United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
E PA/ROD/R03-88/052
June 1988
Wildcat Landfill, DE
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RECORD OF DECISION
ROD DECISION SUHKARY
SUMMARY OF REMEDIAL ALTERNATIVE SELECTION
WILDCAT LANDFILL SITE
KENT COUNTY. DELAWARE
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION III
PHILADELPHIA, PA
and
DELAWARE DEPARTMENT OF NATURAL RESOURCES AND ENVIRONMENTAL CONTROL
DOVER. DE
0000~1
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I.
II.
III.
IV.
V.
VI.
'VII.
VIII.
IX.
X.
XI.
TABLE OF CONTENTS
Page
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Site Location and Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Site History[[[ 4
Current Site Status................................................ 5
A. Geology[[[ .'..... 5
B. Hydrology[[[ 8
C. Extent of Contamination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., 13
1. Inorganic[[[ 13
2. Organic[[[ 14
Biological Assessment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., 15
Risk Assessment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., 15
A. Groundwater--Current Offsite Residents.......................... 19
B. Groundwater--Future Offsite Residents........................... 19
C. Groundwater--Future Onsite residents............................ 19
D. Soil and Leachate--Occasional Site Users........................ 19
E. Surface Water--Occasional Site Users............................ 20
F. Fish Intake--Occasional Site Users.............................. 20
Remedial Action Objectives......................................... 20
Remedial Alternatives Evaluation................................... 21
A. Description of Alternatives..................................... 21
B. Evaluation of Alternatives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . 23
Community Relations. . . . . . ; . . . . . . . . . . . . . . . . . . . . . . . . . . . .'. . . . . . . . . . . .. 33
Documentation of Significant Changes............................... 34
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Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
FIGURES
1. Site Location Map........................................:.....
2. Site Map. : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3. Borehole and Monitor Well Locations............................
4. Trench Loca t ions'. . '. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .
5. Groundwater-level Elevations in Columbia Formation..... "'" ...
6. Groundwater-level Elevations in Waste and Meander Channel.. ....
7. Schematic Hydrodynamic Cross Section........ .'. ..... .... .... ....
8. Organic Compounds in Groundwater Samples.......................
9. Domestic Well Sample Locations.................................
10. Offsite Groundwater Restric~ed Areas in Columbia Formation. . . .
TABLES
Table 1. Summary of Risk Assessment. . . . . . . . . . . . . " . . . . . . . . . . . . . . . . . . . . . . . .
Table 2. Recommended Alternatives: Summary of Detailed Analysis.........
~nooot)~
Page
2
3
6
7
10
11
12
16
28
29
18
, 24
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SUMMARY OF REMEDIAL ALTERNATIVE SELECTION.
. Wildcat Landfill Site
Kent County. Delaware
I. Introduction
This Record of Decision addresses the first of two operable units for the
Wildcat Landfill site and is made up of the landfill proper and the adjacent
areas. The second operable unit consists only of the pond that is located
along the northwestern border. of the landfill. This ROD involves selection of
a remedial alternative which addresses the contamination source by preventing
existing and future direct contact where a direct contact threat is posed by
the site, by reducing the potential for future direct contact risks off the
site, and by prohibiting well installations .in areas of known or suspected
contamination. The remedial investigation/feasibility study (RI/FS) will be
continued in order to address the impacts the landfill on the adjacent pond and
the wildlife found there.
A remedial investigation was conducted to determine the extent .of contamination
resulting from the site and to determine the potential risks posed to human
health and the environment on and adjacent to the site. The remedial
investigation report addresses the onsite risks posed by the site, the offsite
ground water contamination risks, and the stream and wetland systems on and
adjacent to the site. The accompanying feasibility study report screened
various response actions which could be used to mitigate effects of the site
and to compare a number of alternatives which address the problems posed by the
site. The alternatives have been evaluated using the followi~g criteria from
the Superfund Amendments and Reauthorization Act (SARA) Section 121:
protection of human health and the environment, compliance with other.
environmental requirements, implementability, short-term effectiveness, long-
term effectiveness and permanence.. reduction in toxicity, mobility and volume,
cost effectiveness, and community acceptance. The public was given an
opportunity to comment upon the Proposed Remedial Action Plan and the'
Administrative Record which includes the RI/FS. The comments and concerns made
by the public are considered in the alternative evaluation and are specifically
addressed in the attached responsiveness summary (Appendix E).
Finally, this Record of Decision documents the selection of the final remedy
by DNREC and EPA and is based upon the contents of the Administrative Record.
II. Site Location and DescriDtion
The ~ildcat Landfill site is approximately 44 acres in area located in Kent
County, Delaware, 2 1/2 miles southeast of Dover (See Figure 1). The site lies
along the west bank of the St~ Jones River and is bordered to the north and
east by the river and associated marshlands, and to the south and west by
residential and commercial establishments (See Figure 2). A pond which was
created by construction of the landfill is located directly adjacent to the
site along the northwestern edge. Portions of the site lie within the lOO-year
floodplain of the St. Jones River.
". ~
1
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Figure 1
GENERAL SITE
LOCATION MAP
Wildcat Landfill, Dover, Delaware
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BARDEN PLUMBING &
o. B. WILLIAMS
ELECTRICAL COMPANY
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.
FEATURES ADJOINING
LANDFILL SITE
WildCat LJ 0 0 0 () 6
Do~er Detaware i7;;:;:.,;':~ .
. ~.C;":.""?'~''':',,-.y==.;
IE. rn
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APPROXIMATE LANDFILL BOUNDARY
SCAI..E 1"' . "a:J1
3
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Much of the site is .situated upon Im..-lying wetland sediments. However, the
area to .the southwest was backfilled with wastes following excavation of soil
and sand material; consequently, in that area of the landfill, wastes are in
direct contact with the surficial sand aquifer. The entire site was covered
with sands excavated from this area and from a second excavation area nearby
although this second area was not used for landfilling. Much of the site is
presently well vegetated with a number of plant communities established.
Leachate seeps are present in a few areas of the site, particularly in the area
of the adjacent pond. Exposed trash is evident in isolated areas across the
entire area of the site and includes empty or partially empty drums, tires,
.solid latex, and assorted municipal trash.
The St. Jones River and its associated marshlands provide natural barriers to
human access along the north, east, and part of the southeast boundaries of the
site. Access along the northwest area of the site is not restricted but is
made somewhat difficult by the adjacent pond and associated marshy areas. The
site is easily accessed along the southwest perimeter both by vehicle and on
foot in the area of the Hunn house and behind the businesses located adjacent
to the ~ite. As shown in Figure 2, the only residential property located
direc tly adj acent to the site is 'the Hunn residence who are the property
owners.
The Wildcat Landfill site is situated in the Atlantic Coastal Plain
Physiographic Province. Most of the site is below about 20 feet mean sea
level (MSL) , within the natural m~ander channel of the St. Jones River. This
low-lying part of the landfill was created by dumping and spreading waste
directly into the wetlands of the river; The southwestern corner of the
landfill lies at elevations of 20 .to 30 feet MSL and is apparently beyond the
meander channel. Wastes in this upland portion were disposed within a man-made
. excavation.
The predominant surface hydrologic feature of the area is the St. Jones River
and its tributary, Tidbury Creek. Both are tidal with a normal tide range of'
2 feet in the vicinity of the site. Much of the site lies within the lOO-year
floodplain. Two other surface hydrologic features of the area are the pond
and a small drainageway (which conveys water from Route 10 to the St. Jones
River along the northwestern border of the site). The drainageway appears to
have been man-made and is separated from the landfill by a low but continuous
ridge extending along the pond and landfill.
The geohydrologic units of major importance in the area are the surficial
Columbia Formation and two major sand beds within the Calvert Formation.of the
Chesapeake Group, namely, the Frederica Aquifer and the underlying Cheswold
Aquifer. All residents.of the study area draw their water from wells within
one of these three units. .
III. Site History
The site was operated as a permitted sanltary landfill between 1962 and 1973,
accepting both municipal and industrial wastes. Liquid and solid wastes were
reportedly mixed together, compacted, and covered; drums of waste were
.reportedly emptied onsite and the empty drums recycled. Industrial wastes
suspected to have .been disposed include latex waste and paint sludges.
4
OQ0007
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1__-
However, there are no known existing records of the actual quantity of wastes
which were disposed in the landfill.
The facility was permitted as a solid waste landfill by the Delaware State
Board of Health in 1962. The site was later permitted by the Delaware Water
and Air Resources Commission (WARC) and then by DNREC. However, throughout its
eleven years of operation, the facility appears to haye routinely violated
operating and other permits issued by the regulating agencies. In August of
1973 the facility was ordered by DNREC to cease operations for failing to
comply with permit conditions. The site operators were ordered to cover with
soil and revegetate the site. The entire regulatory history is discussed in
the EPA Remedial Action Master Plan (RAMP) which is available in the
Administrative Record.
The site was investigated by the EPA in June 1982 for possible inclusion on
the National Priority List (NPL) of hazardous waste sites. The site was
subsequently listed in December 1983 and the RAMP published that same month.
The Delaware DNREC requested and the EPA agreed to allow the state to
perform a remedial investigation and feasibility study. DNREC began the
investigation in September 1985 and the feasibility study in November 1987.
The RIjFS report was drafted and released for public comment in May 1988.
IV. Current Site Status
Through a Cooperative Agreement with the EPA, the Delaware DNREC completed the
RIjFS for the Wildcat Landfill site through its contractor, CH2M Hill
Southeast, Inc. The RI report describes the geology and hydrogeology, onsite
and offsite chemical characteristics, onsite and offsite biological assessment,
wetlands assessment, and suspected risks within the study area. The geology,
hydrology, and types and concentrations of contaminants found onsite and
offsite will be described in this section. The biological assessment and the
risk assessment will be described in the next two sections, respectively. A
summary of all chemical data generated during the remedial investigatio:1 is
included in Remedial Investigation Report.
A. Geology
The geology of the study area was interpreted from monitor well borings drilled
onsite and offsite. The monitor well locations are found on Figure 3.
Trenches were dug onsite both for sample collection and for ~nterpreting the
geology and hydrology of the study area (See Figure 4). Other information
sources were cuttings from nearby residential wells, logs of nearby wells from
the Delaware Geological Survey, logs of borings from the Delaware Department'
of Transportation at the Route 10 bridge, historical areal photographs, United
States Geological Survey (USGS) topographical maps, Delaware Geological Survey
geologic and hydrogeologic reports, and reconnaissance of the area.
I .
There are three kinds of. surficial deposits in the study area. The two
naturally occurring deposits are' sands interpreted to be of the Columbia
Formation and the meander channel organic silts and sands of the St. Jones
River. The' third surficial material are the landfill wastes associated with
the landfill and a small area on the eastern side of the river which appears
to be construction material.
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= 47-000
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3 3 WASTE 30REHOLE
915 MONITORING WELL
A PQNO WATEH LEVEL
«-••' APPROXIMATE LANDFILL SOUNDAflY
Figure 3
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BOREHOLE AND
MONITORING WELL
SAMPLING LOCATIONS
WBdcat Landfll.
Dover, Delaware
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\14
TRENCH LOCATION
APPROXIMATE LAND FILL BOUNDARY
NOTE: THENCH6S t-14 EXCAVATED 12/»-l3/85j
TRENCHeS 13-25 bXuAVATED 11/2-6/37
Flzure 4
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LOCATIONS OF TRENCHES
EXCAVATED FOR THE
REMEDIAL INVESTIGATION
WILDCAT LANDFILL.
DOVEH, DELAWARE
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The general stratigraphy of the study area is detailed in the RI report and is
described here in ascending order:
(1) The Cheswold aquifer is a sandy zone within the Chesapeake Group
consisting of medium to coarse sand and shells. The top of the Cheswold
aquifer in the study area is at approximatley 200 feet below ground surface.
