United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R03-92/146
March 1992
&EPA Superfund
Record of Decision;
Chem-Solv, DE
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NOTICE
The appendices listed in the index that are not found in this document have been removed at the request of
the issuing agency. They contain material which supplement, but adds no further applicable information to
the content of the document All supplemental material is, however, contained in the administrative record
for this site.
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50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA/ROD/R03-92/146
3. RSCIplMn • AOQKMMOft NO.
4. THtowdSubtm*
SUPERFUND RECORD OF DECISION
Chem-Solv, DE
First Remedial Action - Final
5. Report Date
03/31/92
9. Performing Organization Na
11. Confract(C)orGnnt(G)No.
(C)
(G)
12. SpemorkigOrganlztlioriNaRMandAddnM
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
13. Typ» of Report * Period Conrad
800/000
14.
15. Supplementary NolM
PB93-963906
IS. Abstract (Limit 200 word*)
The Chem-Solv site, located in Cheswold, Kent County, Delaware, occupies approximately
one-third of a 1.5-acre property and consists of a one-story concrete building, a
distillation process building, and a concrete pad used for drum storage. Surrounding
land use is mixed agricultural, residential, and commercial strip development. In the
vicinity of the site, the Columbia Formation functions as a thin water-table aquifer
and is a potential source of drinking water in the area. From 1981 to 1984,
Chem-Solv, inc., used the facility to purify spent industrial solvents and store the
distillation residues, known as * still bottoms,* for offsite disposal as hazardous
waste. After an explosion and fire at the facility in 1984, during which stored
solvents ran off the concrete pad, a state investigation concluded that this incident
and prior hazardous waste handling violations had resulted in soil and possible ground
water contamination of the site with VOCs. After Chem-Solv failed to comply with a
state order, the state removed 1,300 cubic yards of contaminated soil and a portion of
the storage pad and implemented a ground water treatment system that operated from
1985 until 1988. This ROD addresses the ground water contamination in the Columbia
(See Attached Page)
DE
17. Document Anatyele e. Deecrlpleri
Record of Decision - Chem-Solv,
First Remedial Action - Final
Contaminated Medium: gw
Key Contaminants: VOCs(benzene, PCE, TCE, toluene, xylenes), metals
(manganese.)
«dT«
c. COSATI Reid/Group
1S. AvaUaMttr State
1». Security Claee (TMe Report)
None
20. Security Cten (Thto P^>)
None
21. No. of
72
22. Prto.
(Sw MO-Z3S.H)
(FofRMrty KTB-35)
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EFA/ROD/R03-92/146
Chem-Solv, DE
First Remedial Action - Final
Abstract (Continued)
aquifer. The primary contaminants of concern affecting the ground water are VOCs,
including benzene, PCE, TCE, toluene, and xylenes; and the metal manganese.
The selected remedial action for this site includes ground water pumping and offsite
discharge to a POTW, or as a contingency if an agreement with the POTW cannot be reached,
onsite treatment by filtration and air stripping and onsite discharge; ground water
monitoring; institutional controls, including ground water use and deed restrictions; and
the removal of existing recovery wells. If ground water monitoring detects contamination
in existing residential wells, alternate water supplies will be provided. The present
worth cost for the selected remedy is 5660,000 to $686,000, including an annual O&M of
$57,000 to $138,000; and for the contingency remedy is $688,000, including an annual OiM
of $148,000 to $189,000.
PERFORMANCE STANDARDS OR GOALS: Chemical-specific ground water clean-up goals are based
on SDWA MCLs for VOCs, including benzene 5 ug/1, PCE 5 ug/1, TCE 5 ug/1, toluene
1,000 ug/1, and xylenes 10,000 ug/1; and risk-based levels for manganese 3,000 ug/1.
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REGION III, EPA
PHILADELPHIA, PA
RECORD OF DECISION
FOR THE CKEK-80LV, INC. SITE
CEBSWOLD, KENT COUNTY, DELAWARE
March 1992
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RECORD OF DECISION
CHBM-80LV, ZHC.
DECLARATION
SITE IAMB AND LOCATION
Chem-Solv, Inc.
Chesvold, Kent County, Delaware
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for
the Chem-Solv, Inc. Site, in Chesvold, Kent County, Delaware, which
was chosen in accordance with the requirements of the Comprehensive
Environmental Response, Compensation, and Liability Act of 1980
(CERCLA), as amended, 42 U.S.C. S 9601 e£ sea.. and, to the extent
practicable, the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP), 40 C.F.R. Part 300. This decision document
explains the factual and legal basis for selecting the remedy for
this Site. The information supporting this remedial action
decision is contained in the Administrative Record file for this
Site.
The State of Delaware concurs with the selected remedy.
ASSESSMENT OF TEE SITE
Pursuant to duly delegated authority, I hereby determine, pursuant
to Section 106 of CERCLA, 42 U.S.C. S 9606, that actual or
threatened releases of hazardous substances from this Site, if not
addressed by implementing the response action selected in this
Record of Decision (ROD), may present an imminent and substantial
endangerment to public health, welfare, or the environment.
DESCRIPTION OF THE SELECTED REMEDY
This remedy addresses ground water contamination in the uppermost
aquifer beneath the Site, the only medium which the United states
Environmental Protection Agency (EPA) has determined needs to be
addressed. The ground water, which is contaminated with volatile
organic contaminants (VOCs) and manganese, will be collected from
the aquifer through a series of recovery wells and treated to
remove the contaminants until the cleanup levels are achieved. The
ground water cleanup levels for this Site are the Maximum
Contaminant Levels (MCLs) and non-zero Maximum Contaminant Level
Goals (MCLGs) of the Safe Drinking Water Act for those contaminants
for which they exist. Health-based cleanup levels were developed
for contaminants wic no associated MCLs or MCLGs.
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The selected remedy includes the following major components:
1. Collection of contaminated ground water using recovery
wells until cleanup levels are achieved
2. Discharge of extracted ground water to the local Publicly
Owned Treatment Works (POTW) via the Kent County sewer
system or, if an agreement with the POTW cannot be
'reached, a contingency remedy for onsite treatment of
extracted ground water and discharge to local surface
water
3. Continued ground water monitoring of domestic, recovery
and monitoring wells until cleanup levels are achieved
4. Provisions for an alternate water supply for residences
whose wells may become contaminated before the remedial
action is complete
5. Institutional controls restricting ground water use until
cleanup levels are achieved throughout the entire
contaminated area by establishing and enforcing a State
ground water restriction zone and property deed
restrictions regarding the installation of wells in the
restriction zone
6. Removal of existing recovery wells onsite.
DECLARATION OF STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the
environment, complies with Federal and State requirements that are
legally applicable or relevant and appropriate to the remedial
action, and is cost-effective. This remedy utilizes permanent
solutions and alternative treatment (or resource recovery)
technologies to the maximum extent practicable, and it satisfies
the statutory preference for remedies that employ treatment that
reduces toxicity, mobility, or volume as a principal element.
Although EPA believes that the selected remedy will achieve the
cleanup levels, it may become apparent during implementation or
operation of the ground water treatment system that contaminant
levels are remaining constant at levels higher than the cleanup
levels. In that event, a reevaluation of the system performance
standards and/or the remedy may be necessary. Assuming that the
cleanup levels set forth in this ROD will be met, no hazardous
substances will remain at the Site above levels that would allow
unlimited use and unrestricted exposure after completion of the
selected remedy. The cleanup levels, however, may require five or
more years to attain. Hazardous substances, therefore, may remain
at the Site above levels that allow for unlimited use and
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unrestricted exposure for five years or longer from initiation of
the remedial action. Because the selected remedy say not allov for
unlimited use and unrestricted exposure within five years of
initiation of the remedial action, a policy review of the Site will
be conducted within five years of the initiation of the remedial
action in accordance with EPA guidance set forth in "Structure and
Components of Five-Year Reviews," May 23, 1991, OSWER Directive
9355.7-02, to ensure that the remedy continues to provide adequate
protection to human health and the environment. Such policy-
reviews will be conducted every five years thereafter until EPA.
determines that the cleanup levels set forth in this ROD have been
achieved, or that the hazardous substances remaining on the Site do
not prevent unlimited use and unrestricted exposure at the Site.
Edwin B. EricJcson V Date
Regional Administrator
Region III
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STATE or DKLAWAM
DEPARTMENT O* NATURAL RESOUP
A ENViRONMCNTAi CONTROL
DIVISION OF AIM ft WASTE MANAGEMENT
ee NUMB HMHWAV
BflVW. DCWkWANI I
OMflCTON
March 31, 1992
Kr. Edwin B. Brickaon
Regional Administrator
U.S. EPA Region III
841 Chestnut Building
Pbil«d*lphl«, PA 19107
RZ: Conourr«ne« With Ih« Record Of D«ci«ion For Th« Chni
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DBCISIOH SUMMARY
1.0 SITE HAMB, LOCATION AND DESCRIPTION
The Chem-Solv, Inc. (Chem-Solv) site is located in Chesvold, Kent
County, Delaware, approximately 3 miles north of Dover on the
west side of U.S. Route 13 (Dupont Highway) just south of
Delaware Route 42 (Figure 1). The Chem-Solv facility occupied
the southern third of a 1.5 acre property and consisted of a one-
story concrete block building, a distillation process building,
and a concrete pad. A concrete-paved skateboard park was
formerly located adjacent to the office building, but was
partially dismantled in 1988. A two-story wood frame apartment
building, a storage barn, and a wood shed occupy the northern two
thirds of the property (Figure 2).
The total population of Cheswold, Delaware is approximately 300.
Surrounding land use is agricultural, residential, and commercial
(Figure 3). Strip development consisting of commercial
establishments and private residences is found on both sides of
Route 13 in the vicinity of the site.
To the south and west of the site is an abandoned field that was
part of a former drive-in theatre. A truck
stop/restaurant/fueling establishment previously operated
immediately north of the property, adjacent to Route 13. Three
underground storage tanks (USTs) were removed from this property
in May 1988. The tanks reportedly contained diesel fuel,
gasoline and fuel oil. An antique furniture/refinishing store is
located north of the former truck stop on the southwest corner of
the intersection of Routes 13 and 42.
On the north side of Route 42 west of Route 13 is a gasoline
station/convenience store where leaking USTs were replaced in May
1990. In the past, gasoline stations operated on both the
northeastern and southeastern corners of the intersection of
Routes 13 and 42 as well, each of which had USTs located on the
premises. Three USTs on the property on the southeast corner
were cracked when removed in April 1987.
Private homes are located along Route 42 proceeding east from
Route 13. A roofing business, a private home, and a used truck
business are all located across Route 13 from Chem-Solv.
Qeolocrv - The Chem-Solv site is located within the Coastal Plain
Physiographic Province, which is characterized as a series of
unconsolidated or partially consolidated layers of sand, gravel,
silt, and clay. These sediments form a wedge that dips and
thickens to the southeast. The thickness of the Coastal Plain
sediments is approximately 3,300 feet in the vicinity of the
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site. This section of sediments consists of the Miocene Calvert
Formation of the Chesapeake Group overlaid by the .surficial
Pleistocene Columbia Formation (Figure 9). The thickness of the
Columbia Formation in the vicinity of the site is approximately
50 feet. The formation is locally characterized by
unconsolidated, moderately to poorly sorted, coarse-to-fine,
brown-to-orange quartz sand. Thin clay, silt, and gravel
interbeds are common within the formation. The Chesapeake Group
which immediately underlies the Columbia Formation is
characterized by gray to bluish-gray silts with some sand that
are commonly fossiliferous. The Cheswold aquifer is found within
the Chesapeake Group in the vicinity of the site.
Soils - Soil at the site is classified as Sassafras sandy loam
by the United States Department of Agriculture Soil Conservation
Service. The Sassafras consists of deep, well-drained, friable,
moderately coarse textured sandy soils with 0 to 5 percent
slopes. The hazard of erosion is slight because of the small
slopes. The pH of these soils is in the range of 4 to 5.5. The
soils retain moisture moderately well and are good for farm and
nonfarm use.
stratigraphy - The uppermost geologic unit beneath the site, the
Columbia Formation, ranges in thickness from 20 to greater than
40 feet in the vicinity of the site. Hells and borings at the
site shown in Figure 4 have encountered a low permeability silt
layer approximately .1 to 6 feet thick at approximately 18 to 23
feet below grade. This layer separates the shallow and
intermediate zones of the Columbia aquifer. It is present
beneath the Chem-Solv property and extends beyond the property
boundary to the eastern side of Route 13 in the vicinity of wells
8A and 8B. A second silt layer was encountered at shallower
depths, approximately 14 feet below grade, at borings CSB-3 and
CSB-5 and well MWS-6-25. This layer is not laterally contiguous
with the silt layer encountered beneath the former Chem-Solv
facility. Figure 5 shows the geologic cross section of the site.
HvdroQeoloav - In the vicinity of the site, the Columbia
Formation functions as a thin water-table aquifer. The average
depth to ground water at the site is approximately 8 feet.
Because of its limited saturated thickness, only domestic supply
needs can be. met from this aquifer. However, the Columbia
Formation is a source of recharge for the deeper artesian
aquifers between the Columbia and the underlying Cheswold aquifer
of the Chesapeake Group. In the vicinity of the site, the top of
the Cheswold aquifer is present approximately 100 feet below
grade.
Ground water flow directions for both shallow and intermediate
zones of the Columbia aquifer are generally to the northeast. In
the shallow zone, the average hydraulic conductivity has been
calculated to be 31 ft/day. Ground water gradients and flow
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velocities in the Columbia Formation are non-uniform as a result
of the r ssterogeneous nature of the sediments. In .1990 and 1991,
flow vc scities for the shallow zone were estimated.to be as high
as 2.9 f,-
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2.0
2.1 Hiatorv aad Previous Investigations — The Chem-Solv
facility was in operation from approximately 1981 to 1984. At
the facility, spent industrial solvents were distilled and
purified. The recovered product was then returned to the
original generator for reuse. The residues generated during the
distillation process, referred to as "still bottoms'*, were
collected in 55 gallon drums. These drums were stored on the
concrete pad behind the distillation building, awaiting offsite
disposal as hazardous waste. Chem-Solv was, therefore,
classified as a hazardous waste storage facility and had obtained
Resource Conservation and Recovery Act (RCRA) interim status.
On September 7, 1984, an explosion and fire occurred at the
facility which resulted in solvents running off the concrete pad
and into the soil. The Delaware Department of Natural Resources
and Environmental Control (DNREC) was notified and immediately
initiated an investigation to determine the nature and extent of
potential soil and ground water contamination. At the time of
the incident, DNREC conducted air monitoring and collected soil
samples. Based on soil sampling analysis, DNREC concluded that
the soil contamination consisted primarily of the following
volatile organic compounds (VOCs): trichloroethene (TCE);
1,1,1-trichloroethane (TCA); 1,2-dichloroethane (1,2-DCA);
1-chloroethane; ethylbenzene and toluene.
As a result of a detailed analysis of the waste and material
handling practices at Chem-Solv, DNREC concluded that the
facility had other violations of Delaware's regulations governing
hazardous waste. Consequently, DNREC issued a Cessation of
Operation Order (Order) to Chem-Solv dated September 21, 1984.
