EPA Superfund
Record of Decision:
PB96-964409
EPA/ROD/R08-96/121
October 1996
Ellsworth Air Force Base,
Operable Unit 4, Rapid City, SD
5/10/1996
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Final
Record of Decision for
Remedial Action at Operable Unit 4
Ellsworth Air Force Base, South Dakota
United States Air Force
Air Combat Command
Ellsworth Air Force Base
April 1996
AF Project No. FXBM 94-7002
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Final Record of Decision Operable Unit 4
Ellsworth Air Force Base, South Dakota
TABLE OF CONTENTS
Chapter Page
1.0 DECLARATION FOR THE RECORD OF DECISION 1-1
1.1 SITE NAME AND LOCATION .1-1
1.2 STATEMENT OF BASIS AND PURPOSE 1-1
1.3 ASSESSMENT OF THE SITE 1-1
1.4 DESCRIPTION OF SELECTED REMEDY 1-1
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 OPERABLE UNIT 4 (OU-4) DESCRIPTION/HISTORY AND
REGULATORY OVERSIGHT ACTIVITIES 2-1
2.2.1 Description/History 2-1
2.2.2 Regulatory Oversight Activities 2-2
2.3 HIGHLIGHTS OF COMMUNITY PARTICIPATION 2-3
2.4 SCOPE AND ROLE OF RESPONSE ACTION 2-4
2.5 SITE CHARACTERISTICS 2-5
2.5.1 Soils 2-5
2.5.2 Sediment 2-6
2.5.3 Ground Water 2-6
2.6 SITE RISK SUMMARY 2-7
2.7 DESCRIPTION OF ALTERNATIVES 2-10
2.8 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES 2-12
2.8.1 Overall Protection of Human Health and the Environment 2-13
2.8.2 Compliance with ARARs 2-14
2.8.3 Long-Term Effectiveness and Permanence 2-15
2.8.4 Reduction of Toxicity, Mobility, and Volume Through Treatment 2-16
2.8.5 Short-Term Effectiveness 2-16
2.8.6 Implementability 2-17
2.8.7 Cost 2-17
2.8.8 State Acceptance 2-19
2.8.9 Community Acceptance 2-19
2.9 SELECTED ALTERNATIVE 2-20
•2.10STATUTORY DETERMINATIONS 2-23
2.10.1 Protection of Human Health and the Environment 2-23
2.10.2 Compliance with ARARs ! 2-24
2.10.3 Cost Effectiveness 2-24
2.10.4 Utilization of Permanent Solutions and Alternative Treatment
Technologies to the Extent Possible 2-24
2.10.5 Preference for Treatment as a Principal Element 2-25
2.11 DOCUMENTATION OF SIGNIFICANT CHANGES , 2-25
3.0 LIST OF ACRONYMS AND ABBREVIATIONS 3-1
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Final Record of Decision Operable Unit 4
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APPENDICES
Appendix A Figures
Appendix B Responsiveness Summary
LIST OF FIGURES
Figure 2-1 Area Location Map
Figure 2-2 Site Location Map
Figure 2-3 OU-4 Location Map Showing Underground Utilities and Areas of Fill
Figure 2-4 OU-4 Ground Water Area of Attainment
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1.0 DECLARATION FOR THE RECORD OF DECISION (ROD)
1.1 SITE NAME AND LOCATION
• Operable Unit 4 (OU-4), Landfill No. 3 Area, Ellsworth Air Force Base (EAFB),
National Priorities List Site.
• Meade and Pennington Counties, South Dakota
1.2 STATEMENT OF BASIS AND PURPOSE
This decision document describes EAFB's selected remedial action for Operable Unit 4 (OU-4),
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-4, EAFB. The US
Environmental Protection Agency (EPA) and the South Dakota Department of Environment and
Natural Resources (SDDENR) concur with the selected remedial action.
1.3 ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from OU-4, if not addressed by
implementing the response action selected in this Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare, or the environment.
1.4 DESCRIPTION OF SELECTED REMEDY
Twelve operable units (OUs), have been identified at EAFB. This ROD is for a remedial action at
OU-4 and is the sixth ROD for EAFB.
The selected alternative for the landfill, soil cover, includes the following major components:
• Institutional controls for the landfill area;
• Placing a soil cover capable of sustaining perennial vegetation over the landfill area;
• Landfill gas monitoring and passive collection system, as necessary;
• Long-term monitoring and maintenance.
The selected alternative for the ground water, pump and treat, includes the following major
components:
• Continued operation of the interim remedial action (IRA) which consists of removal and
treatment of contaminated ground water;
• Installation of recovery trenches and/or additional extraction wells to be added to the
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existing IRA ground-water recovery system.
• Treatment of removed ground water at the treatment plant built for the IRA.
• Discharge of treated ground water to a surface water drainage, to the Base wastewater
treatment plant, or by underground injection.
1.5 STATUTORY DETERMINATION
The selected remedy is protective of human health and the environment, complies with Federal
and State of South Dakota requirements that are legally applicable or relevant and appropriate to
the remedial action, and is cost-effective. This remedy utilizes permanent solutions and
alternative treatment (or resource recovery) technologies, to the maximum extent practicable for
OU-4. However, because treatment of the principal threats of potential contaminants in the
landfill was not found to be practicable, the landfill remedy does not satisfy the statutory
preference for treatment as a principal element. The size of the landfill and the fact that there are
no apparent on-site hot spots that represent major sources of contamination preclude a remedy in
which contaminants could be excavated and treated effectively. The remedy for ground water
satisfies the statutory preference for treatment as a principal element.
Because this remedy will result in low levels of hazardous substances remaining on-site beneath
the landfill cover area, a review will be conducted at least every five years after signing the ROD
to ensure that the remedy continues'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
Lieutenant General, USAF
Vice Commander
Date
~
ACK W. MCGRAW
Acting Regional Administrator
US Environmental Protection Agency Region 8
Date
NETTIE H. MYERS, Scrediry
Department of Environment and Natural Resources
State of South Dakota
Date
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1.6 SIGNATURE AND AGENCY CONCURRENCE ON THE REMEDY
BREffM. DULA Date
Lieutenant General, USAF
Vice Commander
JACKW. MCGRAW Date
Administrator
US Environmental Protection Agency Region 8
NETTIE H. MYERS, Secretary Date
Department of Environment and Natural Resources
State of South Dakota
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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 2-1).
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-
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 OPERABLE UNIT 4 (OU-4) DESCRIPTION/HISTORY AND REGULATORY
OVERSIGHT AdTVnTES
2.2.1 Description/History
Ellsworth Air Force Base (EAFB) was officially activated in July 1942 as the Rapid City Army
Air Base, a training facility for B-17 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.
OU-4 consists of Landfill No. 3 which is approximately 35-40 acres in size and is located in the
southwestern corner of EAFB (Figure 2-3). The landfill was active between 1965 and 1976 as a
trench and fill operation. The trenches were approximately 13 to 15 ft deep. One open trench
was used for disposal of construction demolition debris during the mid-1980s. Digested
wastewater treatment plant biomass was also added to the landfill at this time. A recent
examination of 1946 and 1952 aerial photographs of EAFB indicated that some landfill activity
may have occurred prior to 1965. Solid waste generated on-Base has been disposed of by
contract at an off-Base sanitary landfill since 1976.
Shop wastes (liquids and paints), industrial sewer sludge and oils, and miscellaneous refuse were
placed in Landfill No. 3. During the mid-1970s, a gravel-filled waste-oil pit was operated in the
southwest comer of the OU for about one year. The contents of approximately 100 55-gallon
drums containing waste oil and fuel were placed in the waste-oil pit. Prior to 1982, the southwest
corner of OU-4 was also used as a staging area for 55-gallon drums containing waste oil and fuel.
