United Slates Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R03-90/104
September 1990
&EPA Superfund
Record of Decision:
Dover Air Force Base, DE
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50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA/ROD/R03-90/104
3. Recipient• Accession No.
4. Title and Subtitle
SUPERFUND RECORD OF DECISION
Dover Air Force Base, DE
First Remedial Action
5. Report Date
09/28/90
7. Author(s)
8. Performing Organization Rept No.
». Performing Organization Name and Addreaa
10. ProjecVTaak/Work Unit No.
11. Contract(C) or Grant(G) No.
(C)
12. Sponsoring Organization Name and Addresa
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
13. Type of Report & Period Covered
800/000
14.
15. Supplementary Notes
16. Abstract (Limit: 200 words)
The 3,734-acre Dover Air Force Base site is an active military base in Dover, Kent'
County, Delaware. Surrounding land use is primarily agricultural/residential, and
wetlands associated with stream floodplain areas are located onsite. Since 1941, the
base has operated as a military air field and has served several different functions
including present day cargo operations. Hazardous waste has been generated at the
, base from industrial operations, fuels management, fire training, and pesticide use.
These wastes have been handled in various manners since 1941, including disposal in
onsite landfills and pits, use in fire training exercises, and discharge to surface
drainage ditches. A 1.3-acre area referred to as Fire Training Area #3 (FT-3),
located in the northeastern portion of the site, was used to conduct fire training
exercises, and currently contains several waste pits, an oil/water separator,
dumpsters, and an underground storage tank used during the exercises. From 1962
until 1970, contaminated waste oils and fuels were placed on an old aircraft or
spread in a pit and ignited for fire training exercises in FT-3. Approximately 1,000
gallons of waste material were used per exercise, with two exercises being performed
each week. In 1970, the original pit was filled in, and a new pit was excavated.
(See Attached Page)
DE
17. Document Analysis a. Descriptors
Record of Decision - Dover Air Force Base,
First Remedial Action
Contaminated Media: soil, sludge, debris
Key Contaminants: VOCs (benzene, toluene, xylenes), metals (lead)
b. Identifiers/Open-Ended Terms
c. COSA71 Field/Group
18. Availability Statement
19. Security Class (This Report)
None
20. Security Class (This Page)
None
21. No. of Pages
61
22. Price
(See ANSI-Z39.18)
See Instructions on Reverse
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
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EPA/ROD/R03-90/104
Dover Air Force Base, DE
First Remedial Action
Abstract (Continued)
Metal dumpsters were placed in the pit and waste JP-4 fuel was ignited on them during
quarterly training exercises. Drainage from the pit was collected in an underground
oil/water separator, and was removed from the site by a waste oil recovery contractor.
An underground storage tank, used to store JP-4 fuel used in the exercises, and
underground pipes, also are located near the pit. Fire training exercises ceased in
1989. Investigations in 1989 by Dover Air Force Base revealed the presence of
contaminated soil in the pit area. Residual waste fuel, oil, and sludges still remain in
underground piping, creating a fire and explosion hazard. This Record of Decision (ROD)
addresses remediation of soil and structures within the FT-3 area. Subsequent RODs will
address other sources of contamination and contaminated ground water in other site areas.
The primary contaminants of concern affecting the soil, sludge, and debris are VOCs
including benzene, toluene, and xylenes; metals including lead; and oils.
The selected remedial action for this site includes removing residual liquids, sludges,
and solids from the underground tank, oil/water separator, and piping, and transporting
these materials offsite for disposal; excavating the underground tank, oil/water
separator, dumpsters, and piping, and decontaminating them using high-temperature steam
cleaning equipment; disposing of the contaminated steam cleaning solution and excavated
debris and structures offsite; backfilling and grading excavated areas; and placing a
revegetated soil cover over the FT-3 area. The estimated
present worth cost for this remedial action is $100,000, which includes a total O&M. cost
of $5,000 over 20 years.
PERFORMANCE STANDARDS OR GOALS: Chemical-specific cleanup goals were not provided.
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THE DECLARATION FOR THE RECORD OF DECISION
•REMEDIAL ALTERNATIVE SELECTION
s
Site; Fire Training Area 3, Dover Air Force Base, Kent County, Delaware
Statement of Baals and Purpose
This Record of Decision presents the selected remedial action for Fire
Training Area 3 Operable Unit (Site) at Dover Air Force Base, in Kent County,
Delaware, which was chosen in accordance with the requirements of the
Comprehensive Environmental Response. Compensation, and Liability Act of
1980 (CSRCLA), as amended by the Superfund Amendments and Reauthorization
Act of 1986 (SARA) and, to the extent practicable, the National Oil and
Hazardous Substances Pollution Contingency Plan (KCP), 55 Fed. Reg. 8666-8865
(March 8, 1990) to be codified at 40 C.F.R. Part 300. This decision is based
en the administrative record for this Site.
The State of Delaware and the United States Environmental Protection
Agency (SPA) concur with the selected remedy. The information supporting
this remedial action decision is contained in the administrative record
located in the Dover Public Library, Dover, Delaware.
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 ar.d substantial endangerment to
public health, welfare, or the environment.
Description of_ the Remedy
This operable unit it the first of several operable units for Dover Air
Force Base. Investigations are ongoing at Dover Air Force Base. As more
information becomes known about additional.operable units, further response
action will be taken. The primary objective of the selected remedy Is to
protect public health and the environment by abating the fire and explosion
threat. Piping and structures at the site are contaminated with residual
waste fuel and waste oil which pose a threat of fire and explosion. The
selected remedy addresses the principal threats to human health presently
posed by the Site. The Site structures, which include an underground storage
tank (UST), an oil/water separator and above ground dumpsters, will be
removed and decontaminated. Soil surrounding the underground tank will be
tested after removal of the tank. A risk-based determination will be made as
to the disposition of the soil near the UST upon completion of the soil
tests. A soil cover will be placed over the Site and the Site revegetated.
The decontamination/removal of the Site structures consists of the following
major components:
A pump will be used to pump the residual waste fuel/oil from the
structures.
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. The underground tanks and structures will be excavated.
. High temperature and pressurized steam will be used to decontaminate
the structures. After decontamination, disposal of th§ structures will be
accomplished.
. The liquid sludge and decontamination water will be tested. If found
to be a RCRA wast*, regulation* covering disposal of RCRA liquid wastes will
be followed. Otherwise Delaware UST regulation* governing disposal will be
followed.
Ae part of the continuing base wide study underway at Dover Air Force Bast,
any degradation in groundwatar and surfacewater caused by the Site (if any)
will be identified.
Declaration of Statutory Determinations
The selected remedy is protective of human health and the environment,
complies with Federal and State environmental laws that are legally applicable
or relevant and appropriate to the remedial action, and is cost-effective.
This remedy utilizes permanent solutions and alternative treatment (or
resource recovery) technologies to the maximum extent practicable, and
satisfies the statutory preference for remedies that employ treatments that
reduce toxlcity, mobility, or volume as a principal element.
A review will be conducted within five years after commencement of reacdial
action to ensure that the remedy continues to provide adequate protection of
human health and the environment.
ARTHUR G. ERICSON, Colonel, USAF DATE
Commander
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RECORD OF DECISION
REMEDIAL ALTERNATIVE SELECTION
SITE FT-3: FIRE TRAINING AREA 3
DOVER AIR FORCE BASE, DELAWARE
September 1990
Prepared for:
Headquarters Military Airlift Command
DCS Engineering & Services (HQ MAC/DEV)
Scott Air Force Base, Illinois 62225-5000
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RECORD OF DECISION
TABLE OF CONTENTS
SECTION PAGE
I SITE NAME, LOCATION, AND DESCRIPTION 1
II SITE HISTORY AND ENFORCEMENT ACTIVITIES &
III HIGHLIGHTS OF COMMUNITY PARTICIPATION 8
IV SCOPE AND ROLE OF OPERABLE UNIT 9
V SUMMARY OF SITE CHARACTERISTICS 10
VI SUMMARY OF SITE RISKS U
VII DESCRIPTION OF ALTERNATIVES 13
VIII SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES 2-
IX DESCRIPTION OF THE SELECTED REMEDY 2S
X STATUTORY DETERMINATIONS . 30
XI RESPONSIVENESS SUMMARY 22
XII REFERENCES 3:
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THE DECISION SUMMARY FOR REMEDIAL ACTION SELECTION
FOR FIRE TRAINING AREA 3 OPERABLE UNIT OF THE DOVER AIR FORCE BASE
I Site Name. Location, and Description
Dover Air Force Base
The Dover Air Force Base (Dover AFB) is a 3,734-acre installation
located in eastern Delaware, approximately 3.5 miles southeast of the City of
Dover, in Kent County. Figure 1 presents the regional location of Dover AFB,
which is surrounded primarily by cropland and large farms. Communities in the
vicinity of the facility include the City of Dover (Dover AFB is within city
limits), Little Creek and Port Mahon Annex approximately 3 miles and 5 miles
respectively to the north, and the Dover Family Housing Annex adjacent to the
facility, as shown in Figure 2. Routes 9 and 13 run northwest-southeast to
the east and west of the facility, respectively; Route 8 runs east-west north
of the facility.
Dover AFB is located on a ridge between the St. Jones River to the south
and west and Little Creek to the north. Both rivers flow eastward to the
nearby Delaware Bay. The topography is flat with very little relief. Surface
elevations range from 10 feet Mean Sea Level (MSL) along the St. Jones River
southeast of the base to 30 feet MSL along the base's western boundary. The
maximum local relief is approximately 12 feet at the St. Jones River.
Dover AFB Geology
Dover AFB lies within the Coastal Plain Physiographic Province, a region
underlain by sedimentary deposits. These deposits consist of interlayers of
gravel, sand, clay, shale, limestone, and marl that dip toward the southeast.
They overlie, at a great depth, crystalline rocks that consist mainly of
micaceous schists and gneisses of the Wissahickon Formation. The Coastal Plain
sediments belong to different formations, including the Columbia at the
surface, the Kirkwood, and other Tertiary and Cretaceous soils.
The Columbia sediments consist of interlayers of gravel, sand, silt, and
clay. They were deposited in stream channels, flood plains, and associated
environments. From the Kent-New Castle County line south, the Columbia
sediments consist of a sand layer that thickens southward across Kent and
Sussex Counties. The color of these sands ranges form red-brown to dusty red
depending on the amount of iron present in the sands. In the vicinity of the
City of Dover there is a transition from predominantly fluvial sediments to
marine sediments, which is evidenced by changes in color and sorting.
Therefore, the Columbia deposits are distinguishable from the underlying gray-
black Kirkwood Formation. The Kirkwood Formation, which is of Miocene Age,
was found to consist of dark gray, hard, silty clay that contains traces of
fine sand and silt. The top of this formation was encountered between -8 and
-43 MSL (SAIC, 1989).
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Dover AFB Groundwater
The Cheswold and Piney Point aquifers are the primary water supply
aquifers in the Dover area. The Cheswold is composed of fine-to-coarse sand
with shells and is 50 to 75 feet thick in the Dover area. The Piney Point
aquifer consists of fine-to-medium glauconitic sand and is separated from the
Cheswold aquifer by a thick, silty sand confining unit.
