.64E-06
I.I3E-OS
I.99E-OI
I.99E-OI
1.99E-OI
I.99E-OI
3.99E-OI
NOILS:
(a) The combined risk from volatile inhalation/dermal contact (i.e., showering) is the same as that for ingestion of ground water.
-------
TABLE 5
EVALUATION OF FEDERAL AND STATE ARARS
Potentially Applicable or Relevant and Appropriate Federal Standards. Requirement*. Criteria and Limitations
•v
Citations Description
Standard Requirement, Criteria, or
Limitation
ARARType
Applicability to OU-11
Safe Drinking Watar Act 42 USC 300g
National Primary Drinking Water 40 CFR Part 141
Standards
National Secondary Drinking Water 40 CFR Part 143
Standards
Maximum Contaminant Level Goals Pub. 1. No. 00-330.100 Slat 642
(1080)
Clean Water Ad 33 USC 1251-1376
Water Quality Criteria 40 CFR Pan 131
Criteria and Standards lor the National 40 CFR 125
Pollutant Discharge Elimination
General Pretreatment Regulation* for 40 CFR 403
Existing and New Sources o» Ponution
Guidelines Establishing Test Procedures 40 CFR 130
tor the Analysis of PoUuUnt*
Establishes health based standards for
public water systems (maximum
contaminant levels)
Establishes welfare based standards lor
the public water systems (secondary
maximum contaminant levels)
Establishes drinking water quality goals
set at levels of unknown or anticipated
adverse health effects, with an adequate
margin of safety
Sets criteria for water quality based on
toxlcity to aquatic organisms and human
health
Establishes criteria and standards for
technology-based requirements In
permit* under the CWA
Establishes responsibilities of federal,
state, and local government and of the
POTW in providing guidelines for and
developing, submitting, approving, and
modifying state pretrealment programs.
Specifies standards for pretrealment.
Specify analytical procedures for
NPDES applications and reports
Chemical
Chemical
Chemical
Chemical
Chemical
Action
Relevant and appropriate for
Federal Class II aquifer.
Relevant and appropriate.
Relevant and appropriate.
Action
Relevant and appropriate. Aquifer
may be a Federal Class IIA
(discharge to surface water).
Applicable for discharge to surface
waler.ortoEAFBWWTP
Applicable for discharge to EAFB
WWTP.
Applicable for treatment and
discharge of ground water.
-------
TABLE 5 (cont.)
Standard Requirement Criteria, or
Limitation
Citations
Description
ARARType
Applicability to OU-11
Clean Air Act
National Primary and Secondary
Ambient Air Quality Standard
National Emission Standard* lor
Hazardous A* Potutants
Resource Conservation and Recovery
Act
Hazardous Waste Management
System: General
Identification and Listing of
Hazardous Wastes
40CFRPartSO
40CFRPart61
40 CFR Part 260
40 CFR Part 261
Standards Applicable to Generators 40 CFR Part 262
of Hazardous Wastes
Standards Applicable to Transporters 40 CFR Part 263
of Hazardous Wastes
Establishes standard tor ambient air
quality to protect pubfe health and
welfare.
Establishes regulatory standard for
specific eh* poflutaiils.
Establishes definitions as we* as
procedures and crtterta tor modification
or revocation of any provision In 40 CFR
Parts 260-265
Defines those solid wastes which are
subject to regulations as hazardous
wastes under 40 CFR Parts 262-265
Establishes standards for generator* of
hazardous wast*
Establishes standards which apply to
parsons transporting hazardous waste
within the U.S. If the transportation
requires a manifest under 40 CFR Part
262
Action
Action
Action
Action
Action
Action
Applicable.
Applicable tor alternatives which
require dbctargt to BM ak Htowtno
treatment
Applicable tor identifying hazardous
waste during we! placement, or
trenching at OU-11.
Applicable for Identifying hazardous
waste during wen placement, or
trenching at OU-11.
Applicable tor transport of
hazardous materials off-site.
Applicable for any transport of
hazardous materials off-site.