These sands underlie the entire study and are separated from the overlying
Frederica sands by confining silts and clays. The Cheswold sands were not
evaluated in the remedial investigation but will be used in the ~emedial
action;
(2) The Frederica sands are interpreted as members of the upper Chesapeake
Group. These sands underlie the entire study area and generally grade from
fine silty sand in the southern part of the study area to coarse sand with
gravel in the central and eastern portions of the study area;
(3) The clay semi-confining layer found above the Frederica
throughout the study area although its extent and integrity
meander channel was not defined. These clays are generally
some places contain a trace of silt and fine sand;
sands extends
beneath the
plastic and in
(4) The .Columbia Formation directly overlies the clay semi-confining layer in
all locations outside of the meander channel of the St. Jones River. This
formation is composed primarily of fine to coarse sands with a trace of medium
gravel. Sands of the Columbia underlie portions of the landfill outside of
the meander channel. Within the meander channel, however, distribution of
, Columbia sands is uncertain although sand deposits were found there. These
could either be extensions of the Columbia or channel deposits;
(5) The meander channel deposits of the St. Jones River are exposed along the
north, east, and southeast of the boundaries of the landfill. Similiar
deposits are found exposed in and around the pond on the west side of the
landfill. The uppermost unit of these deposits is composed of organic silts
and some clay, root fibers, and wood fragments. These deposits were also
found beneath the landfill in the meander channel. Beneath these organic
deposits are sands which may either be undisturbed Columbia sands or reworked
channel deposits;
(6) The landfill materials are in direct contact with sands of the Columbia
Formation in the southeast corner of the landfill. This is referred to as
Area 1 in the risk assessment. Wastes within the meander channel are in
direct contact with meander channel organic silts. The typical wastes
encountered during the remedial investigation included municipal refuse (glass
bottles, waste paper, trash, and decomposed garbage), latex in strips and
sheets, scattered crushed, empty, and some intact drums, and manufactured
plastic items. Wastes ranged to 20 feet deep across the site with the thickest
and highest area outside the meander channel. Within the meander channel the
wastes have compressed and otherwise displaced the meander channel silts.
. B. Hydrology
The hydrology of the study area is strongly influenced by the St. Jones River
and the tidal action of the river. The hydrogeology was determined with the 27
monitor wells installed at 15 locations on and near the landfill. Wells were
8
00001.1
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'-
I
screened within the Columbia Formation, Frederica sands, landfill materials,
meander channel silts, and meander channel sands.
The hydraulic properties of natural materials in the study area were
determined through variable-head (slug) tests at individual wells, and by an
aquifer test conducted for 48 hours in the Frederica sands at MW-16A. Single
water-level measurements were taken in all the monitor wells and in the pond
adjacent to the site in April and June 1986. Continuou~ water-level
measurements were taken between September 1986 and January 1987 at various
monitor wells and from the St. Jones River. Figure 5 and Figure 6 represent
the offsite and onsite surface water table configuration, respecti3ely. The
hydraulic conductivity of the Columbia wells ranged from 2.5 x 10. to
3.3 x 10-2cm/sec which is typical of sands and silty sands. The hydraulic
conductiv!ty of the meander channel organic silts were 9.9 x 10.4 and
1.9 x 10. . Many of the tests conducted in the meander channel silts and
sands were abnormal which may indicate a limited areal extent of t20se sands.
The hydraulic propertie~ of the Frede:}ca sands were 412 to 330 ft /day for
transmissivity, 3 x 10. an~ 1.3 x 10 cm/~ec for hydraulic
conductivity, and 9.6 x 10. and 2.7 x 10- for storativity. These
values are typical of semiconfined sands and silty sands.
Patterns of groundwater flow are generally toward the St. Jones River although
very localized flow directions are more varied because of local topographic
features and tidal fluctuations of the river. Measurements from wells which
are tidally influenced are difficult to interpret because the tidal influence
varies both spatially and temporally depending on the location of the monitor
well with respect to the river.
The hydrodynamic setting is depicted in Figure 7 and as follows:
(1) The Columbia Formation is unconfined and the water table mimics the
topography. Flow is from topographic highs to topographic ~ows. Groundwater
from the Columbia discharges into the various surface features found within
the meander channel. Discharge from the area of the Wildcat Archery Range is
either into the St. Jones River directly or into the drainageway that exists
northwest of both the pond and the site. Discharge from the Columbia in the
area directly west of the site is toward t~e pond, the landfill, and Tidbury
Creek. Discharge may also occur into the meander channel sands if they are
directly connected to the Columbia sands. The southwestern corner of the
landfill rests directly upon Columbia sands and horizontal flow continues from
this area of the landfill toward both the St. Jones River and Tidbury Creek;
(2) The semiconfining clays found atop the Frederica sands allow vertical
flow. Within the meander channel this flow is vertically upward while outside
of the meander channel the flow is downward;
(3) The Frederica sands are semiconfined with the overlying confining clays
relatively thin beneath parts of the meander channel. Horizontal flow is .
generally from west to east.. Vertical flow is controlled by recharge
occurring from the Columbia Formation through the confining clays and into the
Frederica sands outside of the meander channel, and upward discharge from the
Frederica sands into the meander channel and the St. Jones River occurring
0000J2
9
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= 476000
=477000,
=47
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INTERPRETED WATER-tEVEL CONTOUR (FT MSU
COLUM8IA/M6A^40EH CHANNEL CONTACT LINE
QflOUNDWATEH DIVIDE
MONITOR WELL AND WATER LEVEL READING (FT MSU
APPROXIMATE LANDFILL BOUNDARY
300
Fizure 5
INTERPRETIVE MAP OF
WATER-LEVEL ELEVATIONS
IN COLUMBIA FORMATION,
AP*,L
LandfW.
Dover, Delaware
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INTERPRETED WATER-LEVEL CONTOUR (FT MSU
COLUMBIA/MEANDER CHANNEL CONTACT LINE
GROUND WATER DIVIDE
MONITOR WELL AND WATER LEVEL READING (FT MSU
APPROXIMATE LANDFILL BOUNDARY
200 400 500
E
SCALi <" ' 400*
300
.Figure fi
INTERPRETIVE MAP OF
WATER-LEVEL ELEVATIONS IN
WASTE AND IN MEANDER
CHANNEL ORGANIC SOILS.
APRIL 1O-11, TG86
Wildcat Landfil. OOOOJ
Dover, Deiavwe
11
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Approximate
Elevation In
FeetMSL
I lorizonlal Direction ol
Groundwaler Flow
Vertical Direction of Groundwaler Flow
-40
|iy#;>;v^:^^
30
20
10
3f
4f
O
O
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Waste
Columbia Forrnallon
Clay Confining Layer
Meander Channel Silts
Meander Channel Sands
Frederlca Aquifer
Figure 7
SCHEMATIC HYDROGEOLOGIC CROSS SECTION
Wildcat Landfill
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within the meander channel.
tidal action from the river;
All wells within the Frederica were influenced by
(4) Horizontal flow direction within the meander channel sands is poorly
defined although flow directions are undoubtedly toward the St. Jones River.
All wells were influenced by the tidal action of the river. These sands are
being recharged by overlying deposits near the center of the landfill and away
from the center of the meander channel, and discharging upward into overlying
deposits within the meander channel;
(5) Horizontal flow directions within the landfill wastes is poorly defined
within the meander channel. However, flow is expected to follow topography
and be consistent with flow from Columbia sands outside of the landfill.
Generally, horizontal flow will be radial from topographic highs within the
landfill with discharge occurring into the adjacent pond and meander channel
deposits. ~ithin Area 1, horizontal flow will continue offsite into Columbia
sands with subsequent discharge into the St. Jones River and Tidbury Creek.
(6) The mean tidal variation in the St. Jones River is approximately 2 feet.
The mean elevation was 1 foot mean sea level (MSL) with a total range of -1 to
3 feet MSL. ~ater levels in many wells showed similiar fluctuations in level.
Generally, the water levels were higher in April and lower in June and October.
The average linear velocity of flow in the Columbia Formation was calculated at
49 to 91 feet per year. The average linear velocity of groundwater flow in the
Frederica sands is between 5.6 and 26 feet per year.
C. Extent of Contamination
Two rounds of sampling and chemical analyses were performed in the remedial
investigation and the table summaries are found in the RI Report.
Samples of soil, water, and landfill contents were collected throughout the
study area. This includes samples collected by the EPA Emergency Response Team
from wetlands and stream channel locations.
1. Inorganic Characterization and Contamination
The major ion and bulk chemistry interpretations were used to classify the
various waters in the study area and to interpret the likelihood of inorganic.
metal concentrations and distribution. Based upon the total dissolved solids
concentration, the waters of the study area are of three types:
-less than 200 parts per million (ppm)--Co1umbia Formation, all domestic
wells, and Frederica sands;
-500 to 2000 ppm--meander channel silts, landfill leachate; and
-greater than 2000 ppm--surface water from St. Jones River and its tributaries.
The ion chemistry (namely the cations:ca1cium, magnesium, potassium, sodium;
and anions:carbonate, chloride, sulfate) suggest that the pond and ~-l2 waters
have been affected by the landfill, that the meander channel silt water has
been affected by the St. Jones River, and that the meander channel sand waters
are affected by the Frederica aquifer waters. There appears to be no affect of
either the St. Jones River nor the landfill on the meander channel sands. This
data supports the hydrogeologic understanding that there exists an upward
gradient from the Frederica aquifer into the meander channel, or that the
13
()OOOJ6
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meander channel organic silts have been an effective buffer for contaminants
leaving the landfill and entering those organic deposits, or both. Both MY-lS
and MY-16B are similiar to the Frederica aquifer water. . MY6B may be affected
by the landfill but the results are anomalous.
The trace element chemistry (aluminum, antimony, arsenic, barium, cadmium,
chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, selenium,
silver, tin, vanadium, zinc) of waste trenches were similiar to. the bottom
sediments of the St. Jones River and generally within the range of
naturally-occurring concentrations. The concentrations from soils taken
from borings, primarily of Columbia Formation sands outside the landfill, were
slightly below the river and landfill sediments.
The extraction procedure analyses performed on landfill wastes were almost all
below the detection limits although barium at 2400 ppb occurred in Trench 6;
lead at 10.5 ppb in trench 1, 20.5 ppb in Trench 3, 19.5 ppb in Trench 7, and
1940 ppb in Trench 17; mercury at 0.3 ppb in Trench 16, 1.4 ppb in Trench 18,
and 0.2. ppb in Trench 24; and selenium at 10 ppb in Trench 10.
The mean concentration of trace elements in water samples were primarily
reflective of the St. Jones River, as most were taken from the river. Station
6 in wetlands adjacent to the southeast of the landfill had relatively high
concentrations of aluminum, arsenic, barium, chromium, iron, lead, manganese,
vanadium, and zinc. Station 16 in the pond and the leachate seep near the
south end of the pond also had higher concentrations of these elements as
compared to the St. Jones River. Groundwater and leachate samples taken within
the landfill contained elevated levels all trace elements except arsenic and
manganese when compared with groundwater samples taken outside. the landfill.
In addition, cadmium, cobalt, nickel, and vanadium were consistently present in
the landfill waters but rare or absent in other groundwater samples including
both domestic and commercial, and monitor wells.
i. Organic Characterization and Contamination
With few exceptions, samples taken from the study area contained concentrations
of organic constituents in the low ppb range. Further, there was no
discernible pattern to their distribution.
The highest concentrations up to a total of 70 ppm were found in drums
excavated during the second trenching operation. Most of this is accounted for
with styrene at 69 ppm. Other common constituents were ethylbenzene (from a
few to 900 ppb), methylene chloride (similiar range), and phthalates (generally
10 to 40 ppb).
Trench samples typically contained totals of a few hundred ppb of organic
constituents. Of the 43 organic compounds detected in Round 2 sampling,
only acetone (6 to 43 ppb), benzene (4 to 15 ppb), chlorobenzene (16 to 110
ppb), ethylbenzene (1 to 300 ppb) , .methylene chloride (1 to 5 ppb),
~ylenes (7 to 150 ppb) , and naphthalene (5 to 32 ppb) were common. The
high~st single concentration for phthalate was 8500 ppb in Trench 24.
The water and sediment samples collected from the wetlands and surface water
by the EPA Emergency Response Team were generally free of organic constituents.
Phthalates were found .from some sediments in the study area in the low ppb
14
0000J7
. -. - --~- .