Recently, the southwest corner of OU-4 was used to stage asphalt rubble. The asphalt nibble
was removed in the fall of 1993. The exact locations of the waste pit and drum staging area are
not known, but are presumably in the vicinity of the former asphalt waste pile area. During 1982
and 1983, OU-4 was used as a disposal site for soil containing Pramitol, a herbicide, and sodium
chromate, a launch facility coolant.
The topography at OU-4 is fairly level, with a slight slope toward the south and east, and a few
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broad, shallow depressions. The western portion of the OU slopes gently toward the west. A
series of east-west trending depressions are visible on aerial photographs, and are assumed to be
the surface reflection of historical trench and fill operations.
A shallow aquifer has been identified at depths of 10 feet to 50 feet beneath the ground surface at
EAFB. The top of the shallow aquifer at OU-4 varies seasonally, but is generally 14 ft to 32 ft
below the ground surface. This ground water is classified as having a beneficial use as a drinking
water supply suitable for human consumption (ARSD Chapter 74:03:15, Groundwater Quality
Standards). The shallow aquifer may also discharge to the surface. However, no known seeps or
springs were identified at OU-4.
Deeper bedrock aquifers also exist beneath EAFB. These deeper aquifers are separated from the
shallow aquifer by 800 feet of low-permeability clays and silts. In the past, EAFB utilized these
deeper aquifers for its water supply. Presently, EAFB obtains its potable water from the Rapid
City Municipal Distribution System.
2.2.2 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 ERP 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 U.S. 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 (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 in accordance with the Comprehensive
Environmental Response, Compensation, and Liabilities 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). It also states the oversight procedures
for EPA and the State to ensure Air Force compliance with the specific requirements. The FFA
identified 11 site-specific operable units (OUs) and a Base-wide ground-water operable unit. 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. In 1993 and 1994, an
extensive PJ field program was conducted to characterize conditions at OU-4. 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
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risks, and review and compilation of previous IRP investigations. Collection and laboratory
analysis of soil, ground-water, and sediment samples were included in the RI field program.
A ROD for an interim remedial action (IRA) for OU-4 was signed on 16 May 1995. The
objectives of the IRA were (1) to prevent additional transport of contaminated ground water
beyond the Base boundary and (2) to remediate ground water in areas which contained higher
concentrations of contaminants beyond the Base boundary. The IRA consists of removing
contaminated ground water using ground-water wells, and treatment of the contaminated ground
water consisting of filtration, air stripping, and activated-carbon adsorption. The treatment
system was constructed as part of the IRA.
2.3 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 USAF, 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
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. An update to this plan
will be prepared 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.
• 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.
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• 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.
A public comment period was held from September 18 to October 18, 1995, and a public meeting
was held on September 26, 1995, 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-4, in accordance with
the CERCLA, as amended by SARA, and the NCP. The RI/FS reports and the Proposed Plan for
OU-4 provide information about OU-4 and the selected remedy. These documents are available at
the Information Repositories at EAFB and the Rapid City Public Library.
2.4 SCOPE AND ROLE OF RESPONSE ACTION
The FFA identified 11 site-specific OUs and a Base-wide ground-water OU. The 12 operable
units are identified as follows:
OU-1 Fire Protection Training Area
OU-2 LandfillsNos. land6
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 Base-wide Ground Water
OU-12 HardfillNo. 1
This ROD documents the selected remedial action (RA) at OU-4 and is the sixth ROD for EAFB.
The remedial action objectives (RAOs) are to reduce the potential risks posed by contaminants in
surface soils and ground water, to reduce the mobility of potential contaminants in the landfill
through containment, and to prevent ingestion of contaminated ground water.
The development of alternatives for the landfill was conducted under EPA's Presumptive
Remedies Approach [Presumptive Remedies: Policy and Procedures (OSWER Directive
9355.0-47FS); Presumptive Remedy for CERCLA Municipal Landfill Sites (OSWER Directive
9355.0-49FS)y. Selection of an alternative for remediation was streamlined by using preferred
technologies based on historical patterns of remedy selection and EPA's scientific and engineering
evaluation of performance data on technology implementation.
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The presumptive remedy stipulates containment as the appropriate remedy for landfills. The
response action, containment by soil cover, would minimize risk associated with the ingestion,
dermal contact, and inhalation exposure pathways. The response action for ground water at
OU-4, pump and treat, would minimize risk associated with the ingestion, dermal contact, and
inhalation exposure pathways.
The area of attainment defines the area over which preliminary remediation goals would be
achieved, and is based on the RAOs. The area of attainment for the landfill includes areas not
meeting appropriate closure standards. The area of attainment for ground water is defined by
those areas beyond the landfill boundary with contaminants at concentrations above remediation
goals.
2.5 SITE CHARACTERISTICS
This section describes the presence and distribution of contaminants at OU-4 as a result of past
activities.
2.5.1 Soil
Volatile Organic Compounds (VOCs)
Sixteen separate VOCs were reported in soil samples from OU-4. Toluene was the only reported
VOC in surface soil samples. Acetone, toluene, ethylbenzene, xylenes,
octamethylcyclotetrasiloxane, trichloroethene (TCE), and 1,2-total-dichloroethene were the most
commonly reported VOCs in subsurface soil samples. Octamethyltetrasiloxane is a laboratory
artifact, and not a site contaminant. No specific pattern of VOC contamination exists in the •
surface or subsurface soil.
Polynuclear Aromatic Hydrocarbons (PAH)
Four soil samples taken from locations within Landfill No. 3 contained PAH, o-cresol and
p-cresol. Benzo(a)pyrene was reported in three surface soil samples. Other than tentatively
identified compounds, octamethylcyclotetrasiloxane and di-n-butyl phthalate, no semivolatile
organic compounds (SVOCs) were reported in the off-Base soil samples.
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Jet Fuel
Jet fuel was not reported in surface soil samples. Jet fuel was reported in six subsurface soil
samples taken within Landfill No. 3, at a maximum concentration of 1,100 mg/kg.
Pesticides and Polychlorinated Biphenyls (PCBs)
Twenty different pesticides and two PCBs were reported in soil samples. The highest frequency
of reported pesticides were from surface soil samples collected within Landfill No. 3. Reported
pesticides are believed to be a result of normal pesticide application practices on the surface,
rather than disposal of waste product.
Inorganic Analytes
Eight inorganic compounds were reported above background in OU-4 surface soil samples.
Calcium and magnesium were the inorganic analytes most frequently reported above background
concentration. Sixteen inorganic analytes were reported above background levels in OU-4
subsurface soil samples. Lead, silver, and zinc were reported at 4, 250, and 18 times,
respectively, above the background range in one subsurface sample.
Dioxin/Furan
Reported dioxin/furan included: 2,3,7,8 tetrachlorodibenzofuran; 1,2,3,4,6,7,8
heptachlorodibenzo-p-dioxin and furan; and octachlorodibenzo-p-dioxin and furan. The
international toxic equivalents were below the 1,000 picograms per gram (pg/g) level of concern
for residential soil.
2.5.2 Sediment
One sediment sample was taken during the 1993 RI. This sample was taken from an off-Base
ephemeral stream channel downgradient of OU-4. Reported analytes included acetone in the
duplicate analysis only, eight separate PAH compounds, three pesticide compounds, and inorganic
compounds.
