4 7 ! 0 File: 17G

D.P.

ELLSWORTH AFB

SOUTH DAKOTA

ADMINISTRATIVE RECORD

COVER SHEET

AR File Number q V ]
File:

-- D.P. / _,,_? -/) _,

g

471 I

_ Ellsworth Air Force Base, South Dakota

Final Focused Feasibility Study

_ for Operable Unit 1

- March, 1995

United States Air Force

- Air Combat Command
" " " " " Ellsworth Air Force Base, South Dakota

Final Focused Feasibilit_ Study for Operable Unit 1

TABLE OF CONTENTS 4 7 1 2

"" Chapter P__age

1.0 INTRODUCTION ..................................................... 1-1

1.1 PURPOSE AND ORGANIZATION OF REPORT ............................. 1-1

-- 1.2 BACKGROUND INFORMATION ........................................ 1-2

1.2.1 Facility Description .............................................. 1-2

1.2.2 Previous Investigations ........................................... 1-4

1.2.3 OU-1 Geologyh-Iydrogeology ...................................... 1-6

1.2.4 Nature and Extent of Contamination ............................. 1-7

,_ 1.2.5 Contaminant Fate and Transport .................................... 1-8

1.2.6 Baseline Risk Assessment Summary ................................ 1-10

1.2.7 Ecological Evaluation/Risk Assessment .............................. 1-11

2.0 INTERIM RESPONSE ACTION OBJECTIVES .............................. 2-1

-,- 2.1 REDUCE DEGRADATION OF GROUND WATER ............................ 2-1

2.2 COMPLIANCE WITH APPLICABLE OR RELEVANT AND

-- APPROPRIATE REQUIREMENTS (ARARs) ................................ 2-2

2.3 ENSURE CONSISTENCY WITH THE POSSIBLE FINAL REMEDIES ........... 2-2

3.0 GENERAL INTERIM RESPONSE ACTIONS ............................... 3-1

3.1 DESCRIPTION OF ALTERNATIVES ..................................... 3-1

3.1.1 Alternative I - No Action .......................................... 3-2

3.1.2 Alternative 2 - SVE for Source Soils and Source Removal and

Downgradient Containment for Ground Water ......................... 3-2

4.0 EVALUATION OF ALTERNATIVES ..................................... 4-1

4.1 CRITERIA 1 - OVERALL PROTECTION OF HUMAN HEALTH AND THE

_, ENVIRONMENT 4-1

4.2 CRITERIA 2 - COMPLIANCE WITH ARARs ............................... 4-1

4.3 CRITERIA 3: LONG-TERM EFFECTIVENESS AND PERMANENCE ........... 4-3

•- 4.4 CRITERIA 4: REDUCTION OF TOXICITY, MOBILITY, AND VOLUME

THROUGH TREATMENT .............................................. 4-3

w

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Final Focused FeasibiligJ Study for Operable Unit 1

-- 4.5 CRITERIA 5: SHORT-TERM EFFECTIVENESS ............................ 4-4

4.6 CRITERIA6: IMPLEMENTABILITY .................................... 4-4

4.7 CRITERIA 7: COST ................................................... 4-5

"_ 4.8 CRITERIA 8: STATE ACCEPTANCE ..................................... 4-5

4.9 CRITERIA 9: COMMUNITY ACCEPTANCE ............................... 4-5

5.0 REFERENCES ........................................................ 5-1

"_ 6.0 LIST OF ACRONYMS AND ABBREVIATIONS ............................. 6-1

LIST OF TABLES

,_ Table 4-1 Evaluation of Federal and State ARARs That May Apply to OU-1 .......... 4-6

-,-- LIST OF APPENDICES

Appendix A Figures

LIST OF FIGURES

Figure 1-1 Area Location Map

Figure 1-2 Site Map

-- Figure 1-3 OU-1 (FPTA) Site Area

Figure 1-4 OU-1 (FPTA) Location of Geologic Cross-Sections

Figure 1-5 OU-1 (FPTA) N-S Cross-Section A-A'

Figure 1-6 OU-1 (FPTA) E-W Cross-Section B-B'

Figure 1-7 OU-1 (FPTA) W-E Cross-Section C-C'

,-- Figure 1-8 Potentiometric Surface Contours Shallow Aquifer

Figure 1-9 OU-1 Top of Pierre Shale

Figure 1-10 Extent of Reported COC in Soil-Burn Pit Area

_, Figure 1-11 General Area Where Organics Exceed MCLs

Figure 2-1 OU- 1 Site Plan

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Final Focused Feasibility Stuclyfor Operable Unit I

_ 1.0 INTRODUCTION

1.1 PURPOSE AND ORGANIZATION OF REPORT

Operable Unit 1 (OU-1) isthe currentdesignationfor an areacomprised of the fire protection training

area (FPTA) which is a 10-acre area located northwest of the alert apron in the southwest portion

_ of Ellsworth Air Force Base (EAFB).

--- OU-I includes the former burn pit areas and a steel aircraft mock-up which was set on fire and

-- extinguished for training exercises. Fuels used during training exercises included flammable products

from various Base operational areas. Waste materials burned in the FPTA included solvents, oils and

aviation fuels particularly JP-4jet fuel (USAF, 1989).

Volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs) and pesticides are

_ present in soils and ground water at OU-1. Chlorinated solvents and JP-4 jet fuel are present in

ground water beneath and to the south of the burn pit at OU-1. These compounds have been

identified for an interim remedial action (IRA) for control of the potential risks they pose.

A brief summary of background information is provided in Section 1.2 of this document. Further

information is availablein the "Final Remedial Investigation Report, Operable Unit 1 at Ellsworth Air

:-- Force Base, South Dakota", USAF, December, 1994 (OU-1 RI Report).

This Focused Feasibility Study (FFS) summarizes findings of the RI conducted for OU-1. The FFS

-- was completed in response to findings of the OU-1 KI Report submitted December, 1994 to the U.S.

Environmental Protection Agency (USEPA) and the South Dakota Department of Environment and

Natural Resources (SDDENR).

The purpose of the FFS is to develop and examine IRA alternatives to quickly address risks posed

by OU-1 to human health and the environment, as identified in the RI Baseline Risk Assessment and

-- Ecological Evaluation/Risk Assessment for OU-I. An interim remedial action is proposed at OU-1

to initiate remedial action at the site while the full Feasibility Study (FS) process takes place and a

Record of Decision (ROD) is signed for the final action. The IRA does not address all chemicals of

"" concern at OU-1 or all affected media. The full FS process will evaluate a broad range of alternative

actions for OU-1 in it's entirety.

The IRA will reduce immediate risks and control potential hazards at OU-1. Based on the findings

of the Baseline Risk Assessment (BRA) which addresses exposures to contaminants in the soil and

ground water at OU-1, this interim action will decrease the risk by reducing the amount of

contamination in the subsurface soil and ground water. This interim action will be consistent with and

may be incorporated into the final cleanup actions at OU-1.

Remedial action alternatives were developed and screened based on applicable, relevant, or

appropriate federal and state regulations and requirements and on the findings of the RI. The FFS was

--- prepared to analyze and present relevant information concerning potential interim remedial action

alternatives for OU-1. The USEPA Superfund Accelerated Cleanup Model (SACM) approach of

using presumptive remedies was incorporated into this FFS. This approach streamlines the FFS. In

_- accordance with EPA protocols, this document does not recommend an IRA, but rather, provides

I4d.'k55202EPORTSWFSOU Lo, -1.FIN 1-I March 1995
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4 7 [ 5 Final Focused Feasibili_ Stuc_for Operable Unit 1

,i, sufficient information for decision-makers to compare alternatives, and select an appropriate interim

remedy for the site. Interim remedy selection is recommended in the ROD for Interim Action at

OU-1.

This alternative includes treatment of contaminated subsurface source area soils and ground water

by Soil Vapor Extraction (SVE) and ground water extraction wells in the area of historical fire

--- protection training activities. In addition, this alternative would include containment of the

downgradient ground water plume by operation of the existing interceptor trench (USAF, 1991),

located approximately 500 feet south of the fire training area. Vertical SVE wells would be installed

"" in the fire training area and selected SVE wells would be constructed to act as ground water

extraction wells. Extracted soil gas, condensate and ground water will contain both VOCs and

- hydrocarbons and will be treated at a centrally located treatment plant which will also provide

"" treatment for waste streams generated by the OU-4 IRA and the Ottbase JP-4 Plume Early Action.