The Columbia aquifer consists of fine-to-coarse sand with discontinuous
interlayers of clay and gravel. Published data indicate that the average
hydraulic conductivity for this aquifer in central and southern Delaware is
about 3.1 x 10° centimeters per second (cm/sec) and that a specific yield of
0.15 is considered representative for this aquifer (SAIC, 1989). The
groundwater table is shallow, and groundwater in some locations travels fairlv
short distances before discharging into nearby surface waters.
The Cheswold and Piney Point aquifers provide approximately 80 percent
of the total municipal and industrial water pumped in Kent County (Leahy,
1982). By contrast, pumping from the Columbia aquifer is minor (Johnston,
1977) and the water is used primarily for irrigation and domestic supply.
However, because the Columbia is easily accessible and can provide large
quantities of water, it is among the most important statewide groundwater
resources. According to Sundstrom (1968), the Frederica and overlying Miocene
sands supply the towns of Felton, Frederica, Harrington, and Milford, as well
as several food processing and poultry industries. The Frederica is not used
to supply water in the Dover AFB area. Several production wells that tap
these deeper aquifers are located at Dover AFB. Three of these wells are
screened in the Cheswold aquifer between -188 and -268 feet MSL. The other
four production wells tap the Piney Point aquifer and are screened at
approximately -450 to -560 feet MSL.
Dover AFB- Surfacewater
The highest elevation (18 feet MSL) along the southeast-northwest runway
marks the location of a drainage divide on Dover AFB. Figure 3 presents
installation surface drainage patterns. Surface runoff at the base is mostly
to the north and south. The areas north of the divide drain into the small
streams that feed (offbase) into the Morgan and Pipe Elm Branches, which in
turn flow northeast to Little Creek. The areas south of the divide drain into
the small tributaries of the St. Jones River. Both the Little Creek and St.
Jones River flow eastward to the Delaware Bay.
Onbase runoff and nonprocess waters are discharged to several surface
water diversions (i.e., open ditches). In areas where the elevation of the
bottom of the diversions is higher than the water table, surface waters may
infiltrate and recharge groundwater. However, in areas where the diversions
and/or on-base streams have cut below the level of the water table,
groundwater appears to discharge into those diversions and streams.
Surface water flow is generally in the same direction as groundwater. in
areas underlain by the Columbia Formation, which forms a water table aquifer
under the region. A groundwater divide roughly coincides with the topographic
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divide (southeast-northwest runway) of Dover AFB. In general, groundwacer in
the northeast portion of Dover AFB flows north toward Morgan and Pipe Elm '
Branches, and in the southwest portion of Dover AFB flows south toward Sc.
Jones River and its tributaries.
The water table elevations at Dover AFB (Figure 4) indicate that the
gradients south of the divide are greater than the gradients to the north.
Minimal or no groundwater movement is shown to occur beneath the runways at
Dover AFB. This lack of groundwater movement is attributed to the large
surface areas occupied by the runways, which affect the infiltration of
rainfall and consequently the recharging of the water table in the central
portion of Dover AFB.
Dover AFB Demographic Information
Dover AFB has two runways and about 1,700 buildings. It employs
approximately 5,000 military personnel and over 1,400 civilians.
Lands adjacent to Dover AFB include single and multifamily residential
areas, industrial zones, commercial land along major roads, and large areas of
agricultural and open lands. The large residential areas are located across
U.S. Route 113 for base personnel and generally southwest of the base, across
the St. Jones River. Numerous low-density single family homes are scattered
throughout the area around the base. Major industrial areas are located to
the north of Dover AFB, and commercial areas are located along major roads to
the north and west. Government and institutional uses include schools across
from the base on U.S. Route 113, and numerous local, State, and Federal
buildings in the City of Dover. Agricultural and open land areas can be found
in many locations along the perimeter of Dover AFB, especially to the south
and east.
Dover AFB Wildlife Uses and Wetlands
Dover AFB has limited habitat available for wildlife. The wildlife
present on base consists of small mammals and birds and an occasional white-
tailed deer. There are no threatened or endangered animal or plant species or.
base, and game hunting is not allowed.
The Department of Interior estimates that Delaware has over 220,000
acres of wetlands; 23 percent of Kent County is estimated to consist of
wetland areas. Wetlands play a critical role in the hydrologic cycle and have
a variety of ecological and social benefits that have led to their increasing
protection by the U.S. Government, as well as the State of Delaware. As pare
of the Federal Government's program to preserve and enhance the nation's
wetlands, the National Wetlands Inventory (NUI) Project has developed
generalized (1:24000 scale) maps of wetland types. Wetlands in the vicinity
of the Fire Training Area #3 are discussed below.
Fire Training Area #3
Fire Training Area *3 (Site FT-3) is located in the northeastern portion
of Dover AFB, and to the east of the north-south airfield runway, as shown in
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Figure 5. Situated approximately 800 feet from the installation boundary, i:
is adjacent to a tributary of Little Creek. The portion of the Site that is
currently inactive--covering approximately 1.3 acres--served as the most
recent fire training area, from 1962 to 1989. A square, unlined area (pit) of
unknown size--adjacent to the tributary--was formerly used for training from
1962 to early 1970 (Figure 6).
Site FT-3 Geology
Evaluation of the subsurface information obtained during the field
investigation (SAIC, 1989) indicates that the central portion of the Site is
underlain by a layer of fill material comprised of a mixture of silt, sand,
and clay. It appears that the fill, which is 4 to 6 feet thick, is composed
of onsite soils and was built during the construction of the existing fire
training area and burial of the previous fire training area. Under the fill
and ground surface at the other locations of the site, the borings encountered
the unconsolidated material of the Columbia Formation, which ranges in
thickness from 50 feet in the western portion of the site (well MV-44d) to 40
feet in the eastern portion (well MV-20). The material consists primarily of
fine-to-medium sand that grades with depth to coarse sand, and includes
localized layers of silt, clay, and gravel. A clay layer that is 8 to 10 feet
thick was encountered throughout much of the Site at a depth ranging from the
ground surface at well MW-20 to 5.5 feet below ground surface at well MW-19.
Localized lenses of gravel ranging in thickness from 3 to 5 feet were
encountered in several of the borings; however, they appear to be laterally
discontinuous.
Underlying the unconsolidated material of the Columbia Formation are
mostly dark gray clay layers of the Kirkwood Formation. The upper few feet of
the Kirkwood were penetrated by all five boreholes used to install the deep
monitoring wells. The Columbia/Kirkwood Formation interface beneath Site FT-3
ranges in elevation from approximately -28 feet MSL in the southwestern
portion of the site to -32 feet MSL in the northern portion.
Site FT-3 Groundwater
Groundwater at Site FT-3 is found within the Columbia aquifer at a
shallow depth ranging from about 4 to 11 feet below ground surface. Table 1
presents groundwater measurements in the monitoring wells of Site FT-3 that
were taken in January, June, and July of 1988. As shown in the table, the
water table elevations varied slightly with the change in seasons, with the
highest levels recorded in the spring. The groundwater flow direction is
generally northeast at a gradient of approximately 0.46 percent from well MW-
18 to well MW-20, and 0.23 percent from well MU-44s to well MW-43s. Figure 7
presents groundwater elevation contours as measured on July 13, 1988. Those
contours confirm the northeasterly groundwater flow direction.
The similar groundwater levels observed in each pair of deep and shallow
wells (nos. 43 and 44) indicate that the Columbia aquifer is hydraulically
connected and that the clay layers encountered during well installation do not
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ace as confining layers in the aquifer. The shallow groundwater flows from
under the site to the adjacent streams to the north.
Site FT-3 Surfacevater and Wetlands
The ground surface at Site FT-3 is mainly flat — sloping gently to the
north and east — with elevations ranging from about 20 to 12 feet MSL. The
major topographic feature in the vicinity of the site is the stream valley
containing Pipe Elm Branch, which flows northeast to Little Creek.
Site FT-3 is adjacent to some wetlands, as shown in Figure 8. These
wetlands were located using NWI information based on aerial photography
(SAIC, 1989).
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PENNSYLVANIA
NEW JERSEY
MARYLAND
DELAWARE
VIRGINIA
ATLANTIC
-OCEAN
GINIATJ^I
^
isSt^&^-^i' r:-,-*<• -.-v.
*ra, »CALt £ 1° Mlt£t
VIRGINIA
•OURCC: COMMEACUL HtOHWAY
FIGURE 1
DOVER AFB
REGIONAL LOCATION
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Delaware
Bay
Simon*
ft/Mr
Mthon
Rivtr
PORT
MAHON
POL ANNEX
LITTLE
CREEK
DOVER
APB
MMILY
MOUSING
ANNEX
Murdtrklll
Rivtr
012
FIGURE 2
LOCATION OF DOVER AFB
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Can*** Urn
Unlmprww* Road
Off-tea ConanwttM W*l
Dr«ir«M Dtncton
FIGURE 3
INSTALLATION DRAINAGE. DOVER AIR FORCE BASE
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Ug«rt
USAF Property L*»
Driin* j» Ctanrwl
Centaur l>»
**••. blkiMMd
OreuntfwilV
*fc- -• ~«-
l^> v*<» "«•
Oividt
I
f /" - ^7^
^ffir
\ 5 / ^*
J *- F
>7T^/^ •
3H&yZ5s&
^ Vs.
\OSTSD ^X. VX\
^^ V X\ \
•^Sg^^%i-c,,*Of
'^^^^f^p:
Ft*t
FIGURE 4
WATER TABLE ELEVATION OF COLUMBIA AQUIFER
AT DOVER AFB (AUGUST 1988)
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i*oa retT
•
FIG' : 5
DOVER Al IITE PLAN
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PIPE ELM BRANCH
TO LITTLE RIVER
N
DRAINAGE CHANNEL
TRIBUTARY
FIGURE 6
SITEFT-3: FIRE TRAINING AREA 3
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• Monitoring W«l (t-ShtBow. d.Q«»p)
" Sod BorinVs«flvfing Point
^» OroundMfer BtvUton Contour (MSL)
£ Data Ragocd to CeflMben Point (Ft MSL)
— QroondwtW Flow ttMflen
680
FIGURE 7
SITE FT-3: FIRE TRAINING AREA - GROUNDWATER ELEVATION (7/13/88)
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PF01A
N
i
NOTE:
WET LAND TYPES
PF01A—Peulwint,
Dtciduoul, Timponry
R2SOWZx-Riv»rlnt, Lowtr Pertnniaf,
Open Wlt«r/Unknown Bottom,
Intermittently Expowd/Pcrmtntnt,
Exavited
FIGURE 8
SITE FT-3: FIRE TRAINING AREA - ADJACENT WETLANDS
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TABLE 1
Groundwater Elevation Survey at Site FT-3
Dover Air Force Base
(all elevations in units of feet mean sea level)
Measurement Date
Well No.
