EPA/ROD/R04-95/216
1995
EPA Superfund
Record of Decision:
OLIN CORP. (MCINTOSH PLANT)
EPA ID: ALD008188708
OU01
MCINTOSH, AL
12/16/1994
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RECORD OF DECISION
SUMMARY OF REMEDIAL ALTERNATIVE SELECTION
OLIN CORP. (McINTOSH PLANT) SITE
OPERABLE UNIT ONE
McINTOSH, MOBILE COUNTY, ALABAMA
PREPARED BY
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION IV
ATLANTA, GEORGIA
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DECLARATION
of the
RECORD OF DECISION
OPERABLE UNIT ONE
SITE NAME AND LOCATION
Olin Corp. (Mclntosh Plant) Site
Mclntosh, Mobile County, Alabama
STATEMENT OF BASIS AND PURPOSE
This decision document, presents the selected remedial action for Operable Unit One of the Olin
Corp. (Mclntosh Plant) Site, Mclntosh, Alabama, ("the Olin Site" or "the Site") developed in
accordance with the Comprehensive Environmental Response, Compensation and Liability Act of 1980
("CERCLA"), as amended by the Superfund Amendments and Reauthorization Act of 1986 ("SARA") 42
U.S.C. Section 9601 et seq., and to the extent practicable, the National Contingency Plan
("NCP") 40 CFR Part 300. This decision is based on the administrative record for the Olin Site.
The State of Alabama, as represented by the Alabama Department of Environmental Management
("ADEM"), has been the support agency during the Remedial Investigation and Feasibility Study
process for the Olin Site. In accordance with 40 CFR 300.430, as the support agency, ADEM
has provided input during this process. ADEM has concurred with the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from the Olin Site, if not addressed by
implementing the response action selected in this ROD, may present an imminent and substantial
endangerment to public health, welfare or the environment.
DESCRIPTION OF SELECTED REMEDY
This operable unit is the first of two that are planned for the Site. This alternative calls for
the design and implementation of response measures which will protect human health and the
environment. The first operable unit addresses the source of the contamination on the Site as
well as the groundwater contamination across the entire Site. While this remedy does address the
principal threats at the Site, the second operable unit will involve continued study and
remediation, if appropriate, of a drainage basin on the Site located adjacent to the Tombigbee
River.
The major components of the selected remedy for operable unit one include:
• Extraction of the groundwater from horizontal and vertical wells with subsequent onsite
treatment. The extraction wells would be designed to improve the RCRA Corrective Action
Program and to capture, for treatment, the area of contamination including the area of
dense brine accumulation;
• Upgrading and extending the existing cap over the old plant (CPC) landfill with a
multimedia cap and performing additional groundwater monitoring in the vicinity of the
landfill. The CPC landfill cap will be extended to encompass the former drainage ditch
area. The clay cap that exists over the former CPC plant will be extended to the west,
capping the contaminated soils;
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• Quarterly monitoring and maintenance of the existing clay caps over the sanitary
landfills, the lime ponds, and the strong brine pond, the asphalt cover over the mercury
cell plant, and the fencing around the well sand residue area will be established. The
findings of the inspections will be documented. If an inspection noted problem areas such
as erosional areas, cracks in the asphalt, or insufficient cap depth, maintenance or
corrective measures will be reguired. Maintenance and corrective measures will also be
documented;
• Additional groundwater monitoring in the vicinity of the sanitary landfills will be
implemented. In the event that monitoring indicates releases from the sanitary landfills,
additional corrective action measures will be reguired;
• Monitoring to determine the effectiveness of the groundwater treatment in reducing the
contaminant migration; and
• Institutional controls for land use and groundwater use restrictions.
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment, complies with federal and
state reguirements that are legally applicable or relevant and appropriate, and is
cost-effective. Because this remedy will result in hazardous substances remaining onsite above
health-based levels, a review will be conducted within five years from commencement of the
remedial action to ensure that the remedy continues to provide adeguate protection of human
health and the environment.
RICHARD D. GREEN, ASSOCIATE DIRECTOR OF DATE
SUPERFUND AND EMERGENCY RESPONSE
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TABIiE OF CONTENTS
1. 0 Site Location and Description 1
2 . 0 Site History and Enforcement Activities 1
3 . 0 Highlights of Community Participation 4
4 . 0 Scope and Role of Operable Unit 5
5 . 0 Summary of Site Characteristics 5
5 .1 General Site Characteristics 5
5 . 2 Summary of Site Contamination 7
5.2.1 Source Evaluation 7
5.2.2 SWMU Soil Evaluation 7
5.2.2.1 Old Plant (CPC) Landfill 7
5.2.2.2 Former CPC Plant Area 8
5.2.2.3 Sanitary Landfills 8
5.2.2.4 Lime Ponds 9
5.2.2.5 Strong Brine Pond 10
5.2.2.6 Former Mercury Cell Plant 10
5.2.2.7 Old Plant (CPC) Landfill Drainage Ditch 11
5.2.2.8 Well Sand Residue Area 11
5.2.3. Groundwater Evaluation 11
5.2.3.1 Alluvial Aguifer Sampling 12
5.2.3.2 Miocene Aguifer Sampling 14
5.2.3.3 Residential Well Sampling 14
5.2.4 Surface Water Runoff 14
6. 0 Summary of Site Risks 15
6.1 Chemicals of Concern 15
6. 2 Exposure Assessment 16
6. 3 Toxicity Assessment 18
6. 4 Risk Characterization 21
6. 5 Cleanup Levels 23
7 . 0 Description of Alternatives 24
7 .1 Groundwater 25
7 . 2 Old CPC Plant Landfill 25
7 . 3 Area West of Former CPC Plant 25
7.4 Sanitary Landfills, Lime Ponds, Strong Brine Pond,
Mercury Cell Plant, and Well Sand Residue Area 26
8.0 Summary of the Comparative Analysis of Alternatives 26
8 .1 State Acceptance 38
8 . 2 Community Acceptance 38
9.0 Summary of Selected Remedy 38
10 . 0 Statutory Determination 42
11. 0 Documentation of Significant Changes 42
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LIST OF TABLES
Chemicals of Concern 16
RfCs, RfDs, Slope Factors, and Carcinogen Classification 20
Summary of Chemical-Specific Risks 22
Cleanup Performance Sandards for Groundwater 24
Cleanup Performance Standards for Soils 24
ARARS 28
Summary of Detailed Analysis OU-1 Groundwater 30
Summary of Detailed Analysis Old Plant (CPC) Landfill 31
Summary of Detailed Analysis Area West of Former CPC Plant 33
Summary of Detailed Analaysis OU-1 Soils
Sanitary Landfills, Lime Ponds, Strong Brine Pond
Mercury Cell Plant and Well sand Residue Area 35
LIST OF FIGURES
Figure 1 Area Map for Mobile, Alabama 2
Figure 2 Site Map 3
Figure 3 Horizontal extent of groundwater contamination 13
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Decision Summary
Record of Decision
Operable Unit One
Olin Chemicals Site
Mclntosh, Alabama
1.0 SITE LOCATION AND DESCRIPTION
The Olin Corp. (Mclntosh Plant) Site (hereinafter, "the Site") is located approximately 1 mile
east-southeast of the town of Mclntosh, in Washington County, Alabama. For an area location map
and general Site map, see Figures 1 and 2, respectively. The property is bounded on the east by
the Tombigbee River, on the west by land not owned by Olin west of U. S. Highway 43, on the
north by the Ciba-Geigy Corporation plant site and on the south by River Road. The Olin
Mclntosh plant is an active chemical production facility. The main plant and associated Olin
properties cover approximately 1,500 acres, with active plant production areas occupying
approximately 60 acres.
2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES
Olin Corporation ("Olin") operated a mercury cell chlor-alkali plant (constructed in 1951) on a
portion of the Site from 1952 through December 1982. In 1952, Alabama Chemical Company began
operation of a chlorinated organics plant on property immediately south of the Olin plant. In
1954, Olin acguired Alabama Chemical and in 1955 began construction of a pentachloronitrobenzene
("PCNB") plant on the acguired property. The plant was completed and PCNB production was
started in 1956. The Mclntosh plant was expanded in 1973 to produce trichloroacetonitrile
("TCAN") and 5-ethoxy-3trichloromethyl-l,2,4-thiadiazole ("Terrazole"). The PCNB, TCANand
Terrazole manufacturing areas were collectively referred to as the Crop Protection Chemicals
("CPC") plant. In 1978, Olin began operation of a diaphragm cell caustic soda/chlorine plant,
which is still in operation. Olin shut down the CPC and mercury cell chlor-alkali plants
between 1982 and 1986. The CPC plant was decommissioned and dismantled and the site was capped.
The Mclntosh plant today produces chlorine, caustic soda, sodium hypochlorite and sodium
chloride and blends and stores hydrazine compounds. Current active facilities at the plant
include: a diaphragm cell chlorine and caustic production process area; a caustic concentration
process area; a caustic plant salt process area; a hydrazine blending process area; shipping and
transport facilities; process water storage, transport and treatment facilities; and support and
office areas. Olin mines a salt dome through a series of brine production wells located to the
west of the active plant facility. The salt dome cap is at a depth of approximately 500 feet
below the surface. The dome is approximately 4,500 feet in diameter and greater than 2 miles
deep. Nine brine wells have been completed in the salt dome for the production of brine. The
first six wells were associated with the mercury cell chlor-alkali plant and are no longer in
service. The other three brine production wells were developed in a different portion of the
salt dome, have been used exclusively for the diaphragm cell plant, and are still in use. A
tenth cavity was developed in the dome by Olin for use by the Alabama Electric Cooperative to
store high-pressure (1200 psi) air for off-peak power production.
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The Olin Mclntosh plant currently monitors and reports on numerous facilities within the plant
that are permitted through the EPA and the Alabama Department of Environmental Management
(ADEM). These include water and air permits as well as a Resource Conservation and Recovery
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Act (RCRA) post-closure permit. The RCRA post-closure permit requires groundwater monitoring
for closed RCRA units, including the weak brine pond, the stormwater pond and the brine filter
backwash pond. The post-closure permit also requires corrective action for releases of 40 CFR
261 Appendix VIII constituents from any solid waste management units (SWMUs) at the facility.
There are no active RCRA units at the facility. Olin also has permits for three injection wells
for mining salt and a neutralization/percolation field.
Investigations have indicated contamination in a 65-acre natural basin, located on the Olin
property east of the active plant facilities. The plant wastewater ditch currently carries the
NPDES discharge and storm water runoff from the manufacturing areas, as well as from some of the
west, east and southeast manufacturing areas of Olin property to the Tombigbee River. From 1952
to 1974, plant wastewater discharge was routed through the basin and then to the Tombigbee
River. In 1974, a discharge ditch was constructed to reroute the wastewater directly to the
Tombigbee River.
In September 1984, Olin's Mclntosh plant site was placed on the National Priority List of CERCLA
or "Superfund." Groundwater contamination at the site had been established based on the results
of various investigations. Mercury and chloroform were the principal contaminants identified at
the site. Mercury contamination was evidently caused by the operation of the mercury cell
chlor-alkali plant during the period 1952 to 1982. The chloroform contamination is probably a
degradation product from the operation of the TCAN plant from 1973 to 1982.
In 1989, EPA and Olin entered into an Administrative Order on Consent ("AOC") for Olin to
conduct a remedial investigation/feasibility study ("RI/FS") under EPA oversight.
3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION
On December 12 1990, at the beginning of Remedial Investigation field work, an availability
session at a local library and interviews with local officials and community were held. The
main branch of the Mobile Public Library at 300 Pine Street was chosen as the local information
repository for the Site. On March 12, 1992, Olin held a public meeting to discuss an upcoming
removal action at the Site. In addition, a fact sheet concerning the RI was sent to those on
the mailing list in May 1992.
A Proposed Plan fact sheet and Administrative Record containing the final RI and Feasibility
Study ("FS") was issued to the public on February 28, 1994 to the repository. The public
comment period on the Proposed Plan was held from March 1, 1994 through March 30, 1994. A
public meeting was held on March 15, 1994 where EPA answered questions regarding the Site and
the Proposed plan under consideration. The administrative record was available to the public at
both the information repository maintained at the Mobile Public Library and at the EPA Region IV
Library at 345 Courtland Street in Atlanta, Georgia. The notice of availability of these
documents was published in the Mobile News-Herald on February 28, 1994. Responses to the
significant comments received during the public comment period and at the public meeting are
included in the Responsiveness Summary, which is part of this ROD in Appendix A.