Water and Condensate treatment will consist of gravity separation, air stripping, filtration and liquid

-- phase granular activated carbon, with monitoring of treated water and effluent discharge

approximately 800 feet upstream to Pond 001.

,,, The objectives for this interim action and the alternatives considered are discussed in Sections 2.0 and

3.0. Section 4.0 presents a comparison of the potential alternatives and evaluation criteria. Section

5.0 is a listing of references of reports on past investigations at OU-1.

1.2 BACKGROUND INFORMATION

!- The information provided in 1.2.1 through 1.2.7 is excerpted and/or summarized from the OU-1 RI

Report (USAF, 1994).

--- 1.2.1 Facility Description

EAFB is aU.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 1-1). EAFB was

officially activated in July, 1942 as the Rapid City Army Air Base, a training facility for the 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 Base has provided support, training, maintenance, and/or testing facilities. Presently,

the 28th Bombardment Wing (B-1B bombers), the 44th Strategic Missile Wing (Minuteman II missile

system), and the 99th Tactics and Training Wing are the host units of EAFB.

The main Air Base covers approximately 4,858 acres within Meade and Pennington counties and

includes runways and airfield operations, industrial areas, and housing and recreational facilities

-- (Figure 1-2). 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.

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Final Focused Feasibility Study for Operable Unit 1

,,, On August 30, 1990 (55 FR 35509), EAFB was listed on the U.S. EPA's National Priorities List

(NPL). A Federal Facility Agreement (FFA) signed in January 1992 went into effect on April 1, 1992.

The FFA identified 11 potential source area Operable Units (OUs) as well as a Base-wide ground

-- water Operable Unit. 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 Low Level Radioactive Waste Burial Site

'" 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 Hard fill No. 1

Listing on the NPL and execution of the FFA required the U.S. Air Force to initiate a remedial

investigation/feasibility study (RI/FS) to investigate these 12 operable units. (USAF, 1994)

OU-1 contains the former FPTA located in the southwestern segment of EAFB, near the southern

perimeter of EAFB northwest of the alert apron and east of Kenney (formerly Bismark) Road

,-" (Figure 1-3). OU-I covers approximately 10 acres and consists of a centrally located shallow, bermed

bum pit and surrounding land. No containment (liner) was installed under the old FPTA. The FPTA

was operated by the EAFB Fire Department at this location from 1942 to 1990.

OU-1 includes the former burn pit areas and a steel aircraft mock-up which was set on fire and

extinguished for training exercises. The location of the bum area within the former FPTA has changed

-- several times over the years. Aerial photographs of EAFB dated May 28, 1952, October 8, 1954,

August 25, 1962 and June 19, 1968 show numerous areas of staining presumed to be a result of fire

training activities within the former FPTA. The extent of the historical burn pit locations based upon

"- aerial photos is illustrated in Figure I-3. The training exercises conducted at the FPTA involved

simulation of aircraft fires and spills,and consisted of dispersing various fuels and solvents within the

,,, bum pit area and subsequently igniting and extinguishing the fire. Fuels used during training exercises

included flammable products from various Base operational areas. Waste materials burned in the

FPTA included solvents, oils and aviation fuels particularly JP-4 (USAF, 1989).

Prior to 1972, training exercises were conducted by pouring fuels directly from 55 gallon drums onto

the soil of the burn pit. The burn pit soil was not pre-wetted, and in the summer, up to two bums

,- (1,000 to 2,000 gallons of liquids each) wereconducted daily. In 1972, a 20,000 gallon above-ground

fuel tank, a 1,000 gallon underground storage tank and underground lines connecting the tanks were

installed and connec ted to the burn pit. These tanks are empty and no longer in use since the new

-- FPTA area was built and are in the process of being abandoned (DeYoe, 1993). Since 1972,

exercises conducted in the FPTA area consisted of 200 to 300 gallon burns (approximately 10,000

to 15,000 gallons annually). The fuel used in these exercises prior to 1984 consisted primarily of

", waste JP-4 but also included waste oil and solvents. Clean JP-4 fuel was reportedly used between

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Final Focused Feasibility Stud_ for Operable Unit 1

w 1984 and 1990. the practice of pre-wetting bum pit soil with water prior to fuel application was

implemented in the late 1980s. Extinguishing chemicals used during the fire training exercises have

included aqueous film forming foam, ha/on, protein-foams, carbon dioxide, dry chemicals and

v chlorobromomethane (USAF, 1989). The former FPTA at OU-I is no longer in use and all training

activity now takes place at the new FPTA.

" The new FPTA was built 600 feet to the north-northeast of the former FPTA in 1992 and started

operation in 1993. The burn pit of the new FPTA is an approximately 100 foot diameter circular

concrete-lined depression. Water and waste products associated with training activities flow through

a collection system and are piped to a nearby oil/water separator. A 60 foot wide reinforced concrete

apron surrounds the perimeter of the new bum pit.

1.2.2 Previous Investigations

,_ Environmental investigation activities at EAFB were initiated by the Air Force in 1985 through the

preparation of an Installation Restoration Program (IRP) Phase I Installation Assessment/Records

Search. The IRP was a four-phased study program which included; Phase I, Installation

v Assessment/Records Search; Phase II, Confirmation/Quantification; Phase HI, Technology Base

Development; and Phase IV, Operations/Remedial Actions.

-," The Phase I study, dated September, 1985, identified a total of 17 locations at EAFB where releases

involving hazardous substances potentially occurred. There was no sample collection or arialysis

associated with the Phase I IRP study (USAF, 1985).

As recommended in the Phase I IRP, a two-stage, Phase II IRP investigation was conducted between

1987 and 1989. Stage 1 of the Phase II IRP study was conducted in 1987 and 1988 (USAF, 1988).

"- Activities in this phase of the investigation included soil vapor surveys, geophysical and radiation

surveys, soil borings, monitoring well installation, and subsurface soil, ground water, sediment,

surface soil, and tank sampling and analysis.

In Phase H, Stage 2 of the IRP investigation, field activities included soil vapor surveys, geophysical

v surveys, soil borings, monitoring well installation, hydrogeologic testing, and subsurface soil, ground

water, sediment, surface soil, and storm drain sample collection and analysis (USAF, 1989).

,,, Two soil vapor surveys were conducted at OU-1 as part of the Phase II IRP Study. The first

consisted of 41 grid points, and was conducted in November, 1987. In general, samples were

- collected at depths of 1.5 and 4.0 feet Subsequently, a 32 point grid was established and additional

soil vapor sampling was conducted in April, 1989. The depth of sample collection for these 32

samples ranged from 5 to 12 feet The results of these two separate soil vapor surveys indicated:

-- • Organic vapor readings were reported in soil vapor samples northeast, south, and southeast

(within 100 feet) of the bermed burn pit. Movement of fuels through gravel related to surface

spills and training-related events appears to be the cause of the elevated vapor readings. The

-- direction of near surface/overland flow of product was concluded to be generally toward the

south and southeast following the surface grade.

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• Final FoeusedFeasibili_ Studyfor Operable Unit I

,., • A trend of decreasing concentration with depth was observed at all sampling locations where

multiple depth readings were obtained. According to the IRP report, this trend was the result

of fuel product vapor residue in the near surface.

Atotal of 22 borings were drilled during the Phase I, Stage 1 and 2 field programs. Six borings were

drilled during Phase II, Stage 1. Three soil samples were collected from each of the six Phase II

Stage 1 borings for laboratory analysis. The resulting 18 soil samples were collected from evenly

spaced intervals from grade to boring termination and were analyzed for VOCs, SVOCs, oil and

grease (O&G), extraction procedure (EP) toxicity metals, and EP toxicity pesticides. Sixteen

v additional borings were drilled during Phase II, Stage 2, and 10 of these were logged, lithologically

classified and one sample from each boring was collected for VOC and total recoverable petroleum

hydrocarbons (TRPH) analysis. The remaining six borings were drilled to install piezometers. These

borings were not sampled.

-- Soil borings drilled in the area during the IRP investigation indicate that the site is underlain by a silty

clay layer, up to 15 feet thick, with some discontinuous lenses of sand and gravel. The clay layer in

turn was found to be underlain by a sand and gravel layer ranging from 2 to 15 feet in thickness, and

v- inter-fingered with discontinuous clay lenses. The sand and gravel layer which was considered to be

fluvial in origin was not encountered in all borings and appears to pinch out to the west and south of

the training area. In particular, a 4 feet silty gravel lens was encountered during the Phase II, Stage

.-- 2 borings beneath the bum pit. Fill materials consisting of loose gravel and hard clay was encountered

in the southern portion of the site ranging from 2 to 10.5 feet in thickness.