The Order outlined DNREC's belief that spillage of hazardous
wastes onto the ground had occurred during the fire on September
7, 1984, and at other times previous to that incident. DNREC
ordered Chem-Solv to halt all hazardous waste handling operations
with the exception of those associated with cleanup of the site.
In addition, the Order required Chem-Solv to remove contaminated
soil from the site and to initiate a ground water monitoring
program. DNREC initiated a soil and ground water investigation
after the owners of Chem-Solv failed to comply with the Order.
In August 1985, DNREC terminated Chem-Solv, Inc.'s interim status
under RCRA and denied Chem-Solv, Inc.'s request for a RCRA Part B
permit to store hazardous waste.
In 1985 DNREC removed a large portion of the drum storage pad and
excavated 1300 cubic yards of contaminated soil to the depth of
the water table. Figure 2 shows the approximate area of
excavation. The soil was staged onsite for later remediation.
Subsequently, DNREC contracted with SMC Martin, Inc. (SMC
Martin), an environmental consultant, to evaluate remedial
alternatives for onsite treatment of the excavated soil.
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SMC Martin conducted two initial rounds of soil sampling in May
1985. The sampling scheme was designed to determine the
following:
1. Whether any contaminated soil remained in the sidewalls
or floor of the excavation;
2. The range of concentration of contaminants in the soil
' stockpile for the evaluation of feasible remedial
alternatives; and
3. Whether any compounds other than VOC's had contaminated
the soils.
SMC Martin collected soil samples from the stockpiled soils, and
from the floor and sidewalls of the pit, and analyzed them for
selected VOCs. Total VOC concentrations ranged from 0 ug/kg
(micrograms per kilogram) to 120 ug/kg in the sidewalls, 132
ug/kg to 3640 ug/kg in the floor, and 26 ug/kg to 244 ug/kg in
the stockpiled soils. VOC contamination consisted of TCE and
TCA.
Based on results from the May 1985 sampling, SMC Martin concluded
that soil shredding/aeration was the appropriate alternative for
remediation of the soil and issued a report entitled Evaluation
of Remedial Alternatives for Soil and GrQU,n.flwater Cleanup at the
Chem-Solv Solvent Recovery Facility. Cheswold. Delaware, dated
May 18, 1985.
In August 1985, a second round of soil samples was collected from
the in-place soils adjacent to the stockpiled soils and analyzed
for VOCs and acid/base neutral organic compounds. No acid/base
neutral compounds were detected. VOC concentrations ranged from
1.9 to 31 ug/kg. Samples were also collected from the stockpiled
soils and analyzed for VOCs. Total VOC concentrations ranged
from 1.1 to 480 ug/kg. These results indicated that the
stockpiled soil contained significant levels of VOCs and that the
excavation had not extended to an adequate depth, although soil
was removed to the water table. Some minor VOC contamination
existed in the in-place soil.
The soil shredding process began on September 9, 1985 and
continued until November 7, 1985. The stockpiled soils were
repeatedly passed through the soil shredder equipment. Samples
of the soil were taken before and after shredding and were
analyzed for VOC concentration, moisture content, grain size, and
pH. When analytical results indicated that additional passes of
the soil through the shredder did not result in any additional
reduction in VOCs, the soil was placed into the excavated pit and
compacted. Otherwise, the soil was returned to the shredder for
another pass.
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SMC Martin published the findings of the soil shredding operation
in a report entitled Removal of Volatile Organic Contaminants
from Soils at the Chem-Solv Solvent Recovery Facility. Chesvold.
Delaware, dated May 20, 1986.
DNREC also conducted an extensive investigation into ground water
contamination associated with the Chem-Solv facility. Between
September 1984 and June 1986, DNREC installed 43 monitoring wells
and 7 recovery wells on and around the site. Monitoring wells
were installed in the shallow and intermediate zones of the
Columbia Formation, that is, above and below the low permeability
silt layer which is found beneath the former Chem-Solv facility
and extends across Route 13. Samples of ground water from these
and domestic wells in the vicinity of Chem-Solv were collected
and analyzed for organic priority pollutants, primarily vocs,
beginning in October 1984.
Early analytical data collected by DNREC indicated that ground
water contamination in the shallow aquifer consisted of VOCs,
primarily TCE and associated chlorinated hydrocarbons. Maximum
detected concentrations ranged from 2.8 ug/1 (micrograms per
liter) chlorobenzene to 130,000 ug/1 TCE. Other VOCs detected
and their maximum concentrations were as follows: benzene
(360 ug/1), chloroform (669 ug/1), 1,1-dichloroethane (1,1-DCA)
(414 ug/1), 1,1-dichloroethylene (3,200 ug/1), 1,2-dichloroethane
(1,2-DCA)(30 ug/1), trans-1,2-dichloroethylene (1,000 ug/1),
ethylbenzene (1,100 ug/1), toluene (2,300 ug/1), TCA
(1,800 ug/1), m-xylene (250 ug/1), o-xylene (106 ug/1), and
p-xylene (111 ug/1). The inorganic element manganese was also
found at elevated levels.
Continued monitoring of ground water quality indicated that by
October 1985 the contaminant plume had migrated beyond the
property boundary to the eastern side of Route 13. Total VOC
levels in the median of Route 13 were as high as 418 ug/1 and TCE
was detected on the east side of Route 13 at a level of
approximately 200 ug/1.
Contaminant concentrations in the intermediate zone monitoring
wells never reached the high levels found in the shallow zone.
The maximum detected VOC levels in the intermediate zone
monitoring wells were 1.3 ug/1 chloroform, 1.2 ug/1 1,1-DCA,
38 ug/1 1,2-dichloropropane, 2.3 ug/1 toluene, 2.1 ug/1 TCA, and
3.4 ug/1 TCE.
Information gathered during this early investigation allowed
DNREC to assess the general hydogeologic conditions underlying
the site and to delineate the plume of VOC-contaminated ground
water. In April 1985, DNREC retained SMC Martin to evaluate
alternatives for ground water remediation at the site. Because
of SMC Martin's findings, DNREC decided to implement a ground
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water treatment system that included a collection system and
treatment of the collected ground water by air stripping.
The ground water collection system became operational in December
1985. Seven recovery wells were installed onsite and were
designed to contain the major portion of the plume within a 150-
foot radius from the center of the system. Analytical results
were obtained for both the untreated and treated ground water.
In January 1986, total VOC levels were 37,946 ug/1 in the
untreated ground water and 3.5 ug/1 in the treated water. Total
VOC concentrations in the untreated ground water gradually
decreased to a low of 1.7 ug/1 in April 1988 and then increased
to levels ranging from 49.4 ug/1 in May 1988 to 173.2 ug/1 in
July 1988. Total VOC levels in the treated water ranged from not
detected to 10.5 ug/1.
In September 1988, the air stripping tower collapsed. Collected
ground water was no longer discharged to the air stripper but
DNREC continued to discharge to the Kent County sewer system
until November 1988 when the ground water collection system was
shut down permanently. DNREC continues to conduct quarterly
monitoring of several domestic wells in the area. In 1987, DNREC
replaced one domestic well, the Gearhart well indicated on Figure
4 on the east side of Route 13, after VOCs were detected in the
well. The replacement well was drilled into a deeper
uncontaminated aquifer.
2.2 Enforcement Activities - EPA initially proposed the Chem-
Solv site for inclusion on the National Priorities List (NPL) on
January 22, 1987. Subsequently, procedural issues arose and new
technical information became available, resulting in EPA
reproposing the site on June 24, 1988. EPA placed the site on
the NPL on August 30, 1990.
In December 1987, EPA issued Special Notice Letters to
approximately 30 potentially responsible .parties (PRPs) inviting
them to perform the Remedial Investigation/Feasibility Study
(RI/FS) for the Chem-Solv site. In September 1988, DNREC, EPA
and 21 of the PRPs entered into an Administrative Order on
Consent (AOC). Under the AOC, the PRPs agreed to perform the
RI/FS, with DNREC and EPA oversight, in accordance with CERCLA.
3.0 H1QHLIQHT8 GT COMMUNITY PARTICIPATION
Pursuant to CERCLA S 113(k)(2)(B)(i)-(v), the RI/FS reports and
the Proposed Plan for the Chem-Solv site were released to the
public for comment on January 15, 1992. These two documents were
made available to the public in the Administrative Record file
located at the EPA Docket Room in Region Ill's Philadelphia
office, the DNREC office in New Castle, DE, and at the William C.
Jason Library at Delaware State College in Dover, DE. The notice
of availability of these documents was published in TJje.
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Wilmington Neva Journal and The Delaware State News on January
15, 1992. A public comment period on the documents was held from
January 15, 1992 to February 14, 1992. In addition, a public
meeting was held on February 6, 1992. At this meeting,
representatives from EPA and DNREC answered questions about
conditions at the site and the remedial alternatives under
consideration. A response to the comments received during the
public comment period, including those expressed verbally at the
public meeting, is included in the Responsiveness Summary, which
is part of this Record of Decision (ROD). This ROD presents the
selected remedial action for the Chem-Solv, Inc. site in
Cheswold, Delaware, chosen in accordance with CERCLA and, to the
extent practicable, the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP), 40 C.F.R. Part 300. The
decision for this site is based on the Administrative Record file
placed in the above-mentioned locations.
4.0 SCOPE AND ROLE OF REMEDIAL ACTION
This ROD addresses ground water contamination in the Columbia
aquifer, the only media requiring remedial action at this site.
The remedial action objectives are to prevent exposure to the
contaminated ground water at the site and to restore the ground
water to its beneficial use. In the vicinity of this site, the
Columbia aquifer is a potential drinking water source.
5.0 SUMMARY OF 8TTB CHARACTERISTICS
In accordance with the AOC signed in 1988, the PRPs performed a
RI/FS to assess the nature and extent of contamination of the
local ground water and the soil in and around the former
excavated area by site-related contaminants. The PRPs also
performed a risk assessment to evaluate the risk to human health
and the environment from exposure to site contaminants.
The RI included soil, ground water, and stratigraphic
investigations. Ten soil borings were drilled within the
boundary and around the edge of the former excavated area and 32
soil samples were collected to evaluate whether contamination
remained in these areas. Soil samples were analyzed for all
Target Compound List (TCL) and Target Analyte List (TAL)
parameters. Five stratigraphic borings were also drilled
downgradient to determine the extent of the silt layer which had
been identified directly beneath the facility. Seven additional
monitoring wells were installed. Ground water samples were
collected from these wells and from seven existing wells and
analyzed for all TCL/TAL parameters. Analytical data from the
ground water sampling were evaluated to determine the horizontal
and vertical extent of ground water contamination in both the
shallow and intermediate zones of the Columbia aquifer.
8
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5.1 aeil« - Low concentrations of organic compounds were
detected in onsite soils, generally at levels below or close to
the method quant itat ion limit (Figure 7) . These compounds
included VOCs (TCE, chloroform, methylene chloride, toluene, and
xylene) , semi volatile organics (benzoic acid, bis [2-ethyhexyl]
phthalate, butylbenzylphthalate, and isophorone) , and pesticides
(DDD, DOE, and DDT) . Twenty inorganic elements were detected in
onsite soils at background levels. Generally soils from within
the former excavated area had lower concentrations of both
organic and inorganic compounds than soils located outside the
former excavated area.
Results from soil samples collected within the boundary of the
former excavated area confirm that the DNREC soil remediation
program successfully removed VOCs from the soils. Toluene and
xylene were detected below method guantitation limits in only one
sample at estimated concentrations of 2 ug/kg and 3 ug/kg,
respectively. In addition, analytical results from sampling
locations around the former excavated area show maximum levels of
chloroform (15 ug/kg), methylene chloride (4 ug/kg), and TCE (5
ug/kg) at levels near the analytical detection limit and indicate
that the soil remediation program encompassed the entire source
area.
Some semivolatile organics were detected both within and outside
the former excavated area at low concentrations. Comparison of
data obtained from site background soils indicates that the
pesticides detected in onsite soils are anthropogenic. These
compounds probably resulted from previous pesticide use at the
adjacent open field. In addition, background data indicate that
the 20 inorganics detected in onsite soils are generally within
background concentrations (Table 1) . A slightly elevated lead
level in one onsite soil sample is likely attributable to the
fact that the site is directly adjacent to Route 13.
5.2 flrffypfl Ifottr ~ Figure 8 summarizes the relevant ground water
data collected during the RI. Wells 9A, 22A, 33A, 39A, 41A, MWS-
3-17, MWS-5-18, MWS-6-25, and MWS-7-25, drilled to depths of 25
feet or less, are located in the shallow zone of the Columbia
aquifer. Wells 9B, SB, MWI-1-43, MWI-4-40, and HWI-2-40 are
drilled in the intermediate zone to depths of approximately 40
feet. Ground water flows to the northeast in both the shallow
and intermediate zones. Wells 22A and MWI-1-43 are located
upgradient of Chem-Solv and represent background conditions.
Wells 9A, 9B, SB, and 33A are located within the property
boundary. The remainder of the wells are located downgradient of
the property boundary in the direction of ground water flow.
5.2.1 shallow aon« investigation - Eleven VOCs (acetone,
benzene, 1,1-dichloroethane, cis-l,2-dichloroethene, 1,2-DCA,
methylene chloride, tetrachloroethene (PCE) , toluene, TCA, TCE,
and total xylenes) were found during the ground water
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investigation. Total VOC concentrations ranged from 5 ug/1 in
veil MWS-5-18 to 563 ug/1 in well 33A to 921 ug/1 in well
MWS-7-25. Twelve VOC tentatively identified compounds (TICs)
were found in well 26A and well MWS-7-25. Phenol was found in
one well at 9 ug/1. Eleven semi volatile TICs were detected in
three downgradient wells. No pesticides were found in any
sample.
Wells 33A and 26A showed the highest concentrations of site-
related contamination. TCE concentrations were highest in well
33A at 540 ug/1. Well 26A, located on the adjacent property just
north of Chem-Solv, was found to be contaminated with benzene,
toluene, and several VOC TICs. It is uncertain whether the
contamination in well 26A may be partially attributed to USTs or
the operation of a filling station on this property in the past;
however, well 26A is situated downgradient from the initial
source at Chem-Solv and certain compounds found in this well
(benzene, toluene, TCE, and 1,1-DCA) during and previous to the
RI have also been determined to be associated with Chem-Solv.
The contamination in well 26A will be addressed, therefore, by
the selected remedy for the Chem-Solv site.
Sources other than Chem-Solv are believed to be the cause of
contamination found just north of the intersection of Routes 13
and 42. VOC contamination found in MWS-7-25 has been interpreted
to be representative of compounds found in the subsurface after
gasoline or other petroleum hydrocarbons are spilled. DNREC UST
files document that USTs were located at several former gasoline
stations located at this intersection and just west of Route 13
on Route 42, as discussed in Section 1.0. Some of these tanks
were known to have leaked in the past or were reported to be
cracked when removed from the ground. The contamination
associated with these suspected sources north of Route 42 is not
within the boundary of the contaminant plume associated with the
Chem-Solv site and therefore will not be addressed as part of the
remedy for the site.
Inorganics detected at elevated levels in shallow ground water
samples include manganese and zinc. Elevated zinc levels were
found only in well 33A and are believed to be caused by the
galvanized steel casings of the recovery wells located in the
vicinity of wall 33A. These recovery wells will be removed
during the performance of the selected remedial action at the
site as set forth in Section 9.0 of this document.
