PB94-964210
EPA/ROD/R06-94/087
February 1995
EPA Superfund
Record of Decision:
Double Eagle Refinery Site
(O.U. 2), Oklahoma City, OK
4/19/1994
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RECORD OF DECISION
DOUBLE EAGLE REFINERY SITE
GROUNDWATER OPERABLE UNIT
OKLAHOMA CITY, OKLAHOMA
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
APRIL 1994
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CONCURRENCE DOCUMENTATION
FOR THE
DOUBLE EAGLE GROUND WATER OPERABLE UNIT
RECORD OF DECISION
Lis4 Price
Peer RevieV ^Committee' Chairper_son
Phj&ip H. Allen
Site Remedial Project Manager
"Mel McFarland
Office of Regional Counsel
Regional Counsel
Barbara Greenfield, tariUMMf Chief# Superfund Branch
Office of4»Real$nal Counsel 6C-W
!arT lldlund, Chief
Superfund Programs Branch 6H-S
Button - Acting Regional Counsel
Office of Regional Counsel 6C
Allyn M. nDavis , Director
Hazardous Waste Management Division 6H
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DECLARATION
DOUBLE EAGLE REFINERY SITE
GROUNDWATER OPERABLE UNIT
Statutory Preference for Treatment
as a Principal Element
is not
Met and Five-Year Review is Required
SITE NAME AND LOCATION
Double Eagle Refinery Site
Oklahoma City, Oklahoma
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for
the Double Eagle Refinery Site (DER site) , in Oklahoma City,
Oklahoma, for the Ground Water Operable Unit. The Source Control
Operable Unit Record of Decision (ROD) for this site was completed
and signed on September 28, 1992. The remedy for the DER site was
chosen 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), and,
to the extent practicable, the National Contingency Plan (NCP).
This decision is based on the Administrative Record for this site.
The State of Oklahoma concurs with the selected remedy.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this
site, if not addressed by implementing the response action selected
in this Record of Decision, may present an imminent and substantial
endangerment to public health, welfare, or the environment.
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DESCRIPTION OF THE SELECTED REMEDY
This Record of Decision (ROD) addresses the contamination in the
groundwater. Principal threat wastes include "pools" of dense non-
aqueous phase liquids (DNAPLs) submerged beneath the ground water
or in fractured bedrock. Although there was no free phase
contamination noted during drilling operations at the site,
certain chemicals were detected that are contaminants associated
with DNAPLs. This Ground Water Operable Unit (GOU) addresses the
principal threat at the site by monitoring the ground water to
ensure that the contaminant levels are reduced with time due to
natural attenuation, once the surface contamination is addressed,
so that the surface contamination will no longer provide a source
of contamination to the ground water.
Past oil production activities have rendered the upper ground water
zone non-useable (Class III aquifer) due to the presence of high
Total Dissolved Solids. The data also suggests the possibility of
an offsite source of contamination. Therefore, implementation of
a ground water recovery and treatment system is not considered
appropriate at tftis time. Plowever, a potential exists for
contaminants to migrate vertically to a potential drinking water
aquifer. Therefore, monitoring to ensure that migration does not
occur is appropriate.
This action is the second and final operable unit for the DER site.
This second operable unit is also referred to as the "Ground Water
Operable Unit" (GOU). The first operable unit for the DER site,
termed the Source Control Operable Unit (SCOU), addressed the
source of contamination both onsite and offsite, which included
surface sludges, contaminated surface water and sediment, and
contaminated soil and debris.
The major components of the selected remedy include:
Installation of additional ground water monitoring wells.
Establishment of a routine monitoring and maintenance
program for ground water sampling and modeling, to
evaluate contaminant level reductions, upon removal of
the surface contaminant source materials.
To the extent that site access is available, new
monitoring wells will be placed to determine whether
there is an off site source of contamination.
A five-year review to analyze the data obtained and
computer modeling to determine if contaminant level
reductions are being achieved as expected, once the
surface source of contamination is stabilized.
Contingency action that could be implemented if the
contaminant concentrations increase or the contaminant
plume migrates horizontally or vertically to a usable
water supply.
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STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the
environment, complies with Federal and State requirements that are
legally applicable or relevant and appropriate to the remedial
action, and is cost-effective. This remedy utilizes permanent
solutions to the maximum extent practicable for the conditions at
the site. However, treatment of the hazardous constituents in the
ground water was found to be inpracticable.
Because this remedy will result in hazardous substances remaining
on site above health-based levels, a review will be conducted
within five years after commencement of remedial action to ensure
that the remedy continues to provide adequate protection of public
health, welfare, and the environment.
ani N.' Saginaw Date
jional Administrator
Region 6
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DECISION SUMMARY
FOR THE
DOUBLE EAGLE REFINERY SITE
GROUNDWATER OPERABLE UNIT
OKLAHOMA CITY, OKLAHOMA
I. SITE NAME. LOCATION. AND DESCRIPTION
The Double Eagle Refinery Site ("DER site", or "the site") occupies
the Southeast Quarter (SE 1/4) of Section 35, Township 12 North,
Range 3 West, Indian Meridian, Oklahoma City, Oklahoma County,
Oklahoma. Located at 1900 NE First Street, the site is bounded to
the north by the Union Pacific Railroad tracks (also referred to as
the ATSF-Santa Fe railroad), and to the west and south by vacant
lots zoned for industrial land use. Martin Luther King Boulevard
lies on the east side of the site as an overpass to the railroad
tracks. The DER site is fenced and extends over approximately 12
acres.
The Fourth Street Refinery Superfund Site ("FSR site") lies about
500 feet northeast of the DER site, just north of the railroad
tracks and just east of Martin Luther King (MLK) Boulevard. The
DER and FSR sites are separated only by the MLK overpass, and
contain very similar waste material since both sites recycled used
oils. Due to the fact that these sites are in such close
proximity, and migration of contaminants in certain cases overlap,
this Record of Decision (ROD) will make reference to the FSR site
as necessary. The FSR site was addressed in a separate ROD. Figure
1 provides'a general location map. Figure 2 provides a schematic
of both the DER and FSR Superfund sites, and shows the location of
each site in relation to the other. Figure 3 provides a site
layout for the DER site.
Although industrial areas immediately surround the site, the land
use within a 1 mile radius of the DER site is mixed industrial and
residential. One residence is located to the north of the railroad
tracks and to the east of Martin Luther King Boulevard, adjacent to
the FSR site. A small neighborhood is located about 1/4 mile to
the north, on the other side of the industrial complex adjacent to
the railroad tracks which border the site. Four schools (Douglas
High School, Dunbar School, Bath School, and Edwards School) are
located within a 1 mile radius of the site. Recreational areas
close to the site include the Douglas Community Center, Douglas
Community Park, and Washington Park. Drug Recovery, Inc. is the
only medical facility located within a 1 mile radius of the site.
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OKLAHOMA
I FOURTH STREET SITE
NORTHEAST FDURW STOEET
NOT TO SCALE
Figure 1 Site 'Location Map
DOUBLE EAGLE AND FOURTH STREET
SUPESFUNO SITES.
OKLAHOMA CITY. OKLAHOMA
R.UOR DANIEL
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The DER site has contributed to offsite contamination at offsite
areas called the "Radio Towet area" and "Parcel H". The Radio
Tower area is located just south of the Double Eagle site and
Parcel H is located just south of the Fourth Street site. The
North Canadian River is located just south of Interstate 35,
approximately one half mile south of the site. Although no
endangered species have been identified in these areas, wildlife in
the area includes migratory fowl and small mammals.
II. SITE HISTORY AND ENFORCEMENT ACTIVITIES
Site History
The Double Eagle Refinery collected, stored, and re-refined used
oils and distributed the recycled product. The refinery was active
as early as 1929 with historical aerial photographs available as
early as 1941. Generally, early refining was conducted on the
western portion of the site and expanded toward the eastern portion
as the operations increased.
The DER recycled approximately 500,000 to 600,000 gallons of used
motor oil per month into finished lubricating oil. The recycling
process consisted of the addition of sulfuric acid, settling, and
filtration with bleaching clays via a filter press. This process
generated approximately 80,000 gallons of oily sludge per month.
Sludges were initially sent to an off-site disposal facility, now
the Hardage Criner Superfund Site located in Criner, Oklahoma.
Later, sludges were disposed of in onsite impoundments and a sludge
lagoon until the late 1960's to early 1970's.
Onsite and offsite visual inspections, by the Environmental
Protection Agency (EPA) Field Investigations Team in May of 1985,
indicated that a preliminary sampling inspection should be
conducted. An Expanded Site Inspection was conducted by EPA in
1987-88 which confirmed that the site should be ranked for
inclusion on the National Priorities List (NPL). . In March 1989,
the DER site was added to the NPL, pursuant to Section 105 of the
Comprehensive Environmental Response, Compensation, and Liability
Act (CERCLA), 42 U.S.C. Section 9605, as amended.
The Remedial Investigation/Feasibility Study (RI/FS) for the
Groundwater Operable Unit (GOU) was initiated in June 1992 for the
DER site; and the RI and FS were both completed in July 1993. Due
to the close proximity of the DER and FSR sites, and due to the
similar types of wastes present at both sites, EPA assigned one
contractor to conduct the RI/FS projects concurrently. Therefore,
distinguishable characteristics of each site could be easily
identified, and mobilization and remedial alternative development
efforts would not be duplicated for the overall study area.
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In conjunction with the site investigations and related studies
performed by the EPA, the U.S. Fish and Wildlife Service
(Department of Interior -DOI) conducted a Preliminary Natural
Resource Survey (PNRS) for the DER site. Technical information was
gathered from site visits, National Wetland Inventory maps, EPA
analytical data, and personal communications with the Oklahoma
Department of Wildlife Conservation (ODWC) and EPA. The study
revealed that the DER site is upgradient of a small "oxbow lake"
(created by damming natural drainage) which lies south of the
Parcel H area. The site is also upgradient of the North Canadian
River. The varied habitat adjacent to the Parcel H ponds, oxbow
lake, and the North Canadian River is capable of supporting good
populations of common urban fish and wildlife species. According
to the PNRS report, a dead opossum and a ring-billed gull was
recovered from the concrete vat (basin), and a dead opossum were
noted in one of the lagoons on site during the site visit by the
DOI.
As a result of the site investigation performed by the DOI (U.S.
Fish and Wildlife) the EPA prepared an "Action Memo" dated
September 13, 1993, which was signed by the Director, Environmental
Services Division. The Action Memo authorizes the EPA to expend
funds to install protective netting over an approximate 2.5 acre
sludge lagoon to preclude access by wildlife, and provide a barrier
to the highly toxic and acidic contamination present at the
surface. The PRPs have been offered the opportunity to conduct the
planned action at the site.
EPA Enforcement Activities
In December 1988 EPA issued" an Unilateral Administrative Order
(UAO) to the site owner, requesting that the north side of the site
be fenced to prevent people and animals from coming into direct
contact with the hazardous substances. The owner complied with the
AO and completed the fencing in February 1989, which mitigated the
immediate risk to public health.
Prior to initiating the RI/FS for the Source Control Operable Unit
(SCOU) in Hay 1990, EPA conducted a search for Potentially
Responsible Parties (PRPs). EPA sent Special Notice letters to 17
PRP's identified in the search. The letters included a
notification of potential liability under Section 107 of CERCLA.
The letters also included a demand for reimbursement of EPA's past
costs as well as an offer affording the PRPs an opportunity to
perform the RI/FS. None of the parties receiving the Special
Notice made a good faith offer to conduct the RI/FS, nor did any
parties offer to reimburse the EPA for the past costs incurred.
EPA conducted the RI/FS for the SCOU as a Fund lead project.
Simultaneously with the performance of the RI/FS, EPA proceeded to
pursue leads regarding other unidentified PRPs. In October 1992,
several previously undiscovered boxes of manifests were located at
the Oklahoma State Department of Health (OSDH) archives, now the
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Oklahoma Department of Environmental Quality (ODEQ), which
contained records of shipments of waste oil and other hazardous
wastes to the DER facility. These manifests were from the time
period of 1980-1982. From these records 46 Special Notice letters
were issued on December 16, 1992. A PRP group formed in January
1993, and the EPA met with the group on February 11, 1993. At this
meeting the EPA provided the PRPs the liability information linking
the PRPs to the site and past cost documentation for funds expended
by the EPA. A group of 22 PRPs made a good faith offer to "cash
out" on March 31, 1993. EPA anticipates future negotiations with
respect to the SCOU.
EPA conducted the RI/FS for the GOU as a Fund lead project also;
however, the newly identified PRP's were sent General Notice
letters on February 9, 1993, affording them the opportunity to
participate in the GOU Remedial Design/Remedial Action, and
informing them of GOU RI/FS activities.
Negotiations with the EPA and the PRPs, pertaining to all aspects
of enforcement activities are ongoing.
State Enforcement Activities
During 1977 and 1978 numerous inspections conducted by the Oklahoma
Water Resources Board (OWRB) indicated that un-permitted releases
of hazardous waste occurred both onsite and offsite. Subsequent
inspections conducted by OWRB revealed that the Double Eagle
facility continued to discharge hazardous substances in violation
of the facility permit. As a result of the unpermitted releases of
hazardous waste, OWRB referred this case to their General Counsel,
seeking a Cease and Desist Order on September 14, 1985.
III. HIGHLIGHTS OF COMMUNITY PARTICIPATION
/
This decision document presents the selected remedial action for
the GOU for the DER Superfund site, in Oklahoma City, Oklahoma.
This action is chosen in accoidance with CERCLA, as amended by the
Superfund Amendments and Reauthorization Act (SARA) and, to the *
extent practicable, the National Contingency Plan (NCP), 40 CFR
Part 300. The decision for this site is based on the
administrative record. An index for the administrative record is
included as Attachment A to this document.
The public participation requirements of CERCLA, sections
113 (k) (2) (B) (i-v) and 117, were met during the remedy selection
process. The Remedial Investigation and the Feasibility Study
reports and the Proposed Plan were released on August 5, 1993, and
were all made available to the public in both the administrative
record and information repositories. The repositories are
maintained at the Ralph Ellison Branch Library, the ODEQ Central
Office in Oklahoma City, Oklahoma, and the EPA Region 6 Office in
Dallas, Texas. The notice of availability for these documents was
published in The Black Chroniclef on August 5, 1993.
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The EPA and ODEQ held an Open House in Oklahoma City on February
18, 1993, to explain the Superfund process and to notify the public
that RI activities for the GOU had begun. The RI fieldwork for the
GOU was discussed and general information about the site as well as
new developments pertaining to the SCOU were provided to the public
by the EPA.
A 30-day public comment period was held from August 5, 1993 to
September 4, 1993. On August 16, 1993, the EPA received a request
for a thirty-day extension in accordance with 40 CFR § 300.430,
from one of the PRP representatives on behalf of the participating
PRPs. On August 27, 1993, the' EPA responded to the PRP
representative granting the 30-day extension request, which
extended the public comment period until October 7, 1993 (due to a
holiday weekend within this period). Two commenters submitted
written comments during the public comment period.
A public meeting was held in Oklahoma City on August 12, 1993. At
this meeting, representatives from the EPA presented information on
the RI, Risk Assessment and FS. EPA and ODE'Q answered questions
about the site, the remedial alternatives under consideration, and
the Proposed Plan of Action. Responses to the comments received at
this meeting, as well as the comments received in writing during
the public comment period, are included in the Responsiveness
Summary, which is included in this ROD as Attachment B.
IV. SCOPE AND ROLE OF OPERABLE UNIT 2 WITHIN THE SITE STRATEGY
During the RI/FS project for the SCOU for the DER site, the issues
related to ground water beneath the site were acknowledged as
complex in comparison to those obvious with respect to the surface
contamination, consisting of the sludges and tar mats, and the
contaminated soil, sediment and surface water. During the
investigations required for ranking the site for inclusion on the
NPL, the resulting reports indicated that there was a continuous
shale layer acting as an "aquitard" beneath the site, since this is
generally the regional geology. However, during the field
investigations conducted as part of the RI for the SCOU, the shale
layer was not present beneath the site. Shallow and deep alluvial
wells were installed around the perimeter of both the DER and FSR
sites, but the determination of vertical and lateral migration of
ground water contaminants required further study. Therefore, the
site was separated into two Operable Units to address the surface
contamination and the ground water problems individually. The
impact of the migration of contaminants in ground water and
possibly to the North Canadian River is addressed in this ROD for
Operable Unit 2 (Ground water Operable Unit - GOU).
Principal threat wastes are those source materials considered to be
highly toxic or highly mobile that generally cannot be reliably
contained or would present a significant risk to human health or
the environment should exposure occur. The principal threats at
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the DER site pertaining to the surface contamination are the acidic
sludges within the sludge lagoon and contaminated ponds. These
were addressed in the SCOU ROD which was signed on September 28,
1992.
