PB94-964637
EPA/ROD/R10-94/093
January 1995
EPA Superfund
Record of Decision:
Eielson Air Force Base,
Operable Unit 6, AK
9/27/1994
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Final
EIELSON AIR FORCE BASE
OPERABLE UNIT 6
RECORD OF DECISION
Prepared for
Eielson Air Force Base
through
Armstrong Laboratory
Brooks Air Force Base
San Antonio, Texas
July 1994
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CONTENTS
DECLARATION OF THE RECORD OF DECISION
DECISION SUMMARY
1. SITE NAME, LOCATION, AND DESCRIPTION 1
2. SITE HISTORY AND ENFORCEMENT ACTIVITIES 5
2.1 SOURCE AREA WP38 (OU6) 5
2.2 ENFORCEMENT ACTIVITIES 8
3. HIGHLIGHTS OF COMMUNITY PARTICIPATION 9
3.1 COMMUNITY RELATIONS PRIOR TO THE FINAL ACTION 9
3.2 COMMUNITY RELATIONS TO SUPPORT SELECTION OF A REMEDY . . 9
4. SCOPE AND ROLE OF OPERABLE UNIT 6 11
5. SUMMARY OF SITE CHARACTERISTICS 12
5.1 GEOLOGY AND HYDROGEOLOGY . 12
5.2 NATURE AND EXTENT OF CONTAMINATION 15
6. SUMMARY OF SITE RISKS 25
6.1 HUMAN HEALTH RISKS 25
6.2 ECOLOGICAL RISKS 35
7. DESCRIPTION OF REMEDIAL ALTERNATIVES 38
7.1 REMEDIAL ACTION OBJECTIVES 38
7.2 REMEDIAL ALTERNATIVES 38
8. SUMMARY OF THE COMPARATIVE ANALYSIS OF ALTERNATIVES 43
8.1 OVERALL PROTECTION OF HUMAN HEALTH AND THE
ENVIRONMENT 43
8.2 COMPLIANCE WITH APPLICABLE OR RELEVANT AND
APPROPRIATE REQUIREMENTS 43
8.3 LONG-TERM EFFECTIVENESS AND PERMANENCE 43
8.4 REDUCTION OF TOXICITY, MOBILITY, OR VOLUME
THROUGH TREATMENT 45
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CONTENTS (continued)
8.5 SHORT-TERM EFFECTIVENESS 45
8.6 IMPLEMENTABDLITY 45
8.7 COST 45
8.8 STATE ACCEPTANCE 46
8.9 COMMUNITY ACCEPTANCE 46
9. THE SELECTED REMEDY 47
9.1 INSTITUTIONAL CONTROLS 47
9.2 GROUNDWATER MONITORING 48
9.3 STATUTORY REVIEW 48
10. STATUTORY DETERMINATIONS 49
10.1 PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT 49
10.2 ATTAINMENT OF APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS OF ENVIRONMENTAL LAWS (ARARS) 49
10.3 COST-EFFECnVENESS 50
10.4 UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE
TREATMENT TECHNOLOGIES TO THE MAXIMUM EXTENT
PRACTICABLE 50
RESPONSIVENESS SUMMARY
A. OVERVIEW 1
B. BACKGROUND ON COMMUNITY INVOLVEMENT 1
C. SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC COMMENT
PERIOD AND USAF RESPONSES 2
D. REMAINING CONCERNS 3
ATTACHMENT A. COMMUNITY RELATIONS ACTIVITIES AT EIELSON AFB 6
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EIELSON AIR FORCE BASE
OPERABLE UNIT 6
DECLARATION OF THE RECORD OF DECISION
Site Name and Location
Operable Unit 6
Eielson Air Force Base
Fairbanks North Star Borough, Alaska
Statement of Basis and Purpose
This decision document presents the selected remedial action for Operable Unit 6 (OU6) at
Eielson Air Force Base (AFB), Alaska, which was chosen in accordance with the
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), as
amended by the Superfund Amendments and Reauthorization Act (SARA), and, to the extent
practicable, the National Contingency Plan (NCP). This decision is based on the
Administrative Record for the site.
The State of Alaska concurs with the selected remedy.
Assessment of the Site
Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the response action selected in this Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare, or the environment.
Description of the Selected Remedy
The selected remedy for OU6 includes institutional controls to restrict the use of groundwater
and groundwater monitoring to ensure protection of human health and the environment.
Major components of the OU6 selected remedy are
• monitoring the groundwater beneath and adjacent to the site to evaluate contaminant
migration and natural attenuation (monitoring of OU6 will be incorporated in the
Eielson AFB site-wide monitoring program)
• maintaining institutional controls that restrict access to groundwater and
groundwater development at the site as long as hazardous substances remain on the
site at levels that preclude unrestricted use.
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These controls will remain in effect as long as the Air Force maintains active control of the
area or until the groundwater contamination dissipates to levels that do not pose an
unacceptable risk to human health or the environment. The specific institutional controls to
be implemented at OU6 by land use controls are as follows:
1. development of a site map showing the areas currently and potentially impacted
by groundwater contaminants to determine where the controls are to be
implemented
2. posting of warning signs, prohibiting consumption and domestic use of the
groundwater or the installation of additional wells for other than groundwater
monitoring purposes;
3. continuing to provide an alternate water supply of potable water to OU6 for
drinking and domestic use
4. securing of existing water supply and groundwater monitoring wells.
In addition, to ensure long-term integrity of the above land use controls, the Air Force will
ensure that, to the extent that groundwater contamination remains above unacceptable levels,
deed restrictions or equivalent safeguards will be implemented in the event that property
containing such contamination is transferred by the Air Force.
Statutory Determination
The selected remedy is protective of human health and the environment, complies with
Federal and State 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 to the maximum extent practicable. However, treatment of the
groundwater was not selected due to the complex hydrogeology of the fractured bedrock, the
limited extent of contamination in a remote area of the base, and the reliability of available
institutional controls. Therefore, the remedy does not satisfy the statutory preference for
treatment as a principal element.
Because the remedy will result in the continued presence of hazardous substances on the site
above health-based levels, a review will be conducted within 5 years of commencement of the
remedial action to ensure that the remedy continues to provide adequate protection of human
health and the environment.
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This signature page is part of Eielson AFB Operable Unit 6 Record of Decision,
Final Version
Signature and Support Agency Acceptance of the Remedy
Thomas WJL. McCall Date
Deputy Assistant Secretary of the Air Force
(Environment, Safety, and Occupational Health)
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This signature page is pan of Eielson AFB Operable Unit 6 Record of Decision,
Final Version
Signature and Support Agency Acceptance of the Remedy
J.
William D. McGee Date
Regional Administrator
Northern Regional Office
Alaska Department of Environmental Conservation
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This signature page is part of Eielson AFB Operable Unit 6 Record of Decision,
Final Version
Signature and Support Agency Acceptance of the Remedy
•* •>- 'r
Clarke . Date
' Regional Administrator
Region 10
U.S. Environmental Protection Agency
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EIELSON AIR FORCE BASE
OPERABLE UNIT 6
DECISION SUMMARY
1. SITE NAME, LOCATION, AND DESCRIPTION
Eielson Air Force Base, covering an area of approximately 19,000 acres, is in the interior of
Alaska, 100 miles south of the Arctic Circle, about 25 miles southeast of Fairbanks along the
Richardson Highway (Figure 1). About 3,650 acres are improved or partially improved, and
the rest encompasses forest, wetlands, lakes, and ponds. The base is bounded on the east and
south by Fort Wainwright, a U.S. Army installation, and on the west and north by private and
public land. The base is isolated from major urban areas. The adjacent public and private
land is zoned for general use.
Eielson AFB, a major employer in the Fairbanks area, has approximately 3,400 military
personnel and 500 civilian workers. The total residential population of the base is 5,132; the
total population Giving and working on the base) is approximately 10,000. The residential
and occupational populations are primarily concentrated in the developed portion of the base.
The base is active, with ongoing functions that include, in addition to the military mission,
support work, school, and recreational activities. The base has three elementary schools and
one junior-senior high school. There is one child care center and one medical and dental
clinic.
The base is located in the Tanana River Valley, and most of the developed portion is built on
fill material. The developed portion of the base is an area of low relief, with elevations
averaging about 550 ft above sea level. The undeveloped east and northeast sides of the base
are hilly, with elevations as high as 1,125 ft above sea level. Two-thirds of the base is on
soils containing discontinuous permafrost. Half of the potential agricultural soils are currently
being used for recreation facilities, ammunition storage areas, the Arctic Survival Training
School, and other Air Force developments. Animals are abundant on Eielson AFB. The base
supports a variety of recreation and hunting opportunities. There are no resident threatened or
endangered species of plants and animals on the base.
OU (Operable Unit) 6, in the southeast comer of Eielson AFB (Figure 2), consists of a
ridgetop where eight 50,000-gallon above-ground fuel tanks stored diesel and jet fuel from
1956 to 1972, the hillside below it, and the base of the hill, where there is a ski lodge and a
skeet range at the edge of the Tanana River plain. The tanks were removed in 1977; in 1986
evidence was found that there had been releases of fuel into a fractured-bedrock aquifer in the
ridge. Contaminated water flowed from there down to the alluvial floodplain aquifer. The
latter contains an unknown but probably large amount of permafrost down to about
120-150 ft below the surface at the site.
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420
Scale miles
OU6
(SOURCE AREA WP38)
LEGEND
Boundary
Hi^hwoy
Riven end Creeks
Figure 1. Eielson Air Force Base, Alaska.
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Date:
Date:
F: \AJW\EIESON\VICINITY.OWG
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LEGEND
Eielson AFB Boundary
Operable Unit 6 (OU6)
-f Base Water Supply Well
—.—s
J
..J
Eielson AFB Boundary j
NORTH
Eielson AFB Boundary J
(oue) :
^ Eielson AFB Boundary |
M2 1
=»•=
Scale: miles
Figure 2. Map showing location of Operable Unit 6.
Eielson Air Force Base.
Drawn
AJW
Reviewed
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Date 4/18/94
Date
Date
Date
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Beneath the developed portion of the base the floodplain aquifer is shallow and unconfmed in
200-300 ft of unconsolidated alluvial sands and gravel overlying bedrock of relatively low
permeability. This aquifer is characterized by high transmissivities and relatively flat
ground water gradients. There is evidence of discontinuous layers of permafrost in it.
Although there are seasonal fluctuations, groundwater is generally encountered about 8 ft .
below grade, and it flows generally to the north-northwest, locally influenced by surface water
bodies (e.g., French Creek, Garrison Slough) and groundwater extraction from the base supply
wells.
Groundwater is the only source of potable water at the base and in the communities near it.
Potable water in the main base system is treated to remove iron and sulfide. The aquifer is
also the principal source of water for various other industrial, domestic, agricultural, and fire-
fighting uses.
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2. SITE HISTORY AND ENFORCEMENT ACTIVITIES
2.1 SOURCE AREA WP38 (OU6)
2.1.1 Site History
Operable Unit 6 is a single contaminated source area, also referred to as WP38, located in the
southeastern area of the base. This OU includes approximately 200 acres of southwest-facing
hillside near the Eielson AFB Ski Lodge (Figure 3). Present uses of the area include
downhill and cross-country skiing, winter survival training, snowmobiling, and setting of
permitted trapping lines.
The immediate source area was a fuel storage area built in 1956. Eight 50,000-gallon above-
ground tanks and a number of smaller tanks were located on the crest of the ridge, along the
southwest side of "B" Battery Road. The tanks were used to .store aviation and/or diesel fuel.
Use of the tanks was discontinued in 1972, and the tanks and their associated piping and
concrete sub-bases were removed in 1977.
Groundwater contamination was detected in 1986, when routine sampling revealed the
presence of benzene (a petroleum-related contaminant) in the water supply well in the
basement of the ski lodge and then in a second well installed slightly uphill of the lodge.
In 1988, benzene was detected in a third water supply well, also installed in 1986.
Subsequent sampling in 1988, 1989, and 1993 has confirmed the presence of petroleum-
related contaminants in the groundwater near the ski. lodge. In 1987, all three of the water
supply wells at the site were removed from service, and since then water from the main base
wells has been trucked to the site and stored in an underground tank adjacent to the lodge to
meet all site water needs.
The contamination in the groundwater is believed to be from leaked aviation or diesel fuel
from the storage tanks. The petroleum-related contaminants moved through the soils and
weathered bedrock at the top of the ridge into the highly fractured bedrock below; once in the
upper portion of the bedrock, the contaminants are thought to have continued to move
downward through the bedrock along fractures until they reached the groundwater. The
contamination appears to be relatively isolated within the bedrock.