The highest concentrations of manganese, approximately 23,000
ug/1, were detected in well 26A. Elevated levels were also found
in wells further downgradient, but at comparatively lower levels
(1800 ug/1 at well 41A; 1300 ug/1 at well 39A). Manganese
concentrations in wells that were sampled and located within the
Chem-Solv property boundary were only as high as 148 ug/1.
Inorganic compounds, such as manganese, become more soluble in
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water under anaerobic conditions. Low pH and dissolved oxygen
concentrations for well 26A indicate that these conditions exist
in this location. The anaerobic conditions are believed to be
influenced by the natural degradation of the hydrocarbon
contaminants found in this well. The dissolved manganese
consequently moves with ground water to the northeast resulting
in elevated levels of manganese in wells 39A and 41A.
5.2.2 Intermediate gone Investigation - Ground water data
collected from wells in the intermediate zone of the aquifer
indicate that impact to this zone has been limited by the
presence of the low permeability silt layer beneath the site.
However, some VOC contamination has occurred as indicated by low
levels of VOCs in the intermediate zone monitoring wells and
nearby domestic wells (Figure 8).
Low concentrations of volatile and semivolatile organic compounds
were found in the two wells located within the property boundary
and the upgradient well. TCE was detected in well 58 at an
estimated concentration of 5 ug/1 and was not detected in well 9B
at the quantitation limit. Total semivolatile organic TICs were
10 ug/1 in the upgradient well (MWI-l-43), 103 ug/1 in well SB,
and 60 ug/1 in well 9B. No volatile organic TICs, semivolatile
organic compounds, or pesticides were detected in any ground
water sample. Elevated levels of mercury were found in well 9B;
however, further investigation revealed that the majority of the
mercury exists in the less toxic inorganic form and is not of
concern at the concentrations detected.
5.2.3 Pomestie Wells - DNREC has monitored several domestic
wells in the area periodically since 1984. Some of these wells
are screened in the water table aquifer, some are much deeper,
and many are of unknown depths. As mentioned in Section 2, one
well, the Gearhart well located on the east side of Route 13 (see
Figure 4) was replaced in 1987 after becoming contaminated with
VOCs. Samples collected in March 1991 from the American Roofing,
new Gearhart, and Simon wells, the three wells located closest to
the Chem-Solv property, indicated little impact from the site
(Figure 8). The American Roofing well shoved 1,2-DCA at 5 ug/1.
No other VOCs were detected in the three wells. Manganese and
zinc were not found at elevated levels. Mercury was not
detected.
In summary, soil sampling results indicate that the soil
shredding operation conducted by DNREC in 1985 was sufficient to
remediate the contamination in the source area. Very little
contamination of soil remains and is at such low levels that no
further action is warranted. No potential or current threat to
human health or the environment is presented by the onsite soils.
Ground water, however, remains contaminated with several VOCs,
primarily TCE and benzene, and the inorganic contaminant
11
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manganese. The ground water contamination exists beneath the
Chem-Solv property and extends laterally some distance to the
northeast in the direction of ground water flow to approximately
well 41A located on the east side of Route 13. The highest
concentrations of contaminants in the ground water have been
found in one monitoring well on the Chem-Solv property and in one
well on the adjacent property directly to the north. Vertically,
the contamination has been detected in the uppermost water table
aquifer beneath the site, the Columbia Formation, with the
majority present within the upper 20 feet, the shallow zone.
Very low concentrations of contaminants have been found at depths
of approximately 40-50 feet in monitoring wells and in some
domestic wells in the area. Based on the low concentrations of
contaminants that were detected relative to their solubilities in
water, EPA has determined that it is extremely unlikely that
dense nonagueous phase liquids (DNAPLs) exist beneath the site.
6.0 SUMMARY OF SITE RISKS
A Risk Assessment was prepared by the PRPs to assess the
potential human health and environmental effects that may result
from exposure to contaminants from the site. The Risk Assessment
can be found in Section 5 of the Remedial Investigation Report.
BCM Engineers, Inc., November 1991. EPA subsequently modified
the human health risk assessment. All documentation is included
in the Administrative Record file for the site. The revisions
are included in the risk discussion presented in this section.
Based on the Risk Assessment , as modified by EPA, it has been
determined that actual or threatened releases of hazardous
substances from this site, if not addressed by implementing the
response action selected in this ROD, may present an imminent and
substantial endangerment to public health and welfare.
6.1 HMHI»K Health Assessment
mitiapt Identification Information — No organic or
inorganic compounds were determined to be of concern in soil
because the concentrations detected were in the range of
background concentrations which are not above acceptable health-
based levels, represented isolated events unrelated to previous
site activities, or were infrequently detected at low
concentrations. EPA consequently concluded that onsite soils do
not pose a human health or environmental threat. The remainder
of the risk assessment was not performed for soils because no
contaminants of concern were identified.
Contaminated ground water was the only medium found to pose a
threat to human health or the environment at the Chem-Solv site.
The contaminants of concern for ground water listed in Table 2
include several VOCs detected during the RI and one inorganic
contaminant, manganese, also detected during the RI. The
reasonable mavinnna exposure (RME) values for the contaminants of
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concern are also listed in Table 2. The RME represents the 95
percent upperbound confidence interval for the arithmetic mean.
It is a statistical estimate of the highest average concentration
predicted to occur in 95 out of 100 sets of samples. The RME is
used to account for the fact that the actual number of samples is
relatively small to accurately predict the average.
6.1.2 Exposure Assessment - The exposure assessment determines
the pathways that may result in human exposure, the mass of
chemicals at the point of exposure, and the concentration of each
chemical absorbed by the exposed individual on a daily basis
(chronic daily intake, GDI). Exposure pathways include all the
various ways in which humans come in contact with the
contaminants of concern, either currently or at some time in the
future.
The only complete exposure pathway identified at the Chem-Solv
site is residential use of the ground water. Currently, one
drinking water well is located within the property boundary and
several are located downgradient. Potential routes of exposure
include ingestion of ground water, inhalation of indoor air
containing VOCs, and dermal absorption during showering or
bathing.
The potential for contamination of homegrown fruits and
vegetables during watering and the release of contaminants to
surface water were also considered. Since the contaminants of
concern are primarily VOCs which will volatilize during watering,
they have little to no potential for accumulation in homegrown
food.
The distance to the nearest point of surface water discharge is
0.4 miles, and low concentrations of VOCs indicate that the
potential for elevated concentrations in this stream, the Alston
Branch of the Leipsic River, is highly unlikely. Nevertheless,
an exposure pathway quantified for dermal absorption during
showering or bathing can be used to semi-quantitatively evaluate
exposure in the stream.
Exposure during recreational use of the stream will be primarily
dermal, with occasional wetting of the hands, feet, and lower
legs of children. The use of .the exposure pathway for dermal
absorption during showering and bathing assumes daily contact
with ground water over the entire body. If this pathway poses no
significant risk, sporadic dermal exposure to water in the stream
will pose even less risk. In fact, as explained below, the
dermal absorption route alone does not pose an unacceptable risk.
Therefore, no adverse health effects would be expected from use
of the stream.
The objective of the exposure assessment is to determine how much
of the chemical is actually taken into the body (dose or GDI).
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The dose received daily is expressed as the milligrams of
contaminant per kilogram of body weight per day (mg/kg/day). A
number of assumptions are used to calculate the dose for each
identified exposure pathway since it is seldom possible to
measure a specific dose. The assumptions used for this risk
assessment are presented in Table 3. Separate calculations were
performed for adults and children because children are considered
a more sensitive subpopulation.
The data .for the ground water monitoring wells were evaluated to
determine which wells were most representative of the ground
water quality at the site. The data from these wells were then
combined to estimate concentrations in a hypothetical drinking
water well placed in the contaminated area. Data from the
intermediate and shallow zone wells 5B, 26A, 33A, and 39A were
combined to simulate ground water use in the area. Area drinking
water wells are generally installed at depths greater than 100
feet; however, the high porosity of the soil and the absence of a
true confining layer in all areas suggests that water from the
shallow zone is likely to be included in the recharge for the
intermediate zone wells. In this way, human exposure to water
from the shallow aquifer may occur.
6.1.3 ToKicitv Assessment - Cancer potency factors (CPFs), also
known as slope factors, have been developed by EPA's Carcinogenic
Assessment Group for estimating excess lifetime cancer risks
associated with exposure to potentially carcinogenic chemicals.
CPFs for contaminants of concern which contribute to the
carcinogenic risk are presented in Table 4. CPFs, which are
expressed in units of (mg/kg/day)"1, are multiplied by the
estimated chronic daily intake (GDI) of a potential carcinogen,
in mg/kg/day, to provide an upper-bound estimate of the excess
lifetime cancer risk associated with exposure at that intake
level. The term "upper bound*1 reflects the conservative estimate
of the risks calculated from the CPF. Use of this approach makes
underestimation of the actual cancer risk highly unlikely.
Cancer potency factors are derived from the results of human
epidemiological studies or chronic animal bioassays to which
animal-to-human extrapolation and uncertainty factors have been
applied.
The weight of evidence, also presented in Table 4, reflects the
degree of confidence in the data used to determine that the
chemical is a human carcinogen. EPA toxicologists recognize that
the risks associated with a known human carcinogen, based on
epidemiological studies, should be evaluated differently from
those of a chemical that causes tumor production in a limited
number of laboratory animals. Each carcinogen is assigned to a
group according to the quality and quantity of evidence for
carcinogenicity in humans and animals. The definitions for the
groups are presented in Table 5.
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The potential for adverse noncarcinogenic health effects is
estimated with a toxicity value known as a reference dose (RfD).
RfDs are associated with adverse health effects, which are also
referred to as toxicity end points. The RfDs and toxicity
endpoints for the contaminants of concern are listed in Table 6.
The model to determine RfDs from the dose-response assessment
assumes that there is a concentration for noncarcinogens below
which there is little potential for adverse health effects over a
lifetime of exposure. The RfD is designed to represent this
threshold level.
The RfD is calculated from the highest chronic exposure level
that did not cause adverse effects (the no-observed-adverse-
effect level, or NOAEL) in animals. The NOAEL is divided by a
factor to account for any uncertainty such as using data on
animals to predict effects on humans and an allowance for
sensitive individuals. Uncertainty factors range from l to
10,000, based on the confidence level associated with the data.
The resulting RfD (ing/kg body weight/day) is used to quantify the"
risk.
6.1.4 Risk Characterisation - The risk characterization
combines the dose with the toxicity value to estimate a numerical
value for the risk. There are several differences between the
approach used to describe risk for carcinogens (cancer risk) and
for noncarcinogens (hazard index, HI).
6.1.4.1 Carcinogenic Risks - Excess lifetime carcinogenic risk
is calculated by multiplying the dose (GDI) times the slope
factor. These risks are probabilities that are generally
expressed in scientific notation (e.g., 1 x 10"6). An excess
lifetime carcinogenic risk of 1 x 10~6 indicates that, as a
plausible upper bound, an individual has a one in one million
chance of developing cancer as a result of site-related exposure
to a carcinogen over a 70 year lifetime under the specific
exposure conditions at a site. Carcinogenic risk estimates for
the same chemical in different exposure pathways are added
together. Also, carcinogenic risks for different chemicals are
added together to determine the risk associated with the exposure
pathway for all the chemicals.
EPA has not established an intake level below which no adverse
carcinogenic effects would be expected to occur. Instead, in the
NCP, EPA has identified a range of acceptable carcinogenic risks
of 1 x 10~6 to 1 x 10"4 for Superfund sites. This means that
target risk levels are between an upper limit of l in 10,000
probability of excess cancer incidence to a lower limit of 1 in
1,000,000.
Table 7 presents carcinogenic risk values for each exposure
pathway and for each contaminant in each pathway. The total
15
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carcinogenic risk for the ingestion pathway is 5 x 10~S. The
majority of risk is attributed to TCE and benzene,. 2 x 10~s for
each. Total carcinogenic risk for the inhalation pathway is also
5 x 10"5 with TCE and benzene contributing the greatest risk at
3 x 10"5 and 2 x 10~5, respectively. Dermal absorption presents
a total carcinogenic risk of 8 x 10~6, an order of magnitude
lower than ingestion and inhalation. Total carcinogenic risk for
all pathways is 1.1 x 10~4 which exceeds the upper bound (1 x 10~
4) of EPA's target risk range.
6.1.4.2 Honcarcinoaenie Risks - Potential concern for
noncarcinogenic effects of a single contaminant in a single
medium is expressed as the hazard quotient (HQ) (or the ratio of
the estimated intake derived from the contaminant concentration
in a given medium to the contaminant's reference dose) . By
adding the HQs for all contaminants within a medium or across all
media to which a given population may reasonably be exposed, the
Hazard Index (HI) can be generated. The HI provides a useful
reference point for gauging the potential significance of
multiple contaminant exposures within a single medium or across
media. HI values less than 1.0 indicate that lifetime exposure
has limited potential for causing an adverse effect in sensitive
populations. HI values greater than 1.0 show that acceptable
exposure levels have been exceeded.
Table 8 presents the noncarcinogenic risks presented by each
exposure pathway and contaminant. Separate calculations are
performed for adults and children because children are considered
to be a more sensitive subpopulation. The HI values exceeded 1.0
for ingestion of ground water for both adults (4.0) and children
(11.0). With an HQ of 4.0, manganese is the contaminant driving
the risk for this pathway. The remainder of the contaminants
present HQs well below 1.0 and contribute insignificant risk.
For the inhalation and dermal absorption pathways the HQ values
do not exceed 1.0 for either adults or children, indicating that
the potential for adverse health effects from inhalation or
dermal absorption is not expected. The HQ for adults for the
inhalation pathway is 2 x 10"2 and the HQ for children is
5 x 10"2. For the dermal absorption pathway, the HQ for adults
is 5 x 10~3 and the HQ for children is 7 x 10~3. The total HI
for all three pathways for adults is 4.0 and for children is
11.0, both of which exceed the acceptable HI of 1.0.
€.2 ^nTJrTBBTPMl frisk Assessment - The -environmental risk
assessment performed for the Chem-Solv site found no unacceptable
risks to the environment. There are no contaminants in the soils
at significant concentrations above background. The contaminants
of concern in ground water were evaluated for potential impacts
on aquatic life at the point of discharge into the nearest
surface water, the Alston Branch of the Leipsic River (Figure 1) .
The evaluation compared the calculated concentrations at the
16
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point of release with water quality guidelines (Table 9). All
predicted concentrations based on the RME concentrations for each
contaminant are below chronic toxicity guidelines indicating that
there is little to no potential for impact on aquatic life at the
discharge point.
No critical habitats, endangered species or habitats of
endangered species have been identified in the area. The Chem-
Solv property is vegetated with perennial plants (e.g., clover/ .
cow vetch, fleabane, plantain, ironweed, and several perennial
grasses). In the area where soil excavation and remediation took
place, a depression exists where water accumulates after
precipitation. This area is vegetated with some of the same
plants but many of the predominant plants found on the rest of
the property cannot tolerate such wet conditions.
