United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R03-91/115
June 1991
&EPA Superfund
Record of Decision
Halby Chemical, DE
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90272-101
| REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA/ROD/R03-91/115
3. Recipient1* Acceeaion No.
Tree and Subtitle
SUPERFUND RECORD OF DECISION
Halby Chemical, DE
First Remedial Action
5. Report Date
06/28/91
. 7. Aut>or(«)
8. Performing Organization Rept No.
9. Performing Organization Nun* and Addrea*
10. Pro|*ct/Ta*k/Work Unit No.
11. Contr*c loBntincrft/Open-Lnovd Tcmu
c. COSATI Reid/Group
;. AvaUabiity Statement
19. Security Ctau (Thl* Report)
None
20. Security Claa* (Thi* Page)
None
21. No. of Page*
120
22. Price
(See ANSI-Z39.18)
See Instruction* on Revere*
(Formerly NTIS-35)
Department of Commerce
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EPA/ROD/R03-91/115
Halby Chemical, DE
'irst Remedial Action
Abstract (Continued)
the State and EPA beginning in 1983, which identified leaking drums and stained soil.
Analyses of samples taken during this site investigation revealed VOCs, organics, metals,
and other carcinogenic compounds in the soil. This Record of Decision (ROD) addresses
the first of two operable units (OUs) and provides a final remedy for soil and debris in
the process plant area. Contamination of air, surface water, ground water, and sediment
in the marsh and lagoon areas will be addressed in a subsequent ROD as OU2. The primary
contaminants of concern affecting the soil and debris are VOCs including benzene, TCE,
toluene, and xylenes; other organics including PAHs; and metals including arsenic,
chromium, and lead.
The selected remedial action for this site includes consolidating debris onsite or
disposing of all debris offsite; excavating and stabilizing the top 6 inches of
approximately 10,300 cubic yards of contaminated surface soil in the process plant area,
followed by replacing the stabilized soil onsite; capping the approximately 5,800 square
yards residuals area with an asphalt cap; conducting soil monitoring; and implementing
institutional controls including deed restrictions. The estimated present worth cost for
this remedial action is $1,586,000, which includes an annual O&M cost of $43,000.
PERFORMANCE STANDARDS OR GOALS: The clean-up goals for soil contaminants including
arsenic and carcinogenic PAHs are set at background levels. Additional sampling and
analysis is required to ascertain background levels; however, approximate goals include
arsenic 10 mg/kg and PAHs 1.2 mg/kg.
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REGION III, EPA
PHILADELPHIA, PA
RECORD OF DECISION
FOR THE HALBY CHEMICAL SITE
NEW CASTLE COUNTY, DELAWARE
June 1991
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TABLE OF CONTENTS
Page
DECLARATION FOR RECORD OF DECISION 1
DECISION SUMMARY 4
Site Name, Location, and Description 4
Site History and Enforcement Activities 10
Highlights of Community Participation 13
Scope and Role of Operable Unit 13
Summary of Site Characteristics 14
Summary of Site Risks 26
Description of Alternatives 38
Summary of Comparative Analysis of Alternatives 58
Selected Remedy. 63
Statutory Determinations 67
Documentation of Significant Changes 72
RESPONSIVENESS SUMMARY 74
APPENDIX It Description of Evaluation Criteria
APPENDIX II: Index of the Administrative Record
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DECLARATION
FOR
RECORD OF DECISION
SITE NAME AND LOCATION
Halby Chemical Site
Wilmington, New Castle County, Delaware
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action
for Operable Unit 1 of the Halby Chemical Site, New Castle
County, Delaware, developed in accordance with the requirements
of the Comprehensive Environmental Response, Compensation and
Liability Act of 1980 (CERCLA), as amended by the Superfund
Amendments and Reauthorization Act of 1986 (SARA) and, to the
extent practicable, the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP). This decision document
explains the factual and legal basis for selecting the remedy for
Operable Unit 1 for this site.
The State of Delaware concurs in the remedy selected by the
Environmental Protection Agency (EPA). This decision is based on
the Administrative Record for this site. An index of the
Administrative Record upon which the selection of the remedial
action is based is attached as Appendix II.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from
this site, if not addressed by implementing the response action
selected in this Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare,
or the environment.
DESCRIPTION OF THE SELECTED REMEDY
*
This operable unit is the first of two operable units for
the Halby Chemical Site. Operable Unit 1 (OU1) for the site
addresses the principal threat posed by soil contamination within
the process plant area of the site. Operable Unit 2 (OU2) for
the site will address contamination of the air, groundwater,
sediments in the outfall area and tidal marsh area, and sediments
and surface water within the lagoon and drainage ditch. The soil
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inside the process plant area (OU1) poses an unacceptable health
risk to workers because of the potential for direct contact,
ingestion, or inhalation of contaminated soil. The selected
remedy involves the excavation of the top 6 inches of
contaminated surface soil in the process plant area followed by
stabilization and replacement. An asphalt cap is to be placed
over the stabilized material.
The major components of the selected remedy includes the
following:
1. Consolidate all debris on-site into one area
2. Perform a soil grid sampling activity to determine
the extent of remediation within the process plant
area
3. Perform a treatability study to identify a proper
stabilization formula
4. Excavate the top 6 inches of contaminated surface
soil
5. Stabilize excavated soil
6. Backfill stabilized soil
7. Cover the stabilized soil with an asphalt cap
8. Implement deed restrictions and public education
programs
9. Perform long-term monitoring and maintenance.
STATUTORY DETERMINATIONS
The selected remedy for OU1 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. By stabilizing the
contaminated surface soils within the process plant area, this
remedy satisfies the statutory preference for remedies that
employ treatment that reduce toxicity, mobility, or volume as a
principal element and utilize permanent solutions and alternative
treatment technologies to the maximum extent practicable.
However, because treatment of the subsurface soils within
the process plant area was not found to be practicable, the
selected remedy will result in hazardous substances remaining on-
site above health-based levels. Consequently, a review will be
conducted within five years after commencement of remedial action
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to ensure that the remedy continues to provide adequate
protection of human health and the environment. A separate
Proposed Plan and Record of Decision will be issued when the
studies associated with OU2 are completed.
UNITED STATES ENVIRONMENTAL
PROTECTION AGENCY
Edwin B. Erickson
Regional Administrator
Region III
Date
"The State of Delaware concurs
in the remedy selected by EPA"
.7Z.
Zdwin H. Clark Tl, Secrelfary
Department of Natural Resources and
Environmental Control
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DECISION SUMMARY
1. SITE NAME, LOCATION AND DESCRIPTION
The Halby Chemical Site presently owned by the Brandywine
Chemical Company consists of approximately 14 acres of land in
Wilmington, New Castle County, Delaware. Located in a highly
industrialized area near the Port of Wilmington, the site is bordered
to the northeast, northwest, and south by the Conrail Railroad,
Interstate 495, and Terminal Avenue, respectively. Figure i shows
the location and approximate property boundaries of the Halby
Chemical Site. Located in an area zoned industrial, the Halby
Chemical Site primarily has been used for heavy industry.
a. Site Description - Major site features are shown on Figure 2 and
include the following areas. The fenced area in the southeastern
corner of the site constitutes the former Halby Chemical Plant
(hereinafter, referred to as the process plant area). Major
components within the fenced area include wastewater/runoff
conveyance system, buildings, 37 tanks, drums, machinery, and a
railroad spur. There are no known underground storage tanks on-
site. As indicated on Figure 2, the buildings include: l) a large
three-story steel structure that housed the chemical plant; and 2)
three story split level brick building containing office space, a
machine shop, a motor storage room, a warehouse for chemical drums, a
file storage area, and a boiler room annex. The steel structure
consists of dilapidated structural members, inactive reactors, and
exposed piping. There are 23 horizontal tanks and 14 vertical tanks
on-site. These tanks were used to store bulk chemicals including
ammonium thiocyanate, sulfuric acid, caustic solutions, acetic acid,
isopropyl alcohol, sodium disulfide and toluene.
Large quantities of drums and containers are present on-site. A
1987 photographic analysis conducted by the Environmental Photo-
graphic Interpretation Center of the Environmental Protection Agency
(EPA) reported approximately 684 drums on-site. Labels on drums and
other containers on-site indicate the drums contain the following
substances:
acetone
ammonia thiocyanate
1-butanol
1-ethyl acetate
ethylene glycol
isopropanol 99
methanol
toluene
xylene
aromatic 100
germicidal solvent degreaser
odorless mineral spirits
caustic soda
sodium bicarbonate
methylene chloride
perchloroethylene (or tetrachloroethylene)
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X/fl
N
/\
HALBY CHEMICAL
FIGURE 1
SITE LOCATION MAP
Some*: U3GS 7,5 mlnul* Quadnngte Map (Wllmlnglon South) sc*u i H.*M
REMEDIAL MVESTKUTON M» FEASMLfTY STUDY («*S)
HALBV CHEMICAL SHE, NEW CASTLE COUNTY. DELAWARE
North
AEPCO
EPA CMMd N*. UMJt*
EPA W*«h
N*.
Mo. 1(01 SM
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CICCTMC CAM TOWtN TWtnt
VtNnCAtTAiM
HOMMMM|.fAM(
CHUSMCO 30*
cmvrwt
OflAMAOC TRENCH
- NMUHMOTMOn
1-495
RUNOFF
DITCH
CM.WNT
NUIMNUMMMANM
APPROXIMATE
PLANT OUTFALL
LOCATION
TRAILER/
HOUSES/
PLANT
DRAINAGE
' DITCH
/WAREHOUSE
TIDAL
MARSH
tOBOeiL CANAt
HALBY
CHEMICAL
PLANT
FIGURE 2
SITE LAYOUT AND PHYSICAL FEATURES
BRICK
BUILDING
STEEL
STRUCTURE
HALBY CHEMICAL SITE FEASIBILITY !
NEW CASTLE COUNTY. DELAWAt
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According to the facility owner, these drums are clean drums
containing the chemicals to be distributed to end users. Bulk
chemicals are shipped to the site via rail or trucks and stored in
tanks outdoors. The chemicals are later dispensed into the fresh
drums. Drums that are awaiting shipment to clients are either stored
in the warehouse building or outdoors in the fenced area.
A drainage ditch originates at the rear of the process plant
area and flows northwest to a lagoon. The lagoon is breached along
the northwest bank causing a direct hydraulic connection with the
drainage ditch which parallels 1-495. The 1-495 drainage ditch
directs surface runoff from the highway to the Christina River. Due
to their direct hydraulic connection with the Christina River both
the ditch and lagoon are under tidal influence. Water levels in the
lagoon fluctuated to 3 feet with each tidal cycle. An access road
is situated between the 1-495 drainage ditch and the highway. A
warehouse (identified as 3 on Figure 2) is located immediately
northwest of the process plant area which presently houses several
automobile repair businesses. Areas north and west of this warehouse
are used for storage of tractor trailers, cars, railroad cars,
trolley cars and other miscellaneous machinery. A drainage trench
flowing northeast-southwest bisects the site. The process plant
area, warehouse and storage areas, as discussed above, are located
east of the trench. The area west of the trench excluding the lagoon
and drainage ditch have been filled raising the grade several feet
above the area east of the trench. Primary features west of the
drainage trench include a tire repair business housed in a small
trailer (4), a truck stop (5) which includes two filling islands and
a small office, and a large warehouse (6) used to store steel. The
areas north and east of the warehouse are also utilized for steel
storage. Both the warehouse and filling area appear to straddle the
property line.
Off-site areas, which are indicated on Figure 2, include the
following:
Area 7 is a residential area consisting of three small house
trailers.
Area 8 consists of an asphalt plant, restaurant, and other
miscellaneous businesses.
Area 9 is utilized by the Delaware Department of
Transportation for equipment and materials storage. «,
Area 10 is situated northwest of the site on the opposite side
of 1-495. This area is utilized by a local contractor to
store salt between unloading from the Port of Wilmington
marine terminal (located 0.5 miles east of the site) and its
final destination.
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Area 11 is situated north and northeast of the site on the
opposite side of the Conrail Railroad tracks. The area is
utilized by the same contractor mentioned above for storage of
petroleum coke. The coke is stored in this area prior to
shipment from the Port of Wilmington to overseas destinations.
Area 12 is the tidal marsh which is located north and
northeast of the site between the railroad tracks and Area 11.
The tidal marsh is connected to the Delaware River via the
Lobdell Canal and the Christina River. The marsh fluctuates
2-3 feet over each tidal cycle. Historically, the on-site
lagoon was connected to the tidal marsh by a 30-inch .culvert
constructed under the railroad track. Field observations
indicate that the culvert is filled and crushed and therefore
is no longer a conduit for flow between the lagoon and tidal
marsh. However, the lagoon is hydraulically connected to the
Christina River via the 1-495 drainage ditch.
b. Geology - The Piedmont Uplands Section of the Piedmont
Physiographic Province and the Coastal Plain Physiographic Province
are present in New Castle County, Delaware. These two provinces are
separated by a boundary designated as the Fall Line, which is
situated approximately 1.25 miles north of the Halby Chemical Site.
The Piedmont Province is located north of the Fall Line, while
deposits of the Coastal Plain Province are south of this boundary.
The site is located within the Coastal Plain Physiographic Province]
approximately 1.25 miles south of the Fall Line. Based on reports
published by the Delaware Geological Survey, the depth to weathered
bedrock at this site is estimated to be approximately 100-150 feet.
In general, the lithology beneath the site consists of
unconsolidated sands, gravels, silts, and clays of the Columbia and
Potomac Formations and recent sediments, and weathered bedrock of the
Wilmington Complex. The Potomac Formation unconformably lies on the
weathered bedrock of the Wilmington Complex. The Cretaceous Age
Potomac Formation is the basal sedimentary unit of the Coastal Plain
sediments. The Potomac Formation is unconformably overlain by the
Pleistocene Age Columbia Formation which is exposed at the surface
except where overlain by the recent sediments'deposited by the
Christina and Delaware Rivers or fill material.
c. Soils - Soils within the process plant area and along the
southern portion of the 1-495 drainage ditch are mapped as the
Aldino-Keyport-Mattapex-Urban land complex (AM) according to*, the
United States Department of Agriculture Soil Survey, New Castle
County, Delaware. This complex consists of gently sloping Aldino,
Keyport, and Mattapex soils that have been disturbed for residential
and/or commercial purposes to a degree that mapping each distinct
soil type is impractical. Soils of the Aldino, Keyport and Mattapex
series are generally deep and moderately well drained. The mapped
soil types have been covered by a layer of fill material throughout
much of the site area. Extensive filling took place west of the QJ
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site drainage trench prior to construction of the truck stop and
warehouse.
d. Surface Water Hydrology - storm water runoff in the vicinity of
the site generally flows towards a drainage ditch which parallels I-
495 and discharges into the Christina River. The drainage divide is
roughly marked by the triangular perimeter of the site; that is, I-
495, the Conrail railroad tracks, and Terminal Avenue. The drainage
areas west of the railroad tracks, immediately north of the Halby
Chemical Plant, and on the southern side of 1-495 are all conveyed to
the drainage ditch. The United States Geologic Survey (USGS)
conducted an investigation of the relationship between the surface
water in the tidal marsh and shallow groundwater at the site;
Surface water and groundwater levels, tidal stage, and groundwater
temperature data were collected for approximately four weeks.
Findings of the USGS study indicate that no significant hydraulic
connection exists between the shallow aquifer and the adjacent tidal
water bodies at the site; this hydraulic connection will be
investigated further in Operable Unit 2 for this site.
e. Groundvater Hydrology - Local groundwater was encountered between
3 and 5 feet above mean sea level in both the Columbia and Upper
Potomac aquifers. Groundwater movement in the Columbia and Upper
Potomac aquifers is generally to the northeast and north-northwest,
respectively, toward the Christina River. The horizontal flow
gradient of the Columbia aquifer is approximately 0.002 or a 2-foot
vertical drop in water level for every 1000 feet horizontally. Both
aquifers are affected by local pumping of the Forbes Steel Well,
which is reportedly screened between 50 and 60 feet in the Upper
Potomac aquifer and produces approximately 6000 gallons of water per
day. Past reports have generally indicated a downward vertical flow
gradient between the Columbia and Upper Potomac aquifers, indicating
that groundwater would descend from the water table (Columbia)
aquifer to the deeper (Upper Potomac) aquifer.
Based on the RI findings there are three water bearing sands
beneath the site: upper and lower sands in the Potomac Formation and
the sands of the Columbia Formation. These sands are designated in
this document as the Upper and Lower Potomac aquifers and Columbia
aquifer, respectively. The Columbia and uppermost Potomac aquifers
in the Port of Wilmington including the Halby Chemical site and its
vicinity are not viable sources of water supply. The groundwater in
this area will be investigated further as part of Operable Unit 2 for
this site. However, the hazardous constituents found in the
groundwater during the RI are not the only reason that the aquifer is
not a viable future source of water supply. Other reasons include
inadequate yield, potential for brackish water intrusion, and man-
made contamination. Removal of the contaminants from groundwater
beneath the Halby Site would therefore have little impact on the
likelihood that groundwater in this area would be used for water
supply purposes. Public water is currently available to the
population in this area.
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2. BITB HISTORY AMD ENFORCEMENT ACTIVITIES
a. Bite History - From 1948 to 1977, sulfur compounds were produced
at the Halby Chemical Site. The three principal products produced
were ammonium thiocyanate, ammonium thioglycolate and isooctyl
thioglycolate. Other products and by-products included ammonium
sulfide, sodium sulfide, sodium thiocyanate, sodium hydrosulfide,
potassium thiocyanate, and monoethanolamine thioglycolate.
From 1948 to 1964, all liquids from the Halby Chemical Plant
flowed into the adjacent marsh (or lagoon). This unlined lagoon
drained via the marsh into the Lobdell Canal and from there into the
Christina River. The liquids from the site included cooling water,
surface water runoff and acid wastewater. According to one of the
site owners, the acid wastewater was at a pH between 3 and 6 and
contained:
* 7% sodium chloride * ferric chloride
* 15% sodium bisulfide * isopropyl ether
* ferrous sulfate * isooctyl alcohol
The acid wastewater flow from the plant was 6 to 7 gallons per
minute (gpm). In the early 1960s, the acid wastewater was discharged
into a pit, filled with limestone rocks, which partially neutralized
it prior to its discharge into the lagoon.
From 1964 to 1972, the acid wastewater was discharged to public
(county) sewers and, reportedly, only cooling water entered the
lagoon. In 1972, Halby Chemical Company merged with and became a
part of the Argus Chemical Company, a wholly-owned subsidiary of the
Witco Corporation. Witco assumed control of the plant and began
experimenting with wastewater treatment schemes. By 1975, Witco was
periodically diverting the acid wastewater flow from the county sewer
system to its pilot plant. The treated wastewater was discharged to
the lagoon. A National Pollutant Discharge Elimination System
(NPDES) permit was issued to Halby Chemical Company on July 1, 1977
to regulate discharges from the lagoon, which included cooling water
and effluent from the process plant wastewater treatment plant, to
nearby receiving waters (Lobdell Canal). The -permit regulated pH,
total suspended solids, Biological Oxygen Demand (BOD) and Chemical
Oxygen Demand (COD) in the lagoon effluent.
The plant closed in August 1977 and the property was sold to
Brandywine Chemical Company which receives bulk chemicals atvthe site
and distributes them to end users. At some time between May 1977 and
June 1983, the northwest bank of the lagoon was breached and the
lagoon now drains through the drainage ditch along 1-495 to the
Christina River with tidal fluctuations.
According to property title records, a portion of the site (until
1969) and the adjacent properties (until 1974) were owned by the
Pyrites Company. This company used the property to store pyrite or.
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Pyrite ore is an iron sulfide (FeS2) . Arsenic often replaces a
sulfide molecule in the pyrite structure to form arsenopyrite (FeAsS)
and the pyrite stored on the property reportedly contained arsenic.
The Pyrites Company removed iron from the ore and made sulfuric acid.
A portion of the adjacent properties is now used to store petroleum
coke and coal.
b. Previous Investigations - The area surrounding and including the
Halby Chemical Site has been the focus of several investigations by
EPA, the State of Delaware's Department of Natural Resources and
Environmental Control (DNREC), and the City of Wilmington. A
principal source of background information on the site is the NUS
Corporation's Site Inspection Report of the Halby Chemical Company,
completed under a contract with EPA on January 10, 1986.
The Delaware DNREC, in December 1983, prepared a Preliminary
Assessment of the Halby Chemical Site under the Emergency and
Remedial Response Information System (ERRIS). In February 1985, a
Preliminary Hydrogeologic Investigation at the salt piles along
1-495 was also prepared by the DNREC. The City of Wilmington
commissioned a geotechnical investigation of the 1-495 bulk storage
area. The report for this investigation was prepared in August,
1986. According to the 1983 Delaware DNREC Preliminary Assessment,
nearby residents had complained about lagoon overflow, hydrogen
sulfide-like odors in the vicinity of the site, and numerous spills.
In March 1984, an EPA FIT III Team performed a Site Inspection
(SI) of the facility. Odors were emanating from sediment samples
taken from the on-site lagoon. Numerous drums and tanks were
observed to be stored on the site. The soil around the drums was
stained and several drums appeared to be leaking. A sample of the
stained soil was taken. Analytical results for the samples collected
during the SI showed high levels of the following organic and
inorganic compounds:
acetone naphthalene
benzene chrysene
ethylbenzene benzo(c)anthranthene
chloroform acenaphthene
1,1,-dichloroethane indeno(1,2,3,-cd)pyrene
1,1,1,-trichloroethane carbon disulfide
trichloroethylene (TCE) arsenic
tetrachloroethylene (PCE) chromium
total xylenes cyanide «
2-butanone mercury
4-methyl, 2-pentanone lead
fluoranthene
Migration from the site was evident in aqueous and sediment
samples from the lagoon outfall, which contained elevated levels of
various pollutants. Only one of three water supply wells located on-
site was operational at the time of the inspection. This well showed
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high levels of arsenic, mercury, cyanide, and TCE. The on-site wells
were used for cooling water supply and not for potable water. The
presence of these substances suggested that the groundwater
underlying the site was contaminated.
In March 1985, EPA resampled the on-site production well. These
samples were analyzed for thiocyanate compounds by a wet chemistry
method. The results indicated that most of the cyanide discovered
during the March 1984 sampling was actually thiocyanate, a compound
that was manufactured at the facility.
In a City of Wilmington study of the bulk storage area \
immediately adjacent to the Halby Chemical Site, it was observed that
the groundwater beneath this site was contaminated with various
inorganic and organic constituents. In particular, national interim
primary and secondary drinking water standards were exceeded for the
following inorganics: chloride, sulfide, cyanide, arsenic, cadmium,
selenium, and zinc. Analysis for priority pollutant organic
compounds indicated the presence of low levels of two volatile
organics which included toluene and trans-l,2-dichloroethene.
Volatile compounds detected during the sampling and which are not on
the EPA's priority pollutant list included 2,2-oxybis-propane,
tetrahydrofuran, and acetone. The latter two were found in trace
amounts and regarded as related to sampling analysis procedures and
well construction. In addition, three unlisted base/neutral
extractable organics were detected.
Several heavy metals were also identified in the City's study.
These included arsenic, cadmium, cobalt, iron, manganese, nickel,
selenium, strontium, and zinc. The presence of cobalt, nickel, and
strontium, and the high concentrations of surfactants suggest that
the storage of petroleum coke at the area adjacent to the Halby
Chemical Site may also have contributed to the contamination of
groundwater at the site.
Based on the Delaware DNREC study conducted on the salt piles
along 1-495, it was concluded that leachate from the salt piles had
also contaminated the groundwater locally and posed a threat to the
use of the aquifer for most water supply purposes, including public
drinking water. Analyses of groundwater quality samples taken during
this study indicated high levels of iron and manganese in every well.
Sulfates were also found in high concentrations and it is speculated
that these contaminant levels could be related to coal or slag piles
that may have existed at or near the site in the past. Highvsulfate
concentrations along with high iron and low pH are consistent with
the presence of water leached through coal. Sodium and chloride were
both found in high concentrations in various wells. Therefore, an
additional potential source of groundwater contamination is
associated with the salt piles on the opposite side of 1-495.
There is also the possibility that the former operation of North
American Smelting, a lead smelter plant which was located
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approximately 1,000 feet west of the site may have contributed at
least a portion of the lead and arsenic identified in surface soil
and lagoon sediment samples in the area.
c. Enforcement Activities - EPA has identified the following
potentially responsible parties (PRPs) associated with the Site:
Argus Chemical Corporation, as the successor to Halby Chemical Co.,
Inc.; Witco Corporation, as the parent corporation to Argus Chemical
Corporation; and Brandywine Chemical Company as the owner and
operator of the site from 1977 to the present.