2.1.2 Previous Investigations
OU6 has been evaluated under the U.S. Air Force Installation Restoration Program (IRP) and
the CERCLA remedial investigation/feasibility study (RI/FS) process. The studies listed
below document preliminary investigations of OU6:
• 1982 IRP Phase I Records Search (CH2M Hill 1982)
• 1988 IRP RI/FS Stage 3, Volume II (HLA 1989)
• 1989 IRP RI/FS, Stage 4, Volumes I through V (HLA 1990)
• 1989 IRP RI/FS, Stage 4, Volumes VH through XVIH (HLA 1991)
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LEGEND
Xllfr
©
Swamp
former Tank Locations
600
Figure 3. Ski hill with locations of former fuel storage tanks (OU6),
Eielson AFB, Alaska.
Drown:
Date:
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The results of these studies are described in Chapter 5, Summary of Site Characteristics.
1982 IRP Phase I Records Search The literature search for possible sources of
contamination at Eielson AFB (CH2M Hill 1982) did not uncover any evidence of releases at
the OU6 site.
1988 IRP RJ/FS Phase II, Stage 3 Investigation HLA (Harding Lawson Associates) was
commissioned in 1988 to investigate OU6 and prepare a Phase n Step 3 report (HLA 1989).
HLA conducted an initial field investigation of source area WP38 from July through
November 1988. The investigation comprised a soil vapor survey; seismic and geophysical
examination of the geology, hydrogeology, and possible permafrost at the site; and the drilling
of soil borings and installation of vadose vapor monitoring wells and groundwater monitoring
wells. Field tasks included surface reconnaissance, surface geophysics, a soil vapor survey,
soil borings, borehole geophysical logging, monitoring well installation, soil and groundwater
sampling, aquifer testing, and water-level survey.
The investigations were carried out along the ridge line, on the ski slope east of the tank
storage area, in areas along the utility access road west of the tank storage area, and along the
road from the main base to the ski lodge. The five soil borings drilled at the site ranged in
depth from 76 to 325 ft Soil borings were drilled downslope of tank locations, at mid-slope
near the ski lodge, along the base of the hill, and out into the lowlands. Several borings were
converted to monitoring wells and designated 38M01 through 38M05.
The soil vapor survey was performed in the former POL storage tank area and other
accessible areas around the site; the geophysical survey was performed to assess the presence
of permafrost, investigate depth to groundwater, and aid in the location of monitoring wells.
A slug test was conducted in monitoring well 38M03 and a groundwater sample from well
38M01 was analyzed to determine the hydrocarbon fingerprint.
A photoionization detector (PID) OVM (organic vapor monitor) was used to screen the soil
boring samples for volatile organic compounds, and the samples with the highest reading
from each borehole were analyzed in a field laboratory for selected organic compounds and
submitted to a laboratory to be analyzed for petroleum product indicator chemicals selected
on the basis of their mobility, persistence, and toxicity: benzene, toluene, ethylbenzene, and
xylenes (BTEX) and total petroleum hydrocarbons (TPH). Indicator chemicals selected for
groundwater analysis were BTEX and chlorobenzene, bis(2-ethylhexyl)-phthalate, and
2-methylnaphthalene.
1989 IRP RI/FS Phase n, Stage 4 Investigation HLA conducted Phase n, Stage 4 of the
IRP field investigation from August through November 1989 (HLA 1990, 1991). The
investigation focused on obtaining additional information on the extent of purgeable aromatics
in the groundwater southwest of the ski lodge and assessment of the fuel-related compounds
beneath the former tank sub-bases. Activities included a seismic refraction survey, soil
borings, installation of groundwater monitoring wells, collection of groundwater samples, and
measurement of groundwater levels.
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The seismic refraction survey was conducted in the vicinity of the former fuel storage tanks
and ski lodge to define the stratigraphic profile, determine the presence of permafrost, and aid
in positioning additional soil borings and monitoring wells. Twenty-four soil borings, ranging
in depth from 12 to 47.5 ft, were drilled on the ski hill near the tank sub-bases (38SB01
through 38SB16; 38M08 through 38M15). Soil borings 38M08 through 38M15 were
converted to vapor monitoring wells. Two borings (38M06 and 38M07) were drilled
southwest of the ski lodge in the lowlands, to depths of 158 and 130 ft, respectively, and
converted to groundwater monitoring wells.
2.2 ENFORCEMENT ACTIVITIES
Eielson AFB was listed on the National Priorities List (NPL) (54 Fed. Reg. 48184) on
21 November 1989 by the U.S. Environmental Protection Agency (EPA). This listing
designated the facility as a federal Superfund site subject to the remedial response
requirements of the Comprehensive Environmental Response,. Compensation, and Liability
Act (CERCLA), as amended by the Superfund Amendments and Reauthorization Act
(SARA). In accordance with EPA policy, Eielson AFB was placed on the NPL on the basis
of its Hazard Ranking System score. Sixty-four potential source areas at Eielson AFB were
divided into six operable units (OUs) and three source evaluation report (SER) groups, on the
basis of commonality of characteristics and of contaminants. Two more potential source
areas were added to the SER groups in 1992, bringing the total to 66.
As a result of Eielson's listing on the NPL, Eielson, EPA, and the State of Alaska Department
of Environmental Conservation (ADEC) entered into a Federal Facility Agreement pursuant to
CERCLA in October 1990. The FFA established a procedural framework for agency
coordination and a schedule for all CERCLA activities conducted at the base. This final
action, the Record of Decision for Operable Unit 6, is undertaken in accordance with the
FFA.
Eielson AFB is also party, with EPA, to a RCRA Federal Facility Compliance Agreement,
signed on 15 June 1988, which required Eielson to pursue RCRA closure at site-specific
hazardous waste management areas. These activities are ongoing at some sites at the base,
but there are no such sites at' OU6.
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3. HIGHLIGHTS OF COMMUNITY PARTICIPATION
3.1 COMMUNITY RELATIONS PRIOR TO THE FINAL ACTION
In accordance with Sections 113(K)(2)(b)(i-v) and 117 of CERCLA, community interviews
were conducted in the early 1990s with local officials, community residents, and public
interest groups to solicit concerns and information needs and to learn how and when citizens
would like to be involved in the CERCLA process at Eielson AFB. The information gathered
during community interviews and other relevant information provided the basis for the
development of the Community Relations Plan (CRP) (USAF 1991).
The community relations staff first interviewed 40 local residents and community leaders to
develop plans to keep residents informed about the cleanup activity at Eielson AFB.
Follow-up interviews and questionnaires of more than 100 residents helped revise the
Community Relations Plan. An environmental cleanup newsletter was created and mailed to
anyone who wished to be on the mailing list, and fact sheets were prepared on various topics
related to cleanup operations. Several times a year, articles describing significant cleanup
events have been released to the base newspaper, The Goldpanner, and to the Fairbanks
Daily News-Miner and the North Pole Independent. These efforts were designed to involve
the Community in the cleanup process through comments they might make on the information
that was furnished.
3.2 COMMUNITY RELATIONS TO SUPPORT SELECTION OF A REMEDY
A Technical Review Committee (TRC) was established in 1992 that included three
representatives of the community (selected by local officials and the Chancellor of the
University of Alaska, Fairbanks), industry representatives, and environmental agency
representatives. In November 1993 a local environmental interest group was invited to
participate. A preliminary version of the Proposed Plan for the remediation of OU6 was
presented to the TRC on 27 January 1994. At that meeting, representatives from the U.S. Air
Force, ADEC, and EPA responded to questions from an audience representing the University
of Alaska, the city of North Pole, and various state and federal agencies.
The RI/FS documents (USAF 1994a, b, and c) and the Proposed Plan (USAF 1994d) for
Operable Unit 6 of Eielson AFB were released to the public in March 1994. The documents
were made available in both the Administrative Record office at the base and in an
information repository maintained at the Elmer E. Rasmussen Library at the University of
Alaska, Fairbanks.
The Proposed Plan for OU6 was advertised twice in two local newspapers, and more than
3,500 copies were added as an insert in the base newspaper and delivered to every home in
the base housing area. A news release announcing the Proposed Plan and a public meeting
on 12 April was sent to all local news media (radio, television, newspapers), and the story ran
on the front page of the base newspaper. The meeting was advertised on the base access
cable channel and in the base information bulletin, and on at least one local area radio station
as well. The First Sergeants Group (the senior enlisted leadership for each unit on the base)
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was briefed on the plan and public meeting, to encourage their people to attend. Copies of
the plan were delivered to various information repositories and to the North Pole City Hall.
A public comment period and public meeting .were advertised on 18 March in the Goldpanner
base newspaper. A 9-inch display ad that highlighted the cleanup efforts was placed in the
North Pole Independent on 18 March and in the Fairbanks Daily News-Miner on 20 and
21 March.
The public meeting for the Proposed Plan was held on 12 April 1994. At that meeting,
representatives from the Air Force, ADEC, and EPA answered questions about problems at
the sites and the remedial alternatives under consideration. About 10 members of the public
attended.
The public comment period on the Proposed Plan ran from 22 March through 22 April 1994.
Comments received during that period, and the Air Force responses, are summarized in the
Responsiveness Summary of this ROD.
This ROD and the attached Responsiveness Summary will be available in the Administrative
Record office and at the information repository listed below:
Elmer E. Rasmussen Library
Arctic and Polar Regions Archives Section
University of Alaska, Fairbanks
Fairbanks, AK 99775
907/474-6594
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4. SCOPE AND ROLE OF OPERABLE UNIT 6
The Federal Facility Agreement organized the CERCLA study sites at Eielson AFB into six
OUs, on the basis of similar source characteristics or contaminants. Operable Unit 6, the
subject of this ROD, addresses the problem of groundwater at the ski hill source area that has
been contaminated by leaks and spills from the fuel tanks and piping formerly located at the
top of the ridge.
The ski hill area is used primarily for recreational and military training purposes.
Groundwater sampled in wells downgradient of the hilltop area has been found to contain
petroleum hydrocarbons, but the groundwater at OU6 is not extracted or used for any purpose
at present. The potential contribution of the bedrock aquifer to groundwater in the vicinity,
and the amount and direction of flow in the bedrock aquifer are difficult to determine.
Five other operable units are under consideration for remedial action at Eielson AFB:
OU1 Petroleum, Oil, and Lubricant (POL) Contamination
OU2 POL Contamination
OU3 Solvent Contamination
OU4 Land Disposal of Fuel Tank Sludge, Drums, and Asphalt
OUS Land Fills
An interim action at OU1B was initiated in June 1992 to address "floating product." RODs
are in progress for OU1 and OU2. RI/FS reports are in progress for OUS, OU4, and OUS.
Thirty-one source areas not included in any OU are being evaluated through the Source
Evaluation process. Of these, 21 are proposed for no further action, and 10 are still
undergoing evaluation.
A "sitewide" RI/FS and ROD will also be completed to address cumulative risks (including
ecological risks) for all source areas and to allow for monitoring of areas that have been
investigated and recommended for no further action.
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5. SUMMARY OF SITE CHARACTERISTICS
The area of OU6 is a southwest-facing hillside slope that extends from the ski hill ridgetop to
somewhat swampy, relatively flat lowlands. The geologic units encountered at the site
include fractured bedrock, weathered bedrock, a layer of soil (loess) mantling the top of the
bedrock, and, at the bottom of the hill, alluvial sediments. The layers of alluvial sediments
lie unconformably on the bedrock and extend southwestward at the bottom of the hill; this
alluvium is part of the Tanana River plain, which contains the major groundwater aquifer at
Eielson AFB. It contains discontinuous permafrost in the area of the ski hill.
Petroleum contaminants were released from some of the eight 50,000-gallon above-ground
fuel storage tanks and associated piping that were formerly located on the ridgetop along
B Battery Road. Fuel contamination has since been found in the soil at the top of the ridge
and in the groundwater in the bedrock near the base of the slope. Studies of the ski hill have
investigated the distribution of the fuel contamination in the environmental media. Samples
of soil, weathered bedrock, surface sediment, and groundwater have been collected and
analyzed.
The data from studies prior to 1993 were not validated, so those data were reviewed and
analyzed and used to select locations for the 1993 RJ/FS field work, the analytical results of
which are compiled in the RI for OU6 (USAF 1994a).
5.1 GEOLOGY AND HYDROGEOLOGY
The geology of the site was investigated by logging borings drilled in soil and bedrock, by
surface geology investigations, and by interpretation of geophysical survey results. Numerous
soil borings were located at the top of the ridge near the bases of the former tanks. These
borings intersected a layer of soil composed mostly of loess and silly soil that is between
0 and 20 ft thick. A seismic refraction survey was completed to investigate the soil-bedrock
interface in the area of the former tanks and also the distribution of the permafrost in the
alluvial sediments at the bottom of the hill. The results of the geophysical survey at the top
of the hill confirmed that the soil was a thin layer, and that the bedrock-soil interface surface
was of low relief. The soil unit at the top of the hill is not water-bearing.