-- The fill and alluvial deposits were determined during the IRP investigation to overlie gray to black

weathered shale of the Pierre Shale Formation. The weathered shale interval ranges in thickness from

13 to 20 feet and overlies unweathered shale. Based on IRP Phase II study borings, the Pierre Shale

"- surface appears to be sloping, generally to the south and southeast.

Organic compounds commonly associated with jet fuels (toluene, ethylbenzene, and total xylenes)

-- were generally reported in soil samples from borings surrounding, and south of, the burn pit.

Chlorinated solvents, including trichloroethene (TCE) and tetrachloroethene (PCE) were reported

in samples within and south of the burn area. Light non-aqueous phase liquid (LNAPL) was noted

"_" in one of the monitoring wells during the Phase II, Stage 1 investigation.

-- TRPH was reported in ten often Phase II, Stage 2 soil samples; reported values ranged from 97 to

2,600 mg/kg. The highest TRPH concentrations were reported in the samples collected downgradient

and south of the burn pit. The Phase II, Stage 1 soil samples were not analyzed for TRPH.

O&G was reported in eighteen of eighteen Phase II, Stage 2 soil samples. The reported values

ranged fi'om 180 to 3,200 mg/kg In general, samples obtained from borings located adjacent to the

_, bum pit had the highest reported values. The O&G reported values were also higher in the samples

obtained from downgradient (south of the burn pit) borings• The reported concentrations also

generally decreased with depth. Phase II, Stage 2 soil samples were not analyzed for O&G.

Naphthalene and 2-methylnaphthalene were the two primary analytes reported from Phase II, Stage 1

soil samples• Acenaphthene, fluorene, and phenanthrene were also reported.

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Final Focused Feasibilit), Stud,vfor Operable Unit 1

,, A total of seven monitoring wells were installed during the IRP Phase II investigation at the area.

Two wells were installed and sampled during Phase II, Stage 1. These samples were analyzed for

VOCs, SVOCs, O&G, and priority pollutant metals. An additional five monitoring wells were

-- installed during Phase II, Stage 2 (April-May, 1989). During Phase II, Stage 2, ground water samples

were collected from all seven monitoring wells and analyzed for VOCs and TRPH.

Based on IRP data, it appears that relatively higher levels of organic constituents occur in ground

water samples primarily between the burn pit area and Pond 001 located south of the burn pit.

Chlorinated solvents and benzene, toluene, ethylbenzene, toluene (BTEX) compounds were reported

v in samples from the Phase II, Stage 2 sampling event. LNAPL was noted in one of the monitoring

wells during Phase II, Stage 2 sample collection.

_' A ground water recovery system and treatment plant was installed, operated, and tested during

September and October 1990 at OU-I as part of the IRP, Phase III Technology Base Development

-- Study at EAFB. The purpose of the test was to determine the feasibility of using a ground water

pump and treat system at OU-1. This pilot system was still in place at the time of the RI field

investigation and consists of an interceptor trench equipped with a pneumatic ejector pump. The

trench is 115 feet long and 75 feet wide at its longest and widest points, and is approximately 22 feet

deep. The treatment system is composed of an oil/water separator, chemical pre-treatment (to

control the deposition and precipitation of iron and other cations in the air stripper), air stripper, bag

_. filtration (to remove solids and precipitated metals), followed by activated carbon filtration.

A Phase III pumping test conducted at the fire protection training area predicted that a yield of 0.437

,,- gallons per minute (gpm) was expected from an interception trench (of the dimensions used in the

pilot study) in the fractured clay at EAFB. The pilot study established that the pilot ground water

treatment system operating at an average flow rate of 745 gallons per day (gpd), successfully

_-- removed target compounds from the ground water (USAF, 1991).

In 1993 and 1994, an extensive Remedial Investigation (RI) field program was conducted to

-- characterize site conditions at OU-1. The program included completion of 51 boreholes, installation

of 11monitoring wells, geotechnical analysis of selected soil samples, ecological investigations, health

risk assesment and review and compilation of previous IRP investigations. Collection and laboratory

_" analysis of soil, ground water, surface water and sediment samples were included in the RI field

program.

The results of the ILl field program are summarized in Sections 1.2.3, 1.2.4, 1.2.5, 1.2.6 and 1.2.7

of this document.

1.2.3 OU-I Geology/Hydrogeology

,t The unconsolidated deposits at OU-1 consist of silty clay (one to 15 feet thick) underlain by

silty/clayey gravel and sand (one to 20 feet thick). The upper Pierre Shale at OU- 1 is very weathered

with few or no fractures to moderately hard with fractures (less than 0.10 to 0.25 inches wide). The

-, thickness of the fractured/weathered shale unit is estimated to be approximately ten to 30 feet thick.

However, it should be noted that because most RI borings did not penetrate into competent shale,

the fractured/weathered shale unit may be thicker. The OU-1 geology is illustrated on Figures 1-4

through 1-9.

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Final Focused Feasibility Studyfor Operable Unit 1

\

"-'k, The depth of ground water at OU-1 ranges from approximately 10 to 20 feet below the ground

'surface. Ground water generally flows toward the south-southeast within the silty clay, sand and

gravel and fractured shale. The average ground water gradient is approximately 0.016 fl/R. The

hydraulic conductivity based on slug test results ranges from 2.8 E-03 to 3.7 E-06 feet/minute (fl/min)

with a median value of 7.0 E-05 tt/min. It is estimated that the saturated thickness ranges from

approximately 15 to 30 feet. Ground water flow velocity was calculated as ranging from 0.64

-- feet/year in the fractured shale to 96 feet/year in the clayey sand and gravel.

1.2.4 Nature and Extent of Contamination

The following text summarizes the nature and extent of petroleum and chlorinated VOC

contamination in OU-1 soil and ground water in the area of and downgradient of the abandoned

"" FPTA:

So// w

Both vadose zone (the unsaturated zone above the water table) and capillary fringe (the saturated

v zone above the water table where water is held against gravitational forces by capillary forces) soil

contain high concentrations of JP-4, BTEX, and chlorinated VOCs. The following general

concentration ranges of these compounds were found in the burn pit portions of the FPTA area soil

v during the RI:

v Contaminant Vadose Zone (_zg/kg) Capillary Fringe (/zg/kg)

JP-4 100,000s to 1,000,000s 1001000s to 1,000,000s

Total BTEX ND to 100,000s 1,000s to 10,000s

_ Total chlorinated VOCs ND to 10s ND to 100s

IP-4 concentrations are much higher than other compounds According to the RI, the distribution

v of JP-4 generally reflects the extent of organic compounds in soil. The extent of chemicals of concern

(COC) in soil is shown on Figure 1-10.

The RI indicated that light non-aqueous-phase liquids (LNAPLs) (JP-4 and the related BTEX

compounds) were found in soil at the south end of the FPTA.

Ground water

..., The RI reported that TCE, benzene, PCE, 1,1-dichloroethyelene (1,1-DCE) and 1,2-dichloroethane

(1,2-DCA) were reported at or above their established Safe Drinking Water Act Maximum

Contaminant Level (MCL) in one or more ground water samples at OU-1. The RI also indicated that

-- the 10 lzg/l contour for benzene represents the extent of organic compounds exceeding their MCLs.

The extent of COCs in ground water at OU-1 is shown on Figure I-11.

W

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4 7 _ I _ FinalFocusedFeasibilityStudyforOperable Unit 1

,,, The RI indicated that dense non-aqueous-phase liquids (DNAPLs) were not present in OU-1 ground

water. The ILl indicated that LNAPLs (JP-4 and related BTEX compounds) were found in ground

water at the southern end of the FPTA area (wells MW890105 and MW930102 shown on Figure

-- 1-11).

1.2.5 Contaminant Fate and Transport

The fate and transport of contaminants associated with OU-1 is governed by on and off-site transport

of the contaminants in surface and ground water and transport in soil.

- Surface soils at OU-1 consist of naturally occurring clay loam and reworked silty clay. The primary

physical routes of movement for contaminants associated with surface soils are transport of dissolved

"" and particulate matter by surface water runoff and through infiltration to ground water. Another

potential physical route of transport of chemicals associated with surface soil is by wind-blown

deposition.