This decision document presents the selected remedial action for operable unit one of the Olin
Site, chosen in accordance with CERCLA, as amended by SARA, and the NCP. The decision for this
Site is based on the administrative record. The requirements under Section 117 of CERCLA/SARA
for public and state participation have been met for this operable unit.
4.0 SCOPE AND ROLE OF OPERABLE UNIT
As with many Superfund sites, the problems at the Olin Site are complex. As a result, EPA has
organized the work at this Site into the following two phases or operable units ("OUs"):
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• OU-1: OU-1 consists of the active production facility, Solid Waste Management Units
("SWMUs"), and the upland area of Olin property. The areas in OU-1 beyond the active
production facilities include predominantly undeveloped areas to the north and northwest
and the brine well field to the west. The most distinctive topographic feature is a steep
bluff located approximately 4,000 feet east of the main plant area. This bluff defines
the edge of the low-lying OU-2 floodplain area.
• OU-2: OU-2 consists of a basin, floodplain, and a wastewater ditch leading to the basin.
The basin is a natural oxbow lake lying within the floodplain of the adjacent Tombigbee
River. During the seasonal high water levels (approximately 4 to 6 months per year), the
basin is inundated by surface water, and thus becomes contiguous with, the adjacent river.
A remedy for OU-2 will be developed in a subseguent ROD, if it is determined that remedial
action will be necessary.
5.0 SUMMARY OF SITE CHARACTERISTICS
5.1 GENERAL SITE CHARACTERISTICS
The Mclntosh area is underlain by alternating beds of unconsolidated-to-consolidated sedimentary
rocks that are collectively hundreds of feet thick. The Mclntosh salt dome is the most
distinctive structural feature of the area.
The groundwater in the vicinity of the Olin Site contains two major aguifers, the Alluvial and
the Miocene: The Alluvial Aguifer in the main plant area varies in thickness from an average of
about 55 feet to 80 feet. The Alluvial Aguifer is generally unconfined throughout the area.
The hydraulic conductivity was estimated to be between 4 ft/day and 40 ft/day. Groundwater in
the Alluvial Aguifer generally enters the site from the north. The southerly flow is divided
into southeast and southwest components by a groundwater divide oriented north-south through the
center of the plant site. Flow to the east of this divide is to the east and southeast,
discharging to the basin in the northern portion of the Site and farther south, flow continues
in a southeasterly direction toward RCRA corrective action wells.
In off-site areas southeast of the facility, groundwater from the Alluvial Aguifer discharges to
the Tombigbee River. On the western side of the groundwater divide, flow is south and southwest
toward the groundwater recovery area created by RCRA corrective action wells. A hydraulic mound
farther to the west deflects westerly flow to the south in the brine field area. The
groundwater flow patterns are affected by the seasonal rises in the Tombigbee River. During
periods of high river stage, instead of groundwater discharging eastward, the basin and
Tombigbee River become recharge areas and groundwater flow is to the west toward the active
facility.
The Miocene units are designated as Tml, and Tm2. The Miocene confining unit (Tml) consist of
clays, sandy clays, or clayey sands. Boring logs from wells that penetrate the upper Miocene
confining unit indicate that this unit is approximately 80 to 100 feet thick. The Miocene
Aguifer (Tm2) is composed primarily of thick-bedded coarse sand and gravel beds. The upper
Miocene Aguifer (Tm2) contains two main artesian sands that are separated by a clayey unit
ranging from 10 to 20 feet thick. The sands are considered as one hydrogeologic unit due to a
natural hydraulic-connection and connection by gravel-packed wells. The combined transmissivity
of the two sands is considered to be in excess of about 25,000 sguare feet per day. The
regional gradient of the Miocene Aguifer is to the east-southeast, however, Olin continuously
pumps two Miocene Aguifer process water wells. The effect of pumping process water wells is to
cause groundwater flow in the Miocene Aguifer to be toward the process water wells across the
plant area.
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The active production areas of the plant are relatively flat. A topographic high of greater
than 50 feet (above mean sea level) extends from the northern to the southern extent of Olin's
property, west of the production facility and east of the brine well field. This topographic
high creates a drainage divide that defines the two major surface water drainage pathways. A
steep bluff located approximately 4,000 feet east of the main plant area defines the edge of the
low-lying floodplain area, which is about 25 feet lower in elevation than the upland areas
immediately to the west. Runoff from the northern portions of the site east of the drainage
divide flows eastward to a low-lying area between the plant area and the basin. There is also a
small east-west drainage divide in the northeast corner of the Olin property. Flow to the north
of this divide is to the Ciba-Geigy property.
The watershed for the basin within the floodplain area is limited to the area defined as OU-2.
The basin and surrounding wetlands lie within the floodplain of the Tombigbee River. The most
significant feature of OU-2 is the basin.
5.2 Summary of Site Contamination
5.2.1 Source Evaluation
A source evaluation was conducted which included a review of the RCRA guarterly groundwater data
to evaluate trends in chemical concentrations that may indicate the presence of significant
sources of groundwater contamination. Potential sources were also evaluated using the results
of the RI soil sampling.
5.2.2 SWMU SOILS EVALUATION
Potential source areas were evaluated by examining trends in guarterly groundwater data from
1987 until 1991 and conducting subsurface soil sampling at SWMUs. Subsurface soil samples were
collected from the following SWMUs/AOCs:
Old plant (CPC) landfill
• Former CPC plant area
• Sanitary landfills
• Lime ponds
• Strong brine pond
• Former mercury-cell plant
Old plant (CPC) landfill drainage ditch
• Well sand residue area
The sampling results are summarized in the following sections.
5.2.2.1 Old Plant (CPC) Landfill
The site of the old plant (CPC) landfill was utilized from 1954 until 1972 to neutralize acidic
wastewater from CPC plant operations. The landfill area is approximately 300 x 400 feet and is
estimated to have had an 8,000-cubic-yard capacity. During the RI sampling soil and residual
waste samples were analyzed for the EPA's Contract Laboratory Program (CLP) Target Compound List
(TCL) volatile organics, TCL semivolatile organics, TCL pesticides/PCBs and the selected Target
Analyte List (TAL) constituents.
The vertical distribution of constituents in three of the soil borings (BOP2, BOPS and BOP4)
showed decreases in constituent concentrations with increasing depth. At BOP2 and BOPS, the
constituent concentrations in the clay beneath the landfill and in the underlying sand above the
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water table are near or below detection limits. Concentrations of organic constituents at BOP4,
located in the western portion of the landfill, indicate migration of constituents through the
clay and into the upper portion of the unsaturated underlying sand. The data for BOP1, located
in the western portion of the landfill, indicate that organic constituents have migrated through
the clay and the unsaturated portion of the underlying sand. Overall, the data indicate that
migration of organic constituents into the Alluvial Aguifer from the soil is most likely in the
western portion of the landfill. Based on the analytical results described above, the old plant
(CPC) landfill was identified as a potential source of contaminants, particularly organics, to
the groundwater.
5.2.2.2 Former CPC Plant
The former CPC plant was constructed in 1952 and initially manufactured monochlorobenzene,
adding pentachloronitrobenzene (PCNB) in 1956. In 1973, the plant was expanded to produce
trichloro-acetonitrile (TCAN) and 5-ethoxy-3-trichloromethyl-l,2,4-thiadiazole (Terrazole). The
PCNB, TCAN and Terrazole manufacturing areas were collectively referred to as the crop
protection chemicals (CPC) plant. The CPC plant was shut down in 1982. In 1984 the plant area
was dismantled and covered with an approximately 2-foot-thick recompacted clay cap and topsoil.
The capped area was then vegetated.
During the RI, borings were drilled into the unsaturated sand above the Alluvial Aguifer. The
soil samples were analyzed for CLP TCL volatile organics, TCL semivolatile organics, TCL
pesticides/PCBs, and the selected list of TAL constituents.
Chemicals of concern were detected in soil samples from boring (BCP1) at the west boundary of
the old plant area. The data from the area west of the former CPC plant (BCP1) showed
chlorobenzene at a maximum concentration of 0.54 mg/kg in the upper clay material. Benzene,
carbon disulfide and chloroform were also detected in the clay, at concentrations less than 0.02
mg/kg. The detected TCL semivolatile chlorinated benzenes in the two clay samples ranged from
an estimated concentration of 0.2 mg/kg for hexachlorobenzene to 750 mg/kg for
1,2,4,5-tetrachlorobenzene. Concentrations in BCP1 decreased with depth in the sand. Two TCL
chlorinated benzenes were detected in the bottom (sand) sample from BCP1 (30 to 32 feet):
hexachlorobenzene at 1.5 mg/kg and 1,2,4,5-tetrachlorobenzene at an estimated concentration
below the guantitation limit (CRQL) of 0.055 mg/kg. The data indicated a potential for the area
west of the former CPC plant to be a continuing source of groundwater contamination, therefore
soil action levels were developed.
5.2.2.3 Sanitary Landfills
There are two sanitary landfills which comprise about 12 acres. Cells at the landfills are 6
feet deep. The landfills were intended for the disposal of only sanitary waste, trash, and
debris, however, sampling was conducted to address a report which suggested that the landfills
received wastes containing hexachlorobenzene and mercury sludges. Each boring penetrated the
full waste depth (0 to 7 feet) and was composited for analysis. The samples were analyzed for
CLP TCL volatile organics, TCL semivolatile organics TCL pesticides/PCBs, and the selected list
of TAL constituents. The samples were also analyzed using the toxic characteristics leaching
procedure (TCLP) for mercury.
Hexachlorobenzene concentrations ranged from 9.5 mg/kg to 44 mg/kg. Mercury concentrations
ranged from 7.8 to 27.1 mg/kg. The chlorinated benzenes: chlorobenzene,
1,2,4,5-tetrachlorobenzene, 1,2,4-trichlorobenzene, 1,4-dichlorobenzene, and 1,3-dichlorobenzene
were detected at low concentrations (<10 mg/kg). Pentachlorobenzene and pentachloronitrobenzene
were tentatively identified in the sanitary landfill samples at estimated concentrations ranging
from 1.0 mg/kg to 3.6 mg/kg for pentachlorobenzene and 0.16 mg/kg to 31 mg/kg for
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pentachloro-nitrobenzene. 2,3,4,5,6-pentachlorobenzamine was tentatively identified with
estimated concentrations ranging from 0.25 mg/kg to 6.5 mg/kg. The data were evaluated to
determine whether contaminants present in the landfills would affect the groundwater above MCLs.
Fate and transport analysis of the data indicated that constituents percolating in infiltrating
water through the soils in the sanitary landfill would be unlikely to affect the Alluvial
Aguifer above the MCL at the landfill boundary.
5.2.2.4 Lime Ponds
The east and west lime ponds were used to manage spent lime slurry used to absorb chlorine gas
from various vent streams. Their use ceased in 1976 and they were closed in 1979 with ash for
stabilization, a clay cap, topsoil and grass. The lime ponds are located 10 to 15 feet above
natural grade. The lime waste in these ponds is covered by 0.5 to 6.0 feet of clay/sandy clay
and about 10 feet of ash. Samples were analyzed for total and TCLP mercury.
The sample results are summarized below:
Sample TAL Mercury TCLP Mercury
Boring Interval (ft) Result (mg/kg) Result (• g/1)
BL1 16 to 18 1.3 10
BL2 12 to 14 0.46 3
The Summers model was used to assess the concentration of mercury in the groundwater of the
Alluvial Aguifer that could result from infiltration of leachate from the closed lime ponds.
The assumption that the infiltrating water for each lime pond has a mercury concentration egual
to that of the highest mercury TCLP result (10 • g/1) was used in the calculation. The analysis
indicated that mercury from the former lime ponds would be unlikely to affect the Alluvial
Aguifer above the MCL at the lime pond boundaries.
5.2.2.5 Strong Brine Pond
The strong brine pond was a holding pond for the strong brine process fluid that was removed
from the brine wells for use in the mercury cell plant. It was removed in 1985. It was
approximately 340 x 340 feet and constructed partially above-grade in natural clay.
The pond was sampled to assess whether mercury-containing brine seeped from the pond and
contaminated the underlying soils to the extent that mercury can be leached to the groundwater.
Mercury concentrations from the TCLP leachate were 5 • g/1 and 30 • g/1 for the two samples.