The partly exposed bedrock unit at OU6 is known regionally as the Birch Creek Schist, but
locally the rock types are quartz-biotite schists, highly weathered near the surface, with
graphite and quartz layers at depth. The depth to water in the bedrock varies from
approximately 40 ft below the surface in the area of the ski lodge to approximately 270 ft
below the surface at the top of the ridge. A total of nine groundwater monitoring wells
(38M01-38M07, 38M16, 38M17) and three groundwater supply wells (SLW, 8621, and 8626)
have been installed at the site with auger or air rotary drilling equipment. All but three of
these wells (38M07, 38M16, 38M17) were screened in the bedrock.
Water levels were observed to rise rapidly after first water during drilling of the wells in the
bedrock. This suggests that confined conditions may exist in the fractured bedrock aquifer.
No geologic evidence of a confining layer was observed in the logging of the borings, and
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permafrost is not generally present in bedrock in an area where permafrost is discontinuous in
the alluvium. The interpretation of the bedrock aquifer as either confined or unconfmed is
uncertain. One slug test was conducted on well 38M03; the results indicated that the aquifer
has a hydraulic conductivity of approximately 1.2 ft/day in the area of the well.
Measurements made in July 1993 of the potentiometric surface in the wells at OU6 indicate
that the hydraulic gradient in the schist is toward the south-southwest, at values between
0.021 and 0.25. Figure 4 shows a hydrogeologic cross-section of the ridge through tank
sub-base 8 and the ski lodge.
The hydrologic information about the bedrock aquifer is subject to the uncertainties common
to most bedrock aquifer systems. It is possible that the flow of liquids in the unsaturated
portion and also in the saturated portion of the bedrock is controlled by a relatively small
number of hydrologically significant heterogeneities, i.e., fractures that are much more
permeable than the bedrock blocks between these fractures. The location, orientation, and
connectedness of the significant fractures cannot be determined using conventional field
methods or a reasonable number of investigative or monitoring points. The flow of the fuel
contaminants in the unsaturated zone, of the contaminated groundwater in the saturated zone,
and of the uncontaminated water in the saturated zone are all subject to considerable
uncertainty as to the direction and magnitude of downgradient flow. The locations and
magnitudes of the maximum concentrations of the contaminants are also subject to
uncertainties.
The alluvial sediments at the base of the ski hill area are part of an extensive sedimentary
unit that makes up the level portion of the Tanana valley. The sediments are primarily sands
and gravels, and they are 200-300 ft thick at Eielson AFB. The sediments lie unconformably
on the bedrock. The sediments are saturated below approximately 8 ft depth; the alluvial
aquifer is highly productive and an important water source in the Tanana valley.
A total of seven water wells (8626, 38M02, 38M03, 38M06, 38M07, 38M16, 38M17) were
drilled into or through the alluvial aquifer at OU6, but only three of these (38M07, 38M16,
and 38M17) were screened in the alluvium itself. The alluvial aquifer may be locally
confined by permafrost, as evidenced by frozen sediments encountered during drilling and an
immediate and considerable rise in water levels in the wells after first water was encountered.
The results of the geophysical survey in the alluvium indicated that the permafrost was too
discontinuous to permit interpretation of the geophysical data.
The direction of groundwater flow in the alluvial aquifer is generally to the north-northwest
(the direction of the Tanana River) in the developed portion of the base, where elevation
control is good. In that location the aquifer is influenced locally by Garrison Slough, by
Hardfill Lake, probably by French Creek, and by pumping of the base water supply wells.
Groundwater, the only source of potable water at Eielson AFB, is supplied by three large-
capacity wells located near the power plant at the center of the base, approximately 3 miles
from OU6 (see Figure 2). The supply wells are of 1,000-2,000 gallon per minute capacity.
The base water supply wells are completed at depths averaging approximately 100 ft. At
present (1994), water from those wells furnishes the domestic water supply at the OU6 site.
11206.44 13
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A
Location of cross—section A-A'
PERMAFROST DEPTH
WITH SOME DISCONTINUOUS
MARGINAL PERMAFROST
(SEE NOTE)
A'
Scale: feet
Figure 4. Hydrogeologic cross-section, OU6,
Eielson Air Force Base, Alaska.
Drawn'
Reviewodi
Rev.l:
Date;
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Date?;
Final: ^^^ate:
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In addition there are seven wells designated to provide water to fight fires on the base, and
these are designed for emergency use only. They are plumbed to the water supply system.
5.2 NATURE AND EXTENT OF CONTAMINATION
The environmental media sampled in 1993 for the RI were soil, sediment, and groundwater.
Soil and groundwater were also sampled in the previous investigations, and groundwater was
routinely sampled in the water supply wells at the site when they were in use. The
contaminants investigated in 1993 were the fuel compounds benzene, toluene, ethylbenzene,
and xylene (BTEX); total petroleum hydrocarbons (TPH); total diesel hydrocarbons (DRO);
total gasoline hydrocarbons (GRO); and the metals cadmium, chromium, and lead. Other
metals were found in the soil at concentrations typical of those occurring naturally at the
base, and they are not considered to be present as contaminants. The results of the 1993 and
earlier sampling effort arc summarized below.
Soil
Soil samples were collected from soil borings (38SB01-38SB18, Figure 5) and in the borings
for groundwater (38M01-38M07) and vadose-zone monitoring wells (38M08-38M17). The
borings for wells M01-M07 (see Figure 5), carried out in 1988, were drilled just downslope
of the tank sub-bases (M04, M05), at midslope above the ski lodge (M01), and at the base of
the hill (M02, M03). Wells 38M06 and 38M07 were drilled in the lowland alluvium in the
assumed downgradient direction from the ski lodge well. Soil samples were taken from these
wells at the following depths (generally the bottom of the boring):
38M01 38M02 38M03 38M03 38M04 38M05 38M06 38M07
Depth (ft) 171 43 47 72 50 114
TPH(mg/kg) 27 ND 12.8 ND 13.6 ND
The samples were analyzed only for TPH. The samples from M06 or M07, the wells in the
alluvial plain, were not analyzed offsite.
The concentrations of organic analytes detected in the remaining samples are shown in
Table 1. (In 1993 two groundwater monitoring wells were drilled at the foot of the hill,
38M16 to the west, below tank sub-base 1, and M17 on a possible pathway below
sub-bases 1 and 2.) Borings were concentrated at two locations: near the tank sub-bases and,
to a lesser extent, downslope along potential migration pathways, (e.g., north of sub-base 1,
southwest of sub-bases 3 and 5). Soil samples were collected at several depths from each
boring.
Fuel compounds were detected in the soils near the tank sub-bases. The highest
concentrations of Total Petroleum Hydrocarbons were found in 38M10, 38M13, and 38M14,
below tank sub-bases 1 and 2 (see Figure 5). The highest concentrations of benzene, toluene,
ethylbenzene, and xylenes were found in wells 38M09, 38M10, and 38M11. The highest
level of contamination in the areas sampled to date is found near tank sub-base 1, at the
11206.44 15
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Location of
cross-section B-B'
38M10
J3BSB17-
230
IgS
oumc ICALC H rtn
850
\
V
MOTES:
AIL CONCENTRATIONS IN mj/Vj
SCWRAl SOIL BORINGS OR MONITOR
WCLIS BOHINCS LAY ON EITHER SOC OH IHC PRCTItC
LINE AND ARC NOTED AND ILLUSTRATED IN Tilt FIGURE
AS CROJCCKO. CHANCE INUTHOLOCV IS ILUSTRATED
IN HCURC FOR PROJCC
SPLIT SPOON SAMPLES
INTERVALS ANO_ SAMPLE
NGS.
AT 9 FOOT
;EO FOR T(
PETHOUUU HYDROCARBONS. SAUPLL
INIERVAL ILLUSTRATED ON MS CROSS-SECTION HAD THE
HIGHEST PIU READING AND WAS SENT TO THE FIELD AND
Off51 IE LABORATORY FOR ANALYSIS.
B
S«ty So** (Lot** including
Granular r«l>
Ivch Crttk $ch(«t i*t*nt>
3BMI2 VIP*: r»?z**vrtt °f s°*
I-
TPH Concrntratlon (nQ/l«Q>
Crologic Contact* Inftfrfd tron
, Sfllnlc R»rr«ction Survey «nd
So* larngt
Tank Sub-bair and Nunbrr
r 890
880
- 870
- 860
- 850
- 840
>- 830
r 820
- 810
- 800
.-
<
>
300 100 0
•<00 800
HOmZONIAL SCALE IN FECI
Figure 5. Vertical extent of petroleum constituents, OU6.
Eielson Air Force Base, Alaska
Drawm
Reviewed;
Rev.li
Date:
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Date;
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TABLE 1 CONCENTRATIONS OF ORGANIC ANALYTES IN SOIL
SAMPLES, OU6, EDELSON AFB, 1988-1993"
Well Sample
Boring Depth (ft)
38M08 10.0-11.5
30.0-30.7
38M09 15.0-17.0
15.0-17.0
45.0-47.0
38M10 30.031.5
40.0-41.5
38M11 5.0-6.5
25.0-26.4
38M12 100-11.0
15.0-15.6
38M13 5.0-6.5
25.0-26.0
38M14 25.0-25.5
45.CM6.5
38M15 10.0-11.5
25.0-27.0
25.0-27.0
38M16 0.0-1.5
10.0-11.5
10.0-1 1.5
14.5-16.0
a. 38M08-38M17 - October 1989;
Concentration (mg/kg)
Benzene
ND
ND
35.6
NS
ND
27.5
ND
25.2
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
NS
ND
ND
ND
Ethylbenzene
1.7
ND
53
NS
ND
91
ND
59
ND
ND
ND
ND
ND
5.6
ND
ND
ND
ND
NS
ND
ND
ND
Toluene Xylenes
1.6 13.5
ND
140
NS
ND
180
ND
620
ND
ND
ND
3.5
ND
9.7
ND
ND
ND
ND
NS
ND
0.0008
0.0006
ND
400
NS
ND
752
ND
440
ND
ND
18.6
16.1
14.3
31.5
8.68
ND
ND
ND
NS
ND
0.0011
ND
DRO GRO TPH
21.9
ND
- - 408
- 144
_ _ ND
1,330
- - ND
133
- - ND
875
406
1,470
45.6
1240
220
ND
- - ND
- ND
31 - 35
35 ND 57
12 ND 14
14 ND 13
38SB17, 38SB18 - July 1993.
Note: DRO - Diesel-range organics; GRO - gasoline-range
ND - Below method or sample detection limit; NS
organics;
- Sample
TPH - total
not analyze*
petroleum hydrocarbons.
i for parameter.
11206.44
17
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TABLE 1 (continued)
Well
Borinc
38M17
38SB17
38SB18
Sample
Depth (ft)
0.0-1.5
12.5-14.0
12.5-14.0
17.5-19.0
0.0-1.5
15.0-16.5
15.0-16.5
50.0-51.5
60.0-61.5
0.0-1.5
0.0-1.5
16.0-17.5
30.0-31.5
Concentration (mg/kg)
Benzene Ethylbenzene Toluene
ND
ND
ND
ND
ND
0.0006
0.0013
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
0.0008
o.ooii
0.0010
ND
ND
ND
ND
ND
ND
Xvlenes
ND
ND
ND
0.0012
0.0011
0.0025
0.10
0.0013
ND
ND
ND
ND
ND
PRO
13
ND
16
26
ND
ND
6.9
ND
ND
23
12
ND
11
GRO
ND
ND
ND
ND
ND
1.4
1.8
ND
ND
ND
ND
ND
ND
TPH
8.8
ND
6.7
6.4
ND
ND
ND
ND
ND
ND
6.4
NS
ND
11206.44
18
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northwest end of the line of tank sub-bases, and near sub-base 7, near the southeast end of the
line of sub-bases. The data suggest that the petroleum contaminants migrated through the soil
in a dominantly vertical direction.
Metal concentrations in the soil samples were in the ranges of background concentrations for
the metals investigated. For example, of 11 lead samples, 10 were in the range reported for
background levels in fluvial soils at Eielson AFB, which averaged 10 mg/kg, and the 11th, at
35 mg/kg, was found in competent schist. The same was true for chromium: of 11 samples,
the only one outside of the background range (average 26 mg/kg) was found in competent
schist in 38SB18.
Sediments
Six sediment samples were collected from the materials underlying standing water in the
wetlands at the foot of the ridge (Figure 6). The sampling points were located near "inflow"
points, where it was estimated that subsurface water from the ridge might be rising to the
surface, and where sediments were thick enough to permit collection of a sample.
The results of the sediment sample analyses are shown in Table 2. The fuel constituents
tested for were detected in varying numbers of the samples, at concentrations below the level
of regulatory concern. The various samples contained low concentrations of benzene, toluene,
ethylbenzene, xylenes, diesel-range hydrocarbons, gasoline-range hydrocarbons, and TPH.
