United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R07-93/064
May 1993
c/EPA Superfund
Record of Decision
Chemplex II, IA
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50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA/ROD/R07-93/064
3. Recipient's Accession No.
THJ* and Subtitle
SUPERFUND RECORD OF DECISION
Chemplex II, IA
Second Remedial Action - Final
& Report Date
05/12/93
7. Authors)
& Performing Organization Rapt. No.
9. Performing Organization Nam* and Address
10 Project Tatk/Work Unit No.
11. Contract(C)orGrant(G)No.
(Q
(G)
12. Sponsoring Organization Name and Address
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
11 Type of Report & Period Covered
800/800
14.
1& Supplementary Note*
PB94-964309
16. Abstract (Umtt: 200 words)
The 700-acre Chemplex II site consists of a manufacturing plant and agricultural fields
located in Clinton, Iowa. The plant, located on approximately 230-acres of land, is
owned by the City of Clinton and enclosed by a fence. Land use in the area is
predominantly industrial, with agricultural fields surrounding the plant. Eleven.
potential areas of concern were identified from historical waste handling practices and
previous studies, which are identified as the Landfill, Debutanized Aromatic Compound
(DAC) Storage and Truck Loading Area, Polishing Basin, Previous Basin, Former Waste
Pile F, Surface Impoundment B, Surface Impoundment C, Surface Impoundment D, DAC Spill
Area, Former Container Storage Area H, and Unnamed Tributary to Rock Creek. From 1968
to 1978, the 7-acre landfill was used for disposal of various plant wastes generated at
the polyethylene manufacturing facility, including sludge, debris, scrap polyethylene,
and spent solvents. These wastes appear, in part, to have contaminated the soil and
ground water below the landfill. Much of the highly contaminated soil and debris in
the landfill will continue to leach into the ground water and potentially could be a
future contamination source for ground water. Currently, the contaminated soil and
'debris in the Landfill Area pose the principal threat because they contain high
concentrations of contaminants that are highly mobile due to landfill subsurface
(See Attached Page)
17. Document Analysis a. Descriptors
. Record of Decision - Chemplex II, IA
Second Remedial Action - Final
Contaminated Media: soil, debris
Key Contaminants: VOCs (benzene, PCE),
b. idertlfierm/Open-Ended Terms
COSAT1 Field/Group
other organics (PAHs)
ia Availability Statement
19. Security Class (This Report)
None
20. Security Class (This Page)
None
21. No. of Pages
52
22. Price
(Sea ANSt-Z39.l8)
So* Instructions on R»van»
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
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EPA/ROD/R07-93/064
Chemplex IX, IA
Second Remedial Action - Final
Abstract (Continued)
conditions. The proposed remedy includes treating vapors from the Soil Vapor Extraction
(SVE) system using a technology such as catalytic oxidation or carbon adsorption, as
determined during the remedial design phase. The contaminated soil, debris, and ground
water at the rest of the site present a relatively low long-term threat. A 1989 ROD
addressed ground water extraction and treatment throughout the site, as OU1. The design
of the system is currently ongoing and the system is expected to be operational in 1994.
This ROD addresses a final remedy for the contaminated soil and debris, as OU2. The
primary contaminants of concern affecting the soil and debris are VOCs, including benzene
and PCE; and other organics, including PAHs.
The selected remedial action for this site includes treating onsite 350,000 yd^ of
contaminated soil and debris using in-situ soil vapor extraction to remove VOCs; treating
the vapors onsite using catalytic oxidation or carbon adsorption; installing a multi-layer
cap over this area; capping the H-2 area of the DAC Storage and Truck Loading Area;
disposing of treatment residuals from SVE either onsite or offsite; establishing and
maintaining a vegetative cover in the Polishing Basin Area, Previous Basin Area, and
Former Waste Pile F to prevent exposure to damaged soil; placing warning sighs and fences
in these areas and in Surface Impoundments B and D; suppressing ground water in the
Landfill Area to facilitate operation of the SVE system; and implementing institutional
controls, including deed restrictions. The estimated present worth cost for this remedial
action is $11,409,000, which includes an estimated annual O&M cost of $32,702 for 2.5
years.
PERFORMANCE STANDARDS OR GOALS:
Chemical-specific soil cleanup goals will be based on MCLs from chemical data collected
during the Supplemental Endangerment Assessment (SEA), and include benzene 4,672.29 mg/kg;
CPAH 1,051.14 mg/kg; PAH 51,093.6 mg/kg; and PCE 118.85 mg/kg. The SVE process will attain
a 90-99% cleanup of VOCs as measured by in-situ gas concentrations. Detailed performance
criteria will be developed as part of the design process.
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RECORD OP DECISION
DECLARATION
SITE NAME AND LOCATION
Chemplex Site
Clinton, Iowa
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action
for the soils and wastes at the Chemplex Site located in Clinton,
Iowa. This decision was chosen in accordance with the
Comprehensive Environmental Response, Compensation and Liability
Act (CERCLA), as amended by the Superfund Amendments and
Reauthorization Act (SARA), and, to the extent practicable, the
National Contingency Plan (NCP). This decision is based on the
administrative record for this Site.
The State of Iowa concurs on the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from
this Site, if not addressed by implementing the response action
selected in this Record of Decision (ROD), may present a current
or potential threat to public health, welfare, or the
environment.
DESCRIPTION OF THE SELECTED REMEDY
Remedial action at the Chemplex Site is to be implemented
through a series of operable units. The first operable unit
consists of extraction and treatment of contaminated groundwater.
The Record of Decision for the first operable unit was signed on
September 27, 1989. That remedial action is being implemented by
a number of potentially responsible parties (PRPs) pursuant to a
judicial consent decree entered by the Federal District Court for
the Southern District of Iowa on November 7, 1991.
The second and final operable unit, which is the subject of
this Record of Decision, addresses threats posed by contaminated
soils and wastes at the Site. The contaminated soils and wastes
act as a source of groundwater contamination and also act as a
source for direct exposure to hazardous substances. The remedy
addresses principal threat wastes, which are the contaminated
materials in the Landfill Area of the Site, as well as the low-
level threat wastes at the rest of the Site.
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The major components of the selected remedy are:
groundwater suppression, soil vapor extraction (SVE),
and capping in the Landfill Area;
capping of the H-2 area of the DAC Storage and Truck
Loading Area;
establishment and maintenance of a vegetative cover
in the Previous Basin Area, Former Waste Pile F, and
Surface Impoundments B and D; and
institutional controls in all areas.
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the
environment, complies with federal and state requirements that
are legally applicable or relevant and appropriate to the
remedial action, and is cost-effective. This remedy utilizes
permanent solutions and alternative treatment (or resource
recovery) technologies to the maximum extent practicable, and
satisfies the statutory preference for remedies that employ
treatment that reduces toxicity, mobility, or volume as a
principal element.
Because this remedy will result in hazardous substances
remaining on the Site above health-based levels, a review will be
conducted within five years after commencement of remedial action
to ensure that the remedy continues to provide adequate
protection of human health and the environment.
/William W. Rice
" Acting Regional Administrator
U.S. EPA, Region VII
Dat
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RECORD OF DECISION
DECISION SUMMARY
CHEMPLEX SITE
CLINTON, IOWA
SOILS AND WASTES OPERABLE UNIT
Prepared by:
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION VII
KANSAS CITY, KANSAS
MAY, 1993
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RECORD OF DECISION
CHEMPLEX SITE
TABLE OF CONTENTS
SECTION PAGE
1.0 SITE NAME, LOCATION AND DESCRIPTION 5
2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES 5
3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION 10
4.0 SCOPE AND ROLE OF RESPONSE ACTION 10
WITHIN SITE STRATEGY
5.0 SUMMARY OF SITE CHARACTERISTICS 11
6.0 SUMMARY OF SITE RISKS 15
7.0 DESCRIPTION OF ALTERNATIVES 23
8.0 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES 29
9.0 SELECTED REMEDY 34
10.0 STATUTORY DETERMINATIONS . 38
11.0 DOCUMENTATION OF SIGNIFICANT CHANGES 41
FIGURES
Figure 1: Site Map 6
Figure 6.5.1: Summary of Potential Noncarcinogenic Risk 19
Figure 6.5.2: Summary of Potential Carcinogenic Risk 21
Figure 9: Area H-2 35
TABLES
Table 5: Maximum Concentrations of SOCs 14
Table 6.4: Potential Exposure Scenarios 17
RESPONSIVENESS SUMMARY
GLOSSARY 50-51
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DECISION SUMMARY
1.0 Site Name, Location and Description
The Chemplex Site is located approximately five miles west
of Clinton, Iowa, south of U.S. 30 and west of Route 67. The
700-acre Site includes the high-density and low-density
polyethylene manufacturing plant operated by Quantum Chemical
Corporation and the agricultural fields that surround the plant.
The plant itself is located on approximately 230 acres of land
enclosed by a fence. The plant has been in operation since
approximately 1967. The plant and the land on which it is
located are owned by the City of Clinton. Initially the City
leased the land to ACC Chemical Company and Getty Chemical
Company (ACC/GCC), who operated the plant until 1984. Quantum
currently leases the plant and the property, excluding a seven-
acre Landfill on the western portion of the Site, from the City
of Clinton. ACC/GCC retain their leasehold interest in the
Landfill.
As indicated on Figure 1, eleven potential areas of concern
(AOCs) at the Site were identified from historical waste handling
practices and/or previous investigations. These eleven areas
(study areas) were investigated during the Second Operable Unit
Remedial Investigation (SOURI) and are discussed in detail in the
Remedial Investigation (RI) and Feasibility Study (FS) Reports.
These areas are the Landfill, Debutanized Aromatic Compound (DAC)
Storage and Truck Loading Area, Polishing Basin, Previous Basin,
Former Waste Pile F, Surface Impoundment B, Surface Impoundment
C, Surface Impoundment D, DAC Spill Area, Former Container
Storage Area H, and Unnamed Tributary to Rock Creek.
2.0 Site History and Enforcement Activities
The Site has been the subject of a number of investigations
over the past several years. Initially, the investigations were
concerned with the Polishing Basin and the Landfill. The scope
of subsequent investigations was expanded to include the eleven
study areas. A brief description and history of each of these
eleven study areas is presented below.
2.1 The Landfill
The Landfill is located near the west-central boundary of
the fenced portion of the Site and covers approximately seven
acres. From 1968 to 1978, the Landfill was used for disposal of
various plant wastes generated at the polyethylene manufacturing
facility including black oily sludge, scrap polyethylene,
construction debris, carbonate sludge, and spent solvents. The
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Qua, iium
Fe :Uity
CONTAINER
STORAGE AREA H
LANDFILL AREA
suwAct
ENTO
SURFACE
IMPOUNDMENT*
UNNAMED TTHBUTARr
TO ROCK CREEK
SURFACE
IMPOUNDMENT C
DAC STORAGE A
TRUCK LOADING
DAC SPILL AREA
PREVIOUS KASIN
POLISHING KASIN
0 160
Scale in Feet
FIGURE I
On-Site Areas of Potential Concern- Chemplex Site: Clinton, Iowa''
6
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plant wastes have contaminated the soil and groundwater
underneath the Landfill.