2.5.3 Ground Water
Organic Contaminants
TCE and total dichloroethene (DCE) were the most frequently reported VOCs in ground-water
samples. TCE, vinyl chloride, and 1,2-dichloropropane were reported in samples taken from the
shallow aquifer at or above the Maximum Contaminant Level (MCL). Sample results from OU-4
monitoring wells indicate chlorinated hydrocarbons were reported in ground-water samples from
four general areas. The first area extends from the center of Landfill No. 3 south past the Base
boundary approximately 2,000 feet. The second area is in the southwestern corner of the landfill,
and extends off-Base to the south and southwest. There is some indication that these two areas
may be interconnected. The third area is an isolated occurrence in the northeast comer of the
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OU. A fourth area is in the vicinity of the control tower.
Off-Base ground-water samples were taken from seven domestic and three livestock wells. Five
different analytes including: trichloroethane (TCA), dichloroethane (DCA), total DCE, acetone
and TCE were reported. The highest concentrations were reported in samples from the livestock
wells. Off-Base sampling of domestic and livestock wells has been conducted since 1990.
Results from the first two sampling events conducted in 1990 reported four separate VOCs.
Results from the third sampling event reported seven different VOCs. The MCL for TCE was
exceeded in two instances during the off-Base investigations. Concentrations of 75 ug/L were
reported in a sample from a livestock well and 25 ug/L in a domestic well. As a result, the
domestic well was taken out of service in July 1991. Quarterly off-Base ground-water monitoring
was implemented by the Air Force in February 1994. One incidence of TCE above the MCL
occurred in a December 1994 sample.
Nineteen different SVOCs analytes were reported in ground-water samples from OU-4.
Bis(2-chloroethyl)ether and 1,4-dichlorobenzene were the most frequently reported SVOCs in
ground-water samples. 1,2,4-trichlorobenzene was reported once above the MCL of 70 ug/L.
Pentachlorophenol was reported once at 1 ug/L, equal to the MCL.
Fourteen different pesticides were reported in eight ground-water samples. Aldrin, alpha-BHC,
beta-BHC, heptachlor, and heptachlor epoxide were the most frequently reported pesticides in
OU-4 ground-water samples. The highest reported pesticide value was for prometon, which was
reported once at a concentration of 0.95 ug/L.
Inorganic Contaminants
Seventeen inorganic compounds exceeded background ranges in ground-water samples.
Antimony, cadmium, manganese, lead, nickel, and selenium were reported at values that exceeded
the MCL in at least one sample. However, antimony, manganese, and selenium were also
reported in background samples above the MCL, and are believed to naturally occur at higher
concentrations in the area.
2.6 SITE RISK SUMMARY
Human Health Risks
Risk Assessment Process
The assessment of human health risks for this OU considered the following topics:
(1) Contaminants of concern (COCs) in ground-water, sediment, and soil samples taken at
OU-4;
(2) Current and future land-use conditions;
(3) Potential environmental pathways by which populations might be exposed;
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(4) Estimated exposure point concentrations of COCs;
(5) Estimated intake levels of the COCs;
(6) ToxicityoftheCOCs;and
(7) Uncertainties in the assessments of exposure, toxicity, and general risks.
Noncarcinogenic and carcinogenic risks were calculated for the following six potential exposure
groups:
(1) Current EAFB maintenance personnel mowing grass on-site;
(2) Current off-Base residential use of ground water;
(3) The future adult living on-site who ingests surface soil;
(4) The future child/adult living on-site who ingests and showers with shallow ground water;
(5) The future child/adult living off-site who ingests and showers with shallow ground
water;
(6) Future adult construction workers who excavate on-site for building residences.
A quantitative risk assessment was performed for the ground water, soil, sediment, and air. The
risk assessment evaluated potential effects on human health posed by exposure to contaminants
within OU-4. Carcinogenic risks were estimated as the incremental probability of an individual
developing cancer over a lifetime as a result of exposure to a potential cancer causing chemical.
The acceptable risk range expressed as a probability is one cancer incident in ten-thousand people
to one cancer incident in a million people. This level of risk is also denoted by 1 x 10"4 to 1 x 10"6.
Risks within the acceptable risk range may or may not warrant remedial action depending upon
site-specific circumstances. Risks below this range cannot be differentiated from the background
occurrence of cancer in human populations. Risks calculated in a risk assessment are .potential
risks and are excess (i.e., over background) cancer risks due to exposure from contaminants at the
OU.
Noncarcinogenic health risks are evaluated using a hazard index (HI). If the hazard index is less
than or equal to one, the contaminant concentration is considered an acceptable level and
generally assumes that the human population may be exposed to it during a 30-year period
without adverse health effects.
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Risk Assessment Results
The risk assessment for OU-4 indicated that the chemical which contributed the majority of the
risk in the soil was.benzo(a)pyrene [a polynuclear aromatic hydrocarbon (PAH)]. However, only
three of five samples had reported benzo(a)pyrene concentrations in excess of the reasonable
maximum exposure (RME) 10"* risk range. None of the sample concentrations exceeded the
central tendency/average risk range. However, due to the heterogeneity of the landfill contents,
uncertainty is associated with the calculated risk values for the surface soil.
The following compounds were identified in the risk assessment as contributing to unacceptable
risk (risk drivers) in ground water on-Base: vinyl chloride, 1,1-DCE, TCE, n-nitroso-di-n-
propylamine, bis(2-chloroethyl)ether, 1,4-dichlorobenzene, aldrin, alpha-BHC, and heptachlor. In
addition, 1,2,4-trichlorobenzene, cadmium, and lead were reported above the MCL in on-Base
ground-water samples. Total-1,2-DCE was reported above the MCL for cis-l,2-DCE in on-Base
ground-water samples.
Vinyl chloride, 1,1-DCE, TCE, 1,2-DCA, and alpha-BHC were identified as risk drivers in
off-Base ground water. In addition, lead and total-1,2-DCE were reported above the MCL in
off-Base ground-water samples.
Risk Assessment Conclusions
Remediation of the ground water is warranted based on the risk to human health from ingesting
and contacting contaminated ground water. Remedial action is warranted for the landfill based on
potential risk to human health from future releases of hazardous substances. Contaminants in the
landfill may leach downward to contaminate the underlying ground water. Off-Base residents
may then ingest or come in contact with the contaminated ground water. Also, the surface of the
landfill may erode, thus exposing off-Base residents to contaminants in both surface water and air.
Due to the potential heterogeneity of the waste materials present within the landfills, a complete
characterization of waste materials present was not possible during the RI. This adds a degree of
uncertainty to the risk assessment for the landfill contents. Rather than attempting to fully
characterize landfill contents and gain more certainty in the risk assessment, the Air Force utilized
guidance developed by EPA titled Presumptive Remedy for CERCLA Municipal Landfill Sites
(OSWER Directive 9355.0-49FS). The presumptive remedy for landfills is containment (capping)
of landfill contents. Using the presumptive remedy strategy, a quantitative risk assessment is not
necessary to evaluate whether the containment remedy addresses all exposure pathways and
contaminants potentially associated with a landfill. Rather, all potential exposure pathways can be
identified using the conceptual site model and compared to the pathways addressed by the
presumptive remedy. Containment of the landfill contents addresses exposure pathways and risks
normally associated with landfills. The contaminant exposure pathways for the potential risks
associated with the landfill contents at OU-4 include (1) direct physical contact with the landfill
contents and (2) consumption or contact with ground water that may become contaminated.
Actual or threatened releases of hazardous substances from OU-4, if not addressed by
implementing the response action selected in this Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare, and the environment.
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Ecological Risks
An ecological risk evaluation of OU-4 was based on a combination of data and literature reviews,
field and laboratory analyses, analyte evaluation and screening, and preliminary risk screening.
The pertinent findings are summarized below.
A variety of animal species may live, forage, or nest in OU-4 habitats. These species include
various types of invertebrates, amphibians, birds, and mammals. Terrestrial vegetation and soil
faunal communities do not reveal characteristics that indicate chemical-related impacts. This
finding is consistent with the relatively low levels of contaminants in the soil.