For example, benzene was found in two of the six samples, at concentrations of 0.01 and
0.013 mg/kg; TPH was found in all six, at 13-120 mg/kg. Because the samples were taken
near the road to the ski lodge, a local vehicular source cannot be excluded, and the ultimate
source of the constituents found in the sediments cannot be identified with certainty.
Lead was found in all six samples, at 6.4-16 mg/kg; chromium, at 22-32 mg/kg. Both ranges
are within the background level ranges reported for Eielson AFB.
Groundwater
Groundwater samples were collected from the water supply wells (see Figure 6) and the
monitoring wells and analyzed for organic and inorganic constituents. Four of the wells are
periodically or permanently inaccessible, because of ice or equipment in the well casing
(8621, 38M07, and 38M08) or damage to the well head (8626).
Table 3 summarizes the organic contaminants detected in groundwater samples from the wells
through 1993. Benzene was found at levels greater than 5 ng/L in wells SLW, 8626, and
38M01. It was detected at concentrations less than 5 ng/L in wells 38M04 and 38M05. The
greatest number and highest levels of all contaminants were found in samples from 38M01.
The Benzene contamination in 38M01 decreased and then increased in the period 1988-1993.
However, the concentrations of other BTEX components have declined. This may be
attributed to natural degradation and attenuation processes in which benzene is attenuated
more slowly than the other BTEX components. The benzene concentration in 38M01 varied
from 868 pg/L in 1988 and 510 \igfL in 11989 to 910 ng/L in 1993.
11206.44 19
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Figure 6. Sampling locations, OU6, Eielson Air Force Base, Alaska.
Drown:
Reviewed:
Rev.1:
Final:
Dole:
Dale:
Date:
.Dote:
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TABLE 2 CONCENTRATIONS OF ORGANIC ANALYTES IN
SEDIMENT SAMPLES, OU6, EIELSON AFB,
JULY 1993
Concentration (mg/kg)
Sample
Number
38SD01
38SD02
38SD03
38SD03-01*
38SD04
38SD05
38SD06
Benzene
ND
0.013
ND
ND
0.0010
ND
ND
Ethvlbenzene
ND
0.013
ND
ND
0.0008
ND
ND
Toluene
0.0013
0.069
0.0007
ND
0.0045
0.0015
ND
Xylenes
0.0020
0.076
ND
ND
0.0046
ND
ND
PRO
27
ND
ND
ND
28
28
11
GRO
0.29
0.66
ND
ND
ND
ND
ND
TPH
78
18
13
23
110
120
40
Note: DRO - Diesel-range organics; GRO - gasoline-range organics; TPH -total
petroleum hydrocarbons.
ND - Below method or sample detection limit.
* Duplicate sample.
11206.44
21
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TABLE 3 CONCENTRATIONS OF ORGANIC ANALYTES IN
GROUNDWATER, OU6, EIELSON AFB, 1988-1993
Concentrations (ue/L)
WeU
38M01
38M02
38M03
38M04
38M05
38M06
Sampling
Session8
1988
1989
1992
1993
1988
1989
1992
1993
1988
1989
1992
1993
1988
1989
1992
1993
1988
1989
1992
1993
1988
1989
1992
Benzene
868
510
590.0
910
<0.15
<0.20
<2.0
ND
<0.15
<0.20
<2.0
ND
3.77
<0.20
<2.0
ND
0.19
0.43
<2.0
0.54
„
<0.20
Toluene
1,400
96.6
5.9
27
0.84
<0.30
<2.0
ND
<0.25
<0.30
<2.0
ND
2.15
2.02
<2.0
ND
0.43
1.10
<2.0
ND
v«
<0.30
Ethyl-
benzene
318
21.3
4.4
ND
<0.46
<0.50
<2.0
ND
<0.46
ND
ND
ND
<0.46
<0.50
<2.0
ND
0.82
<0.50
<2.0
ND
•»«
<0.50
Xylenes
1,890
230
5.0
50
<0.85
<0.40
<5.0
ND
<0.85
<0.40
<5.0
ND
<0.85
<0.40
<5.0
ND
<0.85
<0.40
<5.0
ND
_.
<0.40
TPH
10,700
1,500
. 500
100
<100
100
<100
500
400
1,500
—
a. 1988: IRP Phase II, Stage 3; 1989: IRP Phase II, Stage 4; 1992; 1993: RJ/FS.
22
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TABLE 3 (continued)
Concentrations Cug/L)
Well
38M07
8626
Sampling
Session3
1988
1989
1992
1993
1988
1989
1992
38M16 1993
38M17 1993
38SLW 1993
Benzene
<0.20
ND
148
18.8
ND
ND
140
Toluene
14.7
0.0012
<0.25
3.00
ND
ND
ND
Ethyl-
benzene
<0.50
ND
<0.46
<0.50
ND
ND
ND
Xvlenes TPH
<0.40
ND
<0.85
<0.40
0.77
ND
ND
1,130
ND
100
100
100
11206.44
23
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Benzene was first detected in the ski lodge well in a water sample collected on 13 August
1986, at a concentration of 145 ug/L. The well was resampled on 30 August, and the
presence of benzene was confirmed, at 115 ug/L. The well was sampled quarterly from
July 1987 to October 1990; concentrations of benzene ranged from below the detection limit
to 33 ug/L. A carbon filter was installed at the wellhead at an unknown date: the
December 1988 value was annotated "no treatment" and had a concentration of 20 ug/L. It is
not known if samples collected between July 1987 and October 1990 were collected upstream
or downstream of the carbon filter. The next sample, collected in 1993, contained benzene at
a concentration of 140 ug/L.
No fuel contaminants other than TPH (Method 418.1) have been detected in samples from
wells 38M03, 38M06, and 38M17.
11206.44 24
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6. SUMMARY OF SITE RISKS
This chapter summarizes the Baseline Risk Assessment (RA) for OU6 (USAF 1994b), which
forms the basis for taking action and indicates the exposure pathways that need to be
addressed by the remedial action. It indicates what risks could exist if no action were taken
at the site. Environmental risks may be categorized as ecological risks and human health
risks.
6.1 HUMAN HEALTH RISKS
A human health risk assessment begins with identification of COC (chemicals of concern) at
the site and the exposure pathways for those chemicals to receptors (human beings). To
estimate the risk to receptors, measures of the toxicity of the COC as delivered by the
particular exposure pathways are combined mathematically with conservative estimates of the
concentrations of COC as delivered and the duration of exposure. The MEPAS (Multimedia
Environmental Pollutant Assessment System) integrative model was used. Its main
components are an exposure assessment (Section 6.1.2) and a toxicity assessment (6.1.3).
6.1.1 Identification of Contaminants of Concern
The contaminants of concern for the OU6 site were identified using the screening method
suggested in the supplemental guidance for Superfund Risk Assessments in EPA Region 10
(EPA 1991). This method, called the "risk-based screening approach," compares the highest
concentration of each chemical detected at a site to a risk-based screening concentration.
Screening concentrations were chosen, using a residential exposure scenario, for the ingestion
of soils and sediments and for the ingestion of water and inhalation of its vapors during
showering. Possible COC were listed, on the basis of the results from the analysis of about
250 soil, water, soil vapor, air, and groundwater samples collected at the site in the period
1986-1993, and the highest 1993 concentration for each contaminant for each medium
sampled was compared to concentrations estimated to pose a risk to receptors.
A chemical was eliminated if the maximum concentration was less than the cancer risk
concentration of 1E-6 (one in one million) in water and less than 1E-7 in soil (the threshold
was lowered 10-fold to take into account the multiple exposure pathways for soil-borne
contaminants). For non-cancer risks, the corresponding values for both soil and water were a
total H/Q ratio (i.e., the sum of all ratios of the concentration in the medium to the highest
concentration estimated not to cause a noticeable effect with chronic exposure, summed
across all exposure paths for the chemical) of 0.1. Chemicals were also eliminated if their
presence could not be attributed to the source of contamination.
Table 4 presents the resulting list of chemicals of concern for the OU6 site and the
concentrations of those chemicals that served as input to the risk assessment calculations.
The analytical data used, collected during the 1993 field season, are listed in Appendix E of
the RI (USAF 1994a). The concentration listed for each chemical of concern is either the
95 percent upper confidence limit on the mean concentration for all samples (95 percent
UCL) or the highest measured value, if it is less than the 95 percent UCL or if the data did
11206.44 25
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TABLE 4 CONCENTRATIONS* OF CHEMICALS OF CONCERN USED
FOR RISK ASSESSMENT AT OU6, EIELSON AFB
Chemical of Concern
Benzene
Ethylbenzene
Toluene
Xylenes (total)
Total Petroleum Hydrocarbons
Diesel Hydrocarbons
Gasoline Hydrocarbons
Surface Soil, Sediment
(me/kg)
Highest
0.0013
0.0013
0.0069
0.0076
120
86
0.66
95%UCL
0.0004
0.0002
0.0020
0.0009
70
57
0.24
Groundwater
(ue/U
Highest
910
0
27
50
1,500
1,350
3,800
95%UCL
260
ND
8
15
970
890
1,100
a. Highest concentration is highest single concentration detected in sampling at OU6
between 1988 and 1993 for soils; highest in 1993 for groundwater. 95% UCL
concentration is 95th percentile value of all measured samples; values below the
detection limit were set at the detection limit.
Note: 95% UCL was used for RME (Reasonable Maximum Exposure) concentration in
risk assessment calculations unless the distribution of values was not normal or the
highest value measured was less than the 95% UCL.
11206.44
26
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not exhibit a normal distribution. All water analyses were used, along with all soil and
sediment analyses that met or exceeded EPA Level HI.
There are no EPA toxicity data for two of the principal contaminants at site OU6: TPH and
lead. Although lead concentrations were generally at soil background levels for Eielson AFB,
the presence of a higher concentration in the schist of the ski hill led to its inclusion in the
risk assessment. Accordingly, these compounds were not included in the primary risk
calculations. An analysis for lead risk to children was calculated separately, and EPA
Region 10 guidance (EPA 1991) was used for TPH in groundwater.
6.1.2 Exposure Assessment
An exposure pathway consists of a source and release mechanism, an environmental transport
medium, a point of exposure, and a human receptor and mechanism of exposure. The OU6
site is in a relatively undeveloped area and is used at present .for recreation and for the Arctic
Survival Training School, and thus exposure to chemicals is temporary and intermittent.
Water used on the site comes from uncontaminated wells elsewhere on the base.
The points of exposure for soil are sediment accumulations at the foot of the slope and
surface soil near the former tank sites. Water, assuming the use of groundwater from the site,
is from wells near the present monitoring wells. The 95 percent UCL of the chemicals of
concern for these source locations were entered into the risk assessment models.
The exposure assessment was made for four land-use scenarios. In two of them, groundwater
from the site itself is used: "future use," by residents of housing at the site and by military
personnel engaged in industrial activity. These scenarios assume ingestion, inhalation of
vapors (e.g., in showers), and dermal contact with contaminated water; they also involve
incidental ingestion of and dermal contact with surface soil from the site. A third scenario is
"current" industrial use of the site by military personnel, with soil but not groundwater
exposure, and the fourth is recreational use (which was defined as 65 days per year of
camping at the site), also involving soil but not water exposure. All of these scenarios are
hypothetical, to a greater or lesser degree, and are intended to define conservative (high)
exposure to site contaminants. Both of the industrial scenarios and the recreational scenario
assume use of the site by adults; the residential scenario, use by adults and children.
Table 5 lists the exposure pathways that were considered complete for each land-use scenario.
The point exposure concentrations for the contaminants are included in Table 4.
The degree of exposure depends on the duration and frequency of contact, the size and age of
the receptor, and the conditions of exposure. The exposure factors used for the four land-use
scenarios generally follow EPA Region 10 guidance (EPA 1991). Exposure factors for both
"Average Exposure" and the more conservative "Reasonable Maximum Exposure" cases were
used. The factors used are listed in Tables B.I through B.13 in Appendix B of the RA
(USAF 1994b). There was some divergence from the standard default exposure factors: the
exposure duration for soils and sediments was adjusted to take into account the long periods
of snow cover in the subarctic climate at Eielson AFB. The values used (130 days per year
for industrial use and 180 days for residential use) were based on the number of days in
11206.44 27
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TABLE 5 EXPOSURE PATHWAYS FOR CHEMICALS OF CONCERN
AT OU6, EIELSON AFB, ALASKA
Scenario
Pathway
1. Current Camp Workers and Recreators
Ingestion of soil or sediment
Dermal contact with soil or sediment
2. Current Military Personnel
Ingestion of soil or sediment
Dermal contact with soil or sediment
3. Future Military Personnel
Ingestion of soil or sediment
Dermal contact with soil or sediment
Inhalation of VOCs released from groundwater
Dermal contact with groundwater
4. Future Residents
Ingestion of soil or sediment
Dermal contact with soil or sediment
Inhalation of VOCs released from groundwater
Ingestion of groundwater
Dermal contact with groundwater
11206.44
28
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Fairbanks without snow cover. The mean number of days without snow cover at Fairbanks
is 146; 180 days is presented as a reasonable maximum value. The industrial exposure
duration reflects a 5-day work week. These values were initially advanced in Appendix A of
the Management Plan for Operable Units 3, 4, and 5 of Eielson AFB (Battelle 1992). The
effect of adjustment is discussed in the section on uncertainties (Section 6.1.5).