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range.
Both groundwater and surface water samples generally contained low levels of
organic contamination. But as seen in Figure 8, benzene compounds, toluene,
and xylenes (BTX) were common contaminants in the low.ppb range. Certain of
these contaminants also occurred in wells upgradient of the landfill, such as
MW 13A, lBand C, and 14A. In fact, the highest concentration of BTX compounds
occurred in MW-16B which is screened across the rive~ in the Columbia
Formation.
V. Biological Assessment
The biological assessment documented a productive and diverse ecosystem within
the Wildcat Landfill site boundary. Five species of plants were identified
which are listed on the Delaware Natural Heritage Inventory draft list of rare
or seldom seen plants. Histopathology on white-footed mice and
bioaccumulation studies of small mammals did not indicate adve~se effects to
terrestrial wildlife.
Comprehensive sediment toxicity testing did not indicate any adverse effects
on the St. Jones River and the marshlands adjacent to the site. However, of
the fish that were collected from the river, two fish contained PCB levels ~~
excess of the Food and Drug Administration action level of 2 ppm. The
available monitor well water data, surface water data, and sediment data do
not indicate that the landfill is a source of the PCBs.
Several impacts from the landfill were found in the pond adjacent to the site.
These impacts included levels of acute toxicity in the southwest portion of the
pond, leachate entering the pond from the site having concentrations of certain
metals above water quality criteria, and bioaccumulation of several metals
within turtles and mummichog fishes collected from the pond.
i
i
[.
In order to fully asses~ the impact of bioaccumulation in the fish upon
migratory birds which may be feeding on these fish, the pond has been made a
separate operable unit and will be addressed in a continuation of the
remedial investigation and feasibility study. Remediation of the pond is not
addressed in this record of decision.
VI. Risk Assessment
The purpose of the risk assessment is to provide a mechanism for documenting
the hazards or potential hazards posed by the site for the support of remedial
actions under Section 106 of CERCLA. The general elements of the risk
assessment include a toxicitY assessment of chemicals identified at the
site, eXDosure assessment for identifying the major potential routes oJ
human exposure, and the risk characterization which combines the potential
exposure pathways and information on the toxicity assessment to estimate the
potential effects of the site on human health.
The current and future exposure pathways examined for this site in the risk
assessment are (1) exposure in groundwater for residents downgradient of
the site who. use groundwater as a source of drinking water, (2) exposure to
15
000018
-------
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--::d"iOLW-' - n____u
COmpounds Tested For.
1. Benzene
2. Chlorobenzene
3, Elhylbenzene
4, Total Xylenes
5. Toluene
6. Chloroethane
(
-------
contaminants in groundwater for future onsite residents who use groundwater as .
a source of drinking water, (3) exposure of' contaminants in the St. Jones River
from incidental ingestion of surface water by occasional site users,
(4) exposure through ingestion of fish from the St. Jones River by occasional
site users, (5) exposure to contaminants in soil and leachate through direct
contact by occasional site users, and (6) exposure to contaminants in the soil
and leachate through direct contact by future onsite residents.
The ingestion of fish in the St. Jones River is reported here but is not a
subject for this decision. The information has been given to the federal and
state agencies responsible for this public health concern. This pathway is
not considered here because of the following: (1) the landfill could not be
identified as a source of the PCBs although PCBs were found in certain waste
materials, (2) PCBs were not found offsite in either sediments or water
samples, and (3) the fish sampled in the St. Jones River travel well beyond the
length of river near the site, including possibly beyond the St. Jones River
watershed.
The risk characterization includes comparisons between estimated intakes and
reference doses (RfDs) for noncarcinogenic chemicals and estimates of excess
lifetime cancer risk for exposure to carcinogens. These comparisons and,risk
estimates must be interpreted carefully because, for each exposure setting,
assumptions as to chemical concentrations, exposure durations, and
characteristics of the potentially exposed population are made. Further,
quantitative assessment is possible only for those chemicals for which EPA has
developed numerical criteria. Chemicals which have no criteria are excluded
from the risk analysis. Table 1 summarizes the risk assessment with
summaries of existing or future exposed populations, routes of exposure, excess
lifetime cancer risks, comparisons to reference doses for noncarcinogens, and
chemicals of concern.
Over 80 chemicals were detected in samples analyzed for the RI and over 60
were considered in the risk assessment. These chemicals can be separated into
two categories according to their health effects, namely, carcinogens and other
chronic toxicants that are o~ncarcinogenic. The carcinogenic effects are
expressed as the excess lifetime cancer risk from exposure to individual
chemicals.
The excess lifetime cancer risk is the incremental increase in the probability
of devel~ging a cancer from exposure to contaminants at the site. For example,
a 1 x 10 excess lifetime cancer risk is an increase in the risk of cancer
incidence of one case per mil,ion people exposed. The acceptable risk range
adopted by ~PA is 10-4 to 10. .
The exposure to noncarcinogens is assessed by comparing estimated daily
intakes of contaminants to reference doses (RfDs). RfDs are established below
the threshold dose, that is, below the ,dose at which effects are expected to
occur. A simple additive risk model is used to assess the overall potential
for noncarcinogenic effects from a mixture of chemicals. The estimated daily
intake for each chemical is divided by the RfD for that chemical and the
resulting quotients for each chemical of the mixture is added resulting in the
hazard index (HI). If the HI exceeds 1.0, the potential hazard is
unacceptable and the chemicals are further evaluated.
17
000020
-------
....
CD
o
o
o
<::>
I\:)
~
Exposure
Population
Current Offsite
Residents
Future
Onsite
Residents
Future Offsite
Residents
Occasional
SHe Users
Occasional
SHe Users
OCCAsional
Site Users
wnR356/048
Route of
Ellposure
Grouodvater
iDIJesUon
Groundwater
lnjlosUon
Groundwater
injlestlon
Direct
contact
with 5011
Direct
contact with
leachate
Incidental
ingestion of
surface water
fish
ingelitlon
Excess LUeU.e
Csncer Risk
1 . 10-6
4 . 10-3
6 . 10-6
1 . 10-3
Not appliCAble
8 . 10-5
3 II 10-4
'fable 1
SUHHARY OF RISK ASSESSMENT
WILDCAT LANDFILL SITE
COllpar1son of
Reference Dose
No chellical
exceeds RfD,
HI . 1.0
HI . 104
HI . J.g
Chelllctlls of
Concern
None
Arlienic
PCBs
Chrysene
AnU80ny
Cadalua
Lead
Mercury (If alkyl)
Barlua
Chr08lwa
(If hexavalent)
Nickel
Manganese
HI . negligible Ar8enic
for children PCBs
and adults Chrysene
Not appl1cable
All daily
intakes are
negllgible
All dally
Inttlkes are
negligible
Mercury
Nooo
FCBa
COlIIIDents
Carcinogenic contaminants include
benzene and melhylene chloride. Bolh
were detecled 01 low concentrations,
hence leading 10 cancer risk estimates
In the acceptable risk range.
Arsenic was present at levelu below
t.he HCL. Chrysene was det.ect.ed in one
sample. Levels of noncarcinogens
exceediny RfDs were det.ected in
leachate only.
Carcinogenic conlaalnants Includq
benzene only. It wali detected in one
sample at 4 ppb and hence does not.
appear to be of concern. Two of
eleven samples would lead to exposures
of mang&1eSe exceeding the RfD.
Manganese causes taste probleas.
Chrysene was detecled In one sample.
Comparison of children's Intake' to
adjusted IO-day health advlsor~es.
Assumes exposure every day for a
lifetime. Carcinogenic contamlnanls
include in-senic and chlordlU"le.
Arsenic was det.ect.ed at. levels below
the HCI.. Chlon1ane WIIB detecled in
ona sliwple.
Three flah fillet samples exceed the
t'!)A action level. PCBs in these Ush
lire probdhi y not due to the sHe.
-------
A. Groundwater .- Current Offsite Residents
There is no evidence of contamination from the landfill in any of the
domestic wells sampled near the site. All wells within the immediate vicinity
of the landfill were sampled in the RI. The domestic wells DW-8 and DW-IO
exist in close proximity to the landfill and could potentially be affected by
landfill contaminants should they be overpumped or if groundwater flow
directions change near these wells. A risk assessment was performed on these
wells because of their close proximity to the site. No RfDs were exceeded and
the HI equals 1.0. The chemicals which contributed to the HI were barium,
cadmium, copper, and lead. These are natural trace ~lements. The potential
excess lifetime cancer risk was determined from maximum congentrations
reported in residential and commercial wells and is 1 x 10- because of the
presence of benzene and methylene chloride.
B. Groundwater--Future Offsite Residents
There are no existing users of water downgradient of the site where
offsite, migration of contaminants has been documented. The risk assessment is
based upon data fromMW-12A and B, and MW-6B. The estimated daily intake for
manganese was exceeded in MW-12, and the HI equals 2.9. However, manganese is
an essential nutrient and the RfD is based upon inhalation exposures rather
than ingestion. The potential exgess lifetime cancer risk through ingestion
of offsite groundwater is 6 x 10- due to the presence of benzene at 4 ug/l
in MW-12. No other carcinogens were detected in these wells.
C. Groundwater--Future Onsite Residents
The toxicity effects of onsite chemicals were used in the risk assessment to
evaluate their effects on future onsite residents. Data from MW-2 and aqueous
trench samples from Area. 1 were used in the evaluation. The RfDs were
substantially exceeded for antimony, cadmium, lead, mercury, barium, and
'chromi~, and the, HI was 104. The potential excess lifetime cancer risk was
4 x 10- . Arsenic, PCBs, and chrysene contributed most to this value.
C9ncentrations of arsenic, however, are below the maximum contaminant level
(MCL). Of the eleven samples used in this assessment, six contained arsenic,
four contained PCBs, and one contained chrysene. '
D. Soil and Leachate--Occasional Site Users
Both current and future occasional site users such as recreational users and
workers could be exposed to contaminants in soil and leachate. The values for
soils are extrapolated from chemical concentrations found in buried landfill
wastes and from leachate from the trenches. Values from a leachate seep
sampled near the pond were also used. Only ingestion is quantitatively
assessed and is compared to acute (lO-day) exposure to chemicals in the
leachate. The RfDs for adults and children were not exceeded and the HI
values were neg~~gible. The excess lifetime cancer risk from the ingestion of
soils is 1 x 10 with arsenic, PCBs, and chrysene contributing most to
that risk level. This level is very conservative with a number of important
assumptions. The chemical concentration levels in the surficial leachate
seeps is assumed to be the same as the levels found in leachate from the
trenches even though the concentrations for the leachate seep near the pond
were considerably lower than the trench samples, and with no PCBs found at the
surface seep.
19
000022
-------
E. Surface Water--Occasional Site Users
The RfDs for surface water were not exceeded
lifetime cancer risk of 8 x 10-5 is based on
and chlordane (detected in one sample).
and are negligible. The excess
arsenic (which was below the MCL)
F. Fish Intake--Occasional Site Users
Three fish collected from the St. Jones River were found to contain PCB levels
in excess of the Food and Drug Administratton (FDA) action level of 2.0 ppb.
The excess lifetime cancer risk is 3 x 10- . The remedial investigation
was unable to detect any PCBs beyond the landfill wastes in either sediments,
groundwater, or surface water samples. The fish that were analyzed are able to
move considerably within the St. Jones River and its tributaries and are
bottom feeders. For these reasons, the information on the PCB levels in the
fish samples has been given to the appropriate state and federal agencies and
is not addressed as a site-specific issue in this decision.
,
VII. Remedial Alternative Obiectives
The remedial action objectives were developed to respond to the site hazards
(summarized previously in this document) which are discussed in the Remedial
Investigation Report. Remedial action objectives address the media of concern,
which, for the Wildcat Landfill site are the offsite biota and the landfill
contents.
The remedial investigation found that the major areas of contamination are the
leachate within the landfill contents, leachate seeps near the pond, and
groundwater contamination of the shallow surface aquifer in'a limited area.