Because of the altered natural environment at OU-4, rare, threatened, or endangered species are
unlikely to utilize the area for more than brief, periodic habitat. Due to the low levels of
contaminant concentrations, the contaminants do not pose an unacceptable risk to these species.
In addition, the limited contact these species would have with the OU-4 area ensures unacceptable
risk to a single individual is not likely to occur.
Findings of the RI indicate that the contaminants at OU-4 are not altering the ecology to
unacceptable levels. A Base-wide ecological risk assessment will be conducted as part of OU-11,
and OU-4 will be included in this Base-wide evaluation.
2.7 DESCRIPTION OF ALTERNATIVES
Presumptive Remedy for CERCLA Municipal Landfill Sites, (OSWER Directive 9355.3-1 IPS)
was the basis for the abbreviated feasibility study (FS). The OSWER directive established
containment of the contamination within the landfill as the presumptive remedy for municipal
landfills.
Although not specifically identified as a municipal landfill, OU-4 exhibits characteristics that make
this presumptive remedy applicable. The alternatives are briefly described below. A more
detailed description is provided in the FS report.
• Alternative 1 (Landfill)
• No Action
• • The no action alternative represents the baseline condition at OU-4 and refers to taking
no further action at Landfill No. 3.
• Alternative 2 (Landfill) - Institutional Controls
• Institutional controls (access restrictions and deed restrictions).
• Monitoring of ground water.
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• Repair of existing cover in the southwest corner, as necessary.
• Long-term maintenance of existing soil cover.
• Alternative 3 (Landfill) - Capping
• Monitoring and institutional controls as stated in Alternative 2.
• Place soil cover capable of sustaining vegetation on the area of attainment at the landfill.
• Monitor for landfill gas around the landfill perimeter and install a with passive gas
venting layer as part of the soil cover, as necessary.
• Long-term maintenance of soil cover.
• Alternative 4 (Ground Water) - No Further Action
• No Further Action
• The no further action alternative represents the baseline condition at OU-4 and refers to
taking no further action for the ground water at OU-4.
• Alternative 5 (Ground Water) - Ground-Water Recovery Trench/IRA Treatment
Plant/Discharge
• Install ground-water recovery trenches along the southern Base boundary, and in the off-
Base plume.
• Treat extracted ground water at the ERA treatment plant.
• Discharge of treated ground water to a surface water drainage channel.
• Underground injection of ground water is retained as a contingency discharge option.
• Alternative 5A (Ground Water) - Slurry Wall/Ground-Water Recovery Trench/ERA
Treatment Plant/Discharge
• Ground-water recovery trench and treatment components as stated in Alternative 5.
• Installation of a slurry wall upgradient and sidegradient of the landfill
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• Alternative 6 (Ground Water) - Extraction Wells/IRA Treatment Plant/Discharge
• Install ground-water extraction wells along the southern Base boundary, and in the off-
Base plume.
• Treat extracted ground water at the existing ERA treatment plant.
• Discharge of treated ground water to a surface water drainage channel.
• Underground injection of treated ground water is retained as a contingency discharge
option.
• Alternative 6A (Ground Water) - Slurry Wall/Extraction Wells/IRA Treatment
Plant/Discharge
• Extraction well and treatment components as stated in Alternative 6.
• Installation of a slurry wall upgradient and sidegradient of the landfill.
2.8 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The analysis of alternatives coupled with the use of the presumptive remedy combine for a
narrower range of feasible approaches to address landfill remedial activities at OU-4.
The remedial action objectives for OU-4 are as follows:
Landfill
• Prevent dermal contact and ingestion of surface soils within OU-4.
• Reduce the mobility of potential contaminants in the landfill.
Ground Water
• Prevent inhalation, dermal contact, and ingestion of ground water containing
contaminants at concentrations exceeding the remediation goals.
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-4 make it
feasible to divide the OU into separate areas for purposes of evaluating attainment status and
determining appropriate response actions. OU-4 has been divided into four distinct areas for
these purposes: 1) Landfill No. 3; 2) construction disposal area; 3) on-Base ground water; and
4) off-Base ground water.
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Landfill No. 3
The area of attainment for this remedial action is the extent of Landfill No. 3 which is
approximately 35-40 acres in size (Figure 2-3).
Construction Disposal Area
The area of attainment for ground water from the construction disposal area is at the western
Base boundary.
On-Site Ground Water
Because the landfill waste will be managed in place, ground water beneath the landfill is not within
an area of attainment. The area of attainment for on-Base ground water will be landfill
boundaries (Figure 2-4).
Off-Site Ground Water
The area of attainment for off-Base ground water is defined by those areas with contaminants
above remediation goals (MCLs, or risk-based State Ground Water Quality Standards). This area
approximately corresponds to the area identified by the TCE plume (Figure 2-4).
Pursuant to Section 40 CFR 300.430(e)(9)(iii), the remedial action to be implemented should be
selected based upon consideration of nine evaluation criteria. These criteria are as follows:
1. Overall protection of human health and environment.
2. Compliance with applicable or relevant and appropriate requirements (ARARs).
3. Long-term effectiveness and permanence.
4. Reduction of toxicity, mobility, or volume of contamination.
5. Short-term effectiveness.
6. Implementability.
7. Cost.
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.
»
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.
Alternatives 1 and 4 (no further action) do nothing to reduce risk at OU-4. Alternative 2
(Institutional Controls) provides for care of the OU through maintenance of erosional and/or non-
vegetated areas. Access restrictions would reduce risk by reducing exposure associated with the
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landfill. Alternative 3 (Capping) provides containment (cover) of the surface soil and the landfill
contents. This would minimize risk associated with exposure to soil and the future risk associated
with potentially contaminated ground water. Alternatives 5, 5A, 6, and 6A would remediate
ground water to MCLs, thus reducing risk by reducing concentrations of contaminants in the
ground water.
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 of South
Dakota laws that specifically address a hazardous substance, pollutant, contaminant, remedial
action, location or other circumstances at a CERCLA site.
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 to this remedial action is provided in
Table 2-1 at the end of Section 2.0 and a narrative discussion of compliance with ARARs is
provided below for the alternatives considered.
Alternatives 1 and 4 (No Further Action):
The No Further Action alternative does not comply with State solid waste landfill closure
requirements, State criteria for petroleum contaminated soil (ARSD Chapter 74:03:32), or
ground-water ARARs. No Federal or State permits are required for this alternative. Alternatives
1 and 4 do not meet the remedial action objectives for OU-4. No action would not be taken to
prevent human contact with contaminants in the surface soils and ground water. Contaminants
within the landfill would continue to leach to the ground water.
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Alternative 2 (Institutional Controls):
Alternative 2 does not meet all the State of South Dakota solid waste landfill closure
requirements, State, criteria for petroleum contaminated soil, or ground-water ARARs. No
Federal or State permits are required for this alternative. Alternative 2 does not meet the remedial
action objectives for OU-4.
Alternative 3 (Capping):
Alternative 3 will meet or exceed State of South Dakota Waste Management Regulations for the
disposal of solid waste (ARSD Article 74:27) by providing containment of landfill contents,
access/development restrictions, and long-term monitoring. Information from the remedial
investigation indicates that approximately one to two feet of cover material exists over most of
the landfill. The exact cover thicknesses throughout the entire landfill are unknown. ,The State
requires a minimum of two feet of cover material. Additional cover material (a minimum of one
foot in depth) will be added under this alternative to achieve compliance with the State
requirements. The exact cover design will be determined during the remedial design phase. The
State is Federally authorized for the Resource Conservation and Recovery Act (RCRA) Subtitle
D Municipal Solid Waste Program (8 October 1993, 58 FR 52486). State of South Dakota
remediation criteria for petroleum contaminated soil is not applicable within the landfill
boundaries. However, the intent of the regulations (to minimize leaching of contaminants to
ground water) would be met by containment of landfill contents. The resulting cover will also
assist in compliance with the Safe Drinking Water Act Maximum Contaminant Levels (MCLs) by
minimizing the downward transport of contaminants to the ground water.