Low-level threat wastes are those source materials that generally
can be reliably contained and that would present only a low risk in
the event of a release. The low-level threats at the site are the
contaminated surface soils and tar matrices. These low-level
threat wastes were also addressed in the SCOU ROD. The Remedial
Design for the SCOU was initiated on June 21, 1993.
Principal threat wastes pertaining to ground water are defined as
"pools" of dense non-aqueous phase liquids (DNAPLs) submerged
beneath ground water or in fractured bedrock. The contaminated
ground water in the immediate area of the site is classified as a
Class III aquifer by EPA, and the ODEQ agrees with this
classification." Class III aquifers are considered unusable due to
the presence of Total Dissolved Solids (TDS) in excess of 10,000
parts per million (ppm). The average and maximum concentrations of
TDS in the alluvial aquifer were 2,460 ppm and 13,100 ppm,
respectively; and in the upper portion of the Garber-Wellington
(bedrock) aquifer the TDS were 34,680 ppm and 110,000 ppa,
respectively, for the wells installed at the DER site. The
remedial objectives of the GOU are to minimize potential exposure
by direct contact (which includes accidental ingestion and dermal
contact) or inhalation, and to reduce the potential for migration
of contaminants into the surface waters and useable ground water
supplies.
V. SUMMARY OF SITE CHARACTERISTICS
General Overview
s
The DER site and offsite^areas (Parcel H and the Radio Tower area)
are not located in the 100 year floodplain. Generally, the local
surface drainage flows to the south and east of the DER site.
Prior to construction of Interstate 35, the North Canadian River
meandered through the -adjacent FSR site. During construction of
the highway, the river was diverted to the south side of 1-35, and
is now located approximately one half-mile to the south of the DER
site.
Ponds on the DER site and portions of the Parcel H Area appear on
the National Wetlands Inventory Haps (NWI) (U.S. Dept. of Interior,
Fish and Wildlife Service, 1989). These maps are based on
interpretation of aeprial photographs and not on actual site
surveys.. The NWI maps are prepared by review of the aerial
photographs and do not distinguish between pristine ponds and
sludge lagoons covered with surface water, or other types of waste
water treatment ponds. Migratory fowl have no way of
discriminating between clean and contaminated surface waters,
therefore, the DER site is considered a wetland area until the
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remedial action for the SCOU is complete. Once the SCOU remedy is
implemented, no ponds will remain, and the site will essentially be
left as a dry field. Therefore, the DER site will no longer be a
wetland after the Remedial Action.
The North Canadian River is located just south of Interstate 35,
approximately one-half mile south of the site. Although no
endangered species have been identified for these areas, wildlife
in the area includes migratory fowl and small mammals.
Nine alluvial monitoring wells were installed at the DER site.
Five of the alluvial monitoring wells were installed in the shallow
alluvium with the top of 5 foot screens placed at depths varying
from 10 to 19 feet. The remaining four alluvial wells were
installed with the top of five foot screens placed between 28 to 34
feet below ground surface. Six "bedrock" monitoring wells were
installed around the perimeter of both the DER and FSR sites with
the top of 10 feet screens placed about 5 feet into the top of the
Garber sandstone. The top of the Garber sandstone varies from 25
to 57 feet below ground surface across the DER site. The
monitoring well locations are shown on Figure 4. The terms
"bedrock" or "upper bedrock" used in this ROD shall refer to the
uppermost portion of the Garber-Wellington aquifer, and the terms
may be used interchangeably.
General Geology and Hydrogeology Characterization
The DER site is situated on Quaternary alluvial deposits which
represent recent deposition by the nearby North Canadian River.
The floodplain deposits typically consist of unconsolidated and
interfingering lenses of sand, silt, clay, and gravel. These
alluvial sediments are predicted to have relatively high
permeabilities and porosities. The alluvium in Oklahoma County
ranges in thickness from several inches to 90 feet below ground
surface along the river basin.
Directly below the alluvial deposits are the Garber and Wellington
formations. Regionally, these bedrock formations (i.e., lithified
strata below the alluvial channel fill) have a gentle westward
homoclinal dip of 30 to 40 feet per mile. However, the DER site is
located on the northeast flank of the Oklahoma city oil field
surface anticline. Beneath the site, the dip of the Garber
sandstone is to the east-northeast, which is opposite of the
regional dip. The bedrock formation beneath the DER site begins
approximately 25 to 57 feet below the ground surface.
Collectively, the Garber-Wellington consists of massive, cross-
bedded sandstones irregularly interbedded with siltstones and
shales. The "red bed" sandstones and shales of the Garber and
Wellington Formations are similar in lithology and conform
gradationally. Therefore, these formations are commonly mapped as
a single lithologic unit and classified as a single aquifer (the
Garber-Wellington aquifer). Cross section locations and a Geologic
Cross Section are shown on Figures 5 and 6, respectively.
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The Garber-Wellington aquifer constitutes the most important source
of ground water in Oklahoma County. Wells drilled into the water
bearing zone may penetrate as much as 200 to 300 feet of water
bearing sandstone. Artesian conditions exist below 200 feet in
areas in which the aquifer is overlain by the Hennessey Group. The
depths of municipal, institutional, and industrial wells screened
in the Garber-Wellington range from 100 to approximately 1,000 feet
in Oklahoma County. Yields of wells less than 250 feet deep range
from 5 to 115 gallons per minute (gpm) and average 35 gpm.
Reported yields of wells more than 250 feet deep range from 70 to
475 gpm and average 240 gpm. The principal hydrologic factor
controlling the development of the aquifer for fresh water supply
is the presence of high Total Dissolved Solids (TDS) in the ground
water. Shallow ground water (water encountered at a depth less
than 100 feet) in the area is not used as a water supply due to TDS
levels in excess of 10,000 ppm. The high TDS content in the ground
water is attributed to past oil and gas production activities in
the area.
No drinking water wells currently exist within a 1 mile radius of
the site. Residents and industries in the area utilize water
obtained from reservoirs surrounding the city. Results from
sampling the alluvial ground water beneath the DER site revealed
that the TDS ranged from 310 ppm to 13,100 ppm with an average of
about 2,500 ppm for the nine alluvial wells at the DER site.
Results from sampling the upper bedrock monitoring wells (installed
with a 10 feet screen placed approximately 5 feet below top of
Garber sandstone) indicate TDS from 5,200 ppm to 110,000 ppm with
an average of about 35,000 ppm for the three bedrock wells
installed around the perimeter of the DER site (BMW #1, #2 and #6).
Therefore, this zone is considered a Class III aquifer due to the
high TDS, which would prohibit use of the shallow ground water for
domestic purposes. Class III aquifers are characterized by TDS
concentrations greater than 10,000 parts per million (ppm) . Figure
7 shows the degree of contamination with respect to the TDS, based
on data obtained from sampling from the upper bedrock monitoring
wells.
Site Hydrogeologic Conditions
The site is underlain by unconsolidated deposits of alluvium
material consisting of about 1 to 3 feet of topsoil, beneath which
is a mixture of mostly sandy material mixed with silt and clayey
gravel. The thickness of the alluvium varies from about 25 to 57
feet below the ground surface. Underlying these alluvial deposits
is the bedrock material. The uppermost bedrock formation is the
Garber Sandstone.
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The Hennessey Group formation, predominantly reddish-brown shale
containing some layers of siltstone and fine-grained sandstone,
overlies the Garber-Wellington Formation in parts of the region.
However, this shale layer was not encountered above the Garber-
Wellington aquifer (as originally anticipated) in the deeper
borings drilled at both the DER and FSR sites in March of 1992,
indicating that the shale has been completely removed by erosion in
the area of the site prior to the deposition of the alluvium by the
North Canadian River system. This shale material was originally
believed to have been a continuous layer beneath the site, which
acted as an "aquitard" that separated the upper and lower ground
water aquifers. However, the more recent studies revealed that no
Hennessey shale is present beneath the site, concluding that there
is no aquitard between the upper alluvial material and the bedrock.
Therefore, the upper and lower water bearing zones are
hydraulically connected. Due to the absence of the Hennessey Shale
beneath the site, this Operable Unit was initiated to assess the
vertical migration and potential impact of site contaminants on the
deeper Garber-Wellington aquifer.
In addition, the lateral migration and potential impact of site
contaminants in the ground water on the nearby Canadian River has
been investigated, and the results presented herein. Although the
Garber-Wellington aquifer is the most important source of ground
water in the Oklahoma City area, the City of Oklahoma City
currently receives its public water supply from lakes in the area.
During drilling operations at the site, ground water was
encountered at varying depths that ranged from 7 to 20 feet below
ground surface. Subsequent ground water monitoring indicates that
the ground water levels range from about 7 to 17 feet below the
ground surface. The ground water levels were determined
periodically and exhibited moderate seasonal fluctuations due to
seasonal variations in rainfall.
Nature and Extent of Contamination
The Groundwater RI/FS was focused to provide information for
discrete areas of concern and subsequent migration pathways.
From all the chemicals detected in the ground water at the site,
certain chemicals were identified as potential Contaminants of
Concern (COC) based on the COCs from the SCOU. The RI/FS revealed
that numerous contaminants similar to those found in the sludges,
sediments, and soils onsite, were detected in the ground water
sampled from the alluvial and upper bedrock monitoring wells. The
contaminants found were primarily organic chemicals and heavy
metals related to the refinery process. The most commonly found
organic chemicals were Chlorinated Hydrocarbons and Benzene
compounds. Lead was the primary metal contaminant found in ground
water samples taken during the investigation. The COCs are
discussed in detail in Section VI - Summary of Site Risks.
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Other chemicals detected . consisted of Dichloroethane,
Trichloroethane, and Dichlorobenzene. Some or all of the
contaminants identified in this section are "hazardous substances"
as defined in Section 101(14) of CERCLA, 42 U.S.C. § 9601(14), and
40 C.F.R. § 302.4. Although there was no free phase contamination
noted during drilling operations, these chlorinated benzene
compounds are contaminants associated with Dense Non-Aqueous Phase
Liquids (DNAPLs), and suggest the presence of DNAPLS at the site.
A summary of the ground water sampling data is presented in Table
1. The maximum, minimum, and mean concentrations of contaminants
were calculated for all samples collected at all screen depths.
This data represents the contamination encountered in the alluvial
and upper portion of the Garber-Wellington (bedrock) aquifer.
Ground water samples taken at the site also contained high
concentrations of Total Dissolved Solids (TDS). All three upper
bedrock monitoring wells have shown concentrations equal to or
greater than 10,000 ppm, indicating that the upper portion of the
Garber-Wellington (bedrock) aquifer in the vicinity of the site is
a Class III aquifer according to the EPA Ground Water
Classification System.
Samples were collected from both the alluvial and upper portion of
the Garber Wellington (bedrock) aquifers, to identify the level of
contamination in the ground water. Data obtained from the bedrock
monitoring wells represented the current level of contamination at
a depth (60 feet) of the assumed future residential well. Data
obtained from the upper aquifer were used in ground water modeling
to predict the concentration in the lower aquifer at a future date
and to determine exposure point concentrations for the risk
calculations.
The results of the ground water samples were used in a model to
predict worst-case contamination levels in an imaginary drinking
water well located in the top of the bedrock aquifer at the DER
site boundary. The model was also used to predict the impact that
a contaminant plume in the alluvial aquifer may have on the North
Canadian River. In developing the model, it was assumed that the
regional ground water gradient is to the southeast. Modeling was
also performed to estimate the extent of contamination in the upper
portion of the Garber-Wellington (bedrock) aquifer. These results
were used to estimate the risk from potential use of the bedrock
aquifer as a drinking water supply.
Contaminant Migration in the Alluvial Aquifer
The water level measurements taken in conjunction with the RI
reveal that a downward ground water gradient exists at the site;
however, any mounding effect, due to standing water on the ponds.
and lagoon, beneath the DER site is considered negligible.
Regionally, the ground water in the alluvium flows towards the
North Canadian River (southeast). The average ground water flow
rate for the DER site was estimated to be 20 ft/year for the
17
-------
Table 1
Monitoring Well Statistical Data Summary
PARAMETER
NO. OF
DETECTS
MAXIMUM
(UG/U
MINIMUM
(UG/l)
MEAN
(UQJD
Ahiinlnutn
23/36
67900 JO
152 JO
1080238
Atmnwoy
14.70
1470
1435
Amnfc
25/36
149.00
52)
1484
Barium
3936
14/30
1790.00
4 JO
116X0
1JO
53180
1.13
Cadmium
1/38
1.30
1JO
1.65
Ctfckim
36/36
1190000.00
77400 JO
29292222
Chroinhin
17)36
71.90
2 JO
1143
Cobrt
1506
29.40
5.70
638
GOBBflf
*^*rt^^_
8/38
22J60
7.35
Iran
31/36
55600.00
1710 M
16295/16
27/36
73120
1.70
1404
36/36
375000.00
12700 JO
77936.11
36/36
5350 JO
310X0
165942
metal
11/86
54.10
7.40
13J7
86/36
24200 JC
630JC
941040
12JO
2.10
2J2
35/36
3130000JO
120JO
395531.11
30/36
160X0
3JO
43JB3
ano
2S86
214 JO
7^40
8408
VaytCMortda
«M
27JO
13/38
12.00
1JO
1(V36
380JO
4 JO
2341
CvbonOtaAto
»JO
»M
1.1
1/86
2JO
2JU
1.1
7/86
12JO
2JO
13-00110
29JO
3J»
SJB
36JO
22JO
8JBB
2/38
7JO
1.1.1-TOtiJoiD^htlM
1/B6
4JO
4JB
1100
2JB
4JZ
11AJ8
240X0
2J>
12.19
2O6
88X0
1/B6
5/38
200X0
10X9
406
170X0
HUB
886
IXO
OJO
OJO
8X0
txo
8.14
8/96
87X0
1X0
1/B8
8X0
1/B8
2X0
2X0
7X0
2X0
5.11
35X0
OJD
1M
5.H
3/36
&BO
1X0
1/n
oxo
0/40
12/96
2X0
OJ90
4.11
108
5.18
14/38
200X0
050
1/18
0X0
4J7
1g7
0.11
0.11
OJN
2B7
18
0X7
0X8
-------
contaminant transport model. The major source areas for the
alluvial aquifer were assumed to occur at areas where sludge
material was placed in the past, and standing water was observed.
Dispersion represents an important mechanism for contaminant
migration, and results in the spreading of the contaminant plume
and also causes the reduction of maximum concentrations. Figure 8
shows the predicted benzene plume in the alluvial aquifer based on
the most conservative values used for dispersivity. Based on the
results of the model, contaminant concentrations will decrease over
time. Maximum Contaminant Levels for the contaminants of concern
should be attained in 30 to over 150 years. This is discussed in
more detail in Section VI - Summary of Site Risks (Risk Summary).
It is important to note that contaminant mass loading rates were
estimated to provide an estimation of contaminant concentrations at
the current well locations. Although the modelling results
successfully approximate the maximum concentrations of COCs from
four sampling events, seasonal and analytical variability was
observed.
Contaminant Migration in the Bedrock Aquifer
The water level measurements from the upper bedrock monitoring
wells indicate that the flow direction in the upper portion of the
Garber-Wellington aquifer is generally to the south. The average
flow rate for the upper bedrock aquifer was assumed to be 10
ft/year for the contaminant transport model. The major source area
was assumed to be the contamination present in the alluvial
aquifer, since the surface contamination was assumed to have been
removed. Dispersivity values for the bedrock modelling were
considered to be the same as the alluvial aquifer of 50 and 20 feet
for the longitudinal and transverse dispersivity, respectively.
Figure 9 shows the predicted current benzene plume in the bedrock
aquifer based on the aforementioned assumptions. Table 2 shows a
comparison of model predicted contaminant concentrations and
analytical 'results for the samples from the bedrock monitoring
wells. Also, Figure 10 is provided to show the current benzene
plume at 20 ppm, with the respective level of TDS contamination.
Impact on the North Canadian River
The receptor point for the alluvial aquifer was assumed to be the
North Canadian River (River). Figure 11 shows the predicted
benzene plume, when the peak concentration is predicted in the
alluvial aquifer just before discharging to the North Canadian
River. For predicting the impact on the North Canadian River, the
observed contamination in the monitoring wells was attributed to
the DER site.
Table 4 shows the maximum concentration predicted by the model in
the alluvial aquifer just before the ground water is discharged to
the river. The background data in Table 4 are the results of
sampling directly from the river, and indicates that mixing of
19
-------
-------
21
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22
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23
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24
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25
-------
ground water with the surface water in the river reduces
contaminant concentrations significantly. This results in
concentrations significantly below the ambient water quality
criteria for the river as shown in Table 5.
YL SUMMARY OF SITE RISKS
Human Health Risks
As part of the Remedial Investigation for the 6OU at the DER site,
a quantitative risk assessment was performed to estimate human
health risks posed by the migration of contaminants within the
groundwater, and lateral migration of contaminants to surface
waters from the DER site. The methods used in the development of
the risk assessment are based on the following EPA guidance
documents: Risk Assessment Guidance for Superfund. Vol. I: Human
Health Evaluation Manual (Part A). 1989. also known as "RAGS".