6.3 Remedial Action Objectives and Cleanup Levels
The human health risk assessment indicates that the carcinogenic
risk (l.l x 10"4) and the noncarcinogenic risks (Hazard Index of
4.0 for adults, 11.0 for children) associated with the site
exceed acceptable levels and therefore warrant remedial action to
clean up ground water at the site. Remedial action objectives
and ground water cleanup levels must therefore be established.
The remedial action objectives for the site are to restore the
ground water to its beneficial use as a potential drinking water
source and to prevent exposure to the contaminated ground water
until the restoration is complete. Cleanup levels for the
contaminants of concern are listed in Table 10. In accordance
with S 300.430(e)(2)(i) of the NCP, 40 C.F.R. S 300.430
(e)(2)(i), the non-zero Maximum Contaminant Level Goals (MCLGs)
and, where the MCLG is zero. Maximum Contaminant Levels (MCLs)
developed under the Safe Drinking Water Act are the appropriate
cleanup levels for the majority of the contaminants. For acetone
and manganese, risk-based cleanup levels were developed because
MCLs do not exist. The cleanup level for manganese is based on
the No Observed Adverse Effect Level (NOAEL) and consideration
that manganese might be consumed from sources other than water.
The cleanup level for acetone is a Drinking Water Equivalent
Level calculated using the Reference Dose (RfD).
7.0 DBBCRTPTIOH OJ ALTBRHATIVBB
From the results of the Remedial Investigation (RI) and the Risk
Assessment, it has been determined that only one medium of
concern exists at the site. This has been identified as the
ground water in the Columbia aquifer which has been contaminated
by VOCs and manganese.
The NCP requires that the alternative chosen to clean up a
hazardous waste site meet nine criteria. The alternative must
17
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protect human health and the environment, be cost effective, and
meet the requirements of environmental regulations. Permanent
solutions to contamination problems should be developed wherever
possible. The solutions should reduce the volume, toxicity, or
mobility of the contaminants. Emphasis is also placed on
treating the wastes at the site, whenever this is possible, and
on applying innovative technologies to clean up the contaminants.
The FS evaluated a .variety of technologies to see which were
appropriate for addressing the contamination at this site. The
technologies determined to be most appropriate were developed
into remedial alternatives. These alternatives are presented and
discussed below. All costs and implementation timeframes
provided for the alternatives below are estimates and should be
used for comparative purposes only.
COMMON ELEMENTS;
The alternatives considered for the site include several common
elements. First, all alternatives include a monitoring program
for evaluation of ground water quality. The FS assumed that
monitoring would include sampling of onsite and offsite
monitoring wells and residential wells immediately downgradient
of the Chem-Solv property, that the analyses would include VOCs
and metals, and that approximately eight wells would be sampled
for monitoring purposes. The monitoring costs associated with
each alternative are based on these assumptions. Final
determination of the specific number and location of wells, the
frequency of sampling, and the analytical parameters and methods
to be included in the monitoring program during implementation of
the selected remedy will be made by EPA during the remedial
design for the site.
Second, all alternatives include removal of seven existing
recovery wells located on the Chem-Solv property. These wells
are constructed of galvanized steel which is believed to be
contributing to levels of zinc above background in the immediate
vicinity of the ground water collection system installed by DNREC
in 1985. Since the collection system is no longer operable, the
recovery wells will be removed. Abandonment of these wells will
be performed in accordance with the Delaware Regulations
Governing the Construction of Water Wells, Title 7, Delaware
Code, Chapter 60, S 6010.
Third, Alternatives 2 through 5 include a ground water
restriction zone to be instituted and enforced by DNREC. This
institutional control would restrict future installation of
residential wells in the Columbia aquifer in the contaminated
area and an appropriate buffer zone until cleanup levels are
achieved. Alternatives 3 through 5 also include provisions for
an alternate water supply to existing users should ground water
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monitoring indicate that contaminants are present in a well at
concentrations exceeding cleanup levels.
Five alternatives were evaluated to deal with the risks posed by
current and/or future ground water contamination. Alternative l
is considered no action because no active remediation would be
conducted. Alternatives 2 and 3 are considered limited action
since they include institutional controls or, in the case of
Alternative 3, an alternate water supply. Alternatives 4 and 5
offer two approaches to active remediation of the contaminated
ground water.
Cost figures include capital costs, annual operation and
maintenance (O & M) and present worth costs for each alternative.
An interest rate of 10 percent before taxes and after inflation
was assumed for the present worth analysis. The following is a
brief summary of each of the alternatives evaluated for the site:
Alternative is Ho Action, around Water Monitoring
Capital Costs: $13,500
Annual O & M: $25,000 - $81,000
Present Worth: $385,000
The NCP requires that the "no action*1 alternative be evaluated at
every site to establish a baseline for comparison. Under this
alternative, no further action would be taken to remediate the
ground water contamination or to prevent exposure to the ground
water either from existing residential wells or from residential
wells which might be installed in the future. This would allow
the continued migration of contamination in the ground water,
resulting in additional exposure of individuals to contaminants
exceeding cleanup levels.
The monitoring program discussed above would be included to
monitor ground water quality while the contamination is reduced
to cleanup levels by natural attenuation. Natural attenuation is
a combination of processes, such as biodegradation, dilution, and
dispersion that occurs within the aquifer and is estimated to
take approximately 14 years. This estimate is based on
concentrations of TCB and benzene in ground water being reduced
to MCLs. The assumption has been made that if the VOCs are
removed, the conditions causing the manganese to become soluble
would be eliminated thus reducing the elevated manganese
concentrations.
The costs listed above are based on quarterly monitoring for the
first 2 years, semiannual monitoring for the next 5 years, and
annual monitoring thereafter. Annual monitoring would continue
for 3 years after reaching the cleanup levels. The range in O6M
costs reflects the range in the frequency of monitoring. In
accordance with EPA guidance set forth in "Structure and
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Components of Five-Year Reviews," May 23, 1991, OSWER Directive
9355.7-02, a policy review of the remedial action .would be
conducted not less than every 5 years from the initiation of such
remedial action to interpret the ground water data and to monitor
the progress of natural attenuation. After review of the
monitoring data, the scope of the monitoring program would be
adjusted if determined necessary by EPA. This alternative is
considered to be easily implamentable.
Alternative 2: Ground Water Monitoring, Ground Water Restriction
2one
Capital Cost: $18,500
Annual O & M: $25,000 - $81,000
Present Worth: $391,000
As with Alternative 1, this alternative includes no action to
remediate the ground water contamination or to prevent exposure
to contaminated ground water from existing residential wells.
Ground water contamination would continue to exceed cleanup
levels and would continue to migrate downgradient. A ground
water monitoring program would be implemented as discussed in
Alternative 1. Alternative 2 would provide increased protection
of human health compared with Alternative 1 because it would use
institutional controls to reduce the potential for exposure to
contaminated ground water for future users.
This alternative varies from Alternative 1 in that it provides a
certain level of protection by restricting ground water use for
future users by using institutional controls. In this case,
DNREC would institute a ground water restriction zone to restrict
future installation of residential wells in the contaminated area
until contamination has naturally attenuated to cleanup levels in
approximately 14 years. DNREC has administrative programs to
support these restrictions, including well permitting, licensing
of drillers, and water allocation permitting. All wells must be
permitted by DNREC before installation. Notifications would also
be placed on the deeds of all properties located in the
restriction zone indicating that the property is located within
the boundary of a ground water restriction zone. The exact
location and extent of the restriction zone would be determined
by EPA and DNREC during the remedial design for the site.
As with Alternative 1, policy reviews would be performed in
accordance with EPA guidance set forth in "Structure and
Components of Five-Year Reviews," May 23, 1991, OSWER Directive
9355.7-02 no less often than every five years from initiation of
the remedial action to interpret the ground water data and to
monitor the progress of natural attenuation. The implementation
of deed restrictions would depend on the cooperation of property
owners. This option is considered to be administratively
feasible for implementation in a fairly short time frame.
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Alternative 3i Ground water Monitoring/ around Water Restriction
Zone, Alternate water supply
capital Costs: $30,500 - $34,500
Annual O & M: $25,000 - $84,000
Present Worth: $410,000 - $431,000
In addition to ground water monitoring and the ground water
restriction zone discussed in Alternatives 1 and 2, Alternative 3
would provide an alternate water supply to residences where
ground water monitoring indicates that cleanup levels are
exceeded. The alternate water supply would consist of well head
treatment at the affected well or replacement of the affected
well with a deeper well drilled into an uncontaminated aquifer.
Both existing and future ground water uses would be protected
with Alternative 3, though no active remediation of the
contaminated ground water would be conducted. Cleanup levels in
the aquifer would be reached through natural attenuation. Ground
water contamination would continue to migrate and exceedances of
cleanup levels in the aquifer would go unaddressed.
The type of well head treatment system to be used would depend on
the contaminants found during monitoring. Zeolite filters
installed on supply lines would remove inorganic compounds,
including manganese, from the household supplies. Carbon
adsorption units would then be placed in series after the zeolite
filters to remove VOCs. Ultraviolet treatment would be used to
control bacterial growth in the carbon units. The objective of
the well head treatment systems would be to reduce the
concentration of contaminants to cleanup levels (Table 10). EPA
would approve the exact configuration of the well head treatment
system during the remedial design.
Any residuals from the treatment unit in the form of spent carbon
05- filtration media would-be handled and disposed of offsite in
accordance with the requirements of Delaware Regulations
Governing Hazardous Waste, Parts 262-264 (40 C.F.R. Parts 262-
264) and the land disposal restrictions in 40 C.F.R. Part 268,
and transported in accordance with United States Department of
Transportation (DOT) regulations, 49 C.F.R. Parts 107 and 171.1-
172.604.
Wells now in use, if found to be contaminated, could also be
replaced with, walls screened in deeper uncontaminated aquifers
thus preventing the use of the shallow contaminated aquifer. Two
aquifers, the Cheswold and Frederica, could adequately supply the
needs of area residents. The Cheswold aquifer is located 60 to
100 feet below ground surface. Although the Columbia, the
uppermost aquifer beneath the site, provides recharge to the
lower aquifers, the levels of contaminants at 60 to 100 feet
would not be expected to exceed cleanup levels. Wells would be
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installed in accordance with Delaware Regulations Governing the
Construction of Water Wells, Title 7, Delaware Code, Chapter 60,
S 6010.
The final decision as to which option would be implemented, well
head treatment or well replacement, would be made by DNREC and
EPA. Cooperation from property owners would be necessary to
accommodate installation and maintenance of well head treatment
systems or installation of new wells. Again, the alternate water-
supply contingency would be in effect until cleanup levels have
been achieved through natural attenuation, which is expected to
take approximately 14 years.
The cost estimates listed above reflect the range in costs for
the alternate water supply options. The FS assumed that an
alternate water supply might be provided at two residences
immediately downgradient of the Chem-Solv property. The actual
number of wells which might be affected may differ from this
estimate.
Both well head treatment and well replacement are considered
administratively feasible. Well head treatment has been used at
other sites and is proven effective. Both options would require
the cooperation of the affected property owners. Well
installation would also require approval from DNREC. As
discussed in Alternatives l and 2 above, policy reviews of the
remedial action would be conducted no less often than every five
years from the initiation of the remedial action in accordance
with EPA guidance set forth in "Structure and Components of Five-
year Reviews," May 23, 1991, OSWER Directive 9355.7-02.
Alternative 4s around Water Monitoring, around Water Restriction
Zone, Alternate Water Supply, around water
Collection, Discharge to POTW
Capital Costs: $110,000 - $234,000
Annual O&M: $57,000 - $148,000
Present Worth: $660,000 - $686>000 '
Alternative 4 is essentially Alternative 3 with active
remediation incorporated to remove contaminants from the affected
aquifer. In addition to the ground water monitoring program
discussed in Alternative l, the ground water restriction zone
discussed in Alternative 2, and the alternate water supply
discussed in Alternative 3, Alternative 4 would include ground
water collection from the aquifer. An estimated 8 recovery wells
would be installed onsite to capture the contaminated ground
water in the Columbia aquifer. The volume of the contaminated
ground water has been estimated at approximately 58,500 cubic
feet. The collected ground water would then be discharged to the
Kent County Publicly Owned Treatment Works (POTW) via a Cheswold
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District sanitary sever located onsite. Treatment of the
discharged water would be carried out at the POTW.
The pumping rate could vary depending on discharge limitations.
The Kent County Engineering Office has indicated that proposed
regulations could limit discharge to 5 gallons per minute (gpm)
but that variances from these limits may be available on a case-
by-case basis. Estimates for cost and length of time needed for
remediation were calculated for pumping rates of 5 gpm and 20
gpm. At 5 gpm, cleanup levels would be reached in an estimated 8
years. At 20 gpm, cleanup levels would be reached in an
estimated 2 years. The range in costs listed above reflects the
difference in the length of time that pumping would be required
at the different pumping rates. Also reflected in the cost range
is the difference in the impact fee charged by the POTW at
different pumping rates.
The discharge of collected ground water would be carried out in
accordance with the General Pretreatment Regulations for
discharge to POTWs, 40 C.F.R. Part 403, and any local
pretreatment standards established by the Kent County POTW. The
Kent County Engineering Office has indicated that collected
ground water from the Chem-Solv site could most likely be
discharged directly to the POTW without pretreatment because of
the low levels of contaminants.
The ground water monitoring program proposed in the FS for 8
years of active remediation would include quarterly monitoring
for 2 years, semiannual monitoring for the next 5 years, and
annual monitoring for 4 years thereafter. For a two year
treatment program, monitoring would be performed quarterly for 2
years and semiannually for the next 3 years. Costs listed above
are based on these proposals. Actual monitoring program
specifics will be determined by EPA during the remedial design.
Installation of new recovery wells is easily implementable
because of information generated during installation of the DNREC
collection system. A connection to the sanitary sewer system is
readily available. Obtaining final approval from the Kent County
POTW to accept the discharge from the site could pose a future
problem for implementation of Alternative 4. Kent County has
expressed some concern with accepting discharge from the Chem-
Solv site because of capacity problems at the treatment facility.
As discussed in Section 5.2.1, the contamination at well 26A may
be influenced by both Chem-Solv releases and sources (e.g.,
former USTs) on the property on which well 26A is located, since
well 26A is located downgradient to Chem-Solv and the
contaminants found there can be partially attributed to Chem-
Solv, this area is included in the remedial action for the Chem-
Solv site. One concern with pumping and collection of ground
water is that if sources remain on the adjacent property, then
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benzene and manganese concentrations could increase in the ground
water as a result of pumping. EPA anticipates, however, that
during the remedial action, both benzene and manganese will be
remediated to cleanup levels. Policy reviews would be conducted
in accordance with EPA guidance set forth in "Structure and
Components of Five-Year Reviews," May 23, 1991, OSWER Directive
9355.7-02 no less often than every 5 years from initiation of the
remedial action to evaluate the performance of the remedial
action. ' The possibility of other sources of contamination
remaining on the adjacent property and the influence of those
sources on the probability of achieving the cleanup levels for
the site would be evaluated at that time.