Alternatives 5, 5 A, 6 and 6A (Ground-Water Pump and Treat):
Alternatives 5, 5 A, 6 and 6 A would achieve containment of on-Base ground water at the landfill
boundary, in accordance with the Presumptive Remedy Guidance. Removed ground water would
be treated to achieve MCLs. Sufficient ground water would be removed and treated so that
MCLs would be met at the Base boundary. Off-Base contaminated ground water would be
removed and treated to achieve MCLs, with the ultimate requirement of restoration of off-Base
ground water to MCLs.
2.8.3 Long-Term Effectiveness and Permanence
The assessment of this criterion considered the long-term effectiveness of alternatives in
maintaining protection of human health and the environment after response action objectives have
been met.
+
Alternatives 1 and 4 would not provide additional effectiveness or permanence in reducing the
potential for direct contact or ingestion of the surface soil or sediments. No further controls for
the OU would be developed under this alternative.
Alternative 2 would provide for increased effectiveness of access restrictions (in addition to the
general EAFB access restrictions). Additionally, vegetation maintenance would reduce erosion
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potential. Permanency and reliability of these controls would be enhanced through long-term
monitoring and maintenance of the OU. Uncertainties exist for the ability to provide long-term
access restrictions.
Alternative 3 would offer the highest level of long-term effectiveness. Reduction of risk would be
accorded by the soil cap. Erosion would be limited by the development and maintenance of a
vegetated area. Upon completion, long-term maintenance of the cover and monitoring of ground
water would be provided. Future land uses will be allowed for the landfill only if the integrity of
the landfill cover is not compromised.
Alternatives 5, 5A, 6 and 6A would offer a high level of long-term effectiveness for ground water.
Reduction of risk would be accorded by a reduction in the concentration of chemicals in the
ground water. Remediation of the existing contaminated ground water in conjunction with a
landfill cover would prevent the movement of contaminants from beyond landfill boundary.
2.8.4 Reduction of Toxicity, Mobility, and Volume Through Treatment
The assessment of this criterion involves considering the anticipated performance of specific
treatment technologies an alternative may employ.
Alternative 1 would not provide for the reduction of toxicity, mobility, or volume of the chemicals
of concern in the surface soil and sediment. Alternative 2 would reduce the mobility of
contaminants in surface soils through long-term maintenance of existing cover soils. Alternative 3
does not use treatment technologies, but reduces the mobility of the contaminants in surface soils
in the landfill area through containment. Alternatives 5 and 6 reduce the toxicity and mobility of
ground water through extraction and treatment. Alternatives 5A and 6A reduce the toxicity,
mobility, and volume of ground water to be treated.
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.
It is not anticipated that the proposed alternatives would significantly impact worker or
community health and safety during the implementation period. Alternatives 2 and 3 may impact
community and worker health and safety through dust emissions during the initial construction
phase. The impact could be minimized through dust mitigation. Alternatives 5, 5A, 6 and 6A
may impact community and worker health and safety through volatile emissions during air stripper
operation. The impact could be minimized by treatment of emissions.
Alternatives 2 and 3 may create a short-term increase in risk during remedial activities due to the
inhalation exposure pathway. Disturbance of surface soil through earthwork would result in
exposure to workers. Dust mitigation during these activities would minimize this potential
impact. Alternative 3 would present the potential for temporarily increasing the opportunity for
erosion of the disturbed soils, although erosion and sediment control measures will help to
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minimize this adverse impact.
Alternatives 5, 5 A, 6, and 6A may create a short-term increase in risk during remedial activities
due to the inhalation of volatile compounds emitted by the air stripper. Air monitoring and
emission treatment, if necessary, during this activity would minimize the potential impact.
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.
Alternative 1 would not be difficult to implement since no further action would be undertaken.
Alternative 2 requires no special or unique activities and could be implemented using locally
available materials and contractors. Long-term monitoring would indicate whether additional
action would need to be implemented in the future.
Alternative 3 could be implemented with standard construction equipment, materials, and
methods. The availability of an on- or off-Base supply of cover material will require further
consideration during the Remedial Design Analysis. Land use (or deed) restrictions can be
implemented at EAFB by various administrative means.
Alternatives 5, 5 A, 6, and 6A require no special or unique activities and could be implemented
with widely available equipment, materials, and methods. The existing IRA treatment plant would
be utilized to treat ground water.
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. 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. A summary of the costs for each alternative is
as follows:
Alternative No. 1 (No Action)
Total Capital Costs
Total Annual (Sampling/Analysis) Costs
$0
$0
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Alternative No. 1 (No Action)
30-Year Present Value for Annual Costs
Annual Cost = $0
Years = 30
Discount Rate = 5%
TOTAL 30-Year Present Value
$0
SO
Alternative No. 2 (Institutional Controls)
Total Capital Costs
Total Annual (Sampling/ Analysis/O&M) Costs
30-Year Present Value for Annual Costs
Annual Cost = $76,000
Years = 30
Discount Rate = 5%
TOTAL 30-Year Present Value
$293,000
$76,000
$1,169,000
$1,462,000
Alternative No. 3 (Capping)
Total Capital Costs
Total Annual (Sampling/ Analysis/O&M) Costs
30-Year Present Value for Annual Costs
Annual Cost = $80,300
Years = 30
Discount Rate = 5%
TOTAL 30-Year Present Value
Alternative No. 5 (Extraction Trench and Treatment)
Total Capital Costs
Total Annual (Sampling/Analysis/O&M) Costs
30-Year Present Value for Annual Costs
Annual Cost = $76,600
Years = 30
- Discount Rate = 5%
TOTAL 30-Year Present Value
Alternative No. 5 A (Extraction Trench, Treatment, and Slurry Wall)
Total Capital Costs
Total Annual (Sampling/Analysis/O&M) Costs
30- Year Present Value for Annual Costs
$3,004,560
$80,300
$1,235,000
$4,239,500
1,398,000
76,600
1,178,000
2,576,000
2,289,000
76,600
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Annual Cost = $ 76,600
Years = 30
Discount Rate = 5% -
TOTAL 30-Year Present Value
Alternative No. 6 (Extraction Wells, Treatment)
Total Capital Costs
Total Annual (Sampling/ Analysis/O&M) Costs
30-Year Present Value for Annual Costs
Annual Cost = $ 82,000
Years = 30
Discount Rate = 5%
TOTAL 30-Year Present Value
Alternative No. 6A (Extraction Wells, Treatment, and Slurry Wall)
Total Capital Costs
Total Annual (Sampling/ Analysis/O&M) Costs
30-Year Present Value for Annual Costs
Annual Cost = $ 82,000
Years = 30
Discount Rate = 5%
TOTAL 30 Year Present Value
1,178,000
3,467,000
1,490,000
82,000
1,261,000
2,751,000
2,381,000
82,000
1,261,000
3,642,000
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. The questions and concerns of the community are discussed in detail in the
Responsiveness Summary, which is Appendix B of the ROD.