On April 17, 1986 the aforementioned PRPs received Special Notice
Letters inviting them to perform the Remedial Investigation/
Feasibility Study (RI/FS) Report. Brandywine, Argus and Witco
declined to conduct the RI/FS, and the RI/FS was performed with
Superfund monies. After the completion of the RI, Witco offered to
do the FS. The Agency declined the offer, as it contravenes EPA's
policy to split the RI/FS process. In addition, a change in
contractors would have delayed the completion of the FS and the
issuance of the ROD.
3. HIGHLIGHTS OF COMMUNITY PARTICIPATION
Pursuant to CERCLA SS 113(K)(2)(B)(i-v) and 117, the RI/FS Report
and the Proposed Plan for the Halby Chemical Site were released to
the public for comment on April 19, 1991. These two documents were
made available to the public in the administrative record located in
an information repository maintained at the EPA Docket Room in Region
III and at the Wilmington Institute Library in Wilmington, Delaware.
The notice of availability for these documents was published in The
News Journal on April 19, 1991. A public comment period on the
documents was held from April 19, 1991, to June 3, 1991. In
addition, a public meeting was held on May 2, 1991. At this meeting,
representatives from EPA answered questions about problems at the
site and the remedial alternatives under consideration. A response
to the comments received during the public comment period is included
in the Responsiveness Summary, which is part of this Record of
Decision (ROD).
4. SCOPE AND ROLB OP OPERABLE UNIT
As with many Superfund sites, the problems at the Halby Chemical
Site are complex. As a result, EPA has organized the remedial work
into two Operable Units. The scope of both of the Operable Units can
be summarized as follows:
Operable Unit 1: Contamination of soils inside the process
plant area.
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Operable Unit 2: Contamination of the air, groundwater,
sediments in the outfall area adjacent to the process plant,
sediments in the area east of the Halby property which
includes the tidal marsh area, and sediments and surface water
within the lagoon and adjacent ditch next to the process
plant.
This ROD addresses Operable Unit I at the site. The contaminated
soil inside the process plant area was determined to be the principal
threat at the site due to the potential for direct contact health
risks to on-site workers. The remedial action objective for Operable
Unit 1 is to prevent current and future exposure to contaminated
soils in the process plant area at the Halby Chemical Site.
Further investigations will be conducted concerning the
groundwater, air releases, sediment in the outfall area adjacent to
the process plant, the area east of the Halby property including the
tidal marsh area, and sediments and surface water located within the
lagoon and drainage ditch next to the process plant. A separate
Proposed Plan and ROD will be issued when the studies associated with
Operable Unit 2 are completed.
5. SUMMARY OP SITE CHARACTERISTICS
The soil at the process plant area poses unacceptable health
risks to workers due to the potential for direct contact, ingestion,
or inhalation of contaminated soil. Up to 10,300 cubic yards of
contaminated sediment could require remediation. There were no
discernible waste piles, impoundments, or containers/drum storage
areas visible in the process plant area during the initial site
reconnaissance for the RI/FS. Existing tanks and containers on-site
are used to store raw chemicals but not wastes. Thirteen soil
sampling stations were located within the process plant area during
Phase I and II sampling (Figure 3). Soil samples were collected from
areas around storage tanks or stained soil within the process plant
area.
a. TCL Metals - The 17 metals identified in the process plant area
at concentrations exceeding twice the background level are shown in
Table 1. Arsenic, lead and zinc concentrations are also shown in
Figure 4. The most significant metals identified within the process
plant area are discussed below. Arsenic was identified at 11 of the
13 sampling locations within the process plant area. Elevated
concentrations were identified at stations SSS-09 (1,130 mg/kg) and
SSS-25A (1,700 mg/kg), which are situated north of the railroad spur
track. These locations are separated by sampling station SSS-10,
which showed a concentration of 74.1 mg/kg. Arsenic levels
identified at other locations within the process plant area are
commonly in the 30-80 mg/kg range, even at depth (SSS-23). Thus, the
elevated concentrations at SSS-09 and SSS-25 may be associated with
spills.
14
-------
Ul
LEGEND:
H ELECTRIC CABLE TOWCR TRESTLE
FENCING
VERTICAL TANKS
HORIZONTAL TANKS
DRAINAGE TRENCH
RAILROAD TRACKS
BLOC. FOOT PRINT
SURFIQAL SOIL SAMPLING STATION
0SSS-08
COKE
HALBY
CHEMICAL
SITE
SSS-16
SSS-24
TIDAL
MARSH
SSS-04
SUM
/SSS-25
SS-1
SSS-03
SSS-10
SSS-02
SSS-09
SSS-19
SS-23
SSS-11
SSS-12
SSS-22
FIGURE 3
SURFICIAL SOIL SAMPLING LOCATIONS
REMEDIAL INVESTIGATION It FEASIBILITY STUDY (RI/TS)
HALBY 'CHEMICAL SITE. NEW CASTLE COUNTY. DELAWARE
sss-u
SSS-21
EPA CONTRACT NO. 68-01-7250
CPA WORK ASSICNUCNT NO 119-3117
EBASCO SUBCONTRACT NO
-------
TABLE 1
METAL CONCENTRATIONS - PROCESS PLANT AREA
HALBY CHEMICAL SITE
**
***
***
***
***
PARAMETERS
ARSENIC
IARIUM
RERVUIUN
CADMIUM
CALCIUM
CHROMIUM
COBALT
COPPER
IKON
LEAD
MANGANESE
MERCURY
NICKEL
SELENIUM
SILVER
SODIUM
ZINC
UNIT
g/kg
g/kg
V/kB
g/kg
g/kg
*g/kg
g/kg
g/kg
g/kg
g/kg
g/kg
ng/kg
g/kg
g/kg
g/kg
g/kg
g/kg
SSS-06*
2'0-
4.4
43.4
1.4
0.89
469
28. J
16.1
37.3
27500
16.5
359
0.11
13.7
0.83
0.86
42.5
81, A
SSS-06* SSS-01
2-0- 3-0"
4.4
63.4
1.4
0.89
469
28.3
16.3
37.3 315
27500
16.S 120
359
0.11 0.6S
13.7
0.83
0.86
42.5
81.6
SSS-09
0'3«
1130
143
7.1
7860
343
217
107000
400
9
42.3
559
1250
SSS-10
0-3"
74.1
150
1.9
1240
151
225
0.6
3.6
447
272
SSS-11
0«2»
36
7.1
1090
249
2
3
707
314
SSS-12 SSS-17
0'3« 0'3"
58.7 23.4
1760
76.8 1780
255 133
0.5 2
275
SSS-18
0'3"
57.7
199
3.8
5590
98.7
1470
65200
260
5.5
51.9
647
910
SSS-19
O'O"
107
393
3.1
86
3870
222
43
43.3
2.3
475
SSS-20 SSS-21A SSS-21B SSS-21C SSS-21D
O'O" 4'0« 6'0" B'O" 10-0"
36.4 50
9.5
3310
228
50
372
487000
443
2680
7.6
174
3270
Background tmpU.
** Carcinogen by both the ingestion and inhalation routes.
*** Carcinogen by inhalation route.
-------
TABLE 1 (cont)
METAL CONCENTRATIONS - PROCESS PLANT AREA
HALBY CHEMICAL SITE
**
***
ft**
***
***
PARAMETERS
ARSENIC
IARIUM
IERYUIUM
CADMIUM
CALCIUM
CHROMIUM
C06ALT
COPPER
IROH
LEAD
MANGANESE
MERCURT
NICKEL
SELENIUM
SILVER
SODIUM
ZINC
UNIT
g/kg
g/kg
g/kg
g/kg
g/kg
g/kg
ng/kg.
g/kg
ng/kg
ng/kg
ng/kg
ng/kg
ng/kg
ng/kg
g/kg
g/kg
g/kg
SSS-06* SSS-22A SSS-22* SSS-22C SSS-22D SSS-23A SSS-23B SSS-23C SSS-23D SSS-23E SSS-2SA SSS-258 SSS-2SC SSS-2SO SSS-2SE
2'0" 4'0" 6'0" 8'0" lO'O" 4'0" 5'0» 6'0" 8'0" 10*0" 4'0B 6'0" 8'0" 10'0" 12'0"
4.4 130 50 60 60 1700 S40 . 1300 490 140
63.4
1.4
0.89
469
28.3
16.3
37.3
27500
16. 5 200 200 100
359
0.11
13.7
0.83
0.86
42.5
81.6 260 2000 570 1200 470 220
ItckgromJ tanpU.
** Carcinogen by both the ingestion and inhalation routes.
*** Carcinogen by inhalation route.
-------
00
LEGEND:
H ELECTRIC CABLE TOWER TRESTLE
-~- FENCING
VERTICAL TANKS
HORIZONTAL TANKS
- DRAINAGE TRENCH
RAILROAD TRACKS
BLOC. FOOT PRINT
SURFICIAL SOIL SAMPLING STATION
FIGURE 4
PROCESS PLANT SOILS - ARSENIC. LEAD,
AND ZINC CONCENTRATIONS
REMEDIAL INVESTIGATION * FEASIBILITY STUDY (RJ/FS)
HALBY CHEMICAL SITE. NEW CASTLE COUNTY. DELAWARE
MORW
f>
ABI-Ct
EPA CONTRACT NO. 68-01-7250
EPA WORK ASSIGNMENT NO. 119-3LL7
EBASCO SUBCONTRACT, NO. 42.* '-005
AEPCO PROJCCT NO. 1023-5! '
-------
Within the vertical profile at SSS-25 (samples A-E), arsenic was
identified at an elevated concentration of 1,700 ing/kg at the 4-foot
level but declined with depth (see Table 1). SSS-25 shows the
attenuation of arsenic to be one order of magnitude in 8 feet of
vertical depth (1,700 to 140 mg/kg). SSS-09 contamination (1,130
rag/kg) is reported at a depth of 3 inches.
Copper concentrations were less than 400 mg/kg at all sampling
locations except SSS-17 (1,780 mg/kg), SSS-18 (1,470 mg/kg), and
SSS-19 (3,870 mg/kg). These sample locations are in the western part
of the process plant near its west gate (SSS-17), near the plant sump
adjacent to storage tanks (SSS-18), and the covered drain adjacent to
the railroad spur (SSS-19); and may be indicative of a spill during
the filling of a storage tank. Copper was not analyzed for during
the Phase II sampling.
Lead concentrations appear homogenous, ranging from 120-443
mg/kg. This element appears in 11 of the 13 process plant sampling
locations, and in all the near-surface Phase I samples. The highest
concentration is found at SSS-20, the lowest at SSS-01.
SSS-25 was the only sampling location at which significant
concentrations of lead were identified at more than one contiguous
depth. At a depth of 8 feet, lead was detected at a concentration of
200 mg/kg and at 10 feet at 100 mg/kg.
Zinc contamination closely parallels that of arsenic. It was
reported at significant levels in 9 of the 13 sampling locations in
the process plant area. Like arsenic, elevated concentrations of
zinc were identified at SSS-09 (1,250 mg/kg) and SSS-25 (2,000
mg/kg). Elevated concentrations of zinc were also identified at
SSS-18 (910 mg/kg) and SSS-20 (3,270 mg/kg). Zinc levels identified
at other locations within the process plant area are commonly in the
275-475 mg/kg range.
Vertical profiling at sample station SSS-25 using Phase II data
shows the highest zinc concentration of 2,000 mg/kg at the 4-foot
level and a decrease with depth to a low of 220 mg/kg at 12 feet.
b. Volatile Organic Compounds (VOCs) - The VOC contaminants found to
be present within the process plant are shown in Table 2 and in
Figure 5. Of the 14 VOCs identified within the process plant, carbon
disulfide and methylene chloride were the only two found throughout
the process plant area. These two VOCs were detected at nine of the
process plant sampling locations in concentrations of 12-66,900 and
21-6,600 ug/kg, respectively.
The highest concentration of carbon disulfide was identified at
SSS-25 (66,900 ug/kg) at a depth of 4 feet. Stations SSS-18 (58,000
ug/kg), SSS-17 (9,000 ug/kg), and SSS-10 (680 ug/kg), which are all
in the same area as SSS-25 in the northwestern section of the process
plant, also revealed elevated concentrations. This area represents
19
-------
TABLE 2
VOC CONCENTRATIONS - PROCESS PLANT AREA
HALBY CHEMICAL SITE
PARAMETER!
** NETHTLENE
CHLORIDE
ACETONE
CARBON
M DISUlFlOe
O 2-WJTANONE
TRICHLORO-
ETHENE
** IENZENE
4-NEWL-2-
PENTAHONE
2-HEXAHOHE
** TETRACHLORO
ETHENE
1.1.2,2-TETRA
CHLOROETHANE
TOLUENE
ETNTL BENZENE
STTRENE
TOTAL XTLENEI
UNIT
ug/kg
ug/kg
ug/kg
ug/kg
ug/kg
ug/kg
ug/kg
ug/kg
ug/kg
ug/kg
ug/kg
ug/kg
ug/kg
ug/kg
US-06* SSS-01
2-0- J'O-
NO 44
230
ND 18
27 170
HO
ND
NO
ND
NO '
HO
2 480
NO 56
NO
ND 490
SSS-09 SSS-10 SSS-11
0'3" O'J" 0'2"
120 130 24
3000
120 600
300
120 700
550
690
28
SSS-12 SSS-17 SSS-18 SSS-19 SSS-20 SSS-21A SSS-21B SSS-21C SSS-210
O'J" O'J" O'J" O'O" O'O" *'0" 6'0" 8'0" 10'0"
190 6600 25 21
6500
9000 58000 23 140
712 507
190
500
1200
3300 24.3 38.2
160
15
12 IB
Background SMpU.
** Carcinogen by both the ingestion and inhalation routes.
-------
TABLE 2 (cont)
VOC CONCENTRATIONS - PROCESS PLANT AREA
HALBY CHEMICAL SITE
PARAMETERS
** MEWLENE
CHIMIOE
ACETONE
CMION
oisuirioe
2-MJTANONE
TRICHUMO-
tTNENE
** IENZENE
4-M£THYl-2-
PENTANONE
2-NEXANONE
** TETRACMIORO
ETNENE
1.1,2.2-TETM
CNLMOETHANE
TOIUEHE
ETHTL BENIENE
STVRENE
TOTAL XTLENES
UNIT
UO/ka
ug/kg
U»/kg
ua/kg
ua/kg
ug/kg
ug/kg
ug/kg
ug/kg
ua/kg
u«/kg
uo/kg
ug/kg
ug/kg
SSS-06* SSS-22A SSS-22B SSS-22C SSS-22D SSS-23A SSS-23B SSS-23C SSS-230 SSS-23E SSS-2SA SSS-2SB SSS-2SC SSS-250 SSS-2SE
2'0» 4'0" 6'0» a'O- 10'0" *'0" 5'0" 6*0" 8'0" 10'0" 4'0" 6'0" 8'0" 10'0" 12'0"
NO 33.5 28.7
230 814 1520
NO 29.7 12. t 66900 130 12 212 34.0
27 370 180 182
NO
NO U2 24.2
NO 33.4
NO
NO
NO
2 87.2 23.3 10.S
NO
NO x
NO 14S.3 28.1 12.0
ckground Iwpla.
** Carcinogen by both the ingestion and inhalation routes.
-------
LEGEND:
ELECTRIC CABLE TOWER TRESTLE
FENCING
VERTICAL TANKS .
HORIZONTAL TANKS
-» DRAINAGE TRENCH
RAILROAD TRACKS
BLDG. FOOT PRINT
SURFICIAL SOIL SAMPLING STATION
FIGURE 5
PROCESS PLANT SOILS - VOC CONCENTRATIONS
REMEDIAL INVESTIGATION Ic FEASIBILITY STUDY (RI/FS)
HALBY CHEMICAL SITE. NEW CASTLE COUNTY. DELAWARE
EPA CONTRACT NO. 68-01-7250
EPA WORK ASSIGNMENT NO.
EBASCO SUBCONTRACT NO.
AEPCO PROJECT NO. 1023-
-------
the topographic low area within the process plant area. Vertical
profiling of station SSS-25 demonstrates a sharp decline in carbon
disulfide concentration with depth. The concentration dropped from
66,900 to 130 ug/kg from the 4-foot to the 6-foot depth interval.
The maximum concentration of methylene chloride (6,600 ug/kg) was
detected within the topographical low area, at SSS-18. Methylene
chloride was also detected at slightly elevated concentrations at
SSS-09 (120 ug/kg), SSS-10 (130 ug/kg), and SSS-17 (190 ug/kg).
Methylene chloride is a common laboratory contaminant and was
detected in the QC blank samples (26 ug/kg); thus, it cannot be
concluded that methylene chloride is a contaminant at a sampling
station if its concentration is less than 260 ug/kg. Phase II
samples show no data to suggest high levels at depth.
Trichloroethene (712 ug/kg), 1,1,2,2-tetrachloroethane
(28 ug/kg), ethyl benzene (56 ug/kg), and styrene (15 ug/kg) were
identified at only .one of the 13 sampling locations. Acetone
(1,520-6,500 ug/kg), 2-butanone (170-370 ug/kg), benzene (142-190
ug/kg), 4-methyl-2-pentanone (33.4-700 ug/kg), 2-hexanone (550-1200
ug/kg), tetrachloroethene (24.3-3,300 ug/kg), toluene (87.2-480
ug/kg), and total xylenes (12-490 ug/kg) were identified at four or
less sampling locations.
These VOCs were generally detected at the same sample locations
at which the elevated concentrations of carbon disulfide were
detected or at isolated sample locations along the railroad spur.
Acetone was detected in concentrations of 6,500 and 3,000 ug/kg,
respectively, at SSS-18 and SSS-10. It was not identified in any
other process plant sample, except at depth at station SSS-23. It
was detected in a concentration of 814 ug/kg in the 8-foot level and
1,520 ug/kg in the 10 foot level samples at this location. However,
acetone contamination cannot be confirmed at this location because
the detected concentration is less than 2,000 ug/kg (ten times the QC
blank concentration). Sample SSS-01 collected near the plant sump
indicated toluene and total xylenes contamination of approximately
500 ug/kg. The maximum concentration of tetrachloroethene (3,300
ug/kg) was also detected as SSS-18.
c. Semivolatile Organic Compounds (SVOCs) - SVOCs were evaluated as
potential site contaminants in the same manner as VOCs. The
resulting SVOC contaminants considered to be present within the
process plant are listed in Table 3. Combined carcinogenic
polycyclic aromatic hydrocarbon (CPAH) concentrations are shown in
Figure 6.
Of the 19 SVOCs detected, fluoranthene (85,000 ug/kg), indeno
(1,2,3-cd) pyrene (4,200 ug/kg), and benzo (g,h,i) perylene (5,000
ug/kg) were only identified at SSS-09, near the on-site railroad spur
line. Naphthalene (1,200 and 1,300 ug/kg), 2-methylnaphthalene
(2,200 and 2,800 ug/kg), acenaphthylene (27,000 and 1,900 ug/kg),
dibenzofuran (14,000 and 1,300 ug/kg), fluorene (20,000 and 700
ug/kg), phenanthrene (110,000 and 8,000 ug/kg), anthracene (19,000
23
-------
TABLE 3
SVOC CONCENTRATIONS - PROCESS PLANT AREA
HALBY CHEMICAL SITE
f\>
-P-
PARAMETERS
UNI?
SSS-06*
2-0-
SSS-01
3'0«
SSS-09
0'3»
SSS-10
0«3»
SSS-11
0'2«
SSS-12
0'3"
SSS-17
0«3"
SSS-18
0'3»
SSS-19
O'O"
SSS-20
O'O"
NAPHTHALENE
2-METNVL
NAPHTHALENE
ACENAPNTNVLENE
DIBENZOFURAN
FLUOftENE
PNENANTNRENE
ANTHRACENE
** DI-N-Mim
PNTHALATE
FLUCMANTHENE
PYRENE
** BUTVIBENZVL
PHTHALATE
** BENZOU)
ANTHRACENE
** CNRVSENE
** BIStf-ETNTLNEXYL)
PNTHALA1E
** KNZO(b>
FLUMANTNENE
** lENZO(k)
FLUMANTNENE
** KNZO(a)PYKNE
** INOENOd.2,
3-cd)PVRENE
ENZO(g.M)
^PERYLENE
ug/kg NO
ug/kg NO
ug/kg NO
ug/kg NO
ug/kg HO
ug/kg NO
ug/kg NO
ug/kg 40
ug/kg NO
ug/kg NO
ug/kg. NO
460
ug/kg
ug/kg
NO
NO
ug/kg 260
ug/kg
ug/kg
ug/kg
ug/kg
ug/kg
NO
NO
NO
NO
NO
1200
2200
27000
HOOO
20000
110000
19000
asooo
66000
19000
22000
12000
11000
7900
4200
5000
500
1700
1200
1300
2800
1900
1300
700
8000
1200
9000
4000
3800
1800
3900
2500
2100
1200
2100
2000 2300
2200
900
14000 24000 11000
Background sample.
** Carcinogenic PAHs
-------
COAL
ui
ICCCND:
ELECTRIC CABLE TOWER TRESTLE
FENCING
VERTICAL TANKS
HORIZONTAL TANKS
DRAINAGE TRENCH
RAILROAD TRACKS
BLOC. FOOT PRINT
SURFICIAL SOIL SAMPLING STATION
RGURE 6
CPAH CONCENTRATIONS
PROCESS PLANT SOILS
HALBY CHEMICAL SITE FEASIBILITY STUDY
NEW CASTLE COUNTY, DELAWARE
-------
and 1,200 ug/kg), pyrene (66,000 and 9,000 ug/kg), benzo(a)anthracene
(19,000 and 4,000 ug/kg), chrysene (22,000 and 3,800 ug/kg),
benzo(b)fluoranthene (12,000 and 3,900 ug/kg), benzo(k)flouranthene
(11,000 and 2,500 ug/kg), and benzo(a)pyrene (7,900 and 2,100 ug/kg)
were also detected at SSS-09 and near the gate at SSS-17,
respectively. Benzo(a)anthracene, chrysene, benzo(b)fluoranthene,
benzo(k)fluoranthene, benzo(a)pyrene, and indeno(1,2,3-cd)pyrene are
carcinogenic.
2-Methyl-naphthalene (1,200 ug/kg), phenanthrene (2,100 ug/kg),
and pyrene (2,200 ug/kg) were also detected as SSS-19. Bis(2-ethyl-
hexyl) phthalate was detected as SSS-19 as well, at a concentration
of 24,000 ug/kg. Di-n-butylphthalate (460 ug/kg) was the only SVOC
detected at SSS-01. At SSS-11, bis(2-ethylhexyl)phthalate (1,200
ug/kg) was the only SVOC detected. These two compounds were also
detected at SSS-10, in concentrations of 500 and 1,700 ug/kg and at
SSS-20 in concentrations of 2,300 and 11,000 ug/kg, respectively.
The SVOCs identified within the process plant area are not
considered to be wide-spread site contaminants because of their
isolated locations. Sixteen of the identified SVOCs (including six
carcinogenic compounds) were, however, identified at SSS-09; while
fourteen were identified at SSS-17. These areas may have experienced
localized spills.
d. Additional Parameters - Total cyanide, free cyanide, and
thiocyanate, were analyzed for during Phase I sampling. Phase II
samples were analyzed for thiocyanate only. Total cyanide was found
in the process plant area at stations SSS-09, SSS-11, and SSS-12 in
concentrations of 40, 15, and 35.1 mg/kg, respectively. These
stations are located adjacent to one another within the southern tank
area of the Plant. No associated in-plant free cyanide or
thiocyanate contamination was detected in Phase I samples.
6. SUMMARY OF SITE RISKS
A Risk Assessment was prepared by the Environmental Protection
Agency (EPA) to assess the potential health effects that may result
from exposure to contaminants within the process plant area of the
Halby Chemical Site (Operable Unit 1). The environmental risks
associated with exposure to the wastes found at the site are fully
evaluated in the Biological Assessment in the RI Report, Appendix E
of the FS, and in the Analytical Chemistry and Solid Phase Toxicity
Bioassay Report of April 1991. There are no risks to the environment
within the process plant area of the site. Areas where environmental
risks exist will be addressed in Operable Unit 2 for the site. All
of the referenced reports can be found in the Administrative Record
for the Halby Chemical Site. Based on the EPA risk assessment it has
been concluded that actual or threatened releases from Operable Unit
1, if not addressed by implementing the response action selected in
26
-------
this ROD, may present an imminent and substantial endangerment to
public health and welfare.
a. contaminant identification Information The media of concern in
Operable Unit 1 is soil contamination within the process plant area.