18
19
20
43s
43d
44s
44d
Top of Casing
Elevation
19.45
15.99
12.06
14.15
14.06
20.61
20.99
Ground Surface
Elevation
IS. 13
14.42
10.39
11.62
11.70
17.78
18.06
1/15/88
6.74
5.95
5.83
6/8/88
—
—
—
7.17
7.21
8.41
8.28
7/13-14/88
(Purging)
7.14
6.07
5.93
6.33
6.38
7.66
7.48
7/13-14/88
(Sampling)
13.26
5.08
5.87
6.28
6.29
7.57
7.49
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II SITE HISTORY AND ENFORCEMENT ACTIVITIES
Site History
Dover AFB
Dover Municipal Airfield was leased to the U.S. Army Air Corps in
December 1941 and served as a. base for different activities until it was
deactivated in September 1946. During that period, the base served one or
more functions--a coastal patrol base, a logistic and maintenance support
facility for U.S. Air Force units, an operational training base, a site for
the development of air-launched rockets, and a Pre-Separation Processing
Center for personnel leaving the service at the end of World War II.
The base was periodically used by the Air National Guard for training
exercises during the time of deactivation. The base was reactivated and
designated as Dover Air Force Base in July 1950. In March 1952, accompanying
a transfer of command to the Military Air Transport Service (now Military
Airlift Command), the base mission switched from air and land defense to cargo
operations, which are currently the main operations at Dover AFB.
Hazardous wastes generated at Dover AFB result from industrial
operations, fuels management, fire training, and pesticide use. The wastes
include waste fuels, oils and solvents, empty pesticide containers,
transformers containing polychlorinated biphenyls (PCBs) , wastewaters from
industrial shops, and excess paints.
Hazardous wastes have been handled in various manners at the base since
1941. From 1941 through 1963, landfills and/or pits located along the
perimeter of the base were used as disposal sites for oils, paint, hydraulic
fluid, and solvents; combustible chemicals such as oils, fuels, and solvents
were used at fire training areas in routine fire training exercises; and
wastewater from industrial shops, such as the engine buildup shop and the
plating shop, were discharged to a storm drainage ditch that emptied into a
tributary of Little Creek.
From 1963 through 1968, an industrial waste collection system was used
to collect waste oils, solvents, and contaminated fuels for recycling or use
in fire training exercises. However, the untreated wastes of the plating shop
continued to be discharged into the storm drainage ditch during this period.
In 1968, the industrial waste collection system was enlarged to include the
collection of wastes generated by the plating shop. From 1981 until the
present time, the different wastes generated at the base have been disposed of
offbase using approved procedures. JP-4 fuel was the only waste used for on-
base fire training after 1975; however, fire training exercises ceased in Mav
1989.
Site FT-3
From 1962 through early 1970, contaminated waste oils and fuels were
either placed on an old aircraft that was brought to the site for training
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exercises, or spread in Che water-saturated former pit and ignited twice per
week. Drums of waste oil and fuels originating from shop operations were
stored near the site and used as the source of fuel for fire training
exercises. At least 1,000 gallons of waste oil and fuel were normally used
per exercise; however, if more waste was available, it was also burned. Based
on chemical tests performed on soil samples taken from the site during the
U.S. Air Force's Installation Restoration Program Phase II, Stage 2
Investigation (SAIC, 1989), it appears that this pit was closed by covering it
with 6 to 8 feet of soil.
A new circular pit with a 12-inch berm around it was built to the
southwest of the square pit in early 1970; this pit was used until 1989 as the
fire training area at Dover AFB. During this period, the training exercises
were limited to once per quarter and used only off-specification JP-4 as fuel.
Unconsumed fuel, water, and aqueous film forming foam, which was used to
extinguish the fires, were drained to an underground oil/water separator that
was installed at the site in the early 1970s. Oil was then collected
periodically by a contractor for reuse and recovery. It also has been
determined that an underground storage tank (UST) exists near this new pit
that was used to store JP-4 for the training exercises. The size of the UST
is unknown; it is assumed to be located at the northwest corner of the Site.
Other onsite structures include underground pipes and 20 closely spaced
dumpsters that were placed inside the circular pit. The dumpsters used to be
sprayed with JP-4 and ignited to simulate an airplane on fire for training
exercises.
Enforcement Activities
The Air Force, EPA, and DNREC signed a Federal Facility Agreement on
June 29, 1989, pursuant to Section 120 of CERCLA, which provides for the
oversight and enforcement of Air Force Remedial Action at the Dover AFB. EPA
issued a RCRA Corrective Action Permit which defers corrective action under
RCRA to implementation of Remedial Actions under the Federal Facility
Agreement.
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Ill HIGHLIGHTS OF COMMUNITY PARTICIPATION
The Remedial Investigation/Focussed Feasibility Study (RI/FFS), Proposed
Remedial Action Plan (RAP), and background documentation for Site FT-3, were
released to the public for comment in August 1990. These documents were made
available to the public in the local information and administrative record
repository at the Dover Public Library, Dover, Delaware. The notice of
availability for these documents was published in the News Journal and the
Delaware State News on Tuesday August 14, 1990. A public comment period on
the documents was held from August 14, 1990 to September 27, 1990.
Additionally, a public meeting was held at 7:00 P.M. on August 30, 1990, at
the Dover AFB Officer's Club. At this meeting, representatives from the Air
Force, EPA, and DNREC answered questions about Site FT-3 and the remedial
alternatives under consideration. A response to the comments received during
this period is included in the Responsiveness Summary, which is provided in
Section XI of this Record of Decision (ROD). The Responsiveness Summary is
based on oral and written comments received during the public comment period.
The above actions satisfy the requirements of Sections 113(k) and 117 of
CERCLA, 42 U.S.C. Sections 9613(k) and 9617. The decision for this site is
based on the administrative record.
-------
IV SCOPE AND ROLE OF OPERABLE UNIT
As with many Superfund sices, the problems at the Dover AFB are complex.
As a. result, the Air Force has organized the remedial work into Operable
Units. This ROD addresses the first planned remedial action at the base. The
Air Force is continuing with the Dover AFB-wide study that will determine the
next Operable Units to be remediated.
The Operable Unit authorized by this ROD addresses the contaminated
soils and structures at Site FT-3. This ROD addresses risks from this area,
including the risk from dermal contact and accidental ingestion, and the
potential for contaminants to migrate to groundwater. Groundwater and the
adjacent drainage ditch that leads to Pipe Elm Branch will be investigated as
part of the Dover AFB area-wide study, and will be addressed in a subsequent
ROD. Further, soils immediately surrounding the UST were not tested during
the investigation. Therefore upon implementation of the remedy chosen by this
ROD, these soils will be tested. If the analysis indicates soil contamination
in excess of levels previously detected, a subsequent risk assessment will be
performed.
-------
V SUMMARY OF SITE CHARACTERISTICS
While this ROD focuses on the potential remediation of soil and
structures at Site FT-3, the discussion of contamination includes all media
investigated (i.e., soil, structures, groundwater, surface water, and
sediment). Discussing contamination in a broader context provides a more
comprehensive environmental framework upon which to base decisions on
remediation. Table 2 presents contaminants detected in Site FT-3 soils and
groundwater.
Site FT-3 Soil and Structures
Figure 9 is representation of Site FT-3 and shows the locations of
present and former fire training pits, the location of soil borings, and the
TPH concentrations (with isoconcentration contours) in soil at each boring in
descending order of depth. Figure 10 shows the Total Petroleum Hydrocarbons
(TPH) soil isoconcentration contours along with the location of the adjacent
wetlands (illustrated in Figure 8). A total of 14 borings were drilled in and
around the study site. Four of these borings (d9 through d!2) were located
along two stream channels--Pipe Elm Branch to the north and an unnamed
intermittent stream to the northeast. Samples were taken at intervals below
the ground surface at 1 to 3, 4 to 6, and 7 to 9 feet. In addition, 10
borings (d30 through d48) that fan out from the current pit were sampled ac 0
to 2, 2 to 4, 4 to 6, and 6 to 8 feet below ground surface.
The soils were analyzed for volatile organic compounds (VOCs), lead, and
TPH (SAIC, 1989). The TPH concentrations at 2 to 4 feet below ground surface
are generally higher and have greater areal extent than the levels at depth.
These levels are contoured in Figure 9 to show the extent of soil
contamination. The isoconcentration contours were developed by SAIC based on
available data. Variations between the contours and the actual TPH
concentrations in soil may occur due to isolated pockets of contaminated soil
assumed to be present at Site FT-3.
Note that the results of soil gas analyses performed at Site FT-3
indicate that maximum detections of TPH (Figure 11) and toluene (Figure 12) in
the soil gas do not coincide with each other or with the locations of maximum
TPH detections in soil (SAIC, 1989). The maximum detection of TPH (greater
than 1,000 parts per billion (ppb)) in soil gas is located parallel to the
paved area of the site, extending from the taxiway and adjacent to the
southwest end of the fire training area. Analysis of soil near the same
location (soil boring d48) did not disclose the presence of TPH. In contrast
to the results of the soil gas analyses, the maximum for TPH in soil occurs at
sample location d44--the northern end of the fire training area. This lack of
coincident maxima between the soil and soil gas analyses suggests that TPH in
the soil gas may have an independent source--perhaps nearby refueling
operations.
Figure 13 locates the vertical profile of TPH concentrations depicted in
Figure 14. This profile was developed from soil analysis data for TPH (SAIC,
1989), and shows one feature that is not clearly distinguishable from the
10
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contouring of TPH concentrations in soils near the surface. There are two
distinct zones of soil stratum that coincide with former versus most recent
fire training activities. The highest concentrations of TPH occur in the
vicinity of the active fire training area, where relatively low concentrations
of benzene, ethylbenzene, toluene, xylene, 1,1-dichloroethane, 1,2-
dichloroethene, and trichloroethene were detected in samples from soil borings
d43, d44 and d45 (SAIC, 1989).
A second, deeper zone of elevated TPH concentration is also clearly
defined in the vicinity of borings d42 and d40. As shown in Figure 14, soil
boring d42 lies within the estimated boundary of the former fire training
area, and the nearsurface soils that have elevated levels of TPH (soil boring
d40) lie on approximately the same horizon. It is likely that this horizon
was at the land surface when the former pit was in use, and that the TPH
levels detected at this horizon represent the pit and adjacent areas of
spillage. When the new pit was constructed and the old one closed, the former
fire training area was backfilled and graded to its present configuration.
Two additional organic chemicals--2 butanone and tetrachloroethene
(PCE)--were reported in the soils at Site FT-3 (SAIC, 1989). Relatively low
concentrations were detected in only two samples. All of the organic
chemicals reported to be at Site FT-3 in the IRP Phase II, Stage 2 report
(SAIC, 1989), are considered for evaluation of risk. Lead is also reported as
a potential contaminant (SAIC, 1989), and it is also discussed as to its
potential risk level.
Underground structures--such as piping--are also contaminated at Site
FT-3. Residual waste fuel and waste oil are present in these structures.
Because of the physical limitations imposed by the site, testing beneath the
Site FT-3 Underground Storage Tank was not done.
Site FT-3 Groundwater
Monitoring wells sampled during the IRP Phase II, Stage 1 and Stage 2
investigations are shown in Figure 15. The direction of groundwater flow at
Site FT-3 is northeast toward the nearby intermittent stream. Travel time to
the base boundary has been estimated at 6.1 years, corresponding to a
calculated flow velocity of 0.63 ft/day (SAIC, 1986).