These results indicate that some mercury has migrated to the natural soils beneath the former
pond. An analysis was performed to evaluate whether the leachate from the subsoil could affect
the Alluvial Aguifer. The Summers model calculation was completed to assess what concentration
of mercury in the groundwater of the Alluvial Aguifer could result from infiltration of water
through the subsoil. The assumption that the infiltrating water has a mercury concentration
egual to that of the highest mercury TCLP result (30 • g/1) was used in the calculation. The
analysis indicated that mercury in water percolating through the soil beneath the closed strong
brine pond would be unlikely to affect the Alluvial Aguifer above the MCL at the SWMU boundary.
5.2.2.6 Former Mercury Cell Plant
The former mercury cell plant area was the location of the mercury cell rooms until the plant
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was shutdown in 1982 and demolished in 1986. Decommissioning included removing all above ground
structures to the concrete bottom floor of the building. The sumps and trenches were filled
with clay. The floor was covered with a synthetic roofing membrane (Durbigum) and asphalt. The
area (approximately one acre) was sampled in an unbiased grid pattern. The results are
summarized below:
Sample TAL Mercury TCLP Mercury
Boring Interval (ft) (mg/kg) (• g/1)
BMC1 0 to 4 <0.12 <2
BMC2 0 to 4 <0.12 <2
BMC3 0 to 4 <0.12 <2
BMC4 0 to 4 164 40
BMC5 0 to 4 0.38 <2
0.16 (Duplicate)
BMC6 0 to 4 3.4 <2
A Summers model analysis was used to evaluate the potential migration from the mercury cell
plant. The assumption that the infiltrating water would have a concentration of 40 • g/1 was
used in the analysis. The analyses of the soil samples from beneath the former plant indicates
that if leachate infiltrated into the Alluvial Aguifer, mercury concentrations in otherwise
uncontaminated groundwater would be unlikely to exceed the MCL of 2 • g/1 at the mercury cell
plant boundary.
5.2.2.7 Old Plant Landfill Drainage Ditch
The old plant landfill drainage ditch formerly drained from the old plant (CPC) landfill to the
wastewater ditch. Due to extensive earth work in the area associated with the closure of the
old plant (CPC) landfill, there is no longer any surface remnant of the ditch. Samples were
analyzed for CLP TCL volatile organics, TCL semivolatile organics, TCL pesticides/PCBs, and the
selected list of TAL constituents. Mercury, at a concentration of 10 mg/kg, and
hexachlorobenzene, at a concentration of 6 mg/kg, are the contaminants which were found in any
significant concentration. The old plant landfill drainage ditch soils are not in a defined
area, therefore, guantifiable fate and transport analysis to assess potential impact on
groundwater was not performed. However, due to the close proximity of the drainage ditch to the
old plant (CPC) landfill, the ditch soils are included with the landfill soils. A guantitative
evaluation of the potential for migration to groundwater was performed for the old plant (CPC)
landfill and potential soil action levels were developed.
5.2.2.8 Well Sand Residue Area
Well sands were generated from development and operation of the brine wells for the mercury cell
chlor-alkali process. These sands are residues of the material from the salt domes. During
early operation of the mercury cell plant, when the well sands were generated, they were
deposited in mounds in an area referred to as the well sand residue area. The well sand in
these mounds is a cohesive granular material that has the consistency of sandstone. Samples
were collected at ten randomly selected areas and depths within the mounds. The 10 individual
samples were ground and composited into one sample for analysis (mercury and TCLP mercury). The
total mercury concentration detected in the well sand composite sample was 20.1 mg/kg. Mercury
was not detected in the leachate from the TCLP analysis. Therefore, the well sand is not
considered a current source of groundwater contamination.
5.2.3 Groundwater evaluation
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There are two aquifers of concern at the Olin Mclntosh site: the Alluvial Aquifer and the
Miocene Aquifer. Based on investiqations of Alluvial Aquifer Olin implemented a qroundwater
corrective action proqram in 1987. The onqoinq RCRA monitorinq includes quarterly samplinq of
compliance and corrective action wells screened in the Alluvial Aquifer. The qroundwater flow
direction over the horizontal extent of OU-1 is towards the corrective action wells.
5.2.3.1 Alluvial Aquifer Samplinq Results
Twenty-nine monitorinq wells and corrective action wells screened in the Alluvial Aquifer were
sampled at the facility from September 9, 1991 throuqh September 19, 1991. The wells were
sampled for the followinq constituents: mercury (total and dissolved), a selected list of 13
additional Tarqet Analyte List (TAL) compounds (total and dissolved); Tarqet Compound List (TCL)
volatile orqanics; TCL semivolatile orqanics; TCL pesticides/PCBs and chloride. Both mercury
and chloroform were reported at concentrations hiqher than the Primary Drinkinq Water Standard
MCLs.
Mercury is the primary inorqanic constituent of concern at the facility and was selected to
define the extent of inorqanics. Chloroform was used to define the extent of orqanics because of
its prevalence in all perimeter wells containinq orqanics and qenerally at concentrations hiqher
than other orqanics. The exception is at the west perimeter, where chlorobenzene was reported
at a qreater concentration than chloroform. Therefore, with the exception of the west
perimeter, chloroform was used to define the horizontal extent of orqanics.
The horizontal extent of mercury and chloroform in the qroundwater is presented in followinq
fiqures:
![]()
5.2.3.2 Miocene Aquifer Samplinq Results
Two process water wells and two monitorinq wells screened in the Miocene Aquifer were also
sampled as part of the RI. Chlorobenzene, 1,2-dichlorobenzene, and 1,4-dichlorobenzene were
reported in the qroundwater samples from one of the process water wells screened in the Miocene
Aquifer. However, the detected concentrations in this well were less than the MCLs.
Mclntosh City Water Wells 1 and 2, are also screened in the Miocene Aquifer. Water Well 1 is
about 2 miles to the northwest and Water Well 2 is about 5 miles southwest of the site. The
data indicate that Wells 1 and 2 have not been affected by contamination from the site.
5.2.3.3 Residential Well Samplinq Results
A total of 122 residential wells (active, inactive and closed) were identified within a 3-mile
radius of the Olin facility; 34 of these wells which were identified as drinkinq water wells
were sampled.
Samples from the drinkinq water wells identified in the domestic well survey were analyzed for
the followinq constituents: total mercury, total orqanic carbon (TOG), total suspended solids
(TSS), and chloride. In addition, the wells were analyzed for TCL volatile orqanic
constituents. Mercury was reported in 1 of the drinkinq water wells and volatile constituents,
which are related to the Olin facility were reported in some of the drinkinq water wells. All
reported concentrations were below the respective MCLs.
5.2.4 Surface Water Runoff
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The two major surface water drainage pathways within the Olin property were examined. The Olin
plant discharges are routed either through the existing NPDES system or through areas sampled
for Olin's storm water discharge permit. The NPDES permit limits are based on the Alabama water
guality standards for the receiving water, which is the Tombigbee River. Olin continues to meet
their NPDES limits as documented by their ongoing surface water monitoring programs.
6.0 SUMMARY OF SITE RISKS
The baseline risk assessment ("BRA") provides the basis for taking action and indicates
contaminants and the exposure pathways that need to be addressed by the remedial action. It
serves as an indication of what risks the site poses if no action were taken. This section of
the ROD contains a summary of the results of the baseline risk assessment conducted for this
site.
In the BRA, EPA evaluated Site risks for several environmental media. This ROD summarizes only
human health exposures because OU1 is the plant facility and no significant ecological or
habitats exposures are expected. Ecological risks will be evaluated for OU2 (the basin) in a
subseguent ROD.
The risk assessment included the following major components: chemicals of concern, exposure
assessment, toxicity assessment, and risk characterization.
6.1 Chemicals of Concern
The risk assessment evaluated current and potential future risks from exposure to chemicals of
potential concern. The chemicals which are included in this Section as chemicals of concern are
those for which the results of the risk assessment indicate that the contaminant might pose a
significant current or future risk. Chemicals of concern are those compounds that contribute to
a pathway that exceeds a 1 x 10-4 risk or a Hazard Index ("HI") of 1. Chemicals contributing
risk to these pathways were not included if their individual carcinogenic risk contribution was
less than 1 x 10-6 or their noncarcinogenic hazard Quotient ("HQ") was less than 0.1. In
addition, chemicals were included if they exceeded either State or Federal ARARs.
The exposure point concentration for each contaminant was derived using the 95 percent upper
confidence limit ("UCL") on the arithmetic mean. If the 95% UCL resulted in a concentration
higher than the maximum concentration detected, the maximum concentration detected was used as
the exposure point concentration. In order to provide an accurate assessment of risk from the
Site.
Under the current land-use scenario, chemicals of concern would pose unacceptable risks if the
on-site groundwater were used as a source of potable water. Future land use is likely to remain
industrial on the property currently occupied by the site. Following is a list of those
chemicals for which the results of the risk assessment indicates that the contaminant may pose a
significant current or future risk. Also included are their corresponding groundwater exposure
point concentrations.
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CHEMICALS OF CONCERN
Pathway/Chemical Exposure Point Concentration
Groundwater Ingestion
1,2-dichlorobenzene
1,4-dichlorobenzene
1,2,4-trichlorobenzene
Alpha-BHC
Arsenic
Benzene
Beryllium
Br omodi chloromethane
Cadmium
Cadmium Tetrachloride
Chlorobenzene
Chloroform
Chromium VI
Copper
Cyanide
Lead
Mercury
Nickel
Pentachlorobenzene
Pentachloronitrobenzene
1.400
2.076
0.024
0.004
0.003
0.049
0.0812
0.010
0.022
0.006
0.613
0.521
0.172
0.103
0.104
0.050
0.1462
0.8992
0.007
0.005
1 Exposure point concentration is based on 95% UCL of log normal distribution unless
otherwise noted.
2 Maximum detected concentration is listed of 95% UCL exceeds maximum concentration.
6.2 EXPOSURE ASSESSMENT
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In the exposure assessment, EPA considered ways in which people could come into contact with
contaminants under both current and future conditions. All likely pathways of exposure were
evaluated. The current use of the land in the vicinity of the site is industrial to the north
and residential to the south. Future land use is likely to remain industrial on the property
currently occupied by the plant.
The risk assessment evaluated the potential exposure to chemicals of potential concern to adults
and children living near or trespassing on the contamination currently, and site industrial
workers. Exposure pathways for offsite residential receptors include (1) residential exposure to
water from domestic wells screened in the Alluvial Aquifer (ingestion, dermal contact [through
skin] and inhalation [breathing] of volatile organic constituents) and (2) potential contact
with soils in OU1 areas (particulate inhalation). Children might potentially be at greater risk
due to behavior patterns or sensitivity to chemical constituents. Exposure pathways for site
industrial workers include exposure to groundwater via dermal and inhalation during quarterly
sampling of groundwater from monitor and corrective action wells. And exposure to OU1 surface
soils (dermal, ingestion and particulate inhalation).
The exposure point concentrations are the chemical concentrations to which a receptor is exposed
when contact is made with a specific environmental medium.
The data used to develop the exposure point concentrations are summarized below:
• Groundwater: Chemical analyses of on-site groundwater samples collected from the monitor
wells, corrective action wells and process water wells for the groundwater chemicals of
potential concern.
• Surface Soil: Chemical analyses of soil samples collected from beneath the asphalt cap in
the mercury cell plant area for mercury and the surficial soil (0-1 foot) sample
collected from the old plant landfill drainage ditch for hexachlorobenzene.
• Domestic well water (off-site): Chemical analyses from the 34 drinking water wells that
were sampled during November 1991 for those analytes that were detected in one or more of
the samples.
To address air exposure pathways to environmental media for which measured concentrations were
not available, modeled concentrations of the various constituents were used to estimate exposure
point concentrations.
Additionally, chemical-specific dermal exposures to domestic well water and groundwater were
calculated for the risk assessment.
In order to calculate the daily chemical intake, a number of exposure parameters are first
quantified. Exposure parameters which are typically quantified include the following:
• Exposure frequency (days/year)
• Exposure time (hrs/day)
• Exposure duration (years)
• Groundwater ingestion rate (I/day)
• Soil/sediment ingestion rates (mg/day)
• Body weight (kg)
• Body surface area (m2)
• Lifespan (days)
• Fish ingestion rates (g/day)
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The exposure parameters are included in the text of the baseline risk assessment on pages 6-27
to 6-36. The numerical values used in the exposure algorithm were developed using the Exposure
Factors Handbook (U. S. EPA, 1989b) and OSWER Directive 9285.6-03 (Standard Default Exposure
Factors; U. S. EPA, 1991c) and the Risk Assessment Guidance for Superfund (RAGS) Manual (U. S.