The concentration of the chemicals of concern on which the risk
assessment was based is the reasonably most exposed (RME)
concentration. The RME is a calculated level of contamination which
is the upper 95th percent of confidence level. The contaminants of
concern and their respective RME concentrations are presented in
Table 4. Mercury, nickel, zinc and carbon disulfide were initially
considered to be contaminants of concern, however, results of the
calculations for noncarcinogenic health threats support the decision
that they should not be considered further as shown in Table 7. They
were therefore eliminated from the list of contaminants of concern.
b. Exposure Assessment - As the primary current use of the site is
for industrial purposes, and the potential for site access by casual
trespassers is quite limited, the most likely potential route of
exposure under current conditions is exposure to the workers in the
course of their day-to-day activities. Current and future-use
exposure pathways for Operable Unit 1 are summarized as follows:
Exposure Pathway
Current Site Land Use
Ingestion of dusts and soils
containing arsenic and CPAHs
Inhalation of dusts and soils
containing arsenic, chromium
and CPAHs
Dermal absorption of CPAHs from
soils that adhere to the skin
Exposed Population(s)
Workers at Halby Site
Workers at Halby Site
Workers at Halby Site
2. Future Site Land Use (Construction Excavation)
Ingestion of dusts and soils
containing arsenic
Inhalation of dusts and soils
containing arsenic
Workers at Halby Site
Workers at Halby Site
It is expected that onsite workers may experience direct contact
with surface and shallow subsurface soil as part of their normal
duties. Activities which would involve such exposures could include
grading, maintenance and normal housekeeping activities. Exposures
could be both through direct dermal contact and incidental ingestion
27
-------
Table 4
CONTAMINANTS OF CONCERN
IN PROCESS PLANT AREA (001)
HALBY CHEMICAL SITE
INORGANICS RME
Arsenic . ........................... 412
64ft ...... .................. 872
§ 6 ft ........................ 282
§ 10 ft ....................... 265
Chromium ............................ 170
ORGANIC8
Pyrene 17,861
Benzo (a) anthracene 5,334
Chrysene 6,051
Benzo (b)fluoranthene 3,597
Benzo (k) f luoranthene 3,155
Benzo(a)pyrene 2,337
28
-------
occurring due to such activities as smoking or eating at the site
without washing soiled hands.
Since the majority of the site is not vegetated, it is to be
expected that airborne particulates will be generated due to the
action of wind, excavation and construction activities (future use
scenario), and surface disturbance by vehicles. Inhalation of
airborne particulates by onsite workers is therefore likely to occur.
Inhalation of site-associated particulates is less likely to be
significant for off-site receptors (residents) because of the
distances to the nearest residences, and obstacles between the site
and the residences (the cement works and the 1-495 embankment) that
would increase the rate of particle deposition.
To calculate the risks to on-site workers at the Halby Chemical
Site certain exposure assumptions were made based on human activity
patterns. Assumptions common to all evaluated scenarios are the
human lifetime set at 70 years, body weight set at 70 kg, exposure
frequency set at 250 events/year and the averaging time set at 25,550
days in 70 years. Other assumptions for each exposure scenario are
as follows.
INGESTION
Amount of Soil Ingested per day = 50 mg
Exposure Duration
=25 years under the current use scenario
= 1 year under the future use scenario
INHALATION
Inhalation Rate - 0.83 m /hr
Exposure Time = 8 hrs/day
Exposure Duration
- 25 years under the current use scenario
= 1 year under the future use scenario
DERMAL CONTACT
Skin Surface Area in Contact = 3,120 cm /event
Soil to Skin Adherence Factor = 1.45 mg/cm
Exposure Duration - 25 years
The Cowherd Model was used in calculating risks present in the
inhalation pathway of exposure. A brief summary of assumptions used
in this model are as follows:
Models the transport of respirable particles; *
Assumes that the contamination is distributed uniformly over
the facility;
Employs dispersion modeling that accounts for concentrations
at the breathing height;
Makes steady state assumptions indicating that the
contaminant source is never depleted; and
29
-------
Concentration of contaminants in the respirable particles i:
the same as that of the bulk phase soils.
c. Toxicity Assessment - Cancer potency factors (CPFs) have been
developed by EPA's Carcinogenic Assessment Group for estimating
excess lifetime cancer risks associated with exposure to potentially
carcinogenic chemicals (Table 5). CPFs, which are expressed in units
of (mg/kg-day) "1, are multiplied by the estimated intake of a
potential carcinogen, in mg/kg-day, to provide an upper-bound
estimate of the excess lifetime cancer risk associated with exposure
at that intake level. The term "upper bound" reflects the
conservative estimate of the risks calculated from the 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.
Reference doses (RfDs) have been developed by EPA for indicating
the potential for adverse health effects from exposure to chemicals
exhibiting noncarcinogenic effects (Table 5). RfDs, which are
expressed in units of mg/kg-day, are estimates of lifetime daily
exposure levels for humans, including sensitive individuals, that is
not likely to be without an appreciable risk of adverse health
effects. Estimated intakes of chemicals from environmental media
(e.g., the amount of a chemical ingested from contaminated drinking
water) can be compared to the RfD. RfDs are derived from human
epidemiological studies or animal studies to which uncertainty
factors have been applied (e.g., to account for the use of animal
data to predict effects on humans). These uncertainty factors help
ensure that the RfDs will not underestimate the potential for adverse
noncarcinogenic effects to occur.
d. Risk Characterization Binnmarv
Cancer Risks - Excess lifetime cancer risks are determined by
multiplying the intake level with the cancer potency factor. These
risks are probabilities that are generally expressed in scientific
notation (e.g., IxlO"6 or 1E-6). An excess lifetime cancer risk of
IxlO"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.
The results of the risk assessment for the site indicated that
chemical exposures through the aforementioned exposure pathways may
be associated with cancer risks which achieve or exceed EPA's target
risk range of 10 to 10 . The primary contaminant of concern at the
Halby Chemical Site is arsenic although the broad spectrum of CPAHs
also elicit some notable cancer risk. The carcinogenic risks for
each contaminant of concern for each exposure pathway are presented
in Table 6.
30
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Table 5
TOXICITY PARAMETERS FOR CONTAMINANTS OF CONCERN
IN PROCESS PLANT AREA (OD1)
EALBY CHEMICAL SITE
Compound
Benzo(k)fluoranthene
Benzo(a)pyrene
CPF*
(mq/Xq/day)
-i
CPF1
(mq/Xq/davr1
RfDu
(mq/kq/dav)
Arsenic
Chromium*
Carbon Disulfide
Pyrene
Benzo (a) anthracene
Chrysene
Benzo (b) f luoranthene
1.75
4.1
9.32 X 10"1
1.67
5.06 X 10~2
1.61
5 X 101
4.94 X 10"1
8.84 X 10"1
6.77
8.54 X 10~1
1 x 10"3
5 X 10'3
1 X 10"1
7.59 X 10
-1
1.15 X 10
-1
4.03 X 10
6.10
-1
CPF° - Cancer Potency Factor for oral exposure.
CPF' - Cancer Potency Factor for inhalation exposure.
RfD° - Reference Dose for oral exposure, noncarcinogenic effe'cts.
* Chrome VI potency factor used although most soil chromium is the
noncarcinogenic chrome III (conservative approach).
31
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Table 6
INCREMENTAL CANCER RISKS BY EXPOSURE PATHWAYS
PROCESS PLANT AREA (OD1)
HALBY CHEMICAL SITE
I. CURRENT QBE SCENARIO
A. The Incidental Oral (Ingestion) Exposure Route
RME CONC.
CONTAMINANT UO/kQ
CDI CANCER INCRE.
ma/ka/dav POT.FACT. GANG.RISK
ORGANICS (PAHS) !
Pyrene
Benzo(a)
anthracene
Chrysene
Benzo(b)
f luoranthene
Benzo(k)
f luoranthene
Benzo(a)pyrene
i
»
17861
5334
6051
3597
3155
2337
3.1E-06
9 . 3E-07
1.1E-06
6.3E-07
5.5E-07
4 . 1E-07
9.32E-01
1.67E+00
5.06E-02
1.61E+00
7.59E-01
1.15E+01
3E-06
2E-06
6E-08
1E-06
4E-07
5E-06
PAH Total Incre. cancer Risk ...IE-OS
INORGANICS:
Arsenic
4.12E+05 7.2E-05 1.75E+00
1.3E-04
-------
Table 6 (eont)
B. The Inhalation of Airborne Participates Exposure Route
RME CONG. GDI CANCER INCRE.
CONTAMINANT UQ/lCQ no /tea /day POT. PACT* GANG. RISK
Carbon Disulfide**
Pyrene 17861
Benzo(a)
anthracene 5334
Chrysene
6051
Benzo(b)
fluoranthene 3597
Benzo(k)
fluoranthene 3155
Benzo(a)pyrene 2337
6.3E-07 4.94E-01 3E-07
1.8E-07 8.84E-01 2E-07
2.1E-07 6.77E+00 1E-06
1.3E-07 8.54E-01 1E-07
1.1E-07 4.03E-01 4E-08
8.3E-08 6.10E+00 5E-07
Total Incre. Cancer Risk = 2E-06
Arsenic 4.12E+05 1.46E-05 5.00E+01 7.3E-04
Chromium 1.70E+05 6.03E-06 4.10E+01 2.5E-04
* Inhalation potency factors in mg/kg/day
** Carbon Disulfide is not considered to be a carcinogen by
the Agency
33
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Table 6 (eont)
c. The Dermal Absorption Exposure Route
RME CONC.
CONTAMINANT UQ/ko
GDI CANCER
ma/ka/dav POT.FACT.
INCRE.
CANC.RISK
PYRENE 17861
Benzo(a)
anthracene 5334
Chrysene 6051
Benzo(b)
fluoranthene 3597
Benzo(k)
fluoranthene 3155
Benzo(a)pyrene 2337
2.8E-05
5.7E-06
9.32E-01
8.4E-06 1.67E+00
9.6E-06 5.06E-02
1.61E+00
5.0E-06 7.59E-01
3.7E-06 1.15E+01
TOTAL .,
3E-05
1E-05
5E-07
9E-06
4E-06
4E-05
.9E-05
-------
Table 6 (cent)
II. FUTURE USE SCENARIO
A. Tbe
DEPTH
4'0"
6*0"
lO'O"
Ineidential
RME GDI
874
282
265
Oral (Ingest ion) Exposure
ARSENIC
(ma/ka/d) CAN. POT. FACT
6.1E-06
1.9E-06
1.8E-06
1.75E+00
1.75E+00
1.75E+00
Route
INCRE.RISK
IE-OS
3E-06
3E-06
B. The Inhalation of Airborne Particulates Exposure Route
ARSENIC
DEPTH
4'0"
6'0"
10 «0"
RME
872 -
282
265
CDI(ma/ka/d)
1.2E-06
3.9E-07
3.7E-07
CAN. POT. FACT.
5.0E+01
5.0E+01
5.0E+01
INCRE.RISK
6E-05
2E-05
2E-05
35
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The risk assessment for various exposure scenarios indicated tha.
the soil at the Halby Chemical Site poses a potential risk to human
health (expected value of cancer risk >10'6). The current use
pathway poses excess cancer risks greater than 10 . Remedial action-
is generally warranted at a site when the cancer risk is determined
to be above the upper bound of the risk range identified in the
National Contingency Plan (10"6 to 10"*).
The exposure pathways and expected excess cancer risks are
presented below:
Expected Excess
Exposure Pathway Cancer Risk
1. Current Site Land Use;
Ingestion of dusts and soils
containing:
arsenic 1.3 x 10
CPAHs 1 x 10"*
Total 1.4 x 10"*
Inhalation of dusts and soils
containing:
arsenic 7.3 x 10
chromium 2.5 x 10**
CPAHs 2 x 10**
Total 9.82 x 10"*
Dermal Absorption of CPAHs from
Soils that adhere to skin 9 x 10*5
TOTAL CANCER RISKS 1.2 X 10*3
2. Future Site Land Use;
Ingestion of dusts and soils
containing arsenic 1 x 10*5 § 4 feet
Inhalation of dusts and soils
containing arsenic .. 6 x 10*5 @ 4 feet
TOTAL CANCER RISKS 7 x 10*5 9 4 feet
Arsenic elicits an incremental cancer risk of a calculated 1.3 X
10 over a lifetime by the incidental ingestion route and an
incremental risk of 7.3 x 10** by the inhalation route for a combined
incremental risk of about 8.6 x 10** to the workers at the process
plant area. This rounds off to a 1.0 x 10*3 incremental cancer risk
36
-------
from arsenic located in surface soils. Any future health threats are
from arsenic exposure during operations that involve the digging into
buried contamination. The incidental ingestion pathway could cause
an incremental exposure of as much as 1 x 10 while the inhalation
pathway could cause an additional 6 x 10 cancer risk.
The cleanup goal for arsenic will be set at its background level,
however, the background value of 10 ppm for arsenic is based on a
limited number of samples at the Halby chemical Site. Existing EPA
guidance suggests that additional samples are necessary in order to
determine a statistically representative background value for
arsenic. This additional sampling will be used to determine the
value which will be used as the cleanup criteria for arsenici
Setting the cleanup goal for arsenic in soils at background would be
practicable and the excess cancer risk will be sufficiently reduced
for protection of human health.
If the RME soil levels of chromium are assumed to be the
hexavalent form (which is highly unlikely) there is an incremental
cancer risk of 2.5 x 10 by the inhalation pathway. The soil
chromium is very likely to be in the relatively harmless and
noncarcinogenic trivalent form, however, this should be confirmed in
the field.
The wide spectrum of CPAHs elicits about a 1 x 10"5 incremental
cancer risk to the workers over a lifetime by the incidental
ingestion pathway, but a 9 x 10 incremental cancer risk by the
dermal absorption pathway (close to a 10~4 risk). The inhalation of
airborne particles contaminated with CPAHs only elicits a risk of 2 x
10 additional cancers. When all exposure pathways are added, CPAHs
contribute about a 1 x 10"4 incremental cancer risk to the workers.
A cleanup goal for CPAHs in soils will be set at background.
This cleanup standard would be practicable and would result in
residual cancer risks of less than 10'*, however, the background
value of 1.2 ppm is based on a limited number of samples. EPA
guidance suggests that additional samples are necessary in order to
determine a statistically representative background value for CPAHs
at the Halby Chemical Site. This additional sampling will be used to
determine the value which will be used as the cleanup criteria for
CPAHs.
Nencarcinoaenic Effects - Potential concern for noncarcinogenic
effects of a single contaminant in a single medium is expressed as
the hazard quotient (HQ) which is 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.
37
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Noncancerous threats as demonstrated in Table 7 by the hazard
quotients for arsenic and chromium were not particularly notable and
summed to a hazard index of 0.13 suggesting that the combined
concentrations of these elements is about 13% of that necessary to
constitute a threat to the workers. The widespread carbon disulfide
does not present any notable risk to the workers at this facility.
Table 8 presents the future noncancerous toxic hazard calculation
results for exposure to buried arsenic. The depths assessed, RMEs
utilized, and calculated daily intakes (GDI) are the same as those
used for the ingestion pathway under the future use scenario in Table
6. It should be noted that arsenic is both a carcinogen and a
noncancerous threat. All other future risks and noncarcinogenic
hazards would be trivial.
Risks - There are no critical habitats, endangered
species or habitats of endangered species affected by site
contaminants within the process plant area . Areas where
environmental risks exist will be addressed in Operable Unit 2 for
the site.
7. DESCRIPTION OF ALTERNATIVES
Prior to discussing the alternatives for Operable Unit 1 it
should be stated that there are no Federal or State of Delaware
chemical-specific ARARs which establish a cleanup action level for
contaminated soil at the Halby Chemical Site. The cleanup levels for
Operable Unit 1 will therefore be established based on the
aforementioned current and future risk values taking into account the
background levels of contaminants found in the area of the site.
Based on a limited number of samples at the Halby Chemical Site
background levels were established as follows:
Arsenic - background is approximately 10 ppm on average
CPAHs - background is approximately 1.2 ppm on average
Existing EPA guidance suggests that additional samples are necessary
in order to determine a statistically representative background value
for both arsenic and CPAHs. This additional sampling will be used to
determine the value which will be used as the cleanup criteria for
arsenic and CPAHs.
The following alternatives for Operable Unit 1 were evaluated in
detail in the Feasibility Study to determine which would be most
effective in achieving the goals of CERCLA, and in particular,
achieving the remedial action objectives for the site. The detailed
analysis of remedial alternatives for Operable Unit 1 are described
38
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Table 7
NONCARCINOGENIC TOXIC HEALTH THREATS
HAZARD QUOTIENT AND HAZARD INDEX CALCULATIONS
CURRENT USB SCENARIO
PROCESS PLANT AREA (OU1)
HALBY CHEMICAL SITE
RME (ma/ka of soill CDIfna/ka/davl RfDfmcr/ka/dl ' HQ
Arsenic 412
Chromium 170
Lead 309*
Mercury 14
Nickel 62
Zinc 1461
Carbon
Disulfide 16
7.2E-05
2.9E-05
2.5E-06
l.OE-05
2.5E-04
2.5E-05
l.OE-03
5.0E-03
2.0E-03
2.0E-02
2.0E-01
l.OE-01
0.07
0.06
0.001*
5E-04*
0.001*
3E-04*
Hazard Index (HI)
0.13
(Note: noncarcinogenic toxic impacts from PAH compounds are
too minuscule to warrant consideration in this table)
Note:
This Hazard Index indicates that these contaminants
elicit a non-carcinogenic chronic toxic threat that is about
13 percent of the magnitude that could be a concern.
»>
These contaminants were determined to be present at
concentrations that provoked a hazard quotient that is less than
0.01. Therefojr they are not contaminants of concern, but since
they were commonly detected these results are provided to support
the decision that they should not be considered further.
** Since there is no RfD for lead this element is assessed
by comparing both its arithmetic average (273 ppm) and RME (309)
with the CDC recommendation of a 500 to 1000 ppm criterion for
industrial areas. This would suggest that lead does not
constitute a health threat to the workers at this facility.
39
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Table 8
NONCARCINOGENIC THREATS FROM
EXPOSURES TO ARSENIC-CONTAMINATED SOILS
FUTURE USE SCENARIO
PROCESS PLANT AREA (OU1)
EALBY CHEMICAL SITE
DEPTH RME GDI fma/kcr/d) RfD Hazard Quotient
4'0" 872 6.1E-06 l.OE-03 6E-03
6'0" 282 1.9E-06 l.OE-03 2E-03
lO'O' 265 1.8E-06 l.OE-03 2E-03
40
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below. The alternatives are numbered to correspond with the numbers
in the RI/FS Report. The cost and implementation times presented
with each alternative are estimates and should be used for
comparative purposes only. The implementation times are for
construction of the alternative and do not include any time for pre-
design or design activities.
a. Alternative 8-1i No Action
Capital Costs: $40,000
Annual O&M 38,000
Present Worth: 655,000
Months to Implement: 1
The no action alternative for the contaminated soil is the
baseline alternative for comparison with the other alternatives.
Under this alternative, no action would be taken to remediate the
contaminated soil at the site. The no action alternative provides
for long-term monitoring and site reviews every five years. Long-
term monitoring of the site would examine the soils, sediment and
surface water contaminants. The program would identify any changes
in the site conditions which could pose an increase in the risk from
the site. This monitoring program would include annual visual site
inspections with sampling and analysis of areas that are suspect.
Because this alternative does not entail contaminant removal, the
site would have to be reviewed every five years as called for in the
Superfund Amendments and Reauthorization Act (SARA).
The long-term monitoring program is designed to monitor the
process plant and the lagoon and would include the following:
1. Surface water samples would be collected
from locations, as indicated in Figure 7. The samples
would be analyzed for volatile organics, Target Analyte
List (TAL) compounds, ammonia, nitrate, cyanide, and
thiocyanate.
2. Sediment samples would be collected from
locations, as indicated in Figure 8'. The sediment
samples would be analyzed for full TCL and TAL, ammonia,
nitrate, cyanide, and thiocyanate.
3. A visual site inspection would be performed to note any
changes from the previous inspection.
4. The analytical and inspection results would be tabulated
in a report for review by the State of Delaware and EPA.
This long-term monitoring program would be performed annually for
up to 30 years. Remediation of groundwater would be addressed under
Operable Unit No. 2 for the Halby Chemical Site. Groundwater samples
are therefore not included in the long-term monitoring program
described here.
41
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UGCNO:
HALBY
CHEMICAL
H CLCCmiC CABLt IOVKR TRCSTU
FCNCING
VtRnCAl TANKS
HORIZONTAL TANKS
ORAINAGC TRCNCH
RARROAD TRACKS
BLOC. FOOT PRINT
UOMTOMNC *CLLA«t HYDRANT
PROPOSED SAMPLE
LOCATION
FIGURE 7
LONG-TERM SURFACE WATER
MONITORING LOCATIONS
HALBY CHEMICAL SITE FEASIBILITY STUDY
NEW CASTLE COUNTY. DELAWARE
-------
LCCOTO:
B ELECTRIC CABl£ TOWER TRES1U
FENCINC
VERTICAL TANKS
HORIZONTAL TANKS
» DRAINAGE TRENCH
RAILROAD TRACKS
BLOC. FOOT PRINT
SURFACE WATER SAMPLING STATION
PROPOSED SAMPLE
LOCATION
FIGURE 8
LONG-TERM SEDIMENT
MONITORING LOCATIONS
HALBY CHEMICAL SITE FEASIBILITY STUDY
NEW CASTILE COUNTY. DELAWARE
-------
Although the NCP requires EPA to consider the no-action
alternative, it would not be protective of human health since it does
not meet the aforementioned health-based cleanup goals. The process
plant area is not located in the 100-year floodplain and is not a
wetland. There are no known endangered species living inside the
plant area. There are no data to indicate that the process plant
area contains any sites which may be considered to be of historic or
archeological significance. Thus, there are no location-specific
ARARs associated with this portion of the site. Monitoring would be
conducted according to OSHA Health and Safety Standards. There are
no other action-specific ARARs applicable to Alternative S-l. All
action-specific ARARs for Operable Unit 1 are listed in Table 9.
b. Alternative B-2: Limited Action
Capital Costs: $70,000
Annual O&M: 39,000
Present Worth: 696,000
Months to Implement: 1
The major work items associated with this alternative are as
follows:
Upgrade the existing perimeter fence and install warning
signs;
Establish institutional controls to limit the use of
contaminated areas and groundwater;
Monitor with site inspections and long-term monitoring
program to determine changes in site conditions and their
effects on the risks associated with the area;
Conduct public education programs by means of meetings,
presentations, or workshops to increase public awareness of
the site conditions; and
Perform site reviews every five years.
The limited action alternative for the contaminated soil at the
process plant area would not include any containment or treatment to
remediate the site soil. For this alternative, deed restrictions,
public education, fencing and long-term monitoring are used to reduce
the potential hazards at the Halby Chemical site. The deed (
restrictions would be imposed for the entire site to limit or
restrict groundwater uses, excavation in areas of subsurface soil
contamination, and cross contamination of the lower Potomac aquifer
by improper installation of deep wells in the area. Public education
programs would be established to inform all interested parties of the
conditions existing at the site. Site access would be restricted by
improvement of the existing fence and placement of warning signs
around the area. Long-term monitoring of the site (as described in
44
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Table 9
ACTION-SPECIFIC ARMS FOR SOIL
OPERABLE UNIT 1
HALBY CHEMICAL SITE
ARARS
STATUS
A. Common to all alternatives:
OSHA-Ceneral Industry Standards (29
CFR 1910)
Applicable
OSHA-Safety and Health Standards
CFR 1926)
OSHA-Record Keeping. Reporting and
Related Regulations (29 CFR 1904)
RCRA-Standards for Owners/Operators of
Remitted Hazardous Wast* Facilities
(40 CFR 264.10-264.18)
RCRA-Preparedness and Prevention
(40 CFR 264.30-264.31)
RCRA-Contingency Plan and Emergency
Procedures (40 CFR 254.50-264.56)
ONREC Regulations Covering Hazardous
Substances Cleanups (Part IX, Ch.91 Sec
9101-9120)
Applicable
Applicable
Relevant And
Appropriate
Relevant And
Appropriate
Relevant And
Appropriate
Relevant And
Appropriate
REQUIREMENT SYNOPSIS
These regulations specify the
8-hour tine-weighted average
concentration for worker expo-
sure to various organic cow-
pounds. Training requirements
for workers at hazardous waste
operations are specified in 29
CFR 1910.120.
This regulation specifies the
type of safety equipment and
procedures to be followed
during site remediation.
This regulation outlines the
record keeping and reporting
requirements for an employer
under OSHA.
General facility requirements
outline general waste analysis,
security measures, inspections,
and training requirements.
This regulation outlines the
requirements for safety equip-
ment and spill control.
This regulation outlines the
requirements for emergency
procedures to be used following
explosions, fires, etc.
Requires prompt containment and
removal of hazardous substances
to eliminate or minimize the
risk to public health or welfare
or the environment.
ACTION TO BE TAKEN TO ATTAIN ARARS
Proper respiratory equipment will be worn
if it is not possible to maintain the work
atmosphere below these concentrations.
All appropriate safety equipment will be on-
site and appropriate procedures will be
followed during treatment activities.
These regulations apply to the company(s)
contracted to install, operate, and main-
tain the remedy.
Facility will be designed, constructed, and
operated in accordance with this requirement.
All workers will be properly trained.
Safety and communication equipment will be
installed at the site, local authorities
will be familiarized with the site.