2.2 The DAC Storage and Truck Loading Area
The DAC Storage and Truck Loading Area is an active
operation area that has been in use since the inception of
facility operations in 1968. The area measures approximately 500
feet by 800 feet and is used primarily for the storage and
transfer of debutanized aromatic compound (DAC), a by-product of
the polyethylene production process. DAC contains approximately
40% benzene, which is a hazardous substance, as well as other
volatile organic compounds. The area contains eleven above-
ground storage tanks, a transfer pump station, a truck loading
area and a rail tank car loading area, including a railroad track
that bisects the study area. Historically, this area was not
paved or otherwise protected from surface water infiltration, and
contamination of soils and groundwater occurred as a result of
spills of DAC product. However, subsequent paving and compaction
activities have reduced the potential for surface water
infiltration.
The area south of the railroad tracks is unpaved and is
bordered on its southern end by a french drain. The french drain
was installed voluntarily by ACC/GCC in approximately 1988 as an
interim groundwater recovery system to intercept Light Non-
Aqueous Phase Liquids (LNAPL) present as free product floating on
the ;water table. The french drain appears to be at least
somewhat effective in controlling LNAPL.
2.3 The Polishing Basin
This area is currently used by Quantum as a tertiary process
water treatment unit that receives process water from a
biological treatment unit. The Polishing Basin was originally
constructed with a bentonite-treated clay liner in 1968 and used
as a process water settling pond. In 1974, in conjunction with
construction of the wastewater treatment plant, the Polishing
Basin was dredged. During dredging, a backhoe apparently removed
a section of the clay liner. As a result of this damage to the
clay liner, contaminants leached into the soil beneath the
Polishing Basin.
In 1982, the Polishing Basin was drained. It was at this
time that the damage to the clay liner from the 1974 dredging was
discovered. The Polishing Basin was rebuilt with a new liner
consisting of compacted clay, bentonite, and a high density
polyethylene liner. A leachate collection system was also
installed that included a system of horizontal piping that
underlies the Polishing Basin. A french drain is located in the
ditch between the Polishing Basin and Hawkeye Road. An
additional groundwater recovery system is located downgradient of
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the Polishing Basin that consists of three french drains and two
collection wells.
2.4 The Previous Basin
The Previous Basin is a 1.1-acre area of the Site on which
was located a basin containing approximately 28,000 tons of oily
sludges. These sludges were dredged from the Polishing Basin in
1974 and placed in the Previous Basin. The sludges consisted of
the sediment from the settling of plant wastewater prior to the
construction of the wastewater treatment plant in 1974.
In 1987, the sludges in the Previous Basin were excavated
and removed from the Site. However, some residual contamination
remains in the soil.
2.5 Surface Impoundment B
This area is approximately 700 feet by 350 feet. The
impoundment was an engineered structure with a clayey silt liner
constructed in September 1982 to provide a drying basin for
sludges removed from the Polishing Basin. The Polishing Basin
sludges placed in Surface Impoundment B were tilled, allowed to
dry, and kept in place until 1985. In June 1985, the area was
excavated and the soils and sludges were transported to Former
Waste Pile F (described below).
2.6 Surface Impoundment C
This area is approximately 300 feet by 100 feet. The
impoundment was placed in service in 1980 for storage of non-
hazardous sludges generated by the process water treatment plant
thickener. In 1985, Surface Impoundment C was excavated and the
sludges and soil were transferred to Former Waste Pile F
(described below).
2.7 Former Waste Pile F
This area is approximately 800 feet by 300 feet. The area
was first used in 1977 for the storage of non-hazardous calcium
carbonate- and magnesium carbonate-rich sludges from the
facility's water treatment and wastewater treatment plants. In
1985-1986, sludges from Surface Impoundments B and C were
excavated and placed in Former Waste Pile F. In 1987, all
sludges in Former Waste Pile F were removed to an off-site
landfill and the area was backfilled.
2.8 Surface Impoundment D
The boundaries of this area are somewhat ill-defined. It is
approximately 300 feet by 150 feet. Surface Impoundment D was
placed in service in the Fall of 1979 to store non-hazardous
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thickener sludges from the process water treatment plant. This
impoundment was abandoned in 1983. The dried sludge was
landfarmed in place by plowing into the soil and has not been
excavated.
2.9 The DAC Spill Area
This area includes a DAC storage tank, a bermed area for the
tank, and the drainage ditch adjacent to the bermed area. In
March, 1982, a line from the DAC storage tank ruptured, spilling
approximately 37,000 gallons of DAC into the bermed area.
Although most of the spilled material was contained in the bermed
area and recovered, approximately 1,500 gallons escaped through
the. drainage pipe. Approximately 1,000 of the 1,500 gallons that
escaped were recovered with a suction truck. The remaining 500
gallons flowed south in a drainage ditch that eventually drains
into the Unnamed Tributary to Rock Creek, located on the western
portion of the Site.
2.10 Former Container Storage Area H
This area is approximately 25 feet by 100 feet. From 1968
to 1981, this area was used to store drums of chromium-bearing
catalyst after its use in the polyethylene manufacturing process.
Other materials stored in this area may have contained 1,1,1-
trichloroethane, tetrachloroethylene (PCE), cyclohexane, and
mono- and di-glycerides. The drums were reportedly removed from
the area in 1981.
2.11 Unnamed Tributary to Rock Creek
The Unnamed Tributary to Rock Creek drains the western
portion of the Site and flows south, draining into Rock Creek
approximately 2,200 feet south of the plant. Below the
confluence with the Unnamed Tributary, Rock Creek flows to the
east and then to the south. Approximately one and a half miles
southeast of the Site, Rock Creek flows adjacent to Hazel's Lake.
During high water conditions, the creek and lake are
hydraulically connected through a culvert. Rock Creek eventually
discharges to the Mississippi River approximately two miles south
of the Site.
2.12 Enforcement History
On September 18, 1987, EPA entered into an Administrative
Order on Consent with certain Potentially Responsible Parties
(PRPs), USI (now Quantum) and ACC/GCC, to investigate the
Landfill and DAC Storage and Truck Loading Area. The Consent
Order was issued pursuant to Section 106(a) of CERCLA,
42 U.S.C. §9606(a), and Section 3013 of the Resources
Conservation and Recovery Act, as amended (RCRA),
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42U.S.C. §6934. A summary of the results of this investigation
and other previous investigations is included in the RI/FS Report
that was completed by the PRPs in June 1989. With this
information and other documents available in the Administrative
Record file, EPA issued the first ROD for this Site in September,
1989, which selected groundwater extraction and treatment for the
Landfill and the DAC Storage and Truck Loading Areas. This ROD
was later modified by an Explanation of Significant Differences
(ESD) to include groundwater extraction and treatment for the
entire Site. The groundwater extraction and treatment remedy is
considered Operable Unit Number One (OU#1) for the Site and is
discussed in more detail in Section 4.0 of this document. These
documents are all available in the Administrative Record file for
OU#1.
At the time the first ROD for the Site was issued, EPA
determined that there was not sufficient information concerning
the nature and extent of soil contamination at the Site to select
a remedy. Therefore, on December 28, 1989, EPA entered into an
Administrative Order on Consent with the PRPs to conduct a Second
Operable Unit (OU#2) RI/FS. This Order was issued pursuant to
Sections 104(b) and 122(d) of CERCLA, 42 U.S.C. §§9604(b) and
9622(d). The RI was completed in June of 1992 and the FS was
completed in December of 1992. A Supplemental Endangerment
Assessment (SEA) and Treatability Study were also completed by
the PRPs. The results of all of the investigations to date are
summarized in these reports.
3.0 Highlights of Community involvement
The RI/FS Report and the Proposed Plan for the Chemplex Site
were released to the public for comment on January 23, 1993.
These two reports and the Administrative Record file were made
available for review in the Clinton and Camanche Public Libraries
and at the EPA Region VII offices at 726 Minnesota Avenue, Kansas
City, Kansas. The notice of availability for these documents was
published in the Clinton Herald on January 23, 1993. A public
comment period on the documents was held from January 23, 1993
through February 21, 1993. In addition, a public meeting was
held in Clinton on February 2, 1993. At this meeting,
representatives from EPA and the Iowa Department of Natural
Resources answered questions about the Site and the remedial
alternatives under consideration. Responses to the comments
received during the public comment period are included in the
Responsiveness Summary, which is part of this ROD. The decision
for this Site is based on the information contained in the
Administrative Record file.
4.0 Scope and Role of Response Action Within Site strategy
Remedial action at the Chemplex Site is being implemented
through a series of operable units, or discrete actions. The
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soils and wastes at the Site is driven by carcinogenic PAHs
(CPAHs). Therefore, the discussions of the nature and extent of
contamination at the study areas focus on the occurrence of the
following SOCs: benzene, PCE, PAHs and CPAHs.
Table 5 summarizes the maximum concentrations of SOCs found
at the Site for each study area in parts per million (ppm) . As
the table indicates, maximum contaminant concentrations in the
Landfill area are one to two orders of magnitude higher than
maximum concentrations at any other area at the Site. The
maximum concentrations of either benzene or PCE in any of these
other areas is 12 ppm, which is minimal when compared to the
Landfill. The maximum concentration of PAHs found in any of the
other areas except the Landfill is 3,821 ppm, and occurred in the
subsurface at Surface Impoundment B. Although this concentration
may seem high, PAHs are relatively immobile in the subsurface and
groundwater contamination is much more widespread for benzene and
PCE than it is for PAHs.
As discussed in the RI Report, the Landfill contains a total
of approximately 350,000 cubic yards of contaminated soils and
wastes including 104,000 cubic yards of contaminated plant by-
products and construction debris. This is in sharp contrast to
the ten other areas, where the total volume of contaminated soils
is approximately 20,000 cubic yards.
The contaminated soils and wastes in the Landfill Area pose
the principal threat to be addressed by this operable unit,
because they contain high concentrations of contaminants that are
highly mobile due to Landfill subsurface conditions. Much of the
highly contaminated soils and wastes in the Landfill are in
contact with bedrock and the groundwater. As a result,
contaminants from soils and wastes in the Landfill will continue
to leach into the groundwater and will act as long-term sources
of damage to groundwater unless they are addressed.
The contaminated soils and wastes at the rest of the Site
present a relatively low long-term threat. In the DAC Truck
Storage and Loading Area and the Polishing Basin Area,
considerable groundwater contamination exists. However, the
groundwater contamination appears to be primarily from historic
releases. Given the relatively low levels of contamination and
the low permeability of the soils in these areas, it appears that
significant leaching of contaminants into the groundwater is not
occurring and will not be expected to occur in the future.
In regard to all of the other areas of the Site, low
permeability soils have apparently restricted the movement of
SOCs and there is little or no groundwater damage in these areas.
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phasing of cleanup actions provides the opportunity to achieve
significant risk reduction more quickly than addressing the
entire Site at one time. The Chemplex Site cleanup consists of
two operable units.
The first operable unit remedial action addresses
groundwater at the Site. As mentioned earlier, the September
1989 ROD calls for groundwater extraction and treatment
throughout the Site. On November 7, 1991, EPA and certain PRPs
entered into a Consent Decree which requires the PRPs to design,
construct and operate the groundwater extraction and treatment
system. The design of the system is currently ongoing and the
system is expected to be operational sometime in 1994.
The purpose of OU#2 is to address contaminated soils and
wastes at the Site that present a threat to human health and the
environment from direct exposure or from indirect exposure
through migration of contaminants into groundwater. In concert,
OU#1 and OU#2 should address all human health and environmental
risks at the Site. The specific remedial action objectives for
OU#2 are:
1. Reduction of carcinogenic risk to on-site workers and
construction workers from direct dermal and inhalation
exposure to soils to a risk level of approximately 1 x 10"6
or less.