The input concentrations for groundwater BTEX for future scenarios were set at the
95 percent UCL of the concentrations measured in the monitoring wells at the site.
Assumptions used in the exposure assessment modeling component of the MEPAS program
include the following:
• Each component in the BTEX group can be modeled as a separate and independent
constituent.
• There will not be any changes in concentrations with time. (No modeling of the
effect of the passage of time on concentration was included in the risk assessment.)
6.13 Toxicity Assessment
The values and references for all toxicity data used in the risk assessment are given in
Table 9.1 of the Risk Assessment. Tables 6 and 7 are samples of the toxicity data for the
chemicals of concern. Toxicity data are expressed as slope factors (SFs) for carcinogens
(Table 6) and as reference dosages (RfDs) for noncarcinogenic toxic chemicals (Table 7).
SFs have been developed for Carcinogenic Assessment Groups by EPA for use in estimating
excess lifetime cancer risks associated with exposure to potentially carcinogenic chemicals of
concern. SFs, which are expressed in units of (mg/kg-day)-l, are multiplied by the estimated
intake of a potential carcinogen, in mg/kg-day, to provide an upper-bound estimate of the
excess lifetime cancer risk associated with exposure at that intake level. The term "upper
bound" reflects the conservative estimate of the risks calculated from the SF. Use of this
approach makes underestimation of the actual cancer risk highly unlikely. SFs are derived
from the results of human epidemiological studies or chronic animal bioassays to which
animal-to-human extrapolation and uncertainty factors have been applied (e.g., to take into
account the use of animal data to predict effects on humans).
RfDs (reference doses) have been developed by EPA for oral exposure to toxic chemicals to
indicate the potential for adverse health effects from exposure to contaminants exhibiting
noncarcinogenic effects. The corresponding measure for chemicals that are inhaled is the RfC
(reference concentration). RfDs, which are expressed in units of mg/kg-day, are estimates of
lifetime daily exposure levels for humans, including sensitive individuals, that will not result
in appreciable adverse effects on health. Estimated intakes of chemicals of concern from
environmental media (e.g., the amount ingested from contaminated drinking water) can be
compared to the RfD. RfDs are derived from human epidemiological studies or animal
studies to which uncertainty factors have been applied.
11206.44 29
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TABLE 6 REFERENCE DOSES AND CRITICAL EFFECTS OF THE CHEMICALS
OF CONCERN AT OU6, EEELSON AFB, ALASKA
Chemical
Reference Dose
(mg/kg-d)
Level of
Confidence3
Critical Effect
Organics
Benzene
Ethylbenzene
Toluene
Xylenes
UR
1.00-01
2.00E-01
2.00E+00
—
Low
Med
Med
Petroleum
Hydrocarbons
Diesel
Hydrocarbons
Gasoline
Hydrocarbons
8.00E-03*
2.00E-01*
Low
Low
Liver and kidney toxicity
in rats
Changes in liver and
kidney weights in rats
Hyperactivity, decreased
body weight and
increased mortality in
male rats
Fatty changes in the liver
of mice
Decrease in body weight
in rats and mice
Inorganics
Cadmium
Chromium
Lead
5.00E-04
5.00-03
NR
High
Low
Significant proteinuria in
humans
No observed effects in
rats
a. USEPA - assigned level of confidence in toxicity value. Med = medium.
Note: UR = under review, NR = not reported. An asterisk (*) indicates that values were
taken from USEPA 1992d. A dash ("-") indicates that this item is not applicable, or
that there is no entry in either IRIS or HEAST.
11206.44
30
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TABLE 7 ORAL EXPOSURE SLOPE FACTORS AND TARGET ORGANS
OF THE CHEMICALS OF CONCERN AT OU6, EIELSON AFB,
ALASKA
Chemical
Organics
Benzene
CAGa
A
Slope Factor
(mg/kg-d)-1
2.90E-02
Target Organ
(Tumor Type)
Blood (leukemia):
Ethylbenzene
Toluene
Xylenes
Petroleum Hydrocarbons
Diesel Hydrocarbons
Gasoline Hydrocarbons
D
D
D
U
D
C
1JOE-03*
humans
Liver (carcinoma/
adenoma): mice
Inorganics
Cadmium
Chromium
Lead
Bl
A
B2
Significant proteinuria
in humans
No observed effects in
rats
a. A CAG = EPA Carcinogen Assessment Group (see text).
Note: SF = slope factor, U = Undetermined. An asterisk (*) indicates that values were
taken from USEPA 1992d. A dash ("-") indicates that this item is not applicable, or
that there is no entry in either IRIS or HEAST.
11206.44
31
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There are no EPA toxicity classifications for two of the principal contaminants measured at
OU6, TPH and lead, so these compounds were not included in the primary risk calculations.
The relatively high concentrations of TPH at OU6 are believed to have resulted from past
spills and leaks of fuel. Because of the inherent variability in the degradation of fuels in soil,
no fixed toxicity value can be assigned. However, the sample with the highest TPH
concentration at each site was also analyzed for volatile and semivolatile organic compounds,
for which SFs and RfDs are established. Lead concentrations in groundwater and soils were
compared to the EPA guidance value for soils (500 mg/kg) and the groundwater MCL
(Maximum Contaminant Level) of 15 ng/L. The highest total concentrations of dissolved lead
in groundwater at OU6 (6 ^ig/L) did not exceed the MCL.
6.1.4 Risk Characterization
The exposure point concentrations listed in Appendix F of the RA for the site were used with
the toxicity data in Table 6 to calculate the risks for carcinogens and noncarcinogens at the
OU6 site. For carcinogens, risks were estimated as the incremental probability of an
individual developing cancer over a lifetime as a result of exposure to the carcinogen for the
stipulated duration and frequency of exposure. Excess lifetime cancer risk was calculated
with the following equation:
Risk = GDI x SF
where
Risk = a probability (e.g., 2E-5 [0.00002]) of an individual developing cancer
GDI = chronic daily intake averaged over 70 years (mg/kg-day)
SF = slope factor (mg/kg-day)-1
The probabilities of risk are generally expressed in scientific notation (e.g., IxlO"6, or 1E-6).
An excess lifetime cancer risk of 1E-6 indicates that, as a reasonable maximum estimate, an
individual has a one in one million chance of developing cancer over a 70-year lifetime as a
result of site-related exposure to the carcinogen under the specific exposure conditions at a
site.
For noncarcinogens, the potential effects were evaluated by comparing the exposure level over
a specified time period (e.g., 9 years, the average term of residence in a house) with a
reference dose derived for that exposure period. The ratio of these two values is called a
hazard quotient (HQ), and it represents in some sense the chance that the receptor will suffer
symptoms of the toxicity. By adding the HQs for all contaminants of concern within a
medium or across all media to which a given population may be exposed, the Hazard Index
(HI) can be generated.
The HQ (for noncarcinogens) is calculated as follows:
HQ = CDI/RfD
where
11206.44 32
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GDI = chronic daily intake
RfD = reference dose
GDI and RfD are expressed in the same units and represent the same exposure period
(i.e., chronic, subcnronic, or short-term).
Risk calculations were made for each of the four land-use scenarios, all associated exposure
pathways, and for two different exposure cases—"average exposure" and "reasonable
maximum exposure."
Table 8 summarizes the risk calculation results for OU6. Each table lists the cancer risk and
the HI for each exposure pathway separately. The values presented are for the RME
(reasonable maximum exposure) case only. A total cancer risk value and a total HI are
presented that add all of the exposure pathway risks together.
Metals other than cadmium, chromium, and lead were not considered to result from activities
at the base: except for these three, there are no known human-caused sources of metals at
OU6, so other metals detected in previous investigations were removed from the list of COG.
The Fairbanks area of Alaska is known to have elevated concentrations of a number of metals
in the groundwater, particularly iron, manganese, and arsenic, and many of these metals
exceed risk-based screening concentrations at uncontaminated sites on Eielson AFB.
Table 8 indicates that the predicted excess cancer mortality associated with the future
residential land-use scenario constitutes an unacceptable risk at OU6 and that the HI is greater
than 1. The major exposure pathway of concern for the site under the local-drinking-water
land-use scenarios is the inhalation of the vapors from contaminated groundwater.
The chief chemical of concern in groundwater at OU6 is benzene, although diesel
hydrocarbons presented a hazard index greater than 1.
Ingestion of and dermal contact with contaminated surface soils and shallow sediments did
not present an excess cancer risk greater than 1 x 10-6 (the highest combined value was
about 2E-9), and the Hazard Index was well under 1, even in the future residential scenario.
6.1.5 Uncertainties in the Risk Assessment
Health risk assessment methodology has inherent uncertainty associated with the degree to
which the calculated risk estimates represent the actual risk. The effects of the assumptions
and the uncertainty factors may not be known. Usually, the effect is difficult to quantify
numerically, so the effect is discussed qualitatively. Some of the major assumptions and
uncertainty factors associated with the risk assessment are the following:
11206.44 33
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TABLE 8 TOTAL RECEPTOR RISK VALUES FOR CURRENT AND
FUTURE LAND USE, OPERABLE UNIT 6, EIELSON AFB,
ALASKA
Hazard Index
Carcinogenic Risk
Exposure Pathway
Current Camp Workers/Recreators
Ingestion of Soil/Sediment
Dermal Contact with Soil/Sediment
Total Receptor Risk
Current Military Personnel
Ingestion of Soil/Sediment
Dermal Contact with Soil/Sediment
Total Receptor Risk
Future Residents (Hypothetical)
Ingestion of Groundwater
Volatiles
Dermal Contact with Groundwater
Ingestion of Soil/Sediment
Dermal Contact with Soil/Sediment
Total Receptor Risk
Future Military Personnel (Hypothetical)
Ingestion of Groundwater
Volatiles
Dermal Contact with Groundwater
Ingestion of Soil/Sediment
Dermal Contact with Soil/Sediment
Total Receptor Risk
Average
3.0E-03
1.5E-02
2E-02
3.0E-03
3.0E-02
3E-02
1.9E+00
7.0E-03
4.0E-03
l.OE-02
4.2E-02
2E+00
1.2E+00
5.0E-03
4.0E-03
3.0E-03
3.0E-02
1E+00
RME1
3.0E-03
6.0E-02
7E-02
3.0E-03
1.3E-02
1E-Q1
3.4E+00
7.0E-03
7.0E-03
2.5E-02
1.9E-01
4E+00
1.2E400
5.0E-03
5.0E-03
3.0E-03
1.3E-01
1E+00
Average
1.7E-11
5.4E-11
7E-11
1.7E-11
1.1E-10
IE- 10
1.8E-05
7.8E-04
2.0E-06
4.8E-11
1.5E-10
8E-04
1.2E-05
3E-04
2.0E-08
1.7E-11
1.1E-10
7E-04
RME*
5.8E-11
7.9E-10
8E-10
4.8E-11
1.3E-09
1E-09
1.1E-04
3.3E-03
l.OE-05
1.6E-10
1.7E-09
4E-03
3.3E-05
3.0E-03
7.0E-06
4.8E-11
1.3E-09
2E-03
a. RME - Reasonable Maximum Exposure.
11206.44
34
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• The assessment used EPA Region 10 default exposure parameters for most
calculations. Some of these parameters are not realistic for a subarctic climate
(May overestimate risk.)
• Because the toxicity of TPH and lead has not been established neither was included
in the primary calculations in the risk assessment. (May underestimate risk.)
• Existing concentrations are assumed to be the concentrations or exposure source
terms in the future. No reduction through natural degradation and attenuation over
time is taken into account. (May overestimate risk.)
• No increase through additional contamination is assumed. (May underestimate
risk.)
• Potential degradation products of existing organic contaminants are not considered.
(May overestimate or underestimate risk.)
• The groundwater detection limits for some organic and inorganic contaminants are
higher than the risk-based screen concentrations. (May underestimate risk.)
• Contaminant concentrations in groundwater may be lower than the maximum
concentrations because of the limited number of sample points in the permafrost
and fractured bedrock. (May underestimate risk.)
6.2 ECOLOGICAL RISKS
The contaminants of concern at the OU6 site, benzene, toluene, ethylbenzene, xylenes, and
lead, were found in the shallow and deep soil on the ridge beneath the locations of the former
storage tanks and, to a certain extent, at the base of the ridge on the western side.
In planning the ecological risk assessment, it was concluded that since volatiles do not
bioaccumulate, but lead may, depending on the complexing form, lead would be studied in
the diet of various animals at the site.