Some uncertainty also exists as to whether ground water
collection will significantly reduce the concentrations of
contaminants in the ground water. Increased flow velocities
caused by pumping may not allow enough time for contaminants in
ground water and soil in the saturated zone to reach equilibrium,
hence the desorption of contaminants from the aquifer soils may
be the rate-limiting step in contaminant removal from the
aquifer. In order to overcome this potential problem, pulsed
pumping might have to be employed to allow for equilibrium
conditions between contaminants in ground water and soil to be
reached to more effectively remove the contaminants in the ground
water. Aquifer tests would need to be performed during remedial
design, and possibly during the remedial action, to optimize
recovery of contaminants with a pulsed pumping system. The
pumping rates and other operational considerations associated
with the ground water collection system would be determined by
EPA during the remedial design.
Alternative 5: around water Monitoring, around Water Restriction
Zone, Alternate Water Supply, around Water
Collection, onaite Treatment, Discharge to Local
Surface Water
Capital Cost: $181,000 - $185,000
Annual O&M: $148,000 - $189,000
Present Worth: $687,000 - $688,000
Like Alternative 4, Alternative 5 includes the ground water
monitoring program, ground water restriction zone, alternate
water supply, and active remediation of contaminated ground water
by collection via a series of recovery wells. In this case
however, rather than discharging to the POTW, collected ground
water would be treated onsite to meet cleanup levels. Collected
ground water would then be discharged to local surface water by
way of a storm sewer located about ten feet south of the Chem-
Solv property line. A discharge pipeline would be constructed to
connect the onsite treatment system to the storm sewer system.
The pumping rate developed in the FS was 20 gpm which was
projected to result in reaching cleanup levels in 2 years.
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The onsite treatment system would consist of filtration and air
stripping of ground water in order to reaove both .vocs and
manganese. Water from the collection system veils would be piped
to a storage/equalization tank for holding before treatment.
Manganese would be removed by filtration. A treatability study
would be performed before final design of the treatment system to
determine whether permanganate pretreatment is required for
manganese precipitation in addition to filtration. The exact
process design to implement this alternative would be determined
by EPA after the treatability study and an aquifer test were
conducted during the remedial design phase. The aquifer test
would be performed before design of the treatment system to
verify that the projected removal rates and discharge standards
could be achieved.
Effluent from the manganese removal process would enter an air
stripping column for removal of VOCs. Treated ground water would
be discharged to a storage tank where it would be collected and
sampled before discharge to a nearby storm sewer for transport to
the Alston Branch of the Leipsic River.
Discharge of treated water to local surface water would meet the
substantive requirements of the National Pollutant Discharge
Elimination System (NPDES) program, 40 C.F.R. Part 403, and would
comply with federal and state water quality regulations including
Clean Water Act Water Quality Criteria for Protection of Human
Health and Ambient Water Quality Criteria for Protection of
Aquatic Life, 33 U.S.C. S 1314(a)(1), Delaware Water Quality
Standards, Stream Quality Standard 10, and Delaware Surface Water
Quality Standards of February 1990, S 9.3(a)(i) and S 9.3(b)(i).
Discharge would also comply with the Delaware Wetlands Act of
1973, Title 7, Delaware Code, Chapter 66, S 6607 and 40 C.F.R.,
Part 6, Appendix A.
The collection, treatment, and discharge facilities would be
sited in compliance with all location-specific ARARs including
the Archaeological and Historic Preservation Act of 1974, 16
U.S.C. S 469 and the National Historic Preservation Act of 1986,
16 U.S.C. $470. The design, construction and operation of the
collection, treatment, and discharge systems would comply with
RCRA requirements set forth in the Delaware Regulations Governing
Hazardous Waste, Parts 262-264 (40 C.F.R. Parts 262-264).
Offsite transport and disposal of treatment residuals would be
performed in compliance with RCRA regulations governing the
handling of hazardous wastes, Delaware Regulations Governing
Hazardous Waste, Parts 262-264 (40 C.F.R. Parts 262-264), Land
Disposal Restrictions, 40 C.F.R. Part 268, and DOT regulations
for transport of hazardous materials, 49 C.F.R. Parts 107 and
171.1-172.604.
25
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VOC emissions from the air stripper are estimated.at 0.05
pounds/day. This estimate is based on maximum concentrations of
vocs found in ground water during the RI and a pumping rate of 20
gpm. Actual emissions from the air stripper would be determined
during design and implementation of the remedial action and would
comply with all state and federal regulations. The major
regulations and guidelines include the following: National
Ambient Air Quality Standards (NAAQS), 40 C.F.R. Part 50;
National-Emissions Standards for Hazardous Air Pollutants
(NESHAPS), 40 C.F.R. Part 61; and Delaware Regulations Governing
the Control of Air Pollution, 7 Delaware Code, Chapter 60, §
6003, Reg 2, §2.4. In addition, emissions from the air stripper
would comply with EPA policy for control of air emissions from
Superfund sites contained in OSWER Directive 9355.0-28 entitled
"Control of Air Emissions from Superfund Air Strippers at
Superfund Ground Water Sites," June 15, 1989.
Emissions would also be controlled so as not to pose a
carcinogenic risk to human health greater than 1 x 10" . A risk
assessment for the treatment system would be performed to
calculate the risk presented by the emissions of VOCs. Emission
controls would be implemented if this value were to be exceeded.
Costs for such emissions controls were not included in the cost
figures listed above for this alternative.
The treatment technologies for this alternative have proven
effective for the contaminants of concern at this site and are
commercially available. The treatment system could be easily
designed and implemented, as could the collection system.
Discharge of treated effluent to surface water would require
approval by DNREC. Operation and maintenance of the collection
and treatment systems would be conducted until monitoring
indicates that cleanup levels have been achieved throughout the
contaminated area.
costs listed above include quarterly monitoring for 2 years, the
estimated length of active remediation, and semiannual monitoring
for 3 years thereafter. Uncertainties regarding capture of
contamination from possible offsite sources by the collection
system and the probability of the system significantly reducing
contaminant concentrations discussed in Alternative 4 also apply
to this alternative. Policy reviews of the remedial action would
be conducted no less often than every five years in accordance
with EPA guidance set forth in "Structure and Components of Five-
Year Reviews," May 23, 1991, OSWER Directive 9355.7-02.
9.0 BUMMMtY Of COMPXRATIVg AMXItYSIfl O> XLTgRMXTrVES
The five remedial action alternatives described above were
compared against the nine evaluation criteria set forth in the
NCP, 40 C.F.R. S 300.430(e)(9). These nine evaluation criteria
can be categorized into three groups: threshold criteria,
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primary balancing criteria, and modifying criteria. The criteria
associated with each category are as follows:
CRITKKIA
• Overall protection of human health and the
environment
• Compliance with applicable or relevant and appropriate
requirements ( ARARS )
PRIMARY PaLM*CING CRITERIA
Long-term effectiveness
Reduction of toxic ity, mobility, or volume through
treatment
Short-term effectiveness
Implementability
Cost
MODIFYING CRITERIA
• Community acceptance
• Support agency acceptance
These evaluation criteria relate directly to requirements in
S 121 of CERCLA, 42 U.S.C. S 9621, which determine the overall
feasibility and acceptability of the remedy. Threshold criteria
must be satisfied in order for a remedy to be eligible for
selection. Primary balancing criteria are used to weigh major
trade-offs between remedies. Support agency and community
acceptance are modifying criteria formally taken into account
after public comment is received on the Proposed Plan.
The following discussion summarizes the evaluation of the five
remedial alternatives developed for the Chem-Solv site against
the nine evaluation criteria.
8, x Overall Protect ion of H***^^ H*%lth aiid the EB'tr'tr"t*<*ent
A primary requirement of CERCLA is that the selected remedial
action be protective of human health and the environment. A
remedy is protective if it reduces current and potential risks to
acceptable; levels under the established risk range posed by each
exposure pathway at the site. Because no environmental risks
were identified at this site, this section will be limited to
discussing protection of human health only.
Of the five alternatives evaluated, Alternatives 4 and 5 provide
the greatest overall protection of human health. Through the use
of institutional controls, a ground water restriction zone and
deed restrictions, exposure to contaminated ground water is
eliminated by restricting future installation of residential
27
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yells in the contaminated area. The contingency for an alternate
water supply also provides protection for current .users in the
area by providing well head treatment to reduce contaminant
concentrations to cleanup levels or by installation of a new well
into an uncontaminated aquifer if necessary. In addition, active
collection and treatment of contaminated ground water prevents
further migration of the contaminant plume, thus reducing the
possibility of exposure to additional residents further
downgradient. Alternative 5, however, may pose an additional
risk to nearby residents by way of air emissions of VOCs from the
onsite air stripper. If determined by EPA to be necessary,
emission controls would be implemented to minimize the risk.
As with Alternatives 4 and 5, Alternative 3 is protective of
current and future users of ground water in the known area of
contamination; however, since no active collection is employed in
Alternative 3 to prevent further migration of contaminated ground
water, future exposure to residents further downgradient is not
eliminated. Alternative 3 therefore does not provide the same
level of protection as Alternatives 4 and 5.
Neither Alternative 1 nor Alternative 2 is protective of human
health. Alternative 1 does nothing to reduce or eliminate
exposure for current or future users of ground water and allows
continued migration of contamination. Alternative 2 provides
protection for future users through the institution of a ground
water restriction zone but does not provide a contingency for an
alternate water supply for current users whose wells may become
contaminated during the time required for natural attenuation to
achieve cleanup levels. Since both of these alternatives fail to
meet the threshold criterion of overall protection of human
health, they will not be discussed further in this section.
9.2 Compliance with XRARs
This criterion addresses whether a remedy will meet all of the
applicable or relevant and appropriate requirements (ARARs) of
other federal and state environmental laws and/or provides
grounds for invoking a waiver. Table 11 summarizes the ARARs for
the site.
Alternatives 3/4 and 5 would comply with all ARARs associated
with drinking water standards (MCLs and non-zero MCLGs), offsite
disposal of treatment wastes from well head treatment, and
Delaware Regulations Governing the Construction of Water Wells.
Pretreatment requirements for discharge to the POTW would also be
met for Alternative 4. Additional ARARs associated with
Alternative 5 which would be complied with include federal and
state requirements pertaining to point source discharge to
surface water including effluent limitations based on state water
quality standards and federal ambient water quality criteria.
Alternative 5 would also meet ARARs for design construction and
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operation of the onsite treatment system, for air. emissions from
the air stripper and for offsite disposal requirements for any
treatment wastes produced by the onsite treatment system.
Long-term effectiveness and permanence refers to the ability of a
remedy to maintain reliable protection of human health and the
environment over time once cleanup levels have been achieved.
Alternatives 4 and 5 provide a high degree of long-term
effectiveness by employing ground water collection and treatment
to reduce contaminant levels, thereby reducing risk. Any
residual contamination remaining in the ground water after
cleanup levels have been met would be present at levels which
would not exceed an acceptable risk level.
Alternative 3 would provide active treatment of ground water only
at the well head and would do nothing to reduce contamination in
the aquifer or to prevent contamination from migrating further
downgradient. Exceedances of cleanup levels would continue.
Therefore, Alternative 3 provides a lesser degree of long-term
effectiveness and permanence when compared to Alternatives 4 and
5.
8.4 Reduction in Toxieitv* Mobility* or vol***^ TnT^Tfr Treatment
Reduction of toxicity, mobility, or volume through treatment
refers to the anticipated performance of the treatment
technologies that a remedy may employ. There is a statutory
preference under CERCLA for selecting remedial actions that
employ treatment technologies that permanently and significantly
reduce the toxicity, mobility or volume of hazardous substances.
Alternatives 3, 4 and 5 would reduce the toxicity of the ground
water at specific residential wells through well head treatment
to remove manganese and/ or VOCs. This is the- only provision for
active remediation in Alternative 3. In contrast, Alternatives 4
and 5 would also reduce the toxicity, mobility, and volume of
contaminated ground water in the aquifer through ground water
collection and treatment. Both alternatives would treat a much
larger volume of ground water than Alternative 3.
Treatment at the POTW included in Alternative 4 would reduce the
toxicity and volume of both manganese and VOCs in the collected
ground water. No treatment residues would be produced at the
site.
Onsite treatment by filtration in Alternative 5 would reduce the
toxicity and volume of contaminants in the collected ground water
by removing manganese, but would result in treatment residues
which would require offsite disposal. The toxicity and volume of
29
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contaminants in collected ground water would also' be reduced by
air stripping onsite but emissions would ultimately be
transferred to the ambient air. Controls for reducing levels of
air emissions to the atmosphere would be implemented if
determined by EPA to be necessary.
8.5 Short-term Effectiveness
Short-term effectiveness refers to the period of time needed to
achieve protection and any adverse impacts on human health and
the environment that may be posed during the construction and
implementation, until cleanup levels are achieved.
Alternatives 3, 4 and 5, which include ground water monitoring, a
ground water restriction zone, and a contingency alternate water
supply, provide a high degree of short-term effectiveness for
local residents during remedial action and effectively prevent
exposure to contaminated ground water. Monitoring and
institution of the restriction zone could be implemented in a
relatively short time frame. An alternate water supply would be
provided if contamination from the site is detected above cleanup
levels in a residential well.
Implementation of either Alternative 4 or 5 would result in a
slight potential for exposure to nearby residents and workers
through direct contact with and inhalation of vapors from the
contaminated ground water during installation of recovery wells
or replacement of residential wells. In addition, workers would
be exposed to normal drilling and construction hazards during
installation of wells and construction of the collection system.
These risks could be mitigated by following proper health and
safety practices for well drilling and construction.
Alternative 5 would pose an additional risk to workers due to
construction and operation of the onsite treatment system and the
offsite disposal of treatment residues. Air emissions from the
onsite air stripper may pose an added risk to workers and
residents in the area. If determined by EPA to be necessary,
proper emission controls would be implemented to minimize risk.
8.6
Implementability refers to the technical and administrative
feasibility of a remedy, including the availability of materials
and services needed to implement each component.
The institutional controls included in Alternatives 3, 4 and 5
should not pose any major implementation problems. Ground water
monitoring and replacement of existing wells would be performed
using widely practiced techniques. Well placement would be
conducted in accordance with state regulations. Well head
treatment systems have been shown to be effective in removing the
30
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contaminants associated with this site. Residuals from well head
treatment would need to be disposed of properly and cooperation
from property owners would be necessary for well installation and
maintenance. A ground water restriction zone would have to be
established and enforced by DMREC but is considered
administratively feasible.
For Alternatives 4 and 5, installation of new recovery wells is
easily implementable because of information generated during the
installation of the DNREC collection system. Discharge to the
POTW in Alternative 4 would require meeting the pretreatment
requirements of the POTW. Kent County has indicated that
discharge from the site could be accepted untreated but that the
capacity of the treatment plant might be a limiting factor in
determining the acceptable pumping rate. Kent County has
expressed some reservations with accepting discharge from the
site due to capacity limitations at the treatment facility. If
the collected ground water is discharged there, they have
suggested that certain control mechanisms would have to be placed
on the collection system and that the capacity- of the POTW might
be a limiting factor in determining the acceptable discharge
rate. These requirements would need to be considered in the
design of the remedial action but do not appear to present a
problem with implementation. However, to date, the POTW has not
committed to accepting the discharge from the site.