Exposure Factors Handbook (1989bl. Risk Assessment Guidance for
Superfund: Volume I; Human Health Evaluation Manual. Part B (EPA
1991). Risk Assessment Guidance for Superfund. Volume lit
Environmental Evaluation Manual (EPA. 1989c). Superfund Exposure
Assessment Manual (EPA. 1988) . Health Effects Assessment Summary
Tables (EPA. 1990c). and the National Contingency Plan. This
section presents a summary of the Baseline Human Health Risk
Assessment for exposure of humans to contaminants existing within
the groundwater that are attributable to the site. The baseline
risk assessment provides the basis for taking action and indicates
i-iie exposure pathways that need to be addressed by the remedial
action. It serves as the baseline indicating what risks could
exist if no action were taken at the site. This section of the ROD
reports the results of the baseline risk assessment conducted for
this site.
The purpose of this risk assessment was to compile and evaluate
information collected in the site investigation in order to
estimate the upper limit of potential health risk which may be
present at the site with respect to ground water. In the
evaluation of potential human exposure scenarios, on-site sampling
and analytical results were used in conjunction with current
federal and state guidance documents and professional judgement to
estimate the potential human health risk attributable to ground
water contamination resulting from past site-related operations.
The "risk" values generated within this human health risk
assessment will reflect the plausible upper limit to the actual
risk of cancer posed by the site under the exposure scenarios
evaluated. These estimates were compared to the EPA's target risk
range of 1 X 10'4 to 1 X 10'6 (1 in 10,000 to l in 1,000,000
respectively) excess cancer risks for hazardous waste site
remediations. The NCP stipulates a 1 X 10"6 risk level as a point
of departure in risk management. When evaluating ground water
contamination, EPA also considers the Maximum Contaminant Levels
(MCLs) in the Safe Drinking Water Act as appropriate remedial
26
-------
s
8
I
I
(S
i
i
jiiiiiH
- «4 *i «>> «>«
27
-------
targets. Such estimates, however, do not necessarily represent an
actual prediction of the risk. Non-carcinogenic impacts are
quantified by the "Hazard Index" which is the ratio of site
concentrations of a contaminant of concern to a reference
concentration that causes a non-carcinogenic impact. EPA's
remedial goal is to reduce the "Hazard Index" at a site to less
than 1.0.
The risk assessment was performed based on the assumption that a
residential well was installed at the site boundary to be utilized
for domestic use. This imaginary well was assumed to be installed
at a depth of 60 feet, which is assumed to be about five to ten
feet into the top of the Carter-Wellington (bedrock) aquifer. This
assumption is considered the "worst case scenario". Also, in
predicting the exposure point concentrations it was assumed that
the surface contamination at the site has been removed and will not
contribute to further ground water contamination.
The calculated risks are based on a well being installed in the
most shallow useable water-bearing zone. Ground water in the
alluvial and upper Garber-Wellington (bedrock) zones is considered
unusable due to TDS concentrations in excess of 10,000 ppm. Since
there are no private wells installed in the vicinity of the site at
the present time, no complete pathway exists for current exposure
to contaminated ground water. However, ground water beneath the
upper portion of the Garber Wellington (bedrock) aquifer (at an
approximate depth of 100 feet) could potentially be used as a
domestic supply. The risk assessment was conducted to estimate the
impact on public health should the pathway be completed in the
future. The risk assessment is based on the establishment of a
future pathway by the installation of an immaginary drinking water
well at the boundary of the site at a depth of 60 feet below the
ground surface. This is the depth at which a well may be screened
in a water supply with relatively low TDS. Calculating the risk
based on a' well installed at this point is the most conservative
method, and results in the most protective risk assessment values.
The values which are calculated in this assessment are considered
representative of the cancer risk posed by the ground water
contamination at the site only in that they represent estimates of
the plausible upper bound limit of what is most probably the risk
range. The true risk within the range of the upper limit and zero
is indeterminable. What is estimated is the projected reasonable
maximum potential additional lifetime cancer risk and potential for
adverse health effects. The reasonable maximum potential risk is
calculated in order to be health protective ("health protective"
assumptions are also referred to as "conservative" assumptions in
risk assessment terminology).
It should be noted that the risk is an additional risk - it is
present in addition to the baseline. The national risk, or
probability, that an individual may develop some form of cancer
from everyday sources, over a 70-year life span is estimated at a
28
-------
baseline of three in ten. Activities such as too much exposure to
the sun, occupational exposures, or dietary or smoking habits
contribute to this high risk. This three in ten probability is
considered the "natural incidence" of cancer in the United States.
To protect human health, the EPA has set the range from one in ten
thousand to one in one million excess cancer incidents as the
remedial goal for Superfund sites. A risk of one in one million
means that one person out of one million people might develop
cancer as a result of a lifetime exposure to the site. This risk
is above and beyond the "natural incidence" of three in ten.
Identification of Chemicals of Concern
Contaminants of concern (COCs) are those contaminants which are
most likely to contribute significant cancer risks or non-cancer
health effects. Fifteen COCs were originally considered for
performance of the risk assessment, since these chemicals provided
an excess risk from the Source.Control Operable Unit (SCOU) - These
contaminants were arsenic, barium, beryllium, cadmium, chromium,
lead, nickel, vanadium, vinyl chloride, 1,2-dichloroethane,
trichloroethane, benzene, chlorobenzene, bis(2-chloroethyl)ether,
and 1,4-dichlorobenzene.
In order to ensure compliance with published EPA guidance and
verify that contaminants with potential toxic effects were not
overlooked, the list of COCs was reanalyzed using a screening
process. Initially, the data set for the bedrock monitoring wells
was evaluated to identify potential COCs since current
contamination is assumed to represent steady-state conditions, and
the source of contamination was assumed to be removed. Under
steady-state conditions, the contaminant mass currently in the
alluvial aquifer would continue to contribute to contamination in
the bedrock aquifer. The data obtained from the bedrock monitoring
wells represented the current level of contamination at the depth
of the "assumed" future residential well. Data obtained from the
alluvial aquifer were used in ground water modeling to predict the
concentration in the bedrock aquifer, and potential risk, at a
future date. This "assumed" future residential well is considered
the worst-case scenario. It is highly improbable that anyone will
use the ground water at this depth due to the presence of high
Total Dissolved Solids (TDS).
As a result of the risk calculations for individual contaminants,
the list of potential COCs was further reduced by eliminating those
contaminants that presented a cancer risk less than 1 in 10,000,000
and a Hazard Index less than 0.1. A summary of the determination
of final COCs for this risk assessment is given in Table 6.
Toxicity Assessment
The objective of the toxicity assessment is to weigh available
evidence regarding the potential for particular contaminants to
cause adverse effects in exposed individuals. Also, the toxicity
29
-------
Table 6
Determination of Final COCs
Double Eagle Site
Contaminants of Concern
Risk
Criterion
Calculated Risk
Exposure Pathway and Receptor
Dermal
Child/Adult
Inhalation
Child/Adult
CARCINOGENS
Aldrin2
Arsenic1
Benzene'
BeryUium'
Bisp-ChloroelhyOEthei1
Chlordane
Chloroform2
4,4-DDE i
1 ,4-^cblorobenzene1
"l ,2-DTcSoroelnane'
l.T-DTchioroelhen?
Heptachlor
Heptachlor Epoxid?
Methylene CUoridi?
Trichloroethene1
Vinyl Chloride1
1E-7
1E-7
1E-7
"ll"7
1E-7
1E-7
1E-7
1E-7
1E-7
1E~7 1
1E-7 J
1E-7
1E-7
1E-7
1E-7
1E-7
NA3
NAT
2.1E-5/4.9E-5
[ NA?
NA3
5.8E-8/1.4E-7
2.0E-7/4.7E-7
1.7E-6/4.0E-6
6.3E-8/1.5E-7
NAT
8.6E-7/2.0E-6
2.4E-6/5.7E-6
NA5
NAT
3.6E-6/8.4E-*
NA3
NA"
"NA*
1.2E^/2.9E-4
- - NA" ~
6.3E-5/1.6E-4
NA"
8.4E-6/2.1E-5
~ ~~NA' '" '
NA4
5.0E-4/1.3E-3
S.2E-5/1.3E-4
" ^NA4
NA4
4.6E-8/1.2E-7
3.0E-6/7.5E-6
1.5E-4/3.8E-4
Ingestion
Child/Adult
1.1E-4/1.8E-4
1.6E-5/3.5E-5
4.7E-5/7.8E-5
OA?
2.5E-5/4.2E-5
6.6E-7/1.1E-6
2.5E-7/4.2E-7
2.9E4)7/4.8E-7
1.4E-7/2.3E-7
2.0E-4/3.3E-4
1.0E-5/1.7E-5
1.9E-5/3.2E-5
5.6E-6/9.4E-6
8.7E-8/1.4E-7
2.2E-6/3.7E-6
3.8E-4/6.3E-4
NON-CARCINOGENS
Acetone2
Aldrin
Arsenic1
Barium"
BayUjumT
2-Butanonr
Cadmium'
CUorobenzene1
vjinQiiiimn
1,1-DTcbloToethane^
trans fi^-Dichloroethene2
Endosul&i?
Ketones2
l>rt'
Manganese^
"Methylene chloride5"
2-Memyl-4-Pentknon?
Nickel1
"Phenol2
2,43>Ln>etnyi Phenof
fhailiun?
Toluene2
Vanadium1
fXylene
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
~NA«
"IE"!
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
1E-1
NAJ
NA5
NA?
NA5
NA1
NA?
NAT" ""
2.1E-3/4.8E-3
NAT
NA?"" "
2.3E-3/5.4E-3
NAy
"' NA'
NAT
~ "NAT" ""
NA*
NAT
NAT
"NAT" "
NAT
N^
9.8E-l/2.3E-fO
"". "NAT" '-
4.6E-3/9.8E-3
NA'
NA4
NA4" ' "
NA4
NA4
NA6
" " NA4
13E-1/6.8E-2
w
1.7E-1/8.4E-2
NA4
NA4
9.5E-1/5.4E-1
' Ny "
' NA4
3.9E-4/2.0E-4
NAf
JNA4
NA4
NAr
NA*
4.8E+0/2.4E+0
'" " NA4 . .'
2.9E+0/1.5E-J-0
1.1E+0/3.7E-1
2.5E+0/8.2E-1
3.5E+0/1.5E+0
1.0E+1/3.3E+0
~" "0.0s"" ""
1.7E-1/5.4E-2
2.0E-1/8.8E-2
1.3E-2/4.5E-3
0/C?
6.7E-2^.3E-2
2.2E-1/6.7E-2
6.0E-1/2.0E-1
~" "NA1" "
NA»"
7.7E+2^.6E+2
1.2E+0/9.9E-2
8.0E"+l72.6E+l
OA?"
3.9E+0/1.3E+0
2.4E-2/8.1E-3
L5E+1/7.3E+6
9.7E-01/3.2E-1
OAF
5.2E02/1.7BQ2
COC from list provided by Remedial Project Manager (Allen 1993).
COC determined by initial screening process described in Section 5.2.2 of this report.
Pathway not applicable to contaminant due to low permeability coefficient. See Section 5.2.4.2 of this report.
Pathway not applicable to contaminant due to low Henry's Law Constant and/or molecular weight See Section
5.2.4.2 of this report.
Contaminant not detected in bedrock wells. No significant change expected.
Ketones evaluated as a group only for the inhalation pathway.
Toxicity values not available for lead.
30
-------
assessment provides, where possible, an estimate of the
relationship between the extent of exposure to a contaminant and
the increased likelihood and/or severity of adverse effects. The
types of toxicity information considered in this assessment
include the reference dose (RfD) used to evaluate noncarcinogenic
effects and the slope factor to evaluate carcinogenic potential.
RfDs have been developed by EPA for indicating the potential for
adverse health effects from exposure to contaminants of concern
exhibiting noncarcinogenic effects. RfDs, which are expressed in
units of mg/kg-day, are estimates of acceptable lifetime daily
exposure levels for humans, including sensitive individuals.
Estimated intakes of contaminants of concern from environmental
media (e.g., the amount of a 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 and to protect sensitive subpopulations) to
ensure that it is unlikely to underestimate the potential for
adverse noncarcinogenic effects to occur. The purpose of the RfD
is to provide a benchmark against which the sum of the other doses
(i.e. those projected from human exposure to various environmental
conditions) might be compared. Doses that are significantly higher
than the RfD may indicate that an inadequate margin of safety could
exist for exposure to that substance and that an adverse health
effect could occur.
No RfD or slope factors are available for the dermal route of
exposure. In some cases, however, noncarcinogenic or carcinogenic
risks associated with dermal exposure can be evaluated using an
oral RfD or an oral slope factor. Exposures via the dermal route
generally are calculated and expressed as absorbed doses. These
absorbed doses are compared to an oral toxicity value that is also
expressed as an absorbed dose. Toxicity information used in the
toxicity assessment for the Site was obtained from the Integrated
Risk Information System (IRIS). If values were not available from
IRIS, the Health Effects Assessment Summary Tables (HEAST) were
consulted.
For chemicals that exhibit noncarcinogenic health effects,
authorities consider organisms to have repair and detoxification
capabilities that must be exceeded by some critical concentration
(threshold) before the health is adversely affected. For example,
an organ can have a large number of cells performing the same or
similar functions. To lose organ function, a significant number of
those cells must be depleted or impacted. This threshold view
holds that exposure to some amount of a contaminant is tolerated
without an appreciable risk of adverse effects.
Health criteria for chemicals exhibiting noncarcinogenic effects
for use in risk assessment are generally developed using EPA's RfDs
developed by the Reference Dose/Reference Concentration ("RfD/RfC")
Work Group and included in the IRIS.
31
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For chemicals that exhibit carcinogenic effects, most authorities
recognize that one or more molecular events can evoke changes in a
single cell or a small number of cells that can lead to tumor
formation. This is the non-threshold theory of carcinogenesis
which purports that any level of exposure to a carcinogen can
result in some finite possibility of generating the disease.
EPA's Carcinogenic Risk Assessment Verification Endeavor (CRAVE)
has developed slope factors (i.e., dose-response values) for
estimating excess lifetime cancer risks associated with various
levels of lifetime exposure to potential human carcinogens. The
carcinogenic slope factors can be used to estimate the lifetime
excess cancer risk associated with exposure to a potential
carcinogen. Risks estimated using slope factors are considered
unlikely to underestimate actual risks, but they may overestimate
actual risks. Excess lifetime cancer risks are generally
expressed in scientific notation and are probabilities. An excess
lifetime cancer risk of 1 x 10"6 (one in one million), for example,
represents the probability that one additional individual in a
population of one million will develop cancer as a result of
exposure to a carcinogenic chemical over a 70-year lifetime under
specific exposure conditions.
Slope factors (SFs) have been developed for estimating excess
lifetime cancer risks associated with exposure to potentially
carcinogenic contaminants 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 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).
There are varying degrees of confidence in the weight of evidence
for carcinogenicity of a given chemical. The EPA system involves
characterizing the overall weight of evidence for a chemical's
carcinogenicity based on the availability of animal, human, and
other supportive data. The weight-of-evidence classification is an
attempt to determine the likelihood that the agent is a human
carcinogen, and thus, qualitatively affects the estimation of
potential health risks. Three major factors are considered in
characterizing the overall weight of evidence for carcinogenicity:
(1) the quality of evidence from human studies; (2) the quality of
evidence from animal studies, which are combined into a
characterization of the overall weight of evidence for human
carcinogenicity; and (3) other supportive information which is
assessed to determine whether the overall weight of evidence
32
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should be modified. EPA uses the weight of evidence classification
system to categorize carcinogenicity of contamination as one of the
following five groups:
Group A - Human Carcinogen: This category indicates that there
is sufficient evidence from epidemiological studies to support
a causal association between an agent and cancer.
Group B - Probable Human Carcinogen: This category generally
indicates that there is at least limited evidence from
epidemiological studies of carcinogenicity to humans (Group
Bl) or that, in the absence of adequate data on humans, there
is sufficient evidence of carcinogenicity in animals (Group
B2)
Group C - Possible Human Carcinogen : This category indicates
that there is limited evidence of carcinogenicity in animals
in the absence of data on humans.
Group D - Not Classified: This category indicates that the
evidence for carcinogenicity in animals is inadequate.
Group E - No Evidence of Carcinogenicity to Humans; This
category indicates that there is no evidence for
carcinogenicity in at least two adequate animal tests in
different species, or in both epidemiological and animal
studies.
Several of the initial chemicals of concern have been classified as
potential carcinogens by EPA. Each of these also have been
assigned a carcinogenicity weight-of-evidence category. These
chemicals are presented in Table 7 with the respective Referenced
Doses and Potency Factors.