Toxic Substances Control Act (TSCA)
Fish and Wildlife Coordination Act
40 CFR Pert 761
16 USC 1531-666
40 CFR 6.302(fl)
Substances regulated under this rule
Include, but are not limited to. pots end
other material* contaminated as e result
of spite
Requires consultation when a federal
department or agency proposes or
authorizes any modification of a stream
provision for protection of fish end
w*Me resources
Action
Acton
NotanARAR.
Not an ARAR.
-------
TABLE 5 (cont.)
Standard Requirement. Criteria, or
Limitation
Citations
Descnption
ARARType
Applicability to OU-11
Endangtred Species Act
Archaeological and Historic Pmarvatlon
Act
16USC1S3M543
SO CFR Part* 17. 402
40 CFR 6.302(g)
16 USC 469
40 CFR 6 301(c)
Archaeological Resource* Protection Act
(1979)
Executive Order on Ftoodplalna
Management
Executive Order on Protection ol
Wetland*
63 Slat. 721
18 USC 470
Exec order No 11.986
40 CFR 6.302(b) & Appendix A
Exec Order No. 11.990
40 CFR 6.302(a) & Appendix A
Requires that Federal agencies Insure
that any action authorized, funded, or
carried out by the agency is not likely to
jeopardize the continued existence of
any threatened or endangered species
or destroy or adversely modify critical
haMat
Establishes procedures to provide lor
preservation of historical and
archaeological data which might be
destroyed through alteration of terrain as
a result of federal construction project
for a federal licensed activity or
program.
Requires a permit for an excavation or
removal of archaeological resources
from public or Indian land.
Requires federal agencies to evaluate
the potential effect* of actions they may
take in a floodptain to avoid, to the
extent possible', the adverse impacts
associated with direct and indirect
development of a Itoodpiain
Requires federal agencies to avoid, to
the extent possible, the adverse impacts
associated with the destruction or toss
of wetlands and to avoid support of new
construction in wetlands if a practicable
alternative exists
B. Potentially Applicable or Relevant and Appropriate State Standards. Requirements. Criteria, and Limitations
South Dakota Air Pollution Control Rule*
South Dakota Water Discharge Permit
Rule*
South Dakota Water Discharge Permit
Rules
South Dakota Water Discharge Permit
Rules
ARSD 74:26:01:09. 24. 25. 26-28
ARSD 74:03:16:01-17
ARSO 74:03.19 01-08
ARSO 74:03:01
Establishes permit requirements for
construction, amendment and operation
of air discharge services
Establishes surface water discharge
permit applications requirements
Establishes surface water permit
conditions
Establishes requirements for Individual
and small onsite wastewater systems
Location/Action
Applicable for MW93BG04 Area.
Location
NotanARAR.
Acton/location
Location
Action/Location
NotanARAR.
Not an ARAR. Area not in 100-year
ftoodpUin.
NotanARAR. MW93BG04and
South Docks Areas do not have
identified wetland areas.
Action
Action
Action
Action
Applicable
Applicable for any groundwater
treatment discharge
Applicable for any groundwater
treatment discharge
Applicable for any groundwater
treatment plant
-------
TABLE5(cont.)
Standard Requirement Criteria, or
Limitation
Citation*
Description
ARARType
AppUotiytyloOU.il
South Dakota Watar Quality Standards
South Dakota Ground Water Standards
ARSD 74:03:04 02.10
ARSD740315
Defines use of Boxelder Creek and
certain tributaries.
Defines ground water classifications by
beneficial uso and ssjts chernlcfll
• tBM«4an4a
SUnoafOS.
Action Applicable for any groundwatar
treatment discharge to BoxeMer
Creek.
Chemical Applicable in evaluating the
beneficial use of impacted
grounoVrater.
t;:\raOIV«03?U}\FSU>tFTFINL\2-I.TAB\)l Marak IW7
-------
Final Record of Decision Operable Unit 11
Ellsworth Air Force Base. South Dakota
APPENDIX C
RESPONSIVENESS SUMMARY
F:\PROJW)m90\FS\ROD\FMAL\OUIlROD.FtN April. 1997
-------
Final Record of Decision Operable Unit 11
Ellsworth Air Force Base, South Dakota
Responsiveness Summary
Remedial Action at Operable Unit 11
Ellsworth Air Force Base, South Dakota
1. Overview
The United States Air Force (US AF) established a public comment period from February 10 to
March 10, 1997 for interested parties to review and comment on remedial alternatives considered
and described in the Proposed Plan for Operable Unit Eleven (OU-11). The Proposed Plan was
prepared by the USAF in cooperation with the U. S. Environmental Protection Agency (EPA)
and the South Dakota Department of Environment and Natural Resources (SDDENR).