Alternative 5, while considered feasible, would be more
complicated to implement. For this alternative, a treatment
system for the contaminants of concern would have to be designed,
installed, and operated. The technologies being considered have
been demonstrated successfully in full scale operations for the
contaminants of concern. A treatability study would need to be
performed before treatment system design to optimize the process
and ensure that discharge requirements would be met. In
addition, discharge of treated effluent to surface water would
re ~iire compliance with the substantive requirements of the
National Pollutant Discharge Elimination System (NPDES) program
of the Clean Water Act. Solids removed by treatment processes
would require disposal as hazardous waste but are expected to be
minimal.
8.7 Coat
The capital, annual operation and maintenance, and present worth
costs for all five alternatives evaluated in the FS are
summarized in Table 12. The present worth values for
Alternatives 4 ($660,000 - $686,000) and 5 ($687,000 - $688,000)
are essentially the same. The present worth value of Alternative
3 is $410,000 - $431,000.
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8.8
The State of Delaware concurs with the selected remedy presented
in Section 9.0 of this document.
8 » 9 co*""iT^ itv Acceptance
Generally, local residents expressed no opposition to the
selected' remedy. Kent County expressed some concern with the use.
of the POTW for discharge of collected ground water from the site
due to capacity problems. The PRPs submitted comments regarding
the use of ground water collection and treatment. All comments
received during the public comment period concerning the various
alternatives are summarized in the Responsiveness Summary which
is a part of this ROD.
Based on the findings in the RI/FS, the nine criteria listed
above, and public comments, EPA has selected Alternative 4 as the
remedy for this site, with a contingency to implement an onsite
treatment system with discharge to surface water identified as
part of Alternative 5. The onsite treatment system with
discharge to surface water is designated as the contingency
remedy. The contingency remedy (i.e., onsite treatment) shall be
employed if an agreement with the POTW cannot be reached. The
final decision as to whether to treat the collected ground water
onsite or to provide treatment at the POTW will be made by EPA
during the early stages of the remedial design. The selected
remedy consists of the following major components:
• Collection of contaminated ground water
• Discharge of collected ground water to the Kent County
POTW, or the contingency remedy, onsite treatment and
discharge to local surface water
• Ground water monitoring
• Contingency for an alternate water supply
• Institution of a ground water restriction zone
• Deed restrictions
• Removal of existing recovery wells
Each component of the remedy and appropriate performance
standards are described below.
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A. Collection of Contaminated around Water
Ground water shall be collected from the aquifer using multiple
recovery wells, the exact location and number of which shall be
determined by EPA. Recovery wells shall be installed in
accordance with Delaware Regulations Governing the Construction
of Water Wells, Title 7, Delaware Code, Chapter 60, S 6010.
Performance Standard* for around Water Collection:
1. The number and location of recovery wells shall be
sufficient to prevent further contaminant migration and to
capture all ground water containing site-related
contaminants of concern which exceed the cleanup levels
listed in Table 10.
2. The collection of ground water shall reduce contaminants of
concern in the aquifer to the cleanup levels listed in Table
10. The "point of compliance", or the point at which
compliance with the cleanup levels will be measured, shall
include all wells included in the monitoring program
discussed below. Based on statistical analysis, if sampling
confirms that cleanup levels have been attained throughout
the contaminated area and remain at the cleanup levels for
twelve consecutive quarters, operation of the collection
system can be suspended. If, subsequent to the collection
system shutdown, quarterly monitoring shows the ground water
concentrations of the contaminants of concern above cleanup
levels, the collection system shall be restarted and
continued until the cleanup levels have once more been
attained for twelve consecutive quarters.
B. Discharge of collected Ground Water to Kent County POTW or
oneite Treatment with Discharge to Local Surface Water.
Collected ground water shall be discharged to the Kent County
POTW via a Cheswold District sanitary sewer line which is present
onsite. An operation and maintenance plan approved by EPA shall
be required for the ground water collection and discharge
systems.
Performance Standard for Discharge to the POTW:
Collected ground water which is discharged to the POTW shall
meet the General Pretreatment Regulations for discharge to
POTWs, 40 C.F.R. Part 403, and any local pretreatment
standards established by the Kent County POTW.
Some reluctance to accept the discharge from the site has been
expressed by the Kent County POTW due to potential capacity
limitations at the treatment facility. Consequently, a firm
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commitment to accept the discharge has not been received from
Kent County. Because some uncertainty exists with the
implementation of this aspect of the remedy, a contingency has
been selected to prevent future complications and delays in the
remediation of this site.
In place of offsite discharge of collected ground water to the
POTW, the contingency remedy shall include onsite treatment of
the collected ground water and discharge to local surface water
as discussed in Alternative 5 (Section 7.0). All other
components of the selected remedy discussed above shall be
identical. The decision as to whether to discharge the collected
ground water to the Kent County POTW or to treat it onsite and
discharge to surface water, shall be made by EPA at the onset of
remedial design. If, at that time, a firm commitment from the
Kent County POTW to accept the discharge for the duration of the
remedial action has been received and documented, then the
remedial design shall proceed with discharge to the POTW. If a
firm commitment has not been obtained, however, the remedy shall
change to the contingency and remedial design shall proceed with
onsite treatment and discharge to local surface water.
If the contingency remedy is implemented, collected ground water
shall be treated onsite. Treated water shall be discharged to
the Alston Branch of the Leipsic River via a storm sewer
connection located just south of the site. A connection to the
storm sewer shall be constructed for this purpose.
EPA expects that collected ground water will be treated onsite by
filtration and air stripping; however, information submitted
during the public comment period indicated that additional unit
processes for onsite treatment may be available. Therefore,
further evaluation of these unit processes may be performed
during a pre-design study and EPA shall determine the most
appropriate process to be incorporated into the design of the
onsite treatment system should the contingency remedy be
implemented. The selection of the actual unit process to be
utilized will be based on its demonstrated ability to effectively
remove the contaminants of concern in a cost-effective manner in
order to achieve compliance with the ARARs and performance
standards set forth in this ROD.
Performance Standards for onsite Treatment and Discharge to
surface Waters
1. The onsite treatment system shall reduce contaminants in the
collected ground water to the cleanup levels listed in Table
10.
2. Discharge of treated water to local surface water shall meet
the substantive requirements of the National Pollutant
Discharge Elimination System (NPDES) program, 40 C.F.R. Part
34
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403, and shall comply with federal and state water quality
requirements including Clean Water Act Water.Quality
Criteria for Protection of Human Health and Ambient Water
Quality Criteria for Protection of Aquatic Life, 33 U.S.C. $
1314(a)(1), Delaware Water Quality Standards, Stream Quality
Standard 10, and Delaware Surface Water Quality Standards of
February 1990, S 9.3(a)(i) and $ 9.3(b)(i). Discharge shall
also comply with the Delaware Wetlands Act of 1973, Title 7,
Delaware Code, Chapter 66, S 6607 and 40 C.F.R., Part 6,
Appendix A.
3. If an air stripper is included as part of the onsite
treatment system, a risk assessment shall be performed for
air emissions. Emissions from the air stripper shall not
exceed a cumulative carcinogenic risk of 1 x 10~4. If this
level is exceeded, emission controls shall be installed to
reduce emissions below this level. Air stripper emissions
shall also be in compliance with National Ambient Air
Quality Standards, 40 C.F.R. Part 50, National Emissions
Standards for Hazardous Air Pollutants, 40 C.F.R. Part 61,
Delaware Regulations Governing the Control of Air Pollution,
7 Delaware Code, Chapter 60, S 6003, Regulation 2, S 2.4,
and "Control of Air Emissions from Superfund Air Strippers
at Superfund Ground Water Sites," June 15, 1989, OSWER
Directive 9355.0-28.
The collection, treatment, and discharge facilities shall be
sited in compliance with all location-specific ARARs including
the Archeological and Historic Preservation Act of 1974, 16
U.S.C. S 469 and the National Historic Preservation Act of 1986,
16 U.S.C. S 470. The design, construction and operation of the
collection and treatment systems shall comply with RCRA
requirements set forth in Delaware Regulations Governing
Hazardous Waste, Parts 262-264 (40 C.F.R. Parts 262-264).
Offsite transport and disposal of treatment residuals shall be
performed in compliance with RCRA regulations governing the
handling of hazardous wastes set forth in Delaware Regulations
Governing Hazardous Wastes, Parts 262-264 (40 C.F.R. Parts 262-
264), Land Disposal Restrictions, 40 C.F.R. Part 268, and DOT
regulations for transport of hazardous materials, 49 C.F.R. Parts
107 and 171.1-172.604.
An operation and maintenance plan approved by EPA shall be
required for the ground water collection and onsite treatment
system.
The performance of the ground water collection and discharge
systems in the selected remedy or the collection and onsite
treatment systems in the contingency remedy shall be carefully
monitored on a regular basis. If determined to be appropriate by
35
-------
EPA, the system may be modified, as warranted by performance data
collected during operation. These modifications may include any
or all of the following:
1) at individual wells where cleanup levels have been attained,
pumping may be discontinued;
2} alternating pumping at wells to eliminate stagnation
points;
3) pulse pumping to allow aquifer equilibration and encourage
adsorbed contaminants to partition into ground water; and
4) installation of additional recovery wells to facilitate or
accelerate cleanup of the contamination.
C. Ground Water Monitoring
A ground water monitoring program shall be implemented to
evaluate the effectiveness of the ground water collection and
treatment systems in meeting cleanup levels and to ensure
protection of nearby residents. EPA shall determine the exact
location of monitoring wells and residential wells to be included
in the monitoring program. The frequency and duration of
sampling and the analytical parameters and methods to be used
shall also be determined by EPA during remedial design. In
addition, an operation and maintenance plan approved by EPA shall
be implemented for the ground water monitoring program.
Monitoring shall continue for an estimated 30 years or such other
time period as EPA deems necessary based on the policy reviews of
the remedial action which shall be conducted not less than every
five years from initiation of the remedial action in accordance
with EPA guidance set forth in "Structure and Components of Five-
Year Reviews," May 23, 1991, OSWER Directive 9355.7-02. Policy
reviews will be conducted until EPA determines that the cleanup
levels set forth in this ROD have been achieved, or that the
hazardous substances remaining on the site do not prevent
unlimited use and unrestricted exposure at the site.
D. contingency for aa Alternate Water supply
If through the ground water monitoring program EPA determines
that any existing residential well is contaminated with
contaminants of concern above cleanup levels, an alternate water
supply shall be provided to that residence. The choice of the
alternate water supply shall be made by EPA and DNREC and shall
be based on the contaminants detected and the hydrogeology of the
affected area. The alternate water supply shall consist of
either well head treatment at the point of use or installation of
a new well in an uncontaminated aquifer. Well head treatment
shall consist of filtration to remove inorganic contaminants
and/or carbon adsorption units to remove VOCs. An operation and
36
-------
maintenance plan approved by EPA shall be required for the well
head treatment systems.
Performance Standard for Alternate water Supply:
The well head treatment system shall reduce the contaminants of
concern in the water to the cleanup levels listed in Table 10.
The well head treatment system will result in the production of
residual.treatment wastes. Any wastes (e.g., spent carbon
adsorption units or filtration media) shall be handled and
disposed of offsite in accordance with Delaware Regulations
Governing Hazardous Waste, Parts 262-264 (40 C.F.R. Parts 262-
264), land disposal restrictions, 40 C.F.R. Part 268, and DOT
regulations, 49 C.F.R. Parts 107 and 171.1-172.604. Any
residential wells which are replaced shall be installed in
accordance with Delaware Regulations Governing the Construction
of Water Wells, Title 7, Delaware Code, Chapter 60, S 6010. The
replacement well shall be installed in an uncontaminated aquifer
in order to provide a sufficient quantity of water which meets
cleanup levels identified in Table 10.
B. institution of a Ground Water Restriction Zone
As soon as practicable, DNREC shall institute a ground water
restriction zone in which no drinking water wells shall be
permitted to be installed in the Columbia aquifer until cleanup
levels have been achieved throughout the contaminated area.
Performance standard for the Restriction Zones
EPA and DNREC shall determine the extent of the ground water
restriction zone which shall encompass the entire contaminated
area including an appropriate buffer zone, and shall prohibit
installation of drinking water wells in the uppermost water table
aquifer, the Columbia aquifer, until cleanup levels have been
achieved.
F. Deed Restrictions
As soon as practicable, deed restrictions shall be placed on the
deeds of all properties situated in the restriction zone. Deed
restrictions shall notify present and potential future property
owners that the property is situated within the boundaries of a
ground water restriction zone. The deed restrictions shall
remain in effect until cleanup levels are achieved throughout the
contaminated area.
Q. Removal of Existing Recovery Wells
All recovery wells installed by DNREC as part of the collection
system which operated from 1985 to 1988 and which are presently
located on the Chem-Solv property shall be removed. All existing
37
-------
recovery wells shall be removed in accordance with the Delaware
Regulations Governing the Construction of Water Wells, Title 7,
Delaware Code, Chapter 60, S 6010.
This remedial action shall restore ground water to its beneficial
use, which at this site includes its use as a potential drinking
water source. It may become apparent during implementation or
operation of the remedy that contaminant levels have ceased to
decline and are remaining constant at levels higher than the
cleanup levels over some portion of the contaminated area. If
EPA determines that implementation of the selected remedy
demonstrates, in corroboration with hydrogeologic and chemical
evidence, that it will be technically impracticable to achieve
and maintain the cleanup levels throughout the entire area of
ground water contamination, EPA may require that any or all of
the following measures be taken, for an indefinite period of
time, as further modifications of the existing system:
1) long-term gradient control may be provided by low level
pumping, as a containment measure;
2) cleanup levels may be modified and chemical-specific ARARs
may be waived for those portions of the aquifer for which
EPA determines that it is technically impracticable to
achieve further contaminant reduction;
3) institutional controls- may be provided/maintained to
restrict access to those portions of the aquifer where
contaminants remain above cleanup levels; and
4) remedial technologies for ground water restoration may be
reevaluated.
The decision to invoke any or all of these measures may be made
by EPA during policy reviews of the remedial action which will
occur at least every 5 years from commencement of the remedial
action in accordance with EPA guidance set forth in "Structure
and Components of Five- Year Reviews," May 23, 1991, OSWER
Directive 9355.7-02. If necessary, EPA will issue an Explanation
of Significant Differences or a ROD amendment.
10* 0 BTXTDTOttT
EPA's primary responsibility at Superfund sites is to undertake
remedial actions that are protective of human health and the
environment. In addition, S 121 of CERCLA, 42 U.S.C. S 9621,
establishes several other statutory requirements and preferences
These requirements specify that when complete, the selected
remedial action for each site must comply with applicable or
relevant and appropriate (ARARs) environmental standards
established under federal and state environmental laws unless a
38
-------
statutory waiver is invoked. The selected remedy also must be
cost effective and utilize treatment technologies or resource
recovery technologies to the maximum extent practicable.
Finally, the statute includes a preference for remedies that
permanently and significantly reduce the volume, toxicity or
mobility of hazardous substances. The following sections discuss
how the selected remedy for this site meets these statutory
requirements .