Plans will be developed and implemented
during remedial design. Copies of the
plans will be kept on-site.
Hazardous substances will be contained or
removed promptly.
U1
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Table
(cant)
ARABS
STATUS
B. Off-Site Disposal:
Waste Transportation:
DOT Rules for Transportation of Hazardous
Material (49 CFR Parts 107, 171.1-17Z.558)
Standards Applicable to Transporters of
Hazardous Waste - RCRA Section 3003, 40
CFR 262 and 263. 40 CFR 170 to 179
DHUR - Part 263, Standards Applicable
Transporters of Hazardous Waste
Disposal;
RCRA Land Disposal Restrictions (40 CFR
268, Subpart 0)
Applicable
Applicable
REQUIREMENT SYNOPSIS
Applicable
Applicable
EPA Actain
Ot
Applicable
To Be Considered
This regulation outlines procedures
for the packaging, labeling. Mani-
festing, and transporting of hazard-
ous Materials.
Establishes the responsibility of off-
site transporters of hazardous waste
in the handling, transportation, and
Management of the waste. Requires a
manifest, recordkeeping, and immediate
action in the event of a discharge of
hazardous waste.
The Delaware Department of Natural
Resources and Environmental Control
(ONREC) has adopted certain DOT regu-
lations governing the transport of
hazardous Materials.
After November 8, 1988, Movement of
of excavated Materials to new location
and placement in or on land would
trigger land disposal restrictions
(for non-CERCLA actions). CERCLA
actions became regulated under this
requirement on November 8, 1990.
Covers the basic permitting, applica-
tion, monitoring and reporting require-
ments for off-site hazardous waste
management facilities.
Delaware program to properly manage
solid waste storage, collection, trans-
fer, and disposal by obtaining a permit.
ACTION TO BE TAKEN TO ATTAIN ARARS
This regulation will be applicable to any company
contracted to transport hazardous material from
the site.
This regulation will be applicable to any company
contracted to transport hazardous Material from the
the site.
This regulation will be applicable to any company
contracted to transport hazardous material from
the site.
If soil and sediment are RCRA wastes, the excavated
material will be properly disposed or treated as
required by the regulations.
Any off-site facility accepting hazardous waste from
the site Must be properly permitted. Implementation
of the alternative will include consideration of
requirements.
This regulation may be applied to the disposal of
debris on-site.
-------
ARARS
STATUS
Table 9 (cent)
REQUIREMENT SYNOPSIS
ACTION TO BE TAKEN TO ATTAIN ARARS
I. Excavation and/or Stabilization;
tAA- NAAQS for Total Suspended
'articulates (40 CFR 129.105, 750)
Relevant And
Appropriate
This regulation specifies MX {MM
and secondary 24-hour concentrations
for paniculate matter. Fugitive dust
emissions fro* site excavation
activities Must be Maintained below 260
ug/m (primary standards).
Proper dust suppression methods such as water spray
would be specified when implementing excavation and/or
stabilization actions.
.0 CFR 262: RCRA
.0 CFR 261: RCRA
0 CFR 264: Subpart L
.0 CFR 264: RCRA
0 CFR SO: NAAQS
jNREC-Environmental Control (Part VII,
:h. 60. Sec. 6003)
HWR-Chemical. Physical and Biological
treatment (Subpart Q, Section 265.400-
Applicable
Applicable
Applicable
Relevant And
Appropriate
Applicable
'NREC-Regulatiora Governing the control Relevant And
f Air Pollution (Regulation Nos. 2, 3. 6 Appropriate
;nd 21)
Relevant And
Appropriate
Relevant And
Appropriate
Establishes standards for generators of
hazardous wastes including waste deter-
mination, manifests, and pre-transport
requirements.
Hazardous Uaste determination.
Provides requirements to design and
operate waste piles.
This regulation will be applicable upon excavation and
on-site storage of site wastes.
Wastes will be compared to Federal Register listing to
determine if they are listed or characteristic wastes.
Performance standards would be specified for compliance.
Requires owner/operator to control wind Fugitive dust emissions will be controlled during implemen-
disposal of particulate matter. tat ion to maintain concentrations below these levels.
Provides air quality standards for
particulate matter and lead.
Details the required permits, ambient
air quality, allowable dust control
during excavation activities and
emission standards.
Requires a permit if any contaminants
are discharged to the air, surface
water or groundwater.
Outlines operating requirements,
analysis and trail tests, inspections
and closures for hazardous waste treat-
ment processes.
Same as below.
Proper dust suppression methods and monitoring will be >
required when implementing excavation and/or stabilization
actions.
Practices will be followed to reduce potential emissions.
If discharges are anticipated, an application for a permit
will be submitted.
Required waste analysis, trail tests, inspections, closures
and operation procedures will be used during stabilization
treatment.
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Table
(cant)
ARABS
STATUS
DHREC - Delaware Erosion and Sediment
Control Handbook for Development (1989)
and Delaware's Erosion and Sediment
Control Law (Chapter 40. Title 7.
Delaware Code)
D. Closure: (For Alternative S-5 only)
Clean Closure;
ROM-General Standards (40 CFR 264.111)
Relevant And
Appropriate
REQUIREMENT SYNOPSIS
ACTION TO BE TAKEN TO ATTAIN ARARS
Relevant And
Appropriate
RCRA-Nanlfesting, Recordkeeping and
Applicable Reporting (40 CFR 264.70-
264.77)
DHUR-Closure and Post-Closure (Subpart
C, Sections 264.110-264.120)
E. Capping (Waste In Place):
RCRA-Landfills (40 CFR 264.310(a))
Applicable
Relevant And
Appropriate
Relevant And
Appropriate
Outlines Delaware Erosion and Sediment Recommended practices will be followed during excavation. An
Control Law Regulations and practices to erosion and sediment control plan will be submitted for
minimize erosion. review and approval to comply with state erosion and sediment
control requirements for land-disturbing activities.
Proper design considerations will be implemented to minimize
the need for future maintenance.
Requirement will be followed during closure.
State requirements will be followed to ensure compliance.
General performance standard requires
minimization of need for further main-
tenance and control; minimization or
elimination of post-closure escape
of hazardous waste, hazardous constitu-
ents, leachate, contaminated runoff, or
hazardous waste decomposition products.
Also requires disposal or decontamina-
tion of equipment, structures, and
soils.
This regulation specifies the record-
keeping and reporting requirements for
RCRA facilities.
This regulation details state closure
requirements including performance
standards, closure plans, disposal
or decontamination of equipment and
post-closure plans and uses.
Placement of a cap over waste requires Design considerations will include all requirements.
a cover designed and constructed to:
- Provide long-term minimization of
migration of liquids through the
capped area;
- Function with minimum maintenance;
- Promote drainage and minimize erosion
or abrasion of the cover;
00
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Table
(cant)
ARABS
STATUS
:CRA-Generel Standards (40 CFR
'64.117(c»
4A-NAAQS for Particulate Natter Leas
ihan 10 Nfcrona in Diameter (40 CFR Part
-0, Appendix J)
4A-NAAQS for Total Suapended Particulate*
;40 CFR 2129.105,750)
Relevant And
Appropriate
Relevant And
Appropriate
Relevant And
Appropriate
REQUIREMENT SYNOPSIS
- Accommodate settling and aubsl-
dence BO that the cover's interity
is maintained;
Have a permeability less than or
equal to the permeability of any
bottom liner system or natural sub-
soil present.
Restricts post-closure use of property
as necessary to prevent damage to the
cover.
This regulation specifies annual arith-
metic mean and maximum 24-hour concen-
trations for participate matter.
This regulation specifies maximum pri-
mary and secondary 24-hour concentra-
trations for particulate matter. Fugi-
tive dust emissions from aite excavation
activities must be maintained belou 260
ug/m (primary standard).
ACTION TO BE TAKEN TO ATTAIN ARARS
Post-Closure uses Mill
the cover.
be limited to those that will not
Proper dust suppression methods Mill be employed to keep
concentrations belou regulations.
Proper dust suppression methods will be employed to keep
concentrations below regulations.
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Alternative S-l) would be conducted to identify any changes in the
site conditions. Samples would be taken annually for 30 years to
identify major changes in arsenic and PAH contamination on-site.
Because this alternative leaves contamination on-site, the site would
be reviewed every five years as required by SARA. The review would
include comparing the monitoring data to the RI results to determine
whether or not the remedial measures have been effective.
The process plant area is not located in a 100-year flood plain
and is not a wetland. There are no known endangered species living
inside the plant area. There are no data to indicate that the
process plant area contains any sites which may be considered to be
of historic or archeological significance. Thus, there are'TVO
location-specific ARARs associated with this portion of the site.
Monitoring and, fence and sign installation would be conducted
according to OSHA Health and Safety Standards. This alternative
would not achieve the soil cleanup goals, and thus is not considered
to be protective of human health.
c. Alternative 8-3: Capping
Capital Costs: $493,000
Annual O&M: 43,000
Present Worth: 1,188,000
Months to Implement 2
The capping alternative is a partial containment remedial action.
The primary purpose of the cap is to prevent direct contact with the
contaminated soil and fugitive dust migration. This alternative also
includes deed restrictions, public education, fencing, monitoring
programs, and five-year reviews specified in the limited action
alternative (S-2). The area to be capped (area within perimeter
fence) is shown in Figure 9.
Debris, including steel plates, lumber, and miscellaneous
material, have been observed on-site. These would be consolidated or
disposed of so that they would not interfere with the capping
operations. Some areas of the plant are also- covered with
vegetation. This vegetation would be removed and. disposed off-site
prior to capping.
The contaminated soil within the Halby Chemical process plant
area would be covered with an asphalt aggregate mix. Any structures
and outdoor equipment would be left intact. The area used for truck
access and parking would require some road bed improvement. The
asphalt cover would include a four-inch asphalt aggregate mix layer
and a three-inch gravel layer and would cover approximately 5,800
square yards. The asphalt cover would not cover the railroad track,
and the area adjacent to the track would be covered with stone and
gravel. In order to minimize impacts to existing plant operations,
capping would proceed in stages (i.e., only one portion of the site
50
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HALBY
CHEMICAL
SITE
OtCTRIC CABLC TO«CR TRESTLE
»- FENCING
VERTICAL TANKS
HORIZONTAL TANKS
-» DRAMACC TRENCH
RAILROAD TRACKS
BLOC. fOOT PRINT
SURHOAL SOIL SAMPLING STATION
FIGURE 9
PERIMETER FENCE
OF PROCESS PIANT
HALBY CHEMICAL SITE FEASIBILITY STUDY
NEW CASTLE COUNTY. DELAWARE
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would be capped at any time).
The cap would be designed and constructed to meet the following
objectives:
Function with minimum maintenance;
Promote drainage;
Prevent runoff from damaging (eroding) the area around the
cap; and
Accommodate settling and subsidence, such that the cap's
integrity would be maintained.
The surface runoff from the capped plant area could either
discharge to the lagoon or the sewer. The runoff would not be
contaminated, as contact with contaminants is eliminated by the cap.
This alternative provides containment of contaminated soil above
the cleanup goals, thus preventing exposure to soils, thereby
achieving the remedial action objectives. The process plant area is
not located in a 100-year flood plain and is not a wetland. There
are no known endangered species living inside the plant area. Ther
are no data to indicate that the process plant area contains any
sites which may be considered to be of historic or archeological
significance. Thus, there are no location-specific ARARs associated
with this portion of the site.
During site work, Clean Air Act and State of Delaware air
requirements must be considered. If regulatory limits are exceeded,
dust suppression would be employed. Requirements for these
activities include OSHA Health and Safety Standards as shown in Table
9.
Post-closure use of the property must be restricted, as
necessary, to prevent damage to the cover. Cap construction would
follow OSHA requirements. Long-term monitoring and site security
measures would have to be executed in accordance with Federal and
State RCRA hazardous waste facility standards.
Section 121 (c) of CERCLA, as amended, 42 U.S.C. $9621 (c)(,
requires a periodic review of remedial actions at least every five
years for as long as hazardous substances remain on-site. Therefore,
Alternative S-3 would satisfy action-specific ARARs identified for
this alternative.
52
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d. Alternative B-4! surface Soils Stabilization/Asphalt Cap
Capital Costs: $891,000
Annual O&M: 43,000
Present Worth: 1,586,000
Months to Implement 3
The major components of this alternative include the following:
1. Consolidate all debris on-site into one area, or dispose
of debris off-site;
2. Perform a treatability study to identify a proper
stabilization formula;
3. Excavate top 6 inches of contaminated surface soil;
4. Stabilize excavated soil;
5. Backfill stabilized soil;
6. Cover the stabilized soil with an asphalt cap;
7. Implement deed restrictions and public education programs;
8. Perform long-term monitoring and maintenance.
Debris including steel plates, piping, lumber, and miscellaneous
materials was observed scattered throughout the site. In order to
facilitate excavation, this debris must be consolidated into one area
or disposed off-site.
This alternative involves the excavation of the top six inches of
contaminated surface soil in the process plant area, followed by
stabilization of the soil and replacement back into the excavated
area. The contaminated soil would be mixed with stabilization agents
to immobilize the contaminants of concern and would be placed back
over the excavated area. The backfilled soil would be compacted to
provide a stable sub-base for the asphalt cap.' Any structures and
outdoor equipment would be left intact.
The asphalt cap would be constructed within the area indicated in
Figure 9 and would be placed approximately seven inches thick. The
cap would include a 3 inch gravel layer, and a 4 inch asphalt
aggregate mix. The area used for truck access and parking would
require some roadbed improvement. The asphalt cover would not cover
the railroad track. The area adjacent to the track would be covered
with stone and gravel. In order to minimize impacts to existing
plant operations, the excavation, stabilization, and capping
processes could proceed in stages (i.e., only one portion of the site
would be remediated at any one time).
53
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The cap would be constructed to meet the following objectives:
Function with minimum maintenance;
Promote drainage and minimize erosion of the cap;
Prevent runoff damage around the cap; and
Accommodate settling and subsidence, such that the cover's
integrity is maintained.
Prior to implementing this alternative, a treatability study
would be performed to identify a proper stabilization formula. It is
understood that arsenic is relatively difficult to immobilize. The
treatability study (TS) performed during the Remedial Investigation
indicated that more metals were leached out after treatment using
cement as the binder, even though the leachates from the treated and
untreated soil were both below the TCLP criteria. The asphalt binder
tested in the same TS reduced the leachability of arsenic. Many
commercial vendors have claimed to have successfully immobilized
arsenic. Treatability studies performed for the Whitmoyer Laboratory
Superfund site, which contained high concentrations of arsenic in
soil and sediment, have successfully reduced the leachability of
arsenic by 90% using ferric sulfate as a stabilizing agent.
Because of the congested nature within the process plant area,
some areas might not be accessible for excavation. If this should
occur, the inaccessible area would be covered with clean soil,
stone/gravel, or asphalt aggregate mix. At the completion of the
capping operation, the chemical plant could be returned to its normal
operation. Because the asphalt cap would have a relatively low
permeability, rain water will not infiltrate into the stabilized
material or the soil. Surface runoff would be channeled to the
lagoon or the storm sewer on-site. The runoff would not be
contaminated, as contact with contaminants is eliminated by the cap.
Because a significant amount of contaminants would still remain on-
site, this alternative would include the deed restrictions, public
education, and long-term monitoring programs as described under
Alternative s-2.
This alternative would immobilize surface soil contaminated above
the cleanup goals, thus achieving the remedial objectives. The
process plant area is not located in a 100-year floodplain and is not
a wetland. There are no known endangered species living inside the
plant area. There are no data to indicate that the plant site
contains any areas which may be considered to be of historic or
archeological significance. Thus, there are no location-specific
ARARs associated with this portion of the site.
During site work, Clean Air Act and State of Delaware air
requirements must be considered. If regulatory limits on air and
particulate emissions are exceeded, dust suppressants would be
54
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utilized. Requirements for these activities also include OSHA Health
and Safety Standards as shown in Table 9.
Post-closure use of the property must be restricted, as
necessary, to prevent damage to the cover, site remediation, long-
term monitoring and site security measures would have to be executed
in accordance with Federal and State RCRA hazardous waste facility
standards and pertinent State flood plain area construction
standards.
Since this alternative would result in hazardous substances
remaining on the site a periodic review would be conducted at the
facility, at least every five years, as required by Section '121(c) of
CERCLA, as amended, 42 U.S.C. $9621(c). Alternative S-4 would
satisfy all action-specific ARARs identified for this alternative.
e. Alternative 8-4a; Modified Soils Stabilization/Asphalt Cap
Capital Costs: $1,850,000
Annual O&M: 43,000
Present Worth: 2,700,000
Months to Implement: 3
This alternative is a modification of Alternative S-4. The only
difference between S-4 and S-4a is that S-4a addresses soil
stabilization with depth. A soil grid sampling program would be
required as a predesign activity to locate contaminants with depth
that exceed the aforementioned cleanup levels. Since it is not
practicable to stabilize soils which are below the water table, this
alternative would only provide treatment for soils which are above
the water table, and which exceed the cleanup goals established for
arsenic and CPAHs. Actual results of the soil grid sampling will be
used to define exact depths to which soil would be stabilized
throughout the process plant area. The estimated costs were
calculated based on stabilizing soil at a depth of two feet
throughout the process plant area. The same ARARs as discussed in
Alternative S-4 apply to this alternative.
f. Alternative 8-5; Excavation/Off-Site Disposal
Capital Costs: $4,995,000
Annual O&M: 38,000
Present Worth: 5,610,000
Months to Implement 6 v
The major components of Alternative S-5 include the following:
1. Collect and remove debris from the site;
2. Decontaminate and dismantle tanks, piping, pumps, and
other equipment;
55
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3. Decontaminate and dismantle tank foundations and railroad
tracks;
4. Excavate contaminated soil;
5. Transport and dispose of contaminated soil at an off-site
facility;
6. Backfill excavated area with clean soil;
7. Revegetate backfilled area;
8. Implement deed restrictions and public education -programs;
9. Perform long-term monitoring and maintenance.
This alternative involves excavation of contaminated soil and
disposal at an off-site RCRA landfill. The chemical plant would be
shut down permanently under this alternative.
Prior to excavation, scattered debris on-site would need to be
collected from the site and disposed of in a sanitary landfill. The
debris includes steel plates, piping, lumber, and miscellaneous
materials. It is not expected that this debris would be
contaminated. Decontamination, if necessary, would consist of
brushing off dust or washing with water.
This alternative would not remove the two structures or the
equipment housed inside. All existing tanks, piping, pumps, and
other equipment outside of the structures would be decontaminated by
solvent washing, detergent washing, or other methods as required.
The equipment would be dismantled and salvaged if possible, or
disposed of in an industrial landfill off-site. A total of 37 tanks
were observed on-site. There are no known underground storage tanks
on-site. Little information is available regarding the size,
condition, or contents of the tanks. Inspection and sampling would
be required during remedial design to determine the decontamination
requirements. Any products stored in these tanks should be removed
prior to the shutdown of the plant. Residual -wastes in the tanks
would be packaged and transported to a TSD facility for treatment and
disposal. Spent solvents from decontamination activities would be
treated off-site in a TSD facility. The railroad tracks inside the
plant fence and the tank foundations would also be removed.
After the process plant area is clear of obstacles, contaminated
soil would be excavated using construction equipment and disposed of
off-site in a RCRA hazardous waste landfill. During the excavation,
sampling and analysis would be performed to ensure that all soil
exceeding the cleanup goals established for arsenic and PAHs is
removed. Excavation would proceed to the groundwater table, or to a
depth of five feet, whichever is shallower. The total volume of soi
that would be removed is estimated to be 10,300 cubic yards from an
56
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area of 5,800 square yards. Based on the analytical results from the
TCLP tests performed on the untreated soil for the treatability
study, the contaminated soil from the Halby Chemical site would not
need treatment prior to landfilling under the Land Disposal
Restrictions.
RCRA hazardous waste disposal facilities with sufficient capacity
for disposal of contaminated soil are located in Ohio, Indiana, and
South Carolina. Industrial landfills and sanitary landfills are
available in nearby States (Pennsylvania, New Jersey, and Delaware)
for debris and miscellaneous waste.
Since the excavation would most likely proceed below the footings
of the building structures, engineering measures such as shoring and
sheet piling would be required to protect the buildings from
collapsing. Surface run-off during remediation would be treated by a
temporary treatment facility prior to disposal.
At the completion of the excavation, the excavated area would be
backfilled with clean soil from an off-site source. The area would
be covered with a layer of topsoil and revegetated. Surface runoff
would be discharged to the lagoon or the on-site storm water sewer.
Treatment of surface runoff following remediation would not be
required as contaminated surface soil will have been removed. A
fence would be built around the building to minimize physical hazards
to trespassers.
This alternative also includes deed restrictions, public
education, and the long-term monitoring programs specified under the
limited action alternative (S-2). A long-term monitoring program
would be required for the site since contaminated material in the
saturated zone would remain on-site. The site conditions would be
reviewed every five years for 30 years to assess the effectiveness of
the remedy.
This alternative would remove contaminated surface soil above the
cleanup goals, thus achieving the remedial action objectives. The
process plant area is not located in a 100-year flood plain and is
not a wetland. There are no data to indicate.that the plant area
contains any sites which may be considered to be of historic or
archeological significance. Thus, there are no Ideation-specific
ARARs associated with this alternative.
Excavation/disposal, long-term monitoring and site security
measures would have to be executed in accordance with Federal and
State RCRA hazardous waste facility standards, OSHA Health and Safety
Standards, and pertinent Delaware flood plain area construction
standards. During site work, Clean Air Act and State of Delaware air
requirements would be complied with. If regulatory limits are
exceeded, dust suppressants would be utilized.
57
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Movement of excavated materials to a new location and placement
in or on land may mean that the land disposal restrictions of 40 CFR
268, Subpart D apply to the excavated material. For the development
of this alternative, the land disposal restrictions would not be
invoked for the contaminated soil at the Halby Chemical site since
TCLP tests performed on site samples indicated that the soil would
pass the criteria for land disposal without treatment. However, this
assumption is based on a limited number of tests and must be
confirmed during remedial design.
General performance standards for clean closure (removal) require
elimination of the need for further maintenance and control. Since
contaminated soil will remain in the saturated zone, this removal
alternative would not meet the clean closure standards and long-term
monitoring would be required. Post-closure care and groundwater
monitoring for 30 years would be provided as required by RCRA 40 CFR
264.310.
Although the soil removed from the Halby Chemical site may not be
classified as hazardous wastes under RCRA, the facility receiving the
soil should be one which is in compliance with State and Federal
regulations for RCRA hazardous waste disposal. EPA's off-site
disposal policy would be followed in determining acceptable receiving
facilities.
Section 121(c) of CERCLA, as amended, requires a periodic review
of remedial actions at least every five years for as long as
contaminants that may pose a threat to human health or the
environment remain on-site.
8. SUMMARY OP COMPARATIVE ANALYSIS OP ALTERNATIVES
The five remedial action alternatives described above were
evaluated using the nine evaluation criteria as set forth in the NCP
40 C.F.R. S 300.430(e)(9). These nine criteria can be categorized
into three groups as shown below. A brief description of each of the
nine evaluation criteria is provided in Appendix I.
THRESHOLD CRITERIA
* Overall protection of human health and the environment
* Compliance with applicable or relevant and appropriate
requirements (ARARs)
PRIMARY BAyANgjflG CRITERIA
Long-term effectiveness
Reduction of toxicity, mobility, or volume through treatment
Short-term effectiveness
Implementability
Cost
58
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MODIFYING CRITERIA
* Community acceptance
* State acceptance
These evaluation criteria relate directly to requirements in
Section 121 of CERCLA, 42 U.S.C. Section 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. State and community acceptance are modifying
criteria formally taken into account after public comment is received
on the Proposed Plan. The evaluation of the five remedial -.
alternatives which were developed for Operable Unit 1 follows.
primary requirement of CERCLA is that the selected remedy 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. Alternative S-5 (Excavation/Off-Site Disposal)
provides protection for human health and the environment as most
contaminants would be removed from the site. Exposures through
direct contact, ingestion, and inhalation of contaminated soil would
be eliminated.
Alternatives S-3 (Capping), S-4 (Surface Soils
Stabilization/Asphalt Cap) and S-4a ( Modified Surface Soils
Stabilization/Asphalt Cap) would afford similar protection from
contaminated soil. The asphalt cap in all three alternatives and the
stabilized soil in Alternatives S-4 and S-4a would prevent direct
contact, ingestion, and inhalation of contaminated soil. However,
these processes are reversible (cap failure) and are not as permanent
as the removal action in Alternative S-5. However, Alternatives S-
4, and S-4a are superior to Alternative S-3 in minimizing risk
subsequent to a cap failure as Alternatives S-4 and S-4a provide for
stabilization of surface soil. Alternative S-2 (Limited Action) does
not provide protection from contaminated soil for the workers, but
provides some protection by limiting site access and implementing
institutional controls.