Surface water drainage adjacent to OU-1 originates primarily upgradient of OU-1 as storm water

... runoff Runoff and ground water discharge originating within OU-1 contribute a small percentage

of the total surface flow in the adjoining drainages. Surface water from OU-1 flows into Pond 001

and eventually leaves the Base to the south. Surface water may contribute some recharge to the

-- ground water during seasonally dry periods.

Sediment in the drainages also originates primarily upgradient of the OU and is carried into and

--- through OU-I with storm water from the west and north. Some sediment may originate from within

OU-1 due to bank, channel or surface erosion. Soil particles found in the sediment naturally contain

minor amounts ofhumic material/plant detritus and heavier trace metals. The sediment in the streams

•-- at OU-I will generally move with the surface water flow and move downstream where settlement in

low flow areas, especially Pond 001, will occur. Clay and other fine grain materials are more easily

suspended, or re-suspended, in water and can be transported past Pond 001 and continue to move

-- downstream. Silt and larger particles will tend to reside on the pond bottom and transport of these

particles past the pond will only occur as a result of physical disturbances, such as dredging.

• " The shallow ground water aquifer has the highest potential to be impacted by former activities at

OU-1. Thick sequences of Upper Cretaceous confining beds separate the shallow aquifer from deeper

-- ground-water" aquifers and these deeper aquifers are not considered as potential pathways at OU-1.

- Data provided from the field investigation at OU-1 indicate that specific VOCs reported at the site

,,_ are primarily aromatic hydrocarbon compounds of fuel origin (benzene and ethylbenzene); and

chlorinated hydrocarbons (TCE, 1,2-DCE, 1,1-DCE, 1,2-DCA, and vinyl chloride). VOCs are of

particular concern due to their mobility in the environment. VOCs are known to move through the

environment by means of the atmosphere, soil and water. Transport of individual VOCs is affected

by their partition coefficient, sorption potential, aqueous solubility, and high Henry's Law constant.

Volatilization, biodegradation, and sorption are the three potential fate and transport processes which

-- govern the long-term distribution and persistence of VOCs in the environment.

v

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Final Foeused Feasibilig: Study for Operable Unit I

Volatilization is the process by which chemicals are transported from the aqueous and sorbed phases

to the vapor phase. The tendency to volatilize is primarily determined by physical properties

(molecular weight, solubility in water, Henry's Law constant, diffusion coefficient, and vapor

v pressure) specific to a particular compound. In surface water and ground water, the rate of

volatilization is controlled by the nature of the air-water interface (a function of flow velocity, depth,

turbulence, sediment content, and the presence of dissolved organic carbon or other organic

compounds). Resistance to mass transfer is thought to reside in the gas and liquid boundary layers

associated with the gas-liquid interface. Volatilization from the aqueous phase can be defined by the

Henry's Law constant (14)for a particular compound, which describes the partitioning of a chemical

-- between the aqueous and vapor phases at dilute concentrations. The values of H provide some

insight into the controlling rate processes, and compounds with H values greater than 0.001 atmm3/mole volatilize rapidly (Lyman, 1982). The VOCs reported at OU-1 have H values greater than

"" 0.001; consequently, volatilization from the aqueous phase would be a potential environmental

transport pathway.

Volatilization from the LNAPL phase associated with soil is controlled by chemical, soil, and general

environmental properties. Chemical properties affecting volatilization include: vapor pressure,

solubility in water, basic structural type, and number/kind/position of functional groups. Other factors

affecting volatilization rate from soil are: compound concentration in soil, soil-moisture content,

humidity, temperature, sorptive and diffusive characteristics of the soil, soil organic matter content,

,_ soil porosity, soil density, and clay content. Volatilization from the LNAPL phase can be defined by

the vapor pressure for a particular compound. Volatilization for the VOCs reported at OU-1 is

considered an important transport pathway.

Biodegradation is the second potential process VOCs can undergo in the environment. Several

hydrocarbon compounds are readily biodegraded under aerobic conditions. The following example

•_ for benzene is illustrative of the general mechanism (Chiang, et al., 1989):

Benzene: C6H6+ 7.5 O2 _ 6CO2 + 3 H20

In the presence of suitable microbial populations and oxygen, benzene can be degraded to carbon

dioxide and water. A demonstration project at Hill Air Force Base showed that biodegradation can

" contribute significantlyto the dissipation of hydrocarbons in the gasoline range. Laboratory studies,

along with field measurements leads to the general conclusion that the ecological and environmental

significance of anaerobic hydrocarbon degradation is very low compared with aerobic degradation

v (Ward and Brock, 1978; Ward, et al., 1980; Delaune, et al., 1980).

Most volatile aromatic hydrocarbons have a high water solubility and low affinity to sorb to soil.

Therefore, attenuation of, for example, benzene on soil, suspended material, or bottom sediment is

not viewed as a significant fate process. Consequently, VOC are mobile in the environment.

Data provided from the RI field investigation and risk assessment at OU-1 indicate that specific

SVOCs present at unacceptable risk levels are primarily polynuclear aromatic hydrocarbon (PAH)

.,,, type compounds (fluorene, benzo(a) anthracene, benzo(b)fluoroanthene and benzo(a)pyrene in

surface soil and bis 2-ethylhexyl phthalate and chrysene in ground water. Volatilization,

biodegradation, and sorption are the three potential fate and transport processes which govern the

,,, long term distribution and persistence of SVOCs at OU-1.

I,V..'_55202_2EPORT"S_FFSOU-1.FIN 1-9 March 1995
..,, Ellsworth Air Force Base, South Dakota

il 7 I 1 3 Final Focused Feasibility Stu@ for Operable Unit I

,, Based on their relatively small Henry's Law constants, PAIl are not expected to volatilize from

ground water and surface water to a significant extent. Furthermore, based on their low vapor

pressures, PAH are not expected to volatilize from soil. The PAH compounds have a high tendency

v to bind to dissolved organic carbon in the aqueous phase and sorb to soil organic carbon. The primary

environmental fate of PAH at OU-I is sorption to soil. The primary transport pathway for SVOC at

OU-1 is via transport of suspended soil particles in storm water run off.

Pesticide chemicals of concern at OU-I include: dieldrin, endrin, lindane, gamma-chlordane,

alpha-chlordane, heptachlor epoxide, and p,p-DDT in surface soil due to unacceptable ecological risk;

and heptachlor, alpha-BHC, and gamma-BHC in ground water due to unacceptable human health

risk. Volafilization, biodegradation, and sorption are the three potential fate and transport processes

which govern the long-term distribution and persistence of pesticides in the environment. The primary

-- fate of pesticides at OU-I is sorption to soil, however, percolation of lindane to ground water is

considered possible. With the exception oflindane, the reported pesticides in ground-water samples

are considered to be the result of elevated turbidity in the samples. The primary transport pathway

for pesticides at OU-I is to streams through surface water run off.

In general, metals can form both organic or inorganic compounds in soil and sediment. Metals may

sorb to sediment and soil via interaction with organic matter or clay particles to form stable

complexes that are relatively insoluble in water. The fundamental factors that determine an analyte's

_, affinity for either soil or water are the soil-water chemistry and the adsorbent surface charge

deficiency that requires an accumulation of ions near the solid/liquid interface to neutralize the surface

charge. The cation exchange capacity (CEC) is most commonly controlled by the clay fraction of a

soil matrix. The primary environmental fate of metals and inorganic analytes at OU-I is sorption to

soil. The primary transport pathway for metals and inorganics is to the streams through surface water

= run off. Metals and inorganics were reported at elevated levels in ground-water samples indicating

=7 that some percolation to ground water has occurred. The environmental fate ofinorganics in ground

water is transport with the ground water to the south. Because inorganic analytes preferentially

complex with common soil elements, inorganics and metals are not expected to be transported far

-- beyond their source area.

1.2.6 Baseline Risk Assessment Summary

The assessment of human health risks for this site considered the following topics: (1) potential

COCs in ground water, surfacewater, sediment, and soil samples collected at OU-1; (2) current and

"" future land-use conditions; (3) potential environmental pathways by which populations might be

exposed; (4) estimated exposure point concentrations of potential COCs; (5) estimated intake levels

of the potential COCs; (6) toxicity values of the COCs; and (7) uncertainties in the assessments of

exposure, toxicity, and general risks. The levels of potential human health risk associated with OU-I

were then quantified and discussed.