EPA, 1989a).
Exposure to a chemical is described in terms of intake. The measure of exposure has been
defined as a reasonable maximum exposure. The reasonable maximum exposure has been estimated
using guidance provided in EPA's Risk Assessment Guidance for Superfund (RAGS) (U.S. EPA,
1989a). The reasonable maximum exposure is defined by selecting intake variable values so that
the combination of all intake variables results in a maximum exposure that is reasonably
expected to occur at the site.
6.3 TOXICITY ASSESSMENT
Slope factors (SFs) have been developed by EPA's Carcinogenic Assessment Group for estimating
excess lifetime cancer risks associated with exposure to potentially carcinogenic chemicals of
concern. SFs, 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 SF. Use of this
conservative approach makes underestimation of the actual cancer risk highly unlikely. Slope
factors are derived from the results of human epidemiological studies or chronic animal
bioassays to which animal-to-human extrapolation and uncertainty factors have been applied
(e.g., to account for the use of animal data to predict effects on humans).
The SF is used to estimate an upper-bound probability of an individual developing cancer as a
result of exposure to a potential carcinogen. Chemicals, both carcinogenic and noncarcinogenic,
are given an EPA weight-of-evidence classification.
The following classifications were derived from, Environmental Protection Agency (U. S. EPA).
1989. Risk assessment guidance for Superfund. Volume I: Human Health evaluation manual.
Interim final. Office of Emergency and Remedial Response. EPA. Washington, D. C.
EPA/625-3-89/002.
Group Classification
A Human carcinogen. Sufficient evidence from epidemiologic studies to support a
causal association between exposure and cancer.
B1/B2 Probable human carcinogen; Bl indicates that limited human data are available
from epidemiologic studies. B2 indicates sufficient evidence in animals and
inadeguate or no evidence in humans of carcinogenicity.
C Possible human carcinogen. Limited evidence of carcinogenicity in animals.
D Not classifiable as to human carcinogenicity. Inadeguate evidence of
carcinogenicity in animals.
E No evidence of carcinogenicity in humans or in at least two adeguate animal
tests or in both epidemiologic and animal studies.
Reference doses (RfDs) have been developed by EPA for indicating the potential for adverse
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health effects from exposure to chemicals of concern exhibiting noncarcinogenic effects. RfDs,
which are expressed in units of mg/kg/day, are estimates of lifetime daily exposure levels for
humans, including sensitive individuals. Estimated intakes of chemicals from environmental media
(e.g., the amount of chemicals of concern ingested from contaminated drinking water) can be
compared to the RfD. RfDs are derived from human epidemiological studies or animal studies to
which uncertainty factors have been applied (e.g., to account for the use of animal data to
predict effects on humans).
The RfD and SF values used in the risk assessment were obtained from the following sources:
EPA's Integrated Risk Information System (IRIS) (U. S. EPA, 1992b) on-line database
system
EPA's Health Effects Assessment Summary Tables (U. S. EPA,1992d)
When toxicity values were found from both sources for a given constituent, priority was given to
the IRIS value. Constituents of potential concern not possessing verified RfDs or SFs are
addressed gualitatively in the risk characterization section of the Remedial Investigation
Report (Section 6.7). The slope factors and weight-of-evidence classifications for the
chemicals of potential concern are also included in the following table.
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RfCs, RfDs, SLOPE FACTORS, AND CARCINOGEN CLASSIFICATION FOR CHEMICALS OF
Inhalation
2.00E-02
Chemical
Alpha-BHC
Arsenic(1)
Benzene(1)
Beryllium(l)
Bromodichloromethane(1)
Cadmium (soil)(1)
Cadmium (water)(1)
Carbon Tetrachloride(1)
Chlorobenzene(1)
2
Chloroform(l)
Chromium VI(1)
Copper(3)
Cyanide(2)
1,2-Dichlorobenzene(1)
1,4-Dichlorobenzene(2)
Lead(l)
Chronic
CONCERN
Ingestion/Dermal
Chronic
Carcinogen
Status
B2
A
A
B2
.) B2
ND
Bl
.) B2
C
B2
D
D
ND
D
C
B2
Slope Factor RfC Slope Factor RfD
(mg/kg/day) -1 mg/kg/day (mg/kg/day) -1 mg/kg/day
6.30E+00 ND 6.30E+00 ND
5.0E+01 8.3E-05 1.75E+00 3.00E-04
2.90E+02 ND 2.90E-02 ND
8.40E+00 ND 4.30E+00 5.00E-03
ND ND 1.30E-01 2.00E-02
ND ND ND l.OOE-03
6.1-E+OO ND ND 5.00E-04
5.3E-02 ND 1.3E-01 7.00E-04
ND 5.00E-03 ND
8.1E-02 ND 6.1E-03 l.OOE-02
4.1E+01 5.70E-07 ND 5.00E-03
ND ND ND 3.70E-02
ND ND ND 2.00E-02
ND 4.00E-02 ND 9.00E-02
ND 2.00E-01 2.4E-02 ND
ND ND ND 7.00E-01
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Mercury(1) D ND 8.6E-05 ND
3.00E-04
Nickel(1) A 8.4E-01 ND ND
2.00E-02
Pentachlorobenzene(1) ND ND ND ND 8.00E-04
Pentachloronitrobenzene(2) C ND ND 2.60E-01 3.00E-03
l,2,4-Trichlorobenzene(l) ND ND 3.00E-03 ND 1.31E-03
NOTES: Delta-BHC, bromobenzene and 1,3-dichlorobenzene were not included in this table these constituents lack published toxicity values.
ND = Not determined or available
(1) = Value presented by IRIS (EPA, 1992b)
(2) = Value presented by HEAST (EPA, 1992c)
(3) = Value calculated from Safe Drinking Water Act treatment technique.
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6.4 RISK CHARACTERIZATION
Human health risks are characterized for potential carcinogenic and noncarcinogenic effects by
combining exposure and toxicity information. For carcinogens, risks are estimated as the
incremental probability of an individual developing cancer over a life-time as a result of
exposure to the carcinogen. Excess life-time cancer risk is calculated from the following
eguation:
Risk = GDI x SF where: risk = a unit less probability
(e.g., 2 x 10-5) of an individual developing cancer
GDI = chronic daily intake averaged over 70 years (mg/kg-day)
SF = slope factor, expressed as (mg/kg-day)-1
These risks are probabilities that are generally expressed in scientific notation (e.g., 1x10-6
or l-E-6). An excess lifetime cancer risk of 1x10-6 indicates that, as a reasonable maximum
estimate, an individual has a one in one million additional (above their normal risk) 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. EPA considers individual excess cancer risks
in the range of 1x10-4 to 1x10-6 as protective; however the 1x10-6 risk level is generally used
as the point of departure for setting cleanup levels at Superfund sites. The point of departure
risk level of 1x10-6 expresses EPA's preference for remedial actions that result in risks at the
more acceptable end of the risk range.
The potential for noncarcinogenic effects is evaluated by comparing an exposure level over a
specific time period (e.g., life-time) with a reference dose derived for a similar exposure
period. The ratio of exposure to toxicity is called a hazard guotient (HQ). An HQ<1 indicates
that a receptor's dose of a single contaminant is less than the RfD, and that the toxic
noncarcinogenic effects from that chemical are unlikely. The Hazard Index (HI) is generated by
adding the HQs for all chemicals of concern that affect the same target organ (e.g., liver)
within a medium or across all media to which a given population may reasonably be exposed. An
HK1 indicates that, based on the sum of all HQ's from different contaminants and exposure
routes, toxic noncarcinogenic effects from all contaminants are unlikely. The HQ is calculated
as follows:
HQ = GDI/RfD where: GDI = Chronic daily intake
RfD = reference dose
GDI and RfD are expressed in the same units (mg/kg-day) and represent
the same exposure period.
Quantified carcinogenic and noncarcinogenic risks for each chemical of concern in each relevant
exposure medium for each exposure pathway are presented in the following table.
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SUMMARY OF CHEMICAL-SPECIFIC RISKS
USED TO DEVELOP REMEDIAL GOAL OPTIONSl
SUMMARY OF CHEMICAL-SPECIFIC RISKS
USED TO DEVELOP REMEDIAL GOAL OPTIONS
FUTURE ADULT OU-1 RESIDENT
FUTURE CHILD OU-1 RESIDENT
Excess
Lifetime
Cancer Risk
Chronic
Hazard Index
Cancer Risk
Excess
Lifetime
Hazard Index
Chronic
Ingestion of OU-1 Groundwater
Cumulative Risk for Pathway
1,2,4-trichlorobenzene
1,2-dichlorobenzene
1,4-dichlorobenzene
Alpha BHC
1,2,4-trichlorobenzene
Arsenic
Benzene
1,4-dichlorobenzene
Beryllium
Bromodichloromethane
Cadmium
Carbon Tetrachloride
Chlorobenzene
Chloroform
Chromium (VI)
Tetrachloride
Cyanide
Mercury
Nickel
Pentachlorobenzene
Pentachloronitrobenzene
5E-3
—
—
6E-4
3E-4
—
6E-5
2E-5
3E-4
4E-3
2E-5
—
9E-6
—
4E-5
—
4E-6
—
—
—
--
2E+1
5E-1
4E-1
—
—
1E+0
3E-1
—
2E-1
4E-1
—
1E+0
2E-1
8E-1
1E+0
9E-1
5E-1
1E-1
1E+1
1E+0
2E-1
2E-5
Ingestion of OU-1 Surface Soil
Cumulative Risk for Pathway
Mercury
Ingestion of OU-1 Groundwater
Cumulative Risk for Pathway
1,2-dichlorobenzene
Alpha BHC
Arsenic
Benzene
Beryllium
Br omodi chloromethane
Cadmium
Carbon
Chlorobenzene
Chloroform
Chromium (VI)
Copper
Cyanide
2E-3
1E-4
3E-5
8E-6
2E-3
7E-6
2E-5
7E+0
7E+0
5E+1
1E+0
6E-1
1E+0
3E+0
2E+0
3E+0
2E+0
2E-1
3E-1
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Inhalation of OU-1 Groundwater Volatile Compounds
Mercury -- 3E+1
Cumulative Risk for Pathway -- 3E+0
Chlorobenzene -- 2E-1
Mercury — 2E+0
Pentachloronitrobenzene 7E-6 1E-1
Dermal Contact with OU-1 Groundwater
Cumulative Risk for Pathway 1E-4
1,4-dichlorobenzene 9E-5
Alpha-BHC 1E-6
Benzene 5E-6
Beryllium 2E-5
Chloroform 1E-5
1,2,4-trichlorobenzene — 2E-1
Pentachloronitrobenzene 2E-6
Nickel
Pentachlorobenzene
3E+0
6E-1
Inhalation of OU-1 Groundwater Volatile Compounds
Cumulative Risk for Pathway — 1E+1
Chlorobenzene — 8E-1
Mercury — 1E+1
Dermal Contact with OU-1 Groundwater
Cumulative Risk for Pathway — 1E+0
1,2-diChlorobenzene
1E-1
Chlorobenzene
Chloroform
1E-1
7E-1
NOTE: 1 Remedial goal options were not developed for the current receptors (i.e., off-site
resident/trespassers or industrial workers) because none of the pathways for these receptors
exceeded the 1 x 10-4 excess lifetime cancer risk or a 1.0 hazard index.
Remedial goal options were not developed for this pathway/chemical either because the
pathway contributed less than 1 x 10-4 excess lifetime cancer risk and less than 1.0 hazard index,
or the chemical contributed less than 1 x 10-6 excess lifetime cancer risk and less than a 0.1
hazard guotient.
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The risk assessment indicates that only risks associated with potential future on-site resident
exposures to contaminated groundwater and surface soils would not be within EPA' s acceptable
risk range. The chemicals of concern would pose unacceptable risks if the on-site groundwater
were used as a source of potable water or if children living on the site were exposed to
contaminated surface soils. Future use of this site as a residential area is considered
unlikely and thus the proposed remedial goals are directed at protecting the groundwater for its
maximum beneficial use.
6.5 CLEANUP LEVELS
Actual or threatened releases of hazardous substances from this Site, if not addressed by
implementing the response action selected in this ROD, may present an eminent and substantial
endangerment to public health, welfare, or the environment.