10.1 Protection of H****** Health and the Environment — Both the
selected remedy and the contingency remedy protect human health
and the environment by controlling exposure to contaminated
ground water associated with the site. Ground water collection
will prevent further migration of contamination from the site
which might lead to exposure of additional residents. Ground
water monitoring will track the contamination in the ground water
and will ensure that any unacceptable levels of contaminants in
residential wells will be detected and addressed. If necessary,
well head treatment will reduce contaminant levels to acceptable
cleanup levels or well replacement will provide water from an
uncontaminated aquifer, thereby reducing or eliminating
exposure. Ground water collection and treatment will effectively
reduce contaminant levels in the aquifer and consequently will
reduce the potential for exposure to contaminated ground water.
Institutional controls, which provide for the establishment of a
ground water restriction zone and deed restrictions, will prevent
future exposure to contaminated ground water by prohibiting the
future installation of wells in the contaminated aquifer until
cleanup levels are achieved.
Air emissions which might be produced by air stripping included
in the contingency remedy will be reduced to acceptable risk-
based levels by installation of emission controls, if determined
by EPA to be necessary. Treated ground water discharged to
surface water in the contingency remedy will meet all appropriate
water quality standards to prevent any adverse environmental
effects. Through monitoring, institutional controls and
treatment, this remedy will be protective of human health and the
environment during and upon completion of the remedial action.
10 • 2 C*?mt>ti
-------
proportionate to costs. The estimated present worth cost range
for the selected remedy is $660,000 - $686,000 and for the
contingency remedy is $688,000. The costs associated with the
three alternatives that did not include ground water collection
and treatment are comparatively lower ($385,000 - $431,000) than
the costs of the selected remedy but none of those alternatives
would achieve remedial action objectives or ground water cleanup
levels.
10.4 Utilisation of Permanent Solutions and Alternative
selected remedy for the site utilizes permanent solutions and
treatment technologies to the maximum extent practicable. Of
those alternatives that are protective of human health and the
environment and comply with ARARs, EPA has determined that the
selected remedy provides the best tradeoff in terms of long-term
effectiveness and permanence, reduction in toxicity, mobility, or
volume achieved through treatment, short-term effectiveness,
implementability, and cost, also considering the statutory
preference for treatment as a principal element and considering
State and community acceptance.
The selected remedy and contingency remedy both provide long-term
effectiveness and permanence, and reduction of toxicity,
mobility, and volume through treatment. Costs for both are
essentially the same. Provided that the POTW has the capacity
and will accept the discharge from the site, the selected remedy
is more easily implemented as no onsite treatment system has to
be designed, constructed, or operated, no treatability testing
would be needed to optimize the treatment system, no treatment
residuals would be produced onsite or disposed of offsite, no
additional risk would be posed by onsite operation of the
treatment system or emissions from an air stripper. The selected
remedy has therefore been determined to be the most appropriate
solution for the Chem-Solv site. However, the contingency remedy
also fulfills the requirement of using permanent solutions and
alternative treatment technologies to the tMyiTm™ extent
practicable.
10.5 Preference for Treatment as a Principal Bl^nent — The
selected remedy and the contingency remedy use treatment to
address the threats posed by contaminants in the ground water at
the site. This preference for treatment as a principal element
is satisfied since treatment of VOCs and inorganic contaminants
in the ground water are the principal elements of either remedy.
11.0 pocmmppATioM or siainTicAirp CHAHQBS
The following changes have been made since the Proposed Plan was
issued on January 15, 1992:
40
-------
1. The Proposed Remedial Action Plan identified Alternative 4,
ground water collection and discharge to the .POTW, as the
preferred alternative. During the public comment period,
the POTW expressed some concern with accepting the collected
ground water from the site due to capacity problems at the
treatment plant. Consequently, EPA has selected Alternative
4 as the remedy for the site but has selected Alternative 5,
onsite treatment and discharge to surface water, as a
contingency remedy for the site. The contingency remedy
will be employed if an agreement with the POTW cannot be
reached. The final decision as to whether to treat the
collected ground water onsite or to provide treatment at the
POTW will be made by EPA during the early stages of the
remedial design.
2. The Annual O & M costs, which were presented incorrectly in
the Proposed Plan, have been revised. The correct O & M
costs are included in Section 7.0 above and in Table 12.
3. EPA expects that if the contingency remedy is implemented,
collected ground water will be treated onsite by filtration
and air stripping; however, information submitted during the
public comment period indicated that additional unit
processes for onsite treatment may be available. Therefore,
further evaluation of these unit processes may be performed
during a pre-design study and EPA shall determine the most
appropriate process to be incorporated into the design of
the onsite treatment system. The selection of the actual
unit process to be utilized will be based on its
demonstrated ability to effectively remove the contaminants
of concern in a cost-effective manner in order to achieve
compliance with the ARARs and performance standards set
forth in this ROD.
4. The Proposed Remedial Action Plan stated that the cleanup
levels for the site would be risk-based (i.e., a cumulative
carcinogenic risk not to exceed 1 x 10~6 and a Hazard Index
not to exceed 1.0). The Proposed Plan explained that in
many cases MCLs would be used as cleanup levels but that the
cumulative carcinogenic risk associated with the MCLs for
the contaminants of concern at this site was greater than 1
x 10~6 and that the MCLs were therefore not appropriate
cleanup levels. Upon further evaluation and in accordance
with S 300.430(e)(2)(i) of the NCP, 40 C.F.R.
S 300.430(e)(2)(i), EPA has determined that the cumulative
carcinogenic risk associated with the MCLs (2 x 10~5) is
within the acceptable risk range of 10"4 to 10~6.
Therefore, it is appropriate to use non-zero MCLGs and MCLs
as cleanup levels at this site as set forth in Table 10.
Risk-based cleanup levels were developed for manganese and
acetone because MCLs are not available for those substances.
41
-------
Figure 1
8lt» Location Map
-------
Former Conerttt
Pavtd SkattOoarO
P«rk
/ STONE
/ DRIVE
/ WAY
1 STORY
BLOCK
BUILDING
UNKNOWN
CONCRETE /
BLOCK /
^
SOURCE. Mfcrcft it itM Survey (ftoMrt L. Lv«mr*
JUM 4 «IM ». it«0 Stf v«r tx &
C/o»«ng. Pv
LEGEND
• Memanngwvt
Urw
Concratt
EOOR QUAUT
xQR!GINALoc
Figure 2
«•""
ISM)
-------
CHBN-eOLV, IMC.
CHEM.tQiy.MC.finf
8?
I
-fwic*
OPEN nan
ccicuinr
L_
OASOUC SUIKM/
COHVfMENGi STORE
FOmCRfCSTMJKAMT/mJCK STOP
UKO CAN KAICM
mm w
e_
I
I.
r
IMEMKNTUL
.1
|flE9KMIIM. I USED TMICK Of AUK
_l I
rUMftURESIONi
OASOLME SIMUNI
KSDENTW.
ROOFNOMJSMESS,
RE8DEN1IM.
u
KSOENtlAL
ncaieniM.
~» » »»»» »•»«» u a KH
Figut* 3
LandU»«
-------
Cbea-Solv, inc.
OCM.SOIM.MC on
Morttortng WML Oom«tllc WM, So* Boring and StrattgrapMc Boeing Location*
Figure 4
-------
CMf»MtV MC ttlf
r
EJ «
10-1
0-
•CM *•»«> N» 00 »0'» 03
100 f I
Figure 5
Sitottootogte
A. A'
-------
rlgnr*
-------
Sol Boring
NDNoKMKtod
NT Nel HUH
J
(OUNCE: MM* n. tM* (wow nutim L
JMK « «•« >. IMP Sa»«y (J Q ftik Auocnui. tic. WMtxgteti Ciomig. t^roytv«na>
Figure 7
Distribution of Selected Parameters In Sols
-------
f I. IP» HCMT
-------
IBCMI
we snc
1.25* - t Mite
MMItW
Geologic Cro«t Section of Kent County
Figure 9
-------
Tabtel
GHBMOLV.MC me
M •
00
70 79
QO
-------
TABLE 2
CONTAMINANTS OF CONCERN
CONTAMINANT RMB (UQ/11
Acetone 25.1
Benzene 58.6
1,2-dichloroethane (1,2-DCA) 2.7
Tetrachloroethene (PCE) 2.8
Toluene 1.8
1,1,1-trichloroethane 11.9
Trichloroethene (TCE) 245.0
Xylene 1.8
Manganese 14,987.2
-------
Table 3
ASSUMPTIONS USED IN CALCULATING EXPOSURE
Ingeetion Rate Often/day)
Exposure Frtojuency (events/year)
Exposure Duration (yean)
Body Weight (kg)
Dermal Ahvuntton from Oroundwatar UM
Skin surface area (sq. cm)
Exposure time (hours/evert)
Chsdren
1.3
388
S
17
7,128
0.29
tmm.
Adults
2
368
30
70
19,400
O2S
*«•
Reference
EPA (198
Site Spec
EPA (198
EPA (198
LA (198
EPA. 1981
«•*••»«*
Ba and 19896)
Me
Baandi98Bb)
Ba and 19686)
Ba and 19896)
Be
MA
Exposure duration (years)
5 30
17 70
OrlnMngWatarEquivalantFaoor*
OJS
EPA (198BB and 19896)
EPA. 1988
• Sat Section &3£J and AppandtaO of tb« R«a«<9ial Inv«»tig«tion Report
Compladby: BCM EnglManilna (BCM Project Ma 004012-02)
-------
Table 4
TOXICITY VALUES: POTENTIAL CARCINOGENIC EFFECTS
WrigNol-
Slope Factor EvkJence Sourceof
Chemical (mfl/NlAtayM Ctotrflcalnn TumorSto Stope Factor Model
Beiuane Oral 0029 A (1) IRIS On* hi (pooled data)
0.028 A |l| IRIS On* hi (pooled data)
l.2-CMcMor
-------
Table 5
EPA CATEGORIES FOR POTENTIAL CARCINOGENS
EPA
Category
Group A
Group Bl
Group B2
i
Group C
Group 0
Group E
Group
Daacriptfon
Human
CafdnoQan
Probatta Human
Caidnogan
Poaatta Human
Cardnogm
SoA^arfA Um^m^^
r Qva0a nUUMII
Cartinogin
NotOaaaHid
MeBvidanet
Evidtnca
auniavv wn&wnc* ironi •pwraoiogio
SCUfllttB TO SUDOO^t A CAUMl flkSSOCiflDOi^
baMMan axpoaura and cancar in humana
Umttad avfdanea in humana from
apJdamtatogtc aojdlaa
Umttad avtdanca in animate and/or
Inadaquata avidanea In artmala
No avWanca in at laaat ttto adaojuata
Soureac CPA.
-------
Table 6
TOXIOTY VALUES: POTENTIAL NONCAflONOGENIC EH-bCTS
Chtmtaal
Acatont
OhrorteRfD*
(mg/kg/day)
Tatraehloroaihana
Toluana
Tm .
. - ncr
Xyfana
Manganasa
NA
IRIS
HEAST
\
Oral
Oral
Oral
(•ii^j^^»»
nnwDon
Oral
Oral
inhalation
Oral
0.1
0.01
02
0.6 a
0.09
2
0.2
0.1
Confidant
Lava)
Low
Madkjni
Madium
Medium
Madfcjm
Madium
Madkjm
Madbm
» CrUeal
Effact
Kldnay.Uvar
Uvar
Blood
CNS, LVar, Wdnay
Uvar
Mortalty
CNS,Morta*ty
CNS
RID
Sourea
IRIS
IRIS
IRIS
IRIS
IRIS
IRIS
HEAST
IRIS
Uneartalnty and
Modifying Factors
UF
1000
1000
100
NA
1000
100
NA
1
MF
1
1
1
NA
1
1
NA
NA
Notavalabla
intagratad
iSyatam
Haafth Eflacta Aaaaaamant Summary Tabto
Inhalation i
immmmjm UUOT \
._* — _« — u — —
[TWfvmvm
UMM* tf»M « «
irwvnoiG
0.4 fng/pcg/Qivy mi iti*mjKiPURMUwui uum
a
UmOUWMf l«MUi M IMfc
•an uaiaiiiHiaUt urai r
imbar 17. 1900. o29L i
HW VWJOT WWV UMQ VI OTV
Inhalation RfD of
aeommandad
obtahiad from 40i Ouartar 1900 HEAST.
Compltd by: BCM Engfewani Inc. (BCM Projaet No. 004012-02)
-------
Table?
CANCER RISK ESTIMATES
IMCSSTION OF CONTAMINATED ONUMMATER
CHEMICAL
BENZENE
1,2-0ICHLOROETKANE
PCE
TCE
INHALATION OF CONTAMINANTS IN GROUNOWATER OUIIN6 USC
SLOPE
FACTOR
2.96-02
9.16-02
5.16-02
1.16-02
GDI
(•8/ko/*y)
6.06-04
3.06-05
3.0E-05
2.06-03
CHEMICAL
SPECIFIC
RISK
2.0E-05
3.0E-06
2.0E-06
2.0E-05
TOTAL
PATHWAY
EXPOSURE
BENZENE
1,2-OICHLOROETHANE
Ptt
TCE
2.96.02
9.16-02
i.ae-03
1.7E-02
6.0«-04
3.06-05
3.06-05
2.06-03
2.06-05
3.06-06
5.06-08
3.06-05
DERMAL ABSORPTION OF CONTAMINANTS IN GROUNOUATER OURINC USE
BENZENE
1,2-OICHLOROETKANE
PCE
TCE
TOTAL EXPOSURE
2.96-02
9.1E-02
5.1E-02
1.1E-02
2.0E-04
7.0E-06
2.0E-05
4.0E-05
6.0E-06
6.0E-07
1.0E-06
4.0E-07
5.0E-05
5.0EHH
8.0E-06
1.1E-0*
-------
Tables
CHRONIC HAZARD INDEX ESTIMATES
IMGESTION Of CONTAMINANTED GMUNDUATER
CHEMICAL CDI tfO
ADULTS
ACETONE
PCE
TOLUENE
1,1.1-TRICHLOROETHANE
XTLENE
MANGANESE
CHILDREN
ACETONE
PCS
TOLUENE
1,1,1-TRICMLOMETHANl
XTLENE
MANGANESE
INHALATION OF CONTAMINANTS
ADULTS
ACETONE
PCE
TOLUENE
1,1,1-TRICHLOR06TIUN6
XYLENE
CHILDREN
ACETONE
PCE .