The four potential exposure groups evaluated for OU-1 are: (1) current Base personnel engaged in

site inspection who are exposed to surface soil, surface water and sediment; (2) future adults living

on-site who are exposed to surface soil and ground water; (3) future adolescents living on-site who

are exposed to surface water and sediment through wading activities; and (4) future adult

construction workers who excavate on-site for building residences. Noncarcinogenic and

carcinogenic risks were calculated for these four groups.

W..'I55202_t_ORTSW2n'SOU-1.FIN 1-10 March 1995
_ 7 t 14 ett.,or,ha*rUoB *e re ,So.,hD ko,

Final Focused Feasibility Study for Operable Unit 1

_, The methods used to characterize risks depend on whether a COC is a carcinogen or a

noncarcinogen. For noncarcinogens, the potential effects resulting from exposure to COCs were

estimated by comparing an exposure intake with the established RfD. The resulting ratio, known as

the hazard quotient (HQ), was derived as:

HQ= I_

where:

HQ = Hazard quotient, ratio of average daily dose to acceptable dally intake level (unitless)

Intake = Average daily intake (mg/kg/day)

RfD = Reference dose (mg/kg/day)

Noncarcinogenic risks for the exposure groups are summarized as follows:

Noncarcinogenic risks at OU-1exist for the future residential adult who either ingests shallow ground

water or showers with shallow ground water. Risk is driven by the volatile compound 1,2-DCE.

Carcinogenic risks were estimated as the incremental probability of an individual developing cancer

over a lifetime as a result of exposure to a potential carcinogen. Risks are expressed as probabilities,

e.g., one-in-a-million. This level of risk is also denoted by 10"6or 1 E-06. Risks at or below this level

cannot be differentiated from the background occurrence of cancer in the population. Risks

"" calculated in a risk assessment are potential risks and are excess (i.e., over background) cancer risks

due to exposure from the site.

": Carcinogenic risks for the exposure groups are summarized as follows:

Carcinogenic risks indicate the sources of risks in excess of 1 x 10.6are due primarily to the presence

of several organic compounds (benzene, vinyl chloride, 1,1-DCE, 1,2-DCA, TCE, alpha-BHC,

gamma-BHC, bis 2-ethylhexyl phthalate, chloroform, chrysene) and arsenic in the shallow ground

_ water, and are incurred during ingestion or showering by a future residential adult.

In addition, there is risk greater than 1 x 10.6 associated with the ingestion of the PAH

., benzo(a)pyrene in surface soil (ingested by a future residential adult), and combined risks from dermal

contact with surface soil in excess of 1 x 10"5,attributable to no single compound. Sediment-related

risks greater than I x 106 are due to combined risk from arsenic and beryllium (ingested by a future

,-- residential adolescent), although neither inorganic analyte exceeds 1 x 10_5by itself

1.2.7 Ecological Evaluation/Risk Assessment

The ecological evaluation of OU-I was based on a combination of data and literature reviews, field

and laboratory analyses, analyte evaluation and screening, and preliminary risk screening. The

w pertinent findings are summarized below.

W...155202kREPORTSWFSOU I.FIN- 1-11 March 1995
,.I7t 15

Ellsworth Air Force Base, South Dakota

Final Focused Feasibility Stuclyfor Operable Unit 1

In terms of ecological value, OU-1 presents a highly disturbed environment with dominant features

such as the abandoned bum pit and surrounding gravel patchl Notwithstanding the high level of

disturbance, habitat features such as grass fields, weedy old fields, and wetlands are prevalent in the

eastern and southern sections of the OU. These could be used intermittently by some receptors.

A variety of potential receptors were identified that could forage in OU-I habitats. These range from

--- the benthic invertebrates and amphibians inhabiting the drainage channels to birds and mammals. Any

of these are potential receptors of elevated chemical concentrationS.

-- Rare, threatened, or endangered species are unlikely to use OU-I for more than very transient habitat.

Most of these species would not be expected to occur on OU-I at all because of the high disturbance

level and lack of habitat.

Terrestrial vegetation and soil fauna communities sampled outside the bum pit and surrounding gravel

area do not reveal patterns indicating chemical-related impacts. This finding is consistent with the

_" relatively low levels and limited distribution of elevated concentrations in soil outside the burn pit

area, and with the active and disturbed nature of the site which appears to be the primary control of

biotic community structure.

Surface water does not appear to present sufficient risk to ecological receptors to warrant further

investigation on an OU-specific basis. Therefore, a Tier III assessment for potential OU-specific

chemicals of concern in surface water does not appear to be warranted.

Similarly, sediment does not appear to present sufficient risk to ecological receptors to warrant

further investigation on an OU-specific basis. Therefore, an OU-specific Tier 171assessment for

potential chemicals of concern in sediment does not appear to be warranted.

The pattern of surface soil chemical concentration indicated that the burn pit was the source of

elevated organic chemicals, containing elevated levels of jet fuel, pesticides, PAHs, and volatile

-- organics. Except for jet fuel, elevated concentrations in surface soil was restricted to the burn pit and

surrounding gravel area. An OU-specific assessment of suriicial soil chemicals of concern does not

appear to be warranted.

Potential chemicals of concern could be an important component of an installation-wide ecological

risk assessment. These chemicals of concern would include silver in surface water, cyanide in

sediments, and lead and cyanide in surface soil.

VEq55202_REPORTS_-SOU-1.FIN 1-12 March 1995
Ellsworth Air Force Base, South Dakota

_i i' i _ 6 Final Focused Feasibility Study for Operable Unit I

•.,, 2.0 INTERIM RESPONSE ACTION OBJECTIVES

The IRA objectives at OU- 1 are to control the transport of source area contamination in the area of

-- historical fire pit activities to ground water and to remove and treat contaminated ground water

downgradient of this source area. This action is not the final response action for OU-1; however, it

is expected to reduce organic contaminant concentrations in ground water and to remove VOCs in

"- subsurface vadose and capillary fringe soils and reduce the risks associated with those contaminants.

The IRA being considered includes treatment of contaminated ground water and vadose and capillary

- fringe soils by ground water extraction and soil vapor extraction (SVE) wells, within the same

borehole, in the area of historical fire pit activities and operation of the existing ground water

interceptor trench (USAF, 1991). The locations of the historical fire pit and the existing interceptor

trench are shown in Figure 1-3. A preliminary layout of soil vapor extraction/ground water extraction

wells is shown in Figure 2-1.

Extracted ground water will contain VOCs, SVOCs and petroleum hydrocarbons and will be treated

at a centrally located ground water treatment plant which will also provide treatment for waste

streams generated by the OU-4 IRA and the Offbase JP-4 Plume Early Action. Extracted soil gas

and condensate wilt contain primarily VOCs and low molecular weight petroleum hydrocarbons.

Condensate will be treated by the central ground water treatment plant. Soil gas will be treated by

---, thermal oxidation and emissions will be monitored prior to onsite discharge. Ground water treatment

plant effluent will be monitored prior to discharge approximately 800 feet upstream of Pond 001

(Figure 1-3)

The interim action does not fully address all contaminants in shallow ground water and the risks

associated with those contaminants. The additional contaminants must be addressed by any final

-- action. The interim action also does not address contaminated surface and near surface soils at OU-1.

Remaining contaminated soils must also be addressed by any final action.

-- Because the interim action under consideration is not meant to be the final response for OU-1, only

two alternatives were considered. A more complete listing and review of potential alternatives will

be considered in the full FS for OU-1. The primary objectives of the interim response action are

presented below.

2.1 REDUCE DEGRADATION OF GROUND WATER

The objective of the IRA is to remove VOCs andpetroleum hydrocarbons in subsurface soils (vadose

zone and capillary fringe contaminated soils within the gravel unit are targeted for treatment) and

ground water below the area of historical fire pit activities and to remove and treat contaminated

ground water downgradient of the source area.

I4Zq55202_PORTSh_SOU-1.F1N 2-1 March 1995
- 171 17 Ellsworth Air Force Base, South Dakota

Final Focused Feasibili_/ Stud_ for Operable .Un,!t 1

,,.. 2.2 COMPLIANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE

REQUIREMENTS (ARARs)

Any interim action should comply to the extent practicable, with ARARs in effect when the action

is selected. Where compliance cannot be achieved, the interim action should not prevent compliance

by the final remedy.

2.3 ENSURE CONSISTENCY WITH THE POSSIBLE FINAL REMEDIES

The interim action selected should not preclude the application of any potential final remedy for

OU-1.