Human Risk Characterization
The purpose of the human risk characterization is to estimate and
characterize the potential human cancer risks and non-cancer
adverse health effects associated with exposure to contaminants
released from the site into the ground water.
Exposure pathways evaluated in this risk assessment included dermal
contact, inhalation, and ingestion of contaminants in the ground
water to offsite residents. The pathways were based on the
assumption that a residential well will be installed at the site
boundary.
The risk assessment was based on Reasonable Maximum Exposure (RME)
factors as required by EPA guidance (Longest II 1992). Use of the
RME factors provided a calculation of the highest exposure that
could reasonably be expected for the pathways analyzed. This
conservative calculation is intended to account for uncertainties
in contaminant concentration and variability in exposure parame-
33
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Table 7
Reference Doses and Slope Factors for Contaminants of Concern
Double Eagle Site
Contaminant of Concern
Acetone
Aldrin
Arsenic
Barium
Benzene
|Bu(2-chloioethyl)Ether
2-Butanone
fTpHmtiim
Chlordane
Chlorobenzene
Chlorofonn
4,4-DDE
1,2-DJchloroethane
1 ,4-Dichlorobenzene
1,1-Dichloroetbane
1,1-Dicbloroethene
trans 1,2-Dichloroethene
Endosulfan
Heptachlor
Heptachlor Expoxide
Ketones3
Manganese
Methylene Chloride
2-Methyl-4-Pentanone
Phenol
Thallium
Toluene
TricUoroethene
Vinyl Chloride
Xytene
RfD(O)
ing/kg/day
l.OE-014
3.0E-O5
3.0E-04
7.0E-02
-
_i
6.0E-017
5.0E-04
6.0E-05
2.0E-02
l.OE-02
_i
_i
'
9.0E-03
9.3E-03
2.0E-O2
5.0E-05
5.0E-04
1.3E-05
NA4
5.0E-03
6.0E-02
5.0E-27
6.0E-01
8.0E-05
2.0E-01
-'
_i
2.0E+00
RfD(I)
rng/kg/day
-l
-'
_i
_i
_i
_i
2.9E-01
_i
_i
5.0E-03
_i
_i
-'
[_ 2.0E-01
l.OE-01
_ i
-'
_i
_j
-'
2.9E-01*
l.OE-04
8.6E-01
_i
_i
__i
l.OE-01
_i
-1
9.0E-02
SF(O)
mg/kg/day
NA2
1.7E+01
1.8E+00
NA2
2.9E-02
1.1E+00
NA2
_i
1.3E+00
NA2
6.1E-03
3.4E-01
9.1E-02
2.4E-02
NA2
6.0E-01
NA2
NA2
4.5E+00
9.1E+00
NA4
NA2
7.5EO3
NA2
j
NA2
-'
1.1E-02*
1.9E+00
_i
SF(I)
mg/kg/day
NA2
1.7E+01
5.0E+01
NA2
2.9E-02
1.1E+00
NA2
6.3E+00
_i
NAZ
8.1E-02
_i
9.1E-02
-'
NA2
1.2E+007
NA2 .
NA2
4.5E+00
9.1E+00
_ i
NAZ
1.6E-03
NA2
_J
NA2
^Ji
6.0E-036
3.0E-01
_'
RfD(O) = Oral reference dose for non-carcinogenic effects
RfD(I) = Inhalation reference dose for son-carcinogenic effects
SF(O) Oral slope factor for carcinogenic effects
SF(I) = Inhalation slope factor for carcinogenic effects
- indicates data were not available from IRIS (1993) or HEAST (1992).
NA indicates contaminant hi1* not been dB>pnf"tnted to exhibit carcinogenic effects in
Ketones include acetone, 2-butanooe, 2-hexanone and 2-methyl-4-pentmoae,
Ketones evaluated individually for oral pathway.
RfD for 2-butanone,
Toxiciry factors provided by EPA Region 6 (Rancher 1993a).
Toxicity factors provided by EPA Region 6 (Raucher I993b)
34
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ters. An estimate of average exposure is calculated by using
average or central tendency factors (Central Tendencies are
discussed below).
The exposure point concentrations were based on groundwater
modeling performed in the RI. Exposure concentrations were modeled
for five year time intervals. The highest concentration occurs
atyear 0. Risk calculations fcr child exposure are based on the
assumption that the exposure point concentration remains unchanged
over the six-year exposure duration. The highest risk would,
therefore, occur using the exposure concentrations from year 0.
Risk calculations for adult exposure are completed for five year
intervals and added to account for a 30-year exposure to
contamination in the bedrock water supply system. The highest risk
would, therefore, occur from year 0 through year 29.
Central Tendencies
Based on a February 26, 1992, memorandum from Deputy Administrator
F. Henry Habicht, EPA is required to evaluate both "reasonable
maximum exposure" (RME) and "central tendency" in the risk
assessment at Superfund sites. The exposure assumptions associated
with the RME have been used to estimate the baseline risks and
ultimately the remedial action goals at sites. The "central
tendency" scenario represents the risk from more of an "average"
exposure, compared to a "reasonable maximum" exposure.
A comparison of the differences in the risk assumptions between the
RME and central tendency is shown in Table 8.
Risk Summary
Potential exposures to contaminants in the ground water at the DER
site have been evaluated and the resultant potential for adverse
health effects has been estimated. Exposure scenarios were
developed based on the assumptions that the source of contamination
will be removed, and a residential well will be installed at the
site boundary. The only populations exposed would be the adult and
child residents using the assumed future well. However, it is
highly unlikely that anyone would use the ground water at this
depth (60 feet) for domestic purposes.
Thirty contaminants were identified as COCs based on risks
presented by dermal contact, inhalation exposure, and ingestion of
ground water contaminated by the DER site.
A summary of the risks calculated using RME factors is presented in
Table 9. Cancer risks for both adult and child receptors are above
the EPA goal of 1 in 1,000,000 for all exposure pathways. Cancer
risks for inhalation and ingestion are above the 1 in 10,000 upper
end of acceptability. The total cancer risks from residential
ground water exposure were 36 in 10,000 (3.6E-03) and 17 in 10,000
(1.7E-03) for adults and children, respectively.
35
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Table 8
Exposure Assumptions for Reasonable Maximum Exposure and Central Tendency
Dermal Contact, Ingestion and Inhalation of Groundwater
Off-site Resident Future Use Scenario
Double Eagle Site
DERMAL
Age Group (years)
Days Exposed (per year)
Years Exposed (per 70 year life)
Body Weight (kg)
Surface Area Exposed (cm2)
Hours Exposed per Day (or/day)
Event Frequency (I/day)
INGESTION
Age Group (years)
Days Exposed (per year)
Years Exposed (per 70 year life)
Body Weight,(kg)
Intake Rate (L/day)
Reasonable
Maximum
Exposure
Child
1-6
350
6
15
7200
0.2
1
Adult
18-70
350
30
70
20,000
0.2
1
Central
Tendency
Child
1-6
350
6
15
7200
0.2
1
Adult
18-70
350
9
70
20,000
0:2
1
1-6
350
6
15
1
18-70
350
30
70
2
INHALATION
Age Group (years)
Days Exposed (per year)
Years Exposed (per 70 year life)
Body Weight (kg)
Intake Rate (mVday)
Volatilization Factor (Lfar)
1-6
350
6
15
5
0.5
18-70
350
30
70
15
0.5
1-6
350
6
15
0.7
1-6
350
6
15
5
0.5
18-70
350
9
70
1.4
18-70
350
9
70
15
0.5
36
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Table 9
Risk Summary for Groundwater Exposure
Double Eagle Site
Cancer Risk
Hazard Index (HI)
Pathway
Dermal
Inhalation
Ingestion
Total Risk
Dermal
Inhalation
Ingestion
Total HI
Child
3.0E05
8.9E-04
8.1E-04
1.7E-03
9.8E-01
9.0E+00
8.9E+02
9.0E+02
Adult
7.0E-05
2.2E-03
1.4E-03
3.7E-03
2.3E+00
4.6E+00
3.0E+02
3.1E+02
37
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The Hazard Indices for both adult and child receptors were above
the EPA goal of 1.0 for the ingest ion and inhalation pathways. The
total Hazard Index representing residential ground water exposure
is 310 (3.1E+02) for adults and 900 (9.0E+02) for children.
Results of the risk calculations indicated that adults and children
are at hazard from exposure to contamination in the ground water
for potential carcinogenic and toxic effects.
A summary of the risks calculated using average exposure factors is
presented in Table 10. Although use of these factors decreased the
risks for the adult receptors for the dermal and inhalation
pathways and for adult and child receptors for the ingestion
pathway, the changes were not significant enough to change the
conclusions of this assessment. The total cancer risks from
residential ground water exposure were reduced to 13 in 10,000 and
15 in 10,000 for adults and children, respectively. The total
Hazard Index representing ground water exposure was reduced to 81
for adults and 630 for children.
Site-specific maximum contaminant levels were compared against the
drinking water Maximum Contaminant Levels (MCLs) in Table 11. As
part of the modeling effort, the estimated time for contaminants to
attain MCLs through natural attenuation was calculated. These
calculations were made assuming that the surface contamination was
removed, and would not contribute as a future source of
contamination in the ground water. The MCLs were exceeded for four
metals including barium, cadmium, manganese and thallium. Barium
is expected to reach the MCL by year 65, based on computer modeling
conducted as part of the RI. Manganese is not expected to reach
the MCL level in the next 150 years. Since the concentrations of
cadmium and thallium were not expected to change significantly over
time, no estimate was made as to how long it would take to achieve
MCL levels. Barium, cadmium, manganese and thallium are not
expected to reach acceptable health risk levels in the next 150
years.
Lead was detected in the alluvial wells and was a contaminant of
concern during the SCOU. However, lead was not modelled as part
of the GOU RI because lead was not detected during the first round
of sampling of the upper Garber-Wellington (bedrock) monitoring
wells. Subsequent to the modeling effort however, lead was
detected during the second round of sampling. Three "bedrock
monitoring wells'* (BMWs) are installed around the perimeter of the
DER site. BMW-i and BMW-6 revealed lead at 193 parts per billion
(ppb) and 83.6 ppb respectively. BMW-2 revealed lead at less than
5 ppb, which is below the final cleanup level of 15 ppb considered
protective for ground water usable for drinking water. Therefore,
modeling will be conducted to determine the threat to human health
and the environment posed by lead present in the ground water, as
part of the Remedial Design (RD) for the GOU, when the RD is
initiated.
38
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Table 10
Risk Summary for Groundwater Exposure
Average Exposure Factors
Double Eagle Site
Cancer Risk
Hazard Index (HI)
Pathway
Dermal
Inhalation
Ingestion
Total Risk
Dermal
Inhalation
Ingestion
Total HI
Quid
3.2E-05
8.9E-04
5.8E-04
1.5E-03
9.8E-01
9.4E+00
6.2E+02
6.3E+02
Adult
2.8E-05
8.6E-04
3.7E-04
1.3E-03
8.8E-01
1.8E-01
8.0E+01
8.1E+01
39
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Table 11
Comparison of Contaminant Concentrations
With Drinking Water Maximum Contaminant Levels (MCL)
Double Eagle Site
Contaminant of Concern
Maximum Modelled Concentration
mg/L
MCLs
mg/L
CARCINOGENS
Aldrin
Arsenic
Benzene
Beryllium
Bis(2-chloroethyl)Rher
Chlordane
Chlorofbnn
4,4-DDE
1 ,4-Dichlorobenzene
1 ,2-Dichloroethane
1,1-Dichloroethene
Heptacblor
Heptachlor Epoxide
MeJhylene Chloride
TricbJoroetbene
Vinyl Chloride
1.2E-03
1.7E02
3.0E-01
O.OE+00
4.2E-03
7.6E-05
7.6E-03
1.6E-04
1.1E03
4.0E-01
3.2E-03
7.8E-04
1.1E-04
2.1E-03
3.6E-02
3.6E-02
NON-CARCINOGENS
Acetone
Barium
2-Butanone
fadnnhim
Chlorobenzene
l,l-Dichk>ne%ane
trans 1,2-Dichloroethene
Endosulfai
Ketooes
Lead
Manganese
2-Memyl-4-Pentaoone
Mercury
Nickel
Phenol
Selenium
Thallium
Toluene
Xylsae
1.7E+00
1.1E+01
1.6E-KX)
1.6E-03
4.2E-03
1.1EO1
7.0E-02
4.7E-04
1.7E+00
O.OE+00
6.0E+01
6.3E+01
5.9E-05
O.OE+00
3.7E+01
O.OE+00
1.9E-02
3.0E+00
1.6E+00
NA
5.0E-02
5.0E-03
4.0E-03
NA
NA
l.OE-01
NA
7.5E-02
5.0E-03
7.0E-03
4.0E-04
2.0E-04
NA
5.0E-03
2.0E-03
NA
2.0E+00
NA
5.0E-03
NA
NA
l.OE-01
NA
NA
1.5E-02
5.0E-02
NA
2.0E-03
5.0BO1
NA
5.0E-O2
2.0E-03
l.OE+00
l.OE+01
MCL
Excursion
NA
/
NA
NA
NA
/
y
NA
W
/
NA
/
NA
NA
NA
-
NA
NA
/
NA
NA
/
J
NA = MCL not promnlpatfrd tor this contaminant.
- = Maximum concentration did not exceed the MCL.
Maximum concentration exceeded me MCL.
40
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The MCLs were exceeded by five organics including benzene, 1,2-
dichloroethane, heptachlor, trichloroethane, and vinyl chloride.
These five contaminants were also the major contributors to the
cancer risks calculated for the exposure pathways. Based on
groundwater modeling, benzene is expected to reach the MCL level by
year 145. 1,2-Dichloroethane is expected to reach the MCL level by
year 155. Heptachlor is expected to reach the MCL level by year
30. Trichloroethane is expected to reach the MCL level by year 70.
Vinyl chloride is expected to reach the MCL level by year 105.
Benzene, heptachlor, trichloroethane, vinyl chloride and 1,2-
dichloroethane will take more than 150 years to achieve acceptable
concentrations from a human health risk standpoint.
Contaminants in the groundwater present a hazard for all exposure
pathways. Contaminant concentrations will continue to decrease;
however, some of the contaminant concentrations will remain above
acceptable levels 150 years from now both from a risk and a
regulatory standpoint.
Uncertainties Associated with the Human Health Risk Calculations
Within the Superfund process, baseline quantitative risk assess-
ments are performed in order to assess the potential human health
impacts of a given site under currently existing conditions. They
are performed in order to provide risk managers with a numerical
representation of the severity of contamination present at the
site, as well as to provide an indication of the potential for
adverse public health effects. There are inherent and imposed
uncertainties in the risk assessment methodologies.
This section addresses potential sources of uncertainty in the risk
estimates; possible impacts of the various sources of uncertainty;
and potential bias in the risk estimates. This discussion provides
a context in which the significance and limitations of the various
results can be better understood to evaluate the overall potential
health impacts of the DER site.
Site Characterization
This assessment addresses only the risks due to exposures to ground
water from a future residential well assumed to be placed at the
point of highest contamination at the facility boundary.
Analytical results from only one bedrock ground water well sampling
event were available during the preparation of this assessment.
Results from additional sampling events are required to consider
the effects of seasonal variations and analytical variability. All
analytical results are understood to exist within a range of
potential error due simply to the state of the science of
analytical chemistry. However EPA's analytical results are
consistent with acceptable standards within the U.S. Science of
Analytical Chemistry Community.
41
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Estimation of Exposure Point Concentrations
The ground water modeling utilized to estimate the exposure point
concentration is discussed in the RI. The COCs which were not
modeled were evaluated by considering a consistent
dilution/attenuation factor for the modeled parameters.
Some of the contaminants identified as COCs originally in the SCOU
were not detected in the bedrock wells and based on modeling were
not expected to move down significantly from the upper aquifer.
These contaminants were not evaluated in the risk assessment.
Evaluation of Toxicitv and Associated Constants
The estimation of potential human health impacts due to exposure to
site-related contamination utilizes various toxicity constants
derived by the EPA or approved by EPA for use in human health risk
assessments. These constants are developed based on information
derived from direct exposure (animal) or human epidemiological
studies. Intersex and interspecies extrapolations of toxicological
information require that one accept assumptions including metabo-
lism, detoxification ability, neoplastic disease initiation, DNA
repair mechanisms, etc. These extrapolations result in inherent
errors which increase the uncertainty in estimates of potential
effect. Modifying factors and uncertainty factors are inserted
which intentionally increase the risk estimates in order to ensure
*-.*-& protection of human
The interpretation of the results of the animal studies upon which
the initial toxicity evaluation is founded can be difficult.
Ambiguous or questionable results may produce a number of equally
valid, but conflicting interpretations. Guidelines for the
interpretation of laboratory (toxicological) results demand an
extremely conservative interpretation of available results. The
uncertainty which this builds into the estimates of toxicity is
acknowledged, but this conservative approach provides a level of
protection for the potentially exposed individuals.