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2.9 SELECTED ALTERNATIVE
Based on the requirements of CERCLA, comparative analysis of the nine criteria, public
comments, and in consultation with EPA and the State, the Air Force has determined that the
selected alternative is Alternative 3, Landfill Cover; and Alternative 5, extraction trenches and
treatment for ground water. This alternative includes institutional controls in conjunction with
physical modification of the OU, 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-4 above health-based levels following completion of the installation of the landfill cover and
ground-water extraction system.
Major components of Alternative 3 are:
• Installing an earthen cover over the area of attainment (approximately 35-40 acres).
• Institutional controls to prevent future use of the area for residential use and/or limiting
its use to industrial uses.
• Providing for long-term ground-water monitoring at the OU to identify development of
future risks associated with the OU. Providing long-term maintenance of the remedial
actions taken at the OU.
Installation of Soil Cover
A pre-design study would be conducted to verify the defined limits of the landfill and determine
the type of cover needed. The cover material must be capable of sustaining vegetation. The pre-
design study would also be used to determine the type of cover needed to reduce infiltration of
precipitation through the landfill and ensure continued compliance with the MCLs.
Based on the results of the pre-design study, either a single-layer earth cover or multi-layer
reduced-permeability earth cover would be constructed. The selected cover would be constructed
to comply with State requirements. The area of attainment would be filled, graded, and
contoured to maintain stability, eliminate slumping, settling, or ponding of water above previously
active disposal areas, and to provide positive drainage off the landfill area. The area would also
be vegetated to provide and maintain suitable vegetation to enhance evapotranspiration and
reduce infiltration and soil erosion.
Institutional Controls
Institutional controls would be implemented to prevent human exposure to contaminated soil and
ground water. These controls will include: (1) issuing a continuing order to restrict on-site
worker access to the landfill and to restrict or control temporary construction activities unless
proper protective equipment is worn; (2) filing a notice with the State to recommend denial of
water appropriation permit applications to install ground-water wells within the landfill boundary
and any area which may be effected by potential contaminants; (3) filing a notice to the deed
detailing the restrictions of the continuing order and ground-water well restrictions; and (4) a
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covenant to the deed in the event of property transfer.
A continuing order would be issued by the Installation Commander to restrict access to or
disturbance of the landfill as long as Ellsworth AFB owns the property. Specifically, it would:
Restrict or place limitations on the installation of any new underground utilities or other
construction activities in the area of the landfill; thus preventing accidental exposures to
construction workers.
Provide for the use of proper protective equipment, in the event that access through the
landfill cover is required.
Require that the integrity of the landfill cover be maintained. Maintenance of the landfill
will require development of standard operating procedures (SOPs) to provide for
inspections and repairs.
The continuing order also would mandate that, if the landfill cover was ever removed or
destroyed, the area of attainment would be re-evaluated to determine the need for a replacement
cap or other remedial action.
Continuing order requirements will be in effect as long as the property is owned by Ellsworth
AFB. In the case of the sale or transfer of property within OU-4 by the United States to any other
person or entity, the Air Force will place covenants in the deed which will restrict access and
prohibit disturbance of contaminated soils or the remedial action without approval of the United
States. These covenants will be in effect until removed upon agreement of the State of South
Dakota, the U.S. Environmental Protection Agency, and the U.S. Air Force or their successors in
interest. The Air Force will also include in the deed the covenants required by section 120(h)(3)
of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA),
which include (1) a warranty that the United States will conduct any remedial action found to be
necessary after the date of the transfer, (2) a right of access in behalf of EPA and the Air Force or
their successors in interest to the property to participate in any response or corrective action that
might be required after the date of transfer. The right of access referenced in the preceding
sentence shall include the State of South Dakota for purposes of conducting or participating in
any response or corrective action that might be required after the date of transfer.
Long-Term Monitoring and Maintenance
A maintenance program would be established to ensure the long-term integrity on the landfill
cover system would be maintained. The maintenance program would include development of
SOPs to provide for inspections, repairs, and general maintenance of the landfill.
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 in the off-Base area of contamination and at the landfill boundary would be monitored to
evaluate the effectiveness of the landfill cover and the ground-water treatment system, and to
determine if ground-water contaminants have been transported beyond the landfill boundary.
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Continued analysis and monitoring of the ground-water remedial action system performance will
be conducted to determine jf 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.
This alternative will meet the remedial action objectives and reduce the potential risk for OU-4 by
preventing future exposure to contaminants in the surface soils and by reducing the mobility of
potential contaminants in the landfill. This will be achieved by the construction of the landfill cap.
The major components of Alternative 5 are:
• Continued operation of the IRA, which consisted of removal and treatment of
contaminated ground water;
• Installation recovery trenches to be added to the existing ERA ground-water
recovery system.
• Treatment of removed ground water at the IRA treatment plant.
• Discharge of treated ground water to a surface water drainage, the Base waste-
water treatment plant, or by underground injection.
Continued Operation of the IRA
The IRA consisted of ground-water wells to remove contaminated ground water near the landfill
boundary and in an area beyond the Base boundary. The IRA also included the construction of a
treatment plant for the treatment of the soil gas and contaminated ground water. The IRA will be
continually operated and the additional ground-water collection trenches (or wells) described
below will be added to the system.
Ground-Water Recovery System
Ground-water collection trenches will be installed at OU-4 to remediate contamination in the
shallow alluvial ground water (Figure 2-4). The number and placement of trenches will be
evaluated during the design. The ERA included the installation of ground water wells to remove
contaminated ground water. An evaluation will be performed to determine the effectiveness of
the "ground-water wells. If the most cost-effective method to remove contaminated ground water
is by ground-water wells, additional wells will be installed in lieu of the proposed collection
trenches.
Treatment and Discharge
Ground water removed by the recovery system will be treated at the treatment plant built for the
IRA. The water effluent from the treatment plant is expected to be discharged into a drainage
which flows into Pond 001. The effluent will be monitored prior to discharge to determine the
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effectiveness of the treatment system. Effluent discharge standards and monitoring will be
determined during the design phase and are subject to State and EPA reviews and approvals.
Underground injection or discharge to the Base waste-water treatment plan may be chosen as the
discharge option based on the allowable discharge standard. The expected surface discharge will
comply with the requirements of the Clean Water Act. Off-gas from the thermal oxidizer will be
monitored to ensure compliance with Federal, State, and local requirements under the provisions
of the Clean Air Act.
This alternative will meet the remedial action objectives and reduce the potential risk for OU-4 by
preventing future exposure to contaminants in the ground water and by reducing the mobility of
potential contaminants in the ground water.
2.10 STATUTORY DETERMINATIONS
The selected remedy meets the statutory requirements of CERCLA as amended by SARA. These
requirements include protection of human health and the environment, compliance with ARARs,
cost effectiveness, 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 these materials
by preventing the movement of materials beyond the boundaries of the landfill and preventing
direct contact with landfill materials. The selected remedy represents the best balance of tradeoffs
among the alternatives considered, with respect to pertinent criteria, given the scope of the action.
The manner in which the selected remedy meets each of these requirements is discussed in the
sections below.
2.10.1 Protection of Human Health and the Environment
The selected remedy addresses health and environmental issues that were identified in the OU-4
RI report. Specifically, the capping alternative:
• Eliminates exposure to landfill contents by installing an earthen cover.
• Reduces the potential infiltration of contaminants to the ground water.
• Prevents unauthorized access to the area by installing a perimeter fence and
restricted access signs.
• Provides for long-term monitoring of ground water to identify potential future
risks associated with OU-4.
The ground-water alternative:
• Eliminates exposure to ground water by receptors of concern.
• Reduces the concentration of VOCs and metals in ground water, thereby reducing
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Final Record of Decision Operable Unit 4
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risk.
• Contains the ground-water plume, thereby eliminating the mobility of chemicals in
the ground water.