The USAF also held a public meeting at 7:00 p.m. on February 19,1997 at the Douglas Middle
School in Box Elder, South Dakota to outline the proposed remedy to reduce risk and control
potential hazards at Operable Unit 11.
The Responsiveness Summary provides a summary of comments and questions received from
the community at the public meeting and during the public comment period as well as the
USAF's responses to public comments.
The Responsiveness Summary is organized into the following sections:
• Background on Community Involvement
• Summary of Comments and Questions Received During the Public Comment Period and
USAF Responses
• Remaining Concerns
OU-11 has been divided into two areas to aid in project planning. Area I is the South Docks
Study Area, and Area 2 is the BG04 and BG05 Study Areas.
The selected alternative for Area 1, Ground*Water Extraction and Treatment with Containment,
includes the following major components:
• Ground-water removal and treatment in the South Docks Study Area.
• On-Base containment of ground water containing contaminants at concentrations above
Federal Maximum Contaminant Levels (MCLs) and State of South Dakota Ground-
Water Quality Standards.
• Institutional controls and long-term monitoring.
F:\PROJ\6037890\FSWOD\FMAL\OUIiRODFIN C-l April. 1997
-------
Final Record of Decision Operable Unit 11
Ellsworth Air Force Base, South Dakota
The selected alternative for Area 2, Ground-Water Containment/Extraction and Treatment,
includes the following major components:
• Ground-water removal and treatment along the northeast Base boundary and at areas of
high contaminant concentrations on-Base.
• Natural attenuation of low contaminant concentration areas, primarily off-Base.
• Alternative water supply to residents affected by contamination coming from the Base.
• Additional investigation to determine the eastern extent of off-Base ground-water
contamination.
• Institutional controls and long-term monitoring.
Collectively, the selected remedies for Area 1 and Area 2 constitute the entire remedial action for
OU-llatEAFB.
2. Background on Community Involvement
On August 30, 1990 EAFB was listed on the EPA's National Priorities List (NPL). A Federal
Facilities Agreement (FFA) was signed in January 1992 by the Air Force, EPA, and
the State and went into effect on April 1, 1992. The FFA establishes a procedural framework
and schedule for developing, implementing, and monitoring appropriate response actions for
EAFB.
• Community relations activities that have taken place at EAFB to date include:
• FFA process - After preparation of the FFA by the USAF, EPA, and SDDENR, the
document was published for comment. The FFA became effective April 1, 1992.
• Administrative Record - ,^n Administrative Record for information was established in
Building 8203 at EAFB. The Administrative Record contains information used to
support USAF decision-making. All the documents in the Administrative Record are
available to the public.
• Information repositories - An Administrative Record outline is located at the Rapid
City Library (public repository).
• Community Relations Plan (CRP) - The CRP was prepared and has been accepted by
EPA and the State of South Dakota and is being implemented. This plan was updated in
1996.
• Restoration Advisory Board (RAB) - The RAB has been formed to facilitate public
input in the cleanup and meets quarterly. In addition to USAF, EPA, and South Dakota
F:\PROMOm90\FSWOD\FINAL\QUIIRODFlN <>2 <*P"I. 1997
-------
Final Record of Decision Operable Unit 11
Ellsworth Air Fore* Bast, South Dakota
oversight personnel, the RAB includes community leaders and local representatives from
the surrounding area.
• Mailing list - A mailing list of all interested parties in the community is maintained by
EAFB and updated regularly.
• Fact sheet - A fact sheet describing the status of the IRP at EAFB was distributed to the
mailing list addressees in 1992. A remedial design fact sheet was distributed in October
1996.