The toxicity factors for some contaminants are not available or
have been withdrawn pending further study. To allow for evaluation
of these contaminants, they have been grouped with similar
chemicals and are evaluated using toxicity factors from
contaminants within the group. The contaminants grouped in this
assessment are ketones which include 2-butanone, 2-hexanone,
acetone, and 2-methyl-4-pentanone.
Exposure Assumptions
The exposure assumptions used in a risk assessment require
professional judgement. Often conservative default assumptions are
used. The issues regarding determination of appropriate exposure
assumptions are:
42
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The frequency and duration of exposure.
The transfer of material from environmental media to target
organs. That is, the adsorption across skin, the absorption
by the gut, the absorption by the lungs; and finally the
transfer from the blood to the target organ.
The quantity of material presented to the body. That is the
ingestion rate, the inhalation rate, the surface area exposed
and the body weight.
The default assumptions used for this risk assessment were the
Reasonable Maximum Exposure (RME) factors. The risk calculations,
therefore, represent the highest exposure that could reasonably be
expected for the given pathways.
An estimate of average exposure is calculated using average or
central tendency factors. Use of the average factors affected the
risk calculations for adult exposure in all'three pathways since
the exposure time was reduced to nine years. Exposure through
ingestion of ground water was also affected since the ingestion
rates for adults and children were reduced to 1.4 L/day and 0.7
L/day, respectively. To simplify the calculation for adult
exposure the contaminant concentration was assumed to be unchanged
during the nine year exposure period.
Use of the central tendency factors decreased the calculated risk,
but did not significantly affect the status of the COCs.
Risk Characterization
A number of assumptions were also made in estimating the outcome of
potential human exposures to site-related compounds. Carcinogens
in combination are presumed to exert their effect in an additive
fashion, whereas synergism or antagonism may be present in some
cases. Non-carcinogens are also presumed to act in an additive
fashion; however, this approach does not take into consideration
that different contaminants target different organs and organ
systems. Particularly sensitive populations or individuals may
exist, which may not become obvious until after exposure.
Assumptions regarding exposure are often very conservative.
Uncertainties entering into the analysis from the initial measure-
ment of dose and animal weight in the first lab study to the
interpretation of lab results to extrapolation between species to
the modeling of environmental dispersion, as well as other issues
have a compounding (multiplicative) effect on the final uncertainty
of the risk estimate.
43
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Effects seen at high doses (such as the doses to which laboratory
animals are often exposed) are often not seen at low dose exposures
such as those typically experienced in environmental contamination.
In order to be conservative, it is commonly assumed that cancer
incidence varies with dose in a linear or semi-linear fashion even
at extremely low dose levels, but the validity of this assumption
is currently an issue of considerable debate.
Ecological Risks
The Ecological Risk Assessment (ERA) is an integral part of the
RI/FS for the Double Eagle site. The purpose of the ERA is to
determine current and/or potential baseline impacts on ecological
receptors that are attributable to toxicological stress from the
unremediated Double Eagle site. Specific objectives within the
overall purpose include:
Identification of current/potential toxicant and habitat
stressors;
Identification of representative floral and faunal receptors
in the aquatic setting;
Assessment of endpoints;
Characterization of biotic receptors;
Assessment of relationships between toxicant stressors and
adverse affects;
- Assessment of exposure using ecological and toxicological
stressor components; and
Integration of all above-noted components for ecological risk
estimation and description of sources of uncertainty.
Toxicant Stressors
Concentrations of seven (7) organic and eight (8) inorganic COCs
were predicted for surface water in the North Canadian River
adjacent to the Double Eagle site from ground water inflow.
Further model predictions were used to estimate contaminant
concentrations in river-borne suspended sediment and in
interstitial water of vadose zone. Table 12 presents the predicted
concentrations of the COCs by media and the estimated arrival time
for those contaminants. For the purpose of this ERA, all
contaminant concentrations used were based on a worst-case
scenario. The worst-case scenario was developed by choosing the
44
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Table 12
Predicted Concentrations of Contaminants
of Concern for the North Canadian River
near the Double Eagle Site
Contaminant of Concern
Organics
Vinyl Chloride
1,2-Dichloroethane
Trichloroethane
Benzene
Chlorobeazene
1 ,4-Dichlorobeozene
bis(2-chloroethyl)ether
Inorganics
Arsenic
Barium
Beryllium
Cadmium
{ --ftpftffm^ n^
IffA
Nickel
Vanadium
Predicted Concentration by Media
Surface
Water1
(ug/L)
3.40E-02
1.40E-02
1.40E-02
9.60E-02
3.50E-02
4.00E-03
l.OOE-03
1.85E-01
1.49E+02
5.00E-03
2.00E-03
8.90E-02
2.69E+00
6.30E-02
7.81E+00
Interstitial
Water1
(ug/L)
3.40E-02
1.40E-02
1.40E-02
9.60E-02
3.50E-02
4.00E-03
l.OOE-03
I.85E-OI
1.49E+02
5.00E-03
2.00E-03
8.90E-02
2.69E+00
6.30E-02
7.81E+00
Suspended
Solids'
(ug/Kg)
0
0
0
0
0
0
0
7.56E+01
0
1.4SE02
8.00E-04
6.67E-01
7.08E+01
6.92E-02
1.09E+01
Estimated
Arrival Time1
(Years)
115
115
115
115
115
115
115
1250
115
2000
1150
115
15000
2800
900
J- Frani Chapter 4.0 of
2. Assumed equal to surface water
3. Determined by the equation:
|tion Report dated July 1993.
Cone. Suspended Solids = Cone. Surface Water x distribution coefficient (Kd)
45
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most conservative assumptions as follows: 1) The average saturated
thickness of the alluvial aquifer was assumed to be 20 feet. 2) The
low flow rate for seven (7) consecutive days for a 10-year period
reported by the USGS was used to show the maximum impact on the
river. 3) The background concentrations in the river for organics
was assumed to be zero, and for the metals was assumed to be the
same as for the alluvial aquifer.
Conceptual Ecological Model
For the purpose of this ERA, a conceptual ecological model was
developed which depicts those species of flora and fauna, typical
of the central Oklahoma area, that may experience stress from
habitat alteration or toxicant exposure. The model describes a
contiguous ecosystem which includes riverine benthic and surface
water communities of the North Canadian River. Toxicant movements
in the aquatic system may be described by the following pathways:
Uptake by vegetation from the vadose (interstitial) zone and
directly from the water column;
Uptake by water column invertebrates;
Uptake by lower food chain (omnivorous) vertebrates from
vegetation, invertebrates and incidental suspended sediment;
and,
liptake by upper food chain (piscivorus) vertebrates from lower
food chain vertebrates and invertebrates.
Generally, toxicants are translocated throughout the ecosystem by
the specified pathways where they become available to flora and
fauna through bioconcentration and bioaccumulation. In aquatic
systems, the effects of toxicants can be noticeable because of the
uptake and bioaccumulation in the food web. In the conceptual
model, phytolankton (green algae) and rooted vascular macrophytes
(milfoil) concentrate toxicants from surface water and sediment
interstitial water, respectively. Through bioconcentration,
toxicant levels will increase at the base of the food chain. For
many toxicants, subsequent depuration or biological transformation
may occur; hence, there is no further translocation through the
food web. For the purposes of this ERA, all toxicant uptake is
considered cumulative with no direct losses due to mitigative
factors.
The conceptual model also includes direct uptake (bioconcentration)
by cladocerans (water flea) from the water column. Aquatic
vegetation (in the form of detritus), invertebrates and incidental
suspended sediment are then consumed by omnivorous fish (Fathead
Minnow) which in turn are consumed by piscivorous fish (Largemouth
Bass). Contaminant uptake routes for each ecological class are
summarized in Table 13.
46
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Table 13
General Contaminant Uptake Routes
Conceptual Ecological Model
Ecological Risk Assessment
Ecological Class
Vegetation
Phytoplankton
(Green Algae)
Macrophytes
(Water Milfoil)
Invertebrates
dsdoceran
(Water Flea)
Vertebrates
ierbivorc
Fathead Minnow)
"iscivor?
Largemoutb Bass)
Bioconcentration
Surface
Water
/
/
/
/
Interstitial
Water
/
Bioaccumulation
Suspended
Solids
/
Vegetation
/
y
Invertebrate
/
/
Fish
/
47
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Risk Characterization
The potential for acute and chronic toxicity due to contaminants in
the water column were evaluated against algae, daphnids, fathead
minnows and largemouth bass. The potential for acute and chronic
toxicity due to the sediment pore water COC were evaluated against
water milfoil. Hazard quotients were calculated for fathead minnow
and largemouth bass considering their trophic levels in this
conceptualized chain of the food web which accounts for
bioconcentration and bioaccumulation. The predicted results for
total potential toxic effects and hazard to the aquatic vertebrates
as based on contaminant data and published or derived toxicity and
concentration/accumulation factors for the conceptualized model are
summarized in Tables 14 and 15. Essentially, neither the metals
nor the organics suite of contaminants posed a significant
potential for toxicity or hazard via trophic transfer in this food
chain. At the base of the food chain, heavy metals [beryllium,
lead, nickel and vanadium] appeared to: (1) present potential
chronic toxic effects to aquatic vegetation and (2) present
potential acute and chronic effects to the daphnids. No
significant ecological risk, as defined by the hazard quotient of
greater than or equal to one (1), was predicted for the minnow or
largemouth bass for any of the toxicant stressors. Likewise, the
cumulative hazard quotient for both fish was less than one (1).
The methods used in this predictive ecological assessment indicated
that ecological receptors at the base of the food web may
experience potential risk from exposure to the toxicant stressors.
Organics did not present a significant risk to any ecological
compartment while heavy metal concentrations may potentially elicit
acute and chronic toxicity. The aquatic ecosystem demonstrated
predicted impacts due to direct contact with contaminants and not
because of the influence of bioconcentration/bioaccumulation
dynamics at the lower trophic levels. A summary of potential acute
and chronic toxicity for each ecological compartment for the
contaminants of concern is provided in Table 16.
Sources of Uncertainty
The model constructed for this evaluation of ecological risk and
the semiquantitative, predictive methodologies used resulted in a
very conservative (i.e., over-predictive) approach. This approach
was selected because of the a priori decision to weight the
evaluation process qualitatively. Uncertainties and assumptions
present in this evaluation included:
48
-------
IX)
II]
*o
8
S
Ui
8
o\
ia
8
B)
i
-------
«n
3
o
g
i
O
u
en
III
u
w
oo
l-^
I
S
III
e*»
^.
v>
> -
50
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Table 16
Summary of Potential Acute and Chronic
Toricity for Each Ecological Compartment
For the Contaminants of Concern
Ecological Risk Assessment
Double Eagle Site
Ecological Compartment
Freshwater Aquatic life .
Most Sensitive Species
Aquatic Vegetation . . :. .
Green Algae
Water Milfoil
Aquatic Invertebrate .
Water Flea
Aquatic Vertebrate .
Fathead Minnow (direct)
Fathead Minnow (via food chain)
Fathead Minnow (mmiilartve hazard)
T "vemouth Bass (direct)
Largemouth Bass (via food chain)
Largemouth Bass (cumulative hazard)
Potential Toricity
Acute
' : -. :.:
-
' : .,--:-:":.'.'.--' :":
-
-
Vanadium
-
-
-
-
-
-
Chronic
Vanadium
Vanadium
Vanadium
51
-------
No corrections were made for biological modification of the
contaminants via detoxification, depuration or other such
biological processes that can mitigate against
concentration/accumulation and magnification;
No corrections were made for physicochemical factors such as
partitioning/mobilization dynamics, pH, percent organic
carbon, etc. that control presentation of toxicant dose to
organisms;
All toxicant stressors (i.e., COCs by media) were assumed to
be 100 percent bioavailable and fully retained in the
organisms;
All toxicant stressors were assumed to be transferred
completely from the abiotic compartments (water, sediment,
soil) through the food chain;
Heavy metal (cadmium, chromium, lead, nickel) toxicity
calculations were based on a water hardness of 50 mg/£ CaCO3
and total metals analyses;
Contributory risk from background concentrations of the
toxicant stressors was not removed from the overall risk
summary;
Ti.ne frame constraints for the predicted arrival of
contaminants were not considered and maximum contaminant
concentrations were used as a worst-case scenario; and,
For freshwater species, little data was available for the
toxic effects and bioconcentration of vanadium; therefore, the
criteria used were based on lowest value known toxic to
aquatic life.
VII. REMEDIAL ACTION GOALS
Based on the review of the ground water sampling data from both the
alluvial wells and the bedrock monitoring wells at the DER and the
FSR sites, EPA has determined the alluvial aquifer and the upper
portion of the Garber-Wellington (bedrock) aquifer to be a Class
III aquifer in the immediate vicinity of the sites. This
classification is due to the high TDS concentrations from past oil
and gas production activities in the area. Contaminants of
concern detected in the upper portion of the Garber-Wellington
(bedrock) aquifer were discussed previously in Section VI, and were
provided in Table 6. Concentrations of these contaminants exceed
the Maximum Concentration Limits (MCLs) and pose a 36 in 10,000
excess cancer risk to adults that may use these zones as a drinking
water supply.
52
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To be classified as a Class III aquifer (Guidelines for Ground-
Water Classification under the EPA Ground-Water Protection
Strategy, EPA, 1986) , an'aquifer must have a total dissolved solids
concentration greater than 10,000 parts per million (ppm) and/or an
aquifer yield of less than 150 gallons per day. Although the
subject aquifers yield adequate flow rates to be considered
useable, the TDS of the alluvial and upper portion of the Garber-
Wellington aquifers are much higher than 10,000 ppm. The average
and maximum concentrations of TDS in the alluvial aquifer were
2,460 ppm and 13,100 ppm, respectively; and in the upper portion of
the Garber-Wellington (bedrock) aquifer the TDS were 34,680 ppm and
110,000 ppm, respectively, for the wells installed at the DER site.
Two remedial action objectives have been developed for this site:
1) Ensure that future potential users of the lower Garber-
Wellington aquifer are not exposed to contaminants from
the site (The lower Garber-Wellington aquifer has the
potential to be used for domestic purposes);
2) Ensure that the North Canadian River is not impacted by
contaminants from the site.
Based on the results of the risk assessment and review of the
ARARs, the affected media is the upper portion of the Garber-
Wellington (bedrock) Aquifer. Transport of contaminants through
the alluvial aquifer to the river was investigated as a migration
pathway, however, the resultant. contaminant levels in the river
were below levels that warrant establishment of remedial action
goals (i.e., below risk-based levels and potential ARARs). See
Table 4. Therefore, the goals applicable to the contaminated
ground water are the Chemical-Specific ARARs identified for the
upper Garber-Wellington (bedrock) aquifer and the health based
levels for COCs necessary for protection from consumption of ground
water.
Table 17 provides a list of the goals (mcls) that the potential
remedial action technologies must achieve if the ground water is
used as a public drinking water source. These standards are
applicable to the upper Garber-Wellington aquifer at a down-
gradient well located at the site boundary and at a depth of 60
feet.
Although contaminants in the alluvial aquifer and the upper portion
of the Garber-Wellington aquifer are above MCLs for several
chemicals, restoration is not warranted since the subject portions
of the ground water is categorized as a Class III aquifer. Based
on the classification of these aquifers, no further action would be
required. However, there is no confining "aquitard" between the
upper and lower water bearing zones and there is still concern that
downward migration of contaminants to a deeper useable zone could
occur.
53
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Table 17
Remedial Action Goals
Analyte
Arsenic
Barium
Beryllium
Cadmium
Chromium
Lead
Manganese
Nickel
Thallium
Vanadium
Aldrin
Benzene
Bis(2- chtoroethvl) ether
Chiorobenzene
Ci orodane
C i oroform
D 3-4.4 -
Dknlorobenzene1r4-
L/IU UUIUVIT
>C1
DicW
oroet
broet
KUIO Iff.
ienel.1 -
Heneds- \2
>Sc iHoroethene tens - 1,2
Endosutfan
leplac uw
f
Heptachlor Epoxide
?eoi
- A
- H
- B
- 4
les
ceton
exaru
utono
-Me
Methytene
e
sne2-
ne 2 - (Methyl Ethyl Ketone)
ithyl - 2 - Pentanone
Chloride
Phenol
Toluene
Trichbroethene
Vinyl
Chloride
Xvlene
Goal
(mq/I)
4.7E- 6
2E+0
1.1E-1
N/A
N/A
N/A
N/A
7.8E-3
N/A
2E-3
1.3E-4
N/A
5.0E-7
5E-3
7.8E-5
2.1 E-6
3.1 E- 3
1.8 E-6
2.8E-5
3.0E-6
3.5 r-4
5E-3
2.5E-5
1.9E-8
7E-2
3.15E-2
7.85-5
1.9E-6
9.4E-7
1.8E-1
3.1 E- 2
9.4E-1
7.8E-2
1.1 E-3
9.4 E-1
6.3E-2
5E-3
3.4E-4
4.SE-6
5.6E-2
54
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Because the alluvial and upper portion of the Garber-Wellington
aquifers are Class III aquifers, these goals are not applicable.