2. Reduction of migration of contaminants into groundwater to
the maximum extent practicable, consistent with the OU#1
groundwater remedy.
5.0 summary of site Characteristics
The nature and extent of soil contamination for the eleven
study areas are summarized below. This summary is based
primarily on data generated from the investigation performed by
ACC/GCC for the OU#2 RI. More detailed information regarding the
nature and extent of contamination can be found in the June, 1992
OU#2 RI Report, which is part of the Administrative Record file
and is available at the Clinton and Camanche Public Libraries.
Based on chemical data collected for soil and groundwater at
the Site and the analysis of soil data in the Supplemental
Endangerment Assessment (SEA), particular substances of concern
(SOCs) have been identified for the Site. Data indicate that
benzene and tetrachloroethylene (PCE) are SOCs because they occur
in the groundwater and soils at elevated levels. Within the Site
boundary, Polynuclear Aromatic Hydrocarbons (PAHs) occur at high
concentrations, particularly in association with separate-phase
Light Non-Aqueous Phase Liquids (LNAPLs). The SEA concludes that
risk to human health by direct dermal exposure to contaminated
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In the Unnamed Tributary to Rock Creek, PCE was detected at
the highest concentrations west of the Landfill at 232 parts per
billion (ppb) and west of the Polishing Basin at 56 ppb. Even at
its highest concentration in the tributary, PCE occurs at levels
below the EPA ambient water quality standard for PCE which is
considered safe for aquatic life.
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Study Area
Landfill
TABLE 5
Maximum Concentrations of SOCs (ppm)
Benzene PCE Total CPAH Total PAH
4,650.0 105.0
DAC Storage and
Truck Loading Area
Polishing Basin
Previous Basin
Former Waste Pile F
Surface Impound. B
Surface Impound. C
Surface Impound. D
DAC Spill Area
Former Container
Storage Area H
5.2
4.0
9.5
.09
1.2
1.2
ND
1.1
ND
.04
.2
12.0
.14
.26
1.2
.004
ND
.002
900.0 40,690.0
26.0
9.2
38.3
22.2
2.86
ND
.78
428.0
19.0 1,083.0
3,683.0
322.0
32.8 3,821.0
921.0
136.0
5.4
4.2
PCE = tetrachloroethylene
PAH = Polynuclear Aromatic Hydrocarbons
CPAH = Carcinogenic PAH
ND=Non-detected
14
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6.0 Summary of Site Risks
6.1 Overview of Baseline Risk Assessment
A baseline risk assessment was conducted to evaluate the
potential impacts to human health from exposure to hazardous
substances at the Site in the absence of remedial action. Risks
based on exposures resulting from both current and future land
use scenarios were evaluated. An ecological assessment was also
performed. This section summarizes EPA's findings regarding
risks to human health and the environment from exposure to
contamination in the soil at the study areas. The complete risk
assessment is presented in the Supplemental Endangerment
Assessment (SEA), dated May, 1992. This document is available in
the Administrative Record file. The assessment consisted of an
identification of chemicals of potential concern, toxicity
assessment, exposure assessment, and risk characterization.
6.2 Contaminants of Concern
The SEA compiled a list of contaminants of concern for each
study area from the results of the various sampling activities a_t
the Site. These indicator contaminants of concern were selected
based on concentrations at the Site, toxicity, physical/chemical
properties that affect transport/movement in air, soil and
groundwater, and prevalence/persistence in these media. These
contaminants of concern (as listed in Tables 2-4 through 2-14 of
the SEA) were used to evaluate potential health risks at the
Site. In general the contaminants of concern consist of volatile
organic compounds and base-neutral acids, including PAHs.
6.3 Toxicitv Assessment
The toxicity assessment characterized available human health
and environmental criteria for the contaminants of concern, and
qualitatively related potential chemical exposure (dose) to
expected adverse health effects (response). Included in this
assessment are the pertinent standards, criteria, advisories and
guidelines developed for the protection of human health and the
environment. An explanation of how these values were derived and
how they are applied is presented below.
Cancer slope factors (CSFs or potency factors), have been
developed by EPA's Carcinogenic Assessment Group for estimating
excess lifetime cancer risks associated with exposure to
potentially carcinogenic chemicals. CSFs, 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 CSF.
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Use of this approach makes underestimation of the actual cancer
risk highly unlikely. CSFs are derived from the results of human
epidemiological studies or chronic animal bioassays to which
animal-to-human extrapolation and uncertainty factors have been
applied.
Reference doses (RfDs) have been developed by EPA for
indicating the potential for adverse health effects from exposure
to chemicals exhibiting noncarcinogenic effects. RfDs, which are
expressed in units of mg/kg/day, are estimates of lifetime daily
exposure levels for humans, including sensitive individuals, that
are 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 soil)
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.
6.4 Exposure Assessment
Exposure pathways by which humans could be exposed to
chemicals of potential concern were based on reasonable
assumptions about current and future uses of the Site. Exposures
of four potential receptors were evaluated in the SEA: an on-
site worker, a trespasser, an off-site receptor, and an on-site
construction worker. In accordance with the NCP and Risk
Assessment Guidance for Superfund (RAGS), exposure scenarios
should be based on reasonable and not unlikely current and future
land use. A reasonable maximum exposure (RME) represents a
situation which is more conservative than an average case but is
not a worst case scenario. As explained in guidance published by
EPA in October 1988 for conducting an RI/FS, the RME scenario is
developed to reflect the types and extent of exposures that could
occur based on the likely or expected use of the site in the
future. A residential scenario was therefore not evaluated
because the Quantum facility is still in operation and the
property is likely to continue to be used for industrial use for
the foreseeable future. A summary of these receptor groups along
with the potential exposure pathways and current and future uses
is presented in Table 6.4.
6.5 Risk Characterization
The risk characterization quantifies present and/or
potential future risk to human health that may result from
exposure to the contaminants of concern found at the Site. The
site-specific risk values are estimated by incorporating
information from the toxicity and exposure assessments.
16
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TABLE 6.4
POTENTIAL EXPOSURE SCENARIOS EVALUATED AT THE CHEMPLEX SUE
OU-2 FEASIBILITY STUDY
CHEMPLEX SUPERFUND SITE
CLINTON. IOWA
1; POTENTIAL EXPOSURE
i PATHWAYS fPEPsi
.
Surrace Soii:
Lanaianon
1 Ineesnon
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Tnhaiannn
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ineesnon
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Suriace Water:
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RECEPTOR GROUPS
On-Site Tresoasser ; Off-Sits On-Site
Worker (C.T) Recector Ccnstnicnon
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17
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When sufficient data are available, two quantitative
evaluations are made: the incremental risk to the individual
resulting from exposure to a carcinogen; or, for noncarcinogens,
a numerical index or ratio of the exposure dose level to an
acceptable reference dose.
6.5.1 Risks From Noncarcinoaenic Compounds
The EPA has developed standards, guidelines, and criteria
that provide levels of intakes considered to protect human
populations from possible adverse effects resulting from chemical
exposures. A ratio of the estimated chemical chronic average
daily dose (CADD, sometimes referred to as the chronic daily
intake or GDI) to the RfD provides a numerical measure of the
potential that adverse health effects may result. This ratio is
referred to as the chronic hazard quotient (HQ).
The CADD equations were derived from actual Site data and
exposure assumptions based on EPA guidance documents. The RfD
values for a contaminant represent a level of intake which is
unlikely to result in adverse non-carcinogen health effects in
individuals exposed for a chronic period of time. The equations
and exposure assumptions for the CADD are presented in Appendix D
of the SEA. Sources of the RfD values include EPA's Integrated
Risk information System (IRIS) (U.S.EPA, 1992), and the Health
Effects Assessment Summary Tables (HEAST) (U.S.EPA, 1991). These
values are listed in Tables 4-1 and 4-2 of the SEA.
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. In general, hazard indices greater than one are
associated with potentially unacceptable health risk. As shown
on Figure 6.5.1, the baseline risk assessment indicates that
there are no waste-related compounds at any of the eleven study
areas that represent a potentially unacceptable non-carcinogenic
risk level.
6.5.2 Risks From Carcinogenic Compounds
For carcinogens or suspected carcinogens, a quantitative
risk assessment involves calculating risk levels considered to
represent the probability or range of probabilities of prescribed
exposure conditions. Carcinogenic risk estimates, expressed as
additional incidences of cancer, are determined by multiplying
the cancer slope factor (CSF) of the contaminant of concern by
the estimate lifetime average daily dose (LADD). The CSF values
for the contaminants of concern are based on information from
IRIS and HEAST and are presented in Table 4-3 of the SEA. The
LADD values are based on site-specific data and are calculated in
18
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FIGURE 6.5.1
SUMP 1 AH V Ml I1HKINIIAI, NIIINLiAKlHNUlilLlNll KISIV / S
OU-2 FEASIBILITY STUDY
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Appendix D of the SEA. It is the CSF, expressed in (mg/kg/day)'1
which converts the estimated LADD, expressed in (mg/kg/day), to
incremental risk. These risks are probabilities that are
generally expressed in scientific notation (e.g., IxlO"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 EPA generally considers as
being acceptable those concentration levels representing an
excess lifetime cancer risk of between 10~4 and 10"6 (or lower) .
Figure 6.5.2 presents the potential carcinogenic risk for the
various receptors in each of the eleven study areas. As this
figure indicates, all of the potential carcinogenic risks are
within the 10"4 to 10"6 risk range.
6.5.3 Environmental Evaluation
The SEA considered risk to aquatic receptors from exposure
to contaminants of potential concern in surface water, to
terrestrial receptors from surface soils, surface waters and
sediment, and to downstream ecosystems. The SEA also evaluated
the potential for critical habitats or endangered species to be
adversely affected by contaminants from the Site.
After considering, in accordance with EPA guidelines,
potential acute and chronic adverse effects to aquatic receptors
from exposure to the contaminants of potential concern, the SEA
found that there are no ecological risks of concern to aquatic
receptors. The hazard indices for two potential terrestrial
receptors evaluated indicated that there is a "possible concern"
related to noncarcinogenic exposure for moles ingesting
earthworms in Surface Impoundment B and for house sparrows
ingesting seeds coated with surface soil from Surface Impoundment
B. The SEA concluded, however, that due to the very conservative
exposure assumptions used and the resulting relatively low levels
of risk, neither of these receptors are expected to be adversely
affected by Site-related contaminants of concern.
The SEA further concluded that it is unlikely that there is
any risk from Site-related contaminants of concern to downstream
ecosystems since there is no unacceptable risk to aquatic
receptors in surface waters near the Site, and dilution of
contaminants is anticipated in both Rock Creek and the
Mississippi River. In summation, the SEA found that existing
conditions at the Site are protective of all potential ecological
receptors. Aquatic toxicity tests, stream evaluations and
terrestrial surveys were not performed because the evaluation
that was conducted addressed protection of all potential
ecological receptors.