• Open house - An informational meeting on the status of the IRP and other environmental
efforts at EAFB was held on May 6, 1993. An open house format was also used during
the November 16, 1995 Restoration Advisory Board meeting. In addition, during 1996
the Air Force has met with community members numerous times to inform them about
ongoing investigations at OU-11.
• Newspaper articles - Articles have been written for the Base newspaper regarding IRP
activity.
• Proposed Plan - The proposed plan on this action was distributed to the mailing list
addressees for their comments.
The Proposed Plan for this remedial action was distributed to the mailing list addressees for their
comments, and additional copies of the Proposed Plan were available at the February 19,1997
public meeting. A transcript of comments, questions and responses provided during the public
.meeting was prepared.
3. Summary of Comments and Questions Received During the Public Comment Period
and USAF Responses
Part I - Summary and Response to Local Community Concerns
In review of the written transcript of the public meeting, there were no community objections to
the proposed remedial action indicated. No written comments were received during the public
comment period.
The majority of the comments received during the public meeting were in the form of questions
about the remedial investigation findings and the remedial action (i.e., what would be done, how
it would be done, and what effects the action might have). Representatives of the USAF were
available to provide answers to the questions and also provided an overview presentation during
the meeting to describe the proposed actions.
F:\J>ROJ(6037890\FSVtOD\flNAL\OUimOD.FIN C-3 April. 1997
-------
Final Record of Decision Operable Unit 11
Ellsworth Air Force Base. South Dakota
Part II - Comprehensive Response to Specific Technical, Legal and
Miscellaneous Questions
The comments and questions below have been numbered in the order they appear in the written
transcript of the 19 February 1997 public meeting.
Comment 1. Mr. Myron Mann
Asked for clarification on whether the containment portion of remedial action for the
BG04/BG05 would "pump the plume completely dry" prior to injecting the treated water
back into the ground.
Response 1: As water flows to the Base boundary, in the soil, the water would be pumped from
the ground and treated. Treated ground water will be injected into the ground.
[Treated ground water will be discharged to the Base Waste Water Treatment
Plant, a surface water drainage, or be injected back into the aquifer based upon
results of predesign studies. The ground-water containment system will prevent
ground water and contaminants from moving beyond the Base boundary.
However, if water is injected back into the ground, the aquifer will be replenished
and wells beyond the Base boundary will not go dry due to remedial action
activities. If the aquifer is being replenished with water from other areas beyond
the Base boundary, then reinjection of the treated water may not be necessary.]
Comment 2. Mr. Myron Mann
Asked whether that meant that every drop of water within the plume areas would be removed
from the ground.
Response 2: Not every drop of water within the plume area would be removed from the
ground. The goal is to contain the contamination on-Base and prevent further
movement off-Base. This is similar to what has been done at other areas at
Ellsworth Air Force Base and is a common practice to prevent movement of
contaminants off-Base. Injecting the treated water into the ground has the
advantage of speeding up the process of diffusing and dispersing contamination
that exists downstream. If the majority of the water is removed and not injected
back into the ground, then there would be no more ground water flowing
downgradient at the Base boundary.
[However, the aquifer may be receiving water from beyond the Base boundary
which would ensure a continuous supply of water to downgradient
uncontaminated drinking water wells.]
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Final Record of Decision Operable Unit 11
Ellsworth Air Force Base. South Dakota
Response 3: Based on a model type called a batch flush model, it was estimated that the time it
would take for natural processes to reduce chemical concentrations to acceptable
levels, assuming the source of the contamination is cut off (i.e., contained on-
Base), would be 14 years.
Comment 4. Lt Colonel McBride
Asked if chemicals in the water that are taken up into the plants during phytoremediation
remain in the plant and if so, is there any risk to humans or animals (wild or domestic) that
may eat the plants.
Response 4: Available information indicates that the majority of organic chemicals taken up
into the plants pass completely through them with the water. The rest of the
chemicals are broken down by the plant into non-hazardous substances such as
carbon dioxide.
4. Remaining Concerns
Based on review of the transcript of the oral comments received during the public meeting, there
are no outstanding issues associated with implementation of the proposed remedial action.
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