Inhalation exposure of reference mammals and birds to volatiles (BTEX) from soil and
ingestion exposure of herbivores and carnivores to lead were estimated. The endpoint was
taken to be the lowest observable effect levels (LOEL) and concentrations (LOEC), for
ingestion and inhalation, respectively. Because most toxicity work has been done on acute
effects in domestic animals, large extrapolations with considerable uncertainties had to be
made.
6.2.1 Habitat Types and Potential Receptors
The major habitat types in the area included forest, lawn (mown) grasses, and a small lake.
Potential receptors included lemmings, voles, red squirrels, hares, beavers, porcupines, Canada
geese, grouse, and ptarmigan (terrestrial herbivores); moose and various species of ducks
(consumers of aquatic vegetation); and northern goshawk, red tailed hawk, great horned owl,
and coyote (carnivores).
11206.44 35
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Representative local receptors (those expected to remain in the area through a lifetime) were
chosen: grouse and voles for inhalation and ingestion of volatiles; and for ingestion of lead,
voles in lawn habitat and shrews and shrikes in forest habitat.
Because no lead or volatiles were detected in the local pond, and volatiles in groundwater
were found at depths of 30 ft or more below the ground surface, deeper than the root zones of
shrubs and trees, surface water and groundwater are not plausible pathways and were not
analyzed.
6.2.2 Sampling and Analysis of Diet Tissues
For evaluation of lead in the diet of reference herbivores and carnivores, plant and animal
tissue samples (grass and tree parts, aquatic invertebrates, squirrel) were collected and
analyzed for lead. Blank and spiked samples were analyzed to validate the samples.
6.23 Modeling Exposure
Inhalation Inhalation exposure was modeled for the maximally exposed terrestrial receptor,
grouse, using a conservative assumption about diffusion of volatiles. The resulting estimated
doses were as follows:
Benzene Ethylbenzene Toluene Xylenes
Dose (jig/kg[body weight]/day) 152 158 600 604
Ingestion Ingestion exposure was modeled with lead concentrations in the receptor's food,
measured at the site, weighted by the proportion of the food in the diet and the proportion of
food thought to come from the contaminated area, given the receptor's home range, taken
from the literature. The following receptor doses were estimated for lead:
Dose (ug [wet weight]/kg [body weight])
Ingestion LOEL and inhalation LOEC were estimated for mammals (volatiles) and for birds
and mammals (lead) and used with estimated exposures to calculate EHQs (Exposure Hazard
Quotients) for the receptor species. (A total EHQ was obtained by summing the component
EHQs. A total EHQ near 1 was taken as evidence of potential ecological risk for biota at the
site.)
6.2.4 Estimated Ecological Risk
The estimated EHQs for ingestion of lead were 0.004 for shrews and 0.008 for shrikes. The
estimated total EHQ for ingestion of volatiles (BTEX) by grouse was 0.01 (that for benzene
alone was 0.0008).
The estimated EHQ for voles exposed to volatiles by inhalation was 0.2, of which half the
risk was due to toluene. A similar EHQ (0.2) was estimated for grouse exposed to volatiles
11206.44
36
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by inhalation. These inhalation exposure risks were made quite conservative by the
assumption that the volatiles did not rise more than 1 cm above the ground level.
In summary, the highest estimated EHQ for reference birds and mammals exposed to the
contaminants of concern at OU6 was on the order of 0.2, and thus the site does not appear to
present a significant ecological risk.
Actual or threatened releases of hazardous substances from this site, if not
addressed by implementing the response action selected in this Record of
Decision, may present an imminent and substantial endangerment to public
health, welfare, or the environment.
11206.44 37
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7. DESCRIPTION OF REMEDIAL ALTERNATIVES
7.1 REMEDIAL ACTION OBJECTIVES
The Feasibility Study recommended that OU6 be considered for remedial action primarily
because of the potential risk from unrestricted domestic use of groundwater containing
contaminants derived from petroleum (BTEX). The Baseline Risk Assessment concluded that
the greatest risks at OU6 are associated with benzene in the groundwater.
Soil The results from the site remedial investigations and the risk assessment indicated that
contaminant concentrations present in the site soils are low and that there is currently no
identifiable source of further groundwater contamination. Therefore, no remediation of the
site soils was deemed necessary, and no remedial action objectives were developed for the
site soils.
Groundwater The groundwater remedial action goals for the OU6 source area are the
following:
• Prevent ingestion/direct contact with groundwater containing contaminants in excess
of MCLs or having non-zero MCLGs.
• For contaminants for which there are no MCLs, prevent the inhalation of vapors
from groundwater that contains carcinogens that could result in a cancer risk higher
than 1E-4 to 1E-6.
• For contaminants for which there are no MCLs, prevent ingestion or direct contact
with groundwater containing non-carcinogenic toxic substances at concentrations
that could cause adverse effects (result in a Hazard Index of more than 1).
• Attain residual contaminant levels that would restore the groundwater as a potential
source of drinking water.
The goal is to reach the concentrations described in the Safe Drinking Water Act ARAR
(40CFR141) for volatile organics:
Benzene Toluene Ethvlbenzene
MCL(ug/L) 5 1,000 750
7.2 REMEDIAL ALTERNATIVES
Three alternatives were developed and thoroughly analyzed in the FS.
7.2.1 Alternative 1 - No Action
Under this alternative, no action would be taken to address groundwater contamination. It is
considered as a baseline against which other alternatives can be compared. It is estimated
11206.44 38
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that groundwater contamination would persist for more than 30 years. There are no costs
associated with this alternative.
7.2.2 Alternative 2 - Limited Action
This alternative includes continued groundwater monitoring to detect and evaluate any
changes in contaminant concentrations and implementation of institutional controls to prevent
the use of the contaminated groundwater in the vicinity of the ski lodge from the existing
water supply wells and the construction of any new wells.
Institutional land use controls would be designed to prevent exposure to contaminated
groundwater. The controls would include posting the area and prohibiting the installation and
use of any well for drinking water that could extract contaminated groundwater or affect the
movement of contaminated groundwater. Figure 7 shows possible locations of signs
explaining the restricted use of groundwater.
Use of the groundwater will be prohibited until it is shown to reach drinking water standards
with respect to petroleum products.
Wells at the site would be monitored as part of the Eielson AFB Site-Wide Monitoring Plan,
to continue evaluation of the fate and transport of contaminants at OU6.
The details of monitoring and evaluation will be developed in the Site-Wide Monitoring Plan
documents.
For the purposes of estimating costs, periodic monitoring of groundwater is assumed to
continue for 30 years. Present worth costs are estimated at $370,000.
7.23 Alternative 3 - In Situ Treatment Using Air Sparging with Vapor Extraction
or Enhanced Bioremediation
Alternative 3 would involve an in situ remedial technology consisting of air sparging or
bioremediation. Air sparging is the use of injection wells to inject air into the groundwater.
The injected air would promote the transfer of the volatile organic compounds such as
benzene and petroleum hydrocarbons from the groundwater to the soil above, where they
would be extracted through vapor extraction wells (Alternative 3a), or the air injection can be
used to enhance native microbial activity in the saturated zone and the vadose zone, which
degrades the petroleum-related contaminants (Alternative 3b). The layout of a remedial
system for these two alternatives is shown in Figure 8.
Alternative 3 would also include implementation of institutional controls, as described for
Alternative 2, and a groundwater monitoring plan to track the status of the contamination and
attainment of the ARARs, shown above for Alternative 2.
Because this alternative would involve injection of air to the subsurface, air emissions from
the subsurface would be expected. Air emissions of 250 tons per year or more of an air
11206.44 39
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V^. fT\-:'.'i i: •'•_ / V * • i J jiiS'r*. X V
x\sN v. v \ \ \ '
- N A . ".- V \>^
^ ^T-J ^v N .\ ••-. .-»
* ^%s x X ', «t \ , --•
.. .,.,
V-:X«V-NX V"11
'.iv-r.-ir-i^^;.;:-^..^^.
\ OOWtSIC »*U«
lU^PIICS 10 M* M
MCLUOMO CHHXiNC »>i
wu at tituCKio
M lltOW IHt
fthSt »*«» SUPPlf
1. MJ. CKOUNOHAII •
•nu m BE vrpr
UNOt* lOCK Art) HO.
l^V-^ifl^miNO.s^i^^'-- -. : T^.^y^---:,-;: •'•-,''-.•..
4.^X»_;\^>S ^^X'xV'''-' '• 'i ' I ,;';-'.'.>-'.. "
\
LEGEND
-$~ Cround»oler Monitoring Wells
A Existing Woler Wglla
'•!-... Ground Surfoce Elev. Contour, Teet MSL
i..:.. Swomp
® Tormer Tonk Locations
Access Rooflj
-------
ORIGINAL SKI
LODGE WELL
38 SLW
IN BUILDING
PROPOSED
EQUIPMENT
BUILDING
PROPOSED LOCATION
OF IN SITU TREATMENT
SYSTEM
800* x 200'(Approx.J
X Proposed Locations of Air Sparging Wetls
Existing Monitoring Wells
Ground Surloc* Elev. Contour. Feet MSt
Existing Water Wells
Access Roads
Unpovcd Roads
200
Figure 8. Remedial alternative, OU6,
Eielson Air Force Base, Alaska.
Drown:
Reviewed:
Rev.1:
Final:
Dale:
Date:
Date:
Date:
-------
contaminant regulated under the Clean Air Act (as amended) would require a permit to
operate under 18 AAC 50.300.
Based on available information and modeling, the period for remediation is estimated to be
between 10 and 30 years. The present worth costs are estimated to be between $5 million
and $10 million.
11206.44 42
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8. SUMMARY OF THE COMPARATIVE ANALYSIS OF ALTERNATIVES
In accordance with federal regulations, the three cleanup alternatives were evaluated on the
basis of the nine criteria for choosing among remedial alternatives presented in the NCP
(Table 9).
8.1 OVERALL PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
Alternative 1 is not protective of human health and the environment, because no action would
be taken to address groundwater contamination and no controls would be implemented to
prevent use of the groundwater.
Alternatives 2 and 3 would use institutional controls to prevent the use of contaminated
groundwater until cleanup standards are achieved. If the treatment technology is found to be
effective in addressing the groundwater contamination, Alternative 3 would likely achieve
cleanup standards in less time than Alternative 2.
8.2 COMPLIANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS
Alternatives 1 and 2 would rely on natural processes to decrease contaminant concentrations
in groundwater. Drinking water standards would not be met in the vicinity of the ski lodge
for several decades.
Alternatives 1 and 2 are expected to attain Federal and State groundwater cleanup levels
through natural attenuation (dispersion, dilution, degradation). However, in the interim,
groundwater contaminant levels would continue to exceed MCLs and pose a threat to human
health and the environment.
Because Alternative 3 includes groundwater treatment, it should, in principle, achieve
groundwater cleanup standards more rapidly. The treatment system described in Alternative 3
would be designed and implemented so as to meet all applicable or relevant and appropriate
state and federal environmental regulations (ARARs), including air emission limitations.
83 LONG-TERM EFFECTIVENESS AND PERMANENCE
All alternatives will result in the decay of hydrocarbons by natural attenuation processes and
will result in the attainment of MCLs in the long term.
Alternative 3 would actively address the problem of contaminated groundwater and could
result in remediation more quickly than the other two alternatives. However, because of the
uncertainty associated with remediating contaminants in fractured bedrock, it is difficult to
predict whether the treatment would be effective. It is difficult to monitor a contaminant
"plume" in a fractured bedrock aquifer, because flow of the contaminants could be controlled
by a small number of hydrologically significant fractures. These are difficult to locate and
identify using conventional field methods and a reasonable density of sampling points.
11206.44 43
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TABLE 9 CRITERIA FOR SELECTION OF ALTERNATIVE REMEDIES FOR
CERCLA SITES
Criterion
Questions for Meeting Criterion
Overall protection of human
health and environment
Compliance with requirements
Threshold Criteria
How well does the alternative protect human health
and the environment, both during and after
construction?
Does the alternative meet all applicable or relevant
and appropriate state and federal laws?
Long-term effectiveness and
permanence of treatment
Reduction of .toxicity, mobility,
and volume
Short-term effectiveness
Implementability
Cost
Balancing Criteria
How well does the alternative protect human health
and the environment after completion of cleanup?
What, if any, risks will remain at the area?
Does the alternative effectively treat the
contamination to significantly reduce the toxicity,
mobility, and volume of the hazardous substance?
Are there potential adverse effects to either human
health or the environment during construction or
implementation of the alternative? How fast does
the alternative reach the cleanup goals?
Is the alternative both technically and
administratively feasible? Has the technology been
used successfully at similar areas?
What are the relative costs of the alternative?
State acceptance
Community acceptance
Modifying Criteria
What are the state's comments or concerns about
the alternative considered and about the preferred
alternative? Does the state support or oppose the
preferred alternative?