Exposure to contaminated groundwater is eliminated by deed
restrictions. Protection from exposure to contaminated groundwater
would be similar for all alternatives (except the no action
alternative) since they all use identical remedial measures \i.e.,
institutional controls, via deed restrictions). The need for
remediating groundwater will be further investigated under Operable
Unit 2 for the site.
Alternative S-l (No Action) does not provide any remedial
measures to protect human health except for monitoring the migration
59
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of contaminants. Since this alternative is not protective of human
health and the environment, it is dropped from further consideration.
b. Compliance with ARARs - This criterion addresses whether or not a
remedy will meet all of the applicable or relevant and appropriate
requirements of other environmental statutes and/or provide grounds
for invoking a waiver. There are no chemical-specific ARARs for
contaminated soil. However, Alternatives S-3 (Capping), S-4 (Surface
Soils Stabilization/Asphalt Cap), S-4a (Modified Surface Soils
Stabilization/Asphalt Cap) and S-5 (Excavation/Off-Site Disposal)
comply with health-based cleanup goals and achieve the remedial
action objectives. Alternative S-2 (Limited Action) does not comply
with the soil cleanup goals and does not achieve the remedial
objectives.
Since the process plant is not located in a wetland, within the
100-year flood plain, in an area that is a critical habitat for
endangered species, or in an area that is of historic or
archeological value, there are no location-specific ARARs that must
be complied with for Operable Unit 1.
All alternatives would be implemented in a fashion that complies
with action-specific ARARs as listed in Table 9.
c. Lonq-Term Effectiveness and Permanence - Long-term effectiveness
and permanence addresses the long-term protection of human health an
the environment once remedial action cleanup goals have been
achieved, and focuses on residual risks that will remain after
completion of the remedial action. Alternative S-5 (Excavation/Off-
Site Disposal) would be the most effective in the long-term as the
soil and disposal removal process is not reversible and is permanent.
Since most contaminated soil would be removed from the site to a
regulated landfill, it has the least residual risk at the site.
Alternatives S-3 (Capping), S-4 (Surface Soils
Stabilization/Asphalt Cap), and S-4a (Modified Surface Soils
Stabilization/Asphalt Cap) would provide less protection than
Alternative S-5 since all contaminants would remain on-site. Capping
and stabilization of surface soil are both reversible. The asphalt
cap has a finite lifetime. If the failed asphalt cap was not
replaced, the potential risks would be similar to existing conditions
for Alternative S-3; the potential risks would be less for
Alternatives S-4 and S-4a as the surface soil would be stabilized,
thus providing an extra level of protection. Repair of the asphalt
cap will be provided as part of the Operation and Maintenance (O&M)
of the cap. Alternative S-2 (Limited Action) would provide limited
protection by restricting access.
Alternatives S-2, S-3, S-4, S-4a and S-5 would provide identical
protection of human health from contaminated groundwater, while
Alternative S-l does not provide any protection. Alternatives S-3,
S-4, S-4a and S-5 would also reduce leaching into groundwater.
60
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Alternative S-5 would require the least maintenance while
Alternatives S-3, S-4 and S-4a would require some maintenance of the
caps. Alternative S-2 would require periodic maintenance of the
fence. The no action alternative does not require any maintenance
activities.
All alternatives would provide for identical long-term
monitoring. Deed restrictions are included for all alternatives
except the no action alternative.
Alternative S-2 has the highest possibility of requiring future
actions. The caps in Alternatives S-3, S-4 and S-4a would require
replacement some time in the future. Alternative S-5 has the least
possibility of requiring future actions.
d. Reduction of Toxicity. Mobility. r»r Vfti«»« - This evaluation
criterion addresses the degree to which a technology or remedial
alternative reduces the toxicity, mobility, or volume of a hazardous
substance. Section 121(b) of CERCLA, 42 U.S.C. Section 9621(b),
establishes a preference for remedial actions that permanently and
significantly reduce the toxicity, mobility, or volume of hazardous
substances over remedial actions which will not result in such
reduction. Alternative S-5 (Excavation/Off-Site Disposal) reduces
toxicity and volume of contaminants on-site but not via treatment.
Off-site disposal without treatment in a landfill does not meet the
statutory preference for treatment under SARA. The mobility of
contaminants in soil would also be reduced by placement in a properly
designed and operated landfill. Alternative S-4 (Surface Soils
Stabilization/Asphalt Cap) reduces contaminant mobility by a
stabilization process. However, the treatment only extends to 6
inches below the ground surface. Subsurface soils are not treated.
Alternative S-4a (Modified Surface Soils Stabilization/Asphalt Cap)
also reduces contaminant mobility by a stabilization process. Due to
contaminants being identified through a pre-design grid sampling
event, soils would be stabilized with depth. Alternatives S-3, S-4
and S-4a reduce infiltration of rain water and surface run-on by
capping. Alternative S-2 (Limited Action) does not reduce toxicity,
mobility, or volume of contaminants.
e. Short-Tern Effectiveness - Short-term effectiveness addresses the
period of time needed to achieve protection of human health and the
environment, and any adverse impacts that may be posed during the
construction and operation period until cleanup goals are achieved.
Alternative S-2 (Limited Action) provides for upgrading the existing
fence and the installation of warning signs. Alternative S-3
(Capping) involves capping of the site and has a greater chance of
releasing contaminants during implementation than Alternative S-2.
Alternatives S-4 (Surface Soils Stabilization/Asphalt Cap), S-4a
(Modified Surface Soils Stabilization/Asphalt Cap) and S-5
(Excavation/Off-Site Disposal) involve excavating contaminated soil
and have the greatest chance of air emissions. Alternative S-5
involves more soil handling and will take the longest time to
61
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implement. It also involves shipping waste off-site. It therefore
presents the highest short-term risks.
Once on-site actions begin, Alternative S-2 would take
approximately one month to implement. It would take approximately
two months to complete the asphalt cap required for Alternative 3.
Alternatives S-4 and S-4a would take approximately three months to
complete. It would take six months to excavate and dispose of
contaminated soil under Alternative S-5. Implementation times are
for construction activities only, no predesign or design time is
included.
f. Implementability - This criterion addresses the technical and
administrative feasibility of a remedy, including the availability of
materials and services needed to implement the chosen solution.
Alternative S-2 (Limited Action) involves the least construction and
would be the simplest to implement. However, the alternative does
not achieve the remedial action objectives.
Construction requirements for Alternative S-3 (Capping) are
fairly simple. Alternative S-3 has more construction activities than
Alternative S-2 because of the asphalt cap. Capping is a reliable
technology for prevention of direct contact, ingestion, and
inhalation of soil particles. However, the cap must be maintained in
order for it to be effective.
Alternatives S-4 (Surface Soils Stabilization/Asphalt Cap) and S
4a (Modified Surface Soils Stabilization/Asphalt Cap) involve more
construction activities than Alternative S-3. They include
excavation, stabilization, replacement of treated soil, and capping.
Alternative S-5 (Excavation/Off-Site Disposal) has the most
construction activities and involves the largest volume of
contaminated soil. It also includes decontamination and dismantling
of tanks and equipment. It would be the most difficult to implement.
All alternatives except Alternative S-5 have similar
administrative feasibility. All alternatives except the no action
alternative require deed restrictions, public-awareness programs, and
long-term monitoring. However, Alternative S-5 would require
shutdown of the plant permanently, which would require consent from
the current plant owner. Alternative S-l involves only long-term
monitoring.
All alternatives utilize proven technologies. Services and
materials are readily available. However, Alternatives S-4 and S-4a
may utilize a proprietary stabilization formula which may limit
competition to perform the remedial action.
g. Cost - CERCLA requires selection of a cost-effective remedy (not
merely the lowest cost) that protects human health and the
environment and meets the other requirements of the statute. Projei
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costs include all construction and operation and maintenance costs
incurred over the life of the project. An analysis of the present
worth value of these costs has been completed for each alternative
described in this Record of Decision, and is summarized in Table 10.
Capital costs include those expenditures necessary to implement a
remedial action.
The capital costs of the six alternatives range from $40,000 to
$4,995,000. The degree of protection provided by the alternatives
also varies. Comparison of different levels of costs for different
levels of protectiveness and permanence of treatment is a primary
decision criterion in the cost-effectiveness evaluation.
The no action alternative (S-l) has the least cost whiTe
Alternative S-5 (Excavation/Of f-site Disposal) has the highest cost.
It should be noted that monitoring costs contribute a major portion
of the cost of all alternatives except for Alternative S-5.
The three capping alternatives, Alternatives S-3 (Capping) , S-4
(Surface Soils Stabilization/ Asphalt Cap) and S-4a (Modified Surface
Soils Stabilization/Asphalt Cap), would reduce the risks to levels
which are generally considered acceptable for the corresponding
increase in cost. The excavation and of f-site disposal alternative
would virtually eliminate the risk from the plant area, but at a
significant increase in cost over the other alternatives.
h. State Acceptance - The State of Delaware accepts the selected
remedy as presented in this document.
i. ^nmmnity Acceptance - A Public Meeting on the Proposed Plan was
held on May 2, 1991. The Community concurs with the selected remedy
as presented in this document. Several of the PRPs submitted
comments during the public comment period which express concern
regarding the selected remedy. The PRPs comments, as well as all
other comments received during the public comment period, have been
summarized in the Responsiveness Summary.
9. SELECTED REMEDY
Section 121 of CERCLA, as amended, 42 U.S.C. S 9621, and the
National Oil and Hazardous Substances Pollution Contingency Plan
(NCP) establish a variety of requirements relating to the selection
of remedial actions under CERCLA. Having applied the evaluation
criteria to the six remedial alternatives, EPA has selected
Alternative S-4 (Surface Soils Stabilization/Asphalt Cap) as^the best
alternative for dealing with risks to workers in the process plant
area (Operable Unit 1) .
A description of the selected remedy can be found in Section 7 of
this ROD. The methodology which will be used to determine the extent
of the area to be stabilized and capped is described below. A pre-
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Table 10
Cost-Comparative Analysis
Halby Chemical
ALTERNATIVE S-l
ALTERNATIVE S-2
ALTERNATIVE S-3
ALTERNATIVE S-4
ALTERNATIVE S-4a
ALTERNATIVE S-5
CAPITAL
COST
$40,000
70,000
493,000
891,000
1,850,000
4,995,000
ANNUAL
O&M COST
$38,000
39,000
43,000
43,000
43,000
38,000
PRESENT
WORTH COST
$655,OOQ
696,000
1,188,000
1,586,000
2,700,000
5,610,000
A discount factor of 5 percent per year was assumed with
Annual Costs incurred for 30 years.
64
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design soil sampling study will be performed within the boundary of
the process plant area, as designated in Figure 9. The purpose of
the soil grid sampling is to more fully define the extent of soil
contamination in the process plant area. The soil grid sampling
system shall be surveyed and clearly marked by a licensed land
surveyor. Grid lines shall be established on no less than 50-foot
centers and run approximately north-south/east-west. Composite
samples shall be taken to a depth of 3 inches at each grid nodal
point. A total of 30 samples is estimated for one round of sampling
based on a 50-foot grid pattern. Samples shall be analyzed for
arsenic and CPAHs. Sample results will be used to determine the
extent of soil stabilization and asphalt capping for soil
contaminants that exceed cleanup standards set for soil at this site
(background for arsenic and CPAHs).
The background levels that have been identified at the Halby
Chemical Site for arsenic is 10 ppm and for CPAHs is 1.2 ppm,
however, these values were based on a limited number of samples.
Existing EPA guidance suggests that additional samples are necessary
in order to determine a statistically representative background value
for arsenic and CPAHs. A sufficient number of samples must be taken
to determine the value which will be used as the cleanup criteria for
both arsenic and CPAHs at the Halby Chemical Site.
The top six inches of contaminated surface soil will be excavated
from the areas found to contain contaminants at concentrations
exceeding the cleanup standards. The contaminated soil would be
mixed with stabilization agents to immobilize the contaminants of
concern and would be placed back into the process plant area. The
backfilled stabilized soil would be compacted to provide a firm sub-
base for the asphalt cap. The asphalt cap would cover all areas that
have been stabilized.
If it is determined (based on the sample results) that several
non-contiguous areas of the site need to be capped, efforts would be
made to consolidate the contaminated soil in the area north of the
railroad tracks which pass through the process plant area. The
reason for consolidating small areas of contaminated soil into this
area is the near certainty that this portion of the site would
require stabilizing and capping. The areas from which contaminated
soil was removed and relocated, would be backfilled to grade with
clean fill.
The asphalt cap would include a 3" gravel layer, and a 4" asphalt
aggregate mix. If the area used for truck access and parking is
further determined to require soil stabilization, the area would also
require some roadbed improvement. The maximum area that the asphalt
cap would cover is approximately 5,800 SY. Any structures and
outdoor equipment would be left intact. Prior to implementing this
alternative, a treatability study would be performed to identify a
proper stabilization formula.
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As discussed in Section 6 of this ROD, the risk assessment
assumed that the reasonably most exposed (RHE) concentration of
chromium in soil is in the hexavalent form (which is highly
unlikely). An incremental cancer risk of 2.5 x 10"4 was calculated ,-
for chromium in the inhalation pathway. The chromium is very likely
to be in the relatively harmless and noncarcinogenic trivalent form,
however, this must be confirmed in the field.
The alternative would also include deed restrictions, an air
sampling program, fencing, long-term monitoring, and five-year site
reviews. Some changes may be made to the selected remedy as a result
of the remedial design and construction processes.
a. Coat Breakdown
Capital Costs $ 891,000
Maximum Volume of Material 980 CY
to Stabilize
Unit Costs for Stabilization $ 87.31
of Material
Annual Operation & Maintenance Cost $ 43,400
5-Year Review Costs $ 10,000
Total Present Value Costs $ 1,586,000
b. Remediation Qoals and Performance Standards - The purpose of this
response action is to reduce the human health risks associated with
direct contact, ingestion and inhalation of particulates within the
process plant area (Operable Unit 1). Since no Federal or State
chemical-specific ARARs exist for contaminated soils at the Halby
Chemical Site, the cleanup levels for Operable Unit 1 will be
established based on the aforementioned current and future risk
values taking into account the background levels of contaminants
found in the area of the site.
The cleanup standards set for soil at the Halby Chemical Site are
background for arsenic and CPAHs. The background values that have
been identified through a limited number of samples are as follows:
Arsenic - background is approximately 10 ppm
CPAHs - background is approximately 1.2 ppm
Existing EPA guidance suggests that additional samples are necessary
in order to determine a statistically representative background value
for arsenic and CPAHs. Additional samples will be taken under the
selected remedy to allow EPA to determine the value which will be
66
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used as the cleanup criteria for both arsenic and CPAHs at the Hal by
Chemical Site.
The selected remedy would immobilize surface soil contaminated
above the cleanup goals, thus achieving the remediation goals. The
selected remedy would prevent direct contact with and ingestion and
inhalation of soil from the process plant area by stabilizing the top
six inches of contaminated surface soil and capping the treated soil
with an asphalt cap. This action would effectively eliminate the
risks associated with those pathways from the process plant area for
both the workers and residents. The selected remedy would also
provide risk reduction through institutional controls, public
education, fencing, and long-term monitoring. Additional future risk
to workers through direct contact and ingestion of exposed
contaminated subsurface soil would be eliminated by placing deed
restrictions on excavations in the plant area. The long-term
effectiveness of this remedy in minimizing human health risks through
the potential exposure pathways would depend on the integrity of the
cap. The useful life of the cap and fence is normally 30 years. The
level of effectiveness of this remedy would remain virtually the same
over this period. The cap would have to be maintained to prevent
degradation, and the fence and warning signs would have to be
maintained or replaced if damaged or stolen.
10. STATUTORY DETERMINATIONS
Under its legal authorities, EPA's primary responsibility at
Superfund sites is to undertake remedial actions that achieve
adequate protection of human health and the environment. In
addition, Section 121 of CERCLA, 42 U.S.C. S 9621, establishes
several other statutory requirements and preferences. These specify
that when complete, the selected remedial action for this site must
comply with applicable or relevant and appropriate environmental
standards established under Federal and State environmental laws
unless a statutory waiver is justified. The selected remedy also
must be cost-effective and utilize permanent solutions and
alternative treatment technologies or resource recovery technologies
to the maximum extent practicable. Finally, the statute includes a
preference for remedies that employ treatment' that permanently and
significantly reduce the volume, toxicity, or mobility of hazardous
wastes as their principal element. The following sections discuss
how the selected remedy meets these statutory requirements.
a. Protection of Huma** Health and the Environment The selected
remedy reduces the human health risks associated with direct contact,
ingestion and inhalation of particulates by immobilizing the
contaminated soil and containing the treated soil beneath an asphalt
cap. The selected remedy does not require that the process plant be
shut down yet it eliminates existing health risks to workers at the
Halby Chemical Site. The selected alternative reduces exposure
levels to within the 10 to 10"* risk range and the Hazard Indices
67
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for non-carcinogens to less than one. Deed restrictions and fencin
of the contaminated areas to limit site access would ensure that the
cap is not excavated or damaged.
Subsurface contaminants becoming mobile through groundwater
movement does not appear to be a problem based on information that
suggests that the groundwater moves directly into the Christina
River. Groundwater will be studied further in Operable Unit 2 for
this site.
There are no short-term threats associated with the selected
remedy that cannot be readily controlled. In addition, no adverse
cross-media impacts are expected from the remedy.
b. Attainment of the Applicable or Relevant and Appropriate
Requirements - The selected remedy will comply with all Federal and
State applicable or relevant and appropriate chemical-, location-,
and action-specific requirements (ARARs). Each of these categories
of ARARs is discussed below.
Chemical-Specific ARARs - There are no chemical-specific ARARs for
soil at the Halby Chemical site. The cleanup goals are derived based
on protection of human health. The selected remedy will immobilize
surface soil contaminated above the cleanup goals, thus achieving the
remedial objectives.
Location-Specific ARARs - The process plant area is not located in
100-year floodplain and is not a wetland. There are no known
endangered species living inside the plant area. There are no data
to indicate that the plant area contains any sites which may be
considered to be of historic or archeological significance. The
selected remedy therefore complies with all identified location-
specific ARARs.
Action-Specific ARARs - The action-specific ARARs for the selected
remedy are summarized in Table 11 as well as some of the design
considerations necessary to meet these requirements. The selected
remedy will satisfy action-specific ARARs.
Other Criteria. Advisorlea or Guidance To Be Considered for This
Remedial Action (TBCs) - Local deed restrictions.will be in place to
prohibit excavation and groundwater use for as long as concentrations
of hazardous constituents exceed health based levels. An ARAR to be
considered is the DNREC-Coastal Zone Act (ch.70, Sec 7001-1013).
This ARAR controls location, extent, and type of industrial t
development in Delaware's Coastal areas to protect the natural
environment. Although there is no intention to develop any new
industries at the Halby Chemical Site, the requirements of this ARAR
were considered when the selected remedy was chosen.
o. Cost-Effectiveness - The selected remedy is cost effective
because it has been determined to provide overall protectiveness
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Table 11
ACTION-SPECIFIC ARARS FOR SELECTED REMEDY
OPERABLE UNIT 1
HALBY CHEMICAL SITE
ARABS
STATUS
OSHA-General Industry Standards (29
CFR 1910)
Applicable
OSHA-Safety and Health Standards (29
CFR 1926)
OSHA-Record Keeping, Reporting and
Related Regulations (29 CFR 1904)
RCRA-Standards for Owners/Operators of
Permitted Hazardous Waste Facilities
(40 CFR 264.10-264.18)
RCRA-Preparedness and Prevention
(40 CFR 264.30-264.31)
RCRA-Contingency Plan and Emergency
Procedures (40 CFR 254.50-264.56)
DNREC Regulations Covering Hazardous
Substances Cleanups (Part IX, Ch.91 Sec
9101-9120)
Applicable
Applicable
Relevant And
Appropriate
Relevant And
Appropriate
Relevant And
Appropriate
Relevant And
Appropriate
REQUIREMENT SYNOPSIS
These regulations specify the
8-hour tine-weighted average
concentration for worker expo-
sure to various organic con-
pounds. Training requirements
for workers at hazardous waste
operations are specified in 29
CFR 1910.120.
This regulation specifies the
type of safety equipment and
procedures to be followed
during site remediation.
This regulation outlines the
record keeping and reporting
requirements for an employer
under OSHA.
General facility requirements
outline general waste analysis,
security measures, inspections,
and training requirements.
This regulation outlines the
requirements for safety equip-
ment and spill control.
This regulation outlines the
requirements for emergency
procedures to be used following
explosions, fires, etc.
Requires prompt containment and
removal of hazardous substances
to eliminate or minimize the
risk to public health or welfare
or the environment.
ACTION TO BE TAKEN TO ATTAIN ARARS
Proper respiratory equipment will be worn
if it is not possible to maintain the work
atmosphere below these concentrations.
All appropriate safety equipment will be on-
site and appropriate procedures will be
followed during treatment activities.
These regulations apply to the company(s)
contracted to install, operate, and main-
tain the remedy.
Facility will be designed, constructed, and
operated in accordance with this requirement.
All workers will be properly trained.
Safety and communication equipment will be
installed at the site. Local authorities
will be familiarized with the site.
Plans will be developed and implemented
during remedial design. Copies of the
plans will be kept on-site.
Hazardous substances will be contained or
removed promptly.
Ot
vo
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ARABS
STATUS
Table 11 (cant)
REQUIREMENT SYNOPSIS
ACTION TO BE TAKEN TO ATTAIN ARARS
CAA- NAAQS for Total Suspended
Particulatea (40 CFR 129.105, 750)
Relevant And
Appropriate
This regulation specifies maximua
and secondary 24-hour concentrations
for particulate Mtter. Fugitive dust
emissions fron site excavation
activities sust be maintained below 260
ug/m (prinary standards).
Proper dust suppression Methods such as water spray
would be specified when Implementing excavation and/or
stabilization actions.
40 CFR 262: RCRA Applicable
40 CFR 261: RCRA Applicable
40 CFR 264: Subpart L Applicable
40 CFR 264: RCRA Relevant And
Appropriate
40 CFR 50: NAAQS Applicable
DNREC-Regulatfons Governing the control Relevant And
of Air Pollution (Regulation Nos. 2. 3, 6 Appropriate
and 21)
ONREC-Environaental Control (Part VII, Relevant And
Ch. 60, Sec. 6003) Appropriate
DHUR-Chemical. Physical and Biological Relevant And
Treatment (Subpart 0, Section 265.400- Appropriate
404)
Establishes standards for generators of
hazardous wastes including waste deter-
mination. Manifests, and pre-transport
requirements.
Hazardous Waste determination.
Provides requirements to design and
operate waste piles.
Requires owner/operator to control wind
disposal of particulate matter.
Provides air quality standards for
particulate matter and lead.
Details the required permits, ambient
air quality, allowable dust control
during excavation activities and
emission standards.
Requires a permit if any contaminants
are discharged to the air, surface
water or groundwater.
Outlines operating requirements,
analysis and trail tests, inspections
and closures for hazardous waste treat-
ment processes.
This regulation will be applicable upon excavation and
on-site storage of site wastes.
Wastes will be compared to Federal Register listing to
determine if they are listed or characteristic wastes.
Performance standards would be specified for compliance.
Fugitive dust emissions will be controlled during implemen-
tation to maintain concentrations below these levels.
Same as below.
Proper dust suppression methods and monitoring will be
required when implementing excavation and/or stabilization
actions.
Practices will be followed to reduce potential emissions.
If discharges are anticipated, an application for a permit
will be submitted.
Required waste analysis, trail tests, inspections, closures
and operation procedures will be used during stabilization
treatment.
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Table
(cent)
ARABS
STATUS
DNREC - Delaware Erosion and Sediment
Control Handbook for Development (1989)
and Delaware's Erosion and Sediment
Control Law (Chapter 40. Title 7.
Delaware Code)
ROM-Landfills (40 CFR 264.310(a))
Relevant And
Appropriate
Relevant And
Appropriate
REQUIREMENT SYNOPSIS
ACTION TO BE TAKEM TO ATTAIN ARARS
RCRA-General Standards (40 CFR
264.117(0)
CAA-NAAOS for Participate Natter Less
than 10 Microns in Diameter (40 CFR Part
60, Appendix J)
CAA-NAAQS for Total Suspended Particulates
(40 CFR 2129.105.750)
Relevant And
Appropriate
Relevant And
Appropriate
Relevant And
Appropriate
Outlines Delaware Erosion and Sediment Reconaended practices Mill be followed during excavation. An
Control Law Regulations and practices to erosion and sediment control plan will be subaitted for
minimize erosion.
review and approval to comply with state erosion and sediment
control requirements for land-disturbing activities.
Placement of a cap over waste requires
a cover designed and constructed to:
- Provide long-tens minimization of
migration of liquids through the
capped area;
- Function with minimum maintenance;
- Promote drainage and minimize erosion
or abrasion of the cover;
- Accommodate settling and subsi-
dence so that the cover's Interity
is maintained;
- Have a permeability less than or
equal to the permeability of any
bottom liner system or natural sub-
soil present.