20
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FIGURE 6.5.2
.>uivn»i/viv i VM1 i in_ KIOIV / y
OU-2 FEASIBILITY STUDY
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6.6 Uncertainties
Regardless of the type of risk estimate developed, it should
be emphasized that all estimates of risk are based upon numerous
assumptions and uncertainties. For example, in the Landfill
Area, where materials are extremely heterogeneous, uncertainty in
chemical data is heightened. There may be hot spots that were
not sampled, and thus exposure point contaminant concentrations
used in risk assessment may be low. Everything was done to
collect the best possible data (i.e. 95% confidence interval,
etc.), to reduce the likelihood of underestimating exposure
levels. Nonetheless, in areas such as the Landfill, potential
exposures may be higher than estimated in the risk assessment.
In addition to limitations associated with site-specific chemical
data, other assumptions and uncertainties that affect the
accuracy of the site-specific risk characterization result from
the extrapolation of potential adverse human effects from animal
studies, the extrapolation of effects observed at high dose to
low dose effects, the modeling of dose response effects, and
route-to-route extrapolation.
The use of acceptable levels (established standards,
criteria, and guidelines) and unit cancer risks which are derived
from animal studies introduces uncertainty into the risk
estimates. In addition, the exposure parameters used in
estimating chemical intakes are often associated with
uncertainties. As such, these estimates should not stand alone
from the various assumptions and uncertainties upon which they
are based. In developing numerical indices of risk, an attempt
is made to evaluate the effect of the assumptions and limitations
on numerical estimates. When the assumptions and uncertainties
outweigh the meaningfulness of a risk assessment, a qualitative
assessment of risk is performed.
Regardless of the uncertainties in the risk assessment,
there are high levels of contamination in the subsurface of the
Landfill that will act as a continuing source of groundwater
contamination if not remediated.
6.7 Conclusion
In conclusion, based on the results of the risk assessment,
EPA has determined that actual or threatened releases of
hazardous substances from this Site, if not remediated by the
selected alternative or one of the other active measures
considered, present a current or potential threat to public
health, welfare, or the environment.
In order to reduce all carcinogenic risks based on direct
exposure to a risk level of 10"6 or less, remedial action is
necessary in the Landfill Area, DAC Storage and Truck Loading
22
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Area, Previous Basin, Former Waste Pile F, and Surface
Impoundments B and D.
With regard to indirect exposure, the area of principal
threat is the Landfill area, where PCE-damaged soils will act as
a long-term source of groundwater damage unless they are
addressed.
7.0 Description of Alternatives
The alternatives evaluated in detail in the FS Report are
described below. This discussion identifies engineering and
treatment components, institutional controls, implementation
requirements, estimated costs, and major applicable or relevant
and appropriate regulations (ARARs) associated with each option.
7.1 Site-Wide Alternative 1 - No Action
Under this alternative, the Site would remain in its present
condition and no further action would be taken to reduce exposure
to Site contaminants or reduce migration of contaminants.
Although the no action alternative is not adequately protective
of human health and the environment, it is presented, as required
by the NCP, as a baseline for comparison.
The estimated total present worth cost for this alternative
is approximately $308,000 because of continued maintenance and 5-
year reviews that would be required.
7.2 Site-Wide Alternative 2 - Containment/Limited Action
This alternative includes containment for the Landfill Area,
the DAC Storage and Truck Loading Area, and the Polishing Basin,
and institutional controls in all areas.
The containment component consists of capping to eliminate
direct dermal exposure and cut-off surface water infiltration.
The cap in the Landfill would meet the State of Iowa's
requirements for closure of existing solid waste landfills
(I.A.C. Chapter 567-103, Subrule 103.2(13)), which are applicable
to the Landfill. This cap will also comply with certain relevant
and appropriate RCRA Subtitle C landfill closure requirements set
forth at 40 CFR §264.310. Specifically, relevant and appropriate
requirements are that the cap provide long-term minimization of
migration of liquids through the Landfill, function with minimum
maintenance, promote drainage and minimize erosion, and have a
permeability less than the natural soils present.
In the Polishing Basin and DAC Storage and Truck Loading
Areas, a cap would be installed in certain areas to reduce direct
contact threats and contaminant migration to groundwater. The
State of Iowa landfill closure requirements are not applicable in
23
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these areas, and the RCRA closure requirements are not relevant
and appropriate. However, these are operating areas at the
plant, and the cap would need to be constructed in a manner that
would ensure its long-term effectiveness.
A vegetative cover would be established and maintained at
the Previous Basin, Former Waste Pile F, and Surface Impoundments
B, C, and D. Groundwater suppression for all of these areas
would be included to inhibit migration of SOCs via groundwater.
Institutional controls would be used to supplement the
containment in order to further reduce exposure to contaminated
soils. Access controls, including a fence and warning signs,
would be put in place. Also, the Site is currently on the State
of Iowa Registry of Hazardous Waste or Hazardous Substance
Disposal Sites. Property on the Registry cannot be sold,
transferred, or conveyed, nor can its use be changed, without
written authorization from the Director of IDNR. Finally, deed
restrictions would be recorded with the local registry of deeds
which would prohibit activities at the Site which would disturb
the caps and vegetative covers.
Implementation time for this remedy is approximately six
months. The estimated capital cost for this alternative is
$5,226,000, the estimated annual O&M cost is $32,702, and the
total present worth cost for this alternative is approximately
$5,534,000.
7.3 Site-Wide Alternative 3 - Landfill SVE/Limited Action
This alternative utilizes soil vapor extraction (SVE) to
remove volatile organic compounds, including benzene and PCE,
from the Landfill. Use of SVE will also enhance the
biodegradation of PAHs by increasing the availability of oxygen
to subsurface soils. Based on the results of treatability tests,
SVE in the Landfill is expected to remove significant quantities
of volatile organic compounds (VOCs) and enhance biodegradation
of PAHs. The goal of the SVE treatment will be to remove greater
than 90% of the VOCs in the Landfill area. Contaminants
extracted from the Landfill would be captured and treated in
order to avoid cross-media impacts and short-term exposures to
nearby residents and workers. Catalytic oxidation and carbon
adsorption are types of treatment which could be used.
The soils and wastes in the Landfill are contaminated in
part as a result of disposal of spent solvents, which are listed
RCRA wastes. However, the spent solvent disposal occurred prior
to the 1980 effective date of RCRA, and thus RCRA regulations are
only potential ARARs for remedial activities which involve
treatment, storage, or disposal of these contaminated materials.
Since the SVE treatment would be performed in-situ, there are no
24
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applicable or relevant and appropriate RCRA requirements for the
SVE treatment.
This alternative also includes installation of a multimedia
cap in the Landfill. The cap would comply with the State of Iowa
requirements for closure of solid waste landfills and the
relevant and appropriate RCRA Subtitle C landfill closure
requirements described for Alternative 2.
In study areas other than the Landfill, Alternative 3 is the
same as Alternative 2, including capping, groundwater
suppression, and institutional controls.
Implementation time for this remedy is approximately thirty
months. The estimated capital cost for this alternative is
$11,101,000, the estimated annual O&M cost is $32,702, and the
total present worth cost for Alternative 3 is approximately
$11,409,000.
7.4 Site-Wide Alternative 4 - SVE/Limited Action
Alternative 4 is identical to Alternative 3 with the
exception of an SVE component being added in the DAC Storage and
Truck Loading Area and in the Polishing Basin.
SVE would be utilized in select areas in the DAC and
Polishing Basin Areas to remove contaminants from LNAPL-smeared
soils. Treatability tests indicate that SVE in these areas would
remove and destroy some contaminants. However, the extent to
which SVE can be used in the DAC and Polishing Basin Areas is
limited because existing facility operations make some of the
contaminated soils inaccessible. In addition, the effectiveness
of SVE in the DAC and Polishing Basin Areas, as opposed to the
Landfill, is uncertain due to the low permeability of soils in
these areas. °
Implementation time for this remedy is approximately thirty
months. The estimated capital cost for this alternative is
$14,115,000, the estimated annual O&M cost is $32,702, and total
present worth cost for Alternative 4 is approximately
$14,424,000.
7.5 Site-Wide Alternative 5 - SVE/Excavation/Limited Action
This alternative incorporates SVE in the Landfill, DAC
Storage and Truck Loading Area, and Polishing Basin. It also
includes excavation of certain contaminated unsaturated soils in
the DAC Storage and Truck Loading Area which are in areas not
amenable to SVE. Approximately 4300 cubic yards of contaminated
soil would be excavated. Excavation would be done manually due
to the presence of pipelines, pumps, and utilities in the area.
25
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The excavated soils would be consolidated in the Landfill for
subsequent SVE treatment.
The contaminated soils in the DAC area, unlike the Landfill,
are not contaminated with RCRA listed wastes. Therefore, RCRA
requirements would only be applicable to the handling of
excavated DAC Storage and Truck Loading Area soils if the soils
exhibit a characteristic of hazardous waste pursuant to 40 CFR
Part 261. Based on the RI data, some of the contaminated soils
may contain benzene at high enough .concentrations that the soils
might exhibit the characteristic of toxicity for benzene.
Excavated soils would undergo Toxicity Characteristic Leaching
Procedure (TCLP) analysis, and if the analysis indicates that
they are a characteristic hazardous waste, RCRA regulations would
be applicable to handling of such waste.
The other components of Alternative 5 are identical to those
included in Alternative 3, including capping in the Landfill, DAC
Storage and Truck Loading Area, and Polishing Basin Areas
following SVE treatment, vegetative cover in the Previous Basin,
Former Waste Pile F and the Surface Impoundments, institutional
controls in all areas, and groundwater suppression in all areas
other than the surface impoundments.
Implementation time for this remedy is approximately thirty
months. The estimated capital cost for this alternative is
$14,846,000, the estimated annual O&M cost is $32,702, and the
total present worth cost for Alternative 5 is approximately
$15,154,000.
7.6 Site-Wide Alternative 6 - Landfill Bioremediation/SVE or
Excavation/Limited Action
This alternative incorporates SVE, excavation and ex situ
bioremediation in the Landfill. It also includes partial SVE,
partial excavation and containment in the DAC Storage and Truck
Loading Area, SVE and containment in the Polishing Basin,
containment, including capping, in the Previous Basin, and a
vegetative cover and access controls in Former Waste Pile F and
the Surface Impoundments. Groundwater suppression is also part
of this alternative.
All Landfill materials would undergo SVE treatment, followed
by excavation and on-site bioremediation in a prepared bed
reactor. Approximately 350,000 cubic yards of material would be
excavated and treated. The treated materials would then be
replaced in the excavated area and a vegetative cover would be
established.
The SVE system would be designed and operated as described
for Alternative 3. Upon completion of SVE, the SVE system would
be dismantled and contaminated Landfill materials excavated and
26
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prepared for bioremediation. Materials handling treatability
tests indicate that excavation and preparation of the materials
can be accomplished using commercially available equipment, but
considerable technical difficulties are likely to be encountered
due to the heterogeneity of the materials and the high
concentrations of contaminants in the materials. Rigid controls
would be necessary to protect workers and nearby residents from
exposure to contaminants during excavation and material
preparation activities.
The soils and wastes in the Landfill are contaminated with
PCE as a result of the disposal of spent solvents. The RCRA
status of these contaminated soils and wastes is governed by
EPA's "contained-in" policy, which states that any mixture of a
soil and a RCRA listed waste must be managed as a hazardous waste
as long as the soil "contains" hazardous constituents above
health-based levels. The health-based level for PCE for purposes
of this remedial action is 5.6 ppm. Thus, if after SVE treatment
the excavated Landfill materials contain PCE at concentrations
above health-based levels, they must be managed as RCRA wastes.