Fate and transport analysis provided an evaluation of the potential effects on groundwater from
the SWMUs/AOCs. The analysis was conducted by assuming that the source concentration was the
maximum concentration detected in the soils. In cases where site-specific leachate test (TCLP)
data were available, the maximum concentration from the TCLP extract was assumed to be the
leachate concentration at the source. Cleanup levels were developed (see tables below) for the
groundwater, the old plant landfill drainage ditch, the old CPC plant landfill, and for the area
west of the former CPC plant. These cleanup levels for groundwater are based on MCLs or
health-based calculations. Cleanup levels for the area west of the former CPC plant are based
on protection of groundwater for domestic use from contaminants which may migrate from the soils
to the groundwater.
The tables on the following page include cleanup levels for groundwater based on SDWA MCLs or
health-based calculations and cleanup levels for subsurface soil were based on protection of
groundwater for domestic use from leachable chemicals. Cleanup levels for soils were developed
for the protection of groundwater at the groundwater cleanup level.
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CLEANUP PERFORMANCE STANDARDS FOR GROUNDWATER
Constituent Cleanup Goal(*g/l)
Alpha-BHC 0.013
Benzene 5
Chlorobenzene 100
1,2,4-Trichlorobenzene 70
1,2-Dichlorobenzene 600
1,3-Dichlorobenzene 75
1,4-Dichlorobenzene 75
Mercury 2
Pentachlorobenzene 29
Pentachloronitrobenzene 0.29
CLEANUP PERFORMANCE STANDARDS FOR SOILS1,2
Constituent Soil Cleanup Goal (mg/kg)
Benzene 5
Chlorobenzene 79
1,2-Dichlorobenzene 1,645
1,3-Dichlorobenzene 140
1,4-Dichlorobenzene 140
1,2,4-Trichlorobenzene 1,000
Mercury 55
1 Cleanup levels will be developed for Alpha-BHC, Pentachlorobenzene,
Pentachloronitrobenzene if they are encountered during the cleanup.
2 Cleanup level for soils were developed for the protection of groundwater at
the groundwater cleanup level.
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7.0 DESCRIPTION OF ALTERNATIVES
The Feasibility Study Report evaluated possible alternatives for remediation of conditions at
the Olin site. Several alternatives were retained for the detailed analysis consideration. In
OU-1 there are four (4) general areas which have been evaluated for remediation. Those areas
are:
1 - Groundwater
2 - Old Plant (CPC) Landfill (includes Old Plant Landfill Drainage Ditch)
3 - Area West of the Former CPC Plant
4 - (Collectively) The Sanitary Landfills, Lime Ponds, Strong Brine Pond, Mercury Cell
Plant and the Well Sand Residue Area.
THE FOLLOWING IS A SUMMARY OF ALTERNATIVES EVALUATED IN THE FS:
7.1 GROUNDWATER
Alternative A - No Action With Continuation of Existing RCRA Corrective Action Program (CAP)
which prevents and controls off-site contamination/ contingency to provide municipal water.
Alternative Cl - Pump and Treat System (Additional Vertical Extraction Wells)/Discharge
Alternative C3 - Extraction (Additional Vertical and Horizontal Wells)/Treatment/Discharge
7.2 Old Plant (CPC) Landfill
Alternative A (all source areas) - No Action
Alternative C - Containment (Improve Capping with additional Groundwater Monitoring)
Alternative D - In Situ (in place) Solidification-Stabilization/Containment (Capping), and
additional Groundwater Monitoring
Alternative E - Excavation/Stabilization-Solidification, Containment (Capping), and additional
Groundwater Monitoring
Alternative F - Excavation/Off-Site RCRA Disposal of fill/waste material with In Situ
Stabilization of the underlying soils
Alternative Gl - Excavation/On-Site Thermal (heat) Treatment/Disposal of fill/waste material
with In Situ Stabilization of the underlying soils and placement of treated materials into the
landfill area.
7.3 Area West of Former CPC Plant
Alternative C - Containment which will include extension of the cap which exist in the area of
the CPC plant, monitoring, and maintenance.
Alternative D - In Situ Stabilization-Solidification/Containment which will include construction
of a protective cover (cap), monitoring and maintenance.
Alternative E - Excavation/Stabilization-Solidification/Containment which will include
construction of a protective cover, monitoring and maintenance.
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Alternative F - Excavation/Off-Site RCRA Disposal of contaminated soils. Installation of a
protective cover (cap) over the excavated area.
Alternative G - Excavation/On-Site Thermal Treatment/Disposal with placement of the treated
material into the excavated area and installation of a protective cover (cap).
7.4 Sanitary Landfills, Lime Ponds, Strong Brine Pond, Mercury CELL Plant and Well Sand Residue
Area.
Alternative Bl - Containment area Inspection/ maintenance, additional groundwater monitoring in
areas not encompassed by the RCRA compliance monitoring, e.g., the sanitary landfill areas.
Alternative B2 - Containment area Inspection/Maintenance, expanded groundwater and surface water
monitoring in all areas.
Alternative Cl - Containment area Inspection/ Maintenance with installation of additional
protective cover over and additional groundwater monitoring of the Sanitary Landfills.
Additional cover over the Lime Ponds and Strong Brine Pond.
Alternative C2- Containment/Consolidation/ Inspection (Sanitary Landfills/Lime Ponds/Strong
Brine Pond/Well Sand Residue Area) - Additional groundwater monitoring
8.0 SUMMARY OF THE COMPARATIVE ANALYSIS OF ALTERNATIVES
This section of the ROD provides the basis for determining which alternative provides the best
balance with respect to the statutory balancing criteria in Section 121 of CERCLA, 42 U.S.C.
Section 9621, and in the NCP, 40 C.F.R, Section 300.430. The major objective of the FS was to
develop, screen and evaluate alternatives for the remediation of the Olin Site. A wide variety
of alternatives and technologies were identified as candidates to remediate the contamination at
the Olin Site. These were screened based on their feasibility with respect to the contaminants
present and the site characteristics. After the initial screening, the remaining
alternatives/technologies were combined into potential remedial alternatives and evaluated in
detail. The remedial alternative was selected from the screening process using the following
nine evaluation criteria:
• Overall protection of human health and the environment;
• Compliance with applicable and/or relevant Federal or State public health or
environmental standards;
• Long-term effectiveness and permanence;
• Reduction of toxicity, mobility or volume of hazardous substances or contaminants;
• Short-term effectiveness or the impacts a remedy might have on the community,
workers or the environment during the course of implementation;
• Implementability, that is, the administrative or technical capacity to carry out the
alternative;
• Cost-effectiveness considering costs for construction, operation, and maintenance of
the alternative over the life of the project, including additional costs should it
fail;
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• Acceptance by the State and
• Acceptance by the Community.
The NCP categorizes the nine criteria into three groups:
(1) Threshold Criteria - overall protection of human health and the
environment and compliance with ARARs (or invoking a waiver) are
threshold criteria that must be satisfied in order for an
alternative to be eligible for selection;
(2) Primary Balancing Criteria - long-term effectiveness and
permanence; reduction of toxicity, mobility or volume;
short-term effectiveness; implementability and cost are primary
balancing factors used to weigh major trade-offs among
alternative hazardous waste management strategies; and
(3) Modifying Criteria - state and community acceptance are
modifying criteria that are formally taken into account after
public comments are received on the proposed plan and
incorporated in the ROD.
The selected alternative must meet the threshold criteria and comply with all ARARs or be
granted a waiver for compliance with ARARs. Any alternative that does not satisfy both of these
reguirements is not eligible for selection. The Primary Balancing Criteria is the technical
criteria upon which the detailed analysis of alternatives is primarily based. The final two
criteria, known as Modifying Criteria, assess the public's and the state agency's acceptance of
the alternative. Based on these final two criteria, EPA may modify aspects of a specific
alternative.
The potential action specific, chemical specific and State ARARs are presented in the following
tables.
-------
A = APPLICABLE REQUIREMENTS WHICH WERE PROMULGATED UNDER FEDERAL LAW TO SPECIFICALLY ADDRESS A
HAZARDOUS SUBSTANCE, POLLUTANT, CONTAMINANT, REMEDIAL ACTION LOCATION OR OTHER CIRCUMSTANCE
AT THE OLIN SITE.
R & A = RELEVANT AND APPROPRIATE REQUIREMENTS WHICH WHILE THEY ARE NOT "APPLICABLE" TO A HAZARDOUS
SUBSTANCE, POLLUTANT, CONTAMINANT, REMEDIAL ACTION, LOCATION, OR OTHER CIRCUMSTANCE AT THE
OLIN SITE, ADDRESS PROBLEMS OR SITUATIONS SUFFICIENTLY SIMILAR TO THOSE ENCOUNTERED AT THE
OLIN SITE THAT THEIR USE IS WELL SUITED TO THE SITE.
ACTION-SPECIFIC FEDERAL ARARS FOR THE OLIN SITE
CLEAN WATER ACT - 33 U.S.C. 1251-1376
40 CFR Part 122, 125 - National Pollutant Discharge Elimination Requires permits for the discharge of pollutants for any point source into
A System waters of the United States.
40 CFR Part 403 - National Pretreatment Standards Sets standards to control pollutants which pass through or interfere with
R & A treatment processes in public treatment works or which may contaminate
sewage sludge.
RESOURCE CONSERVATION AND RECOVERY ACT - 42 U.S.C. 6901-6987
40 CFR Part 257 - Criteria for Classification of Solid Waste Disposal Establishes criteria for use in determining which solid waste disposal
Facilities and Practices facilities and practices pose a reasonable probability of adverse effects on
A public health or the environment.
40 CFR Part 262 - Standards Applicable to Generators of Establishes standards for generators of hazardous wastes.
A Hazardous Waste
40 CFR Part 263 - Standards Applicable to Transportation of Establishes standards which apply to transporter of hazardous waste
R & A Hazardous Waste within the U.S. if the transportation requires a manifest under 40 CFR
Part 262.
40 CFR Part 264 - Standards for Owners and Operators of Establishes minimum national standards which define the acceptable
A Hazardous Waste Treatment, Storage and Disposal (TSD) Facilities management of hazardous wastes for owners and operators of facilities
which treat, store or dispose of hazardous wastes.
40 CFR Part 268 - Land Disposal Identifies hazardous wastes that are restricted from land disposal and
A describes those circumstances under which an otherwise prohibited waste
may be land disposed.
-------
SAFE DRINKING WATER ACT
A 40 CFR Parts 144 - 147 - Underground Injection Control Regulations
HAZARDOUS MATERIALS TRANSPORTATION ACT 49 U.S.C. 1801-1813
R & A 40 CFR Parts 107, 171-177 - Hazardous Materials Transportation
Regulations
Provides for protection of underground sources of drinking water
Regulates transportation of hazardous materials.
CHEMICAL-SPECIFIC FEDERAL ARARS FOR THE OLIN SITE
CLEAN WATER ACT - 33 U.S.C. 1251-1376
A 40 CFR Part 131 - Ambient Water Quality Criteria reguirements
40 CFR Part 403 - National Pretreatment Standards
R & A
RESOURCE CONSERVATION AND RECOVERY ACT - 42 U.S.C. 6901-6987
A 40 CFR Part 261 - Identification and Listing of Hazardous
Wastes
40 CFR Part 262 - Standards Applicable to Generators of
A Hazardous Waste
CLEAN AIR ACT - 42 USC Section 7401 - 7642
40 CFR Part 50 - National Primary and Secondary Ambient Air
A Quality Standards
SAFE DRINKING WATER ACT - 40 USC Section 300
A 40 CFR Part 141 - National Primary Drinking Water Standards
Suggested ambient standards for the protection of human health and aguatic
life.
Sets standards to control pollutants which pass through or interfere with
treatment processes in publicity-owned treatment works which may
contaminate sewage sludge.
Defines those solid wastes which are subject to regulation as hazardous
wastes under 40 CFR Parts 263-265 and Parts 124, 270, and 271.
Establishes standards for generators of hazardous waste.
Establishes standards for ambient air guality to protect public health and
welfare.
Establishes maximum contaminant levels (MCLs) which are health-based
standards for public water systems.
-------
CHEMICAL-SPECIFIC FEDERAL ARARS FOR THE OLIN SITE
PL No. 99-339 100 Stat.462 (1986) - Maximum Containment
A Level Goals (MCLGs).
Establishes drinking water quality goals set at levels of no known or
anticipated adverse health effects with an adequate margin of safety.