Restricts post-closure use of property
as necessary to prevent damage to the
cover.
This regulation specifies annual arith-
metic mean and maximum 24-hour concen-
trations for particulate matter.
This regulation specifies maximum pri-
mary and secondary 24-hour concentra-
trations for particulate matter. Fugi-
tive dust emissions from site excavation
activities must be maintained below 260
ug/m (primary standard).
Design considerations will include all requirements.
Post-Closure uses will be limited to those that will not
damage the cover.
Proper dust suppression methods will be employed to keep
concentrations below regulations.
Proper dust suppression methods will be employed to keep
concentrations below regulations.
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proportional to its cost. The present worth, calculated at a
discount rate of five percent, is $1,586,000. The estimated cost of
the selected remedy is approximately 28 percent of the cost
($5,610,000) associated with excavating the contaminated soils with-
off-site disposal, yet the selected remedy through immobilization of
surface soil contamination meets the cleanup goals, thus achieving
the remedial objectives. The estimated cost of the selected remedy
is approximately one half the cost associated with stabilizing the
soils with depth (costs of $2,700,000 are based on 2 foot depth
throughout area), yet both alternatives meet the cleanup goals but
leave contaminated subsurface soils on-site.
d. Utilization of Permanent Solutions and Alternative Treatment
Technologies (or Resource Recovery Technologies) to the Maximum
Extent Practicable - EPA and the State of Delaware have determined
that the selected remedy represents that maximum extent to which
permanent solutions and treatment technologies can be utilized in a
cost effective manner for this operable unit. Of those alternatives
that are protective of human health and the environment and comply
with ARARs, EPA and the State of Delaware have determined that the
selected remedy provides the best balance of trade-offs in terms of
long-term effectiveness and permanence, reduction in toxicity,
mobility, or volume achieved through treatment, short-term
effectiveness, implementability, cost, also considering the statutory
preference for treatment as a principal element and considering Stat~
and community acceptance.
The selected remedy will eliminate current risks to workers at
the site through stabilization of surface soil contamination and
offers a high degree of long-term effectiveness. The selection of a
treatment option is consistent with program expectations which
indicate that priority consideration for treatment of high
concentrations of toxic compounds is often necessary to ensure the
long-term effectiveness of a remedy. The selected remedy has
therefore been determined to be the most appropriate solution for the
Halby Chemical Site.
. Preference for Treatment as a Principal Element - By stabilizing
the contaminated surface soil within the process plant area, the
selected remedy addresses a principal threat posed by the site
through the use of a treatment technology. Therefore, the statutory
preference for remedies that employ treatment as a principal element
is satisfied. The selected remedy meets the statutory requirement to
utilize permanent solutions and treatment technologies to the maximum
extent practicable. *
The following changes have taken place since the Proposed
Remedial Action Plan was released on April 19, 1991:
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a. The Proposed Remedial Action Plan for Operable Unit 1
included remediation of the contamination in sediments and surface
water within the lagoon and drainage ditch next to the process plant.
EPA has decided that in order to gain more information regarding
tidal and groundwater movement in and out of the lagoon, tidal marsh
and drainage ditch areas, any actions with respect to the lagoon and
drainage ditch should be deferred to Operable Unit 2. As stated in
the Proposed Remedial Action Plan, Operable Unit 2 will also continue
to investigate contamination in the tidal marsh area, outfall area,
groundwater and air.
b. A soil grid sampling event was added as a requirement to the
selected remedy (Alternative S-4). This added requirement does not
change the objective of Alternative S-4, yet it provides a system by
which the extent of surface soil contamination within the process
plant area will be based.
EPA does not consider these changes to be significant since they
do not effect EPA's choice of a selected remedy for Operable Unit 1
which now only addresses the process plant area.
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RESPONSIVE SUMMARY FOR
OPERABLE UNIT 1
HALBY CHEMICAL SITE
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RESPONSIVENESS SUMMARY
HALBY CHEMICAL SITE
OPERABLE UNIT NO. 1
NEW CASTLE COUNTY, DELAWARE
A public comment period was held from April 19, 1991 through
June 3, 1991 to receive comments from the public on the Remedial
Investigation and Feasibility Study Reports, the Proposed Remedial
Action Plan, and EPA's preferred remedial alternative for Operable
Unit No. l of the Halby Chemical Site. Operable Unit No. 1 has
been redefined to include the process plant only. The lagoon,
plant drainage ditch, plant outfall area, and marsh area have been
deferred to Operable Unit No. 2. A public meeting for the Halby
Chemical Site was conducted on May 2, 1991 at 7:00 p.m. at the De
La Warr Community Service Center, New Castle, Delaware. The public
meeting was attended by EPA staff, members of EPA's contractor
staff, state regulatory representatives, PRP representatives, local
consultants, university students, area residents, and property and
business owners. The public meeting was preceded by a public
officials briefing held at 3:00 P.M. at the same location. The
briefing was attended by EPA staff, member's of EPA's contractor
staff, representatives of federal, state and local public offi-
cials, and by state and local regulatory representatives.
The purpose of the public meeting was to present and discuss the
findings of the RI/FS and to apprise meeting participants of the
EPA's preferred remedial alternative for Operable Unit No. 1 of the
Halby Chemical Site. Comments received during the public meeting
are summarized in Part 1 of this Responsiveness Summary and
categorized into the following topics:
A. Remedial Investigation
B. Risk Assessment
C. Remedial Alternatives Development and Selection
D. PRP and Financial Responsibilities
E. Other Concerns
In addition to comments made at the public -meeting, written
comments were received from the Potentially Responsible Parties
(PRPs) and the State of Delaware. Part 2 of this Responsiveness
Summary includes a brief summary of these written comments and
EPA's response. The written comments are categorized irito the
following topics:
A. Remedial Investigation
B. Risk Assessment
C. Remedial Alternatives Development and Selection
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PART 1
VERBAL COMMENTS RECEIVED DURING THE PUBLIC MEETING
A. REMEDIAL INVESTIGATION
A.I Comment:
EPA Response:
A.2 Comment:
EPA Response:
A.3 Comment:
A local consultant asked if both on- and off-site
investigations were undertaken during the RI/FS.
EPA stated that the RI/FS involved sampling soil,
surface water, groundwater, and sediment on and
near the site. The studies revealed that the con-
tamination problem is complex and that additional
studies would be necessary to plan remedial actions
for the affected areas. EPA concluded that two
operable units would be necessary at the Halby
Chemical Site to address the contamination issues.
Only the remedial alternatives for Operable Unit
No. 1 have been developed at this time. A separate
Proposed Plan will be issued when the studies
associated with Operable Unit No. 2 are completed.
(Note: The definition of Operable Unit No. 1 has
been revised after the public comment period. Only
the process plant is included in Operable Unit No.
1. The lagoon, plant drainage ditch, and plant
outfall area are deferred into Operable Unit No.
2.)
A university geology student asked if groundwater
monitoring wells were installed in the area as part
of the RI/FS, and/or if there are plans to install
wells for Operable Units No. 1 or 2.
Groundwater monitoring wells were installed as part
of the RI/FS to determine the nature and extent of
the contamination on or near the site, and to study
the geology and hydrogeology of the site. The
locations of these wells are shown in the RI/FS
report which is available for review at the
information repositories. Some of the monitoring
wells used were installed by the State of Delaware
and the City of Wilmington from previous investiga-
tions. EPA is considering installing additional
wells as part of Operable Unit No. 2.
A university geology student inquired about the
locations of the maximum concentrations of the
contaminants of concern in the tidal marsh area
(located in Operable Unit No. 2) and the depths of
the maximum concentrations.
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EPA Response:
A.4 Comment:
EPA Response:
A.5 Comment:
EPA Response:
In the tidal marsh area, the depth of the maximum
concentration levels vary by the contaminant.
During the RI/FS, a range of sediment samples were
taken: 0 to 20 inches; 0 to 30 inches; 0 to 60
inches; and 0 to 72 inches. In general, the great-
est concentrations of metals were found in the
deeper samples. This was particularly true for
arsenic, zinc, copper and lead. Detailed informa-
tion is found in the RI/FS report.
A local consultant inquired why the highest con-
centrations of zinc in sediments in the lagoon area
are found at the surface, whereas they are found
in the deeper sediment samples in the tidal marsh
area.
Sediment sampling in the lagoon area, the tidal
marsh area and the drainage ditch revealed in-
creased concentrations of zinc with depth in the
tidal marsh and drainage ditch areas, but in the
lagoon area the highest concentrations are at the
surface. Factors that may explain the phenomenon
include the tidal movement in and out of the study
area, possible deposition and movement of the upper
sediments in the area, and/or groundwater or some
type of sub-surface drainage remnant from histori-
cal facility operations. The data is inconclusive
and therefore, additional analysis will be required
as EPA proceeds with the studies for Operable Unit
No. 2.
A local consultant posed a possible explanation to
the variation found between the lagoon and tidal
marsh area for zinc concentrations: that the
particles in the tidal marsh were deposited with
erosion from the surrounding landscape and there
were higher concentrations of these contaminants
historically, and they have decreased with time,
which is why there is a decrease at the surface
samples. Whereas, in the lagoon there would be
less soil layering from erosion, so the contami-
nants would not be layered by more recent sedi-
ments and remain in the surface sediments.
EPA will continue to analyze the data and the
geologic and hydrogeologic conditions on- and
off-site as needed to identify the sources and
movement of contamination in areas included in
Operable Unit No. 2.
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A.6 Comment
EPA Response:
A local consultant inquired if sediment samples
greater than 72 inches in depth had been taken in
the tidal marsh area.
Sediment samples deeper than 72 inches were not
taken in the tidal marsh area. Only one of the
sediment samples taken in the tidal marsh area was
72 inches deep. EPA is considering the need for
additional sediment samples that are 72 inches or
deeper for Operable Unit No. 2.
B. RISK ASSESSMENT
B.1 Comment
EPA Response:
An area resident, representing a non-profit social
service/housing program, inquired about the health
of the employees who worked at the process plant
when chemicals were being processed.
The health risks to employees working at the Halby
Chemical Site between 1946 and 1977 when chemicals
were being processed is not known, nor will it be
assessed as part of this study. The risk assess-
ment conducted for the site does indicate that
currently there are unacceptable human health risks
due to direct contact, ingestion or inhalation of
contaminated soil.
C. REMEDIAL ALTERNATIVES DEVELOPMENT AND SELECTION
C.I Comment:
EPA Response:
C.2 Comment:
A local area resident asked if the preferred
alternative for Operable Unit No. 1 - surface soil
stabilization and asphalt cap - is a permanent
solution, given that the asphalt may crack at some
point in time.
The cost of the preferred alternative includes the
cost for long-term maintenance and monitoring.
The asphalt cap has an estimated useful life of
approximately thirty years* and may need to be
replaced in the future. The stabilized soils will
provide additional support for the asphalt cap to
reduce cracking or buckling. The stabilized soil
is expected to be effective for a period sig-
nificantly longer than 30 years. v
A property/business owner's representative in-
quired about the extent of the lagoon cleanup.
Would the cleanup stop at the property line or
would EPA clean up the tidal marsh area, the
Lobdell Canal and where the contaminants have
flowed.
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EPA Response:
C.3 Comment:
EPA Response:
C.4 Comment:
EPA Response:
C.5 Comment:
Operable Unit No. 2 will encompass both on-site
and off-site areas affected by contamination, in-
cluding the tidal marsh area east of the Halby
property.
A property/business owner's representative in-
quired about the potential for the contaminants in
the groundwater in the lagoon and tidal marsh area
leaching back and forth and potentially "undoing"
EPA's clean up efforts in the lagoon, if only the
lagoon is cleaned up at this time.
The Proposed Plan for Operable Unit No. 1 initial-
ly included the preferred remedial alternative for
the lagoon and drainage ditch area. The levels of
contaminants in the lagoon area surface sediments
are very high as opposed to those found in the
samples taken in the tidal marsh area. It is
thought that the majority of the contamination in
the lagoon is from historical surface deposition
in the lagoon rather than contaminants leaching
from the groundwater into the lagoon. Therefore,
separate cleanup activities could proceed in the
lagoon area while the tidal marsh area is being
studied further. However, based on public comment,
EPA has concluded that further hydrogeologic
studies of the lagoon and adjacent off-site areas
will be necessary to study the effects of ground-
water movement both on- and off-site. These
studies will be conducted as part of the remedial
investigation for Operable Unit 2.
A property/business owner's representative in-
quired about whether the preferred alternative for
the lagoon area (i.e., the soil barrier) would be
sufficient to stop the groundwater contamination
or would a liner also be required.
The soil barrier would not be sufficient to reduce
leaching. The effects of groundwater contamina-
tion from the lagoon area will be further studied
in Operable Unit No. 2, as described in EPA re-
sponse to C.3 above.
A property/business owner's representative in-
quired about the timing for the Operable Unit No. 2
investigations.
-------
EPA Response: The Operable Unit No. 2 investigations will be
continuing this year as part of the Halby Chemical
Superfund Site study process. The site was divid-
ed into two operable units so that cleanup activi-
ties for the process plant area could proceed while
further studies of the lagoon and tidal marsh area
are being undertaken.
C.6 Comment: A PRP inquired if the lagoon area becomes part of
Operable Unit No. 2, will the Superfund site name
change.
EPA Response: The site boundary of a Superfund site is not
limited by the property lines, but rather is
defined by the spreading limits of the contami-
nants. As such, the off-site tracking of contami-
nants from the Halby Chemical Site is considered
part of the Halby Superfund Site investigations.
It is not likely that Operable Unit No. 2 would be
renamed.
C.7 Comment: A local consultant inquired about whether the
plants in the re-established wetlands of the lagoon
(following cleanup) would root into the con-
taminated soil and disturb the sediment; and
whether frogs or turtles burrowing in the soil
would disturb the contaminated soil; and/or the
possibility of tidal action flushing away some of
the clean sediment and exposing some of the con-
taminated soil.
EPA Response: The lagoon area and EPA's preferred cleanup alter-
native (i.e., soil barrier) will be studied
further as part of Operable Unit No. 2. The
potential effects of vegetation and tidal action
on a soil barrier in the lagoon will also be
assessed. It is known that most plants in the re-
established wetland would be aerobic plants, with
their roots at the surface, thus reducing the
potential for sediment disruption. The effects of
burrowing frogs and turtles, although considered
insignificant, will also be reassessed. During
the predesign and remedial design studies, the
amount of clean soil fill that may be necessary to
isolate the contaminated sediments will be further
analyzed. Approximately one foot of clean soil
fill would be sufficient, based on studies to date.
However, the type of soil material and other
considerations will be evaluated further in light
of new data presented in Operable Unit No. 2.
Mechanisms to control the drainage flow in and out
of the lagoon to reduce sediment erosion will also
be studied.
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C.8 Comment:
EPA Response:
C.9 Comment:
EPA Response:
C.10 Comment:
EPA Response:
An area resident inquired about the length of time
estimated for the cleanup efforts at the Halby
Chemical Site.
The next phase for Operable Unit No. 1, following
the Record of Decision, is the negotiations with
the potentially responsible parties (PRP) for the
implementation of the remedial design and remedial
action called for in the Record of Decision. If
these negotiations are successful, they will result
in the entry of a Consent Decree between EPA and
the PRPs which would provide for performance of the
work. If no agreement is reached, EPA would
consider other options to have the work completed.
These would include performing the work with Fund
monies, or ordering the PRPs to implement the
remedy. It would be approximately two to three
years before remedial actions would be completed.
There is no estimated completion date for Operable
Unit No. 2 remediation.
A PRP inquired if the extra $400,000 between
Alternative S-3 (Capping Only) and Alternative S-
4 (Soils Stabilization/Asphalt Cap) is justified
if a crack in the asphalt is not going to be
patched in a timely manner.
Alternative S-4, the preferred alternative for the
process plant area, is considered cost effective
because the stabilization will provide an addi-
tional layer of protectiveness and serve as a base
for the asphalt cap. The firm base provided by
soil stabilization would reduce the number of the
potential cracks, thus reducing the overall opera-
tion and maintenance costs.
A PRP stated that if the soil in the process plant
area has been in place since 1946, not much shift-
ing should be expected.
There is likely to be differential settling once
the entire process plant area is capped. The
distribution trucks and vehicles entering and
exiting the process plant area are likely, to use
more of the paved area, which has not been histor-
ically used and therefore is less compacted, for
maneuvering. This is one of the reasons why it
would be prudent to stabilize the entire site for
the purpose of providing a firm base for the
asphalt cap. stabilization would also immobilize
heavy metals and therefore would provide added
protection to human health should the cap deterio-
rate.
-------
C.ll Comment:
EPA Response:
C.I2 Comment:
EPA Response:
A PRP inquired how the soil is stabilized. Is the
stabilized soil clean soil or is it contaminated
soil that is treated somehow and then compacted.
During the design phase, a treatability study would
be undertaken to determine what components or
materials, such as cement or asphalt or other mix
of chemicals and materials, should be used to
stabilize the contaminated soil.
A property/business owner's representative in-
quired about the remedial action objectives for
the drainage ditch area. Is the goal to remove,
treat or reduce the contamination level.
The drainage ditch will be studied further as part
of Operable Unit No. 2. The remedial action objec-
tives would be to prevent exposure to contaminated
sediments which would result in adverse environ-
mental impacts.
D. PRPs AND FINANCIAL RESPONSIBILITY
D.1 Comment:
EPA Response:
D.2 Comment:
A PRP inquired about who would be responsible for
the operation and maintenance cost of the asphalt
cap, when the cap's useful life is complete and
needs to be replaced.
A definitive answer to the question cannot be
given, due to the present and future variables
concerning financial responsibility for the clean-
up. The search for potentially responsible par-
ties will continue for the Halby Chemical Super-
fund Site, and negotiations with the PRPs may
determine who is going to pay for the cleanup and
the operation and maintenance cost. If negotia-
tions with the PRPs fail, then the cleanup may be
paid for by the Superfund Trust Fund, in whole or
part. The State of Delaware may also fund the
cleanup and/or the long term operation and main-
tenance cost. However, there is no statute that
automatically requires the State of Delaware to be
financially responsible for every Superfu^d site
within the state.
A PRP inquired about whether the owners of the
process plant would be responsible for replacing
the asphalt cap in 30 years, or whenever it needs
to be replaced, without the help of the other PRPs
identified for the Halby Chemical Site.
-------
EPA Response:
D.3 Comment:
EPA Response:
D.4 Comment:
EPA Response:
D.5 Comment:
Predicting who will be financially responsible for
replacing the asphalt cap thirty or more years from
now is not possible. It can be stated that long
term maintenance and monitoring of the asphalt cap
is necessary and repairs will be made as needed.
It is unlikely that EPA would walk away from this
site and the hundreds of other sites across the
country.
A PRP inquired about who would be financially
responsible for the on-site lagoon and drainage
ditch area if it is included in Operable Unit No. 2
with other off-site areas that may have different
PRPs. Does the Halby Chemical Site property owner
have to pay twice?
When a remedial action is to be taken at a Super-
fund Site, EPA searches for the PRPs, which in-
clude present and former property owners, opera-
tors, transporters, etc., for each specific ac-
tion. For Operable Unit No. 1, negotiations with
the PRPs for the process plant area would be
undertaken. For Operable Unit No. 2, negotiations
with the PRPs associated with the drainage ditch,
lagoon area and the tidal marsh area would com-
mence, whether they are the same or different PRPs
for Operable Unit No. 1.
An adjacent property/business owner stated that,
given the historical usage of the Halby Chemical
Site and the industrialized nature of the study
area, it would be difficult to put a complete
financial burden on the present and former owners
of the Halby Chemical Site for the cleanup, given
the potential contamination dumped into the water
over the years. If the lagoon is cleaned up
without addressing the potential contamination
sources from adjacent areas, then EPA is opening
a "Pandora's Box" of additional contamination.
It is known, based on the PRP investigations to
date, that other drainage lines have drained into
the lower tidal marsh area, from locations other
than the Halby lagoon area. During the ^studies
that will be undertaken for Operable Unit No. 2,
the PRP search will continue to identify all
possible contamination sources and those PRPs that
may be legally responsible for the cleanup.
A PRP inquired whether the 1-495 is considered to
be a "PRP11 in the sense that the runoff from the
highway may include contaminants that contribute
to the Halby site contamination.
-------
EPA Response:
Upgradient samples in the 1-495 runoff ditch were
taken to assess the potential contamination from
the 1-495 runoff. The levels of some of the metals
were lower than those found in the lagoon area.
Nevertheless, on-site migration of contamination
in the lagoon area will be studied in Operable Unit
No. 2.
E. OTHER CONCERNS
E.I Comment:
EPA Response:
E.2 Comment:
EPA Response:
A local consultant inquired about how the Halby
Chemical Site was selected as a Super fund site,
given the contamination on other properties in the
vicinity.
Potential Superfund sites are brought to EPA's
attention all the time. If, after preliminary
investigations, the site ranks high enough in the
Hazard Ranking System, then the site is listed on
the National Priorities List (NPL). The detailed
RI/FS studies are initiated, and the process
continues through to remediation, monitoring and
maintenance, and deletion from the NPL. In the
case of the Halby Chemical Site, it was necessary
to extend the study area to adjacent off-site areas
where contamination was found, to determine the
extent of contamination associated with the site
and other potential sources of contamination.
A PRP inquired about whether or not EPA was aware
that the plans to widen Terminal Avenue have been
roadblocked since 1987 due to the designation of
the Halby Chemical Site as a Superfund Site.
EPA is initiating the consultation process with
the State of Delaware, local transportation
agencies, and with Conrail (who would like to
construct railroad crossing gates on Terminal
Avenue), regarding the design of these transpor-
tation improvements.
10
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PART 2
WRITTEN COMMENTS RECEIVED DURING THE PUBLIC COMMENT PERIOD
(Note: The section and page numbers cited prior to the comment are
for the Remedial Investigation Report.)
A. REMEDIAL INVESTIGATION
A.1 Comment:
EPA Response:
A.2 Comment:
EPA Response:
A.3 Comment:
EPA Response:
A.4 Comment:
Section 2.1, pp. 1-2 Provide a review of the
aerial photos used in the RI report.
A review of the aerial photographs is provided in
the EPIC document.
Section 3.8.3 Provide more information on the
time of day and tidal cycle for water level mea-
surements .
Time and day of water level measurements are
provided in Table 2-14, Note 1. Tidal cycle
information was not recorded.
Section 4, pp. 4-11, 4-16, 4-44, 4-46, 4-47, 4-
48, 4-67, 4-72, 4-100, 4-101, 4-106, 4-130, 4-132,
and 4-151 The following contaminants were blank
qualified. State the reason for including the
contaminants in the assessment of site contami-
nants .
Methylene Chloride (SW, SED, SSS, GW)
Arsenic (SW, SED)
Acetone (SED, SSS, GW)
2-Butanone (SED, SSS)
bis(2-ethylhexyl)phthalate (SED, SSS)
Chloroform (GW)
Pg. 4-6 of the RI report discussed in detail the
procedures used for selecting chemicals that were
detected in the blank samples. In summary, if the
contaminant identified is a common laboratory
contaminant, the contaminant will be considered if
the sample concentration exceeds ten times the
blank sample concentration. This procedure is an
accepted EPA protocol.
Section 4.3.4, p. 4-18; Section 7.3, p. 7-1 The
surface water sample results do not concur with
the conclusion that arsenic has contaminated the
surface water of the 1-495 drainage ditch and tidal
marsh area.
11
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EPA Response:
A.5 Comment:
EPA Response:
A.6 Comment:
EPA Response:
A.7 Comment:
EPA Response:
A.8 Comment:
EPA Response:
The conclusion is based on the fact that arsenic
concentrations exceed the Federal Water Quality
Criteria, even though the arsenic concentrations
are below MCLs. A MCL is a drinking water stan-
dard which is not the situation for the surface
water.
Section 4.3.4, p. 4-19 The level of zinc in the
surface water sample collected from the pond near
the Forbes Steel Plant is not discussed.
The discussion of zinc contamination at SW-04 is
presented in Section 4.3.3, p. 4-16. The'bullet
item on p. 4-19 serves to point out the dissimi-
larity between contaminants on-site and off-site.
Section 4.3.5, Transverse #2 Figures Sample
location SW-04 is not provided on the plots for
Transverse /2.
The inclusion of sampling station SW-04 into the
plots will not change the conclusion. It will only
add to the complexity of the plots. It is
therefore not included in the plots.
Section 4.4.1, Table 4-5 Additional sediment
samples should have been collected at the back-
ground station to provide the change in concentra-
tion with depth.
The existing background sample has provided rea-
sonable background information for the remedial
investigation. EPA agrees that additional samples
at depth would provide greater details to back-
ground information. This recommendation will be
considered during Operable Unit No. 2 or remedial
design, if it is determined necessary.
Section 4.4.3, p. 4-50 -- .Only ranges of data
results were provided in the RI report. A table
of metal concentrations for off-site samples is
required.