The risk assessment performed for the Wildcat Landfill indicates that
contaminants leaving the landfill do not currently pose a threat to human
health. However, people coming onto the landfill may be exposed to
contaminants at levels of concern in leachate seeps or from exposed landfill
contents. The potential risks associated with future releases of contaminants
from the landfill into the groundwater and, subsequently, into surface water
are also considered.
As stated previously in the Biological Assessment (Section V of this document),
biota on the landfill have not been adversely affected. However, onsite biota
could become contaminated in the future. Therefore, the objective is to
minimize the ingestion of contaminated biota. by humans by limiting the
exposure of biota to landfill contents. The impact of the landfill
contaminants on small fish and turtles in the adjacent pond is not a human
health concern since neither the turtles nor the small fish are consumed by
humans. . However, the fish may be a concern for migratory birds which use the
pond for feeding. This will be addressed as a separate operable unit with
an extended RI/FS report.
There are a number of concerns regarding the landfill contents: (1) the
St. Jones River could cause some erosion of the landfill contents through
either flooding of the river or through migration of the river channel;
20
000023
-------
(2) there are leachate seeps at isolated areas along the periphery of the
landfill, particularly notable in the area of the pond; and (3) protection of
the pond and wetlands adjacent to the site from runoff during any remedial
action activities.
Future direct contact with wastes is also a concern should residential or
commercial development occur upon the landfill. Therefore, the future risks
associated with onsite water wells was evaluated.
There is a future risk associated with future releases to the groundwater of
contaminants originating from the landfill. These groundwaters, however,
occur only as the water table aquifer, are of very limited area, contain no
existing users, contain little available groundwater, have naturally high iron
content, and discharge to the St. Jones River and Tidbury Creek, a few hundred
yards away from the landfill.
In conclusion, the remedial action objectives for the Wildcat Landfill
,
Feasibility Study are:
1. Minimize the ingestion of potentially contaminated biota taken from the
site. .
2. Prevent direct public contact with landfill wastes.
3. Limit the erosion of the landfill contents by the St. Jones River.
4. Minimize the environmental impacts of the landfill contents on biota.
S. Identify future impacts of releases of landfill contents to groundwater
and, subsequently, to surface water. Any releases must be addressed.
VIII. Remedial Alternatives Evaluation
A. Description of Alternatives
The alternative development process combines technologies and corresponding
process options for each medium which form the remedial actions for the site
as a whole. The resulting alternatives include a range of remedies and level
of effort which satisfy all or some of the remedial action objectives. In
accordance with recent EPA guidance, none of the alternatives in the detailed
analysis include treatment due to the size of the landfill (approximately 44
acres) and the absence of hot spots on the site. These site specific factors
make treatment impracticable. The purpose of the alternative analysis is to
provide the lead agency with a list of potential alternatives which provide
the best balance .among the evaluation criteria and meets the statutory finding
of protection of human health and the environment, attains ARARs, is cost
effective, and utilizes alternate treatment technologies to the maximum extent
practicable. The no action alternative is included as the baseline and should
only be used when the risk assessment indicates there are no present or future
threats to public health or the environment.
Alternative 1: No Action
The no action alternative requires no remedial action, therefore, the existing
site conditions would remain unchanged. The existing vegetative cover
provides for a large degree of erosion control, maintains the existing
hydrologic system, provides wildlife habitat, and limits direct contact by
21
000024
-------
humans and biota over much of the site. The five rare plants identified
onsite that are on the Delaware Natural Heritage Inventory would remain
undisturbed. There would be no institutional or monitoring requirements
onsite or offsite.
Alternative 2: Institutional Control and Monitoring
This alternative addresses the remedial action objectives by controlling the
receptors rather than the contaminants. The alternative consists of fencing
and signposting to limit access to the site, monitoring offsite groundwater to
reveal any migration of contaminants, and preventing development upon the
landfill and water well drilling onsite or in the surface aquifer in areas of
concern adjacent to the site. The site conditions would remain unchanged in
this alternative.
Alternative 3: Institutional and Surface Control
The purpose of the surface controls is to decrease erosion and ponding of
water on the surface of the site. This alternative includes institutional
control, monitoring and surface control,. and removal and treatment of drums and
their contents found on the surface of the landfill or uncovered during
grading. Surface control is achieved by grading and revegetating the site and
includes a temporary drainage ditch to protect the adjacent pond and wetlands
during remediation activities. Even though this would provide only minimal
cover, it would limit direct contact with the landfill contents. The
institutional and monitoring requirements would be the same as described in
Alternative 2.
Empty drums found during this operation would be crushed and disposed within
the landfill during the grading operation. Drums containing materials would
be sampled and secured on the site and, if the material is a RCRA hazardous
waste; transported and incinerated offstte. Drums containing non-RCRA waste
or product will need to be evaluated as to proper disposal. The state and EPA
will make this determination.
Alternative 4A: Containment ~ith Soil CaD
This alternative adds a soil cap thicker than the cover material from the
previous alternative. In addition, the institutional, monitoring, and
surface controls of the previous alternatives are included. The purpose of
the soil cap is to provide extra protection against the direct contact risk in
order to meet the direct contact objective.
Alternative 4B: Containment ~ith Soil/Clay CaD
Instead of the soil cap listed in Alternative 4A, this alternative includes
installation of a clay cap with soil cover plus all the technologies listed in
the previous alternatives. The clay would be effective in increasing runoff
and minimizing infiltration and would also be less susceptible to cracking from
settlement. The soil/clay cap should be able to survive deformation caused by
settling better than the soil cap alone.
22
utJ0025
~-- --~---- ------..-----
--------------
------" ------ -----
------- --.-------
-- --- --- ---
-------- ----- ------ -
-------
B. Evaluation of Alternatives
The five alternatives assembled above are evaluated to develop a more complete
analysis of their relative advantages and disadvantages. The evaluation is
based upon the following eight criteria developed in accordance with Section
121 of SARA (See Table 2):
- short-term effectiveness;
- long-term effectiveness and permanence;
- reduction of toxicity, mobility, and volume;
- implementability;
- compliance with ARARs;
- overall protection of human health and the environment;
- cost; and
- community acceptance.
State acceptance is also a criteria
alternatives but since the state is
EPA, that criteria is not pertinent
selection of the final remedy.
developed by EPA for the analysis of
a co-selector of the remedy along with
since the state acceptance is reflected in
The short-term effectiveness pertains to the potential impacts on the
community and to workers during the remedial action activities, the potential
environmental impacts of the remedial action, and the effectiveness and
reliability of mitigative and protective measures. The protection of the
community and workers during implementation of the remedial action refer~ to
. the onsite risks and offsite risks of implementing the alte~native. At this
site, three of the four alternatives have transportation of drums to a
RCRA incinerator as the only offsite component. . There would a150 be increases
in dust levels during construction activities. Therefore, there is little
risk to the community from implementation of any of the alternatives. There
may be risk to workers onsite;. therefore, worker protection would be needed to
prevent direct contact with the landfill contents and inhalation of dust and
volatile emissions.
The landfill is currently affecting only the shallow groundwater aquifer and
the offsite pond adjacent to the site. As was mentioned previously, the
effects on the pond will be addressed in an extended RI/FS report. There are,
however, several other environmental impacts resulting from the implementation
of alternatives.
The fence in Alternative 2 would deter large terrestrial animals from
feeding on the landfill and would deter transient populations from coming in
contact with exposed waste and leachate on the site. The grading and capping
activities in Alternatives 3, 4A, and 4B would prevent any potential risk to
terrestrial animals from direct contact with landfill contents. However, it
would also involve the removal of trees and shrubs used as nesting habitat by
birds. In addition, these alternatives would also eliminate 7.9 acres
of wetland within the landfill and 1.8 acres of wetland around the perimeter
of the landfill as a result of cap overlap. However, the cap overlap in the
vicinity of the pond could minimize the impact of the leachate seeps on the
pond. There are also five plants found on the site listed on the Delaware
Natural Heritage Inventory that would be eliminated from the landfill by
Alternatives 3, 4A, and 4B.
23
000026
-------
CrHeria
Short-TeB
Effeclivene5S
Long-Te.-
EffecU veness
N
~
IleducUon of
toxicity,
Mobil1tr, and
Voluao
hlpleaenh-
bil1tr
C~
o
o
=>
TV
-.J
Alternative I
No Aclion
SHe rea41ns
unchanged.
No present
threat to
oo88Untt r .
lapact off-
sHe pond.
Not protec-
Uve or
effecUve.
Hu potenUal
for future
rhk.
No reducUoo
of todcity
BOb 11 it Y and
volume.
EaaJ to Ui,pl.-
III4W t.
Table 2
SIIHHARY OF DL'TAILID ANALYSIS 0.. ALTrnNATIVES
WILDCAT LANDFILL FS
AlternaUve 2
Institutional Control
and tIonttorinq
"eDOe aUe an4 poOl t
81\1118. MonUor
groundltater.
Slight increase in
dust during oonatruc-
tioo whieb ia estI-
aated to take OIIe
coostcuctiao aeason.
SignIficant riak of
diract contact with
landf 11 I contents.
Sol. relianoo on
fence for prevention
of direct contact.
Groundvater aonitoring
lloul4 report any fu-
ture releasea to tbe
groW14l1ater.
Sa. AlternaUv. 1.
Eaay to oonlltrucl 4114
operat..
Allewalive 3
Surface Control
t'ence sHe an4 post
slgn5. MonHor
groundvater. Grade
landfill.
Increase In dust dur-
ing construction wblcb
is estiDated to take
2 years.
Potential exists for
direct contact lIith
landfill coo tents.
Groundvater aonttoring
lloul4 report any fu-
ture releases to the
groundllatel".
IWducUon of 8Obtl1ty
by erosion control.
tUoinl oocrealla tn
volu~ and toxtcitJ
througb drug removal
~}d incineration.
Easy to conatcuct.
Potent tal for a088
AoUHl1Q.
Alternal1ve 4A
Containment with
a SoH Cap
fence site and post
slyns. MonHor
groundwater. Grade
and cap landfill with
5011.
Increase in dust dur-
Ing construction
whleb Is estl8ated to
take 2-3 years.
Low potential for
dl r..ct contact.
Groundwat..r mon-
Itoring would reveal
anr future re leases
to th.. groundwater.
Bee Alternative 3.
See Alternative 3.
AH"mal1vc 48
CoutailUllcnt with a
Soil/Clay Cap
fence 51te and post
sl'1n5. HouHor
groundwater. Grade
and cap landf111 wHh
50H/clay.
See Alternative 4A.
'"
See Alten\/.Uve 41..
See Alternative 3.
See AIt.maUve 3.
OIlREC And EI'A' 5
I'o:;t sl'1/1S, DOllltor
yrowl03waler, gradtJ,
and partially cap
landt 111 willi 5011.
See AllemalLve CA.
SOJe Alternallve CA.
See Alternative 3.
Ea:iy to C~}struct
however, utJttling
coul03 be e problem
wllh the 2 ft. cap.
-------
Criteria
COllplalnce
vith ARABs
N
l.II
o
C>
o
:::>
\j
00
Alternative 1
No Action
Does not 54t-
isfy 40 CFA
264.310 or
Delavare State
SoUd Waste
Disposal
Regulations
since no
final cover
is provided.
Alternalive 2
Institutional Control
and Monitoring
See Alternative 1.
Tuble 2
(Continued)
SUMMARY Of DETAILED ANALYSIS Of ALTERNATIVES
WILDCAT LANDfILL fS
Alternative 3
AlternaUve U
Surface Control
Containment vi th
a Sol1 Cdp
Construcllon lIust be
approved by DROC and
OOREC. Relevant 4IId
approprIate state
5011d vaste regula-
tIons requIrIng a fI-
nal cover of 2 feet Is
not lIat. The relevant
and iI,\>propriate fed-
eral requirements of
long-tera 8Inl.l&8tlon
of Infiltration and
tbe plaoeaent of a cap
vUh a p8rDeabU ity
less than or equal to
tbe paraeabl1lty of
the natural subsoil
are not satisfied,
howevor, thIs 15 a
proposed rule
1265.310(C)) uDder
Alternate Closure
wblcb when passed
would ...Ih.lnate this
requlnuaent. NPDES
penoit r,eQulred for
discharge of runoff
diverted by temporary
dlko.