VIII. DESCRIPTION OF ALTERNATIVES
A Feasibility Study was conducted to develop and evaluate remedial
alternatives for the DER site for the GOU. Remedial alternatives
were assembled from applicable remedial technology process options
and were initially evaluated for effectiveness, implementability
and cost based on engineering judgement. The alternatives selected
for detailed analysis were evaluated and compared to the nine
criteria required by the NCP. As a part of the evaluation, the NCP
requires that a no-action alternative be considered at every site.
The no-action alternative serves as a point of comparison for the
other alternatives.
Remedial Action Alternatives
Four remedial alternatives were initially considered for ground
water remedial action in the Feasibility Study for the Double Eagle
site. These alternatives are: 1) No Action, 2) Limited Action, 3)
Precipitation of Metals and Activated Carbon Treatment of Organic
Contaminants, and 4) Precipitation of Metals and Biological
Treatment of Organics. During the initial development of these
alternatives, Alternative 4 was considered inappropriate and was
eliminated. The cost of Alternative 4 was significantly higher
than Alternative 3, yet it did not provide an additional level of
risk reduction. The following alternatives to address the ground
water contamination at the DER site were evaluated:
1. No Action
The "No Action" alternative is required for consideration by the
National Contingency Plan and represents a continuation of the
current situation. This alternative establishes a baseline for
comparison with the other alternatives. This alternative does not
provide a means of monitoring of the ground water to determine if
contaminant releases are continuing. Under the "No Action"
alternative, no activities to address the risks posed by the
contaminated ground water at the site would be implemented.
Inclusion of this alternative is required by the Superfund law and
is the basis for evaluating other alternatives.
There are no costs associated with Alternative 1.
2. Limited Action
Major Components of the Limited Action Alternative; Components of
this alternative include: institutional controls to control'
exposure to contaminated ground water, and continued ground water
monitoring to assess changes in the potential for exposure.
Installation of warning signs is included in the alternative to
require notification prior to drilling in the area. A deed notice
55
-------
would be filed to notify future land owners of the hazards
associated with the contaminated ground water in the area of the
site. A deed restriction was considered, but was not pursued since
the State of Oklahoma does not have the authority to place a
restriction in the deed.
This alternative includes the installation of additional ground
water monitoring wells and establishment of a routine monitoring
and maintenance program for ground water sampling and modeling to
evaluate contaminant level reductions following removal of the
contaminant source. The new wells will be installed in a deeper
zone of the Garber-Wellington than the wells presently installed at
the site, at an approximate depth of at least 100 feet below ground
surface. The deepest wells present at the DER site are at about 60
feet deep. The installation of additional deeper monitoring wells
further down-gradient will allow the EPA to ensure that
contaminants do not migrate deeper, or to any receptor point
offsite, and determine if an offsite source of contamination
exists. Also, these deeper wells will allow the EPA to determine
if the ground water beneath 60 feet is useable, or has been
previously contaminated by past oil and gas production activities
(contains high TDS).
Modeling conducted during the RI indicates that MCLs will be
achieved through attenuation in 60 to 150 years. An aspect of this
alternative is to allow natural attenuation to reduce these
contaminant levels over time. Natural attenuation relies on the
ground water's natural ability to lower the contaminant
concentrations over time through physical, chemical, and biological
processes. Routine inspections would also be included in a formal
monitoring and maintenance plan to ensure that public use of the
upper zone (less than 60 feet in depth) of the Garber-Wellington
aquifer does not occur prior to attainment of the remedial action
objectives.
The "Limited Action" alternative would also include monitoring of
the existing monitoring wells. The ground water monitoring will be
conducted to determine if current conditions improve through time,
remain constant, or worsen. The ground water monitoring well
sampling will be conducted on a quarterly schedule for the first
two years and then semi-annually until the first "five-year
review". After the five-year review, the EPA will evaluate all
data and determine if the sampling should be conducted annually or
less frequently. The site would also be re-evaluated every five
years ("five-year review"), to determine if further actions need to
be taken with regard to the ground water. The five-year review
will analyze the data obtained and include computer modeling to
determine if contaminant level reductions are being achieved as
expected, once the surface source of contamination is stabilized.
If the ground water monitoring indicates that detectable
concentrations of site contaminants are found below the affected
upper portion of the Garber-Wellington aquifer, or if the
56
-------
contaminated portions of the ground water show an increase of 30
percent for any contaminant in any of the alluvial or upper Garber-
Wellington monitoring wells; the need for contingency measures
(including active treatment) will be evaluated. Contingency
measures can include one or all of the following elements:
Installation of additional monitoring wells to determine
if the contamination is increasing in concentration or
migrating.
Increasing the frequency of sampling to assure that a
complete exposure pathway does not develop.
Construction of a containment measure such as a slurry
wall.
Implementation of a remedial action plan for extraction,
treatment, and disposal of contaminated ground water.
Although this alternative does not meet the Superfund preference
for treatment of contaminants, EPA's evaluation of the site
specific data indicates that active treatment of the ground water
contamination is not warranted at this time. Active treatment is
not warranted because l) the contaminated ground water aquifers
are Class III aquifers, and 2) the ground water modeling data
showed that by the time the ground water contaminants reach the
North Canadian River, the concentrations would be sufficiently low
and will not adversely impact the river.
General components: The estimated time to implement this remedy is
12 months. The estimated cost associated with implementing
Alternative 2 are: Capital Costs: $158,000; Annual Operation and
Maintenance Costs: $74,880; Total Present Net Worth: $1,463,056.
\
3. Inorganic Precipitation and Activated Carbon Treatment for
Organic Contaminants
Major Components of the Remedial Alternative. The major features
of alternative 3 consists of the following key elements: 1)
installation of a ground water recovery system, 2) construction of
an on site ground water treatment and discharge system, 3)
discharge of the treated ground water either to the North Canadian
River, to a Publically Owned Treatment Works (POTW) , or reinjection
to the alluvial aquifer, and 4) implementation of an operation,
monitoring, and maintenance program.
Components of the Recovery System: The components of the ground
water recovery system include installation of additional ground
water recovery wells in the area of the ground water plume with
sufficient overlap of the radii of influence to recover the
contaminant plume. A system of pipes from the recovery wells would
be used to convey the recovered ground water from each well to an
57
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equalization tank for subsequent treatment.
Implementation of the proposed ground water recovery system will
contain the contaminant plume and reduce the contaminant levels
more quickly than natural attenuation. Using the ground water
recovery system described above, a period of approximately 25 years
would be required for contaminant levels to reach the remedial
action goals. Additionally, the contaminant plume will
theoretically be contained thereby mitigating further offsite
migration of the plume.
Components of the Treatment System: The chemical treatment system
that would be employed under this alternative consists of chemical
and polymer addition followed by filtration to remove flocculated
inorganic constituents. Chemical treatment is performed using a
reagent, such as lime, to increase the pH and thereby reduce the
solubility of the inorganic constituents. The decrease in
solubility will cause the inorganic constituents to form metal
hydroxides. The effectiveness of the removal of flocculated solids
can be enhanced through the use of a polymer, based flocculent.
Filtration can then be used to remove the flocculated solids from
the treated water.
After the filtration unit, the water would be treated through an
activated carbon unit to remove organic COCs followed by direct
discharge to the River or discharge to a POTW. Treatment of
wastewaters using activated carbon adsorption typically occurs in
packed-bed columns piped in series. The activated carbon adsorbs
the organic based hazardous constituents by surface attraction in
which organic molecules are attracted to the internal pores of the
carbon granules. Very high organic removal efficiencies can be
achieved using this process.
Components of the Discharge System: The decision to discharge
directly to the river or to a POTW is considered a design aspect.
The decision would be based on consideration of waste treatability,
local standards, and a detailed cost analysis. This alternative
would have to meet all applicable (Clean Water Act) statutory
requirements contained in a National Pollutant Discharge
Elimination System (NPDES) permit, and would require an NPDES
permit for an off-site discharge directly to the river.
Components of the operation and Maintenance Program: Since the
ground water recovery and treatment system will require
approximately 1 year to install and 25 years to complete
remediation, it will be necessary to establish site access controls
and an operation, monitoring, and maintenance program similar to
the program described under the Limited Action Alternative
(Alternative 2).
In addition to the elements included in the Limited Action
monitoring and maintenance program (site warning signs, deed
notice, sampling and analysis program, etc.), operation and
58
-------
maintenance of the recovery and treatment system will be required
under this alternative. Operation and maintenance of the recovery
and treatment system includes equipment replacement, maintaining
treatment reagent supplies, operation of the treatment system, and
disposal of residues (inorganic precipitate residues, spent carbon,
etc.) from the treatment of contaminated ground water. The
treatment residues may be characterized as a RCRA waste due to the
characteristic of toxicity. Disposal of the residues would be done
based on the results of a leachability test conducted on the
residue. Residues that fail the Toxicity Characteristics Leaching
Procedure (TCLP) test would require further treatment to remove the
characteristic prior to disposal. If this alternative were
implemented, the transportation of the treatment residues would
have to meet all applicable requirements of the U.S. Department of
Transportation; and the disposal of these residues would be
performed in accordance with all requirements contained in 40 CFR
Part 268 - Land Disposal Restrictions.
General Components: The estimated time to implement this remedy is
12 months, and approximately 25 to 40 years to complete (to meet
the Remedial Action Goals). The estimated costs associated with
implementing Alternative 3 are: Total Capital Costs: $775,000;
Annual Operation and Maintenance Cost: $354,200; and Total Present
Net Worth: $5,996,331.
K. SUMMARY OF THE COMPARATIVE ANALYSIS OF ALTERNATIVES
The EPA uses nine criteria to evaluate alternatives for addressing
a Superfund site. These nine criteria are categorized into three
groups: threshold, primary balancing, and modifying. The threshold
criteria must be met in order for an alternative to be eligible for
selection. The primary balancing criteria are used to weigh major
tradeoffs among alternatives. The modifying criteria are taken
into account after state and public comment is received on the
Proposed Plan of Action.
Nine Criteria
The nine criteria used in evaluating all of the alternatives are as
follows:
a) Threshold Criteria
Overall Protection of Hwiaa Health and the Environment addresses
the way in which an alternative would reduce, eliminate, or control
the risks posed by the site to human health and the environment.
The methods used to achieve an adequate level of protection vary
but may include treatment and engineering controls. Total
elimination of risk is often impossible to achieve. However, a
remedy must minimize risks to assure that human health and the
environment are protected.
59
-------
Compliance with ARARs. or "applicable or relevant and appropriate
requirements", assures that an alternative will meet all related
federal, state, and local requirements.
b) Primary Balancing Criteria
Long-term Effectiveness and Permanence addresses the ability of an
alternative to reliably provide long-term protection for human
health and the environment after the remediation goals have been
accompl ished.
Treatment assesses how effectively an alternative will address the
contamination at a site. Factors considered include the nature of
the treatment process; the amount of hazardous materials that will
be destroyed by the treatment process; how effectively the process
reduces the toxicity, mobility, or volume of waste; and the type
and quantity of contamination that will remain after treatment.
Short-term Effectiveness addresses the time it takes for remedy
implementation. A potential remedy is evaluated for the length of
time required for implementation and the potential impact on human
health and the environment during implementation.
Implementability addresses the ease with which an alternative can
be accomplished. Factors such as availability or materials and
services are considered.
Cost (including capital costs and projected long-term operation and
maintenance costs) is considered and compared to the benefit that
will result from implementing the alternative.
c) Modifying Criteria
State Acceptance allows the state to review the proposed plan and
offer comments to the EPA. A state may agree with, oppose, or have
no comment on the proposed remedy.
Community Acceptance allows for a public comment period for
interested persons or organizations to comment on the proposed
remedy. EPA considers these comments in making its final remedy
selection. The comments are addressed in the responsiveness
summary which is a part of this ROD.
Comparative Analysis
This comparative analysis presents an analysis of each alternative
in relation to each other using the nine criteria. The analysis is
used to identify the relative advantages of one alternative versus
another alternative.
60
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Overall Protection of Human Health and the Environment
Alternative 1 does not achieve the remedial action objectives and
does not provide protection to human health and the environment.
Although contaminant concentrations should decrease over time upon
removal of the source material, Alternative 1 does not provide for
monitoring of the contaminant plume.
Alternative 2 provides adequate protection of human health and the
environment. Because the alluvial and upper bedrock aquifers are
Class III aquifers, they will not likely be used as water supplies.
Ground water monitoring will alert EPA to any potential for
movement of site contaminants to a potential drinking water
aquifer. This alternative will also provide information about
changes in contaminant concentrations upon removal of the surface
source of contamination. Upon removal of the surface source
material, contaminant concentrations would be expected to decrease
due to natural attenuation. If contaminants migrate below the
bedrock portion of the aquifer or towards the river, or if the
contaminant levels are not reduced as expected; contingency
measures will be taken to ensure protection of human health and the
environment. Federal drinking water standards would be attained in
approximately 60 - 150 years.
Alternative 3 would provide the greatest protection of human health
and the environment from exposure to contaminants from the site;
however, active remediation is not warranted at this time, since
removal of site contaminants would not restore the alluvial or
upper bedrock aquifers to be usable aquifers due to the presence of
high TDS.
comliance with
The individual discussions of compliance with ARARs within the
Feasibility Study indicated that each alternative will meet their
appropriate location-specific and action-specific ARARs. Action-
specific ARARs are listed in Table 18. Implementation of
Alternative 3 is expected to achieve the remedial action goals
listed in Table 17 in approximately 25 years. Alternatives 2 and
3 provide the information necessary to determine achievement of the
ground water ARARs. Alternative 1 would not provide sufficient
information to assess lateral or vertical contaminant migration.
Thus, EPA would not be able to evaluate potentially unacceptable
risks from exposure to site contaminants either in the North
Canadian River or future use of the lower Garber-Wellington aquifer
as a water supply.
Longterm Effectiveness and Permanence
Alternative 3 provides the greatest degree of long-term
effectiveness and permanence because the contaminant levels are
reduced more quickly than Alternatives 1 or 2. Treatment of the
contaminants present in the recovered ground water also provides a
61
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62
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greater degree of long-term effectiveness and permanence because
the contaminants are either degraded, absorbed, or altered to a
more stable form. Treatment residues associated with the
Alternative 3 are manageable and will be disposed in a manner that
minimizes the long-term potential for cross media impacts.
However, the success of Alternative 3 at removing the contamination
from the alluvial and the upper portion of the Garber-Wellington
aquifers is highly questionable since A) there is a possibility of
an off site source of contamination, B) the subject water bearing
zones are Class III aquifers, and C) the success of remediation of
sites with DNAPL contamination is suspect. Consequently, although
Alternative 3 may reduce contaminant levels in the short term, it
may not be significantly more effective in the long term for the
protection of human health and the environment. Contaminants from
other sources and dissolved solids from past oil production
activities would continue to impose a risk to human health.
Therefore, Alternative 3 may not achieve a significant reduction in
overall risk.
Alternative 2 can effectively monitor the contaminant
concentrations in the alluvial, and upper and lower Garber-
Wellington aquifers. The reduction in concentrations of site
contaminants, upon removal of the surface contamination, is
expected to be permanent. With the source stabilized, minimal site
contaminants will leach into the ground water. The reduction in
leachate contaminating the ground water beneath the site is
considered permanent. Therefore, the reduction in. risk from site
contaminants will also be permanent.
Alternatives 1 and 2 do not provide a reduction in toxicity,
mobility, or volume through treatment. Alternative 3 satisfies the
preference for treatment as a principal element in the alternative,
uses treatment to reduce contaminant levels in recovered ground
water, and reduces the potential for transfer of the contaminants
from the alluvial and upper bedrock aquifers to the lower Garber-
Wellington. However, the overall reduction attributable to
Alternative 3 is questionable, because of the presence of another
source not related to the DER site. The precipitation of inorganic
contaminants, and the carbon absorption under Alternative 3 is
considered an irreversible process, and provides a permanent
reduction in toxicity and mobility. However, the overall reduction
in toxicity may not be significant due to other potential sources
of organic contamination in the area.
Short-term Effectiveness
The short-term risk associated with Alternative 1 is a continuation
of the risk currently associated with the site. In the short-term,
63
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the risk from contaminated ground water is minimal since use of the
ground water as a drinking water source is considered a future use
exposure scenario. Over the short term, implementation of
Alternatives 2 and 3 would not significantly increase the risk to
the community or site workers. The additional risk associated with
construction of a monitoring system or a recovery system
(Alternative 3) can be managed by application of engineering and
short-term access controls.