2.10.2 Compliance with ARARs
Alternative 3 will meet State landfill closure requirements by providing containment of landfill
contents, access/development restrictions and long-term monitoring. Alternative 5 will meet Safe
Drinking Water Act maximum contaminant levels and State Ground Water Quality Standards.
Additional information about ARAR compliance is contained in Section 2.8.2.
Implementation of the presumptive remedy (containment by cover) strategy for landfills has been
shown by EPA to meet the remedial action objectives by preventing direct contact with landfill
contents and ingestion of surface soils.
2.10.3 Cost Effectiveness
The selected remedy provides overall effectiveness in reducing human health risks relative to its
costs. The presumptive remedy process insures cost effective remedies are chosen. The chosen
landfill cover type ensures containment of the landfill contents. Site specific conditions were used
to determine the type of cover necessary for the landfill. Based on the information provided
during the remedial investigation, a more costly landfill cover would not be cost effective. The
selected ground-water remedy provides the most cost effective alternative for ground-water
remediation.
2.10.4 Utilization of Permanent Solutions and Alternative Treatment Technologies to
the Extent Possible
EPA has established that proper capping has proven effective in containing landfill contents. This
alternative provides long-term prevention of exposure to potential landfill material, prevents
unauthorized access. The ground-water treatment system will provide long-term prevention of
exposure to contaminants in ground water. A long-term ground-water monitoring system will be
implemented to detect potential movement of chemicals from the area of attainment.
A five-year review of the selected remedy will be performed due to the uncertainty of the landfill
contents. 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
Treatment of the landfill contents is not supported based on the findings of the remedial
investigation for OU-4. No identifiable hot spots were reported present and the risks associated
with OU-4 can be addressed by eliminating exposure to the landfill contents by capping.
Treatment of ground water by the IRA treatment plant satisfies the statutory requirement of
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Final Record of Decision Operable Unit 4
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treatment as a principal element.
2.11 DOCUMENTATION OF SIGNIFICANT CHANGES
The Proposed Plan identified Alternative 3, landfill cover, as the preferred alternative. A multi-
layer soil cover was used in the Proposed Plan as the basis for the cost estimate for Alternative 3.
The need for a multi-layer cover, as opposed to a single layer soil cover will be evaluated as part
of the remedial design. Therefore, the cover option in Alternative 3 has been modified to reflect
the cost for a 2 ft soil cover until the results of the remedial design evaluation are available.
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Final Record of Decision Operable Unit 4
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TABLE 2-1 EVALUATION OF FEDERAL AND STATE ARARS THAT APPLY TO OU-4, ELLSWORTH AFB, SOUTH
DAKOTA
Applicable or Relevant and Appropriate Federal Standards, Requirements, Criteria and Limitations
Standard, Requirement, Criteria or
Limitation
Safe Drinking Water Act of 1986
National Primary Drinking Water
Standards
National Secondary Drinking Water
Standards
Maximum Contaminant Level Goals
Clean Water Act of 1 977
Water Quality Criteria
Criteria and Standards for the National
Pollutant Discharge Elimination System
Clean Air Act of 1983
National Primary and Secondary Ambient
Air Quality Standard
National Emission Standards Tor Hazardous
Air Pollutants
Citations
42 USC 300g
40CFRPart I4I.II-.12
40CFRPart 143.03
40 CFR 141. 50 and
Public Law No. 99-330, 100
Stat. 642 (1986)
33 USC 1251-1376
40 CFR Part 13 1.36
40 CFR Part I25.1-.3
40 CFR Part 50.1 -.6, .8, .9,
. 1 1 , . 1 2, and Appendices A,
H.J.K
40 CFR Part 6 1.01
Description
Specifies maximum contaminant levels (MCLs)
of public water systems
Establishes secondary maximum contaminant
levels (SMCLs) for public water systems. These
are federally non-enforceable standards which
regulate contaminants in drinking water that
primarily affect the qualities
Establishes drinking water quality goals set at
levels of unknown or anticipated adverse health
effects, with an adequate margin of safety
Establishes criteria for water quality based on
toxicity to aquatic organisms and human health
Establishes criteria and standards for technology-
based requirements in permits under the Clean
Water Act
Establishes standard for ambient air quality to
protect public health and welfare.
Establishes regulatory standard for specific air
pollutants.
ARARType
Chemical
Chemical
Chemical
Chemical
Chemical
Action
Action
Applicability
)
Relevant and appropriate for federal
Class II aquifers.
Relevant and appropriate.
Relevant and appropriate.
Relevant and appropriate. Aquifer may
be a federal Class II A (discharge to
surface water).
Relevant and appropriate.
Applicable
Applicable. Several alternatives would
require discharge to the air following
treatment.
TABLE 2-1 (continued)
Annl
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Applicable or Relevant and Appropriate State Standards, Requirements, Criteria and Limitations
South Dakota Waste Management
Regulations
South Dakota Waste Management
Regulations
South Dakota Waste Management
Regulations
South Dakota Water Quality Standards
South Dakota Ground Water Standards
South Dakota Surface Water Quality
Standards
South Dakota Remediation Criteria Tor
Petroleum-Contaminated Soils
74:26:03:04
74:27:03:11
74:27:15
74:03:04:02, 10
74:03:15
74:03:02
74:03:32
Establishes requirements Tor disposal of
hazardous wastes in sanitary landfills
Defines requirements for closure of solid waste
disposal facilities
Establishes standards for landfill closure and post-
closure monitoring
Defines use of Box Elder Creek and certain
tributaries
Defines ground-water classifications by beneficial
use and sets chemical standards
Establishes surface water quality standards.
Establishes requirements for the remediation of
soil contaminated with petroleum products.
Action
Action
Action
Action
Chemical
Chemical
Chemical
Relevant and appropriate.
Relevant and appropriate. .
Relevant and appropriate.
r
Relevant and appropriate.
Relevant and appropriate.
Relevant and appropriate.
Relevant and appropriate.
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3.0 LIST OF ACRONYMS AND ABBREVIATIONS
ACC: Air Combat Command
AF: Air Force
AFB: Air Force Base
ARARs: Applicable or Relevant and Appropriate Requirements
CERCLA: Comprehensive Environmental Response, Compensation and Liability Act
COC: Chemicals of Concern
DNAPL: Dense non-aqueous phase liquid
EAFB: Ellsworth Air Force Base
EP: Extraction Procedure, the EPA's standard laboratory procedure for
leachate generation
EPA: Environmental Protection Agency
FFA: Federal Facilities Agreement
FPTA: Fire Protection Training Area
FTA: Fire Training Area
GPR: Ground Penetrating Radar
HQ: Headquarters
IN SITU: In the original place
IRA: Interim Remedial Action
IRIS: Integrated Risk Information System
IRP: Installation Restoration Program
JP-4: Jet Propulsion Fuel Number Four; contains both kerosene and gasoline
fractions.