. See Allemallv.. 3.
Satisfies
40 CFA 264.18(b), and
Execulive Ordors 11988
and 11999 ~or tbe
protectioo ot
floodj,)lains a..:,
Watlands.
Alten1dU ve 4U
COlltalnment wilh a
Soil/Clay Cap
Construcl1on musl be
approved by DRUC and
DNREC. I/elevant 4IId
approprlale slate
solid wasle regula-
tions requirIng a fi-
nal cover of 2 feel
Is nol mel. Tile
re levanl and al'pro-
prlala federdl re-
Qulre~nls of long-
ler8 mlni81&alloo of
InfiltratIon Is nol
mel, bul the place-
»cnl of a cap wllh a
permeability less
th40 or equal lo the
permeability of lbe
natural subsoIl is
satIsfied. 'Belter
1009-te[1ll 8Inl.ha-
tlon of infIltration.
IlPOES penait requIred
for dlschuge of
runoff diver led by
temporary cHke.
Satisfleli
40 CfR 264.18(b), 40d
EXeculive Orders 11988
and 11990 for the
protection of
floodplains and
Wellands.
DlIIU::C and EPA' s
Conslrucl1on DIlisl be
approved by LJRBC and
DNROC. Relevant and
approprIate st.ate
solid waste regula-
tIons requirIng a fI-
nal cover of 2 feet Is
mel. Tbe relevant
and approprIate fed-
eral requIrements of
long-tera 8lnl81&atlon
of 111ft Hration Is nol
lIet but the placement
of Ii cap w1th a
permeabIlIty less
,llllill or equlll lo
lhe perme4bllity of
the natural 6WJsol1
16 uall6fled. NPDES
permll requIred for
dtscharge of runoff
diverted by temporliry
dike.
Satisfies
40 CfR )64.18(b), and
Executive Orders 11988
and 11990 for lhe
proleclton of
Floodplains and
Wellands .
-------
CrHerta
Overall Pro-
tection of
Publ1c Health
and the Envl-
rOl1lllent.
Pl"eSent -WorUl
Cost.
~339/05.
N
0'-
o
o
o
:::::>
'"
c.o
Alt.ernaU ve I
No Action
Is the least
protective of
public health
and the envl-
rOOllent..
$
o
AlternaUve 2
Instltutlonal Controf
and HonHorlng
Risk of dlrect con-
tact controlled only
by fence. Rlsk of
future releases 8Onl-
tored. Rhk of
groundwater lngestlon
controlled by ad81nl-
stratlve rest.rlct.lons.
$
350,000
Table 2
(cont1nueal
Alternative 3
Surface Conlrol
Risk of direct con-
lacl, erosion, and
pondlng controlled by
grAding and revege-
tAtion. Risk of fu-
lure releGSes 8001-
tored. Risk uf
groundwaler ing~stlon
controlled by adminl-
strAtlve restrlctlons.
$6,300,000
Alternative 4A
Conlahuoeol wllh
a Soil Cap
See Allernatlve 3.
$7,500,000
Alternative 48
Containment wllh a
Soli/Clay Cap
See A Hecual! ve 3.
$8,530,000
Wkl:£: and I:PA I:;
Stt Allernalive 3.
$5,340,000
-------
. .
.The long-term effectiveness and permanence refers to the magnitude of total
residual risk in terms of untreated waste, the adequacy and suitability of
controls used to manage untreated waste, and the reliability of these controls
over time. In terms of total risk of the residual waste, only Alternatives 3.
4A, and.4B constitute any waste reduction, namely, the removal of any drums
found on the surface or through grading operations. The fact that landfill
waste will remain onsite for all the alternatives means that there is a
potential for future contaminant releases from known and unknown waste in the
landfill, although the potential and rate of release is small. This applies
to all the alternatives, including the No Action Alternative. Because the
potential for direct contact exists on the site, the No Action alternative
(which included no controls) is not reliable. Groundwater monitoring is
included in all alternatives except the No Action and should prove reliable in
reporting any future releases to the groundwater, and hence, potential
releases to surface waters. Alternative 2 would rely entirely on the fence as
the control against direct contact. The grading and capping options would
provide additional protection against direct contact and thus supply the best
direct contact protection. The grading and capping options would require the
most maintenance. All of the alternatives except Alternative 1 contain
institutional controls to prohibit all well drilling onsite and in the shallow
aquifer to the southeast of the site and along the extreme southwest edge, as
delineated in Figure 10. Since these restrictions are to be administered by
the state, it is considered a long-term remedial action. Finally, since waste
will remain onsite, a review of the effectiveness of the final remedial action
will be done in five years.
Reduction of toxicity. mobility. and volume refers to the amount of material
to be treated, the amount of hazardous materials that will be destroyed or
reduced, and the degree of expected reduction. Also, this evaluation
addresses the statutory.preference for selecting a remedial action that
employs treatment to significantly reduce the toxicity, mobility, and volume
of hazardous substances. Volume would be reduced depending on the number of
drums encountered during the remedial action and disposed of offsite. Other
than the potential for treatment of drum contents, none of the alternatives
completely treat all of the waste found onsite.
The analysis of implementability addresses the technical and administrative
feasibility of implementing the alternatives as well as the availability of
services and materials associated with each alternative. The alternatives do
not require unusual equipment or materials although the volumes of soil and
clay are considerable. However, sources of soil and clay exist within the
State of Delaware. With the exception of the offsite drum disposal, only
onsite technologies are included. Monitoring of groundwater is essential for
detecting any future releases of contaminants. The only significant
implementability issue will be construction requirements for the grading and
capping in Alternatives 3, 4A, and 4B. Since the landfill is located in
wetland areas, settlement of the cap would need .to be investigated before
construction. Also, a more detailed analysis of the potential flood
velocities in the event of the lOa-year storm of 24-hour duration should be
done targeting some of the assumptions made in the preliminary analysis
included in the Feasibility Study. This should be done for the grading and
capping options of Alternatives 3, 4A, and 4B. Implementation of state
imposed restrictions on well development both onsite and in the previously
described shallow aquifer area is not considered a problem because Delaware
27
000030
-------
.:175COO
%
!
!
;
j
I
475C(X)
DWID 4n
$ DO 500
DW13 MESTIC WELL
~. DO~ESTIC WELL ~OCATION IROUNDS 1 &
. APPROXIMATE OCATION IROUND 2 2J
':..-!!" 1IXJ] LANDFILL BOUNDARY ONL YI
- 15XJ 2(XO
SCAA..E 1" . w-" '
I
478CCO
Figure 9
~~C WELLS
DNAEC 8Y 0 0
OO~l
WldCat
Dover. ~e ~~~'I
28
-------
4*5000
475000 477500
Approximate Landfill Boundary
Area of Known or Profcable Groundwater Contamination
Area Potentially Susceptible to Groundwater Contamination
(Location of-Westam- Boundary- is- Uncertain)
478000
Domestic or Commercial Weils
in Columbia Formation
Seato
000032
Figure 10
OFFSITE GROUNDWATER CONTAMINATION
IN THE COLUMBIA FORMATION
Wildcat Landfill
29
-------
presently has this authority under t~e state well permitting program.
Further, this shallow aquifer has very low water yielding capacity and
contains naturally high levels of iron.
The evaluation of ARAR compliance by alternatives includes a review of the
state and federal applicable or relevant and appropriate chemical-specific,
action-specific, and location-specific requirements, and other concerns
identified as to-be-considered (TBC). The TBCs do not meet the regulatory
prerequisites of ARARs. These are nonpromulgated advisories or guidance
issued by state or federal agencies. In this section, the alternatives will
be evaluated as to how each meets the major ARARs for the site. A complete
list of the ARARs is found in the Feasibility Study report and Technical
Memorandum Number I, found in the Administrative Record. The ARARs used in
this analysis include the action-specific requirements of the Delaware River
Basin Commission (DRBC) , the Executive Orders pertaining to wetlands and
floodplains, 40 CFR 264.310, and the effluent limitations of the National
Pollution and Discharge Elimination System (NPDES) pursuant to Section 402 of
the Clean Water Act (CWA). Any construction activities affecting greater than
2.5 acres of wetland must be approved by the DRBC. This is applicable to the
grading and capping alternatives. A statement of findings regarding the
wetlands is included in this record of decision under statutory determinations.
Discharge into the offsite stream from the temporary diversion ditches in
Alternatives 3, 4A, and 4B would require an NPDES permit. A CWA Section 404
permit issued by the US Army Corps of Engineers is also required for the
placement of fill material within the offsite navigable waters, including the
wetlands.
The DNREC Wetland Regulations and Wetlands Act are state ARARs. Permits
for. any construction activity within offsite wetlands is required regardless of
the area affected. Wetlands ov~r the surface of the landfill and around the
perimeter of the landfill would be lost during the construction activities for
Alternatives 3, 4A, and 4B. Permits are not required for any remedial action
activities on the site in accordance with SARA.
The Delaware Regulations G~verning the Construction of Water Wells would apply
to the installation of monitor wells or other wells associated.with the
remedial actions.
The location-specific rules governing floodplains applies to remedial actions
at this site. All portions of the remedial activity must be designed,
constructed, and maintained to avoid washout by the 100-year flood. Also,
remedial activity should avoid adverse effects, and restore and preserve
natural and beneficial values. Since the landfill is partially within the
100-year floodplain, this would apply to all alternatives except the no-action
alternative.
The State of Delaware Solid Waste Disposal Regulations of 1974 and federal
RCRA closure and capping requirements (40 CFR 264.310) are relevant and
appropriate. The state solid waste disposal regulations require a cap with a
minimum 2-feet of compacted soil with a minimum 2 per cent slope on the final
grade. Alternatives 3, 4A, and 4B satisfy the slope requirement but none of
them satisfy the 2 feet of compacted soil requirement. However, the soil and
soil/clay caps are both 1.5 feet thick with an added thickness provided by the
grading fill that ranges from 0 to 4 feet.
30
OOOO~3
-------
The soil requirements of the Delaware solid waste regulations may not
practicable at the Wildcat Landfill site for three reasons: (1) the weight of
such a cap would likely alter the existing site dynamics by causing subsidence
of the landfill materials deeper into the underlying wetland sediments,
(2) the intent of the two feet of compacted cover material is to reduce
infiltration into the waste materials but at the Wildcat Landfill site this is
not a concern since the landfill is already located within a wetlands area and
decreasing infiltrating water will not alter that hydrologic feature, and
(3) the onsite risks associated with the site are from direct contact with
exposed wastes and this risk would be more cost-effectively reduced by a soil
cap.
The relevant and practicable intents of the capping option at the \olildcat
Landfill site would be better accomplished by a soil cap containing 1.5 feet
of compacted soil and 0.5 feet of topsoil. The essential 2 foot cover
requirement is, thus, met.
Closure of the landfill will be accomplished in accordance with the relevant
portions of Subtitle C of RCRA. The RCRA requirements are not applicable to
this situation because there are no site records indicating that RCRA waste
was disposed of at the site and because no RCRA characteristic waste was
identified in the study. However, in order to address the contamination
encountered at the \olildcat Landfill, the requirements of RCRA are considered
relevant. .
Since the intent of RCRA closure is generally not appropriate for large
municipal landfills where waste is generally of low toxicity, EPA has proposed
requirements for alternate closure options under RCRA (52 Fed. Reg. 8712, March
19, 1987) which may only be used where closure is not applicable ,but is
relevant and appropriate. The alternate closure options combine the elements
of clean closure and the closure in place options.
The alternate closure is considered the correct closure method for the Wildcat.
Landfill site because the pathways of potential exposure of contaminants. is
limited and the contamination remaining onsite has both low mobility and low
toxicity. The alternate landfill closure consists of the partial removal of
wastes (in this case, the removal of drums containing wastes encountered
either on the landfill surface or during the grading operation), stabilization
and containment with a soil cap (that will be permeable) to address the direct
contact threat, and long-term management controls. The long-term management
controls consist of maintenance of the site and the cap, onsite land use
restrictions, and ground water monitoring. Although the alternate landfill
closure should be used when there is'not significant threat to ground water,
the implementation of the state imposed institutional controls on well
development in the very limited area of concern is considered sufficient for
this situation. .