STATE OF ALABAMA ARARS FOR THE OLIN SITE
REGULATION
APPLICABLE OR
RELEVANT AND
APPROPRIATE
BASIS FOR
DETERMINATION
Alabama Water Pollution Control Act code of Alabama, Title 22,
Chapter 22 - Water Improvement Commission)
Applicable requirement
which was promulgated
by the state of Alabama to
specifically address a
hazardous substance,
pollutant, contaminant,
remedial action location
or other circumstance at
the site.
Establishes
standards for
limits of pollution
and quality of
water.
Alabama National Pollutant Discharge Elimination System
Permit Regulations (Alabama Administrative Code, Department
of Environmental Management, Water Division, Water Quality
Program, Chapter 335-6-6 NPDES; adopted October 19, 1979;
amended January 24, 1989)
Applicable requirement
which was promulgated
by the state of alabama to
specifically address a
hazardous substance,
pollutant, contaminant,
remedial action location
or other circumstance at
the site.
State
administered
permit program
comparable to the
national permitting
system.
-------
Alabama primary drinking water standards (Alabama
administrative code, department of environmental management,
water division - water supply program, chapter 335-7-2 primary
drinking water standards; adopted January 4, 1989)
Applicable reguirement
which was promulgated
by the state of Alabama to
specifically address a
hazardous substance,
pollutant, contaminant,
remedial action location
or other circumstance at
the site.
Applicable to
water systems
reguired to
monitor for
various
contaminants.
Maximum Concentration of Constituents for Groundwater
Protection (Alabama Administration Code, Department of
Environmental Management, Hazardous Waste Program,
Chapter 335-14-5.06-Releases from Solid Waste Management
Units; adopted June 8, m 1983; amended January 25, 1992)
Applicable reguirement
which was not promulgated
by the state of Alabama to
specifically address a
hazardous substance,
pollutant, contaminant,
remedial action location
or other circumstance at
the site.
Applies to
owners/operators
of facilities that
transport, store, or
dispose of
hazardous waste.
The following tables represent an analysis of the evaluation of alternatives for remediating the Olin
Site under each of the criteria. A comparison is made between each of the alternatives for
achievement of a specific criterion.
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TABLE 8-4
SUMMARY OF DETAILED ANALYSIS
OU-1 GROUNDWATER
Present Worth
Overall Protection
of Human Health
Alternative and Environment
Short-Term Effectiveness Implementability
Alternative A:
No short-term adverse
effects.
No Action with
May not be protective.
Already Implemented
Cost
Estimate
($1,000)
None
Although Olin is committed by
Compliance
With ARARs
May not comply:
RCRA permit levels, MCLs and
Long-Term Effectiveness
and Permanence
Reduction of Toxicity, Mobility
and Volume
Effectiveness and permanence Reduces toxicity, mobility and
dependent on ability of the RCRA volume of some contaminants but
permit to address all areas of will not address the area of dense
Continuation of the RCRA post-closure permit to
accumulation.
Existing RCRA CAP operate the CAP until the ARARS. May comply with
established clean-up standards are action-specific ARARs.
achieved the CAP does not However, the existing RCRA
address all areas of contamination permit can not address the
at the Site. Specifically the area HSWA reguirements under
of dense brine accumulation and Federal law and regulation.
possible offsite contamination.
MCLGs are chemical-specific
contamination at the site.
brine
Alternative Cl:
Effective over long term.
extraction wells are
already implementable as
Extraction/
dependent on
Treatment/
remediating potential
Discharge
areas.
health risks from
Protective:
Reduces toxicity,
$3,91
Would Comply:
mobility and
Minimal short term adverse Vertical
volume in the aguifer.
effects from potential
Adds to protectiveness of existing Would reduce time period for Permanence
worker exposure during demonstrated by the existing
CAP with accelerated compliance with chemical- effectiveness at
Contaminants would be transferred well installation. CAP.
contaminated removal. specific ARARs. source
to air and carbon.
Treatability testing may be
Human
-------
(Vertical Extraction Would control off-site migration. System would be implemented Disposal of carbon reduces exposure during
reguired to design TDS
Wells) to comply with action-specific mobility.
sampling/operation and treatment.
ARARs. volatile emissions are
considered negligible.
There are no known location-
specific ARARs for OU-1
groundwater.
Alternative C3: Protective: Would Comply: Effective over long term. Reduces toxicity, mobility and
Minimal short term adverse Vertical extraction well $4,570
volume in aguifer. effects from potential
would be readily
Extraction/ Adds to protectiveness of existing Would reduce time period for Permanence dependent of worker exposure during implementable.
Treatment/ CAPs with accelerated compliance with chemical- effectiveness at remediating potential Contaminants would be
transferred well installation.
Discharge contaminant removal. specific ARARs. source areas. to air and carbon.
Horizontal extraction wells
Human health risks from are implementable but
(Vertical and Would be implemented to Disposal of carbon reduces exposure during
reguire specialized
Horizontal Extraction Would control off-site migration. comply with action-specific mobility.
sampling/operation and eguipment and contractors.
Wells) ARARs. volatile emissions are
considered negligible.
Treatability testing may be
There are no known location- reguired to design TDS
specific ARARs for OU-1 treatment.
groundwater.
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TABLE 8-5
SUMMARY OF DETAILED ANALYSIS OU-1 SOIL
OLD PLANT (CPC) LANDFILL
Present Worth
Overall Protection
Cost
of Human Health
Estimate
Alternative and Environment
Effectiveness Implementability ($1,000)
Compliance
With ARARs
Long-Term Effectiveness
and Permanence
Reduction of Toxicity,
Mobility and Volume Short-Term
Alternative C: Protective: Would Comply:
There would be little to no Readily implementable: $2,164
Containment (Improved rate of infiltration to the
short-term effects.
Capping) Most areas beneath the landfill Implemented in conjunction with
infiltration. The technology is well
showed concentrations that were the RCRA CAP would comply
clay cover would not demonstrated and could be
below the recommended with chemical-specific ARARs for
Permanence would depend on No reduction in toxicity or be removed completely to prevent
preliminary soil action levels Groundwater. cap maintenance.
construction eguipment and
(PSALs), indicating only
Would result in reduction in Mobility to groundwater
would be reduced with adverse
groundwater. reduced
The existing
implemented with standard
volume.
worker
exposure.
practices.
localized areas may be a
continuing source.
Would be implemented to comply
with action-specific ARARs.
Would reduce infiltration to There are no known location-
groundwater. specifics ARARs for OU-1 soils.
Alternative D: Protective:
Potential
adverse short-term Based on existing information,
workers from could be implemented with
Would Comply:
Would result in reduction in
Reduction in mobility by
$16,155
rate of infiltration to the
reduced infiltration and
adverse effects to
-------
In Situ Stabilization- Most areas beneath the landfill
groundwater. stabilization/solidification
Solidification/ showed concentrations that were
generation.
Containment below the recommended
Contaminants would be
preliminary soil action levels
Short-term
adverse effects are not productivity and
(PSALs), indicating only
residents. implementability.
localized areas may be a
continuing source.
Bench-scale testing and
Implemented in conjunction with
intrusive activity and dust
the RCRA CAP would comply
with chemical-specific ARARs for
Obstructions may hinder
moderate-to-high difficulty.
of residual contamination.
Groundwater.
Would be implemented to comply
with action-specific ARARs.
permanently immobilized.
Volume increase would
characterization
reguired.
Would reduce further
degradation of the Alluvial
Aguifer.
There are known location-
specific ARARs for OU-1 soil.
Alternative E:
Potential
short-term adverse
Protective:
Moderately difficult to
Would Comply:
$30,089
occur due to addition of
regret.
No significant reduction in
toxicity.
Satisfies the statuary
preference of using
treatment as a principal
component.
Would result in reduction in
expected for area
additional
Reduction in mobility by
reduced infiltration and
rate of infiltration to the
from exposure implement.
Excavation/ Most areas beneath the landfill Implemented in conjunction with
groundwater. stabilization/solidification during excavation and handling of
Stabilization- showed concentrations that were the RCRA CAP would comply
material and dust
generation Excavation difficulties may
Solidification below the recommended with chemical-specific ARARs for
Contaminants would be during in situ S/S. occur due to debris in landfill
Containment preliminary soil action levels Groundwater.
permanently immobilized. Volume increase would and proximity of surrounding
(PSALs), indicating only occur due to addition of
off-site adverse structures.
localized areas may be a Would be implemented to comply reagent.
effects to workers
of residual contamination.
Minimal potential
effects with proper
-------
excavation and
continuing source.
controls. Bench-scale testing and
characterization
reguired.
Would reduce further
degradation of the Alluvial
Aguifer.
with action-specific ARARs.
There are no known location-
specific ARARS for OU-1 soils.
No significant reduction in
toxicity
Satisfies the statuary
preference of using
treatment as a principal
component.
engineering
additional
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TABLE 8-5 (Continued)
SUMMARY OF DETAILED ANALYSIS OU-1 SOILS
OLD PLANT (CPC) LANDFILL
Present Worth
Overall Protection
Cost
of Human Health Compliance Long-Term Effectiveness Reduction of Toxicity
Estimate
Alternative and Environment With ARARs and Permanence Mobility and Volume
Short-Term Effectiveness Implementability ($1,000)
Alternative F: Protective: Would Comply: Would result in reduction in Volume of waste on-site
Potential
short-term adverse Moderately difficult to $73,347
rate of infiltration to the would be reduced. effects to workers
from
exposure implement due to excavation
Excavation/ Most areas beneath the landfill Implemented in conjunction with
groundwater. during excavation and
handling of and in situ stabilization/solidifi-
Off-Site RCRA Disposal showed concentrations that were the RCRA CAP would comply Reduction in mobility by
material and dust
generation cation.
below the recommended with chemical-specific ARARs for
Contaminants in upper 15 feet reduced infiltration and during in situ S/S.
preliminary soil action levels Groundwater. would be removed from the stabilization/solidification
Excavation difficulties may
(PSALs), indicating only site. of residual contamination Minimal potential
off-site adverse occur due to debris in landfill
localized areas may be a Would be implemented to comply from 15 to 30 feet. effects with proper
excavation and and proximity of surrounding
continuing source. with action-specific ARARs. Permanent immobilization of engineering
controls. structures.
contamination in residual No reduction in toxicity of
Would reduce further There are no known location-
material (15 to 30 feet) material. Potential for short-term risks to
Bench-scale testing for in situ
degradation of the Alluvial specific ARARS for OU-1 soils. public from
spills during
off-site stability/soldification and
-------
Aquifer.
transportation.
characterization
additional
required.
Would Comply:
Alternative G: Protective:
Potential short-term
adverse Difficult to implement. $108,908
rate of infiltration to the
from exposure
Excavation/ Most areas beneath the landfill Implemented in conjunction with
durinq excavation and handlinq of Bench-scale testinq and
On-Site Thermal showed concentrations that were the RCRA CAP would comply
material and dust
qeneration additional characterization
Treatment below the recommended with chemical-specific ARARs for
Contaminants in upper 15 feet with thermal treatment. durinq in situ S/S.
required.
Disposal preliminary soil action levels Groundwater.
(PSALs) indicatinq only destroyed.
potential off-site adverse Excavation difficulties may
localized areas may be a Would be implemented to comply
proper excavation and occur due to debris in landfill
Would result in reduction in
Reduction in
toxicity/mobility and effects to workers
qroundwater. volume of contaminated
material in upper 15 feet
would be permanently
Reduction in mobility of
residual contamination
Minimal
effects with
continuinq source.
Permanent immobilization of
structures.
Would reduce further
risk to workers durinq
deqradation of the Alluvial
of incinerator
due to Incinerator is complex
Aquifer.
temperature and technoloqy, requires hiqhly-
with action-specific ARARs.
enqineerinq controls.
and proximity of surroundinq
contamination in residual Satisfies the statuary
There are no known location- material (15 to 30 feet). preference of usinq
specific ARARS for OU-1 soils.
component.
equipment.
emission could
affect air quality.
skilled personnel.