A table of metal concentrations for off-s^te and
on-site samples can be found in Appendix A of
Volume II. These data were not repeated in the
text.
12
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A.9 Comment:
EPA Response:
A.10 Comment:
EPA Response:
A.11 Comment:
EPA Response:
Section 4.4.3, p. 4-51 The text states that two
samples collected from the coal and coke piles
contained negligible amounts of TCL metals and
therefore should not contribute significantly to
metals loading of marsh sediments. However, the
samples collected from the coal and coke piles
contained metals above background levels. The
statement regarding the level of contamination
affecting the Halby site is not supported by this
data. Detailed results of these samples should be
presented in a table.
The data for the coal and coke pile sampl-es were
summarized in Table 4-16 with detailed results
presented in Appendix A. As the data indicated,
the concentrations of metals in the coal and coke
piles are significantly less than the metal con-
centrations in the marsh sediment. For example,
the maximum arsenic concentration in the coal and
coke piles was 12 mg/kg. The arsenic in marsh
sediment ranges from 28 mg/kg to 1,400 mg/kg. The
coal and coke piles are therefore not a likely
source for the metal contamination for the marsh
sediment.
Section 4.4.5, p. 4-61; Figure 4-16 The RI
report states that arsenic concentrations increase
at station SED-24 in the tidal marsh. This state-
ment is misleading because the elevated concentra-
tion was from a depth of 6 feet and no other
samples discussed were collected below 2 feet. It
is not appropriate to compare sample data from
different depths.
The purpose of the discussion is to identify areas
that are above background and to provide an indi-
cation regarding the migration of contaminants,
regardless of the depth of samples collected. The
resulting figure clearly indicated that arsenic
has migrated off-site into the marsh area. It may
be warranted to collect additional sediment sam-
ples at depth in the marsh area to verify if other
locations are contaminated by arsenic at depth.
These studies are included in Operable Unit 2.
»»
Section 4.4.5.1, p. 4-75 The report incorrectly
states that 4.66 ug/kg of thiocyanate occurs at 6
inches when it really was detected at a depth of
6 feet.
The comment is correct. As a result of this
correction, thiocyanate concentrations did not
increase with depth.
13
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A.12 Comment:
EPA Response:
A.13 Comment:
EPA Response:
A.14 Comment:
EPA Response:
A.15 Comment:
EPA Response:
A.16 Comment:
EPA Response:
Section 4.5.1, p. 4-90 Sample SSS-13, together
with sample SSS-06, should be used as background
samples for soil at the site.
Inclusion of SSS-13 as part of the background
samples to compare the soil data would not change
the conclusions of the RI. The overall results
from SSS-06 and SSS-13 did not differ significant-
ly. None of the contaminants in these two samples
has any concentrations outside of the range of the
normal background (natural) soil.
Section 4, Tables 4-8, 4-10, 4-11, 4-13, 4-15
Sample qualifiers are not included for volatile
and semivolatile compounds.
The comment is correct. Data qualifiers "B" and
"J" are mistakenly omitted.
Section 4.5.2.2, p. 4-108 Station SSS-04 is not
located near the process plant outfall.
The process plant outfall is located near SED-03
through an underground pipe. SSS-04 is in the
vicinity of this outfall.
Section 4.7, p. 4-121 Wells W-03A and W-03B are
located too far northwest for use to characterize
upgradient water quality of the Columbia and upper
Potomac aquifers for the process plant.
The comment is correct. Wells W-03A and W-03B are
not directly upgradient of the process plant based
on the directions of the groundwater flows in the
Columbia and upper Potomac aquifers. However,
these wells did provide general background ground-
water information for the site as a whole. Addi-
tional wells may be warranted during remedial
design if remediation of groundwater is required.
Section 4.7.1.3, p. 4-132 The result of benzene
was not listed on Table 4-20 but was discussed in
the text.
^
Table 4-20 is a summary table for major contami-
nants only. Benzene was detected in only one
sample at a very low concentration and is there-
fore not listed. The result of benzene at W-01A
was listed in Appendix A.
14
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A. 1-7 Comment:
EPA Response:
A.18 Comment:
EPA Response:
A.19 Comment:
EPA Response:
A.20 Comment:
EPA Response:
A.21 Comment:
Section 4.7.1.3, p. 4-132 Vinyl chloride was
detected in one sample but absent from the dupli-
cate sample. Additional testing is requested to
verify the presence of vinyl chloride in well w-
04C.
Additional samples will be collected during Opera-
ble Unit No. 2.
Section 4.7.1.4, p. 4-133; Section 7.4, p. 7-2 -
- Tidal influence on groundwater movement should
be discussed.
The tidal influences on groundwater flow direction
are discussed in the USGS study included as Appen-
dix M.
Table 4-25, p. 4-149 Well W-01B is listed on
Page 2-34 as a well completed in the Columbia
aquifer. In Table 4-25, this well is included with
the upper Potomac wells.
Well W-01B is incorrectly listed on Page 2-35.
This well is constructed in the upper Potomac
aquifer.
Section 4.7.2.4.1, p. 4-154 The salt pile and
the Forbes Steel pond, instead of the old settling
lagoon, are the likely sources for contamination
in well W-02B.
Since W-02B is located off-site, it is not the
intention of this RI to identify the contamination
source(s) for this well. The report did not
indicate that the old settling lagoon is the source
of the Well W-02B contamination.
Section 5.3.3, p. 5-13 In Section 4, the detec-
tion of contaminants at station SW-08/SED-14 locat-
ed in the tidal marsh is explained as the result
of hydraulic connection between the western edge
of the tidal marsh and the on-site lagoon, while
the USGS study indicated that there is no hydrau-
lic connection. The coal and coke piles could be
responsible for contamination in the marsh.
15
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EPA Response:
A. 2 2 Comment:
EPA Response:
A.23 Comment:
EPA Response:
A.24 Comment:
EPA Response:
A.25 Comment:
As discussed in the responses to comments A.9 and
A.26, the coal and coke piles are most likely not
the source of metals and other inorganic contami-
nation for the marsh area. Even though the USGS
study indicated that there is no interaction
between the shallow groundwater and the surface
water for the general site area, the possibility
exists that there is an interaction between the
surface water at the marsh and lagoon. As a result
of this concern, further study is planned during
Operable Unit No. 2 to investigate this interac-
tion.
Section 7.1, p. 7-1 The summary and conclusions
text should also acknowledge that certain contam-
inants detected are not site related and that
neighboring activities are probably the source.
The purpose of the RI is to characterize the site
with emphasis placed on site-related contaminants.
All non-site-related contaminants are properly
discussed in Section 4 and are therefore not
repeated in the summary section.
Section 7.2, p. 7-1 The text should indicate
that the semivolatile compounds identified at
stations SSS-09 and SSS-17 were primarily PAHs and
several phthalate esters. The PAHs are not con-
sidered widespread site contaminants and were
detected in background sample SSS-13 and associat-
ed with the coal/coke pile. The majority of the
phthalate ester concentrations are blank quali-
fied.
The above concerns have been adequately addressed
in Section 4.5.2.1 and are therefore not repeated
in the summary section.
Section 7.3, p. 7-1 Manganese is not previously
discussed in Chapter 4 as being elevated in sur-
face water in the on-site lagoon.
Concentrations of manganese in the on-site lagoon
exceed the background concentration by an order of
magnitude. Discussion should have been included
in Section 4.
Section 7.3, p. 7-1 No mention is made that
carbon disulfide was detected on-site but that
there was none detected at stations in the tidal
marsh.
16
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EPA Response:
A.26 Comment:
EPA Response:
A.27 Comment:
EPA Response:
A. 28 Comment:
EPA Response:
A. 2 9 Comment:
EPA Response:
Extremely high concentrations of carbon disulfide
were detected in a sediment sample (SED-24) in the
marsh area.
Sections 7.3 and 7.4, p. 7-2 Runoff of water
used to wet the adjacent coal and coke piles to
control dust could be the source of the cyanide
detected at station SW-08 in the tidal marsh.
Also, PAH compounds were detected in the tidal
marsh at levels above those detected on-site and
the coal/coke piles should be acknowledged as the
probable source.
i
Total cyanide and PAHs were not detected in the
coal and coke pile samples. The coal and coke
piles are therefore not the likely sources of
contamination.
Section 7.5, p. 7-2 It should be stated that
the Columbia and upper Potomac aquifers are natu-
rally unsuitable for human consumption as a result
of elevated iron and manganese levels.
The discussion of water quality is presented in
Section 4 and is not repeated in the summary
section.
Section 7.5, pp. 7-2 and 7-3 In Section 7,
cadmium, chromium, and lead are discussed as site
contaminants that have contributed contamination
to the groundwater, but the RI report identifies
these metals as non-site-related and lists possi-
ble sources as Forbes Steel, the salt pile, and
the coal/coke piles. Also, the data indicates that
background and off-site concentrations exceed those
detected on-site.
The summary section did not state these metals are
site-related contaminants.
Section 7.6, p. 7-3 More detail should be pro-
vided to explain that the two bioassay stations
(BIO-03, 06) which demonstrated aquatic toxicity
from surface water were in the tidal marshland at
the confluence of the 1-495 drainage ditch and the
Christina River, respectively.
Details of the bioassay tests were provided in
Section 2.10, Section 4.8, and Appendix K. EPA
concurs that the statement should indicate the two
stations which showed aquatic toxicity were locat-
ed off-site.
17
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A.30 Comment
EPA Response:
A.31 Comment:
EPA Response:
A.32 Comment:
EPA Response:
Section 7.6, p. 7-3 In the last sentence, it
should be clarified that the inconsistencies were
in the mini-chronic toxicity test findings. As
the sentence reads now, the reader doesn't under-
stand that the 48-hour acute survival tests were
considered valid.
The testing protocols and results were presented
in Sections 2.10, 3.9, 4.8, and Appendix K. EPA
concurs that a clarification statement here will
be helpful.
Section 7.7, p. 7-3 The hypothetical future use
of groundwater from the shallow aquifer is unlike-
ly considering the naturally poor water quality
and that the City of Wilmington already supplies
potable water to this area.
According to the federal regulations, the ground-
water underneath the Halby Chemical Site would be
classified as Class IIA or IIB. Accordingly, there
is a potential that the groundwater could be used
as a potable water source. An existing on-site
well (IW-01) which is screened in the upper Potomac
aquifer was used as a cooling water source. It is
therefore feasible to use it for other purposes
such as showering. The proposed future use
scenario, while admittedly unlikely, is certainly
not impossible.
Section 7.7, p. 7-3 Based on ERM's review of
the results of the risk assessment, a strong case
could be made for the no action alternative or
limited no action alternative in the FS.
Issues relating to the development of alternatives
will be addressed in the responses relating to the
Feasibility Study. However, the Baseline Risk
Assessment prepared by EPA documents unacceptable
risks to workers in the process plant area, thereby
justifying the need to implement remedial measures.
B. RISK ASSESSMENT
B.I Comment:
EPA Response:
Review of the PHE was difficult because of the RI
organization.
The RI Report was prepared in accordance with the
standard organization for RI Reports contained in
EPA guidance.
18
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B.2 Comment:
EPA Response:
B.3 Comment:
EPA Response:
B.4 Comment:
EPA Response:
B.5 Comment:
The quantitative uncertainty analysis does not add
validity to the results, and adds another layer of
confusion.
The quantitative uncertainty treatment was re-
quested and participated in by the EPA Region III
risk assessment staff. The uncertainty approach
used is presented as an acceptable methodology in
the Risk Assessment Guidance for Superfund (RAGS),
and the EPA's contractor involved in the risk as-
sessment are recognized proficient practitioners
of uncertainty analysis.
Also, past attempts to deal with uncertainty in
risk assessment by calculating so-called "worst-
case" estimates have resulted in unreasonably high
upper bound estimates by use of a combination of
worst-case assumptions. This resulted in confu-
sion in interpretation of the risk assessment
results. The use of quantitative uncertainty
analysis serves to produce more reasonable upper
confidence level risk estimates.
Summary data tables were not provided showing valid
versus invalid samples. Also, non-detects were
included at one-half the analytical detection limit
for all classes of compounds. ERM's experience in
Region III is that the whole detection limit is
used for inorganics and PCB/pesticides.
All data evaluation objectives, approaches, and
results were discussed with and approved by EPA
Region III risk assessment staff, and are within
the guidelines presented in the RAGS.
Background levels are not presented in tabular
form; this would have been helpful.
Background levels were used properly in the evalu-
ation of the data, according to guidance provided
by the RAGS and the EPA Region III staff. While
including summary tables of background levels may
be helpful, this data is provided elsewhere in the
RI. v
No indication is given in the text whether or not
the concentration times toxicity screening tool
was used to screen compounds of concern for the
Halby Chemical Site.
19
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EPA Response:
B.6 Comment:
EPA Response:
B.7 Comment;
EPA Response:
The concentration times toxicity screening tool
was not used in the final screening for chemicals
of concern for the Halby Chemical Site. The RAGS
suggests that this tool be considered for use in
cases where there are an unmanageable number of
chemicals remaining after standard evaluation
criteria have been applied. This was not the case
for this risk assessment.
The use of 5 percent frequency of detection as a
screening criterion, rather than the more widely
accepted 25 to 50 percent, allows compounds fre-
quently detected as laboratory contaminants to be
selected as compounds of concern.
The use of 25 to 50 percent detection frequency as
a selection criterion is not widely accepted. The
RAGS present frequency of detection as an optional
criterion, to be used when the number of chemicals
involved is unmanageable. The RAGS further recom-
mend that the limits on exclusion of infrequently
detected chemicals be approved by the RPM. Addi-
tionally, a comparison to blank sample concentra-
tions was made in this data evaluation to account
for the possibility of common laboratory contami-
nation.
Non-site related compounds such as lead, zinc, and
PAHs were not considered separately in analyzing
risks from exposure to compounds from the site.
The compounds of concern included both non-site
and site related compounds.
If a contaminant's measured concentration was
elevated above it' a background concentration level,
then it was considered to be a compound of concern
in the risk assessment. There is insufficient
information available to exclude these compounds
as non-site related compounds.
B.8 Comment:
EPA Response:
From the information given in the text, it is
impossible to determine which compounds were
eliminated from the list of contaminants of con-
cern. If the toxicity times screening tool had
been used, a majority of compounds would have been
eliminated.
The general approach (per EPA guidance) used to
evaluate the data is explained on pages 6-4 and 6-
5 of the text.
20
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B.9 Comment:
EPA Response:
B.10 Comment:
EPA Response:
B.ll Comment:
EPA Response:
B.12 Comment:
In the PRP's consultant's judgment, the final com-
pounds of concern for this site would have been
limited to arsenic and carbon disulfide. Poten-
tial laboratory contaminants, such as acetone and
methylene chloride, should not have been consid-
ered. Compounds representing off-site sources
should be treated independent of those compounds
related to site activities.
If compounds were included in the risk assessment
that contribute little risk, then including them
would demonstrate if this is the case. Analyzing
all chemicals of concern to evaluate their contri-
butions to risk is an objective of the risk as-
sessment .
The inhalation of volatile contaminants through
the use of groundwater in the Columbia and Upper
Potomac aquifers in a (future) showering scenario
is stretching the hypothetical case because the
likelihood of use of these aquifers is extremely
low.
The current EPA guidance for risk assessments
(RAGS) specify that possible future land use
scenarios be identified for analysis, in consulta-
tion with the RPM. The EPA Region III risk as-
sessment staff and the RPM believe that the future
use of contaminated groundwater from these aqui-
fers by industrial workers for showering cannot be
reasonably eliminated as a possibility. A quanti-
tative evaluation of the likelihood of this scena-
rio is not possible but a judgment that it has
enough potential to merit inclusion in the analy-
sis has been made by EPA.
MCLs should not be applied to concentrations
detected at the site. It is more appropriate to
apply MCLs to estimates of discharges from the
aquifers to the Christina River..
The criteria shown in Tables 6-9 through 6-11 are
properly labeled as "potential ARARs." The EPA is
the final arbitrator of which ARARs will be applied
in the establishment of cleanup levels.
The current MCL for lead is 50 ug/L. Add a table
describing the groundwater and surface water
concentrations at the Christina River. Add a
strongly worded statement that indicates the
concentrations detected in groundwater are "real
concentrations only if someone is exposed".
21
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EPA.Response:
B.I3 Comment:
EPA Response:
B.14 Comment:
EPA Response:
The current MCL for lead is 15 ug/L. The impacts
at the Christina River are beyond the scope of this
PHE. An exposure pathway was considered complete,
in accordance with the RAGS, if the following four
elements were present: 1) a source and mechanism
of chemical release to the environment from the
site, 2) an environmental transport medium, 3) a
point of potential human contact with the contami-
nated medium, and 4) an intake mechanism at the
contact point. Table 6-11 should be changed to
show the MCL for lead is 15 ug/L.
Anthracene is a Class C carcinogen, and should not
be included in the risk assessment. The slope
factors used for carcinogenic PAHs are higher than
those documented in recent toxicological articles.
The basis for the toxicological criteria used for
PAHs is discussed on page 6-66, and was specified
by the EPA Region III risk assessment staff.
The highest uncertainty is in the toxicological
evaluation. Uncertainty in the toxicological
parameters were not included in the uncertainty
analysis in Section 6.7.
This observation is correct, and is stated in the
text.
B.15 Comment:
EPA Response:
B.I6 Comment:
EPA Response:
Site-specific exposure assumptions were not de-
fined because a range of assumptions were used.
The exposure assumptions ,as discussed in Section
6.6.2 of the Public Health Evaluation (Sept 1990),
were precisely specified in the analysis as
probability distributions.
Standard exposure assumptions from the Exposure
Factors Handbook (EFH) were not used consistently.
Some exposure assumptions were given as ranges from
pre-guidance document articles.
Every exposure parameter distribution was devel-
oped taking into consideration all pertinent
studies in the literature, including those that
form the basis of values recommended in the Expo-
sure Factors Handbook. Every exposure parameter
distribution contains the EFH values within its
range, but also accounts for the full range of
information available on the parameter.
22
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B.17 Comment:
EPA Response:
B.18 Comment:
EPA Response:
B.19 Comment:
EPA Response:
B.20 Comment:
EPA Response:
B.21 Comment:
EPA Response:
B.22 Comment:
For residential exposure, the text does not dis-
cuss the risk posed by exposures for 6-12 year old
children.
See Appendix 6-2 for Hazard Indices (His) for all
groups. As a general rule, His were presented for
the children's category showing the highest risk
(2-6 year old children).
The generic equation for ingestion given on page
6-71 has a component called FI which is not de-
fined in the text.
i
FI is the fraction of soil ingested from the
contaminated source, and is presented in the
generic equation for soil ingestion on page 6-73.
The value of this parameter was assumed to be 1.0
throughout the analysis, and is discussed on page
6-78 at the end of the first paragraph.
The modeling used to calculate exposure concentra-
tions for resuspended particulate matter and
volatilized compounds from the soil did not employ
the current USEPA Air/Superfund National Technical
Guidance Study Series documents.
While the guidance in the National Technical
Guidance Study Series was not used directly in this
assessment, the models which were used have been
reviewed and accepted by the EPA for risk assess-
ments. The Cowherd model and the box dispersion
model are recommended in the EPA Superf und Exposure
Assessment Manual.
The sediment data used in the risk assessment
appears to cover the full boring depth. The
concentrations should have been limited to shallow
sediments.
The distributions developed for exposure concen-
trations in sediment were based on shallow sam-
ples .
Justification was not given for using older draft
guidance documents in calculating particulate
emissions and volatile emissions from soils to air.
See EPA Response to Comment B.19.
More PAH compounds were used in the risk tables as
compounds of concern than were identified as
detected on-site in the Section 6.2 discussions.
23
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EPA Response:
B.23 Comment:
EPA Response:
B.24 Comment:
EPA Response:
B.25 Comment:
EPA Response:
As explained on page 6-66, the carcinogenicity of
PAHs were estimated using an approach suggested by
Thorslund (1988). Carcinogenic risks were as-
sessed for all compounds which were addressed in
that study. This resulted in the treatment of a
number of PAHs as carcinogenic, which IRIS and the
HEAST specify for non-carcinogenic treatment. The
result is the discrepancy between Table 6-1 and
the risk estimate tables for some PAHs. This
approach provides a less conservative estimate of
PAH-associated cancer risk than would be obtained
by applying the cancer potency slope factor for
BaP to all PAHs designated as "carcinogenic" in
Table 6-1.
Justification for the selection of the Foster and
Chrostowsi (1987) model for shower inhalation
exposures was not provided. No sample calcula-
tions or input variables were given.
The Foster and Chrostowski model was selected
because it is conservative, has been accepted by
the EPA in numerous risk assessments, and has been
validated by measurements. Sample calculations
have not been provided; however, the spreadsheets
are available from EPA and can be used to repro-
duce all calculations using LOTUS and §RISK.
Example calculations were not provided throughout
the document. Because of the uncertainty analy-
sis, verification of the calculations could not be
made.
Standard procedures were employed to assure the
quality of the calculations made in the risk
assessment. Sample calculations have not been
provided; however, all spreadsheets are available
from the EPA and can be used to reproduce all
calculations using LOTUS and 6RISK.
Summary intake tables were not provided as recom-
mended in the RAGS. Listed soil concentrations
were not specified as maximum or mean. An effort
was not made to lead the reader through these
tables.
The tables in Appendix 6-2 are functionally equiv-
alent to the tables recommended in the RAGS. Soil
concentrations shown are expected values.
24
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B.26 Comment:
EPA Response:
B.27 Comment;
EPA Response:
B.28 Comment:
EPA Response:
The concentrations of compounds used in this risk
assessment may not accurately represent exposure
levels. Invalid data were not specified and
arithmetic means were not calculated. Risk tables
do not specify whether a maximum or average con-
centration was used.
All valid data from the RI were used to develop
cumulative frequency distributions for contaminant
concentrations. In this manner, the concentra-
tions are precisely represented as distributions
which take into account all valid data. Tables in
Section 6.6 were used to report expected values
for contaminant concentrations. Tables 6-1 through
6-5 report the mean and maximum concentrations and
the detection frequencies.
EPA had calculated the risk posed by surface
sediments to trespassers as within the range of
10*6 to 10 . Ebasco calculated a cancer risk of
3x10 for adults occupationally exposed at the
site. Explain why the children (trespassers) had
less risk in the EPA calculations than adult
workers did in the Ebasco calculations.
The reason for the difference in risk results is
because of the exposure assumptions used in the
two calculations. The EPA calculations assigned
a very low exposure frequency for the trespassers
as there are little attractions in the lagoon. The
Ebasco calculations assumed that there will be work
performed in the lagoon. As a result, the worker
could be exposed to the sediment while performing
work in the lagoon. The exposure frequency and
duration would be much higher for a worker than a
trespasser. Consequently, the risk would be
higher.
The assumed use of the shallow aquifer is extreme-
ly hypothetical because ground water in the region
is not used as potable water by residential or
industrial areas. Therefore, the risk to someone
using the groundwater at the site should be negli-
gible. ^
The risk estimate for the future groundwater use
scenario is not negligible. The assessment of
hypothetical future land use scenarios is speci-
fied in the RAGS.
25
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B.29 Comment:
EPA Response:
B.3 0 Comment:
EPA Response:
B.31 Comment:
EPA Response:
The risk calculations based on ambient air moni-
toring data are not considered applicable because
the number of areal sources is varied. The com-
pounds detected during the air monitoring study,
in general, were not detected frequently or in all
media at the site, which indicates other sources.
This issue is discussed in the first paragraph on
page 6-23. The data may not provide a representa-
tive characterization of year-round air quality at
the site, and cannot be used to identify which of
the detected pollutants may be site-related.
The total hazard index for the groundwater expo-
sure scenario is 110, and is a direct result of
the carbon disulfide concentrations in the ground-
water samples. Again, this scenario is highly
unrealistic based on known groundwater use in the
area. Therefore, the hazard from groundwater
should be negligible.
See EPA Response to Comment B.28.
The quantitative uncertainty analysis is unwar-
ranted. A better use of time and dollars would
have been to calculate a reasonable or most proba-
ble case and a worst-case upper bound risk, as
discussed in the guidance document.
The guidance document (RAGS) does not recommend
estimating a worst-case upper bound risk. The RAGS
discusses calculating a Reasonable Maximum Exposure
(RME) with careful consideration given to charac-
terization of uncertainties in the risk assessment.
The quantitative uncertainty treatment was
requested and participated in by the EPA Region III
risk assessment staff. The uncertainty approach
used is presented as an acceptable methodology in
the Risk Assessment Guidance for Superfund (RAGS),
and the EPA contractor's staff members involved in
the risk assessment are recognized proficient
practitioners of uncertainty analysis.
Past attempts to deal with uncertainty in risk
assessment by calculating so-called "worst-case"
estimates have resulted in unreasonably high upper
bound estimates by use of a combination of worst-
case assumptions. This resulted in confusion in
interpretation of the risk assessment results.