Alternatives 1, 2, and 3 do not meet the alternate landfill closure
requir~ments because none contain a landfill cover. Alternatives.4A satisfies
this ARAR because it consists of a soi1 cover over the entire site.
Alternative 4B exceeds the alternate landfill closure requirements because it
consists of an impermeable clay cap with a soil cover.
31
OOOO~4
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The Delaware Natural Heritage Inventory draft list of rare or seldom seen
plants is a TBC since five plants from that list have been identified on
the site. Impacts of any remedial action affecting these plants are to be
minimized, however, this does not preclude implementation of the remedial
action. Since Alternatives 3, 4A, and 4B involve earthwork on the site, this
TBC would apply to all three of these alternatives.
Section IV of this ROD summarized the contamination in the groundwater near
the site. This section showed that certain chemical-specific criteria (MCLs)
are presently exceeded in the ground water. The point of human exposure to
the contaminated ground water should normally be set at the facility boundary
unless specific criteria set forth in Section 121 (d)(2)(B)(ii) of SARA are
met. Maximum contaminant levels are not considered relevant and appropriate
at the Wildcat Landfill site since the site conditions meet the exceptions
outlined in Section 121 (d)(2)(B)(ii). For the Wildcat Landfill site it has
been determined water quality criteria in the St. Jones River are the
appropriate levels to achieve because the ground water discharges directly
into the river and there is no statistical increase in the levels above water
quality criteria. In addition, institutional controls are a part of the
selected remedy in the limited distance between the site and the points of
ground water discharge. Finally, current and projected risk levels and
reference doses (RfD's) for offsite ground water ingestion is within the risk
range considered acceptable by EPA.
Alternative 1 does not meet this ARAR because it is a no action without
institutional controls and monitoring. However, Alternatives 2, 3, 4A, and 4B
meet this requirement since they all contain institutional and mopitoring
controls in the distance between the site and the points of ground water
discharge to the St. Jones River.
The overall protection of human health and the environment criterion refers to
how each alternative eliminates, reduces, or controls existing and potential
risks to human health and the environment through treatment, engineering
controls, and/or institutional controls. All alternatives, except
Alternative 1, control the ingestion of contaminated groundwater by
administrative restrictions and monitoring for future releases. Alternative 2
reduces only the risk of direct contact. Alternatives 3, 4A, and 4B reduce.
the risk of direct contact and erosion of the landfill contents and could
reduce the impact of the leachate seeps into the offsite pond.
All of the final alternatives are also evaluated on a cost basis. The cost
estimates are within +50% to -30% cost range in accordance with EPA policy.
They represent the best estimation of the capital, operation and maintenance,
and total present worth costs. Costs will only be updated at the pre-design
and final design stage. Since the capital costs are the highest for the
soil/clay cap alternative, that alternative has the highest present worth of
approximately $8.5 million. The costs for the alternatives from the detailed
analysis is as follows: Alternative 1- $0.00; Alternative 2- $350,000;
Alternative 3- $6.3 M; Alternative 4A- $7.5M; Alternative 4B- $8.53 M. The
cost for the preferred alternative is $5.4 M.
There are uncertainties involved with the cost estimates that are important to
note. The level of personal protection required during the grading and
capping alternatives is uncertain. Landfill gas and vapors could be emitted
32
0000,':(5
-------
with disturbance of the landfill contents. Since the composition of the
landfill gases has not been characterized, Level B protection would be
required. However, future monitoring and sampling may prove that the landfill
gases do not present any danger which would lower the degree of personal
protection for workers. Should this be the case only Level D protection would
be necessary. In order to provide a conservative cost estimate it was assumed
that Level B and Level D personal protection would be used 50% of the time
during grading and cap construction. Another uncertainty involves the
sampling, removal, excavation, and treatment of the drums in an offsite RCRA
incinerator. The number and contents of drums on and in the landfill is
unknown. Based on estimates made from visual inspection of the landfill and
the excavated trenches, a number of 160 drums was used for the drum count as
the number of drums containing hazardous waste requiring offsite incineration,
that are currently on or could be uncovered, during the grading operation.
The community acceptance criterion indicates those features of th~
alternatives the community supports, those for which they have reservations,
and those for which they strongly oppose. This evaluation is based upon
comments submitted to either the state or EPA as well as those made at the
public meeting.
IX. Community Relations
The Wildcat Landfill site is located in a moderately populated area 2 1/2
miles southeast of Dover in Kent County, Delaware. Private residences are
found along Route 10 to the north and west of the site.. The site owner's
resisence is located directly adjacent to the site to the south. A number
of small businesses are located directly adjacent to the site to the southwest.
An archery range is situated on property presently owned by the landfill owner
and is situated between Route 10 and the northwestern edge of the landfill.
Dover Air Force Base housing is located directly across the St. Jones River
from the landfill.
Local officials were briefed by DNREC prior to initiation of the remedial
investigation in 1985 and again following completion of the Proposed Plan in
June 1988. A fact sheet was prepared and distributed to the local residences.
and businesses prior to the remedial investigation which described the RI/FS
process and discussed the site-specific problems. Press conferences were held
at the site prior to the initiation of field activities during both the first
and second rounds of sample collection. Press releases were also issued by
DNREC to the news media during the investigation and when the proposed plan
was issued.
A public meeting was held on June 16, 1988 to discuss the proposed plan and to
obtain public comment on that plan. Letters were sent to the businesses and
residences located very near to the site inviting them to the public meeting.
A 30-day public comment period was held by DNREC and EPA from May 26, 1988 to
June 24, 1988. The administrative record was made available for public review
both near the site and at EPA Region III offices. .'
DNREC and EPA have attempted to respond to all public comments in the attached
responsiveness summary (Appendix B).
33
OOOO~6
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X. Documentation of Significant Changes
No significant changes to the preferred alternative presented in the proposed
plan have occurred.
XI. Recommended Alternative
The selected remedy chosen by the lead agency must a cost-effective remedy
which effectively mitigates and minimizes threats to and provides
adequate protection of human health and the environment. Both CERCLA and SARA
require selection of a remedy which provides protection of human health and
the environment which is cost-effective and utilizes permanent solutions and
alternative treatment technologies or resource recovery options to the maximum
extent practicible, and that at~ains federal and state ARARs unless otherwise
waived. In addition, treatment of the principal threat at the site to reduce
the mobility, toxicity, and volume of the hazardous substance is preferred.
The remedy selected for the Wildcat Landfill site, excluding final decision on
addressing the adjacent pond, is discussed below.
A. Description of the Selected Remedial Alternative and Performance Goals
A modified version of Alternative 4A, Containment With a Soil Cap, has been
chosen to mitigate the existing and future risks posed by the site and which
meet the goals and objectives, and federal and state ARARs. This alternative
includes the institutional controls and monitoring requirements detailed in
Alternative 2 and included in Altern~tive.4A. The major difference between
the chosen modified alternative and Alternative 4A is that only those areas on
the site which pose a direct contact risk will be capped and that the cap will
meet the intent of the Delaware solid waste regulations. As was mentioned
previously, the two-foot c~mpacted soil requirem~nt may not be practicable for
the reasons previously detailed. Chapter 6 of the Feasibility Study describes
the chosen alternative and estimates the total- cost for that alternative.
This preferred alternative would require all the institutional controls
described in Alternative 2 onsite and in offsite areas identified as potential
problem areas. The purpose of these restrictions is to prevent direct contact
(primarily through ingestion) with landfill contents or contaminants
originating from the landfill. Fencing is not chosen for inclusion in
this alternative for the following reasons: (1) the limited soil cap was
chosen as the more long-term remedy for reducing the future onsite risks, .
(2) difficulty in constructing a fence because of the number of property owners
who would be effected, and (3) access to the site is limited by the
surrounding land-use and terraine features. A very limited soil cap (both
areally and physically) similiar in design to that described in Alternative 4A
will be placed on areas of the landfill where wastes are exposed or where
leachate seeps or pools are found. These areas will be graded, covered with
soil and seeded. Further, any drums exposed on the landfill surface or from
the graded areas will be disposed of offsite in either a solid waste landfill,
or in a RCRA incinerator if the contents are determined to be hazardous.
Hazardous wastes will not be disposed of at RCRA landfills in deference to the
land ban on disposal of hazardous waste. However, no RCRA characteristic
hazardous wastes were encountered during the remedial investigation.
34
('\OOO~7
-------
The general" features of the preferred alternative is as follows:
1. Institutional controls will be implemented by the state in areas adjacent to
the site to prevent the installation of water wells in the surface aquifer that
is downgradient of the southwestern edge of the site. These controls will be
implemented by the state using the existing water well permitting program.
This area discharges into the St. Jones River and Tidbury Creek. The ARAR
associated with this aspect of the chosen alternative is the Delaware
Regulations Governing the Construction of ~ater ~ells.
2. Institutional contr?ls will be implemented by the state which preclude
onsite installation of water wells for domestic or commer~ial purposes.
Construction activities which would disturb the integrity of the soil cap on
the site will be discouraged. The existing state well permit program will
preclude onsite water well construction under the Regulations Governing the
Construction of ~ater ~ells. The Delaware Solid ~aste Regulations will be the
ARAR used to discourage onsite development which would disturb the integrity of
the site. Also, the state will work toward including language in the deeds of
site owners, or other legal means, at least describing the landfill location
on th~ property. .
3. Two commercial wells, D~-8 and D~-lO, located adjacent to the site in an
area of concern will be replaced. The shallow wells presently existing would
be replaced by single-cased wells to approximately 200 feet below ground
surface. The installation of these wells would be according to the Delaware
Regulations Governing the Construction of ~ater ~ells.
4. Exposed landfill wastes, ba~ren areas, and leachate pools or seeps will be
covered according to the intent of the Delaware Solid~aste Regulations of 1974
which includes 1.5 feet of uncompacced and 0.5 feet of topsoil cover, minimum
2 per cent slope, and revegetation. Consideration will be given to the other
TBC's identified such as the DNHI draft list and to the existing natural uses
of the site such' as areas of imp.ortant wildlife habitat value. The RCRA
alternate landfill closure policy will ~lso be used to meet the RCRA relevant
and appropriate requirements. Also, ~hould the volume of cover required to
meet the ARAR's be impracticable because of site-specific concerns, such as
subsidence because of excessive weight, DNREC and EPA will decide on the
actual cover requirements to be met.
5. Offsite disposal of drums containing wastes to either a solid waste
landfill or a RCRA incinerator depending on whether the waste is hazardous or
not. The RCRA requirements will be the appropriate ARARs for offsite
transportation and disposal of hazardous wastes. Disposal of non-hazardous
wastes will done in accordance with the De1aware.So1id ~aste Regulations.
6. Signposting to discourage disruption of the soil cap.
7. Monitoring of groundwater downgradient of the site will be done in
compliance to RCRA, Subpart F to identify changes in the release of
contaminants from the site. This is particularly important in the southeastern
area near the owner's residence.
8. Shallow monitor wells will be installed in the groundwater discharge area
of the southwestern corner of the landfill along Tidbury Creek to insure that
3S
OOOO~8
-------
the Federal Water Quality Criteria are not exceeded above background levels at
the discharge point. Monitor well construction will be done in accordence
with the Delaware Regulations Governing the Construction of Water Wells.
Sampling will be done along with the other monitoring activities at the site.
The Clean Water Act is the appropriate federal ARAR.
Since much of the site is well vegetated with limited cover material in place,
the existing direct contact risk is only associated with those areas where
waste materials are exposed or where leachate seeps or pools are found. '
Institutional controls taken by the state will be imposed to prevent the
future direct contact risks identified in the risk assessment.
I '
I
I
The performance goals are met where the intent of the Delaware Solid Waste
Regulations and the RCRA alternate landfill closure requirements are achieved
on the site. The Federal Water Quality Criteria standards will be monitored
offsite at surface water discharge' points and within the groundwater monitoring
wells between the landfill and the surface water discharge area. The'
institutional restrictions will be placed by the state to insure that the
onsite and offsite restrictions are placed upon the property. This will
include water well installation restrictions and declarations in property deeds
that landfilling has occurred within the property boundary.