This means that the RCRA requirements for design and operation of
treatment units would be applicable to the bioremediation
treatment unit, and that any storage of excavated materials prior
to bioremediation would have to comply with RCRA storage
requirements.
In addition, the RCRA land disposal restrictions of Part 268
would be applicable if the concentrations of PCE in bioremediated
soil are greater than 5.6 ppm. The land disposal restrictions
require that the bioremediated soil cannot be redeposited in the
Landfill area until either TCLP analysis of the soils shows that
PCE concentrations are reduced to less than .05 ppm, or a
treatability variance is obtained.
Bench-scale treatability test data indicate that
bioremediation would likely be effective in destroying residual
VOCs and PAHs remaining in the soils after the SVE treatment to
levels below health-based concentrations. However,
bioremediation is a relatively innovative technology, and pilot-
scale testing would probably be necessary in order to accurately
determine its feasibility and effectiveness. If the residual
levels of PCE in bioremediated soil are below 5.6 ppm, the soil
can be redeposited in the Landfill with only a vegetative cover.
However, if they are not below 5.6 ppm, RCRA Subtitle C landfill
closure requirements would be applicable.
Monitoring of air emissions during bioremediation would be
performed, and emission controls would be put into place as
necessary to avoid cross-media impacts and protect human health
and the environment. The need for such controls would be
evaluated during the pilot-scale testing.
27
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In the DAC Storage and Truck Loading Area, limited SVE would
be performed, as in Alternative 5. Limited excavation of
contaminated materials would also be done, with the excavated
materials being treated in the bioremediation unit. At other
areas of the Site, Alternative 6 is identical to Alternative 5.
Implementation time for this remedy is approximately
seventy-two months. The estimated capital cost of this
alternative is $94,423,000, the estimated annual O&M cost is
$25,116, and the total present worth cost for Alternative 6 is
approximately $94,660,000.
7.7 Site-Wide Alternative 7 - Landfill
Incineration/Bioremediation
This alternative incorporates treatment for all areas at the
Site. It includes SVE followed by excavation and on-site
incineration of 350,000 cubic yards of material from the
Landfill, relocation of Quantum operations at the DAC Storage and
Truck Loading Area and Polishing Basin followed by excavation and
bioremediation of all contaminated soils in these areas, and
excavation and bioremediation of contaminated soils in the
Previous Basin, Former Waste Pile F and the Surface Impoundments.
In the Landfill Area, SVE treatment would be followed by
excavation and preparation of the Landfill materials for
incineration. RCRA regulations for treatment and storage would
be applicable to such activities if the excavated materials
contain PCE at concentrations above the health-based level of 5.6
ppm.
RCRA Subpart 0 requirements for design and operation of
thermal treatment units would be ARARs for this alternative. The
specific type of thermal treatment unit would be selected during
the remedial design. Trial burns would be performed, and air
emissions from the incinerator would be controlled as necessary
to protect human health and the environment and comply with
federal, state, and local air emission regulations.
Following incineration, the treatment residuals would be
placed in the Landfill. RCRA land disposal regulations would be
applicable to these residuals if PCE concentrations are greater
than the health-based level of 5.6 ppm. However, incineration is
expected to be extremely effective in destroying VOCs, so that
treatment residuals could be placed in the Landfill with only a
vegetative cover.
In the DAC Storage and Truck Loading Area and Polishing
Basin Area, existing Quantum operations would be relocated so
that all contaminated soils can be excavated and bioremediated.
Contaminated soils at all other areas of the Site would also be
bioremediated. Approximately 500,000 cubic yards of material
28
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would be bioremediated. The excavation, materials preparation,
and bioremediation of these soils would be performed as described
in Alternative 6. After treatment, the treated materials would
be backfilled in the treated areas and a vegetative cover would
be installed.
Implementation time for this remedy is approximately
seventy-two months. The estimated capital cost for this
alternative is $269,500,000, and there would be no O&M cost.
8.0 Summary of Comparative Analysis of Alternatives
Nine evaluation criteria have been developed by EPA to
address CERCLA statutory requirements and technical, cost, and
institutional considerations which the Agency has determined to
be appropriate. The evaluation criteria serve as the basis for
conducting a detailed analysis of alternatives during the FS and
for subsequently selecting an appropriate remedial action.
Attachment A provides a glossary of the evaluation criteria.
8.1 Overall Protection of Human Health and Environment
Alternative 3 would adequately protect human health and the
environment because it would address the principal threat of OU#2
by using SVE to treat PCE, benzene and other volatile organic
compounds and enhance biodegradation of PAHs in the Landfill
Area. This will reduce direct contact exposure in the Landfill
as well as minimize indirect exposure through contaminant
leaching to groundwater. This alternative will also address
direct contact exposure to contaminants in the surface soils in
the DAC Storage and Truck Loading Area, Polishing Basin, Previous
Basin, Former Waste Pile F, and Surface Impoundments B, C, and D
through capping in the DAC Storage and Truck Loading and
Polishing Basin Areas and establishment and maintenance of a
vegetative cover in the other areas. Institutional controls in
all areas will supplement the containment measures and help to
ensure that exposures in these areas will not increase to the
extent that the carcinogenic and noncarcinogenic risks will be
unacceptable.
With the exception of the no action alternative, all the
other alternatives provide protection of human health and the
environment by removing, reducing, or controlling risk through
treatment, engineering controls, or institutional controls. The
no action alternative will not be evaluated further because it is
not protective of human health and the environment.
8.2 Compliance with ARARs
Section 121(d) of CERCLA requires that remedial actions at
CERCLA sites at least attain legally applicable or relevant and
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appropriate federal and State standards, requirements, criteria,
and limitations which are collectively referred to as "ARARs,"
unless such ARARs are waived under CERCLA Section 121(d)(4).
Applicable requirements are those substantive environmental
protection requirements, criteria, or limitations promulgated
under federal or State law that specifically address hazardous
substances found at the site, the remedial action to be
implemented at the site, the location of the site, or other
circumstances present at the site. Relevant and appropriate
requirements are those substantive environment protection
requirements, criteria, or limitations promulgated under federal
or State law which while not applicable to the hazardous
materials found at the site, the remedial action itself, the site
location or other circumstances at the site, nevertheless address
problems or situations sufficiently similar to those encountered
at the site that their use is well-suited to the site. ARARs may
relate to the substances addressed by the remedial action
(chemical-specific), to the location of the site (location-
specific) , or the manner in which the remedial action is
implemented (action-specific).
The State of Iowa has promulgated regulations pursuant to
Iowa Code Section 455E.5 which apply to cleanup actions at sites
where significant amounts of soil contamination are present and
groundwater contamination is occurring. These regulations, set
forth in 567 IAC 133, are applicable to the Landfill Area due to
the high levels of groundwater and soil contamination in the
Landfill Area. The regulations require "active cleanup of the
contaminated soils ... to the extent reasonable or necessary to
prevent or minimize release to the groundwater; passive cleanup
may be allowed in extraordinary circumstances". There are no
extraordinary circumstances at this Site, and thus active cleanup
is required. Active cleanup is defined by the regulation as the
removal, treatment, or isolation of contamination through
directed human efforts.
Alternatives 3 through 7 all involve treatment of the
Landfill materials and thus comply with this requirement.
Alternative 2, which provides for capping of the Landfill and
groundwater suppression, would comply with this requirement by
isolating the contaminated Landfill materials.
The substantive provisions of the State of Iowa's
requirements for closure of existing solid waste landfills
(I.A.C. Chapter 567-103, Subrule 103.2(13)) are also applicable
in the Landfill Area for Alternatives 2 through 5. These
alternatives, as opposed to Alternatives 6 and 7 (bioremediation
and incineration), would leave contaminated soils and wastes in
place in the Landfill, and thus closure in accordance with state
landfill closure requirements is required. The caps constructed
for Alternatives 2 through 5 would be constructed and maintained
as required by this regulation.
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Regulations have been promulgated under RCRA Subtitle C for
closure of hazardous waste landfills. These requirements are not
applicable to alternatives involving capping of the Landfill
materials in place, because the wastes were disposed of prior to
the effective date of the RCRA regulations.
However, some of these closure requirements are relevant and
appropriate. In particular, the hazardous waste landfill closure
requirements set forth at 40 CFR § 264.310 are relevant and
appropriate. These requirements mandate that the cap provide
long-term minimization of migration of liquids through the
Landfill, function with minimum maintenance, promote drainage and
minimize erosion, and have a permeability less than the natural
soils present. The requirements are relevant because wastes
disposed of in the Landfill prior to the effective date of RCRA,
in particular spent solvents, are now classified as RCRA
hazardous wastes. They are appropriate because the purposes of
the requirements - limiting infiltration and erosion in order to
prevent contaminant leaching to groundwater - are identical to
the remedial objectives for the Landfill cap. The Landfill cap
for Alternatives 2 through 5 would be constructed and maintained
in compliance with these RCRA requirements.
As explained earlier, materials excavated from the Landfill
for bioremediation or incineration would have to be handled in
accordance with RCRA requirements so long as the PCE
concentrations in such materials are above the health-based
concentration level of 5.6 ppm. Substantive RCRA storage
regulations would apply to storage of excavated materials prior
to treatment, and substantive RCRA design and operating
requirements for treatment units would also be applicable. RCRA
land disposal restrictions would govern disposal of treatment
residuals from the bioremediation and incineration of Landfill
materials.
The alternatives which involve capping include drainage and
runoff control. Any alternative which involves channeling of
site runoff directly to an on-site surface water body, via a
ditch, pipeline, storm sewer or otherwise, would have to comply
with substantive requirements of the National Permit Discharge
Elimination System program. Substantive requirements include
ambient water quality standards, effluent limitations, and
monitoring requirements.
The alternatives which involve SVE include collection and
treatment of vapors using technologies such as catalytic
oxidation or carbon adsorption. Any such equipment must be
operated in compliance with substantive requirements of the
National Emission Standards for Equipment Leaks of Benzene, 40
CFR Part 61, the RCRA Air Emission Standards for Process Vents,
40 CFR Part 265 Subpart AA, and the RCRA Air Emission Standards
for Equipment Leaks, 40 CFR Part 265 Subpart BB. Any treatment
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residuals from collection and treatment of vapors must be managed
in accordance with RCRA treatment, storage and disposal
regulations, since the PCE in such residuals would result from
treatment of listed waste (spent solvents disposed of in the
Landfill).
8.3 Lona-Term Effectiveness and Permanence
Alternative 3 includes implementation of SVE in the Landfill
Area, which would effectively minimize the long-term risks
associated with direct contact and contaminant migration to the
groundwater for the Landfill Area of the Site. Results of the
site-specific treatability tests indicate that SVE is likely to
be highly effective in reducing contaminant levels in the
Landfill Area. Capping and vegetative covers in the other areas
at the Site would reduce the potential direct contact exposures
to a carcinogenic risk level of less than 1 x 10"6. Long-term
controls would be required to ensure the integrity of the caps
and vegetative covers.
Alternative 2, which includes a cap but no treatment in the
Landfill, would effectively minimize direct contact risk but
would not be as effective as the Alternative 3 in reducing
contaminant migration to the groundwater. Alternatives 4 and 5,
which call for SVE and limited excavation in the DAC Storage and
Truck Loading and Polishing Basin Areas, would not be expected to
accomplish significantly greater long-term reduction of risk than
Alternative 3 because of the relatively low risk in the DAC
Storage and Truck Loading and Polishing Basin Areas compared to
the Landfill, inaccessibility of soils in these areas, and
limited effectiveness of SVE in these areas due to the low
permeability of the soils. Alternatives 6 and 7, which call for
excavation and treatment by bioremediation or incineration, would
provide the greatest degree of long-term effectiveness and
permanence by destroying the contaminants in the soils at the
Site through bioremediation or incineration.