LNAPL: Light Non-Aqueous Phase Liquid
MCL: Maximum Contaminant Levels
mgd: Million Gallons per Day
ug/1: Micrograms per liter
mg/1: Milligrams per liter
MSL: Mean Sea Level
NAPL: Non Aqueous Phase Liquid
NCP: National Oil and Hazardous Substances Contingency Plan
NEPA: National Environmental Policy Act
NPDES: National Pollutant Discharge Elimination System
NPDWR: National Primary Drinking Water Regulations
NPL: National Priorities List
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Final Record of Decision Operable Unit 4
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OU: Operable Unit
O&G: Symbols for oil and grease
PAH: . Polynuclear Aromatic Hydrocarbon
PCB: Polychlorinated Biphenyl; liquids used as a dielectrics in electrical
equipment
PCE: Perchloroethylene; liquids used in degreasing or paint removal.
pg/g: picograms per gram
PL: Public Law
ppm: Parts per million by weight
RCRA: Resource Conservation and Recovery Act
RI/FS: Remedial Investigation/Feasibility Study
ROD: Record of Decision
SARA: Superfund Amendments and Reauthorization Act
SACM: Superfund Accelerated Cleanup Model
SVOC: Semivolatile Organic Compound
TCA: 1,1,1,-tetrachloroethane
TCE: Trichloroethylene
TCL: Target Compound List
TCLP: Toxicity Characteristic Leaching Procedure
IDS: Total Dissolved Solids
TOC: Total Organic Carbon
TSD: Treatment, storage or disposal sites/methods
USAF: United States Air Force
U.S. EPA: United States Environmental Protection Agency
USDA: United States Department of Agriculture
USFWS: United States Fish and Wildlife Service
USGS: United States Geological Survey
VES: Vertical Electrical Sounding
VOC: Volatile Organic Compound
WQC: Water Quality Criteria
WWTP: Wastewater Treatment Plant
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Final Record of Decision Operable Unit 4
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APPENDIX A
FIGURES
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MMNESOTA
NORTH
.—-
SOUTH DAKOTA
ELLSWORTH AFB
RopUCHy
Scot* In Mlta
APPROXIMATE
3 ELLSWORTH
AIR FORCE BASE
ELLSWORTH AFB
RAPE OIY. SOUTH (MKOTA
AREA LOCATION MAP
ROJECT UCR
DESIGNED BY
DRAWN BY
MRG
CHECKED BY
SCALE
AS SHOWN
DATE
JAN 96
PROJECT NO
60378.93
FIGURE:
2-1
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OU-1
OU-2
OU-3
OU-4
OU-5
OU-6
OU-7
OU-B
OU-9
OU-10
OU-L1
OU-12
0 1200 2400
SCALE IN FEET
LEGEND
OPERABLE UNITS
FIRE PROTECTION TRAINING
AREA (FT-01)
LANDFILLS 1 & 6 (LF-02)
LANDFILL 2 (LF-03)
LANDFILL 3
LANDFILL 4
LANDFILL 5
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)
BASEWIDE GROUND WATER
HARDFILL NO. 1
LF-05
ELLSWORTH
'] AIR FORCE BASE
ELLSWORTH AFB
RAPID Cm. SOUTH DAKOTA
SITE LOCATION MNP
REJECT MGR
DESIGNED BY
DRAWN BY
STAFF
CHECKED BY
SCALE
AS SHOWN
DATE
JAN 96
PROJECT NO
60378.93
FIGURE:
2-2
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-d>- ELECTRIC UTILITY
—®- WATER UTILITY
AREA OF CUT AND FILL
TRENCHES
AREA OF FORMER
ASPHALT PILE
POSSIBLE WASTE
DISPOSAL/CONSTRUCTION
STAGING AREA
SURFACE DRAINAGE
BASE BOUNDARY FENCE
»-— TOPOGRAPHIC ELEVATION
ABOVE MSL
CONTOUR INTERVAL - 10'
OU-4
LOCATION MAP SHOWING
UNDERGROUND UTUJTIES
AND AREAS OF FILL
ELLSWORTH AIR FORCE BASE
MM> OTT. nut won
ELLSWORTH
AIR FORCE BASE
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1993/9' "I SEDIMENT
SAMPLE LOCATION
1991/94 Rl UONITORINC
WELL/SOIL BORING LOCATION
«> 1993/94 Rl FIELD SCREEN/
SOIL BORING LOCATION
,, IRP. PHASE II. STAGE I
2 UONITORINC LOCATION
O DOMESTIC AND LIVESTOCK
WELLS
SURFACE DRAINAGE
BASE BOUNDARY FENCE
'/\ OFF-BASE GROUND WATER
AREA OF ATTAINMENT
cffoum
AMCA Or ATTAMMCNT
OU-4
GROUNO WATER
AREA OF AHAINMENT
AIR FORCE BA
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Final Record of Decision Operable Unit 4
Ellsworth Air Force Base, South Dakota
APPENDIX B
RESPONSIVENESS SUMMARY
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Final Record of Decision Operable Unit 4
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Responsiveness Summary
-Remedial Action at Operable Unit Four
Ellsworth Air Force Base, South Dakota
1. Overview
The United States Air Force (USAF) established a public comment period from September 18 to
October 18, 1995 for interested parties to review and comment on remedial alternatives
considered and described in the Proposed Plan for Operable Unit Four (OU-4). The Proposed
Plan was prepared by the USAF in cooperation with the U.S. Environmental Protection Agency
(USEPA) and the South Dakota Department of Environment and Natural Resources (SDDENR).
The USAF also held a public meeting at 6:30 p.m. on September 26, 1995 in the 28th Bomb Wing
Auditorium at Ellsworth Air Force Base (EAFB) to outline the proposed remedy to reduce risk
and control potential hazards at Operable Units 1, 2, and 4.
Some of the public comments pertained to the selected remedies in the Proposed Plans for all the
operable units. Rather than attempting to separate out the comments which pertained to an
individual operable unit, one Responsiveness Summary was prepared to address all the comments
for all the operable units.
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
The selected alternative for the landfill, soil cover, includes the following major components:
• Institutional controls for the landfill area;
• Placing a soil cover capable of sustaining perennial vegetation over the landfill
area;
•. Landfill gas monitoring and passive collection system, as necessary;
• Long-term monitoring and maintenance.
The selected alternative for the ground water, pump and treat, includes the following major
components:
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• Continued operation of the interim remedial action (IRA) which consists of
removal and treatment of contaminated ground water;
• Installation of recovery trenches and/or additional extraction wells to be added to
the existing IRA ground-water recovery system.
• Treatment of removed ground water at the treatment plant built for the IRA.
• Discharge of treated ground water to a surface water drainage, to the Base
wastewater treatment plant, or by underground injection.
2. Background on Community Involvement
On August 30, 1990 EAFB was listed on the USEPA'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. An 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 currently being carried out.
An update to this plan will be prepared 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 ERP at EAFB was distributed
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to the mailing list addressees in 1992.
• 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.
• Newspaper articles. Articles have been written for the base newspaper regarding
IRP activity.
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 September 26, 1995
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
Review of the written transcript of the public meeting did not indicate community objections to
the proposed remedial action. 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, the remedial action; i.e., what would be done, how it
would be done, and what effects the action might have. In addition, one question addressed
purchase of off-Base property. 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.
Part n - 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 September 26, 1995 public meeting.
Comment 1. Jan Deming
Asked about whether the stream running from the northeast to the southwest in OU-1 was
contaminated, or was transporting contaminants.
Response 1: Evidence of jet fuel and pesticides were found in the sediments. The storm drains
were deferred to OU-11 to allow additional investigation of the ecological
conditions on the Base. The ecological assessment showed that there was no risk
to ecological receptors. The oil/water skimmer in Pond 001 will remove any
contamination floating on the pond surface. The monthly NPDES sampling for a
range of chemicals ensures that no contamination is going off-Base.
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Final Record of Decision Operable Unit 4
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Comment 2. Jan Deming
Asked about whether the remedial alternative for off-Base ground water in the OU-4 area
would include any clean-up of soil in the off-Base area.
Response 2: The remediation in the off-Base area is aimed at ground water. The contamination
was transported off-Base by ground water, and that is what needs to be targeted in
the remedial action.
Comment 3. Willie Kermmoade
Asked if the property off-Base with contaminated wells will be purchased by the Air Force
or condemned.
Response 3: The Air Force has supplied water from the Rapid City Municipal Distribution
system to the off-Base properties that border the contaminant plume.
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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