The following statement of findings regarding the wetlands is also considered
as a TBC. (1) The RIfFS for the Wildcat Landfill site has determined that,
wetlands onsite and adjacent to the site may be graded and covered in order to
eliminate the existing leachate seeps and provide cover to exposed wastes in
areas that constitute an unacceptable risk to public health and the
environment. All remedial alternatives except the No Action Alternative will
require grading and covering of certain of these areas. (2) The grading and'
filling activities shall be conducted in a manner consistant with provisions
of Appendix A of 40 CFR Part 6. The subject regulations have been entitled
"Statement of Procedures on Floodplain Management and Wetland Protection."
These procedures constitute policy and guidance for carrying out provisions of
Executive Ord~r 11990 which addresses Protection of Wetlands. (3) The
remedial design of the remedial action shall be developed in a manner
consistant with Appendix A of 40 CFR,Part 6 to assure that potential harm and
adverse effects to the wetlands is minimized. The remedial design has not
been initiated at this time. Therefore, specific steps to minimize impacts
have not yet been identified. In addition, the effect of the remedial action
on the wetlands cannot be accurately assessed at this time. (4) While all
remedial measures shall be designed to minimize harm to the wetlands, it is
possible that some adverse effects may be unavo~dable. Should ~emedial
activity be expected to create such effects, restorative or mitigative measures
shall be developed during the remedial design and reviewed by DNREC.and EPA.
If anticipated adverse effects occur, restorative or mitigative measures may
be implemented as part of the remedial action.
B. Statutory Determinations
The purpose of this section is to describe the ability of the selected remedy
to be consistant with the statutory requirements of Section 121 of CERC~and
will describe the adequacy of the remedy to be protective of human health and
the environment, attain ARARs, be cost-effective, utilize permanent solutions
36
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and alternative technologies or
extent practicable, and address
mobility, or volume.
resource recovery technologies to the maximum
the preference for reduction in toxicity,
Protection of Human Health and the Environment
The selected remedy is adequately protective of human health and the
environment through the alternate closure engineering of the landfill surface,
removal and treatment of drums containing wastes, and the onsite and offsite
institutional controls to be imposed by the state. The existing direct
contact risks from exposed waste, leachate seeps and pools found onsite will
be eliminated by the alternate closure soil capping to be placed in areas of
the site where direct contact exists. Stabilization of the surface eliminates
the human exposure to the wastes and also reduces the exposure of the
biological community to waste materials. The future direct contact risks to
humans will be minimized. by the institutional controls to be placed on the site
for water well drilling and construction activities. Signposting will also
discourage onsite exposure.
The selected alternative will not pose unacceptable short-term risks although
the grading and the offsite disposal of drums have low short-term risks
associated with them. There should be no cross-media impacts from the
selected media since all waste materials will remain in place except the drums
which are to be disposed of offsiste.
Attainment of the Applicable or Relevant and Appropriate Requirements
The selected remedy for addressing the problems posed by the Wildcat Landfill
site meets the intent of the applicable or relevant and appropriate
requirements of both Federal and any more stringent State environmental and
public health requirements. A number of Federal and State to be considered
(TBC's) have also been identified and are included in this discussion. The
MCL requirement in ground water at the facility boundary has been waived.
because of the special conditions present at the site. These special
co~ditions include the very limited aquifer area, lack of receptors,close
proximity to the surface discharge, and low yield and quality of the section
of aquifer in question. The intent of the Delaware Solid waste Disposal
Regulations will be met by meeting the state closure requirements found in the
Delaware Sanitary Code, Part 38, under which the site was originally to be
closed.
The complete listing of State and Federal ARAR's and TBC's are found in the
Feasibility Study report and Technicai Memorandun #1, both found in the
Administrative Record.
The chemical-s~ecific requirements are:
1. 40 CFR 122 (Clean Water Act) - This is a relevant and appropriate
requirement which includes the acute and chronic ambient water quality
criteria (WQC) for protection of freshwater aquatic life. At the Wildcat
Landfill site these requirements ar~ to be met at the ground water
discharge point along Tidbury Creek.
.
, .
37
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2. 40 CFR 122 (Clean Water Act)
Standards are applicable for
landfill capping activities.
- The Federal Pollution Discharge Elimination
the discharge from the landfill during
3. The State of Delaware Regulations Governing the Control of Water Pollution -
The applicable requirements involve the discharge of waters to surface
water and this applies to the onsite landfill capping action during
construction. A permit would be required since water would be discharged
offsite.
4. The State of Delaware Water Quality Standards for Streams - This is an
applicable state requirement for discharges to surface waters from point
sources. These requirements are enforced under the Delaware Regulations
Governing the Control of Water Pollution.
The location-specific requirements are:
1. State of Delaware Regulations Governing the Construction of Water Wells-
This is an action-specific requirement concerning the construction and
siting of. water wells. These requirements are applicable to remedial
actions for both monitor well construction and replacement of .domestic
wells.
2. State of Delaware Wetland Regulations and the Wetlands Act (Chapter 66) -
These location-specific requirements are applicable to all remedial actions
which impact the existing tidal wetlands. The capping actions at the
Wildcat Landfill site will impact both onsite and offsite wetlands and
measures must be taken to minimize these impacts. A permit is required.
3. Delaware River Basin Commission (DRBC) Rules of Practice and Procedure
This applicable requirement applies to actions where 2.5 or more acres of
wetlands are drained, filled, or otherwise altered. An environmental
impact analysis is required.
4. 40 CFR 264.l8(b) - Actions within the 100-year floodplain must be designed,
constructed, operated, and maintained to avoid washout..
5. Executive Order 11988, Protection of
This applicable requirement requires
minimize potential harm, and restore
values.
Floodplains (40 CFR 6, Appendix A) -
actions to avoid adverse effects,
and preserve natural and beneficial
.6. Executive Order 11990, Protection of Wetlands (40 CFR 6, Appendix A) -
Measures must be taken to minimize the destruction, loss, or degradation of
wetlands. .
7. Clean Water Act, Sec~ion 404 (40 CFR Parts 230, 231) - Action must be taken
to prohibit discharge of dredged or fill material into wetlands without a
permit.
The action-specific requirements are:
1. State of Delaware Solid Waste Disposal Regulations (1974) and the State
Sanitary Code Part 38 - Section 6.03(g)(1) of the solid waste
38
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regulations requires a final slope of at least 2 per cent which precludes
erosion. A minimum of two feet of compacted cover is also required in
Section 6.03(g)(4)(b). The actual cover requirements will be a two foot
soil cover but the compaction requirements will be modified as described
previously with 1.5 feet of compacted and 0.5 feet of uncompacted topsoil.
2. 40 CFR 264.310 - The RCRA closure requirements will be met under the EPA
alternate landfill closure policy allowing the site to be suitably covered.
This is a relevant and appropriate requirement.
3. 40 CFR 264 - The RCRA hazardous waste requirements will also be applicable
to the transportation and disposal of any hazardous wastes found in drums
either on the iandfill surface or during the grading actions.
The to be considered (TBC's) are:
1. Delaware Natural Heritage Inventory - This is a draft list of rare or
seld~m seen plants which have been found on the site. These plants will be
considered during the onsite grading and capping activities.
2. Integrated Risk Information System data base - This information is used in
determining the concentration of carcinogenic compounds at the 10-6
risk level and the concentration of non-carcinogens for the reference dose
level.
3. 45 FR 79318-79379 (November 28, 1980) - These are levels for contaminants
in water for the protection of human health.
Cost-Effectiveness
The selected remedy attains ARARs and mitigates the onsite and offsite risks
to human health and the environment while the cost is less than the other
remedies (3, 4A, and 4B) that include the onsite soil capping option. The
. selected remedy is also much more sensitive to the 'other to-be-considered
requirements such as the rare plants than the other remedies.
The selected remedy is considerably more costly than the no action alternative
and Alternative 2. However, these alternatives are not effective in
addressing the identified risks over the long-term nor do they meet the
federal and state ARAR's.
Utilization of Permanent Solutions and Alternative Treatment Technologies
The final feasibility study report describes the modified alternative chosen
to remedy problems posed by the site. This selected remedy differs from the
detailed alternatives 1, 4A, and 4B by reducing the area of the landfill to be
covered with a soil cap. This was done for two reasons: (1) certain areas of
the site are already covered and very well vegetated with adequate slopes and
(2) sensitive wetland and open water environments are directly adjacent to the
site with certain areas of the site having reverted to wetland-like
conditions. Any grading, capping and revegetation would not improve over the
existing site conditions.
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The selected remedy is as protective of human health as Alternatives 3, 4A,
and 4B because the same existing and future direct contact risks are mitigated
but at a lower cost. Further, the selected remedy is more protective of the
environment since the areas of the site which are stable and already provide
value to the biological community are left intact and because encrouchment of
the cap near the wetlands and the pond is reduced considerably. Both the
short-term and long-term effectiveness of the selected remedy both for the
soil capping and the institutional controls are as good as the other
alternatives where capping is detailed. Further, the replacement of certain
wells adjacent to the site is very effective and precludes the need for
monitoring in that area and is thus more cost-effective. The implementability
of the institutional controls, particularly for restricting water well
development, will be straightforward as the state well permitting program is in
place with the state authority to approve or deny water well development. The
placement of deed restrictions is less straightforward but would be
accomplished by the state through mechanisms recently developed by the DNREC
Solid Waste Branch for active landfill facilities. .Although authority does not
exist at the state level to specifically preclude all activities on the
landfill, language either placed in deeds .or as declarations to the deed which
state the presence of the landfill will preclude activities on the landfill.
These institutional controls would be permanent controls as would the onsite
capping and offsite water well replacement. The toxicity of contaminants
within the landfill will not be reduced as no treatment of landfill contents
will occur (except for drum wastes found to be hazardous). The mobility of
contaminants offsite is presently reduced considerably by the presence of the
organic silts beneath much of the landfill and the hydrologic groundwater
regime existing in the vicinity of the river. The short-term effectiveness of
the cap in reducing infiltration and altering the existing evapotransporation
regime will not be as good as the existing site conditions since areas to be
graded, covered with soil, and revegetated are presently vegetated with a wide
variety of flora. However, this will likely not increase the mobility of the
onsite contaminants since surface drainage controls will be in place during the
grading activities. .
Summarily, the selected remedy is found to be the more cost-effective while at
the same time addressing the onsite and offsite risks identified in the
remedial investigation. Further, the remedy is as effective both in the
short-term and the long-term as the other alternatives which include soil
capping.
Preference for Treatment as a Principal Element
The selected remedy will be using incineration as the only. permanent treatment
and this will apply only t~ the contents of drums found either on the surface
of during the grading of certain areas of the landfill where these contents
are determined to be hazardous wastes. The remedial investigation did not
identify areas of the landfill which would require special treatment
except where drums are found nor did the risk assessment identify existing
unacceptable offsite risks to human health which would be associated with the
landfill. Finally, the very large area and volume of the landfill precluded
any prac.ticable treatment of a11 the landfill wastes.
lo'.;"
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APPENDIX A: Administrative Record Index
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APPENDIX B: Responsiveness Summary
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~ildcat Landfill - Responsiveness Summary
Section 117 CERCLA, as amended by SARA, requires that a proposed plan be made
available for public review. DNREC and EPA have accepted comments on the
Proposed Plan and the draft Remedial Investigation/Feasibility Study reports
beginning May 26, 1988, and ending June 24, 1988. A public meeting was held on
June 16, 1988, at the DNREC building auditorium in Dover (Kent County),
Delaware to discuss the findings of the remedial investigation, present the
alternatives developed to mitigate the problems posed by the site, and present
the preferred alternative of DNREC and EPA.
During the public comment period, comments were submitted by Playtex, Inc.
This Responsiveness Summary summarizes their comments by topic, followed by
the DNREC and EPA response to these concerns and comments.