EPA believes that groundwater suppression for areas other
than the Landfill, which is a common component of Alternatives 2
through 7 would not be advisable as it would not assist in
providing long-term reduction of risk at the Site and would in
fact inhibit long-term reduction of contaminants through
biodegradation.
8.4 Reduction of Toxicitv. Mobility, or Volume
Alternative 3 would employ SVE treatment in the Landfill to
reduce the toxicity, mobility, and volume of the contaminants in
the soil. Alternative 2 would reduce the mobility of the
contaminants in the Landfill Area through installation of a cap
and groundwater suppression, but would not reduce the toxicity or
the volume of the contaminants.
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Alternatives 4 and 5 would provide the same reduction in
toxicity, mobility, and volume for the Landfill Area as
Alternative 3, and would provide slightly greater reduction in
the DAC Storage and Truck Loading Area and Polishing Basin Areas.
The SVE and limited excavation called for in Alternatives 4 and 5
for the DAC Storage and Truck Loading Area and Polishing Basin
Areas would not accomplish significant reduction in toxicity,
mobility, and volume due to inaccessibility of the soils, limited
effectiveness of SVE in these areas and the relatively low
toxicity, mobility, and volume of contaminants in these areas
compared to the Landfill. There would, however, be some
reduction in contaminant levels in these soils.
Alternative 6 would provide significantly greater reduction
in toxicity, mobility, and volume than Alternatives 2 through 5,
through use of bioremediation to destroy the VOC and PAH
contaminants in the Landfill and DAC Storage and Truck Loading
Area soils. Alternative 7, which includes treatment of all
contaminated soils by either incineration or bioremediation,
would provide the greatest reduction by destroying contaminants
in all areas.
8.5 Short-Term Effectiveness
The short-term risks associated with the Alternative 3
include worker exposure to contaminants during SVE treatment and
cap construction, as well as possible exposure to fugitive dust
and surface runoff. These potential exposures can be effectively
minimized and controlled by compliance with worker safety
regulations, ARARs and implementation of engineering controls
such as dust suppression.
Alternative 2 would involve less short-term risks than
Alternative 3 because there would be less handling of
contaminated soils and waste. Alternatives 4 and 5 would involve
more short-term risks than Alternative 3, because of the expanded
SVE. Alternatives 6 and 7 would involve significantly greater
short-term risks to the community as well as construction workers
because of the excavation and handling of contaminated soils.
8.6 Implementability
Implementation of Alternative 3 would involve use of
conventional SVE technologies in the Landfill Area that are
proven and reliable. Treatability testing results indicate that
SVE is easily implementable in the Landfill Area. There are no
anticipated significant administrative issues, such as
permitting, that could affect the implementability of this
alternative.
Alternative 2, capping, would also be readily implementable.
Implementation of SVE and excavation in the DAC Storage and Truck
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Loading and Polishing Basin Areas as called for in Alternatives 4
through 6 would be difficult because of the on-going production
activities. Bioremediation, as called for in Alternative 6, was
proven effective for the contaminants of concern in the
Treatability Study. However, it would require special equipment
and materials and has not been done extensively on sites of this
magnitude. Use of on-site incineration, as called for in
Alternative 7, could be difficult to implement due to potential
community resistance to on-site incinerator operation. Although
incineration is a proven technology for destruction of the
contaminants of concern, excavation and handling of greater than
500,000 cubic yards of contaminated soils would involve
significant risk and uncertainty as well as the potential for
significant volatile organic emissions.
8.7 Cost
The cost of Alternative 3 would be approximately $11.4
million. The cost of Alternative 2, the remedy which
incorporates capping, would be approximately $5.5 million. The
cost of the other SVE/containment remedies ranges from $14.4
million to $15.1 million. The cost of excavation and treatment
by bioremediation or incineration as called for in Alternatives 6
and 7 ranges from $94.6 to $269.5 million.
8.8 State Acceptance
The State of Iowa concurs on EPA's selected remedy, which is
a modification of Alternative 3 (the selected remedy is discussed
in more detail in Section 9.0).
8.9 Community Acceptance
Community acceptance of the selected remedy has been
evaluated following the Public Meeting held on February 2, 1993,
and at the conclusion of the public comment period on February
21, 1993. The results of the evaluation are presented in the
attached Responsiveness Summary.
9.0 Selected Remedy
EPA has selected a remedy that is a modified version of
Alternative 3 as described above. The selected remedy is:
groundwater suppression, SVE, and capping in the Landfill
Area;
capping of the H-2 area (as indicated on Figure 9) of the
DAC Storage and Truck Loading Area;
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-UMP iREA
HISTORIC DAC
TRANSFER AREA
RAILCAR LOADING
OAC RECOVERY TRENCH i
WICK WELL
RECOVERY
SYSTEM
AREA
HAWKEYE DRIVE
SCALE IN FEET
=»ILROAO
-XISTINC CONCRETE
=sv£D IRE*
"£NCH WAIN
"CNI TORINO WELL
=ORINGS
DAC STORAGE AND TRUCK LOADING AREA
CHEMPLEX SUPERFUND SITE
CLINTON, IOWA
BECHTEL ENVIRONMENTAL. INC,
HOUSTON. TEXAS
otuim no.
21073-005
35
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establishment and maintenance of a vegetative cover in the
Polishing Basin Area, Previous Basin Area, Former Waste
Pile F, and Surface Impoundments B and D;
institutional controls in all areas; and
5-year reviews
The difference between the selected alternative and
Alternative 3 is that groundwater suppression would not be
incorporated in areas other than the Landfill, and most of the
areas in the DAC Storage and Truck Loading and Polishing Basin
Areas would not be capped. Groundwater suppression is a common
component of site-wide Alternatives 2 through 7 in the FS.
Although groundwater suppression would inhibit migration of
contaminants to some degree, it would also inhibit natural
biological degradation and attenuation of contaminants in the
study areas. Since OU#1 requires groundwater extraction and
treatment for the entire Site, any contaminated groundwater would
be collected and treated before it migrates off-site. Therefore,
EPA believes that it would be better not to suppress the
groundwater and isolate the contaminants. However, groundwater
suppression will still be incorporated in the Landfill to
facilitate SVE. Once SVE and any required monitoring is
complete, groundwater suppression will cease.
The highly contaminated soils and wastes in the Landfill
Area pose the principal threat being addressed by this remedial
action, and they will be addressed by SVE treatment. The
remaining low-level threats, and the contaminated soils in other
areas at the Site will be addressed through use of containment
and institutional controls.
Based on an evaluation of the relative performance of each
alternative with respect to the evaluation criteria, EPA has
determined that this alternative presents the best balance of
trade-offs among the alternatives considered for remediation of
the study areas. Each component of the remedy is described in
detail below.
9.1 Groundwater Suppression. SVE and Capping of the Landfill
Fence and Warning Signs
Groundwater suppression will be conducted in the Landfill
Area to facilitate operation of the SVE system and will be
implemented prior to SVE. It is important that the groundwater
suppression be coordinated with OU#1 groundwater extraction. In
particular, any Light Non-Aqueous Phase Liquid (LNAPL) recovery
activities will have to be undertaken prior to commencing
groundwater suppression to avoid creating an LNAPL smear across
Landfill soil and debris as the water table is lowered.
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The cleanup goal of SVE will be to remove 90-99% of volatile
organic compounds as measured by in situ gas concentrations.
This is consistent with expected performance of the SVE system,
based on results of the treatability tests. It is also
consistent with the NCP's stated Superfund program goal of
employing treatment technologies that reduce contaminant levels
by greater than 90%. Detailed performance criteria will be
developed as part of the design process. It is expected that
operation of the SVE system will be for a period of two to ten
years. Vapors from the SVE system will be treated using a
technology such as catalytic oxidation or carbon adsorption. The
appropriate treatment system will be selected during the remedial
design. Any residuals from the treatment system (i.e. carbon
filters) will be handled in compliance with RCRA Subtitle C
requirements for treatment, storage, and disposal of hazardous
waste.
The timing of installation of the cap over the Landfill will
need to be coordinated with operation of the SVE system to
maximize the -efficiency of the SVE operation. Therefore, the
exact timing of placement of the cap in conjunction with the SVE
system will be determined during the design phase.
As discussed in Sections 7 and 8, the State of Iowa's
requirements for closure of solid waste landfills are applicable
to the Landfill Area, and certain RCRA Subtitle C landfill
closure requirements are relevant and appropriate to the Landfill
Area. The exact details of the Landfill Area cap construction
will be finalized during the design phase; however, it will be a
multimedia cap with several feet of clay, geotextile,
geomembrane, and a vegetative cover. The cap will incorporate
appropriate stormwater drainage and diversion structures to
minimize erosion and limit future maintenance requirements. Gas
vents will be provided to remove any gases that may be trapped
under the liner.
After completion of the SVE operation and construction of
the cap, a fence will be installed around the Landfill Area and
warning signs will be posted.
Operation and maintenance (O&M), including but not limited
to periodic inspections, mowing, fertilizing, weeding,
replacement of any eroded cap material, sign and fence
maintenance, and maintenance of surface water diversion
structures will be required. The O&M requirements will be
finalized during the design phase.
9.2 Cap in the H-2 Area of the DAC Truck Storage and Loading
Area
The H-2 Area of the DAC Truck Storage and Loading Area will
be capped in order to eliminate direct contact from the surficial
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soils in this area. Unlike the cap in the Landfill Area, this
cap will not need to meet the State of Iowa solid waste or RCRA
hazardous waste landfill closure requirements. However, the cap
must be of sufficient thickness and durability that the ongoing
plant operations in the area will not reduce the cap's long-term
effectiveness. Examples of potentially appropriate cover
material for this cap are concrete and asphalt. Maintenance of
the cap will be required to ensure and maintain its integrity.
Details of cover material and thickness, as well as O&M
requirements, will be determined during the design phase.
9.3 Vegetative Cover. Warning Signs in the Other Areas
Vegetative covers will be established and maintained in the
Polishing Basin Area, Previous Basin Area, Former Waste Pile F,
and in Surface Impoundments B and D to prevent exposure to
damaged soils in these areas. Most of these areas have existing
vegetative cover that can be left in place and supplemented with
additional seeding so that there is a complete cover. Warning
signs will also be placed in these areas. O&M activities for
these areas include maintenance of the vegetative covers (mowing,
fertilizing, weed control, etc.). Details on the vegetative
covers, and O&M will be finalized during the design phase.
9.4 Institutional Controls
Institutional controls in the form of deed restrictions will
be required in all of the eleven study areas. These controls
will restrict future use of the areas and will prohibit any
excavation, drilling, or other intrusive activity in these areas
that would disturb a cap or vegetative cover and potentially
expose workers to contaminants. The deed restrictions will be
structured to allow future changes in use, if it can be
demonstrated to EPA that the proposed use will not have an
adverse impact on human health or the environment.
9.5 5-Year Reviews
The EPA required 5-year reviews will be required for all
eleven study areas because hazardous substances will remain on-
site.