W.'_552027_-.PORTSLnI_OU-1.FIN 2-2 March 1995
- 471 18 ll*worthA rrorceoeSo,uthD,,kota

Final Focused Feasibilit_ Study for Operable Unit I

_-- 3.0 GENERAL INTERIM RESPONSE ACTIONS

3.1 DESCRIPTION OF ALTERNATIVES

Media-specific actions consistent with the remedial action objectives include any combination of

treatment, containment, excavation, extraction, disposal, institutional controls and no action.

This action is not the final response action for OU-1; however, it is expected to reduce organic

contaminant concentrations in portions of OU-1 soils and ground water, control the movement of

•" source (fire pit) area contamination in the FPTA to ground water and reduce the risks associated with

those contaminants. The alternatives considered in this FFS are limited in scope because this is an

interim action to reduce immediate risks and contain contamination at OU-1.

As explained in Presumptive Remedies: Policy and Procedures (OSWER Directive 9355.0-47FS),

presumptive remedies are preferred technologies for common categories of sites. (USEPA, 1993A).

"-- Presumptive remedies are based on the historical selection of remedial actions for common sites. The

EPA has evaluated the technologies that have been consistently selected against the selection criteria

set out in the NCP; reviewed available performance data on the application of the remedy; and

determined that a particular remedy, or set of remedies, is presumptively the most appropriate for

addressing specific types of sites.

The EPA notes that presumptive remedies are expected to be used at all appropriate sites. While

specifying specific remedies, the directives recognize and allow for the examination of additional

-- technologies or remedial approaches under unique site conditions. Benefits of presumptive remedies

include a focusing of resources and a tool for the implementation of site remedy acceleration within

the Superfund Accelerated Cleanup Model (SACM). Presumptive remedies do not preclude the

consideration of innovative technologies should these technologies prove to be as effective or

superior to the presumptive remedy.

During the FS process, the presumptive remedy allows for the streamlining of the FS approach. This

includes the elimination of treatment technology identification, screening of technologies, and the

screening of alternatives. Refinement of alternatives and their detailed analysis is streamlined in the

--" process. This approach is possible because the EPA has conducted an analysis of potentially available

technologies for the presumptive remedies. The EPA determined that certain technologies are

routinely and appropriately screened out based on effectiveness, Implementability, or excessive cost,

or have not been selected under the nine criteria analysis identified for the FS process.

-- Presumptive Remedies: Site Characterization and Technology Selection for CERCLA Sites with

Volatile Organic Compounds in Soils (Directive 9353.048FS) was used to streamline the FS process

for OU-I. (USEPA, 1993B). The directive establishes soil vapor extraction (SVE), thermal

_ desorption, and incineration as presumptive remedies for VOC contaminated soil. The approach

streamlines the detailed analysis of alternatives within the FS. The presumptive remedies are expected

to be used for all VOC sites except under unusual circumstances. Data available for OU-1 does not

v indicate any unusual circumstances that may preclude the presumptive remedy.

SVE is the primary presumptive remedy. Performance data indicates that SVE is an effective in-situ

-- process that can be performed at relatively low cost. Treatability studies conducted in 1994 confirmed

W:I55202W.l_ORTSWFSOU-I.FIN 3-1 March 1995
-- Ellsworth Air Force Base, South Dakota

Final Focused Feasibility Study for Operable Unit 1

,,,, SVE to be a viable remediation method. (USAF, 1994) In situations where SVE may not work,

thermal desorption may be the more appropriate response technology. Incineration may be

appropriate for a limited number of situations.

Although no published guidance is available relating to presumptive remedies for ground water, a

streamlined approach was employed at OU-! in a response to using focused FS approaches. The

•- universe of successfully applied response strategies can be limited by examining the characteristics

of OU-I. Alternatives should consider long-term extraction and treatment remedies for restoration

and/or containment. Discharge components should evaluate options for on-site (to surface water)

"" or off-site (to publicly owned treatment works) (POTW) discharge. Technologies for treatment

include air stripping, activated carbon, chemical precipitation, biologic reactors, ion exchange, and

chemical and/or ultra-violet (UV) oxidation.

3.1.1 Alternative I - No Action

The no action alternative represents the baseline condition at OU-1 and refers to taking no further

action until the final remedy is selected and embodied in a ROD for OU-1.

3.1.2 Alternative 2 - SVE for Source Soils and Source Removal and Downgradient

Containment for Ground Water

This alternative includes treatment of contaminated source area subsurface soils (vadose zone and

capillary fringe contaminated soils within the gravel unit are targeted for treatment) and ground water

•_" by SVE and ground water extraction wells in the area of historical fire protection training activities.

In addition, this alternative would include containment of the downgradient ground water plume

south of the source area by operation of the existing interceptor trench (USAF, 1991), located

" approximately 500 feet south of the fire training area.

The existing trench should intercept the highest concentration of contaminated ground water

"- downgradient of the fire pit source area but will not intercept all contaminated ground water. The

trench was installed by excavating with a backhoe and installing 50 feet of 4-inch screened

interceptor lateral, a 12-inch sump, cleanout, and gravel pack in the fall of 1990. The finished

excavation was approximately 22 feet deep sloping from east to west (USAF, 1991).

•.-, Organic sampling results from surface and near surface soils from the FPTA indicated jet fuel to be

the primary contaminant. The highest concentrations of organics in soils were located from the

surface to the capillary fringe beneath the FPTA and in the capillary fringe to about 800 feet to the

south.

Vertical SVE wells will be installed to intercept the gravel layer above the fractured shale in the fire

training area and selected SVE wells will be constructed to act as ground water extraction wells. The

estimated depths of the SVE wells would be from approximately 15 to 20 feet below ground surface

(BGS). Extracted soil gas, condensate and ground water will contain both VOCs and hydrocarbons

-,,- and will be treated at a centrally located treatment plant which will also provide treatment for waste

streams generated by the OU-4 IRA and the Otibase JP-4 Plume Early Action. Water and condensate

treatment will consist of gravity separation, air stripping, filtration and liquid phase granular activated

-- carbon, monitoring of treated water with effluent discharge approximately 800 feet upstream of Pond

W.'_55202h_EPORTSLV'17SOU-1.FIN 3-2 March 1995
- 17 [ 2 0 eUswor,hAirForce Base,So.thOakota

Final Focused Feasibility Study for 0t_erable Unit 1

,,, 001. The extracted soil gas is expected to contain high concentrations of VOC initially and will be

treated using thermal oxidation.

The area targeted for treatment by SVE is defined by the area of historical fire training exercises

(Figure 1-3). The vertical dimension of the area targeted for treatment by SVE is defined by the

gravel unit depicted in Figure 1-5. The volume of soil to be treated by SVE includes both vadose zone

(unsaturated zone) and capillary fringe zone (saturated zone where ground water is held up by

capillary forces against the force of gravity) soils. The ground water extraction included in the IRA

will allow treatment of capillary fringe zone soils by SVE.

The IRA will not address surface and near-surface soils in fire pit fill areas or portions of the vadose

zone in native silty clay which may be a significant source of vadose zone and ground water

contamination. The fire pit(s) were constructed by excavating within the upper silty clay and filling

with a mixture of clay and gravel. The portion of the vadose zone in native silty clay below these fire

_- pit fill areas is also expected to contain high concentrations of contaminants which are not targeted

for treatment by the SVE system proposed under the IRA. The fire pits and the native silty clay are

expected to be addressed by the final remedial action.

Based on the 1994 pilot treatability study conducted in the fire training pit area (USAF, 1994), OU-1

appears to be a very good candidate for SVE. The treatability study reported high air flow rates and

_ low vacuum pressures suggesting a favorable lithotogy, acceptable soil air permeabilities, excellent

contaminant removal, and an acceptable radius ofinfiuence. All indications from the pilot treatability

study are that SVE is feasible to implement at this site.

The alternative would control/contain movement of source area contaminants by removing soil gas

containing volatile organic contaminants in the capillary fringe zone and intercepting the ground water

contaminate plume downgradient of the source area. This will reduce immediate risks associated with

downward movement of volatile contaminants in the source area. Risks associated with organic

COCs in surface and near surface soils in the source area and other organic COCs in source area soils

-- would not be addressed by the interim action. The alternative would address the organic COCs in the

plume downgradient of the source area but will not address treatment of dissolved arsenic. Low

concentrations of dissolved arsenic are expected to be present in the treated water and monitoring

-- of the water will be necessary to ensure compliance with applicable effluent limits. Additional control

of the source area itself and of inorganic COCs must be evaluated during the development of the final

remedial action for OU-1. This alternative will not impede implementation of the final remedy to

reduce risks to acceptable levels.