During Stage 1 (SAIC, 1986), groundwater samples were collected from
three wells (MW-18, MW-19, and MW-20) in and around Site FT-3 (see Figure 15).
Monitoring well MW-18 is located upgradient of the site; MW-19 is located
between the current fire training pit and Pipe Elm Branch north of the site;
and MW-20 is located between the site and the unnamed intermittent stream
northeast of the site. Groundwater samples were analyzed for oil and grease,
metals, total organic halogens, and total organic carbon. Of the metals,
nickel was detected in MW-18 (55 ppb) and MW-20 (14 ppb) at concentrations
above the EPA Ambient Water Quality Criterion (13.4 ppb). However, the higher
concentration was detected in the upgradient well (MW-18), while the
concentration in the down gradient well (MW-20) was only slightly above the
criterion. Therefore, the higher concentration is not representative of Sice
FT-3 (SAIC, 1986). The detected concentrations of other measured analytes
11
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appeared to be nonproblematic, though total organic carbon in MW-20 (8.9 ppb)
was higher than local background levels (SAIC, 1986).
During Stage 2 (SAIC, 1989), a total of seven groundwater samples were
collected ac Site FT-3, one each from wells MW-18, MW-19, MW-20, MW-43s, MV-
43d, MW-44s, and MW-44d (Figure 15). (The letters "s" and "d" refer to
"shallow" and "deep" with respect to the Columbia aquifer.) Three VOCs--vinyl
chloride, PCE, and toluene-- were detected individually in three separate
wells--MW-19, MW-44s, and MW-44d, respectively. Vinyl chloride, which has a
Federal Maximum Contaminant Level (MCL) of 2 ppb, was detected at 6.9 ppb
(using EPA Method 624, GC/MS) and 3.4 ppb (using EPA Method 601, GC). PCE,
with a proposed MCL of 5 ppb, was detected at 0.3 ppb. Toluene, which has an
MCL of 2,000 ppb, was found to be present at 0.4 ppb. No significantly
elevated levels of metals were observed, including lead, which was detected in
only two wells at concentrations of 2 and 8 ppb, below EPA's recommended level
for Lead in Groundwater of 15 ppb.
The PCE observed in well MW-44s and the toluene in MW-44d appear to be
attributable to the most recently used fire training pit and fire training
activities conducted prior to May 1989. It is not possible to specify whether
the active fire training pit or the former, buried pit is the source of the
vinyl chloride observed in MW-19, because this well is down gradient from both
potential sources. Note that well MW-19 was sampled near the base of the
groundwater column; therefore vinyl chloride is present in the lower zone of
the aquifer. Because of this the vinyl chloride found in MW-19 is suspected
to be emanating from another source. Given the absence of volatiles in wells
MV-43s, MW-43d, and MW-20, the geology of the Site probably inhibits lateral
migration of contaminants in the groundwater. The results of the groundwater
analyses indicate that activities at the fire training area have had minimal
or no effect on water quality in the groundwater.
Site FT-3 Surface Water
During the Site visit for the IRP Phase I investigation (ES, 1983),
there was evidence of oil contamination north of the fire training area along
the bank adjacent to the drainage ditch that leads to the Pipe Elm Branch of
Little River. The residual oil appeared to be a result of overflow of the
underground oil/water separator.
Surface water and sediment samples were collected from the two streams
north and northeast of the Site during the IRP Phase II, Stage 1 investigation
(SAIC, 1986). The positions of the four sampling points (Figure 16) were
selected as follows: SW-11 and SED-d9 were located at the point where the
north stream discharges from beneath the runway; SW-12 and SED-dlO were
located in the north stream downgradient from the site; SW-13 and SED-dll were
located in the northeast stream at a location where groundwater flowing under
the site was estimated to discharge into the stream; and SW-14 and SED-dl2
were located at the confluence of the north and northeast streams. All
samples were analyzed to determine the concentrations of metals, oil and
grease, total organic halogens, and total organic carbon.
12
-------
The results of the surface water analyses indicate that activities at
the fire training area have had minimal or no effect on water quality in the
two streams. However, the sediment analyses indicated an increase in
contaminant concentrations from the upstream sample (SED-d9) to the downstream
samples (SED-dlO and SED-dll) closest to the site. Arsenic increased from 11
to 78 parts per million (ppm); cadmium, 0.67 to 9.0; chromium, 10 to 27;
copper, 6.7 to 20; nickel, 5.4 to 26; lead, 47 to 170; zinc, 18 to 76. Iron
increased from 0.52 percent to 1.8 percent. All metal concentration levels,
except those for chromium, exceeded the background levels of these metals for
Delaware and Maryland (SAIC, 1986). Oil and grease, as well as total organic
carbon, also appeared to be present at levels higher than an expected
background. Although the fire training area may have contributed in the past
(via runoff) to these contaminants in the sediment, it is evident that
upgradient sources are contributing significantly based on contamination
detected upgradient of the site (SED-d9).
13
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LEGEND:
re
Soil Boring/Semplinfl Point
Uoconcentmtion Contour
Din Flcgged to Collection Point by O*pih
Below Land Surface with the top entry
repretenting inelyiii retulu (mg/kg) for
Hmplet collected et 0 to 2 feet end the entriei
below representing retulti (mg/kg) for •mplet
collected it depth* of 2 to 4 feet. 4 to 6 feet,
•r>d 6 to 8 feet retpectivtly.
N
f
FIGURE 9
SITE FT-3: FIRE TRAINING AREA 3-
TOTAL PETROLEUM HYDROCARBONS IN SOIL
-------
LEGEND
Wetland Types:
PF01A-Paul$trine, Forested, Broadleived,
Deciduous, Temporary
R2SOWZx-Riverine, Lower Perennial,
Open Water/Unknown Bottom, Intermittently
Exposed/Permanent. Excavated
•— 0 TPH Soil Uoconcentration Contour (mjAg)
FIGURE 10
SITEFT-3: FIRE TRAINING AREA 3-
TOTAL PETROLEUM HYDROCARBON SOIL
ISOCONCENTRATION CONTOURS AND
WETLANDS ADJACENT TO SITE FT-3
-------
FORMER
AREA
CURRENT
AREA
Soil Gas Survey Area
Isoconcentntion Contour (ug/L)
FIGURE 11
SITE FT-3: FIRE TRAINING AREA 3-
TOTAL PETROLEUM HYDROCARBONS
IN SOIL GAS
-------
N
Sol Qu Survoy A/M
tooonotfltti
Qrounrfwitv
(119!)
FIGURE 12
SITE FT-3: FIRE TRAINING AREA 3-
TOLUENE IN SOIL GAS
-------
Sod
C/OM-$«c6on Location
FIGURE 13
SITE FT-3: FIRE TRAINING AREA 3-
LOCATION OF SOIL BORING PROFILE
-------
It
It
IT
It
ft
14
19
11
11
It
•1-
LEGEND:
1139 Sample Interval with
Concentration In nig/kg
........ f3rounb\yater Elevation* Estimated
from Nearby Groundwater Wells
NOTE: See Figure 1-15 for direction of cross section
120
Approximate Scale in Feet
240
FIGURE 14
SITE FT 3: FIRE TRAINING AREA 3 -
SOIL BORING PROFILE SHOWING TOTAL
PETROLEUM HYDROCARj IS DISTRIBUTION WITH DEPTH
-------
FORMER
AREA
CURRENT
AREA
LEGEND:
Monitoring Well (i-Shallow, d*Deep)
Soil Boring/Sampling Point
Soil Gas Survey Area
FIGURE 15
SITE FT-3: FIRE TRAINING AREA 3
Rl ACTIVITIES
-------
SW-14/B Ik SED-d 12
SW13AI
SED-d9 •ASED-10
SW-
Svv-nBA
SITE FT-3
SED-d11
N
LEGEND:
USAF Property Line
Drainage Channels
Unimproved Road
Phase II Site
Surface Water Monitoring Site
Sediment Monitoring Site
200
APPROXIMATE SCALE
400 feet
FIGURE 16
SITEFT-3: FIRE TRAINING AREA 3-
SAMPLING LOCATIONS FOR SURFACE WATER AND SEDIMENT
-------
Detected
Contaminant
Table 2
Contamination Detected at Site FT-3
Minimum Maximum Detection
Concentration Concentration Frecruenc^
Soil (parts per million)
Trichloroethane
Tetrachloroethane
2-Butanone
Benzene
Toluene
Xylene
Ethyl benzene
1 , 1-Dichloroethane
1 , 2 -Dichloroethane
Lead
TPH
Groundvater (parts
Vinyl chloride
Tetrachloroethane
Toluene
0.0032
0.041
0.032
0.014
0.027
0.015
0.008
0.008
0.59
1.1
120
per billion)
6.9
0.3
0.4
0.009
0.041
0.34
0.014
28
19
8.7
0.008
0.59
200
4,000
6.9
0.3
0.4
2/57
1/57
2/56
1/57
3/57
4/57
4/57
1/57
1/57
54/54
10/47
1/7
1/7
1/7
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VI SUMMARY OF SITE RISKS
Contaminants of Concern
Table 2 presents the contaminants detected in soil and groundwater
(SAIC, 1989). These contaminants were examined using several criteria
(toxicity, measured concentrations, frequency of detection, and potential
human exposure) for identification of contaminants of concern. Because fire
training activities have had a minimal effect on groundwater quality and
groundwater will be further studied as part of the base-wide investigation,
groundwater was not included in the summary of Site risks. Although fire
training activities may have contributed to contaminants in the downgradient
streams, surface water and sediment are not being considered in this summary
of site risks, because it was evident from data collected during 1RP Phase II,
Stage 1 (SAIC, 1986) that upgradient sources appear to have contributed
significantly more contamination, and streams will be studied as part of the
base-wide study.
Based on EPA's Risk Assessment Guidance several contaminants detected in
soil can be eliminated from further consideration because their frequency of
occurrence is less than 5 percent (USEPA, 1989). These contaminants include
trichlorethane, tetrachloroethane (PCE), 2-butanone, benzene,
1,1-dichloroethane, and 1,2-dichloroethane (Table 2). However, benzene is a
Group A, human carcinogen, and, therefore, must be retained. Several
detections of acetone and one of 2-butanone were eliminated from consideration
based on quality control criteria, because the trip and method blanks were
also contaminated with these compounds (SAIC, 1989).
Based on the aforementioned criteria, the contaminants of concern
identified in soil at Site FT-3 are:
benzene
toluene
xylenes (total)
ethylbenzene
lead
Total Petroleum Hydrocarbons (TPH)
Exposure Assessment
Available information on the environmental fate and transport of
contaminants of concern in soil at Site FT-3 is presented in Table 3. The
principal fate of all contaminants of concern, except lead, in surficial .soil
at Site FT-3 is volatilization to the atmosphere where destruction occurs via
indirect photolysis (USEPA, 1979). In aerated soils at greater depth,
biodegradation is important as a mechanism for environmental destruction. The
principal fate of lead is adsorption to the soil. Some leaching into the
groundwater can also be expected for all contaminants of concern.