Transportation of treatment residues associated with Alternative 3
can potentially cause exposure to the general public and the
environment should a mishap occur during transportation. However,
transportation of wastewater treatment residues is a common and
well managed practice in the industry and is not expected to cause
a significant increase in the short-term risk. The transportation
of these residues would have to be conducted in compliance with all
applicable requirements of the U.S. Department of Transportation.
Implementability
Alternative 1 is the easiest to implement. Alternative 2 involves
installation of a ground water monitoring system which does not
require significant construction activity. Alternative 3 requires
the same elements of Alternative 2 with the addition of a recovery
and treatment system. If the treated ground water were discharged
directly to the river, an NPDES permit would be required. This
could delay implementation. The construction of a ground water
monitoring and/or recovery and treatment system with operation,
monitoring, maintenance, and residual material disposal activities
are standard practices in the industry and are readily available.
Adequately trained and experienced personnel are also readily
available for the implementation of the system.
No free phase contamination was encountered during the drilling
operations at the DER site, but some of the chemicals detected in
the ground water beneath the DER site such as dichloroethane,
trichloroethane and dichlorobenzene are associated with DNAPL
contamination. Past experience with ground water recovery systems
indicates a high degree of difficulty in restoring ground water at
sites that contain chemicals associated with DNAPL contamination.
Therefore, Alternative 3 may be implementable, but based on
historical data, the efficiency of remediating this type of
contamination is questionable.
Coat
Alternative 2 at a cost of $1.5 million, provides the same amount
of information as Alternative 3 (approximate cost $6 million) with
respect to characterization of contaminant level reductions.
Alternative 2 does not achieve reductions in contaminant levels in
the same time frame as the recovery and treatment of the
contaminant plume under Alternative 3. Alternative 2 can be
64
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implemented for a significantly reduced cost and provide the
flexibility to continue assessment of ground water contaminant
levels.
State Acceptance
The State of Oklahoma believes that ground water monitoring is the
appropriate alternative for this site. Attachment C is a letter
from the ODEQ to the EPA stating that the State of Oklahoma concurs
with the Limited Action alternative.
Community Acceptance
Comments received during the public comment period indicate that
much of the community questioned whether the Proposed Remedy -
Limited Action, was protective of human health and the environment.
One commenter provided written opposition to the proposed remedy,
and suggested the use of a specific technology termed
"bioremediation and metals extraction". All comments received
during the public comment period, and EPA responses are in the
attached Responsiveness Summary (Attachment B).
X. THE SELECTED REMEDY
Based upon consideration of the requirements of CERCLA, the
detailed analysis of the alternatives using the nine criteria, and
public comments, the EPA has determined that Alternative 2 -
Limited Action is the most appropriate alternative for remediating
the ground water beneath the Double Eagle site. The major
components of this remedy include:
Installation of warning signs to require notification prior to
drilling in the area.
A deed notice filed to notify future land owners of the
hazards associated with the contaminated ground water in the
area of the site.
Installation of additional deeper monitoring wells further
down-gradient to ensure that contaminants do not migrate
deeper, or to a receptor point off site, and to determine if an
offsite source of contamination exists.
Establishment of a routine (quarterly sampling for the first
two years, then semi-annually for the following three years)
monitoring and maintenance program for ground water sampling
and modeling to evaluate contaminant level reductions
following removal of the contaminant source.
Routine inspections to ensure that public use of the upper
zone of the Garber-Wellington Aquifer does not occur prior to
65
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attainment of the remedial action objectives.
Five-Year review of the site to determine if further actions
need to be taken with regard to the ground water. As part of
the 5-year review, data analysis and ground water modeling is
included to assess the adequacy of the monitoring and
maintenance plan.
Contingency measures (which include active treatment) that can
be implemented if the ground water monitoring indicates an
increase in contaminant concentrations (either vertically or
horizontally). The contingency measures are described below.
EPA believes that the Limited Action alternative is the most
appropriate alternative for the following reasons:
1) The ground water in the vicinity of the site is not used as a
water supply;
2) The extremely high concentration of Total Dissolved Solids make
the ground water undesirable as a water supply source;
3) Efforts to remove site-related contaminants in the ground water
would not improve its over all quality, and;
4) The North Canadian River is not threatened at the present time,
nor will it be threatened in the future by site contaminants.
The primary threat posed by the contaminated ground water is the
possibility of migration of the contamination downward into a
useable drinking water zone, or lateral migration into a surface
water body which is the North Canadian river. EPA considers
Alternative 2 the most prudent remedy in light of the fact that the
upper portion of the Garber Wellington aquifer and the alluvial
aquifer are considered Class III aquifers. Also, the data obtained
during the investigation stage of the project suggests the
possibility of an offsite, upgradient source of contamination.
Since the Total Dissolved Solids in the ground water are so high,
and there is a possibility of an offsite source of contamination,
even if a pump and treat alternative (Alternative 3) was
implemented at a much higher cost, the ground water would still
remain non-useable.
The goal of the remedial action is to prevent migration of
contaminants from the shallow aquifer to the deeper aquifer, thus
maintaining the deeper aquifer for its beneficial use. Based on
information obtained during the remedial investigation and analysis
of all remedial alternatives, EPA believes that the preferred
remedy is the most appropriate alternative to achieve this goal.
If monitoring does not indicate a reduction in the concentration of
ground water contamination or if the ground water plumes continue
to expand based on sampling of the specified monitoring points, the
contingency measures described below may be implemented.
66
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The preferred remedy is protective of human health and the
environment, complies with Federal and State requirements that are
legally applicable or relevant and appropriate to the remedial
action, and is cost-effective. Because treatment of the
contaminated ground water was not found to be warranted at this
time, this remedy does not satisfy the statutory preference for
treatment as a principal element of the remedy.
Because the preferred alternative" will result in hazardous
substances remaining on-site above health based levels (in the
shallow ground water, including the alluvial and upper portion of
the Garber-Wellington aquifers), a review will be conducted within
five years after commencement of remedial action to ensure that the
remedy continues to provide adequate protection of human health and
the environment. All work to be performed at the site will be
conducted pursuant to 29 CFR Part 1910 (Worker health and Safety
Plan).
Contingency measures;
The preferred alternative provides for natural attenuation to
reduce contamination levels in the alluvial aquifer and the upper
portion of the Garber-Wellington aquifer, and to prevent migration
of contaminants from the alluvial aquifer and the upper portion of
the Garber-Wellington aquifer to the deeper portion of the Garber-
Wellington aquifer. The alternative also provides for ongoing
monitoring of all existing site wells to determine 1) whether
natural attenuation is working to reduce the contamination level in
the ground water aquifers, and 2) whether the contamination has
migrated vertically or horizontally.
If during the monitoring, detectable concentrations of site
contaminants are found below the affected upper portion of the
Garber-Wellington aquifer, or if the contaminated portions of the
ground water show an increase of 30 percent for any contaminant in
any of the alluvial or upper Garber-Wellington monitoring wells;
the well which showed the increase in concentration will be
resampled immediately. If the second analysis confirms that there
has been a 30 percent increase in contaminant concentration, or
resampling of the deeper Garber-Wellington aquifer confirms
detection, EPA will evaluate 1) the impacts of any offsite sources
of contamination, and 2) the need for additional remedial action to
address site related contaminants. Based on these evaluations, EPA
may require implementation of any or all of the following actions:
Installation of additional monitoring wells to determine
if the contamination is increasing in concentration or
migrating.
Increasing the frequency of sampling to assure that a
complete exposure pathway does not develop.
67
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Construction of a containment measure such as a slurry
wall.
Implementation of a remedial action plan for extraction,
treatment, and disposal of contaminated ground water.
The decision to implement contingency measures may be outlined in
an Explanation of Significant Difference, that will be made
available to the public in the Administrative Record.
Alternative 2 will provide protection to human health and the
environment by allowing the EPA to monitor the ground water to
confirm contaminant level reductions (as predicted), and ensure
that contaminant migration does not reach a receptor point.
Alternative 1 is not considered appropriate since the "No-Action"
alternative will not allow monitoring of the ground water to
provide protection to human health and the environment.
Since the data suggests the possibility of an offsite source of
contamination, and the industrialized nature of the adjacent
properties, an investigation is currently being conducted by other
programs within both the State and the EPA which have authority to
address a health threat posed by petroleum products from active
facilities that are exempt under Superfund. A Resource
Conservation and Recovery Act (RCRA) inspection of active
facilities in the area is underway. If it is discovered that an
unauthorized release has occurred, appropriate action will be
taken.
XL THE STATUTORY DETERMINATIONS
EPA's primary responsibility at Superfund sites is to select
remedial actions that are protective of human health and the
environnent. Section 121 of CERCLA also requires that the selected
remedial action for the site comply with applicable or relevant and
appropriate environmental standards established under Federal and
State environmental laws, unless a waiver is granted. The selected
remedy must also be cost-effective and utilize treatment or
resource recovery technologies to the maximum extent practicable.
The statute also contains a preference for remedies that include
treatment as a principal element. The following sections discuss
how the selected remedy for contaminated ground water at the DER
site meets the statutory requirements.
Protection of Human Health and the Environment
The future use scenario is the only complete pathway for human
exposure to the contaminant plume. Exposure under this scenario
would be completed if a 60-foot deep public drinking water well was
installed at the site boundary and within the area of the
contaminant plume. Alternative 2 provides control of this exposure
route by reducing the likelihood that a drinking water well will be
68
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installed prior to attainment of the remedial action objectives.
Based on the worst-case natural attenuation modeling results, a
period of 60 to 150 years is expected before contaminant levels
will attenuate to within the remedial action objectives. However,
based on levels of TDS at the exposure point, it is unlikely that
the upper portion of the bedrock aquifer will be used as a public
drinking water source.
The monitoring and maintenance program will be used to demonstrate
attenuation of contaminant levels and provide sufficient
information to conduct regular ground water modeling. Based on the
results of routine monitoring and ground water modeling results,
the site controls and monitoring and maintenance plan would be
revised as necessary.
A minimum degree of cross-media impacts or short-term risks are
associated with this alternative since additional exposure to the
contaminated media is minimized. Therefore, to the extent that the
upper portion of the bedrock aquifer is not used as a public
drinking water source, this alternative provides a high degree of
protection to human health and the environment. Through natural
attenuation, contaminant levels are expected to be within the
remedial action objectives at a future time. If the ground water
is used as a public drinking water source, this alternative does
not eliminate the risk to human health and the environment during
the period that natural attenuation of contaminant levels occurs
and contaminant levels exceed the remedial action objectives.
Compliance with ASARs
The ground water at the exposure point is not currently used as a
public drinking water source due to the high total dissolved solids
from past oil production activities. Continued monitoring will
monitor the attenuation of contaminant levels to MCLs. Since
modeling results indicate that the contaminant plume will not
impact the river, the potential ARARs associated with surface water
standards will be achieved. Additional action-specific ARARs
associated with implementation of this alternative include
standards for installation of additional wells and disposal of
miscellaneous wastes associated with the monitoring program such as
sampling equipment and produced water. Those wastes will be
properly disposed of in an appropriate facility in compliance with
the EPA's offsite disposal policy. Compliance with the action-
specific ARARs is not expected to present a significant obstacle to
implementation of this remedial alterative. Action-specific ARARs
are listed in Table 18.
Cost-Effectiveness
The selected remedy is considered cost effective since it is much
less expensive than Alternative 3, yet provides adequate protection
to human health and the environment. The "No-Action" alternative
69
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is not considered acceptable since it provides no protection to
human health and the environment.
Utilization of Permanent Solutions and Treatment or Resource Recovery Technologies to the
Maximum Extent Practicable
Alternative 2 is not considered permanent because this alternative
will not actively remove the contamination within the aquifer and
restore the ground water to MCLs. Alternative 2 does not use a
treatment technology or a resource recovery technology as an aspect
of this remedy. However, it is considered the most practical
solution since this alternative will allow continued monitoring, to
confirm whether an off site source of contamination exists, and that
the classification of the aquifer as a Class III zone remains
appropriate.
Alternative 2 is considered permanent in the sense that the five-
year review will allow ground water sampling and analysis, and
modeling to confirm contaminant level reductions; and if a future
threat to human health and the environment becomes apparent,
Alternative 3 or a comparable pump and treat operation can be
implemented at that time.
Preference for Treatment as a Principal Element
Treatment is not a principal element of alternative 2; however, it
is considered the best alternative considering the specific
conditions and circumstances at the site.
XII. DOCUMENTATION OF SIGNIFICANT CHANGES;
The overall remedy selected in this ROD is not significantly
different from the alternative proposed for public comment.
However, a contingency plan for future evaluation of active
remediation, should the lower Garber-Wellington aquifer be impacted
by contaminants from the DER site, has been included.
70
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ADMINISTRATIVE RECORD INDEX
FINAL
SITE NAME: DOUBLE EAGLE REFINERY SITE
SITE NUMBER: OKD 980696470
INDEX DATE: 03/03/94
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*****************************************************************************
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*****************************************************************************
* I. CHRONOLOGICAL LISTING *
t**
Ir**
*****************************************************************************
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ADMINISTRATIVE RECORD INDEX
FINAL
SITE NAME:
SITE NUMBER:
DOUBLE EAGLE REFINERY SITE
OKD 980696470
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
005598 - 005625
10/27/92
028
Staff Consultants
Fluor Daniel, Inc.
U.S. EPA Region 6 Site Files
Final Project Work Plan
"Final Project Work Plan for the Groundwater Operable Unit
Remedial Investigation/Feasibility Study (RI/FS) - Volume 1'
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
005626 - 005851
01/01/93
226
Staff Consultants
Fluor Daniel, Inc.
U.S. EPA Region 6 Site Files
Final Work Plan
"Final RI/FS Work Plan for Groundwater Operable Unit"
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
005852 - 005867
01/12/93
016
Robert K. Franke, ARCS Project Manager and Mark L. deLorimier,
P.E., ARCS Program Manager
Fluor Daniel, Inc.
Philip Allen, Remedial Project Manager, U.S. EPA Region 6
Correspondence and Attachment
"Responses to Region 6's and Oklahoma State Department of
Health's comments regarding the Final RI/FS Work Plan"
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
005868 - 005868
02/18/93
001
EPA Staff
U.S. EPA Region 6
U.S. EPA Region 6 Site Files
Open House Invitation
"Invitation to the public to attend the 02/18/93 open house to
learn more about Superfund activities at the Double
Eagle/Fourth Street Superfund Sites"
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ADMINISTRATIVE RECORD INDEX
FINAL
SITE NAME:
SITE NOMBER:
DOUBLE EAGLE REFINERY SITE
OKD 980696470
DOCUMENT NOMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
005869 - 005879
12/24/92
Oil
Robert K. Franke, ARCS Project Manager and Mark L. deLorimier,
P.E., ARCS Program Manager
Fluor Daniel, Inc.
Philip H. Allen, Remedial Project Manager (RPM), U.S. EPA
Region 6
Correspondence and Attachments
"Bedrock Monitoring Well Data - Double Eagle and Fourth Street
Refinery Sites"
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
005880 - 005880
02/03/93
001
Philip H. Allen, P.E., RPM
U.S. EPA Region 6
Robert K. Franke, ARCS Project Manager, Fluor Daniel, Inc.
Correspondence
"Modelling Assumptions for the Risk Assessment for the Ground
Water Operable Unit at the Double Eagle and Fourth Street
Refinery Sites"
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
005881 - 005886
02/23/93
006
Philip H. Allen, P.E., RPM
U.S. EPA Region 6
Robert K. Franke, ARCS Project Manager, Fluor Daniel, Inc.
Correspondence and Attachments
"Guidance for the Risk Assessment and the Remedial
Investigation/Feasibility Study for the Ground Water Operable
Unit - Double Eagle and Fourth Street Refinery Sites"
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
005887 - 005890
02/26/93
004
Robert K. Franke, ARCS Project Manager and Mark L. deLorimier,
P. E., ARCS Program Manager
Fluor Daniel, Inc.
Philip H. Allen, RPM, U.S. EPA Region 6
Correspondence and Attachments
"Updated Project Schedule - Double Eagle and Fourth Street
Refinery Sites"
-------
ADMINISTRATIVE RECORD INDEX
FINAL
SITE NAME:
SITE NUMBER:
DOUBLE EAGLE REFINERY SITE
OKD 980696470
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
005891 - 006450
07/27/93
560
Staff Consultants
Flour Daniels, Inc.
U.S. EPA Region 6 Site Files
Final Remedial Investigation Report
"Ground Water Operable Unit Final Remedial Investigation
Report - Double Eagle Superfund Site" (Includes Appendixes
A-K)
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
006451 - 006917
07/27/93
467
Staff Consultants
Fluor Daniel, Inc.