A lonq lead time may be
required due to incinerator
availability.
treatment as a principal
hiqh operatinq
complexity of
Potential air
temporarily
Potential
operation
-------
TABLE 8-6
SUMMARY OF DETAILED ANALYSIS OU-1 SOIL AREA
WEST OF FORMER CPC PLANT
Present Worth
Overall Protection
Cost
of Human Health Compliance Long-Term Effectiveness Reduction of Toxicity,
Estimate
Alternative and Environment With ARARs and Permanence Mobility and Volume
Short-Term Effectiveness Implementability ($1,000)
Alternative C: Protective: Would Comply: Would result in reduction in Mobility to groundwater
There would be
little to no Readily implementable: $379
Containment (Extend rate of
infiltration to the would be reduced with adverse short-term effects.
Existing Cap) Soil concentrations were below Implemented in conjunction with groundwater. reduced
infiltration. The technology is well
the recommended preliminary the RCRA CAP would comply
demonstrated and could be
soil action levels (PSALs), with chemical-specific ARARs for
Permanence would depend on No reduction in toxicity or implemented with standard
indicating a low potential for the Groundwater. cap
maintenance. volume. construction eguipment and
soils to be a continuing source. practices.
Would be implemented to comply
Would reduce infiltration to with action-specific ARARs.
groundwater. There are no known location-
specific ARARS for OU-1 soils.
Alternative D: Protective: Would Comply: Would result in reduction in Reduction in mobility by
Potential
adverse short-term Based on existing information, $1,307
rate of infiltration to the reduced infiltration and adverse effects to
workers from could be implemented with
In Situ Stabilization- Soil concentations were below Implemented in conjuction with
groundwater. stabilization/solidification intrusive activity and dust moderate difficulty.
Soldification/ the recommended preliminary the RCRA CAP would comply of residual contamination.
-------
generation.
Containment soil action levels (PSALs), with chemical-specific ARARs for Contaminants
would be Bench-scale testing and
indicating a low potential for the Groundwater.
permanently immobilized. Volume increase would Short-term adverse effects are not additional characterization
soils to be a continuing source. occur due to addition of expected for area
residents. reguired.
Would be implemented to comply reagent.
Would reduce further with action-specific ARARs.
degradation of the Alluvial No significant reduction in
Aguifier. There are no known location- toxicity
specific ARARS for OU-1 soils.
Satisfies the statuary
preference for treatment.
Alternative E: Protective: Would Comply: Would result in reduction in Reduction in mobility by
Potential
short-term adverse Moderately difficult to $2,348
rate of infiltration to the reduced infiltration and effects to workers
from exposure implement.
Excavation/ Soil concentrations were below Implemented in conjunction with
groundwater. stabilization/soldification during excavation and handling of
Stabilization- the recommended preliminary the RCRA CAP would comply of residual contamination.
material and dust generation Excavation may be difficult
Solidification/ soil action levels (PSALs), with chemical-specific ARARs for
Contaminants would be during in situ S/S. because the work would be in a
Containment indicating a low potential for the Groundwater. permanently
immobilized. Volume increase would relative confined area.
soils to be a continuing source. occur due to addition of Minimal potential
off-site adverse
Would be implemented to comply reagent. effects with
proper excavation and Bench-scale testing reguired.
Would reduce further with action-specific ARARs. engineering controls.
degradation of the Alluvial There are no known location- No significant reduction in
Aguifer. specific ARARs for OU-1 soils. toxicity
Satisfies the statuary
preference for treatment.
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TABLE 8-6(Continued)
SUMMARY OF DETAILED ANALYSIS OU-1 SOILS
AREA WEST OF FORMER CPC PLANT
Present Worth
Cost
Alternative
Short-Term Effectiveness
Alternative F:
Potential
short-term adverse
Overall Protection
of Human Health
Estimate
and Environment
Implementability
Protective:
Moderately difficult to
Compliance
With ARARs
($1,000)
Would Comply:
$7,560
Long-Term Effectiveness
and Permanence
Would result in reduction in
Reduction of Toxicity,
Mobility and Volume
Volume of contaminated
soil on-site would be
Soil concentrations were below
reduced.
Implemented in conjunction with
during excavation and
the RCRA CAP would comply
rate of infiltration to the
from exposure
implement.
Excavation/
groundwater.
handling of
Off-Site RCRA Disposal the recommended preliminary
Excavation may be difficult
soil action levels (PSALs), with chemical-specific ARARs for
Contaminants in upper would Contaminated soil would
indicating a low potential for the Groundwater. be
removed from the site. be disposed of in an off- Potential for short-term risks to relative confined area.
soils to be a continuing source. site landfill where mobility
during off-site
Would be implemented to comply would be reduced. No
Would reduce further with action-specific ARARs. reduction in toxicity.
degradation of the Alluvial There are no known location-
Aguifer. specific ARARS for OU-1 soils.
effects to workers
material.
because the work would be in a
public from spills
transportation.
Alternative Gl: Protective:
Potential short-term
adverse Difficult to implement.
Would Comply:
Would result in reduction in
Reduction in
$14,177
from exposure
Excavation/
groundwater.
Soil concentrations were below
volume of contaminated
rate of infiltration to the
Implemented in conjunction with
during excavation and
toxicity/mobility and
effects to workers
-------
handling of Bench-scale testing reguired.
On-Site Thermal the recommended preliminary the RCRA CAP would comply material. material.
Treatment/ soil action levels (PSALs), with chemical-specific ARARs for Contaminants
would be Excavation may be difficult
Disposal indicating a low potential for the Groundwater.
permanently destroyed. Satisfies the statuary Potential risk to workers during because
the work would be in a
soils to be a continuing source. preference for treatment. operation of
incinerator
due to relative confined area.
Would be implemented to comply high operating
temperatures and
Would reduce further with action-specific ARARs. There complexity of
eguipment. Incinerator is complex
degradation of the Alluvial are no known location-specific
technology, reguires highly-
Aguifer. ARARS for OU-1 soils. Potential air emissions could
skilled personnel.
temporarily affect air guality.
A long lead time may be
reguired due to incinerator
availability.
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TABLE 8-7
SUMMARY OF DETAILED ANALYSIS OU-1 SOIL
SANITARY LANDFILLS, LIME PONDS, STRONG BRINE POND,
MERCURY CELL PLANT AND WELL SAND RESIDUE AREA
Present Worth
Overall Protection Cost
of Human Health Compliance Long-Term Effectiveness Reduction of Toxicity, Estimate
Alternative and Environment With ARARs and Permanence Mobility and Volume Short-Term Effectiveness Implementability ($ 1,000)
Alternative A: Protective: Would Comply: Would provide long-term No reduction in toxicity or No short term adverse effects. Implementation is not reguired.
No Action effectiveness and permanance mobility.
The fate transport analysis shows Implemented in conj unction with because no unacceptable risks to
that the four SWMUs/AOCs are the RCRA CAP would comply human health and the
not current sources of with chemical-specific ARARs environment were identified.
groundwater contamination. Risk for Groundwater. Institutional actions (e.g., caps calculations indicate that the soils and monitoring) will indicate if
do not pose unacceptable risks Olin currently complies with
conditions remain protective.
from ingestion, direct contact and action-spedfie ARARs.
inhalation hazards.
There are no known location-
Surface water runoff from these specific ARARS for OU-1 soils.
SWMUs/AOCs would be
detected with the existing
NPDEBS and stormwater
monitoring programs.
mobility, or volume. The
Institutional Actions (Cap Would provide added protection Implemented in conjunction with action)
by ensuring that risk do cap maintenance programs
Inspection/ (over no action) by ensuring the RCRA CAP would comply not
increase. would ensure that the
Maintenance, Groundwater continued maintenance of the with chemical-specific ARARs mobility of constituents
Monitoring near Sanitary caps. for Groundwater. The
alternative is considered would not increase.
Landfills)
permanent even though it
Groundwater monitoring would Would be implemented to
includes long-term maintenance
be extended to the sanitary comply with action-sped fie and
monitoring programs because
landfill area where currently ARARs. to unacceptable risks to human
there is not routine monitoring. health
and the environment were
There are no known location- identified with the no action
specifics ARARS for OU-1 soils.
alternative.
-------
SUMMARY OF DETAILED ANALYSIS OU-1 SOILS
SANITARY LANDFILLS, LIME PONDS, STRONG BRINE POND
MERCURY CELL PLANT AND WELL SAND RESIDUE AREA (Continued)
Present Worth
Cost
Alternative
Short-Term Effectiveness
Overall Protection
of Human Health
Estimate
and Environment
Implementability
Alternative B2:
There would be little to
no Could be easily implemented
Protective:
Compliance
With ARARs
($1,000)
Would Comply:
Long-Term Effectiveness
and Permanence
Would provide some added long-
Reduction of Toxicity,
Mobility and Volume
No reduction in toxicity,
$4,360
term effectiveness (over no
Implemented in conjunction with
not
effects
Institutional Actions (Cap Would provide added protection
by ensuring that risk do cap maintenance programs
Inspection/ (over no action) by ensuring the RCRA CAP would comply
increase. would ensure that the
Maintenance, Expanded continued maintenance of the with chemical-specific ARARs
Groundwater and Surface caps. Groundwater monitoring for Groundwater. The
alternative is considered would not increase.
Water Monitoring) would be extended to the sanitary permanent
even though it
landfill area where currently Would be implemented to includes
long-term maintenance
there is not routine monitoring. comply with action-specific and
monitoring programs because
ARARs. no unacceptable risks to human
health and the environment were
There are no known location- identified with the no action
specific ARARs for OU-1 soils. alternative. Groundwater and
additional surface water
monitoring in the vicinity of the
lime ponds, strong brine pond
and the mercury cell plant would
have limited effectiveness.
mobility, or volume. The
action)
short-term adverse
mobility of constituents
Alternative Cl:
Protective:
Would Comply:
Would provide some added long-
Mobility would be reduced
-------
There would be little to
no Readily implementable. $8,079
term effectiveness (over no due to the improved caps. short-term adverse
effects.
Containment (Sanitary Would provide added protection Implemented in conjunction with action)
with construction of the
Landfills, Lime Ponds and (over no action) with more the RCRA CAP would comply cap
and the monitoring/ There would be no
Strong Brine Pond)/ competent physical barriers over with chemical-specific ARARs maintenance
programs by reduction in toxicity or
Institutional Actions the sanitary landfill soils, lime for Groundwater. ensuring that
conditions do not volume contamination.
ponds and the strong brine pond.
change
Would be implemented to
Would provide added protection comply with action-specific
(over no action) by ensuring ARARs.
continued maintenance of the
caps. Groundwater monitoring There are no known location-
would be extended to the sanitary specific ARARS for OU-1 soils.
landfill area where currently
there is not routine monitoring.
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SUMMARY OF DETAILED ANALYSIS OU-1 SOILS
SANITARY LANDFILLS, LIME PONDS, STRONG BRINE POND
MERCURY CELL PLANT AND WELL SAND RESIDUE AREA (Continued)
Present Worth
Overall Protection
Cost
of Human Health Complicance Long-Term Effectiveness Reduction of Toxicity,
Estimate
Alternative and Environment With ARARs and Permanence Mobility and Volume
Short-Term Effectiveness Implementability ($1,000)
Alternative C2: Protective: Would Comply: Would provide some added long- Mobility would be reduced
There would be little to
no Readily implementable. $8,352
term effectiveness (over no due to the improved caps. short-term adverse
effects
Consolidation/ Would provide added protection Implemented in conjunction with action)
with construction of the
Containment (Sanitary (over no action) with more the RCRA CAP would comply caps and the monitoring/ There would be
no
Landfills, Lime Ponds, competent physical barriers over with chemical-specific ARARs
maintenance programs by reduction in toxicity or
Strong Brine Pond and the sanitary landfill soils, lime for Groundwater ensuring that
conditions do not volume of contamination.
Well Sand Residue ponds and the strong brine pond, change.
Area)/Institutional Actions and containment of the well sand Would be implemented to
residue. comply with action-specific Containment of the well sand
ARARs. would provide marginal, if any,
Would provide added protection added
effectiveness because it is
(over no action) by ensuring There are no known location- a
cemented material with mercury
continued maintenance of the specific ARARS for OU-1 soils.
bound in the matrix.
caps. Groundwater monitoring
would be extended to the sanitary
landfill area where currently
there is not routine monitoring.
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8.1 STATE ACCEPTANCE
The State of Alabama has concurred with the selected remedy.
8.2 COMMUNITY ACCEPTANCE
Based upon comments received, the reaction of the community has been generally favorable.