W..tS5202q_EPORTSWFSOU-I.FIN 3-3 March 1995
-.- :I"'ti. 2 1 Etlswor bFo,'ce ase,So,,tDh akota

Final Focused Feasibili_ Study for Operable Unit 1

._ 4.0 EVALUATION OF ALTERNATIVES

The National Oil andHazardous SubstancesPollution Contingency Plan (NCP) includes nine criteria

that alternatives must be evaluated against. The alternatives are evaluated against each of these

criteria and then against each other to determine the preferred alternative.

4.1 CRITERIA 1 - OVERALL PROTECTION OF HUMAN HEALTH AND THE

ENVIRONMENT

Alternative 1 (no action) does nothing to reduce threats and potential threats to human health and the

environment until the final remedy(ies) are selected and implemented.

Alternative 2 (SVE and ground water removal and treatment) provides for removal of VOCs from

soils in the capillary fringe beneath the FPTA to approximately 800 feet to the south and shallow

downgradient ground water, which will reduce potential risks to human health and retard future

transport of organic COCs from OU-1.

The combination of liquid and air phase removal will result in a permanent reduction in source

contaminationin the subsurface soil capillary fringe area. In addition, liquidremoval will effectively

limit the degree of downgradient transport. As a result, Alternative 2 will decrease contaminant

concentrations and the lateral extent of movement that presents a potential health risk.

4.2 CRITERIA 2 - COMPLIANCE WITH ARARs

ARARs are applicable or relevant and appropriate requirements. 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. 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. 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.

The analysis of ARARs in this document has been limited to the scope of the interim action. Other

ARARs may apply to final remedies. A summary and evaluation ofpotentiai federal and state ARARs

is presented in Table 4-1 at the end of this section.

VK'I55202kr_PORTSbvFSOU-I.FIN 4-I March 1995
•-, Ellsworth Air Force Base, South Dakota

47 t 2 2 FinalFocusedFeasibilityStudyforOeerableUnitl

,., Chemical-specific cleanup goals for soil and ground water at OU-1 are summarized as follows:

OU-1 Soil and Ground Water Cleanup Goals

Parameter CleanupLevel Media

JP-4 10,000/zg/kg Soil

Benzene 5/zg/L Water

1,2-Dichloroethane 5 tzg/L Water

1,1-Dichloroethylene 7/zg/L Water

1,2-Dichloroethylene 70/zg/L Water

Tetrachloroethylene 5/zg/L Water

Trichloroethylene 5/zg/L Water

1,1,1-Trichloroethane 5 tzg/L Water

Vinyl Chloride 2 _zg/L Water

The basis for the soil cleanup level is the State of South Dakota regulation setting the maximum

allowable JP-4 (as total petroleum hydrocarbons) concentrations at 10,000/xg/kg to 100,000/_g/kg,

depending on site-specific criteria such as depth to ground water and permeability of geologic

materials. The basis for the ground water cleanup levels are the Safe Drinking Water Act MCLs. An

interim action waiver would need to be invoked for the chemical-specific ARARs in soil and ground

water.

Alternative 1 (no action) delays meeting ARARs until the final remedy is implemented.

Alternative 2 (SVE and ground water removal and treatment) provides a preliminary step toward

achieving chemical-specific ARARs for the shallow ground water downgradient of the burn pit areas

-- and site soils in the capillary fringe beneath the burn pit areas. Implementation of the IRA would

prevent further transport of contaminants and quickly achieve significant risk reduction. Upgrade of

the interim SVE and ground water removal system has the potential to achieve the chemical-specific

ARARs for shallow ground water farther downgradient, if selected as the final remedy. Ground water

monitoring at OU-1 will be conducted during implementation of the IRA to determine the progress

-- of the IRA in meeting chemical-specific ARARs.

No location-specific ARARs have been identified for the IRA. The site and any treatment facilities

_ that would be constructed are not located within a 1O0 year flood plain, wetland, historical site or

sensitive ecosystem/habitat.

W..._55202__PORISkhT_OU-I.FIN 4-2 March 1995
4"1t 23

Ellsworth Air Force Base, South Dakota

Final Focused Feasibility Study for Operable Unit 1

.- Action-specific ARARs that will be met include:

• Design of the liquid treatment components to meet the substantive requirements of the

-- Clean Water Act (CWA) and state and federal requirements for monitoring and discharge

of treated ground water.

• Design of the air treatment components to meet the substantive requirements ofthe Clean

Air Act and state requirements and regulations (if developed) for the system air discharge.

Discharge of treated ground water is subject to the requirements of a National Pollutant Discharge

Elimination System 0VPDES) permit for Pond 001. Monitoring of the treated water will be performed

to ensure discharge of hazardous wastes does not occur. Discharge effluent limits will be proposed

and developed as part of the remedial design element of the IRA and are subject to state and federal

approvals and reviews in accordance with the provisions of the CWA.

4.3 CRITERIA 3: LONG-TERM EFFECTIVENESS AND PERMANENCE

Alternative 1 delays any action until the final remedy is selected and is unlikely to provide long-term

effectiveness and permanence. Contamination will move further outward into the environment,

increasing the volume of contaminated materials and the subsequent cost of remedial actions.

Alternative 2 will permanently remove and destroy most of the VOCs from the capillary fringe soils

in the source area at the site. In addition, ground water extraction downgradient of the source area

will reduce the concentrations of organic COCs by treatment (air stripping and carbon absorption)

and contain further downgradient movement of COCs in ground water from the source area while

the final remedy for the site is evaluated. Due to uncertainties in the hydrogeological characteristics

of the shallow aquifer and the extraction system design parameters, complete removal of

contaminants may require system expansion. Information provided by the system operation will be

used to evaluate long-term effectiveness and permanence of the interim remedy and will provide

useful information for development of the final remedy for OU-1. No residuals will be land disposed

and all wastes will be treated to meet applicable or relevant and appropriate requirements. Inorganic

COC:; must be addressed by the final action implemented at OU- 1.

4.4 CRITERIA 4: REDUCTION OF TOXICrrY, MOBILITY, AND VOLUME THROUGH

,_ TREATMENT

Alternative 1 delays reduction of toxicity, mobility, and volume since no treatment would be taking

_ place. Contaminants will continue to move further into the environment, resulting in a greater volume

of contaminated materials.

-- Alternative 2 utilizes established treatment technology to reduce the risks posed by the organic COCs

at depth in the capillary fringe beneath the source area and in ground water downgradient of the

source area.

The mass of VOCs in the subsurface soils beneath the source area will be permanently reduced and

the potential for further movement of VOCs to ground water beneath the source area will be

-- decreased. VOCs removed via SVE will be partitioned to the air phase and thermally destroyed.

W.:155202_ORTS_PSOU-I.FIN 4-3 March 1995
471 2,1

Ellsworth Air Force Base, South Dakota

Final Focused Feasibility Study for Operable Unit 1

,., Other organic COCs will be removed by carbon absorption. The carbon absorbent material will be

periodically disposed or reactivated as needed. Liquid discharge from the treatment system will be

monitored to verify state and federal discharge requirements are met. VOCs carried by the removed

-- soil gas will be thermally treated. No residuals from the treatment will remain on the site.

4.5 CRITERIA 5: SHORT-TERM EFFECTIVENESS

Alternative 1 offers no immediate risks to the community. Delay of action allows for contaminants

to migrate further, offering a longer term concern and no reduction in risk.

Alternative 2 will be designed to protect the community and workers during remedial actions.

Worker protection will be consistent with the OSHA requirements in 29 CFR 1910.120 and the site

-- Health and Safety Plan and Contingency Plan during construction and operation.

Construction of SVE and ground water recovery wells will be monitored to ensure safe ambient VOC

concentrations outside of the active work areas. Removed, affected soil from construction of the

wells will be placed back onto the burn pit areas of the FPTA, graded, covered with clean fill and left

in-place until the final remedial action. All air discharges from the SVE treatment operations will be

thermally treated to oxidize VOCs. No adverse environmental impacts are expected from

implementation of Alternative 2 and risks associated with OU-1 source areas will be reduced.

4.6 CRITERIA 6: 1MPLEMENTABILITY

-- Alternative 1 offers no implementability concerns since it is technically and administratively feasible

and does not rely on the availability of services and materials.

Alternative 2 will utilize proven "off-the-shelf' technology and standard construction methods.