10.0 Statutory Determinations
Under its legal authority, 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 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,
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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.
10.1 Protection of Human Health and the Environment
The selected remedy protects human health and the
environment through SVE treatment of the contaminated soil in the
Landfill. SVE treatment will extract and treat most of the
contaminants in the Landfill soils and thereby reduce the
potential to contaminate groundwater. The selected remedy also
requires a cap over the Landfill Area. The Landfill cap will
provide a physical barrier limiting the potential for direct
contact with any contaminants remaining after completion of the
SVE. It will also limit the amount of surface water infiltration
that passes through Landfill material, thus reducing the
potential for contaminant leaching to groundwater.
The selected remedy also includes a cap over the area H-2 of
the DAC Truck Storage and Loading Area, as well as vegetative
covers in the other areas and institutional controls for the
Site. This will ensure that there will never be direct contact
threats to contaminated surficial soil above the IxlO"6 level.
Compliance with site-specific worker health and safety plan and
control of SVE vapors will ensure that there are no unacceptable
short-term risks or cross-media impacts.
10.2 Compliance with Applicable or Relevant and Appropriate
Requirements
The selected remedy will comply with all federal and state
ARARs. The cap in the Landfill area will be constructed to
comply with the State of Iowa requirements for closure of solid
waste landfills. The cap will also comply with the RCRA landfill
closure requirements contained at 40 CFR § 264.310, which are
relevant and appropriate requirements for the Landfill cap.
The remedy employs SVE treatment in the Landfill Area, and
thus complies with the "active cleanup" requirement of 567 IAC
133. The SVE system, including the treatment unit(s) used to
treat vapors, will comply with the substantive requirements of
air emission standards contained in RCRA Part 264 Subparts AA and
BB, as well the Clean Air Act standards contained at 40 CFR Part
61. Treatment residuals from the SVE vapor treatment system will
be managed in accordance with RCRA treatment, storage, and
disposal regulations.
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Any drainage system or runoff collection system which is
constructed as part of the remedy and which discharges to an on-
site surface water body will comply with substantive provisions
of the NPDES program. Any off-site discharge will comply with
the substantive and administrative requirements of the NPDES
program.
10.3 Cost-Effectiveness
The selected remedy is cost effective because it will
provide overall effectiveness proportional to its cost, with the
net present value being approximately $11 million. The selected
remedy provides protectiveness essentially equivalent to that
provided by Alternatives 4 and 5, at significantly less cost. It
is nearly an order of magnitude less costly than either
Alternative 6 or 7. It is significantly more costly than
Alternative 2, but it is more protective than Alternative 2 and
complies with all ARARS.
10.4 Utilization of Permanent Solutions and Alternative
Treatment for resource recovery) Technologies to the
Maximum Extent Practicable (MEP)
The selected remedy represents the maximum extent to which
permanent solutions and treatment technologies can be utilized in
a cost-effective manner for the Chemplex Site. Specifically, the
selected remedy will permanently deal with the problems at the
Site by incorporating SVE treatment to remove contaminants from
the Landfill (with a goal of 90% removal of volatile organic
compounds), which pose the principal threat being addressed by
this action. It will also reduce lesser threats by construction
of permanent caps and covers over other areas of the Site that
will be maintained over the long-term. Of those alternatives
that are protective of human health and the environment and
comply with ARARs, the selected remedy provides the best balance
in terms of long-term effectiveness and permanence, reduction in
toxicity, mobility or volume achieved through treatment, short-
term effectiveness, implementability, and cost. Also, the State
and EPA considered the statutory preference for treatment as a
principal element, as well as input from the community.
This alternative reduces the mobility of contaminants by
treatment, complies with ARARS, provides short-term effectiveness
and protects human health and the environment equally as well as
Alternatives 3 through 7. Alternatives 1 and 2 do not meet the
preference for treatment and do not comply with all ARARs. In
terms of long-term effectiveness, the selected alternative
provides protection equal to or exceeding all other alternatives.
The selected alternative also will be technically and
administratively easier to implement than Alternatives 6 and 7
(which incorporate bioremediation and incineration). The
selected remedy is reliable and can be implemented quickly with
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less difficulty and at less cost than other treatment
alternatives. It is therefore the most appropriate solution for
the contaminated soils and wastes at the Chemplex Site.
10.5 Preference for Treatment as a Principal Element
By treating the contaminated soil in the Landfill Area by
SVE, the selected remedy addresses the principal threat of
contaminant migration to groundwater as well as potential direct
contact and ingestion/inhalation of contaminated soil. Although
the Landfill Area is the only area which will undergo treatment,
it has concentrations of contaminants that are orders of
magnitude higher than the other areas. Also, there are
approximately 350,000 cubic yards of contaminated material in the
Landfill, a significant amount of which is below the water table,
as opposed to approximately 20,000 cubic yards of moderately
contaminated soil in the other areas combined. EPA does not
believe that it is practicable to apply treatment to the other
areas given that the DAC Truck Storage and Loading and Polishing
Basin Areas are in operation and that contamination in all areas
(with the exception of the Landfill) is not significant, will
attenuate, and will be captured by the OU#1 groundwater pump and
treat system. Therefore, the statutory preference for remedies
that employ treatment as a principal element is satisfied.
ll.O Document of Significant Changes
The Proposed Plan for the soils and wastes for the Chemplex
Site was released for public comment on January 23, 1993. In the
Proposed Plan, the preferred alternative identified was:
groundwater suppression, SVE, and capping in the Landfill Area;
capping of the H-2 area of the DAC Truck Storage and Loading
Area; establishment and maintenance of a vegetative cover in the
Previous Basin Area, Former Waste Pile F, and Surface
Impoundments B, C, and D; and institutional controls in all
areas. The EPA reviewed all comments received during the public
comment period. Upon review of these comments, it was determined
that the only significant change to the remedy identified in the
Proposed Plan is that Surface Impoundment C will not need a
vegetative cover. Based on other comments, some minor changes
were made to this ROD. These changes are discussed in the
Responsiveness Summary.
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RESPONSIVENESS SUMMARY FOR THE RECORD OF DECISION
This responsiveness summary is divided into the following
sections:
Overview: This section discusses the public comment
period, public meeting and the public's view
of EPA's preferred alternative.
Background: This section provides a brief history of
community interest and concerns raised during
remedial planning at the Chemplex Site.
Part I: This section provides a summary of
commentors' major issues and concerns, and
expressly acknowledges and responds to those
raised by the local community. "Local
community" may include local homeowners,
businesses, the municipality and not
infrequently, potentially responsible parties
(PRPs).
Part II: This section provides a comprehensive
response to all written comments received and
is comprised primarily of the specific legal
and technical questions raised during the
public comment period. If necessary, this
section will elaborate with technical detail
on answers covered in Part I.
OVERVIEW
The Proposed Plan, RI/FS Reports and Administrative Record
were available for public comment from January 23 through
February 21, 1993. A public meeting was also held on February 2
at the Clinton County Community College. Comments received from
the local community, both in writing and during the public
meeting, were directed toward issues involving the effect of the
Site on human health and the environment in general. The
transcript from the public meeting is available with the
Administrative Record file. The local community did not express
a preference for, nor indicate any adversity to, EPA's preferred
alternative. ACC/GCC, who are PRPs at the Site, sent a letter to
EPA during the public comment period which indicated their
position that Alternative 2 was as protective as the preferred
alternative.
BACKGROUND
As part of the community relations process, which included
interviews of the local community and preparation of a Community
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Relations Plan during the planning stages of this project,
several community concerns were identified.
The Chemplex Site is located in a rural area, approximately
5 miles west of the cities of Clinton and Camanche, Iowa.
Another NPL site, the DuPont/Todtz Landfill Site, is located
approximately one mile from Chemplex. The Arcadian Fertilizer
Company is also located in close proximity to Chemplex.
Therefore, citizens who live in the surrounding area have
expressed concern that the proximity of these facilities to their
property may have had an adverse impact on their health and
property values.
PART I; SUMMARY OF COMMENTORS' MAJOR ISSUES AND CONCERNS
This section provides a summary of commentors' major issues
and concerns, and acknowledges and responds to comments made by
the local community during the public meeting on February 2. The
questions, comments, and responses are summarized below.
1. Question: A letter received by EPA prior to the public
meeting and that was signed by 24 Iowa state legislators
requested that a health study be conducted. The request was due
to concerns of potential adverse health impacts of residents who
live in close proximity to the Site. EPA's response at the
public meeting was that since the letter was received only a few
hours before the meeting, a commitment to conduct the study could
not be made at that time. However, the EPA personnel in
attendance at the meeting committed to discuss the request with
management.
Response: EPA forwarded the request for a health study to the
Agency for Toxic Substances and Disease Registry (ATSDR).
According to ATSDR, the Iowa Department of Public Health and the
University of Iowa Hygienics Laboratory are in the process of
conducting a health study. Therefore, ATSDR is not planning to
do a health study but is continuing to review the environmental
data and evaluate the need for other types of health activities.
2. Comment: Concern was expressed by citizens at the public
meeting about arsenic originating from the Chemplex Site
contaminating private drinking water wells. EPA agreed to review
the arsenic data for the Site and respond in writing.
Response: Background arsenic levels in soils upgradient of
Chemplex ranged from 0.6 parts per million (ppm) to 7.1 ppm and
averaged 3.6 ppm. Arsenic levels in soil on the Chemplex Site
ranged from zero to 54 ppm with most of the elevated samples
coming from the Landfill. Arsenic levels in the groundwater in
the vicinity of the Landfill range from 2 parts per billion (ppb)
to 31 ppb, indicating that the Landfill may have contaminated the
groundwater. There is no evidence of significant arsenic
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concentrations in groundwater at areas on the Site other than the
Landfill. Arsenic has not been detected in groundwater
monitoring wells located immediately downgradient of the Site
which indicates that arsenic is not migrating off-site.
Groundwater extraction and treatment will be implemented in 1994
and this will ensure that off-site migration of arsenic does not
occur. The cleanup standard for arsenic is 0.03 ppb for off-site
groundwater. The long-term groundwater monitoring plan at
Chemplex includes regular analysis for arsenic and it will be
analyzed for indefinitely.
3. Question: A citizen stated in the public meeting that
information received from the University of Iowa Hygienics
Laboratory indicated the presence of trichloroethylene (TCE) in
her private well. A representative of the laboratory indicated
that it was total organic carbon (TOG) that was present in this
particular well, not TCE. The citizen continued to be concerned.
EPA agreed to follow up on this.
Response: EPA reviewed the correspondence from the University of
Iowa Hygienics Laboratory and has confirmed that TOC was detected
in this citizen's drinking water well. TOC is not a contaminant
of concern at the site. TCE was not detected in this citizen's
drinking water well.
PART II; RESPONSE TO WRITTEN COMMENTS
This section provides technical detail in responding to
written comments or questions on the Chemplex Site. One of the
written comments received was a request by 24 Iowa state
representatives for a health study. This letter was read at the
public meeting and EPA's response to this letter is stated in
Part I. Two other comment letters were submitted by the local
community and two letters were submitted by the law firm
representing the Potentially Responsible Parties (PRPs), ACC and
Getty Chemical Companies (ACC/GCC).
Following are questions or comments and responses to the
letters received by the local community:
1. Question: When the Chemplex SVE material is discharged, will
the total amount of effluent (SVE and Quantum) discharged to the
Mississippi River still be within the discharge permit?