Military personnel and maintenance staff at Site FT-3 have been selected
as the receptor group at greatest risk of exposure to contaminants in surface
soil. This is the only receptor group having significant contact with the
14
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site. The pathways for potential exposure are incidental soil ingestion,
inhalation of soil-generated dust, and dermal absorption of soil constituents.
Because estimates of exposure via dermal absorption include many uncertainties
associated with diffusion of contaminants through both soil and skin, exposure
via this pathway is considered only qualitatively (USEPA, 1989). These three
pathways are relevant to future use, as well as current use, of the Site FT-3
area. Exposure to contaminants was adjusted to a lifetime exposure by
assuming a 20-year career in a 70-year lifetime.
Toxicity Assessment
The relationship between the extent of exposure to a contaminant and the
potential for adverse effects was evaluated during the toxicity assessment
process. Cancer potency factors (CPFs) were identified for potential
carcinogenic contaminants, and reference doses (RfDs) were identified for
chemicals exhibiting noncarcinogenic effects. CPFs and RfDs for the
contaminants of concern used for the toxicity assessment are presented in
Table 4.
Cancer potency factors (CPFs) have been developed by EPA's Carcinogenic
Assessment Group for estimating excess lifetime cancer risks associated with
exposure to potentially carcinogenic chemicals. CPFs, which are expressed in
units of (mg/kg-day)-' , are multiplied by the estimated intake of a potential
carcinogen, in mg/kg-day, to provide an upper-bound estimate of the excess
lifetime cancer risk associated with exposure at that intake level. The term
"upper bound" reflects the conservative estimate of the risks calculated from
the CPFs. Use of this approach makes underestimation of the actual cancer
risk highly unlikely. Cancer potency factors are derived from the results of
human epidemiological studies or chronic animal bioassays to which animal-to-
human extrapolation and uncertainty factors have been applied.
Reference doses (RfDs) have been developed by EPA for indicating the
potential for adverse health effects from exposure to chemicals exhibiting
noncarcinogenic effects. RfDs, which are expressed in units of mg/kg-day, are
estimates of lifetime daily exposure levels for humans, including sensitive
individuals. Estimated intakes of chemicals from environmental media (e.g.,
the amount of a chemical ingested from contaminated drinking water) can be
compared to the RfD. RfDs are derived from human epidemiological studies or
animal studies to which uncertainty factors have been applied (e.g., to
account for the use of animal data to predict effects on humans). These
uncertainty factors help ensure that the RfDs will not underestimate the
potential for adverse noncarcinogenic effects to occur.
Risk Characterization
Excess lifetime cancer risks for Site FT-3 were determined by
multiplying the daily intake of chemicals from environmental media by the
cancer potency factor. These risks are probabilities expressed in scientific
notation (i.e. 1E-6). An excess lifetime cancer risk of 1E-6 indicates that
an individual has a one in a million additional chance of developing cancer as
a result of site-related exposure to a carcinogen over a 70-year lifetime.
For known or suspected carcinogens, acceptable exposure levels are generally
15
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concentration levels that represent an excess upper bound for lifetime cancer
risk to an individual of between 1E-4 and IE-6, however, the point of
departure, as described in the NCP, is considered to be IE-6. See 40 CFR
300.430(2)(i)(A)(2).
The estimated excess lifetime cancer risk for each of the exposure pathways is
presented below:
Exposure to Site FT-3 Soils
ROUTE OF EXPOSURE
POPULATION INGESTION INHALATION
Military personnel/ 1.1E-10 4.9E-14
Maintenance Staff
Potential concern for noncarcinogenic effects of a single contaminant in
a single medium is expressed as the Hazard quotient (HQ) (i.e., the ratio of
the estimated intake derived from the contaminant concentration in a given
medium to the contaminants reference dose). The HQs for all contaminants in a
medium are added to obtain the Hazard Index (HI). The HI provides a reference
point for gauging the significance of multiple contaminant exposures within a
single medium or across media. An HI less than or equal to 1 indicates that
there is no significant risk of adverse health effects.
The His derived for the soil medium are summarized below:
Exposure to Site FT-3 Soils
ROUTE OF EXPOSURE
POPULATION INGESTION INHALATION TOTAL
Military Personnel/ 7.1E-05 1.2E-08 7.0E-05
Although possible groundwater remediation is not part of this ROD, an
exposure pathway was considered for possible contaminant migration from Site
FT-3 soil to groundwater.
A mathematical model which calculates the level in soil that would be
protective of groundwater was used for Site FT-3 contaminants of concern.
This model was developed to estimate the point at which contaminant
concentrations in the soil will produce groundwater contaminant concentrations
above acceptable levels. The resultant concentrations in soil can be use.d .as
soil cleanup levels.
Benzene was selected as the contaminant of concern to calculate an
acceptable soil level. Benzene is a known human carcinogen, has a fairly high
water solubility, and is a common constituent in waste fuels and oils. The
mathematical computation produced a value for benzene in soil of approximately
5 ppm, significantly above the highest concentration at the Site, 31 ppb.
It is evident from Table 4 and the groundwater protection model that the
risks posed by site FT-3 soil to dermal contact, accidental ingestion, and
contaminant transport to groundwater are well below EPA guidance levels.
16
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Fire and Explosion Threat
Site FT-3 structures contain residual waste oil and waste fuel. The
residual waste oil and waste fuel is flammable. While the waste oil/fuel does
not pose an unacceptable carcinogenic risk and/or noncarcinogenic exposure
risk, the existence of this residual waste oil and waste fuel poses a threat
of fire and explosion.
17
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Table 3
Environmental Fate and Transport of
Contaminants of Concern at Site FT-3
Contaminants
of Concern
Sorption
Biodeqradation
Principle Environmental Fate
Benzene
Toluene
Xylene
Ethylbenzene
Lead
Moderately mobile
in soil.
Moderately mobile
in soil.
Moderately mobile
in soil.
Slightly mobile
in soil.
Slightly mobile
in soil
Degrades slowly under an
aerobic environment, but
is considered persistent
in soils sufficiently deep
to be depleted of oxygen.
Easily degraded in an aerobic
environment, but much slower
degradation is possible in an
anaerobic aguifer.
Degraded under aerobic
conditions but persistent
in an anaerobic aquifer.
Rapid degradation occurs in
aerobic environments, but
this process does not in
anaerobic aquifers.
Biodegradation of lead is
not significant.
Principle fate is volati-
lization and destruction in
the atmosphere, but can
also be leached into the
groundwater.
Principle fate in surficial
soil or water is volatili-
zation and destruction in the
atmosphere, but
biodegradation and
leaching into groundwater can
contribute to environmental
degradation.
See Principle fate of
benzene.
Principle fate is volati-
zation followed by destruc-
tion in the atmosphere;
however, leaching into
groundwater may also occur.
Principle fate is adsorption
to soil.
Petroleum
Hydrocarbons
Moderately mobile
in soil.
Degrades under aerobic
conditions.
See Principle fate of
benzene.
-------
Table 4
Cancer Potency Factors and Reference Doses
Used in Site FT-3 Risk Characterization
Contaminant of
Concern CPFf(mq/kq/day)1(a) RfD (mg/kg/day)(b)
Oral Inhalation Oral Inhalation
Benzene .0029 .0029
Toluene .3 2.0
Xylene 2.0 .3
Ethyl benzene .1 .1
Lead NA(c)
TPH NA(d)
(a) Cancer Potency Factor for carcinogenic effects.
(b) Reference dose for noncarcinogenic effects.
(c) EPA refernce dose for lead has been withdrawn. Acceptable soil levels are calculated using the
EPA biokenetic model on a site-specific basis. Typical soil cleanup levels for residential areas
are in the range of 200 ppm lead.
(d) Cleanup levels in soil for TPH are based on the risk to human health and the environment from
carcinogenic compounds, such as benezene, the non-carcinogenic effect from compound, such as
toluene, and use of the area, (i.e. residential, non-residential) on a site-specific basis. Levels
tor TPH in soil at FT-3, (Non-residential, restJcted access), were based on the risk posed to
workers from these compounds.
-------
VII DESCRIPTION OF ALTERNATIVES
Actual or threatened releases of hazardous substances from the site, if
not addressed by implementation of the response action selected in this ROD,
may present an imminent and substantial endangerment to public health and the
environment.
A number of remedial alternatives were developed to significantly reduce
the risk to public health and the environment from the Site FT-3 Soil and
Structures. The following sections briefly summarize each of these
alternatives. The Present Worth Cost was calculated using the capital cost of
the remedy plus, the cost of 20 years Operation and Maintenance (O&M).
Alternative 1: No Action
Evaluation of the No Action Alternative is required by the National Oil
and Hazardous Substances Contingency Plan (NCP). This alternative serves as a
point of reference for comparing all other alternatives. If other
alternatives offer no substantial advantages over the no action alternative,
no action may be considered appropriate. Total cost for this alternative
is $0.
Alternative 2: Capping and a Perimeter Slurry Wall, and Decontamination.
Removal, and Offbase Disposal of Piping/Structures
This alternative involves the construction of a composite cap over the
contaminated soils and a slurry cutoff wall around the entire perimeter of t'r.~
cap, to be implemented after the decontamination, removal, and offbase
disposal of piping/structures.
Decontamination of the piping/structures will require removal of any
residual liquid, sludge, and/or solid material from within these units. .
Removal of the underground piping with the appropriate excavation equipment
prior to cleanup will facilitate decontamination activities. Pumps, manual
labor, and other appropriate mechanical equipment will be used to clean the
piping/structures. Steam-cleaning will then be used to decontaminate the
piping/structures. The material removed from these units and the solutions
resulting from decontamination procedures will be collected in tanker trucks,
vacuum trucks, 55-gallon drums, or other suitable containers prior to shipment
and offbase disposal. Analysis of the waste materials will be performed to
determine the appropriate disposal and/or treatment requirements for the
collected material. The UST and the oil/water separator will then be removed
with the appropriate excavation equipment. All of the decontaminated piping
and structures will then be transported and disposed of offbase at a sanitarv
landfill or salvage yard.
A 2-foot-wide, 50-foot-deep, and 1,600-foot-long soil-bentonite slurry
cut-off would then be installed to isolate the contaminated soils from the
surrounding shallow groundwater. This technique involves excavating a trench.
and filling it with slurry that would keep the trench open with vertical
sides, even below the water table. The slurry would be composed of bentor.ite
18
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clay and water. The excavation of the trench would be performed from the
ground surface using conventional equipment capable of achieving the required
trench widths and depths. After the trench has been excavated to its final
depth, a mixture of soil and bentonite would be placed in the trench,
resulting in the displacement of the bentonite slurry and the formation of
the cutoff wall. The 50-foot depth of the slurry wall will be sufficient to
anchor the wall in the stiff, low-permeability clay layer of the Kirkwood
Formation that was encountered at the bottom of the borings drilled for the
deep wells at the site (SAIC, 1989). This anchoring would be necessary to
prevent any groundwater from flowing into or out of the water table aquifer
under Site FT-3.