What are the community's comments or concerns
about the alternative considered and about the
preferred alternative? Does the community
generally support or oppose the preferred
alternative?
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44
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8.4 REDUCTION OF TOXICITY, MOBILITY, OR VOLUME THROUGH
TREATMENT
Alternatives 1 and 2 do not include treatment of contaminants at OU6. Alternative 3 would
reduce the total mass of contaminants in the groundwater through active treatment.
8.5 SHORT-TERM EFFECTIVENESS
Alternative 1 would not be protective of the community.
The implementation of Alternative 3 would not be expected to pose an unacceptable risk to
residents or workers. All potential impacts from construction and operation of the system
would be readily controlled using standard engineering controls and practices. Although
Alternative 3 would include groundwater treatment, it is not certain that treatment would be
able to achieve cleanup standards faster than natural processes, because of the site's
hydrogeological conditions, contaminant release history, and contaminant migration and
degradation processes.
None of the alternatives is expected to pose an unacceptable risk to residents or workers
during implementation. All potential impacts from the system's construction and operation
will be readily controlled using standard engineering controls and practices.
8.6 IMPLEMENTABELITY
Alternative 1, requiring no further action, would be the easiest to implement.
Alternative 2 would be readily implemented because the institutional controls and
groundwater monitoring would involve no appreciable administrative or technical difficulties.
Although Alternative 3 is technically feasible, it would require a phased approach to verify
the performance of the treatment system and to determine sizing criteria for the remedial
design. Furthermore, although air sparging/enhanced bioremediation treatment is a frequently
used technology, implementation in fractured bedrock is sometimes attended with unexpected
difficulties.
8.7 COST
Based on the information available at the time the alternatives were developed, the estimated
present value cost, in thousands of dollars, of the alternatives, assuming 7 percent interest rate
for 30 years, are the following:
Alternative 2 Alternative 3
Limited Action Air Sparging Bioremediation
Capital Cost ($ 1,000s) 30 3,800 2,600
Present Worth of Total Cost ($l,OOOs) 370 7,485 6,375
11206.44 45
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8.8 STATE ACCEPTANCE
The State of Alaska Department of Environmental Conservation concurs with the selection of
Alternative 2 as the remedial alternative. ADEC has been involved throughout the RI/FS
process, and the agency's comments have been considered and incorporated in this ROD.
8.9 COMMUNITY ACCEPTANCE
Comments received during the public meeting and during the public comment period were
considered in selecting the final remedial alternative. Alternative 1 had no proponents, and
doubts were expressed about the efficacy and cost-effectiveness of Alternative 3. The
community response to the remedial alternative is presented in the Responsiveness Summary,
which addresses comments received during the public comment period.
11206.44
46
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9. THE SELECTED REMEDY
The preferred valtemative is Alternative 2: Limited Action. The Air Force, EPA, and ADEC
selected this alternative over the other alternatives after evaluating the nine CERCLA criteria
described in Table 9. As described in Sections 7 and 8, Alternative 2 consists of institutional
controls to prevent current and future exposure to the contaminated groundwater, along with
groundwater monitoring.
9.1 INSTITUTIONAL CONTROLS
The selected remedy uses institutional controls to prevent current and future exposure to the
contaminated groundwater. Institutional controls include measures undertaken to limit or
prohibit activities that may result in exposure to hazardous substances in the groundwater at a
site. At this site, institutional controls governing land use will prohibit extraction and use of
groundwater.
9.2.1 Land Use Controls
The land use controls.which will govern use of the land and groundwater as long as it is
under the jurisdiction of the Air Force, will be prepared by Eielson AFB and submitted to
ADEC and EPA for approval.
Restrictions on the use of groundwater will include the following elements:
1. a property or site map showing the areas currently or potentially impacted by
groundwater contaminants at OU6
2. a prohibition on the installation and use of any well that could extract
groundwater contaminants or affect the movement of groundwater contaminants
located beneath OU6
3. a prohibition of any activity that may interfere with groundwater monitoring
activities including, but not limited to, maintenance of monitoring wells,
installation of new monitoring wells, and groundwater sampling
4. a prohibition of any activity that may result in the release of contaminants to
groundwater
5. a requirement of notice to and approval by ADEC and EPA of any proposal to
add to or alter land use controls
6. a requirement to notify ADEC and EPA of any proposal to change the existing
land use at OU6.
This will be implemented by posting signs, continuing to provide portable water to the site
from the base water system, and controlling access to all existing wells.
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In addition, to ensure the long-term integrity of the above land-use controls, the Air Force
will make sure that, to the extent that groundwater contamination remains above unacceptable
levels, deed restrictions or equivalent safeguards will be implemented in the event property
containing such contamination is transferred by the Air Force.
9.1.2 Transfer of Property
Conveyance of title, easement, or other interest in the real property subject to this ROD shall
be in accordance with Section 120(h) of CERCLA, 42 U.S.C. § 9620 (h).
9.13 Implementation Schedule
Within three months after final approval of the ROD, Eielson AFB shall implement and
develop a means to ensure the long-term integrity of the institutional controls.
9.2 GROUNDWATER MONITORING
Groundwater monitoring at OU6 will be done as part of the Eielson AFB Site-Wide
groundwater monitoring to be implemented in the 1994 field season. Specific monitoring
parameters, such as wells to be sampled, parameters to be analyzed, and frequency of
monitoring, will be defined in the Sampling and Analysis Plan (SAP) for the Site-Wide
Groundwater Monitoring Plan. Results of the site-wide groundwater monitoring will be
reported annually.
93 STATUTORY REVIEW
Because the selected alternative will result in hazardous substances remaining in the
groundwater at the site above health-based levels, a review will be conducted within 5 years
after commencement of the remedial action to ensure that the remedy continues to provide
adequate protection of human health and the environment. Under provisions of the site-wide
monitoring plan, the Sampling and Analysis Plan for OU6 will be updated periodically. The
SAP will describe the location of samples to be collected, the analytes that will be tested, and
the frequency of sample collection. Changes to the SAP may be made as appropriate, based
on review of the monitoring data. If the data indicate movement of contaminants in a
downgradient direction, measures will be taken to maintain effective knowledge of the extent
of the contaminant plume.
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RECEIVED
AUG 1 1 1994
10. STATUTORY DETERMINATIONS
f I'OtnAL FACILITIES SF BK
The selected remedy meets statutory requirements of Section 121 of CERCLA, as amended
by SARA. and. to the extent practicable, the NCR. The evaluation criteria are discussed
below.
10.1 PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
The selected remedy protects human health and the environment through the prevention of
access to contaminated groundwater. Groundwater contaminated with VOCs (volatile organic
compounds) will be remediated through natural attenuation, because the site is remote from
developed areas, the contaminants are confined largely in the cracks in fractured bedrock
(schist), and the prospects of success with active treatment of contaminants are not regarded
as being very good.
Institutional controls will eliminate the threat of exposure in groundwater through ingestion
and inhalation by preventing utilization of it. Natural attenuation will eventually reduce the
contaminants in the groundwater to levels at which institutional controls are no longer
necessary.
The estimated RME (reasonable maximum exposure) risk without remediation for residential
land use from these exposure pathways was 4E-3 for carcinogenic risk and an HI (hazard
index) of four for noncarcinogenic risks. The corresponding future industrial land use for
military personnel had a risk value of 2E-3 (0.002) and a Hazard Index of 1.2. The goal for
remediation through natural attenuation is cancer risks reduced to 1E-6 and an HI reduced
to 1.
10.2 ATTAINMENT OF APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS OF ENVIRONMENTAL LAWS (ARARS)
The selected remedy is expected to comply with all applicable or relevant and appropriate
requirements (ARARs) of federal and State of Alaska environmental and public health laws.
10.2.1 Applicable or Relevant and Appropriate Requirements (ARARs)
The remedy chosen for the site will comply with all action-, chemical-, and location-specific
ARARs, listed below:
10.2.1.1 Action-Specific ARARs
There are no action-specific ARARs required for the selected alternative.
10.2.1.2 Chemical-Specific ARARs
• MCLs and non-zero maximum contaminant level goals (MCLGs) established under
the Safe Drinking Water Act are relevant and appropriate requirements for
groundwater that is a potential drinking water source:
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Benzene Toluene Ethylbenzene Xylenes
MCL(ng/L) 5 1,000 700 10,000
• Alaska Water Quality Standards for Protection of Class (1)(A), Water Supply, Class
(1)(B), Water Recreation, and Class (1)(C), Aquatic Life and Wildlife (18AAC70).
10.2.1.3 Location-Specific ARARs
There are no location-specific ARARs for the selected alternative.
10.2.2 Inform ation-to-be-Considered
There is no Information-to-be-Considered for the selected alternative.
10.3 COST-EFFECTIVENESS
The selected remedy is cost-effective because it has been determined to provide overall
effectiveness proportionate to its costs and duration for remediation of the contaminated
groundwater. Alternative 3 with a present worth cost of $7.5 million or $6.4 million, is
significantly more costly than the selected remedy. Given the uncertainty about the
effectiveness of air sparging and enhanced bioremediation in fractured rock aquifers, the
benefits of active remediation do not justify the additional cost.
10.4 UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE
TREATMENT TECHNOLOGIES TO THE MAXIMUM EXTENT
PRACTICABLE
The U.S. Air Force, the State of Alaska, and EPA have determined that the selected remedy
represents the maximum extent to which permanent solutions and treatment technologies can
be used in cost-effective manner at the OU6 site. Of those alternatives that are protective of
human health and the environment and comply with ARARs, the U.S. Air Force, the State of
Alaska, and EPA have determined that the selected remedy provides the best balance of
tradeoffs in terms of long-term effectiveness and permanence, reduction in toxicity, mobility,
or volume achieved through treatment, short-term effectiveness, implementability, cost (as
discussed in the preceding section), and the statutory preference for treatment as a principal
element and considering State and community acceptance.
All alternatives would use readily available technologies and would be feasible to construct.
Alternatives 1 and 2 would be readily implementable; they require no additional remedial
action. The technologies involved in Alternative 3 are relatively limited in scope.
The most decisive factors in the selection decision were long-term effectiveness and
implementability. Alternative 2 provides the best option for cost-effective and practical
remediation of OU6, because it is expected that petroleum hydrocarbons will be released
slowly from the bedrock into the alluvial aquifer over a potentially long period of time and
that the processes of natural attenuation in the alluvial aquifer will suffice to reduce the
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concentrations from the bedrock aquifer below MCLs. Alternative 3 would in principle
'reduce the concentrations of contaminants in the bedrock aquifer more quickly, but the
improvement, given the nature of the technology and the geologic and hydrologic conditions
at the site, are not believed to be cost-effective. Regular monitoring will be done to ensure
that the release rate is low enough to protect human health and the environment.
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11. REFERENCES
Battelle. 1992. Remedial Investigation/Feasibility Study — Operable Units 3, 4, and 5
Management Plan, Eielson Air Force Base, Alaska. Battelle, Environmental
Management Operations, Richland, Washington. (Final).
CH2M Hill. 1982. Installation Restoration Program Records Search for Eielson Air Force
Base, Alaska. CH2M Hill, Gainesville, Florida.
EPA. 1991. Supplemental Guidance for Superfund Risk Assessments in Region 10.
U.S. Environmental Protection Agency, Seattle, Washington.
EPA, ADEC, and U.S. Air Force. 1991. Eielson AFB Federal Facility Agreement under
CERCLA Section 120, EPA Docket Number: 1089-07-14-120.
HLA (Harding Lawson and Associates). 1989. Installation Restoration Program Remedial
Investigation/Feasibility Study, Stage 3, Eielson Air Force Base, Draft Remedial
Investigation/Feasibility Study, Volume II (July 1988 to April 1989). Harding Lawson
Associates.
HLA (Harding Lawson and Associates). 1990. Installation Restoration Program Remedial
Investigation/Feasibility Study, Stage 4, Draft Remedial Investigation/Feasibility Study,
Volumes I through V. Harding Lawson Associates.
HLA (Harding Lawson and Associates). 1991. Installation Restoration Program Remedial
Investigation/Feasibility Study, Stage 4, Draft Remedial Investigation/Feasibility Study,
Volumes VII through XVIII. Prepared by Harding Lawson Associates.
Krumhart, A.P. 1982. Hydrologic Information for Land-Use Planning, Badger Road Area,
Fairbanks, Alaska. Water-Resources Investigation 82-4097. U.S. Geological Survey.
USAF (U.S. Air Force). 1991. Community Relations Plan for Environmental Restoration,
Eielson Air Force Base. Prepared by Eielson Air Force Base, Alaska.
USAF (U.S. Air Force). 1993a. Background Soil Quality, Eielson Air Force Base, Alaska.
Battelle, Environmental Management Operations, Richland, Washington (Final).