Response: The SVE system is a vacuum extraction system applied
to the vapors in the soils in the unsaturated zone (above the
zone where groundwater is found). The extracted vapors will
contain contaminants from the soils and will be treated (i.e.
carbon adsorption, catalytic oxidizer, etc.) prior to discharge
into the air.
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Regarding the discharge of wastewater to the Mississippi
River, the Quantum facility currently has a National Pollutant
Discharge Elimination System (NPDES) permit from the Iowa
Department of Natural Resources (IDNR) to discharge a certain
amount of water at certain levels from their treatment process to
the River. The levels and quantity of water have been
established by IDNR based on the Clean Water Act (CWA) to be
protective of a surface water body such as the Mississippi River.
The contaminated groundwater from the Site that will be extracted
and treated as part of the First Operable Unit will either need
to be discharged as part of Quantum's permit or will need a
separate NPDES permit. EPA will require the quantity and levels
established to be protective of the water quality of the
Mississippi River.
2. Question: A letter from another citizen expressed concern
regarding the number of cancer cases in the vicinity of the Site
and requested if a health study would be conducted. The citizen
also wanted to know what EPA was going to do about the Arcadian
Fertilizer facility.
Response: The health study issue has been addressed in Question
l of Part I. Regarding the Arcadian facility, this is currently
being handled by IDNR.
The remaining questions and/or comments were submitted by
the law firm representing ACC/GCC. The questions and/or comments
and responses are as follows:
1. Comment: The Proposed Plan calls for SVE and groundwater
suppression in the Landfill followed by installation of a
multimedia cap. The comment was made that the SVE component of
the proposed alternative will not appreciably increase the
protectiveness of this remedial option over a cap in conjunction
with OU#1 groundwater extraction and treatment. The comment
further states that the cap would meet both remedial action
objectives for the Site by cutting off the possibility of direct
contact with and surface water infiltration through the
contaminated soil and debris in the Landfill.
Response: Gross contamination in the soils and wastes in the
Landfill is migrating into the groundwater and would continue to
do so even after installation of a cap since much of the waste
material is below the water table. This contamination will
continue to act as a source of groundwater contamination for many
years. The groundwater contamination will be controlled and
prevented from migrating off-site by the OU#1 groundwater
extraction and treatment system. However, it is also important
to reduce or eliminate the source of groundwater contamination
wherever it is practicable to do so. It is possible with present
technologies, as demonstrated by treatability studies at the
Site, to effectively and efficiently remove large amounts of
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contaminants from the Landfill, thus greatly reducing contaminant
migration to the groundwater. This can be done in a reliable and
cost-effective manner, using SVE treatment that is expected to
remove greater than 90% of the VOC contaminants from the
Landfill. This can be done in situ, without excavating the
Landfill and putting numerous workers and local residents at
risk.
Also, CERCLA mandates the use of permanent solutions to the
maximum extent practicable and expresses a preference for
treatment as a principle element of remedial actions. Capping
the Landfill Area would not satisfy these statutory requirements,
while use of SVE treatment would.
EPA has determined that the benefits in source reduction
realized by using SVE in the Landfill will be substantial and
should remain as part of the remedy. This determination is
consistent with the remedial action objective for the Site of
reducing the migration of chemicals into the groundwater to the
maximum extent practicable.
2. Comment: The appropriate protective risk level at a secured
industrial facility like the Chemplex Site is 1 x 10"4 instead of
the remediation goal as stated in the Proposed Plan of
approximately 1 x 10"6.
Response: The baseline risk assessment for the Site assumed only
industrial exposures; residential risk scenarios were not
considered due to the fact that the facility is now and is likely
to remain as a industrial facility. In accordance with EPA's
guidance on risk assessments, the baseline industrial exposures
were calculated using less frequent exposure time and less
sensitive populations (i.e. healthy adults as opposed to
children) than if baseline residential exposures had been
calculated. Similarly, the appropriate protective risk level for
this Site is 1 x 10-6 risk, for industrial exposures. Increasing
the acceptable risk level in addition to assuming an industrial
exposure would result in unacceptable exposures.
3. Comment: SVE performance standards in the Landfill should be
flexible to reflect the innovative application of this technology
and the heterogeneity of the Landfill.
Response: This comment is valid. EPA has established a cleanup
goal of removing 90-99% of volatile organic compounds, as
measured by in situ gas concentrations. This is consistent with
expected performance of the SVE system. It is also consistent
with the NCP's stated Superfund program goal of employing
treatment technologies that reduce contaminant levels by greater
than 90%. Detailed performance criteria will be developed as
part of the design process.
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4. Comment: The final remedy should provide flexibility in the
timing and coordination of SVE and capping in the Landfill to
maximize the efficiency of the SVE system. The Proposed Plan
indicates that installation of the cap will follow SVE.
Response: EPA agrees that flexibility should be allowed in
coordinating the timing of SVE and the cap. The exact timing
will be determined during the design phase.
5. Comment: The Proposed Plan should reflect that groundwater
suppression in the Landfill should be coordinated with First
Operable Unit groundwater extraction and treatment. In
particular, any Light Non-Aqueous Phase Liquid (LNAPL) recovery
activities will have to be undertaken prior to commencing
groundwater suppression to avoid creating an LNAPL smear across
Landfill soil and debris as the water table is lowered.
Response: EPA agrees with this comment. This has been included
in the ROD.
6. Comment: Given the current restrictions on access and the
existing vegetative covers on the various impoundments, posting
of appropriate signs should be sufficient to reduce worker
exposure. Also, deed restrictions should not necessarily prevent
any future change in land uses. Any institutional controls
implemented should allow future changes in accordance with an
activity-specific health and safety plan to address possible
exposure and a design that recognizes and addresses the presence
of chemicals of concern.
Response: EPA agrees that there is vegetative cover on most of
the impoundments. However, there are also bare spots in some of
the areas that need to be addressed. Warning signs without
fences are appropriate as long as there are sufficient
restrictions to ensure that more frequent exposures to these
areas does not occur. In regard to allowing institutional
controls that include future changes in accordance with an
activity, EPA would need to review and approve that action prior
to its implementation.
7. Comment: The description of the DAC Truck Storage and
Loading Area on page 4 of the Proposed Plan should include
reference to an existing french drain.
Response: The following information has been added to the ROD:
The area south of the railroad tracks is unpaved and is bordered
on its southern end by a french drain. The french drain was
installed voluntarily by ACC/GCC in approximately 1988 as an
interim groundwater recovery system to intercept Light Non-
Aqueous Phase Liquid (LNAPL) present as free product floating on
the water table. The french drain appears to be at least
somewhat effective in controlling LNAPL.
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8. Comment: Section 3.2 on page 10 of the Proposed Plan should
clearly discuss the relationship of the First and Second Operable
Units. This section should indicate that the Second Operable
Unit remedy presented in the Proposed Plan was developed in
conjunction with the First Operable Unit remedy, and that
together, the First and Second Operable Unit remedies are
intended to provide a complete remedy for the Chemplex Site.
Response: EPA agrees with this comment. This section presently
states that "In concert, OU#1 and OU#2 will address all human
health and environmental risks at the Site." This clarifies that
the two Operable Units are intended to provide a complete remedy
for the Site.
9. Comment: Section 3.2 on page 10 of the Proposed Plan
incorrectly refers to June 1994 as the date the First Operable
Unit groundwater extraction and treatment system is expected to
be operational. Due to the difficulty of projecting such a date
in light of certain remedial design obstacles, it is suggested
the reference to such date be deleted.
Response: EPA agrees that the June 1994 date is incorrect. The
ROD will refer to the operational date as being sometime in 1994.
10. Comment: The risk levels calculated as part of the
Supplemental Endangerment Assessment for the various areas of the
Site were overstated because of an artifact of the methodology.
More accurate risk levels were calculated using the instrument
detection limits. Using these limits, the risk to on-site
workers in the DAC Truck Storage and Loading Area, the Polishing
Basin and Surface Impoundment C do not exceed 1 x 10'6. The
risks from soils in other areas were less than those estimated in
the Supplemental Endangerment Assessment, although they still
exceeded 1 x 10"6.
Response: EPA agrees with this methodology in this case, given
that the sample quantitation limits (SQLs) are much higher than
either the instrument detection limits and the levels that were
detected. Therefore, Surface Impoundment C will not need
establishment and maintenance of a vegetative cover as discussed
in the Proposed Plan. This will be changed in the ROD. However,
given the relatively high concentrations of total PAHs (CPAHs
were not analyzed for) Area H-2 of the DAC Truck Storage and
Loading Area will still need to be capped.
11. Comment: ACC/GCC's consultant also evaluated using the
instrument detection limit instead of the SQL for the exposure
scenario of the construction worker in the Previous Basin and
Landfill Areas. In doing this they discovered that the
concentrations reported for carcinogenic Polynuclear Aromatic
Hydrocarbons (CPAHs) for the Previous Basin in the Supplemental
Endangerment Assessment were incorrect and were actually two
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orders of magnitude higher than the actual concentrations. This
resulted in the risk to construction workers in the Previous
Basin being below 1 x 10"6. They also discovered that using the
instrument detection limits instead of the SQLs for the Previous
Basin further reduced this risk. For the Landfill, the resulting
risk of using the instrument detection limit as opposed to the
SQL reduced the risk but did not lower it to below 1 x 10"6.
Response: EPA agrees with this comment. However, the preferred
alternative for the Landfill Area is SVE and capping. With
regard to the Previous Basin Area, the preferred alternative is
establishment and maintenance of a vegetative cover as well as
institutional controls. Changing the risk of the construction
worker's exposure would not affect either of these preferred
alternatives.
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ATTACHMENT A
GLOSSARY OF EVALUATION CRITERIA
The following criteria were developed by EPA to address
CERCLA statutory requirements and technical, cost, and
institutional considerations. The evaluation criteria serve
as the basis for conducting detailed analyses during the
Feasibility Study and for subsequently selecting an
appropriate remedial action.
OVERALL PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
Alternatives are assessed as to whether they can
provide adequate protection froa risks above health-based
levels posed by contamination present at"the site by
eliminating, reducing, or controlling exposures.
COMPLIANCE WITH ARARs
The alternatives are assessed as to whether they attain
applicable or relevant and appropriate requirements or other
Federal and State environmental and public health laws or~
provide grounds for invoking a waiver.
LONG-TERM EFFECTIVENESS AND PERMANENCE
The magnitude of risk remaining after implementation of
the alternatives is evaluated. The adequacy and reliability
of controls used to manage treatment residuals or untreated
wastes that remain at the site are also assessed.
REDUCTION OF TOXICITY, MOBILITY AND VOLUME
The degree to which the alternatives employ treatment
that reduces toxicity, mobility, or volume is assessed.
SHORT-TERM EFFECTIVENESS ^
The alternatives are evaluated with respect to. their
effects on human health and the environment during
implementation of the alternative. Also assessed is the
amount of time until protectiveness is achieved.
ZMPLEMENTABILTTY
The technical and administrative feasibility of
implementing an alternative and the availability of services
and materials required to implement an alternative are
evaluated.
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COST
Direct and indirect capital costs and operation and
maintenance costs incurred over the life of the project are
identified.
STATE ACCEPTANCE
Technical and administrative issues and concerns the
State say have regarding the alternative are assessed.
COMMUNITY ACCEPTANCE
The issues and concerns of the public regarding the
alternatives are assessed.
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