A composite cap consisting of a geomembrane, a drainage layer, and a
soil cover would then be placed over the existing contaminated soils inside
the slurry cutoff wall. Any excess soil excavated from the slurry trenches
that cannot be reused during the construction of the slurry wall would be
spread over the area to be covered by the cap, thus ensuring that any
contaminants in the soil are contained by the cap. The surface of the cap
should slope (1 to 3 percent) to prevent ponding of water, and the cap should
extend over the slurry wall and, if possible, be anchored into the wall.
Before installing the cap system, the Site would be graded and large
objects (e.g., boulders, concrete slab fragments), if present, would be
removed; then a layer of nonwoven geotextile fabric would be placed over the
site. This fabric layer would protect the overlying 60-mil HDPE georaembrar.e ,
which would serve as an impermeable barrier over the contaminated soils, from
puncturing.
A drainage layer would be placed on top of the geomembrane. This layer
would be installed over the entire exposed cap and would drain any water that
infiltrates through the soil cover.
A 2-foot-thick layer of clean soil would be placed on top of the
drainage layer and seeded. Vegetation would prevent erosion of the soil
layer, which would be graded to prevent run-on and promote runoff.
This alternative would have to comply with RCRA subtitle C requirements
for closure of land disposal units.
This alternative would take approximately 4 months to implement and the
Present Worth Cost is $1,668,500.
Alternative 3: Excavation. Onbase Landfarming. and Onsite Treated Soil
Disposal, and Decontamination. Removal, and Offbase Disposal of
Piping/Structures
This alternative includes decontamination, removal, and disposal of
existing piping/structures followed by excavation and aboveground
bioremediation (landfarming) of the contaminated soils at Site FT-3.
Following treatment, the soils would be used as backfill material at the
excavated Site.
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Decontamination of the piping/structures will require removal of any
residual liquid, sludge, and /or solid material within these units. Removal
of the underground piping with the appropriate excavation equipment prior to
cleanup will facilitate decontamination activities. Pumps, manual labor, and
other appropriate mechanical equipment will be used to clean the
piping/structures. Steam-cleaning will then be used to decontaminate the
piping/structures. The material removed from these units and the solutions
resulting from decontamination procedures will be collected in tanker trucks,
vacuum trucks, 55-gallon drums, or other suitable containers prior to shipment
and offbase disposal. Analysis of the waste materials will be performed to
determine the appropriate disposal and /or treatment requirements for the
collected material. The UST and the oil/water separator will then be removed
with the appropriate excavation equipment. All of the decontaminated piping
and structures will then be transported and disposed of offbase at a sanitary
landfill or salvage yard.
Following decontamination, removal, and disposal of the Site FT-3
piping/structures, excavation and treatment activities associated with the
Site FT-3 contaminated soils would begin. The area to be excavated is
approximately 2.6 acres. Excavation would extend to depths ranging from 2 to
8 feet or to the water table, whichever is shallower. The total amount of
soil to be excavated from Site FT?3 is estimated to be 19,000 cubic yards in
place. Due to the uncohesive nature of some of the soils at Site FT-3,
sloping of the excavation boundaries may be necessary to prevent sloughing
around the excavation perimeter.
Conventional excavation equipment would be used to remove the Site FT-3
contaminated soils. Light spraying of water will be used to control dust
generated during excavation of dry soils. Construction of a temporary silt
fence around the excavation boundaries during excavation and backfilling
activities would prevent erosion of the Site.
The excavated soil would be placed in dump trucks and taken to the'on-
base location that has been selected for the aboveground landfarming process,
Pilot-scale tests conducted by a qualified contractor prior to remediation
will be used to determine the preparation requirements for the selected
treatment site. The treatment site will be cleared of surface debris, large
rocks, and brush. Furthermore, the area selected will be large enough to
accommodate the estimated 19,000 cubic yards of soil expected to be removed
from Site FT-3. Six to seven acres of land will be required to treat the
quantity of contaminated soil anticipated from Site FT-3. The treatment site
will be graded, provided with a berm for run-on and runoff control and/or
collection, and, if necessary, provided with nutrients, fertilizers,
microbes, and/or other agents necessary to enhance the biodegradation process.
The soils would be spread out and treated on a liner that will prevent contact
with the underlying soils. Results of pilot-scale tests will be used
determine the proper ratio of nutrients, water, air, and oxidizing or reducing
agents to be added to the soils that will ensure optimal conditions for
degradation of the contaminants. Runoff from the treatment site will be
collected and, if necessary, reapplied to the treatment site until the
concentrations of contaminants in the liquid runoff are below acceptable
20
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levels. Offbase treatment of this liquid may be necessary if reapplication
proves ineffective.
Sampling and analysis of the treated soils will be conducted during
bioremediation to monitor the progress of the treatment process. Once
acceptable contaminant concentrations in the soils are achieved, the treated
soils will be collected with the appropriate heavy construction equipment,
loaded into dump trucks, and transported back to Site FT-3. The treated soil
would then be backfilled and compacted in the excavated areas of the site.
Both the treatment site and Site FT-3 would then be seeded to promote
revegetation. The treatment site soils would be sampled and analyzed for TPH
prior to and following the bioremediation process to ensure that the site is
returned to its original condition. Any additional treatment required to
ensure the soils are returned to their original condition will be performed.
Groundwater may seep into the Site FT-3 excavated area during the
excavation and landfarming process. This water would be sampled and, if
contaminated, pumped into a tank truck and shipped offbase for treatment at a
RCRA permitted facility. The quantity of water from groundwater seeping is
estimated to be less than 15,000 gallons. Any excavated wet soils would be
stockpiled, on a liner, in the vicinity of the excavation to allow for
dewatering prior to on-base treatment by landfarming. The water from' the
stockpiled soils would then be directed to drain back into the excavated area
for collection and recovery as necessary.
This alternative would comply with RCRA subtitle C requirements for land
treatment.
This alternative would take approximately 6 to 12 months to implement
and the Present Worth Cost is $1,597,300.
Alternative 4: Excavation and Disposal of Soils in an Offbase RCRA Landfill.
and Decontamination. Removal, and Offbase Disposal of Piping/Structures
This alternative includes decontamination, removal, and disposal of the
existing piping/structures at Site FT-3 followed by excavation,
transportation, and offbase disposal of the contaminated site soils in a RCRA-
permitted landfill.
Decontamination of the piping/structures will require removal of any
residual liquid, sludge, and /or solid material from within these units.
Removal of the underground piping with the appropriate excavation equipment
prior to cleanup will facilitate decontamination activities. Pumps, manual
labor, and other appropriate mechanical equipment will be used to clean the
piping/structures. Steam-cleaning will then be used to decontaminate the
piping/structures. The material removed from these units and the solutions
resulting from decontamination procedures will be collected in tanker trucks,
vacuum trucks, 55-gallon drums, or other suitable containers prior to shipment
and offbase disposal. Analysis of the waste materials will be performed to
determine the appropriate disposal and /or treatment requirements for the
collected material. The UST and the oil/water separator will then be removed
with the appropriate excavation equipment. All of the decontaminated piping
21
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and structures will then be transported and disposed of offbase at a sanitary
landfill or salvage yard.
Following decontamination, removal, and disposal of the
piping/structures, excavation of the Site FT-3 soils in preparation for
offbase transport and disposal would begin. Conventional excavation equipment
would be used to remove the Site FT-3 contaminated soils, and light spraying
of water will be used to control dust generated during excavation of dry
soils. Construction of a temporary silt fence around the excavation
boundaries during excavation and back-filling activities would prevent erosion
of the Site soils.
The excavated soil would be containerized in rolloff boxes and loaded
onto flatbed trailer trucks for bulk shipment. Arrangements with the RCRA
landfill chosen to dispose of the soils will be necessary prior to shipment.
The RCRA landfill will most likely require additional sampling and analysis of
the soils, such as for ignitability, prior to acceptance. Following
excavation, Site FT-3 would be backfilled with clean fill, graded, and seeded.
As with Alternative III, any groundwater seeping into the excavated area
will be sampled and, if contaminated, pumped into a tank truck and shipped
offbase for treatment at a RCRA permitted facility. The quantity of
groundwater seeping into the excavated area prior to backfilling is estimated
to be less than 15,000 gallons. Any excavated wet soils would be stockpiled,
on a liner, in the vicinity of the excavation to allow dewatering prior to
offbase shipment and disposal. The water from the stockpiled soils would be
channeled back into the excavated area for collection and recovery as
necessary.
This alternative would comply with transportation and disposal standards
(40 CFR Part 264, Subpart B) and landfill standards (40 CFR Part 264,
Subpart N).
This alternative would take approximately 3 to 5 months to implement and
the Present Worth Cost is $7,336,300.
Alternative 5: Decontamination. Removal, and Offbase Disposal of
Piping/Structures. Sampling Soil Around UST. Soil Cover Over Site FT-3
This alternative includes decontamination, removal and disposal of
existing piping/structures, followed by testing around the UST, and placement
of a soil cover over Site FT-3.
Residual liquid, sludge, and solid materials will be removed from the
piping/structures at Site FT-3 using pumps, manual labor, and other
appropriate mechanical equipment. The underground piping will most likely
require removal with a backhoe or other suitable equipment prior to cleanup.
The liquid sludge, and solid materials will be collected in a tanker truck, 55
gallon drums, or other suitable containers and shipped off site to a disposal
facility permitted to treat or dispose of the collected waste. Analysis of
the waste materials will be performed to determine the appropriate disposal
and/or treatment requirements.
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Following removal of residual materials, remaining contamination could
be removed using high-pressure (up to 3,000 psi) and high-temperature steam
(or hot water) cleaning equipment in combination with a suitable cleaning
agent. This solution will also require collection and offbase disposal and/or
treatment.
The underground structures, which include a UST and oil/water separator,
would be removed by means of a hydraulic backhoe or other suitable equipment.
The associated piping will most likely require removal prior to cleanup. The
UST and oil/water separator, along with the decontaminated aboveground
dumpsters and previously removed and cleaned piping, would then be shipped
off-site for disposal at a sanitary landfill or salvage yard.
The excavated areas at Site FT-3 would be backfilled and graded
following removal of the piping/structures. A soil cover would then be placed
on Site FT-3 and the area revegetated.
This alternative would comply with transportation and disposal standards
(40 CFR Part 264, Subpart B) and RCRA and Delaware UST requirements for
disposal of liquid waste.
This alternative would take approximately 2 months to implement and the
Present Worth Cost is $100,000.
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VIII SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The Air Force has evaluated each of the remedial alternatives developed
for Site FT-3 with respect to nine specific criteria listed below.
Overall Protection of Human Health and the Environment--addresses whether or
not a remedy will (1) cleanup a site to within the risk range; (2) result in
any unacceptable impacts; (3) control the inherent hazards (e.g., toxicity ar.c
mobility) associated with a site; and (4) minimize the short-term impacts
associated with cleaning up the site.
Compliance With ARARs--addresses whether or not a remedy will meet all of the
applicable or relevant and appropriate requirements of other environmental
statutes and/or provide grounds for invoking a waiver.
Long-Term Effectiveness and Permanence--refers to the ability of a remedy to
maintain reliable protection of human health and the environment over time,
once cleanup goals have been met.
Reduction of Toxicity, Mobility, or Volume Through Treatment--refers to the
anticipated performance o.f the treatment technologies that may be employed in
a remedy.