USAF (U.S. Air Force). 1993b. Background Groundwater Quality, Eielson Air Force Base,
Alaska. Battelle, Environmental Management Operations, Richland, Washington (Final).
USAF (U.S. Air Force). 1994a. Eielson Air Force Base OU6 Remedial Investigation/
Feasibility Study: Remedial Investigation Report (Final). Engineering-Science,
Richland, WA.
USAF (U.S. Air Force). 1994b. Eielson Air Force Base OU6 Remedial Investigation/
Feasibility Study: Baseline Risk Assessment (Final). Engineering-Science, Richland,
WA.
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USAF (U.S. Air Force). 1994c. Eielson Air Force Base OU6 Remedial Investigation/
Feasibility Study: Feasibility Study (Final). Engineering-Science, Richland, WA.
USAF (U.S. Air Force). 1994d. Proposed Plan for Operable Unit 6 and Other Areas
(Final). Engineering-Science, Richland, WA.
Weddleton, J., H. Richards, and R. Seifert. 1989. Building in Alaska. A Guide for Assessing
Risks and Costs of Water Well Drilling in the Fairbanks Area. Cooperative Extension
Service University of Alaska Fairbanks, Fairbanks, Alaska.
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EIELSON AIR FORCE BASE
OPERABLE UNIT 6
RESPONSIVENESS SUMMARY
A. OVERVIEW
The proposed cleanup alternatives considered by the US Air Force, Alaska Department of
Environmental Conservation (ADEC), and US Environmental Protection Agency (EPA) were
presented to the public in a proposed plan (U.S. Air Force 1994) and discussed in a public
meeting on 12 April 1994. This plan proposed alternative 2, limited action, as the preferred
method to address the fuel-contaminated groundwater in the bedrock under the ski hill at
Operable Unit 6. The preferred alternative makes the current restrictions on any use of
groundwater in the area an institutional control. The controls will remain in effect as long as
the contamination persists.
Public comments generally supported the plan as the best compromise among cleanup options.
These Sections Follow:
Background on Community Involvement
Summary of Public Comments From Comment Period and USAF Response
- Part I: Summary and Response to Local Community concerns
- Part II: Response to Technical and Legal Questions
B. BACKGROUND ON COMMUNITY INVOLVEMENT
Prior to being added to the EPA National Priority List in 1989, there was little opportunity
for community involvement in environmental activity at Eielson AFB. From 1982 until 1989,
the Air Force used the Installation Restoration Program (IRP) to identify potential
contaminated areas and investigate what remedial actions might be required. This was purely
technical and did not evaluate community concerns in the decision-making process. However,
after signing a Federal Facility Agreement with the State of Alaska and the US EPA, the Air
Force began its Superfund cleanup program, which includes extensive community
involvement.
A Technical Review Committee was established.in 1992 including three representatives from
the community (selected by local officials and the University of Alaska Fairbanks
Chancellor), industry representatives, and environmental agency representatives. Many of the
TRC participants are members of the professional public.
The Proposed Plan for Operable Unit 6 was advertised three times in two local papers. In
addition, more than 3,500 copies were added as an insert in the base newspaper and delivered
to every home in the Eielson AFB housing area. A news release announcing the Proposed
Plan and public meeting was sent to all local news media (radio, TV, newspapers) and the
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story ran on the front page of the base newspaper. The meeting was advertised on the base
access cable channel and in the base information bulletin as well as at least two local area
radio stations. Copies of the plan were delivered to various information repositories, plus
North Pole City Hall. Flyers were placed in store bulletin boards in Moose Creek, North Pole
and Salcha communities.
C. SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC COMMENT
PERIOD AND USAF RESPONSES
The public comment period on the Operable Unit 6 Proposed Plan was held from 22 March
until 22 April 1994. Comments received during that period are summarized below. Part I
addresses non-technical concerns, while Part II responds to technical and legal questions.
Each part is grouped by similar topics.
PART I - Summary and Response to Local Community .Concerns
- Topic: Water Quality Downstream in Moose Creek
- Public Comment: One person was concerned that carcinogens from contamination at OU6
could create a cancer risk for residents in Moose Creek, if they hadn't already done so. The
commenter indicated they knew a person who has cancer and wanted to know if the
contamination from Eielson could have caused this, and what the base was doing to protect
Moose Creek residents.
- USAF Response: The base has identified areas of suspected contamination and determined
the limits of contamination for those sites using monitoring wells, soil sampling, sediment
sampling, and surface water monitoring. The data appear to show isolated areas of
contamination, which test cleaner with distance from the source areas. As an additional
measure, the base installed a series of monitoring wells along the north boundary, adjacent to
the Moose Creek community. These wells show no evidence of contamination even reaching
the base boundary, so it appears unlikely any contamination is leaving or has left the base due
to contamination migrating through the soil or groundwater. Surface water sampling of
Garrison Slough and French Creek along the base boundary also show that water leaving the
base meets all state and federal water quality standards. This water quality monitoring will
continue for both groundwater and surface water throughout the base and along the boundary,
in particular. While this cannot confirm there were no releases in the past before testing and
sampling began, there is nothing now to suggest any contaminants left the base that would
have affected residents of Moose Creek community.
- Topic: Alternatives Selection
—Public Comment: A person called with comments supporting the preferred alternative.
The commenter was opposed to spending any money on a cleanup that was not a proven,
effective technique when current conditions posed no threat to human health. They believed
nature would heal itself best if man just left it alone. The caller approved of monitoring
plans to make sure contamination didn't spread from the area.
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- USAF Response: The caller was knowledgeable of early conditions at the site and
provided additional information regarding early activity associated with the refueling system.
The caller said there were diesel generator-driven pumps to move the fuel in the first year of
operating the system. The pumps caused too much pressure in the fuel lines and they leaked,
so the system was made a gravity-feed only from the second year on. The base community
relations officer met with the individual personally following the call. The Eielson cleanup
team appreciates this type of community involvement and recognizes the community is a
valuable source of new information about site conditions.
- Topic: Environmental Commitment Questioned
- Public Comment: One person commented they were not sure how sincere the Air Force
was regarding cleanups. Caller felt if the Air Force really cared about the environment they
would clean more sites instead of finding contamination and doing nothing about it. Caller's
comments were not limiting this to OU6, but to all work on base, particularly underground
tank removals. The commenter said they heard of a case where the Air Force removed a tank
and found contaminated soil but put clean fill in the hole and closed it up with no action.
- USAF Response: The Air Force is dedicated to protecting the environment, and Eielson is
fully committed to environmental cleanup. This is demonstrated by the funding as well as
increased staffing to address environmental issues. Because Eielson is a Superfund site, all
environmental operations are reviewed by the EPA and ADEC to make sure all commitments
are met
Underground storage tank removal operations at Eielson AFB are performed in concurrence
with Alaska state LUST regulations. The general procedure for underground storage tank
removal under the Alaska state LUST program is as follows:
• The storage tank is excavated and removed
• A Site Assessment is performed by an independent contractor
• If the Site Assessment indicates:
- a spill has occurred and the spill is confined to the area above the water table,
the contaminated soils are removed and replaced with clean fill dirt No further
action is taken at the site.
- a spill has occurred and the spill extends to the water table, soils are excavated
to the water table and the hole backfilled with clean fill dirt Further action will
be taken.
- a spill has occurred and the spill extends beneath a building or structure, as
much contaminated soil as possible is removed as far as the water table and the
hole backfilled with clean dirt Further action will be taken.
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• In the event of a release, a Release Investigation is performed in which soil borings
are made and samples taken to delineate the contaminant plume. If a plume is
detected, monitoring wells are installed and sampling is performed to determine the
extent of groundwater contamination. If contaminant levels require remedial action,
the site will undergo a study similar to studies conducted under CERCLA superfund
requirements. A remediation alternative action will be selected in agreement with
the state and the site will undergo cleanup action.
In 1992, three underground storage tanks were excavated and removed from service at the
base BX service station. A Release Investigation by an independent contractor indicated a
release had taken place and that petroleum contamination did extend to the water table. The
holes were backfilled with clean fill dirt and 10 monitoring wells were placed in the vicinity
of the service station. Groundwater analysis in 2 of the 10 wells did indicate groundwater
contamination at the site from the petroleum release. The level of contamination was above
state action levels. After conferring with the state regulatory .agency, the site was placed
under continued monitoring to determine if the natural attenuation process will reduce the
contaminants to below action levels. If future groundwater analysis indicates additional
action is required to address contamination at the site, Eielson AFB and the state regulatory
agency will determine which remediation alternative action will be selected to correct the
problem. This is the only site on the base where a release from an underground storage tank
has contributed to groundwater contamination.
PART n - Response to Specific Technical and Legal Questions
- Topic: Risk-Based Cleanup Levels for Soil Contamination
- Public Comment: One person had several questions. They wanted to know if all areas of
soil contamination (in excess of ADEC cleanup levels) had been identified. They asked if
there were any areas where soil contamination was contributing to groundwater
contamination. They wanted to know if there were any releases due to the now-removed
pipeline that served the tanks on the hilltop.
- USAF Response: In the initial IRP investigation conducted in 1989, 64 potentially
contaminated sites were identified at Eielson AFB. The individual sites were assigned to an
operable unit based on the type of contamination present or designated as a SER site for
further study and evaluation. Any additional sites located following the initial IRP
investigation are designated as Areas of Concern (AOCs). Each AOC is to be evaluated on
an individual basis to determine if contamination is present. A continuing study of past and
present activities at Eielson AFB is ongoing in an effort to identify and address any
potentially contaminated site at Eielson AFB not identified in the initial IPR investigation.
Soil contamination is contributing or has a potential to contribute* to groundwater
contamination at a number of sites at Eielson AFB. Remediation projects and removal
actions directed at contaminant removal from the soil are in current progress at several sites
on base. Present monitoring of groundwater at these sites shows groundwater contaminants to
be confined within the areas of the sites. Continued long-term monitoring of the groundwater
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at these sites will provide information on contaminant removal through remedial action or
through natural attenuation and will serve as a safeguard to indicate contaminant migration off
site, if this should occur. Regular monitoring of base boundary wells are an additional
safeguard to alert EAFB and the regulatory agencies of contaminant plume migration. This
will allow adequate time to apply appropriate cleanup alternatives to prevent migration of
contaminants beyond base boundaries.
Releases of fuel from the pipeline serving the former tank farm at Operable Unit 6 were a
problem which prompted a decision to convert the pipeline from a pump-charged system to a
gravity flow system. Although releases were noted during the operational life of the pipeline
system, documentation regarding leaks and spillage history in the pipeline area was not
precise, and actual spillage or leaking volumes are unknown. Because no reports exist which
indicate large spillage volumes associated with the pipeline, the Remedial Investigation
focused primarily on the tank farm leakage at the top of the hill. Site geology studies
indicate fuel spills associated with the pipeline would have characteristically followed the
same migration pathway as the fuel leaking from the tanks at the top of the hill, presumably
straight down to the underlying fractured schist bedrock.
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Attachment A
COMMUNITY RELATIONS ACTIVITIES
At Eielson Air Force Base Alaska
1982 Eielson conducts records search and interviews to identify environmental
problem areas under Air Force Installation Restoration Program.
1983-1989 Eielson AFB environmental investigations identify contamination.
Nov. 1989 Eielson AFB listed on EPA National Priority List for priority cleanup.
May 1991 Eielson AFB signs Federal Facility Agreement with EPA and ADEC.
Oct. 1991 Eielson AFB holds first public meeting to announce Superfund cleanup.
Oct. 1991 Community Relations Plan released.
Jan. 1992 Administrative Record established at University of Alaska Fairbanks library.
May 1992 Technical Review Committee established,including three community
representatives from North Pole, Fairbanks, and the University of Alaska,
Fairbanks.
Jun. 1992 Public meeting on Operable Unit IB proposed plan.
Dec. 1992 Public meeting on Record of Decision for OU-1B (Signed in Sep 92).
1992-1993 Interviews with 40 community members to update Community Relations Plan.
Jan. 1993 International Bioventing Symposium held at Eielson for innovative technology.
Sep. 1993 Video documentary on base environmental program released, aired on base TV.
Nov. 1993 Public meeting on OU-2 Proposed Plan and SER Phase 1 recommendations.
Apr. 1993 Public meeting on OU-6 Proposed Plan and Removal Actions for three sources.
In October 1991, Eielson AFB released its Community Relations Plan at the first
environmental cleanup public meeting. In subsequent public meetings in 1992 and 1993,
Eielson presented the Proposed Plans for Operable Unit IB and Operable Unit 6, and
discussed upcoming removal actions.
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From 1992 through 1993, surveys and interviews of more than 100 community residents were
used to update the Community Relations Plan. Eielson AFB prepares fact sheets on topics
like water quality, Technical Assistance Grants, Information Repositories, cleanup
technologies and work opportunities to keep the public advised on cleanup activity. These are
available at the information repositories, or by contacting the community relations point of
contact.
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