~ritten comments received from Playtex Inc. (received by DNREC and EPA on June
2 3, 198 8) :
1. Comment:
The 30-day public comment period does not meet the Section 1l7(a) CERCLA
requirement that a reasonable opportunity for public comment be provided by
the agency since the study had lasted 8 years. Also, the preferred
alternative was not announced until one week before the expiration of the
public comment period.
Response:
First, the National Contingency Plan (NCP) presently requires a 21-day
comment period for remedial action plans. The revised NCP, not yet'.
adopted by EPA, has proposed a 30-day public comment period. Thus, the
30-day comment period chosen by DNREC and EPA for the ~ildcat Landfill
public comment period exceeds the requirements of the existing Nr.? This
decision is also consistent with EPA Region III policy. The 30-day comment
period is regarded by DNREC and EPA as "providing reasonable opportunity"
for public comment on the Administrative Record and the Proposed Plan.
Second, the Proposed Plan, which outlines the preferred alternative, was
made available to the public at the beginning of the 30-day comment period
as part of the Administrative Record, not one week before the close of the
public comment period. Notice in the local newspaper and other media
outlined the preferred alternative and provided notice of the public
meeting. Copies of the Proposed Plan were also available at the Dover
Public Library and the offices of DNREC and EPA Region III. The Proposed
Plan provided a brief analysis of the preferred alternative as required by
CERCLA Section l17(a)(1).
Third, the remedial investigation field work was initiated in December
1985 and the Proposed Plan was made available in May 1988. The RI/FS and
Proposed Plan were completed in 2-1/2 years and it was primarily these
findings that were used by DNREC and EPA in developing the preferred
alternative found in the Proposed Plan and the Record of Decision.
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2. Comment:
The remedial plan is expensive and not cost-effective when compared to the
risks that are posed by the site. The reports and studies are speculative,
particularly where risks are evaluated. The institutional control and
monitoring plan would be a cost-effective solution in accordance with
Section 121(b) of CERCLA with respect to the risks found at the site.
Covering rather than capping would be.tter limit contact by unauthorized
persons.
Response:
First, the preferred alternative and the evaluation of. all the alternatives
found in the RIfFS, Proposed Plan, and Record of Decision, must consider
eIght criteria when evaluating alternatives, namely, short-term
effectiveness, long-term effectiveness and permanence, reduction in
toxicity. and mobility and volume, implementability, compliance with
applicable or relevant and appropriate Federal and State requirements,
overall protection of human health and the "environment, cost, and community
and acceptance. The preferr~d alternat'iv.e was chosen by DNREC and EPA to
provide a remedy which gives the best balance possible among the eight
criteria. '
Second, risk assessments must include many assumptions as to the exposure
and effects of exposure on humans. The approach utilized for the ~ildcat
Lan~fill risk analysis is generally a worst-case scenario which is very
protective of human health. Because of th~,assumptions that must be taken
in risk analyses, very definitive statements cannot be made. Rather,
probabilities must be used resulting in the need for words such as "could"
and "may". .
Third, the monitoring and institutional controls alternative was not
. selected because it did not meet the requirements for long-term
effe~tiveness and permanence, and compliance with applicable or relevant and
appropriate requirements. Nor were the existing direct contact risks and
future direct contact risks addressed solely by that alternative. However,
aspects of that alternative are part of the preferred remedy.
Fourth, the preferred alternative proposed a soil cover in lieu of the soil
caps in alternatives 4A and 4B. The soil cove'r proposed consists of
1.5 feet of compacted soi1 and 0.5 feet of uncompacted soi1 for vegetation.
The purpose of the soi1 cover is to (1) limit the direct contact risks
identified in the risk assessment, (2) prevent erosion from a lOa-year
storm event, (3) provide for stable vegetative cover ,. and (4) meet the
minimum applicable or relevant and appropriate state and federal
requirements. The soil cover that has been chosen is, necessary to meet
these requirements.
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3. Comment:
The projected overhead and administrative costs are disproportionately high
and therefore not cost-effective.
Response:
The high contingencies included in the Feasibility Study are based on the
uncertainties associated in developing an alternative without doing the
actual design. These contingency costs are actually lower in the preferred
alternative as more detailed information was given to the contractor in
estimating the cost of the preferred alternative. These costs are detailed
in Chapt~r 6 of the final Feasibility Study report.
4. Comment:
Alternatives 3, 4A, and 4B are extreme in meeting the problems posed by the
" site.
Response:
The primary objective of the Feasibility Study is to develop a range of
waste management options that protect human health and the environment.
These are to include the no-action alternative. The list of alternatives
are developed coincident with the' Remedial Investigation while the problems
and risks posed by the site are ~eing e~aluated. Consequently, the agencies
require a range of alternatives which will be able to address those problems
and risks posed by the site. In "the case of the Wildcat Landfill preferred
remedy, a modified version of Alternative 4A was chosen. DNREC and EPA
agreed that to grade and cap the entire"surface of the landfill was not
warranted and that to do so would cause unacceptable environmental
degradation by destroying the established vegetative cover, especially the
7.9 acres of onsite wetlands and the 1.9 acres of offsite wetlands
contingent with the landfill. The intent of the preferred remedy is ..0
grade and cover with soil those areas of the landfill which are pre~ently
barren, contain leachate seeps, or allow water to pond on the surface.
S. Comment:
The decision to study further the pond is unwise and inconsistent with the
goals of CERCLA.
Response:
CERCLA investigations and actions must consider environmental impacts of
.sites which may not include purely human health concerns. The decision
.to separate the pond into a separate operable unit was done to allow the
U.S. Fish and Wildlife Service to (1) determine the impacts of elevated
levels of certain metals in fish upon migratory birds feeding in the pond,
and (2) determine whether the metal accumulations found in turtles in the
pond are a concern. Rather, it will be an extension of the original RI/FS
and with a very limited scope. This study will not include a new RI/FS.
'Both EPA and DNREC will be working toward a quick turnaround for this
determination. .
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12.
REPORT DOCUMENTATION' 1. REPORT NO.
r . PAGE I EPA/ROD/R03-88/052
4. . Ti~le. and Subtitle
SUPERFUND RECORD OF DECISION
Wildcat Landfill, DE
First Remedial Action
Author(s)
9. Perlormina OF1raniution Name and Add,ess
12. SpOnsorina O,ganization Name and Add,ess
U.S. Environmental Protection
401 M Street, S.W.
Washing~on, D.C. 20460
Agency
15. Supplementary Notes
3. Recipient"s Accession No.
5. Report Oate
06/29/88
6.
I
8. Perlormina Organization Rept. No
10. Project/Task/Work Unit No.
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11. ContracteC) or G,anteG) No.
ec)
(G)
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13. Type of Report & Period Cove,ea !
800/000
14.
L-
16. Abstract (Limit: 200 words) .
The Wildcat Landfill site is located 2.5 miles southeast of Dover in Kent co~ntj,
Delaware. The 44-acre site is bordered to the north and east by the St. Jones River a00
its associated wetlands, and to the south and west by residential and com~ercial develop-
ment. A pond, created by construction of the landfill, is located directly adjacent to
the site along the northwestern edge. The pond .is th'e subject of a second operable unit
for the site. Portions of the site lie within the 100-year floodplain of the St. Jones
River. The site was operated. as a permitted sanitary landfill between 1962 and 1973,
~ccepting both municipal and industrial wastes. Industrial \vastes suspected to have been
lisposed of include latex waste and paint sludges. Throughout its 11 years of operation,
the facility routinely violated operating and other permits lssued by regul&tin3 agencles.
EPA began investigating the site in.1982. Typical wastes encountered at the site in~luded
municipal refuse latex in strips and sheets; scattered crushed, empty, or intact dru~s;
and manufactured plastic items. Much of the waste is located on low-lying wetland
sediments; however, the area to the southwest was excavated and backfilled with wastes.
Consequently, in that area of the landfill, wastes are in direct con:act with the
surficial sand aquifer. The primary contaminants of concern affecting the soil 3nd ground
water are VOCs including benzene, other organics including PCBs, and metals including
arsenic and lead.
(See Attached Sheet)
17,..,Oocument A!I.I~is .a. 04l.S~riptors
~ecora 0[UeC1SlOII
Wildcat Landfill, DE
First Remedial Action
contaminated Media: gw, soil
Key contaminants: metals (arsenic,
b. Identifiers/Open-Ended Terms
c. COSATI Field/Group
..... A.vailability Statement
(See ANSI-Z39.18)
!-
-
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lead}, organics (PCBs), VOCs (benzene)
See Instructions on Reverse
119. Security Class (This Report)
None
I ':. No. of Pages
51
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20. Security Class (This Page)
None
22. Price
OPTIONAL FORM 272 (4-771
(Formerly NTlS-35)
Department of Commerce
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"-
EPA/ROD/R03-88/052
Wildcat Landfill, DE
First Remedial Action
16.
ABSTRACT (continued)
The selected remedial action for this site includes: grading, installation of a soil
cover, and revegetation of onsite direct contact risk areas; removal and offsite
disposal of drums containing wastes by landfilling. (if not hazardous) or incineration
(if hazardous); replacement of two domestic wells adjacent to the site; institutional
controls including well and land use restrictions; and groundwater monitoring. The
estimated present worth cost for this remedial action is $5,400,000.
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Declaration for' t~e Record of Decision
Site Name and Location
Wildcat Landfill
Kent County, Delaware
Statement of Basis
This decision is based upon the administrative record for the Wrldcat Landfill
site. The attached index identifies the items which comprise the
administrative record.
Statement of Purpose
This decision document presents the selected remedial action for the Wildcat
Landfill site. developed in accordance with the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980, as amended .by the Superfund.
Amendments and Reauthorization Act of 1986, and'to the extent practicable,
the National 011 and Hazardous Substances Pollution Contingency Plan
(40 CFR Part 300).
The State of Delaware concurs with the selected remedy.
Description of Selected Remedy
This operabla uni.t, consisting of the landfill and certain adjacent areas
except the pond., 5.s the first of two for the site. The first operable unit
addresses the sour.ce of contamination by eliminating the existing direct
contact risks posed on the landfill. This first operable unit'also addresses
the potential onslte and offsite direct contact risks posed by contaminated
ground waters. The secon~ operable unit will involve continued study and
remediation of the pond directly adjacent to the landfill.
The major components of the selectp.d remcrly for this operable unit include~
-- Institutional restrictions on all water well installations on the site;
-- Institutional restrictions on
in areas adjacent to the site
potential risk;
all shallow aquifer water well installations
which have been identified as at some
-- Grading, soi1 cover, and revegetation of areas onsite where direct
contact risks have been identified. This will be done in accordance
the Delaware Solid Waste Disposal Regulation, Augu~t 1974;
with
-- Removal and offsite disposal of drums containing wastes and
either by landfilling (if not hazardous) or incineration at
incinerator (if hazardous);
drum contents
a permitted
-- Replacement of two domestic wells adjacent to the site which have been
identified as being potentially at some risk from the site;
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-- Institutional restrictions on commercial and residential building
development on the site;
- - Installation of monitoring wells adj acent to Tidbury Creek to monitor
the quality of ground water discharges;
-- Groundwater monitoring to ensure the effectiveness of the remedial action;
DECLARATION
The selected remedy is protective of human health and the environment, attains
Federal and State requirements that are applicable or relevani and
appropriate to this remedial action, and is cost-effective. This remedy
utilizes permanent solutions and alternative treatment technologies tp the
maximum extent practable for the site. However, because treatment of the
principal threats of the site was not found to be practicable, this remedy does
not satisfy the statutory preference for treatment as a principal element of
the remedy. The size of the landfill and the fact. that there are no onsite
hot spots that represent major sources of contamination preclude a remedy in
which contaminants effectively could be excavated and treated.
Because this remedy will result in hazardous substances remaining onsite above
health-based levels, a review will be conducted within five years after
commencement of remedial action to ensure that the remedy continues to provide
adequate protectlon of human health and the environment.
~?k
DAT
PhilLip
Directo
D~vision of Air ~nd Waste Managem nt
Department of Natural Resources and
Environmental Control
State of Delaware
J /
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c=-;) 7- ~1
L~'
DATE
James M. Seif
Regiqnal Administrator
EPA Region III
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