Short-Term Effectiveness--refers to the period of time needed to achieve
protection, and any adverse impacts on human health and the environment that
may be posed during the construction and implementation period until cleanup
goals are achieved.
Implementability--describes the technical and administrative feasibility of a
remedy, including the availability of materials and services needed to
implement the chosen solution.
Cost-- includes the capital for materials, equipment, etc., and the operation
and maintenance costs.
Support Agency Acceptance--indicates whether, based on their review of the RI ,
FFS, and the Proposed Plan, EPA and DNREC concur with, oppose, or have no
comment on the preferred alternative.
Community Acceptance--will be assessed in the Record of Decision following a
review of the public comments received on the RI, FFS, and the Proposed Plan.
The following sections present a brief discussion of each of the
evaluation criteria and a comparative analysis of each of the remedial
alternatives based on the nine criteria. Each of the action alternatives will
address the principle threat, fire and explosion, posed by Site FT-3, however.
because the risk to human health and the environment from Site FT-3 soils is
below risk based levels, (see Section VI Summary of Site Risks), there is no
need to remediate Site FT-3 soils.
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1) Overall Protection of Human Health and the Environment
This criterion addresses whether or not a remedy will (1) cleanup a site
to within the risk range; (2) result in any unacceptable impacts; (3) control
the inherent hazards (e.g., toxicity and mobility) associated with a site; and
(A) minimize the short-term impacts associated with cleaning up the site.
The primary human health risk associated with the Site is from onsite
piping and structures. This risk is the risk of fire and explosion posed by
residual waste oil and waste fuel.
The no action alternative (Alternative 1) does not abate the risk of
fire and explosion. Therefore, Alternative 1 is judged to be unprotective of
human health and the environment and will not be discussed further.
The four action alternatives under consideration were found to provide
high levels of protectiveness. Alternatives 2, 3, 4, and 5 would eliminate
the threat of fire and explosion posed by the piping/structures through
removal and decontamination of the piping structures.
2) Compliance With ARARs
This criterion addresses whether or not a remedy will meet all of the
applicable or relevant and appropriate requirements of other environmental
statutes and/or provide grounds for invoking a waiver.
A complete listing of all site-related action and location specific
ARARs is presented in Table 5. All of the action alternatives will meet
ARARs, and no waivers will be required. The creation of an on-site landfill
in Alternative 2 would have to meet all applicable State and Federal
regulations regarding closure and post-closure. The Occupational Health and
Safety Act will be applicable for the protection of worker safety during
implementation of any of the remedial alternatives. Offsite disposal would
have to meet Hazardous Materials Transportation regulations. Onsite
landfarming would have to meet emissions standards. Alternatives involving
offsite disposal of residual sludge and decontamination water will follow RCRA
Subpart 268 if testing determines the waste to be a RCRA waste under RCRA
Subpart 261. Otherwise the waste will be subject to Delaware UST regulations.
3) Long-Term Effectiveness
This criterion refers to the ability of a remedy to maintain reliable
protection of human health and the environment over time, once cleanup goals
have been met.
Alternatives 2, 3,4 and 5 would remove/decontaminate the onsite
piping/structures, eliminating the fire/explosion threat, and also greatly
reducing the possibility of leaching of contaminants, thereby providing
adequate long-term protection of human health and the environment.
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4) Reduction of Toxicitv. Mobility, and Volume
This criterion refers Co the anticipated performance of Che treatment
technologies that may be employed in a remedy.
The four action alternatives employ some form of treatment or
containment process to reduce toxicity, mobility, and/or volume in the
affected media.
Since the primary exposure pathway associated with Site FT-3 is the
threat of fire/explosion to onsite workers, Alternatives 2, 3, 4, and 5 will
all reduce this risk with respect to the primary exposure pathway.
5) Short-Term Effectiveness
This criterion refers to the period of time needed to achieve
protection, and any adverse impacts on human health and the environment that
may be posed during the construction and implementation period until cleanup
goals are achieved.
Alternative 2, 4 and 5 could be implemented in a similar period of time
and within a shorter period of time, respectively, than Alternative 3, thereby
resulting in reduced construction/implementation-related impacts.
Alternatives 3 and 4 would both require the handling of a large quantity of
excavated contaminated soils onsite, thereby exposing site workers and the
public to wastes to a greater degree than would Alternative 2 and 5. In
addition Alternative 4 also requires transport of these materials on public
roads, which could result in potential human exposure. Therefore, with
respect to short-term effectiveness Alternatives 2 and 5 are more protective
than Alternatives 3 and 4.
6) Implementabilitv
This criterion describes the technical and administrative feasibility of
a remedy, including the availability of materials and services needed to
implement the chosen solution.
The four action alternatives are technically feasible. However,
Alternatives 2 and 5 would be easier to implement than alternatives 3 and 4,
because, alternatives 3 and 4 include greater material handling requirements
associated with excavation and treatment of soil in Alternative 3, and
excavation, transportation, and disposal in a RCRA landfill in Alternative 4.
Furthermore, Alternative 4 may be difficult to implement because of the
difficulty in identifying and selecting a RCRA landfill that is willing to
accept the large quantity of soil to be excavated from Site FT-3. Therefore,
Alternative 4 has a disadvantage over Alternative 3, which would use onsite
treatment.
7) Cost
This criterion addresses the capital for materials, equipment, etc., and
the O&M costs.
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Assuming a net present worth (NPW) cost including 20 years of 0 & M
costs, Alternative U would be the most expensive alternative to implement with
a NPW cost of $7,336,300. Alternatives 2, and 3 are comparable with NPW costs
of $1,668,500 and $1,597,300 respectively. However, due to the relatively low
risk posed by site soils, this cost can not be justified. Alternative 5 has a
low NPW cost of $100,000 and removes the primary threat posed by the Site.
Therefore, Alternative 5 is the most cost effective.
The Air Force has selected Alternative 5. It offers the most cost-
effective solution, while still providing adequate protection of human health
and the environment.
8) Support Agency Acceptance
This criterion indicates whether, based on their review of the RI, FFS,
and the Proposed RAP, the support agencies concur with, oppose, or have no
comment on the preferred alternative.
EPA and DNREC concur with the selected remedy.
9) Community Acceptance
This criterion assesses the public comments received on the RI, FFS, and
the Proposed Plan.
A public meeting was held on August 30, 1990, at the Dover Air Force
Base Officer's Club. This meeting lasted approximately one hour, and the
members of the public in attendance were able to have all of their questions
about the Site answered. Written comments were received during the public
comment period. The major concerns of the community involve contamination
from other areas at Dover AFB. The Responsiveness Summary, Section XI,
responds to all public comments received.
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TABLE 5
Standard, Requirement,
Criteria, or Limitation
ARARs
Citation
Retained Discussion
Subtitle D land disposal
criteria
(40 CFR Part 257)
YES
Establishes criteria for solid waste
disposal facilities.
Subtitle C landfill
closure and post-
closure
Land disposal
restrictions
Thermal treatment
NPDES requirements
National Ambient Air
Quality Standards
Occupational Safety
and Health Admini-
stration Requirements
U.S. Department of
Transportation
Regulations
Conservation of Wildlife
Resources
(40 CFR Part 264)
(40 CFR Part 268)
YES
YES
(40 CFR Part 240) NO
(40 CFR Parts 122-124) NO
(40 CFR Part 50) YES
(29 CFR Part 1910) YES
(49 CFR Parts 170-179) YES
(Fish & Wildlife NO
Coordination Act)
RCRA regulations for landfill closure
and post-closure.
Restricts land disposal of
contaminated soil.
Guidelines for incineration of waste.
Regulates discharges to surface
water.
Regulates emission from Remedial
Actions.
Worker safety at Remedial Action
sites.
Regulations governing transportation
of contaminated soils and wastes.
Protection of endangered species.
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Table 5 (cont'd)
Standard, Requirement,
Criteria, or Limitation Citation Retained Discussion
Flood Plain and Wildlife (40 CFR Part 6) YES Regulates remedial actions
Protection in floodplain and wetlands.
Underground Storage Tank (Del Code, Title 7, YES Establishes guidelines for
(UST) Regulations Chapter 161) cleanup of UST)
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IX DESCRIPTION OF THE SELECTED REMEDY
Based upon considerations of the requirements of CERCLA and on the
detailed evaluation of the alternatives, the Air Force has determined that
Alternative 5, Decontamination, Removal and Offbase Disposal of
Piping/Structures, Sampling Soil the around UST, and a Soil Cover is the most
appropriate remedy for soil and structures at Site FT-3, Dover AFB, Delaware.
The underground piping will require removal with a backhoe or other
suitable equipment prior to cleanup. The underground structures, which
include an UST and oil/water separator, will be removed by means of a
hydraulic backhoe or other suitable equipment.
Residual liquid, sludge, and solid materials will be removed from the
piping/structures at Site FT-3 using pumps, manual labor, and other
appropriate mechanical equipment. The liquid sludge, and solid materials
will be collected in a tanker truck, 55 gallon drums, or other suitable
containers and shipped offbase to a disposal facility permitted to treat or
dispose of the collected waste. Analysis of the waste materials will be
performed to determine the disposal and/or treatment requirements. If, after
analysis, the waste is determined to be a RCRA hazardous waste, RCRA
regulations for disposal of liquid waste will be followed. If, however, the
waste is not a RCRA hazardous waste, Delaware Underground Storage Tank
regulations for disposal of the waste will be followed.
Following removal of residual materials, remaining contamination from
the piping and structures could be removed using high-pressure (up to 3,000
psi) and high-temperature steam (or hot water) cleaning equipment in
combination with a suitable cleaning agent. This solution will also requirs
collection and offbase disposal and/or treatment. If, after analysis, the
waste is determined to be a RCRA hazardous waste, RCRA regulations for
disposal of liquid waste will be followed. If, however, the waste is not a
RCRA hazardous waste, Delaware Underground Storage Tank regulations for
disposal of the waste will be followed.
The decontaminated UST, oil/water separator, aboveground dumpsters, and
piping, would then be disposed of at a sanitary landfill or salvage yard.
Soils surrounding the underground structures will be tested to determine if
contamination exists above acceptable risk based levels.
The excavated areas at Site FT-3 will be backfilled and graded after
evaluation of soil analysis. A soil cover will then be placed on Site FT-3
and the area revegetated.
The rationale for selection of this alternative is based on four
principles. First, the baseline risk assessment (BRA) conducted in
association with the RI/FFS indicates that Site FT-3 appears to have minimal
or no impacts on human health and the surrounding environment. EPA's own
calculation of Site risks indicate that human health risks from exposure to
contaminated soils at Site FT-3 are well below the EPA target cancer risk
range of 10'* to 10'*, and that the soil at Site FT-3 is having a minimal
effect on groundwater in the area. Second, by removal of the site
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piping/structures and residual waste fuel/oil in the piping/structures the
major known and potential sources of fire and explosion threat associated with
Site FT-3 are removed. Third, there is currently no indication that Site soil
contaminants are migrating off base via nearby surface water and/or sediment
pathways, and the limited groundwater contamination in the vicinity of Site
FT-3 originates from sources upgradient of the site. Finally, the base-wide
groundwater monitoring study for Dover AFB will serve to identify future
migration (if any) of Site FT-3 contaminants in groundwater and surface water
and determine the need (if any) for future additional monitoring or remedial
actions at Site FT-3. *
In addition, pursuant to Section 120(h) of CERCLA, 42 U.S.C. Section
9620(h), appropriate notice regarding hazardous substance activity must be
given if the Air Force transfers land at the Site.