9.0 SUMMARY OF SEIiECTED REMEDY
Based upon consideration of the requirements of CERCLA, the NCP, the detailed analysis of
alternatives and public and state comments, EPA has selected a source control and groundwater
remedy for OU #1 of the Site. The remedy consist of the following:
Old Plant (CPC) Landfill - Alternative C - Containment (Improve Capping with additional
Groundwater Monitoring)
Area West of Former CPC Plant - Alternative C - Containment which will include extension
of the cap which exist in the area of the CPC plant, monitoring, and maintenance.
Sanitary Landfills, Lime Ponds, Strong Brine Pond, Mercury CELL Plant, and Well Sand
Residue Area - Alternative Bl-Containment area Inspection/ maintenance, additional
groundwater monitoring in areas not encompassed by the RCRA compliance monitoring, e.g.,
the sanitary landfill areas.
GROUNDWATER - Alternative C3 - Extraction (Additional Vertical and Horizontal
Wells)/Treatment/Discharge
The selected remedy provides for the following:
1. Extracting contaminated groundwater from horizontal and vertical
wells and treatment of the extracted groundwater;
2. Upgrading the existing cap over the old plant (CPC) landfill with
a multimedia cap and performing additional groundwater monitoring
in the vicinity of the landfill. The CPC landfill cap will be
extended to encompass the former drainage ditch area;
3. Extending the clay cap that exists over the former CPC plant to
the west, capping the contaminated soils;
4. Additional groundwater monitoring in the vicinity of the sanitary
landfills. In the event that monitoring indicates releases from
this area, additional corrective action measures will be required;
5. Quarterly monitoring and maintenance of the existing clay caps
over the sanitary landfills, the lime ponds, and the strong brine
pond, the asphalt cover over the mercury cell plant, and the
fencing around the well sand residue area. The findings of the
inspections will be documented. If an inspection noted problem
areas such as erosional areas, cracks in the asphalt, or
insufficient cap depth, maintenance or corrective measures will be
required. Maintenance and corrective measures will also be documented;
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6. Monitoring to determine the effectiveness of the groundwater
treatment in reducing the contaminant migration; and
7. Institutional controls for land use and groundwater use restrictions.
The estimated present worth cost of the selected remedy is $10,339,000. The estimates were based
on a variety of information, including estimates from vendors, generic unit costs, and
conventional cost estimating guides. Capital and operation and maintenance costs were estimated
for each alternative and were used to calculate present net worth. The estimated present worth
costs for the major components of each alternative are summarized in Section 5 of the
Feasibility Study.
A. GROUNDWATER REMEDIATION
Groundwater remediation with extraction of contaminated groundwater from horizontal and vertical
wells.
A.I. The major components of groundwater remediation to be implemented include:
• Extraction and onsite treatment of groundwater;
• Institutional controls, such as deed and land-use restrictions.
A. 2. Extraction, Treatment, and Discharge of Contaminated Groundwater
Installation of horizontal and vertical wells for extraction of contaminated groundwater.
The horizontal extraction wells would be designed to capture the area of dense brine
accumulation. The vertical extraction wells will be designed to accelerate removal of
organics from the area of the old plant (CPC) landfill. Additional monitor wells will be
installed in the vicinity of the old plant (CPC) landfill to monitor the effectiveness of
the system.
A.3. Performance Standards
a. Treatment Standards
Groundwater shall be treated until the following maximum concentration levels
are attained at the wells designated by EPA as compliance points.
CLEANUP PERFORMANCE STANDARDS FOR GROUNDWATER
Constituent Cleanup Goal(• g/1)
Alpha-BHC 0.013
Benzene 5
Chlorobenzene 100
1, 2,4-Trichlorobenzene 70
1,2-Dichlorobenzene 600
1,3-Dichlorobenzene 75
1,4-Dichlorobenzene 75
Mercury 2
Pentachlorobenzene 29
Pentachloronitrobenzene 0.29
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It may become apparent during the implementation or operation of the treatment system
that contaminant levels have ceased to decline and are remaining constant at levels
higher than the treatment standards. In such a case, the system's performance may be
reevaluated by EPA, in consultation with ADEM.
b. Discharge Standards
Discharges from the groundwater treatment system shall comply with all ARARs,
including, but not limited to reguirements of the NPDES permitting program under the
Clean Water Act, 33 U.S.C. { 1251 et seg., and all effluent limits established by EPA.
c. Design Standards
The design, construction and operation of the groundwater treatment system shall be
conducted in accordance with all ARARs, including but not limited to the RCRA
reguirements set forth in 40 C.F.R. Part 264 (Subpart F).]
B. Compliance Monitoring
Groundwater monitoring shall be conducted at this site. After demonstration of compliance with
Performance Standards, the Site groundwater shall be monitored for five years. If monitoring
indicates that the Performance Standards set forth in Paragraph A.3 (a) are being exceeded at
any time after pumping has been discontinued, extraction and treatment of the groundwater will
recommence until the Performance Standards are once again achieved.
Air emissions during the cleanup will be monitored to ensure safety of workers and residents
near the Site.
Air emissions from the Site will be monitored to ensure compliance with the Clean Air Act. Air
monitoring will be conducted to ensure that contaminant concentrations do not exceed levels
considered to be safe for human health. If levels are exceeded, mitigative procedures such
as dust suppression or vapor capture will be employed to prevent harmful levels of air emissions
from leaving the Site.
C. Source Control
Source control remediation will address active remediation of the Old Plant (CPC) Landfill
(including the drainage ditch), and the Area West of the Former CPC Plant. It also includes
additional groundwater monitoring in the vicinity of the sanitary landfills and institutional
actions for the other SWMUs, i.e., the sanitary landfills, the lime ponds, and the strong brine
pond, the mercury cell plant, and the well sand residue area.
C.I. The major components of source control to be implemented include:
Upgrading and extending the existing cap over the old plant (CPC) landfill with a multimedia cap
and performing additional groundwater monitoring in the vicinity of the landfill. The CPC
landfill cap will be extended to encompass the former drainage ditch area. The clay cap
that exists over the former CPC plant will be extended to the west, capping the contaminated
soils; Quarterly monitoring and maintenance of the existing clay caps over the sanitary
landfills, the lime ponds, and the strong brine pond, the asphalt cover over the mercury cell
plant, and the fencing around the well sand residue area will be established. The findings of
the inspections will be documented. If an inspection noted problem areas such as erosional
areas, cracks in the asphalt, or insufficient cap depth, maintenance or corrective measures will
be reguired. Maintenance and corrective measures will also be documented; Additional
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groundwater monitoring in the vicinity of the sanitary landfills will be implemented. In the
event that monitoring indicates releases from the sanitary landfills, additional corrective
action measures will be reguired.
C.2. Performance Standards
The performance standards for this component of the selected remedy include, but are not limited
to, the following excavation and treatment standards:
a. Standards for containment:
The caps over the Old Plant (CPC) Landfill (including the drainage ditch), and the
Area West of the Former CPC Plant shall be designed to encompass all soils where the
level of contamination exceeds the levels specified in the table below.
CLEANUP PERFORMANCE STANDARDS FOR SOILS1,2
Constituent Soil Cleanup Goal (mg/kg)
Benzene 5
Chlorobenzene 79
1,2-Dichlorobenzene 1,645
1,3-Dichlorobenzene 140
1,4-Dichlorobenzene 140
1,2,4-Trichlorobenzene 10,000
Mercury 55
1 Cleanup levels will be developed for Alpha-BHC, Pentachlorobenzene,
Pentachloronitrobenzene if they are encountered during the cleanup.
2 Cleanup levels for soils were developed for the protection of groundwater cleanup
level.
The selected alternative for Operable Unit #1 of the Olin site is consistent with the
reguirements of Section 121 of CERCLA and the National Contingency Plan. The selected
alternative will reduce the mobility, toxicity, and volume of contaminated groundwater at the
Site. In addition, the selected alternative is protective of human health and the environment,
will attain all Federal and State applicable or relevant and appropriate reguirements, is
cost-effective and utilizes permanent solutions to the maximum extent practicable.
Based on the information available at this time, the selected alternative represents the best
balance among the criteria used to evaluate remedies.
The selected remedy will include groundwater extraction and monitoring, during which the
system's performance will be carefully monitored on a regular basis and adjusted as warranted by
the performance data collected during operation. Modifications may include any or all of the
following:
• at individual wells where cleanup goals have been attained, pumping may be
discontinued;
• alternating pumping at wells to eliminate stagnation points;
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• pulse pumping to allow aquifer equilibration and encouraqe adsorbed contaminants to
partition into qroundwater; and
• installation of additional extraction wells to facilitate or accelerate cleanup of
the contaminant plume.
To ensure that cleanup qoals continue to be maintained, the aquifer will be monitored at least
annually for five years following discontinuation of groundwater extraction for those wells
where pumping has ceased.
The decision to invoke any or all of these measures may be made during a periodic review of the
remedial action, which will occur at least every five years in accordance with CERCLA section
121 (c) and the NCP.
10.0 STATUTORY DETERMINATION
The selected remedy satisfies the requirement of CERCLA section 121 to protect human health and
the environment by eliminating and by reducing risks posed through each pathway and population
through treatment. The remedy ensures adequate protection of human health and the environment.
The site risk will be reduced to the 10-6 risk range for carcinogens, and a Hazard Index for
non-carcinogens of less than one.
No short-term risks or cross-media impacts will be caused by implementation of the remedy. The
selected remedy satisfies the requirement of CERCLA section 121 to comply with ARARS.
The selected remedy provides overall effectiveness proportionate to its costs (i.e., is
cost-effective). The selected remedy satisfies the requirement of CERCLA section 121 to utilize
permanent solutions and alternative treatment technologies or resource recovery technologies to
the maximum extent practicable.
The selected remedy provides the best balance of tradeoffs among the alternatives with respect
to the evaluation criteria. Those criteria that were most critical in the selection decision
(i.e., those criteria that distinguish the alternatives most) are: Overall protection of human
health and the environment, compliance with ARARs; reduction of toxicity, mobility and volume
through treatment; long term effectiveness and permanence; state and community acceptance.
11.0 DOCUMENTATION OF SIGNIFICANT CHANGES
There have been no significant changes from the proposed plan.
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APPENDIX A:
RESPONSIVENESS SUMMARY - OLIN CHEMICALS SITE
1. Q. What contamination was found during the Domestic Well survey?
A. No contamination was found at unsafe levels. Only two of the
34 wells which were sampled show any signs of contamination
at all and in those two wells the levels that were found were
well below the level which is considered safe.
2. Q. Why is there no proposal for groundwater monitoring in the
neighborhood just south of River Road?
A. The language in the proposed plan said, "Monitoring wells
would be added to supplement Olin's RCRA guarterly monitoring
program. Land-use restrictions would be applied as EPA
determines appropriate." If the existing monitoring well
network is not adeguate to monitor the potential for
contaminant migration toward off-site residences, additional
wells will be installed.
3. Q. What about air monitoring? Is the air safe? Will the remedy
make sure that the air is safe for nearby residents.
A. The initial analysis of the potential for airborne
contamination did not demonstrate that need. However,
concerns raised at the public meeting have caused EPA to
revisit the proposal. Further analysis of the adeguacy of
the existing air monitoring reguirements will be examined.
Additional air monitoring may be reguired in the cleanup design.
4. Q. How will covering the contamination with a cap help? Won't
the contamination still be able to cause problems.
A. If rainwater is allowed to move into the contaminated soils
there is a potential for groundwater to be contaminated.
Covering the areas of contamination will prevent the
rainwater from moving into the contaminated soils.
5. Q. What about the increased cancer rate in the area. Is this
due to the contamination?
A. Representatives from the Alabama Department of Health have
determined that there is not any indication of an unusual
number of cancers in the area. They explained that because
of the low population density, statistics may show an
alarming increase in the number. That is, if the historical
instance of cancers is 1 every 10 years and in one ten year
period we see 2 cancers, the statistics will indicate a 100%
increase in the cancer rate.
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6. Q. EPA's groundwater cleanup level for alpha-BHC may be
impractical to achieve due to the site's hydrogeology. If it
is determined that certain portions of the aguifer cannot be
restored to their maximum beneficial use, will there be any
provison for reevaluation of the remedial technology employed
or an adjustment of cleanup levels?
A. The language in Section 9 of the ROD states, "Groundwater
shall be treated until the following maximum concentration
levels are attained at the wells designated by EPA as
compliance points. It may become apparent during the
implementation or operation of the treatment system that
contaminant levels have ceased to decline and are remaining
constant at levels higher than the treatment standards. In
such a case, the system's performance may be reevaluated by
EPA, in consultation with ADEM."
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