TOLUENE
1,1.1-TRICHLORCETHANE
XYLENE
7.01-04
8.06-05
5.06-05
4.06-04
5.06-05
4.0E-01
2.0E-03
2.0E-04
1.0E-04
8.06-04
9.0E-05
1.1E*00
IN GROUNDUATEt
7.0E-04
8.0E-05
5.0E-05
2.06*04
5.06*03
2.01-01
2.01-04
1.01*04
7.01*04
1.01*04
1.0E-01
1.0E-02
2.0E-01
9.06-02
2.06*00
1.06-01
1.0E-01
1.06-02
2.06*01
9.0E-02
2.06*00
1.0E-01
DURING USe
1.06-01
1.01*02
6.01*01
9.01*02
2.01*01
*
1.06*01
1.01*02
6.06*01
9.06*02
2.06*01
4.06*00
2.06*02
2.06*02
5.06-04
9.06*03
5.06*05
1.16*01
1.1E*01
7.06-03
8.06-03
8.01-0$
2.01-03
3.01*04
2.01*02
2.06-02
2.01*02
2.01-04
6.01*03
5.06-04
5.06-02
-------
TABLE 8 (con't)
DERMAL AtSOWTION Of CONTAMINANTS IN GROUMOUATEt DURING USE
ADULTS
ACETONE 8.06-06
PCE 4.06-05
TOLUENE 6.0E-06
1.1.1-TRJCW.OtOETHANe 7.0C-05
XTLEKE • 9.06-06
CMILMEN
ACETONE 9.0E-06
PCE 6.0E-05
TOLUEW 9.0E-06
1,1.1-TRICMLOMETIUUIE 1.0E-04
XTLENE 9.0B-06
TOTAL EXPOSURE AOULTS
TOTAL EXPOSURE CHILDREN
1.0E-01
1.0E-02
2.06-01
9.0E-02
2.06*00
8.0E-05
4.0E-03
3.0E-05
a.OE-OA
S.OE-06
1.0E-01
1.0E-02
2.0E-01
9.0E-02
2.0E*00
9.01-0$
6.06-03
5.0E-OS
1.0E-OX
S.OE-06
5.0E-Q3
7.0E-03
1.16*01
-------
TABLE 9
COMPARISON OF WATER QUALITY GUIDELINES TO PREDICTED
' ENVIRONMENTAL CONCENTRATIONS
Watar Quafltv Gulddtn«a
Pradfctad Concantratlons at
tha Point of Rataaaa (ug/l)**
Chemical
Aeutt
Chronic
Avaitgt
RM€
Maximum
Acatana
Banzana
Cnfoforonn
i.i*0lcntoroatnana
1.2-Olchlofoattiana
1.2-Otehtofoainana
T«trachloreatnana
Tduana K
, 1 , i •Trtcncfoatnana
Trfchtoroathana
Manganaaa
ft*
5.300
28JOO
NA
110.000
11.400
&280
17,500
A *MWft
9J20
48.000
NA
W
536
1.240
NA
20.000
114 b
840
175 b
«*.
b
21JOO
NA
0.4
OJ
0.1
0.1
0.1
0.1
ai
ai
A A
ao
1.1
193LO
0.8
0.8
0.1
ai
0.2
ai
0.2
0.1
2*
47812
7.5
13.6
QJ2
OJ
O.J
0^
0.4
0.2
A
-------
TABLE 10
GROUNDWATER CLEANUP LEVELS
Contaminant MCL
(ug/0
Acetone
Benzene 5
1.2-Oichloroethane 5
Manganese 50 (SMCL)
Tetrachloroethene 5
Toluene 1,000
1,1.1-Trichloroetnane 200
Trichloroetriene 5
Xylene 10.000
MCL3
(ug/i)
-
0
0
—
0
1,000
200
0
10,000
CLEANUP
Level
(ug/i)
3.500 (DWEL)
5
5
3,000 (NOAEL)
5
1,000
200
5
10,000
MCLG • Maximum Contaminant Level QoeJ
MCL • Maximum Contaminant Level
SMCL • Secondary MCL
DWEL - Drinking Water Equivalent Level calculated using tne
RfO following the procedure in EPA7540/G088-003
NOAEL - No Observed Adverse Effect Level calculated based
on a 70 kg adult consuming 2 liters of water per day
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TABLE 11
APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS (ARARS)
AND TO BE CONSIDERED MATERIAL (TBCs)
CHEM-SOLV, INC. SITE
ARARorTBC
L CHEMICAL SPBCinC
A. Water
1. Safe DrinUnf Water Act
a. MiHlm*"?* Contaminant
Leveb
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ARARorTBC
3. Health'Effectt
Assessment
4. State of Delaware
Regulations Governing
PubUc Drinking Water,
Revised May 19, 1989
S. Delaware Surface
Water Quality
SundanJofFeb.
1WO
g.Air
Clean Air Act
l.Nadonal Ambient Air
Quality Standards
i.
2 National Emissions
Standards for
Hazardous Air
Pollutants
Legal Citadon
Tide 16. § 122
§§9.3 (•)(!)
and 9.3 (b)(0
42 U.S.C 87401
40CFJLPanSO
40 GP.R Fait 61
Classification
To be
Gontidered
Relevant and
Appropriate
Applicable
Relevant and
Appropriate
Relevant and
Appropriate
Requirement
Synopsis
Non-enforceable toxitiiy
data for specific chemical*
for use In public health
•iiriimena. Abo to be considered
are Carcinogenic Potency Facton and
Reference DOM provided in the
Superfund PubUc Health Evaluation
Manual.
Sea criteria for public
drinking water supply. These
requirements are not directly
applicable since groundwater at the
site to used at a private drinking water
supply. However, under die
circumstances of this site, these
requirements are relevant and
appropriate.
Criteria are provided to maintain
surface water of satisfactory quality
consistent with public health and
recreational purposes, the propagation
and protection of fish and aquatic life,
and other beneficial uses of water.
National limitations on ambient
to protect public health and wdCue.
resulting from groundwater treatment
Standards promulgated for air
emissions from specific source
categories. Not applicable but may be
relevant and appropriate for emissions
from air strippers at Superfund sites.
Applicability to
Selected Remedy
To he mnsUend where n-nwdutl
alternatives address risk-based criteria
or standard setting for cleanup.
Remedial action must nmt tovrls
which are more stringent then
Federal MCU and non-iero MCLGs
Any surface water dlscharie must
meet lhc*e feveb tf more strinttnt
than federal reguladona.
Relevant and appropriate should
remedial action Include onsite air
stripper.
Air emissions from the air stripper
must meet the standard for benzene
-------
ARARorTBC
D LOCATION snonc
A. The Endangered
Specie* Act of 1978
B. The Archaeological
i and Historical
1974
•i
C Delaware Wetlands
Act afl973
D. Procedures for
Implemendng the
Requlremena of
the Coundl on
Environmental
Quality on the
National Environ-
mental Policy Act
B. Ground Water
Protection
Strategy of 1984
F. National Historic
Preservation Act of
1986
Legal Citation
I6U.S.C§IS3I
SO CF.R Part 402
16U5.C|469
Title 7, Delaware
Code. 0166k
16607
40C.F.RPart6
AppendiiA
EPA 440/6-84402
16U^.Cf§470ej
tea-
36 CF.R. Part 800
Classification
Applicable
Applicable
Applicable
Applicable
To be
Considered
Applicable
Requirement
Synopsis
Requires federal agenda to ensure
that any action authorized by an
agency b not likely to jeopardize the
or threatened spedei or adversely
affect in critical habitat.
Requiremenu relating to potential Ion
or destruction of significant scientific,
historical, or archaeological data
Revised June 29, 1984- Requires
activities that may adversely affect
wetlands In Delaware to be permitted.
Permits must be approved by the
county or municipality having
Jurisdiction.
EPAIi policy for carrying out the
provisions of Eiecudve Order 1 1990
(Protection of Wetlands). No activity
that adversely affects a wetland shall
be permitted if a practicable
alternative that has less effect Is
available. If there b no other
practical alternative, Impacts must be
mitigated.
Identifies ground water quality to be
achieved during remedial actions
based on aquifer characteristics and
use.
Requires remedial action to take into
account effects on properties included
In or eligible for the National Register
of Historic Places and to minimize
harm to National Historic Landmarks.
Applicability to
Selected Remedy
Potentially affected endangered
spedes have not been identified. The
remedial action will be implemented
so as not to adversely affect such
resources should any be identified in
the future.
Archaeological and historical
resources wul be Identified and
actions taken to mitigate any adverse
effects on those resources that would
result from Implementation of the
remedial action (e.g., construction of
an onsile treatment system).
Applies should discharge to surface
water affect wetlands.
Applicable should remediation involve
discharge to surface water.
The EPA aquifer classification will be
taken into consideration during
design and implementation of the
treatment remedy.
If the property b eligible for or
included on the National Register of
Historic Places, actions will be taken
to mitigate any advene effects that
would result from implementation of
the remedial action (e.g., construction
of an onsile treatment system).
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ARARorTBC
m. ACTON SHOPIC
A. Occupational Health
. and Safely Act
a Water
l.Oean Water Act
(CWA); National
Pollutant Discharge
Hlmliuttnn futtfmt
Requirement!
2. General Pretreatment
Regulations
4. Delaware
1 Environneotal Pro-
tection
4. Delaware Water
Quality Standanb
S. EPA Policy for Ground
Water Remediation at
Superfund Sin
6. Delaware River Basin
Gommlssfan Water
Quality
Legal Citadon
29 CP.R Parts
1904, 1910, and 1926
33 U.S.C 11251;
400FJLPM1122
40CF.RPart403
tide 7, Delaware
Code, Chapter 60
Section 6010
Stream Quality
Standard Section 10
OSWER Directive
9355.4-03
Memorandum of
Agreement
between the Delaware
River Basin
and the U.S.
Environmental
Protection Agency
Region III (§ U1.5 and
V.8)
Classification
Applicable
AppUcaUe
Applicable
Appuc^e
i
To be
Considered
Applicable
Requirement
Synopsis
Provides occupational safety and
health requirements for workers
engaged in onsite Odd activities
Enforceable standards for all
discharges to waters of the United
States.
Standards for discharge to POTW.
Regulations Governing the
Construction of Water Welb
Standards are established in order to
regulate die discharge Into state
waters In order to maintain the
Integrity of the water.
This policy recommends approaches to
ground water remediation using a
pump and treat system.
Regulate restoration, enhancement
and preservation of state waters.
Applicability 10
Selected Remedy
Applicable to onsite work performed
during Implementation of remedial
activities
-
Annlicahle should mnMlial action
Involve discharge to surface water.
Applicable for discharge of extracted
groundwater to POTW.
All wells will be installed and
maintained according to state
procedures for permitting,
construction, and abandonment.
Applicable since remediation involves
discharge to surface water.
This policy will be considered during
the ongoing implementation of the
remedial action.
AnJicahle if remedial •rtian InunliM
discharge of >50.000 gallons/day
average over any month or a
withdrawal of ground water of
100,000 gallons/day or more average
over any month.
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ARARorTBC
CAlr •
1. Delaware Regulation*
Governing (he Control
of Air Pollution
2. Control of Air
Emiitions from Air
Strippers at Superfund
Ground Water
Site* June IS, 1989
D. Hazardous Waste
1. United State*
Department of
Transportation Rules
for Transportation
of Hazardous
Materials
X Delaware Regulations
Governing Haiardoua
Waste
Clhe Solid Wane
Disposal Act (ROOD)
a. Standards Applicable
to Generators of
Hazardous Waste
b. Standards Applicable
to Transporters of
Haiardou* Waste
Legal Citation
7 Delaware Code,
Chapter 60, Section
6003, Regulation 2,
Section 2.4
OSWER Directive
9355.0-28
49 CFJl Paris 107,
and 171 .1-172.604
Delaware Regulations
Governing Hazardous
Waste
(42U£.C.|6901ei
f£L)
Delaware Regulations
Governing Haxardous
Waste, Part 262.10-58
(40 CFJt Part 26X10-
58)
Delaware Regulations
Governing Haxardous
Waste, Part 263
(40 CFJl Part 263)
Classification
Applicable
To be
Considered
Applieable
Applicable
Applicable
Applicable
Requirement
Synopsis
Sets forth the requirement that a
permit b necessary to operate an air
•tripper If emissions will exceed 2.5
uWday.
Policy |o guide the selection of
controls for air strippers at
groundwater sites according to the air
quality status of the site's location
fjLe, attainment or non-attainment
area).
Regulations for transport of hazardous
materials
Delaware Regulations Governing
Haxardous Waste Part 261 (40 C.F.R.
Part 261) define "hazardous waste".
Hie regulations listed below apply to
the handling of such hazardous waste.
hazardous wastes including waste
determination manifests and pre-
transport requirements.
Sen forth regulations for off-site
transporttn of hazardous waste in the
handling, transportation, and
management of the waste.
Applicability to
Selected Remedy
If emissions exceed 2.5 Ibsyday then
the substantive requirements of the
regulation must be met. In addition,
the emissions from the air stripper
must meet the Ambient- Air Quality
Standards set forth in Regulation 3 of
7 Delaware Code, Chapter 60, Section
6003.
To be considered In determining if air
emissions controls are necessary for
an air soipper. Sources most in need
of controls are those with emissions
rates In excess of 3 Ibsyhour or 15
Ibsyday or a potential rate of 10
tons/year of total VOCs.
Applicable to oflsite shipment of
process wastes.
The collected ground water,
treatment systems, and hazardous
wastes generated by the treatment
systems shall be handled In
accordance with regulations listed
below
Applies to wastes generated by the
groundwater treatment systems.
Apply to any company contracted to
transport hazardous material from
the site.
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ARARorTBC
c. Standards
for Owners and
Open ton of
Hazardous Wane
Treatment, Storage,
and Disposal
Fadlirk* (TSDF)
d. RCRA Requirements
for UK and
Containers
e. RCRA Requirements
for Tank* System*
f . RCRA Manifest
System, Record-
keeping, and
Reporting
g. RCRA Und Disposal
Restrictioni
Legal Citation
Delaware Regulation*
Governing Hazardous
Watte. Part 264
(40CFJlPart264)
Delaware Regulation
Governing Hazardou*
Waste, Put 264.170-
176
(40CP.RPut
264.170-17*)
Delaware Regulations
Governing Hazardou*
Watte. Put 264.190-
199
(40CF.RPUI
264.190-199)
Delaware Regulatkm*
Governing Haiaidom
Watte. Put 264.70.
264.73-75, and 264.77
(40 CPJ» Put 264.70,
264.79-75, and
264.77)
40CFJtPut266
dassification
Applicable
ApplkaMe
Applicable
Applicable
Requirement
Synopsi*
Reguladona for ownen and operator*
of TSDF* which define acceptable
management of hazardous wanes.
RequlronenlB for storage of hazardous
wade In storage containers.
Requirements for storage or treatment
Requirements for manifesting for
offsite disposal of hazardous wastes
Restriction* on land disposal of
hazardous wastes.
Applicability to
Selected Remedy
Applies to onslte recovery and
treatment systems and any facilities
to which wastes generated at the site
may be taken.
Applicable for ondte treatment
systems and temporary storage
containers.
Applicable for onslte treatment
system* and temporary storage tanks.
Applicable for ofbite disposal of
hazardous waste generated by
treatment systems.
Applicable for land disposal of
treatment process wastes.
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Table 12
Cost Summary
Capital
Alternative 1
No Action
Ground Water Monitoring
Alternative 2
Ground Water Monitoring
Ground Water Restriction Zone
Alternative 3
Ground Water Monitoring
Ground Water Restriction Zone
Alternate Water Supply
Alternative 4
Ground Water Monitoring
Ground Water Restriction Zone
Alternate Water Supply
Ground Water Collection
Direct Discharge to POTW
Alternatives
Ground Water Monitoring
Ground Water Restriction Zone
Alternate Water Supply
Ground Water Cofectton
Onsite Treatment
Discharge to Surface Water
$13,500
$18,500
$30,500-
$34,500
Annual
O&M
$25,000-
$81,000
$25,000-
$81,000
$25,000-
$84,000
Present
Worth
$385,000
$391,000
$410,000-
$431.000
$110,000- $57,000- $660,000-
$234,000 $148,000 $686,000
$181,000. $148,000- $687,000-
$185.000 $189,000 $688,000
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