Cost Estimate for Alternative 5
Cost Item
Remove and dispose of piping/structures $ 25,000
Remove and dispose of residual $ 45,000
material and decontamination
of piping/structures
Sampling and Analysis $ 10,000
of Soil around UST
Backfill structures and $ 15,000
Soil cover and reseeding
Total O&M Cost $ 5.OOP
including grass cutting (adjusted
net present worth value)
Total Cost $100,000
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X STATUTORY DETERMINATIONS
The Air Force's primary responsibility at Dover AFB is to implement
remedial actions that are protective of human health and the environment.
Section 121 of CERCLA, 42 U.S.C. Section 9621, also establishes several other
statutory requirements and preferences. The selected remedy must be cost
effective and utilize a permanent solution to the maximum extent practicable.
The selected remedial action must comply with all applicable or relevant and
appropriate requirements set forth by State and Federal environmental
regulations, unless such requirements are waived in accordance with CERCLA
Section 121, 42 U.S.C. Section 9621. Finally, the Air Force must consider the
statutory preference for remedial actions that permanently reduce the
toxicity, mobility, and volume of the site-related wastes. The following
sections discuss how the selected remedy meets the statutory requirements and
preferences set forth by Section 121 of CERCLA.
Protection of Human Health and the Environment
The risk posed by the Site was identified as the fire and explosion
threat from the Site structures. This is the only significant exposure
pathway having an adverse effect on human health and the environment. The
selected remedy would protect human health and the environment by eliminating
the fire and explosion threat by removal of the Site structures.
Additionally, implementation of this alternative is not anticipated to result
in any adverse short-term risks or cross-media impacts.
Compliance with Applicable or Relevant and Appropriate Requirements
The selected remedial action will comply with all applicable or relevant;
and appropriate location-, action-, and chemical-specific requirements
(ARARs). A complete listing of ARARs developed during the comparative
analysis of alternatives is presented in Table 5, the ARARs specific to the .
selected remedy are presented below.
• Chemical-specific ARARs:
None
• Location-specific ARARs:
40 CFR Part 6 - Flood Plain and Wildlife Protection
regulations are applicable for remedial actions in a
floodplain.
• Action-specific ARARs:
40 CFR Part 50 - National Ambient Air regulations for air
and dust emissions from remedial actions.
29 CFR Part 1910 - Occupational and Worker Safety at
Remedial Action sites.
Del. Code, Title 7, Chapter 161 Underground Storage Tank
Regulations establishing guidelines for cleanup of UST.
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40 CFR Part 268 - RCRA guidelines for Disposal of RCRA
Hazardous Waste.
49 CFR Parts 170-179 - U.S. Department of Transportation
regulations governing transportation of contaminated wastes.
Cost-Effectiveness
The selected remedy provides a level of protection of human health
comparable to that provided by the other remedies, but at a significantly
reduced cost.
The estimated total cost is $100,000 which includes a net present worth
cost accounting for 20 years of Operation and Maintenance at the site. The
O&M activity is expected to include cutting the grass and maintaining
vegetation at the site.
Utilization of Permanent Solutions and Alternative Treatment (or resource
recovery) Technologies to the Maximum Extent Practicable (HEP) .
The Air Force has determined that the selected remedy represents the
maximum extent to which permanent treatment technologies can be utilized in a
cost effective manner for Site FT-3. Of those alternatives that are
protective of human health and the environment and comply with ARARs, the Air
Force has determined that the selected remedy provides the best balance in
terms of short-term effectiveness; implementability; cost; reduction in
toxicity, mobility, and volume; and long-term effectiveness.
Due to the relatively low risk associated with the Site, the Air Force
has determined that the use of a more costly treatment technology at Site FT-3
is not justifiable. Because all the remedial alternatives with the exception
of Alternative 1, offer a comparable level of protection of human health and
the environment, the Air Force has selected Alternative 5, which can be
implemented quickly; will have little or no adverse effects on the surrounding
community; and will cost considerably less than the other alternatives.
Preference for Treatment as a Principal Element.
The statutory preference for remedial alternatives that employ treatment:
as the principle element will be met with the implementation of the selected
remedy. The principle threat will be eliminated by treatment of the site
structures.
Documentation of Significant Changes
The preferred alternative originally selected in the Proposed RAP is
also the preferred alternative identified in the ROD.
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XI RESPONSIVENESS SUMMARY
FIRE TRAINING AREA 3
DOVER AIR FORCE BASE
KENT COUNTY, DELAWARE
SEPTEMBER 1990
This community relations responsiveness summary is divided into the following
four sections:
Overview: A description of the selected remedy and community reaction to the
selected remedy.
Background of Community Involvement and Concerns: A brief history of
community interest in Fire Training Area-3 and Dover AFB.
Summary of Public Comments and Air Force Responses: Replies to public
comments.
Remedial Design/Remedial Action Concerns: Discussion of public concerns which
have a bearing on the remedial action.
Overview
The RI and FFS reports and the Proposed RAP for Site FT-3 were released
to the public for review and comment on August 14, 1990. This date marked the
opening of the public comment period on the alternatives detailed in the
Proposed RAP. A public notice was published on August 14, 1990, which
identified Alternative 5 as the preferred remedial alternative for Site FT-3.
Alternative 5 includes decontamination, removal, and offbase disposal of the
Site FT-3 piping/structures; soil sampling around the UST; providing a soil
cover over the site; and revegetation of the site. A detailed description of
the decontamination, removal, and disposal process for the site
piping/structures is provided in Section 4 of the FFS.
The limited comments received from the public suggest that area
residents do not object to the preferred alternative. However, there is
concern that the preferred remedial action does not address the possibility of
contaminated groundwater or surface water migrating offsite. The Air Force
conducts quarterly monitoring of surface water and is continuing an
investigation of basewide groundwater to address this concern.
Background of Community Involvement and Concerns
Site FT-3 was a fire training site covering approximately 1.3 acres and
was used from 1962 until May 1989. Off-specification jet fuel (JP-4) and used
motor oil was spread in a water-saturated pit, ignited, and then extinguished.
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In 1982, the United States Department of Defense (DOD) implemented the
Installation -Restoration Program (IRP) to identify and evaluate environmental
contamination and associated public health hazards at DOD facilities resulting
from past operations and waste handling/disposal. An Installation Assessment
(Phase I-Records Search) was completed from Dover AFB in 1983. This study
indicated a potential for contamination from past and/or current facility
operations at a number of sites, including Site FT-3. Two successive RI
studies were completed in 1986 and 1989. These RIs confirmed the presence of
contamination in the soil and groundwater. An FFS was completed in August
1990. This FFS included development of a BRA, Remedial Action Alternatives,
and a discussion of compliance with applicable or relevant and appropriate
requirements (ARARs). A Proposed RAP was also developed in August 1990, which
recommended selection of Alternative 5. In addition, a public meeting was
conducted on August 30, 1990, and a public comment period was held from
August 14 to September 27, 1990.
The Public Affairs Office at Dover AFB issues press releases detailing
IRP progress. Coverage in the two daily newspapers serving the Dover area has
usually been front page, but the issues tend to dissipate within a few days
because of a relatively low level of community concern. The start of remedial
activities at Dover AFB could increase community concern.
Summary of Public Comments and Air Force Responses
The majority of the written and oral comments received during the public
comment period revolved around surface water and groundwater conditions at
Dover AFB.
1. One commentor asked if surface water had been monitored at Dover AFB ac
all in the past.
Air Force Response: Surface water is analyzed on a quarterly basis at
the two major storm drainage outfalls. One of the outfalls is on the
southwest side of the base, adjacent to the golf course and near the St.
Jones River. The other is located very near Site FT-3 in the Pipe Elm
Brach, which flows into the Little Creek. In addition, site specific
surface water samples were taken during the two SAIC studies. The
analytical evidence suggests the surface water does not pose a threat to
human health or the environment.
2. A commentor asked if groundwater studies had been conducted.
Air Force Response: Groundwater studies have been conducted, however,
the geology in conjunction with past wastes sites is very complex and
has not yielded a complete picture of groundwater migration. For this
reason, additional study is required. This ROD only addresses soil. Ic
does not address groundwater or surface water.
3. A commentor asked about the stated problem for Site FT-3 being fire and
explosion and asked why EPA was involved.
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EPA/Air Force Response: A three-part Federal Facility Agreement was
signed-which requires remediation of many sites on Dover AFB. FT-3 was
one of these sites. At the time FT-3 was included in the Agreement, we
thought there was a soil problem there. After reviewing the data, we
found that the analysis of the soil indicates contaminant levels are
well below the allowable levels calculated to be protective of human
health and the environment.
Remedial Design/Remedial Action Concerns
The only comment regarding implementation of the remedial action was
about how contamination resulting from construction could be contained on
Dover AFB.
Air Force Response: Soil will have water applied to it before
excavation to minimize dust. In addition, a silt fence will be
installed around the construction area to minimize erosion. An
absorbent boom will also be maintained in the drainage channel in the
event a contaminant was to bypass the other containment measures.
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XII REFERENCES
Engineering Science (ES), 1983. Installation Restoration Program. Phase I--
Records Search. Dover AFB. Delaware, prepared for U.S. Air Force.
Johnson, R.H., 1977. Digital Model of the Unconfined Aquifer in Central and
Southeastern Delaware. Delaware Geological Survey Bull. 15.
Leahy, P. 1982. Groundwater Resources of the Piney Pint and Chesvold Aquifers
in Central Delaware as Determined by a Flow Model. Delaware Geological
Survey Bull, 16.
Science Applications International Corporation (SAIC), 1989. Installation
Restoration Program. Stage 2 Draft Final Report. Dover Air Force Base.
Delaware. Prepared for Headquarters, Military Airlift Command, Scott
Air Force Base, Illinois.
Science Applications International Corporation (SAIC), 1986. Installation
Restoration Program. Stage 1. Dover Air Force Base. Delaware. Prepared
for Headquarters, Military Airlift Command, Scott Air Force Base,
Illinois.
Sundstrom, R.W., and Pickett, I.E., 1968. The Availability of Groundwater In
Kent County. Delaware. With Special Reference to the Dover Area.
University of Delaware Water Resources Center, Newark.
United States Environmental Protection Agency (USEPA), 1989. Risk Assessment
Guidance for Superfund Human Health Evaluation Manual. Part A. External
Review Draft, Office of Solid Waste and Emergency Response (OS-230),
9287.701A.
United States Environmental Protection Agency (USEPA), 1979. Water-Related
Environmental Fate of 129 Priority Pollutants. Prepared by M.A.
Callahan, M.W. Gabel, I.P. Map, and C.F. Fowler for the Office of Water
Planning and Standards, U.S. Environmental Protection Agency,
Washington, D.C.
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