Adequate construction equipment and services are available. The equipment for on-site pretreatment

is commercially available.

Access to the site is available through existing roadways and the topography above the VOC plume

allows access to construction and drilling equipment. Road construction will be limited to that needed

-- to install the treatment facilities and provide access for system monitoring and maintenance. Off-Base

access for implementation of this IRA is not required since all SVE wells and the existing ground

water recovery trench are located entirely on the Base.

Uncertainties associated with this operation involve methods to maximize the effectiveness of soil gas

_ and ground water extraction. Changes in pumping rates, alternating operating wells and/or sporadic

pumping may be necessary to determine the most effective extraction methods.

,,, The action is administratively feasible. Discharge of the treated water will comply with substantive

state and federal requirements. Amendment of the existing NPDES permit for discharge of treated

water upstream of Pond 001 may be necessary. During the remedial design phases of the IRA,

,_ discharge effluent limits for the treated ground water will be evaluated, proposed and implemented.

Monitoring of the treated water will be conducted to ensure compliance with federal and state

discharge requirements. Also, discharge of treated air from the thermal oxidizer system at the thermal

WAS5202_ORTSaFFSOU-I.FIN 4-4 March 1995
,. 71 25 ,,, Ellsworth Air Force Base, South Dakota

Final Focused Feasibility Study for Operable Unit 1

,,, oxidizer stack will be monitored to ensure compliance with substantive federal and state air quality

requirements.

4.7 CRITERIA 7: COST

Alternative 1 does not result in any cost for design or implementation.Operation and maintenance

costs (quarterly ground water monitoring) are $9,500 per monitoring event which results in a present

worth cost of $36,000 based on an annual interest rate of eight percent over one year.

-- Alternative 2 is estimated to cost $1,266,000 in capital cost and $686,000 per year to operate which

results in a present worth cost of $1,888,400 based on an annual interest rate of eight percent over

one year. These costs are total costs for the treatment facilities and would be allocated among other

-- interim actions being considered at other OUs.

4.8 CRITERIA 8: STATE ACCEPTANCE

This criteria will be assessed following comments on the RI/FS to date and the Proposed Plan for this

action.

4.9 CRITERIA 9: COMMUNITY ACCEPTANCE

This criteria will be assessed following public comment on the focused feasibility study information

and Proposed Plan.

W:_55202k_.EPORTS_FSOU-1.F1N 4-5 March 1995
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Draft Final Focused Feasibility Study for Operable Unit 1

5.0 REFERENCES

Chiang, C.Y, E.Y. Chai, J.P. Salanitro, V.D. Colthart, and C.L. Klein. 1989. Effects of Dissolved Oxygen

-- on the Biodegradation of BTX in a Sandy Aquifer. In Petroleum, Hydrocarbons and Organic

Chemicals in Ground water: Prevention, Detection and Restoration - A Conference. Houston.

-- Delaune, R.D., G.A. Hambrick, and W.H. Patrick. 1980. Degradation of Hydrocarbons in Oxidized and

Reduced Sediments. Marine Pollution Bulletin 11:103-106.

-- DeYoe, John. 1993. USAF. Personal Communication.

Lyman, W.J., W.F. Reehl, and D.W. Rosenblatt. 1982. Handbook of Chemical Property Estimation

-- Methods. McGraw-Hill, New York.

_ U.S. AirForce (USAF). 1985. Installation Restoration Program. Phase I - Records Search. Ellsworth Air

Force Base, Rapid City, South Dakota. Prepared for U.S. Army Corps of Engineers - Omaha

District, Omaha, Nebraska.

U.S. Air Force (USAF). 1988. Installation Restoration Program, Phase II, Stage 1, Final Remedial

Investigation Report. EIlsworth Air Force Base, Rapid City, South Dakota. Prepared for U.S. Army

-- Corps of Engineers - Omaha District, Omaha, Nebraska.

U.S. Air Force (USAF). 1989. Installation Restoration Program, Phase II, Stage 2, Final Remedial

Investigation Report. Ellsworth Air Force Base, Rapid City, South Dakota. Prepared for U.S. Army

Corps of Engineers - Omaha District, Omaha, Nebraska.

U.S. Air Force (USAF). 1991. Draft Pilot Study Report. EUsworth Air Force Base, Rapid City, South

Dakota. Prepared for US. Army Corps of Engineering - Omaha District, Omaha, Nebraska.

U.S. Air Force. 1994. Final Remedial Investigation Report Operable Unit 1 at Ellsworth Air Force Base,

South Dakota. December 1994.

U.S. Air Force. 1994. Treatability Studies Technical Report, Operable Units 1, 2, and 4, Ellsworth AFB,

South Dakota. November 1994.

U.S. Environmental Protection Agency (EPA). 1993A Presumptive Remedies: Policy and Procedures

(Directive 9355.0-47FS). U.S. EPA Office of Emergency and Remedial Response, Washington, D.C.

U.S. Environmental Protection Agency (EPA). 1993B. Presumptive Remedies: Site Characterization and

Technology Selection for CERCLA Sites with Volatile Organic Compounds in Soils. (Directive

-- 9355.0-48FS). U.S. EPA Office of Emergency and Remedial Response, Washington, D.C.

Ward, D.M., and T.D. Brock. 1978. Anaerobic Metabolism of Hexadecane in Marine Sediments.

-- Geomicrobiol. J 1:1-9.

W.'_52027_.EPORTS_--FSOU-1.FIN 5-1 March 1995
17!. 33

Ellsworth Air Force Base, South Dakota

Draft Final Focused Feasibili_ Study for Operable Unit 1

•- Ward, D., R.M. Atlas, P.D. Boehm, and J.A. Clader. 1980. Microbial Biodegradation and the Chemical

Evolution of Amoco Cadiz Oil Pollutants. Ambio 9:277-283.

m

W..'_55202q_.EPORTS_"FSOUI-.FIN 5-2 March 1995
47t 34 " Ellsworth Air Force Base, South Dakota

Draft Final Focused FeasibiligJ Stud)/for Operable Unit l

_ 6.0 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.

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

/zg/l: Micrograms per liter

mg/l: 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

OU: Operable Unit

O&G: Symbols for oil and grease

-- PAIl: Polynuclear Aromatic Hydrocarbon

PCB: Polychlorinated Biphenyl; liquids used as a dielectrics in electrical equipment

_ PCE: Perchioroethylene; liquids used in degreasing or paint removal.

W:I552021REPORTSWFSOU-I.F1N 6-I March 1995
Ellsworth Air Force Base, South Dakota

Draft Final Focused Feasibility Study for Operable Unit 1

_ PL: Public Law

ppm: Parts per million by weight 4 7 1 3 5

RCRA: Resource Conservation and Recovery Act

RI/FS: Remedial Investigation/Feasibility Study

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

TDS: Total Dissolved Solids

TOC: Total Organic Carbon

TSD: Treatment, storage or disposal sites/methods

USAF: United States Air Force

USEPA: 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

W.'_55202_,EPORTS_PsOU-1.FIN 6-2 March 1995
Ellsworth Air Force Base, South Dakota

Draft Final Focused Feasibili_ Study for Operable Unit 1

471 36

APPENDIX A

FIGURES

W.'_552027UEPORTSWFSOU-I,FIN March 1995
"i

- _" d FIGURE I-I

I,,..I" _" M AREA LOCATION MAP

•m '0 ELLSWORTH AFB, SOUTH DAKOTA

, PREPAREDFOR U.S. ARMY CORPS,OF ENGINEERS
INST_¢L,_'nO8OU N NOARY

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-- OU-5 LANDFILL 4

OU-T LOW LEVEL RADIATION WASTE BURIAL AREA

• OU-B EXPLOSIVE ORDNANCE DISPOSAL AREA S PRAMITOL SPILL

OU-B OLD AUTO HOBBY SHOP AREA -- OU-IO NORTH HANGAR COMPLEX

ul -- OU-ll BASEWIDE GROUNO WATER ___ I _'%_

_ OU-12 NAROFILL NO.I

"4, NOTE_ ELLSWORTHAPB,S,2M,L_EAST RAPC, ,OTY. _ JUST NORTH OF AND ADJACENT TO BO(_XELDER "

"_ Ia SOUR I CE: OU-4 RI REPORT (EA, 1994) i i

_ _ ' FIGURE I-2

" _" SITE MAP . UJ

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PREPARED FOR U.S. ARMY CORPS OF" ENGINEERS

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