The use of quantitative uncertainty analysis in
this PHE serves to produce more reasonable upper
confidence level risk estimates.
26
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B.32 Comment:
It is the PRP's consultant's professional judgment
that Section 6.7, Appendix 6.1, and Appendix 6.2
add little, if any, information to the overall
conclusion of the risk assessment.
EPA Response:
The quantitative treatment of uncertainty in this
risk assessment provided assurance that "best-
estimate" and upper and lower confidence level risk
estimates are reasonable and well-founded.
B.3 3 Comment:
EPA Response:
B.34 Comment:
EPA Response:
B.35 Comment:
The RI report indicated that the human health risk
caused by the soil and sediment is within the
acceptable risk range of 1x10"* to 1x10 . EPA
recalculated the risk caused by soil and sediment
exposure by using different and inappropriate
exposure assumptions. The reason behind the change
in the exposure assumptions is unclear.
The Ebasco risk assessment used geometric means of
the contaminant concentrations of the entire site
(process plant, lagoon and the other areas) for
the risk calculation. The method is appropriate
for the general population but was not adequate
for the plant workers, whom are restricted to the
process plant area most of the time. As a result,
EPA recalculated the risk for on-site workers based
on data from the process plant only, which is
representative of exposure for on-site workers.
The extreme values employed by EPA in estimating
frequency, duration, and amount of exposure are not
reasonable maximum values, as required by EPA
guidance.
The frequency, duration, and amount of exposure
are discussed in detail in the risk assessment
report. Per EPA guidance, the values range from
low frequency, short duration, and small exposure
to high frequency, long duration, and large
exposure. A probability value was assigned to each
value used to determine the likelihood of such
occurrence. ^
EPA's cleanup target for arsenic in surface soils
considered ingested arsenic as carcinogenic and
ignored RCRA and other Agency policies that treat
ingested arsenic as non-carcinogenic.
27
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EPA Response:
The risk assessment was prepared following the EPA
guidance for risk assessment in general and for
Superfund sites in particular. The cancer potency
factors were obtained from EPA's Integrated Risk
Information System (IRIS) database and the Health
Effects Assessment Summary Tables. It is not the
function of this document to resolve the discrep-
ancy between various EPA programs.
B.3 6 Comment:
EPA Response:
B.37 Comment:
EPA Response:
B.38 Comment:
EPA Response:
The RI conducted by Ebasco indicated the carcino-
genic and non-carcinogenic risk to fall within the
acceptable EPA ranges. Based on these risk1 calcu-
lations, no further remediation or limited remedi-
ation is warranted at the Halby Chemical Site.
The risk calculations performed by Ebasco were for
the whole site (including the areas occupied by
the warehouses). EPA has recalculated the risks
based on data within the process plant area. Both
calculations indicated that carcinogenic risks
exceeded the benchmark of IxlO*6 risk for on-site
workers. EPA's calculations indicated that the
plant area has cancer risks exceeding the EPA
acceptable range. As a result, remediation of the
process plant is warranted.
The risk calculations are a gross exaggeration of
the more realistic risks posed by the site. The
exposure assumptions are clearly ridiculous.
EPA established guidance and methodologies have
been closely followed when performing these risk
calculations. The assumptions used were either
established by EPA, other agencies, or generally
acceptable practices by the risk assessment pro-
fession. It is EPA's understanding that the
calculations should be conservative and, in some
cases, represent the worst case scenario.
The FS mentions that EPA recalculated dermal
contact, particulate inhalation, and ingestion
exposures to workers from compounds detected in
surface soils. EPA used different exposure as-
sumptions than Ebasco did in the 1990 risk assess-
ment. Appendix A in the FS report did not provide
the detailed assumptions used for these risk
calculations. Justification for this new risk
calculation and supporting documentation are
requested from EPA.
Supporting documentation has been made available
to the requester.
28
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B.39 Comment: a)
b)
EPA Response: a)
b)
The modeled inhalation hazard index for resi-
dential exposures was inadvertently reported
as 1.0. The calculated index from Ebasco's
report was 0.33.
Although the Hazard Index for surface soil
exposure is greater than 1, an effort was not
made to recalculate the HI according to the
same target organ effects, which is required
whenever the worst-case summed hazard exceeds
one.
This is a correct observation. The Hazard
Index for residential exposures from volatile
inhalation (modeled) has an expected value of
0.33, as shown in Table 6-43 or the RI. Table
1 of the PRAP should be corrected.
As shown in Table 6-43 of the RI, the expected
HI for the total of onsite surface soil expo-
sures for current land use scenarios is 1.5.
In the USEPA Risk Assessment Guidance for
Superfund (RAGS), guidance is provided that
when the total hazard index exceeds unity and
if combining exposure pathways has resulted in
combining hazard indices based on different
chemicals, one may need to consider segregating
the contributions of the different chemicals
according to major effect.
While this practice is recommended for the
characterization of risk, in the context of a
Feasibility Study to be protective of public
health it is prudent to set cleanup goals based
on keeping total hazard indices at less than
1.
C. REMEDIAL ALTERNATIVES DEVELOPMENT AND SELECTION
Soil Cleanup Levels;
C.i Comment:
In selecting the soil cleanup level, EPA did not
add to the background arsenic concentration, the 10
mg/kg level that causes (according to EPA) a
1x10 excess cancer risk.
29
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EPA Response:
C.2 Comment:
EPA Response:
EPA would like to clarify that the cleanup level
for arsenic which will be established for the Halby
Chemical Site will be based on background con-
centrations. Currently, the background concentra-
tion for arsenic, based on a limited number of
samples, has been estimated at 10 ppm, which
corresponds to a cancer risk of 1 x 10 . Addition-
al samples will be taken during predesign to
develop a more representative background value for
arsenic. The NCP mandates cleanup levels in the
range of IxlO'6 to IxlO"4, with IxlO"6 as the
benchmark. Since it is not practical to reduce
risk to below background, the background risk has
been selected as the cleanup target. The com-
menter has suggested that the value corresponding
to 10 excess cancer risk for arsenic be added to
the background value to determine the soil cleanup
level.
EPA would utilize the benchmark of IxlO*6 excess
cancer risk to determine an acceptable level of
incremental risk resulting from the site. This
would result in a total cancer risk of 1.1x10
(IxlO + IxlO*6) with a corresponding cleanup level
of 11 ppm (assuming the background concentration
for arsenic is confirmed to be 10 ppm). However,
as pointed out above and discussed in the FS report
(p. 2-28), the cleanup level should be the average
background level, not the upper bound of background
concentrations. The actual arsenic concentration
range may be from non-detect to several times the
background concentration. As a result, the 1 ppm
addition for the excess cancer risk becomes
meaningless as the cleanup level is based on sets
of sample results, not on a single value.
a) One commenter disagrees with the use of CPAHs
as chemicals of concern at the site.
b) The commenter stated that' 1.2 ppm could not be
the background concentration for PAHs. Also,
in deriving the 1.2 ppm cleanup level for PAHs,
EPA did not consider the background sample
taken near the asphalt plant (SSS-13).^
a) From Figure 1-10 of the FS report, there are
two locations (SSS-09 and SSS-17) that have
higher CPAH concentrations (by up to two orders
of magnitude) than the remaining areas of the
site and off-site, including the sample from
the asphalt plant. The level is likely a
result of manmade activities at these two
areas. Because of the high potency factors
30
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C.3 Comment:
EPA Response:
for the CPAHs, it is appropriate to include
these chemicals in the risk assessment.
b) The background concentration of 1.2 ppm of
CPAHs is derived by averaging four off-site
samples, which include SSS-06, SSS-13, SB-3,
and SB-4. As noted in the previous response,
additional samples will be taken during pre-
design to establish a more representative value
for background concentrations of CPAHs.
If the Ebasco risk calculations were used, in the
derivation of arsenic soil cleanup levels, a clean-
up level of 180 mg/kg for arsenic would have been
derived. The commenter performed calculations
based upon the use of appropriate reasonable
maximum exposure assumptions and a risk goal of
10 . These calculations yielded a value of 207
mg/kg arsenic for the worker scenario assuming
carcinogenic effects of arsenic through the soil
ingestion route.
Levels set for arsenic in surface soils at other
Superfund sites, the findings of ATSDR, the Wash-
ington State Cleanup Regulations, and the levels
proposed for the RCRA corrective action rule all
underscore the overly stringent nature of the
surface soil arsenic cleanup target of 10 mg/kg
for the Halby Chemical Site.
The risk assessment was performed using conserva-
tive assumptions and closely following the EPA
guidelines. However, as discussed in the response
to comment C.I above, the Ebasco risk assessment
used geometric means for the entire site. EPA
recalculated the risk using data from the process
plant, which is more closely related to the
existing situation.
As previously discussed, EPA intends to establish
the soil cleanup level for arsenic based on
additional sampling to confirm a representative
background value for arsenic. The arsenic cleanup
level for surface soil at the Whitmoyer Site is set
at background level, not at 2,836 mg/kg as cited
in the comment. The arsenic cleanup level for
contaminated soil at the Vineland Chemical Site was
set at 20 ppm, also similar to the level tentative-
ly identified for the Halby Chemical Site.
31
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Sediment Cleanup Levels;
C.4 Comment:
EPA Response:
C.5 Comment:
EPA Response:
EPA states that the National Oceanographic and
Atmospheric Administration (NOAA) has derived
cleanup levels for heavy metals in the lagoon
sediment. However, NOAA states that these values
are not to be construed as NOAA standards or crite-
ria. These values were used as informal guidelines
to rank sites with regard to relative potential
adverse effects at hazardous waste sites. NOAA
further states that the degree of confidence at the
low end of the range should be considered relative-
ly poor.
As indicated in Appendix B, the cleanup levels were
specifically developed by NOAA for the Halby Chemi-
cal Site based on toxic effects data gathered by
NOAA. Even though these values should not be
treated as standards or criteria, these values are
nonetheless "guidelines to be considered." These
values represent estimates of concentrations at or
above which adverse effects were often detected.
In the absence of established sediment criteria
and/or standards, it was the best professional
judgment by NOAA that the overall apparent ef-
fect's threshold could be recommended as target
cleanup levels.
EPA used the same cleanup level for lagoon sedi-
ments as for soils. This means that EPA assumed
that an individual would eat 100 mg of sediment,
located beneath plant discharge water, for 165 days
a year for a lifetime. This scenario is highly
unlikely.
The cleanup levels for soil and sediment were
developed independently. The soil cleanup level
was developed for protection of human health from
direct contact with contaminated soil. The sedi-
ment cleanup level was developed for protection of
human health as well as the environment (biota).
The evaluation process may look similar, but the
remedial objectives were treated separately for
the site soil and sediment.
Bioassav Investigationsi
C.6 Comment:
The following comments have been raised regarding
the bioassay investigation:
a) The organisms used in the test do not appear
to have been allowed sufficient time to accli-
mate.
32
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EPA Response:
b) Some mortality may have been due to factors
other than toxic responses such as widely
varying organic carbon levels in the samples.
c) High survivorship in the control may be relat-
ed to more favorable conditions and not the
absence of toxicity. No chemical or physical
data is provided to allow for this assessment
d) A comparison of on-site toxicity results to
upstream and downstream locations does not
reveal a contamination gradient. The. Chris-
tina River and the tributary which discharges
off-site drainage to the lower marsh are
causing greater toxic effects than the site.
This indicates that the other sources are more
toxic than the site.
e) The aquatic community could potentially pro-
vide more information on the impact of the site
than laboratory testing, especially considering
the variability of the lab results.
Since remediation of the lagoon has been deferred
to Operable Unit No. 2, these comments will be
addressed during the feasibility study for Opera-
ble Unit No. 2.
Other Technical Issues;
C.7 Comment:
EPA Response;
C.8 Comment:
EPA Response:
Only seven criteria were used in the analysis of
the alternatives instead of the stated nine crite-
ria in the FS report.
Seven criteria were used in the evaluation of
alternatives during the feasibility study. The
two remaining criteria, namely state and community
acceptance, were evaluated during the public
comment period. All comments received during this
period are considered prior to the issuance of the
Record of Decision.
The treatability study results demonstrate that
metals are relatively immobile and pose no signif-
icant risk to groundwater and surface water. The
treated soil samples leached more arsenic and other
metals than the untreated samples. This result
indicates that the proposed treatment of soil might
increase the mobility of arsenic and other metals.
The treatability study (TS) results did demon-
strate that metals in soil were relatively resis-
tant to TCLP leaching. However, the RI data also
33
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C.9 Comment:
EPA Response:
C.10 Comment:
EPA Response:
indicated that the surface water and groundwater
were contaminated by arsenic or other metals to
some extent. The treatability study demonstrated
that arsenic is relatively difficult to immobilize
using cement alone. However, some other binding
agents have been more successful in immobilizing
arsenic, as demonstrated in TS at other Superfund
sites. If stabilization is selected in the ROD,
a treatability study will be performed during the
remedial design phase to identify a proper formula
for immobilizing arsenic. It should be noted that
stabilization not only serves to immobilize heavy
metals, more importantly, it also serves to reduce
direct contact, ingestion, and inhalation of the
contaminated soil.
Based on the EPA's remedial action objectives, only
soil and sediment would require active reme-
diation. Groundvater, air, and surface water would
be remediated through source control or prevention
of exposure.
The remediation of contaminated soil within the
process plant will be addressed in Operable Unit
No. 1. The remediation of contaminated sediment,
groundwater, air, and surface water is deferred to
Operable Unit No. 2. Whether management of migra-
tion for groundwater, air, and surface water is
required or not will be determined during the
Remedial Investigation/Feasibility Study for OU-
2.
EPA considered a scenario to remove all contami-
nated soil by excavating down to the groundwater
table or five feet, whichever is less. Existing
tanks and equipment would be dismantled for dis-
posal to allow excavation to five feet. This
scenario is based on the potential future residen-
tial site usage. However, taking into account the
current usage of the site as an Industrial facili-
ty and the fact that the site is located in a
heavily industrialized area, the EPA scenario is
highly improbable.
^
It is EPA's belief that the scenario proposed is
not highly improbable given the fact that there
are currently residences (three trailer houses)
located within the site boundary. Furthermore,
residential communities are located in close
proximity to the site.
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C.ll Comment:
EPA Response:
C.I2 Comment:
EPA Response:
C.13 Comment:
The significant chemical reduction effect of the
tidal event has been ignored by EPA in the evalu-
ation of the remedial alternatives. It should be
noted that the tide causes significant daily dilu-
tion of the groundvater and surface water. This
effect, in combination with the fact that the
discharge of chemicals from the plant has stopped,
indicates that the concentrations of chemicals will
be declining with time. Therefore, five-year
reviews of the site in combination with institu-
tional controls would be the more appropriate
remedy for this site.
All site features, including the tidal event, have
been considered in the development of remedial
alternatives. As mandated by the NCP and CERCLA
as amended by SARA, EPA must evaluate a wide range
of remedial alternatives, including no action,
containment, and treatment action. As a result,
the five-year reviews in combination with institu-
tional controls, was evaluated in the limited
action alternative. The effect of tidal influence
has been considered for the remediation of surface
water. It is EPA's judgment that the limited
action alternative would not achieve the remedial
objectives.
On page 2-40 of the FS report, EPA makes a state-
ment that N[b]ut extended contact with soil vapors
or surface water would pose an unacceptable risk
level." This contradicts an earlier statement made
by EPA that "[Ajssessment of the risks posed by the
surface water in the lagoon indicates that there
is little cause for concern over adverse health
effects occurring as a result of dermal ex-
posure..."
The statement made on page 2-40 was referring to
a hypothetical site that is most suitable for
future use restrictions. It was not intended to
describe the Halby Chemical Site.
Page 4-3: "Additional threats to humans and the
environment may result from soil erosion which
could result in the exposure of more highly con-
taminated soil. This exposure could result in in-
creased risk to human health..." and page 4-10:
"...[m]ay result from soil erosion which could
result in increased risk to human health..." These
statements are totally contradicted on page 1-41:
"[I]f similar assumptions about the frequency and
duration of exposures to subsurface soil were made
as for exposures to surface soil, the resultant
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EPA Response:
C.I4 Comment:
EPA Response:
C.I5 Comment:
EPA Response:
cancer risks would be similar in magnitude, since
the geometric mean concentration of arsenic in the
subsurface soil (210 ing/kg) is very close to that
found in surface soil (250 mg/kg).n EPA makes
sweeping statements that have no technical basis
to justify remediation of soils at the site.
The geometric means used for risk calculations are
similar for surface soil and subsurface soil.
However, there were subsurface areas (e.g., SSS-
23 and SSS-25) with highly contaminated soil.
Should these areas be exposed, the carcinogenic
risks could increase.
EPA notes in Table 2-8 that the stabilization
process could be reversed under adverse condi-
tions. In other words, EPA has proposed a treat-
ment method for soil/sediment that is both unnec-
essary and of questionable long-term effective-
ness .
Since heavy metals are elements that cannot be
destroyed using conventional methods, the only
treatment technologies available are either con-
tainment or stabilization. Under the Resource
Conservation and Recovery Act, the Best Demon-
strated Available Technology for treatment of heavy
metals is stabilization. Since stabilization
involves physical and/or chemical bonding of heavy
metals only, this bonding can be reversed under
certain unfavorable conditions. A properly select-
ed immobilization agent would be able to withstand
most frequently encountered environmental condi-
tions without degradation of the product.
The FS failed to consider in the Identification
and Screening of Technologies section the capping
of soils by a soil cover (without any "treatment")
as a potentially applicable technology. This
technology would reduce dermal c.ontact and achieve
the same results as paving.
A soil cover for the process plant has been evalu-
ated in Section 2.4.2.3 (page 2-45). The soil
cover has been incorporated into Alternatives S-
3 and S-4 to supplement the asphalt cap for areas
that have little plant activity, are inaccessible
for equipment to place the asphalt cap, and areas
that are not suitable for the asphalt cap.
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C.l6 Comment:
EPA Response:
C.I7 Comment:
EPA Response:
C.18 Comment:
EPA is concerned about the presence of PAHs found
in only two soil samples at low concentrations;
however, the asphalt-based alternative will intro-
duce a significant amount of PAHs to the environ-
ment at levels that are probably much higher than
what are already present at the site.
The asphalt cap is designed to protect against
direct contact with arsenic and other heavy met-
als, as well as the two locations containing high
concentrations of "carcinogenic" PAHs.
The FS and the Proposed Plan state that' "[T]he
asphalt cap would require maintenance and possible
replacement in the future" (emphasis added) (page
12). Therefore, the cost for Preferred Alterna-
tive S-4 has been underestimated since the asphalt
cap replacement cost has not been considered.
A properly maintained asphalt cap could last 20 to
30 years. As such, the asphalt cap replacement
would be at the end of the 30 year period. The
replacement cost would be approximately $25,000
(2" wear coat), $50,000 (4" asphalt cap), or
$66,400 (cap and gravel base), depending on the
condition of the cap at the time of replacement.
The cost estimate for the FS is required to be
accurate to within +50% and -30%. The maximum
replacement cost of $66,400 is 4% of the $1.6
million cost estimate. It is therefore within the
guidance requirements.
a) The average arsenic soil contamination level
used for purposes of this risk assessment was
approximately 334 parts per million. Nine of
the eleven surface soil samples contained
arsenic in concentrations substantially lower
than 100 ppm. Sample point SSS-09, which had
an extremely high concentration of arsenic,
obviously contributed to .the high average
arsenic concentration. However, the laborato-
ry data reported that SSS-09 had an arsenic
concentration level of less than 1,130 ppm.
The data did not reflect how much less the
actual concentration was. Further study of the
arsenic concentration in surface soil at the
process plant area and recalculation of the
risk using the new data are therefore re-
quested.
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C.I9 Comment:
EPA Response:
b) Collect actual dust samples from inside and
outside the plant to test the assumption that
any dust ingested is generated solely from
soils within the process plant area.
c)
EPA Response: a)
b)
c)
EPA should reconsider the need for any remedi-
al action following recalculation of risk.
During remedial design, additional soil sam-
ples will be collected to refine the locations
within the process plant area which will be
stabilized and capped. EPA does not plan to
re-conduct the risk assessment unless there
are major changes in the sample results.
The majority (90%) of the carcinogenic risk is
from dermal contact and ingestion of the con-
taminated soil. Inhalation of dust particles
accounts for less than 10% of the risk. It
will be extremely difficult to make a conclu-
sive statement regarding the origin of the dust
particles, even with extensive sampling effort,
due to the variability of weather and plant
activities. EPA therefore has not planned to
sample dust particles.
There are provisions in the NCP to reconsider
the remedial action if there were major
deviations from the RI results. EPA does not
foresee this being the case for the Halby
process plant area. Therefore, there is
currently no plan to reconsider remedial action
at the site.
DNREC (Department of Natural Resources and Envi-
ronmental Control) of the State of Delaware recom-
mended that the lagoon and plant outfall area be
deferred to Operable Unit No. 2. The drainage
ditch should be remediated, together with the
process plant in Operable Unit No. l.
After discussion with the State of Delaware, EPA
has decided to defer the remediation of the la-
goon, plant outfall area, and plant drainage ditch
to Operable Unit No. 2. Operable Unit No. 1 only
includes the process plant. As a result of this
decision, all concerns regarding the remediation
of the lagoon, the plant outfall area, and the
drainage ditch from the State of Delaware will be
addressed during the execution of Operable Unit
No. 2 and will not be included in this responsive-
ness summary.
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C.2.0 Comment:
EPA Response:
C.21 Comment:
EPA Response:
C.22 Comment:
EPA Response:
C.23 Comment:
EPA Response:
C.24 Comment:
EPA Response:
C.25 Comment:
DNREC commented that the remediation of the pro-
cess plant needs to comply with certain state
ARARs.
The State of Delaware will have opportunities to
provide input to the remedial design. EPA will
ensure that state ARARs will be complied with.
DNREC has concerns that the results of the treat-
ability studies have been applied to new site
conditions.
EPA will attempt to resolve DNREC's concerns in
the treatability studies to be performed during the
remedial design for the process plant.
DNREC is concerned that the asphalt cap in Alter-
native S-3 will not have sufficient load bearing
capacity for the truck and forklift traffic.
If this alternative is selected, the asphalt cap
will be properly designed to withstand the traffic
load. A preliminary review of the load bearing
capacity did not indicate this to be a problem.
DNREC is concerned that there may be hexavalent
chromium in the plant soil to hinder the stabili-
zation process.
The selected remedy in the Record of Decision calls
for confirmation of whether the chromium is in the
hexavalent form or the trivalent form. If it is
confirmed that chromiun does exists in the
hexavalent form, a proper stabilization formula
will be selected.
DNREC is concerned that the clean fill proposed in
Alternative S-5 may be recontaminated by site
contaminants.
The process plant does not currently produce
chemicals. It receives bulk chemicals at the site
and distributes them to end users. Therefore, the
source of arsenic no longer exists. Oqce the
contaminated soil is removed from the site, there
will not be a source of arsenic to re-contaminate
the clean fill which is located in the unsaturated
zone.
DNREC has various concerns regarding the remedy
for the lagoon and drainage ditch.
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EPA Response: Since the remediation of the lagoon and drainage
ditch have been deferred to Operable Unit No. 2,
the concerns from DNREC will be addressed during
the execution of Operable Unit No. 2.
C.26 Comment: DNREC has recommended that EP toxicity tests be
performed on stabilized soil if it fails TCLP
testing. Such arrangement may avoid the need to
re-process the failed batch of soil.
EPA Response: EPA will consider such an arrangement during
remedial design.
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APPENDIX I
DESCRIPTION OF EVALUATION CRITERIA
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ALTERNATIVE EVALUATION CRITERIA
Overall Protection of Human Health and the Environment:
Addresses whether the remedy provides adequate protection and
describes how risks posed through each pathway are eliminated,
reduced or controlled through treatment, engineering controls, or
institutional controls.
Compliance vith ARARs: Refers to whether or not a remedy will
meet all Applicable or Relevant and Appropriate Requirements
(ARARs) of Federal and State environmental statutes and/or
provides grounds for invoking a waiver. It also addresses-
whether or not the remedy complies with advisories, criteria and
guidance that EPA and DNREC have agreed to follow.
Long-Term Effectiveness and Permanence: The ability of the
remedy to maintain reliable protection of human health and the
environment over time once the "clean-up" goals have been met.
Reduction of Toxicity, Nobility or Volume Through Treatment:
Relates to the anticipated performance of the treatment
technologies with respect to these criteria.
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 "clean-up" goals are achieved.
Implementability: The technical and administrative feasibility
of a remedy, including the availability of materials and services
needed to implement a particular option.
Cost: A comparison of the estimated capital, operation and
maintenance, and net present worth.
State Acceptancei This indicates whether, based on its review of
the FS, the Proposed Plan and public comments, the State concurs
with, opposes, or has no comment regarding the preferred v
alternative.
Community Acceptance: Views expressed by the community during
the Public Comment period are taken into account when identifying
the selected remedy.
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