U.S. EPA Region 6 Site Files
Final Feasibility Study Report
"Ground Water Operable Unit Final Feasibility Study Report
Double Eagle Superfund Site" (Included Appendixes A-E)
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:'
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
006918 - 006932
08/05/93
015
EPA Staff
U.S. EPA Region 6
General Public
Proposed Plan of Action
"EPA Announces Proposed Plan of Action"
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
006933 - 006933
03/31/89
Office of Emergency and Remedial Response
U.S. EPA - Washington, D.C.
U.S. EPA Region 6 Site Files
Guidance Document
"Risk Assessment Guidance for Superfund: Volume 2 -
Environmental Evaluation Manual (Interim Final)".
EPA/540/1-89/001, March 1989. (See "For Your Information")
-------
ADMINISTRATIVE RECORD INDEX
FINAL
SITE NAME:
SITE NUMBER:
DOUBLE EAGLE REFINERY SITE
OKD 980696470
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
006934 - 006934
12/31/89
Office of Emergency and Remedial Response
U.S. EPA - Washington, D.C.
U.S. EPA Region 6 Site Files
Guidance Document
"Risk Assessment Guidance for Superfund: Volume 1 - Human
Health Evaluation Manual (Part A) (Interim Final)".
EPA/540/1-89/002, December 1989. (See "For Your Information")
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
006935 - 006935
12/31/91
Office of Emergency and Remedial Response
U.S. EPA - Washington, D.C.
U.S. EPA Region 6 Site Files
Guidance Document
"Risk Assessment Guidance for Superfund: Volume 1-Human Health
Evaluation Manual (P^rt B, Development Risk-based Preliminary
Remediation Goals (Interim)". Publication 9285.7-01B, Dec.
1991. (See "For Your Information")
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
006936 - 006936
12/31/91
Office of Emergency and Remedial Response
U.S. EPA - Washington, D.C.
U.S. EPA Region 6 Site Files
Guidance Document
"Risk Assessment Guidance for Superfund: Volume 1 - Human
Health Evaluation Manual (Part C, Risk Evaluation of Remedial
Alternatives) (Interim)". Publication 9285.7-01C, December
1991. (See "For Your Information")
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
006937 - 006967
02/28/92
035
Office of Emergency and Remedial Response
U.S. EPA Headquarters - Washington, D.C.
U.S. EPA Region 6 Site Files
Summary Report - Volume 1
"Evaluation of Ground-Water Extraction Remedies: Phase II1
-------
ADMINISTRATIVE RECORD INDEX
FINAL
SITE NAME:
SITE NUMBER:
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
DOUBLE EAGLE REFINERY SITE
OKD 980696470
006968 - 007417
02/28/92
450
Office of Emergency and Remedial Response
U.S. EPA Headquarters, Washington, D.C.
U.S. EPA Region 6 Site Files
Case Studies and Updates - Volume 2
"Evaluation of Ground-Water Extraction Remedies: Phase II'
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
TITLE:
007418 - 007547
06/30/92
130
Staff Consultants
Fluor Daniel, Inc.
U.S. EPA Region 6 Site Files
Draft Remedial Investigation
"Draft Remedial T-vnstigation Phase III Report"
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
007548 - 007589
03/29/93
042
Unspecified
U.S. EPA Region 9
U.S. EPA Region 6 Site Files
Compendium of Guidance Documents Index
"Compendium of CERCLA Response Selection Guidance Documents
Index"
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
007590 - 007628
08/12/93
039
Lena Pierce, Court Reporter
National Records Service of Dallas
U.S. EPA Region 6 Site Files
Public Meeting Transcript
"Transcript of public hearing held on 08/12/93 at 7:00 p.m.,
YWCA, McFarland Branch Auditorium, Oklahoma City, OK"
-------
ADMINISTRATIVE RECORD INDEX
FINAL
SITE NAME:
SITE NUMBER:
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
DOUBLE EAGLE REFINERY SITE
OKD 980696470
007629 - 007634
09/03/93
006
Matthew Biddle, Department of Geography
University of Oklahoma - Norman, OK
Melanie Ontiveros, D.S. EPA Region 6
Public Comment Letter
"Comments on the proposed plan"
DOCUMENT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
007635 - 007653
09/04/93
019
Phillip Reeves, President
Enviro-Energy
Melanie Ontiveros, U.S. EPA Region 6
Public Comment Letter and Enclosures
"Comments on the proposed plan"
DOCUMECT NUMBER:
DOCUMENT DATE:
NUMBER OF PAGES:
AUTHOR:
COMPANY/AGENCY:
RECIPIENT:
DOCUMENT TYPE:
DOCUMENT TITLE:
007654 - 007656
10/04/93
003
LeAnne Burnett, Attorney representing the Double Eagle PRP
Group
Crowe & Donlevy
Philip Allen, RPM, U.S. EPA Region 6
Public Comment Letter
"Comments regarding the Record of Decision for Operable Unit
2"
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ATTACHMENT B
THE RESPONSIVENESS SUMMARY
The Responsiveness Summary has been prepared to provide written
responses to comments submitted regarding the Proposed Plan of
Action at the Double Eagle Refinery (DER) Superfund site. The
summary is divided into two sections.
Section I: Background of Community Involvement and Concerns. This
section provides a brief history of community interest and concerns
raised during the remedial planning activities at the DER site.
Section II: Summary of Ma~ior Comments Received. The comments (both
oral and written) are summarized and EPA's responses provided.
7. Background of Community Involvement and Concerns
Interest in the DER site on the part of the residents, local
government officials, and potentially responsible parties (PRPs)
has been moderate. Community relations activities were initiated
in 1989 when the site was proposed for inclusion on the National
Priorities List. A Community Relations Plan (CRP) was developed in
Dec. 1989, and the final published and released to the public on
Jan. 26, 1990. The CRP was prepared to identify and address
community concerns raised during the original RI/FS for the SCOU.
Copies of the CRP are located in the information repositories. The
CRP identified that the primary interest in the DER site lies
mostly with the residents who live near the site. Also, several
PRPs have come forward concerning the DER site as discussed in this
Record of Decision.
//. Summary of Major Comments Received
Public notice announcing the public comment period and opportunity
for a public meeting was printed in The Black Chronicle on August
5, 1993. The proposed plan fact sheet was also distributed to the
site mailing list on August 5, 1993, and a reminder was published
on August 12, 1993 in The Black Chronicle. An open house was
conducted the evening of August 12, 1993, to inform the public
about the Remedial Investigation and Feasibility Study Reports and
the Proposed Plan of Action. The comment period began on August 5,
1993, and was scheduled to end on September 4, 1993. An extension
to the public comment period was granted (per the PRP group's
request) which extended the comment period until October 7, 1993.
At the meeting, EPA and ODEQ officials discussed the contamination
problems associated with the ground water beneath the site,
presented the various remedial alternatives that were considered,
and presented the preferred alternative to address the ground water
contamination at the DER site.
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Approximately 20 people were in attendance at the meeting.
The public was given the opportunity to make comments or ask
questions. Seven people made comments or asked questions. A full
account of the public meeting can be found in the public meeting
transcript which is documented in the DER Administrative Record.
a) Verbal Comments
The comments/questions received orally during the public meeting on
August 12, 1993 are as follows:
Comment:
The commenter asked if she could obtain copies of the overhead
transparencies that were used during the presentation at the
beginning of the Public meeting.
Response:
The commenter was provided copies of the transparencies at the end
of the meeting the night of August 12, 1993.
Comment:
The commenter stated that she missed the introduction of the
speaker that presented information at the beginning of the meeting
and would like to know whom he was.
Response:
The speaker was Philip Allen, the Remedial Project Manager for the
Double Eagle site.
Comment:
The commenter stated that five other NPL sites are present in the
area; and that EPA investigates these sites separately. Since all
of these sites are located above the Garber Wellington aquifer, the
commenter expressed concern of migration of contaminants from all
the sites into the aquifer. The commenter further stated that the
sites need to treated as a Regional problem, with respect to the
overall effect in the long term of all these sites on the.aquifer.
Response:
The EPA has conducted investigations at all NPL sites within the
Oklahoma City area. The results of these investigations indicate
that there is no overlap of the contaminant plumes; therefore no
cumulative effects which would result in additional risk to human
health and the environment are evident. It should be noted that
the Double Eagle and Fourth Street sites were investigated
simultaneously due to their proximity to each other.
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Comment:
The commenter expressed concern that the Proposed Plans for the
Double Eagle and Fourth Street were almost identical, and asked if
the sites were similar enough to produce two documents so similar.
Response:
The Double Eagle and Fourth Street sites are very similar. The
types of operations conducted at the sites, the type of waste, and
the contaminants found in the waste are all so similar that the
documents are also very similar. These facts coupled with the
close proximity of the sites resulted in the EPA using the same
contractor to conduct the investigations, and allowed a cost
savings to the Government, since duplication of efforts were
minimized.
Comment:
The commenter asked what long term effect will these sites have on
the North Canadian River and future use of the river.
Response:
The results of the Remedial Investigation indicate that there will
be no adverse impact on the North Canadian River as a result of any
migration of contaminants from the Double Eagle site.
Comment:
The commenter asked what was anticipated for the future land use of
the sites once the remedial action was complete for the source.
Response:
When the remedial action is complete for the Source Control
Operable Unit, the land use is anticipated to continue to be
industrial use. There will also be a deed notice placed on the
deed to notify any potential future land owners of the ground water
contamination.
Comment:
The commenter asked if there are any viable PRPs on the sites.
Response:
There are several viable PRPs for the DER site, and a group of 22
participating PRPs have made a settlement offer; however, the
negotiations are ongoing, and the PRP search is continuing.
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b) Written Comments
The comments received in writing during the public comment period
are as follows:
Comment:
The commenter wrote that there was no North arrow or scale on the
map provided in the Proposed Plan; and that the abbreviations were
confusing.
Response:
The direction North would be pointing straight up on the page and
the map is not to exact scale. Additional maps are provided in the
Record of Decision with North arrows and scales. The abbreviation
"IH" implies Interstate Highway.
Comment:
The Proposed Plan on page 1 identifies the railroad adjacent to the
site as "Union Pacific" while the map on page 3 uses Santa Fe
(ATSF) .
Response:
The railroad lines are essentially identical, and ATSF stands for
Atchinson, Topeka and Santa Fe Railroad.
Comment:
The commenter wrote that it is not clear how or why EPA considers
lead the "major" contaminant of concern.
Response:
Lead is the contaminant that provided the greatest risk for the
Source Control Operable Unit.
Comment:
The commenter wrote that the EPA fails to provide justification for
the choice of Alternative 2 in the Proposed Plan.
Response:
The EPA proposed the Limited Action alternative (Alternative 2) in
the Proposed Plan on August 5, 1993. The Proposed Plan is intended
to be a brief outline of the rationale for proposing a remedy.
Further discussion of the rationale and justification is provided
in the Record of Decision. EPA believes that the Limited Action
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alternative is the most appropriate alternative for the following
reasons:
1) The ground water in the vicinity of the site is not used as a
water supply;
2) The extremely high concentration of Total Dissolved Solids make
the ground water undesirable as a water supply source;
3) Efforts to remove site-related contaminants in the ground water
would not improve its over all quality, and;
4) The North Canadian River is not threatened at the present time,
nor will it be threatened in the future by site contaminants.
Comment:
The commenter wrote that the section in the Proposed Plan
discussing ARARs is "vague and ambiguous", and "does not clearly
indicate if the chosen alternative actually does comply with Safe
Drinking Water Act or Clean Water Act provisions".
Response:
The ground water at the exposure point is not currently used as a
public drinking water source due to the high total dissolved solids
from past oil production activities. Continued monitoring will
monitor the attenuation of contaminant levels to MCLs. Since
modeling results indicate that the contaminant plume will not
impact the river, the potential ARARs associated with surface water
standards will be achieved. Additional action-specific ARARs
associated with implementation of this alternative include
standards for installation of additional wells and disposal of
miscellaneous wastes associated with the monitoring program such as
sampling equipment and produced water. Those wastes will be
properly disposed of in an appropriate facility in compliance with
the EPA's offsite disposal policy. Compliance with the action-
specific ARARs is not expected to present a significant obstacle to
implementation of this remedial alterative.
Comment:
The commenter wrote that it appears that the EPA's position is that
a primary advantage of Alternative 2 is that it can be implemented
quickly.
Response:
EPA disagrees with the comment. The "Limited Action" alternative
is consistent with Superfund guidance regarding ground water
remedies in areas of high Total Dissolved Solids. EPA believes
that the ground water in the area of the Double Eagle site would
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remain unusable after the removal of site related contaminants.
Although time to implement a remedy is a consideration in the
selection process, the effectiveness of restoring a ground water
resource is also considered.
Comment:
The commenter stated that Alternative 2 is a low cost approach, and
cost is not the primary criteria. The commenter requested that the
EPA consider "bioremediation and metals extraction" and requested
an opportunity to present his technology.
Response:
Cost is only one of nine criteria considered in the remedy
selection process, and is not considered one of the primary
criteria. Effectiveness in reducing risk, however, is a primary
criterion. Because the more costly "pump and treat" alternative
would not be any more; effective in the long term than attenuation,
in reducing the risk from use of the upper Garber-Wellington
(bedrock) aquifer, EPA does not believe that Alternative #3 is
cost-effective. Since a "pump and treat" system is not considered
a prudent remedy at the DER site for the contamination in the
ground water, a demonstration of the "bioremediation and metals
extraction" technology is not being considered at this time.
Comment:
The commenter wrote that the EPA did not give the public an
adequate opportunity to review essential information regarding
Operable Unit 2 prior to the Public meeting on August 12, 1993; and
the RI/FS reports were not available at the information
repositories prior to the meeting.
Response:
The public was given ample time to review the RI/FS reports prior
to the public meeting, and was given an extension to the normal 30
days. The EPA extended the comment period which allowed the public
a total of 64 calendar days to review all documents pertaining to
the site and submit written comments. Attachment 1 to this
Responsiveness Summary includes 2 Document Transmittal
Acknowledgement Forms. One of the Acknowledgement forms is from
the Ralph Ellison Branch library and the other is from the Oklahoma
State Department of Health.
Comment:
The commenter wrote that no specific monitoring requirements are
proposed under the remedial action plan, and that a list of
monitoring requirements should be made available for public
comment.
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Response:
The major components of the selected remedy are outlined in the
Record of Decision. The Limited Action alternative includes
quarterly ground water monitoring for the first two years, and
semi-annually monitoring for the following three years. The
specific contaminants that will be analyzed for during monitoring
will be determined during Remedial Design.
Comment:
The commenter wrote that data from the ground water RI/FS study
show that the Double Eagle site is hydraulically lower and is
impacted by polluted ground water from upgradient of the Double
Eagle site; and remediation of any ground water contamination
coming from upgradient of the Double Eagle site should not be the
responsibility of the Double Eagle PRPs.
Response:
The RI/FS states that there is a possibility of an off-site source
of contamination but was not conclusive. The contamination in the
ground water beneath the Double Eagle site is attributable to the
surface contamination, for which the PRPs are responsible.
Therefore, the PRPs are responsible for the ground water Remedial
Design and Remedial Action for the Selected Remedy - Limited
Action.
Comment:
The commenter wrote that part of the proposed Operable Unit 2
remedial design for the Double Eagle and Fourth Street sites is to
install 11 ground water monitoring wells; and that there was no
clear indication if this means 11 wells total or 11 per site.
Regardless, since the ground water is impacted by ground water from
upgradient of the site, no responsibility for installing and
maintaining monitoring wells on or around the Double Eagle site
should be placed on the Double Eagle PRPs.
Response:
The Feasibility Studies for the subject sites estimated 11 wells to
be installed during remedial action per site. However, the amount
of wells actually necessary to ensure that no future threat to
human health and the environment is posed by the contaminated
ground water, is a design consideration and the final determination
will be made during remedial design. Since the installation of
these wells and the subsequent monitoring and maintenance is
necessary due to the activities at the site, the PRPs are
responsible for this aspect of the site remediation.
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Comment:
The commenter wrote that lead levels in the ground water are
already below the clean up goals; and EPA should provide to the
public not only clean up goals for the contaminants of concern, but
also the current levels of contaminants in the ground water. By
providing only the list of contaminants of concern and cleanup
levels, EPA infers that each of those contaminants is above the
cleanup level. This is not the case.
Response:
The Proposed Plan contained the original contaminants of concern.
The final contaminants of concern and the Remedial Action Goals are
provided in the ROD.
Comment:
The commenter wrote that manganese is not a "hazardous substance"
as set forth in Sections 101(14) and 102 (a) of CERCLA or 40 CFR
Part 302; consequently, EPA does not have jurisdiction under CERCLA
to designate this compound as a "constituent of concern" at this
site, and thus EPA has no authority to establish cleanup goals in
the Proposed Plan for this substance.
Response:
Manganese is not a hazardous substance as set forth in Sections
101(14) and 102(a) of CERCLA or 40 CFR Part 302. However, Section
104(a)(l)(B) states that "Whenever there is a release or
substantial threat of release into the environment of any pollutant
or contaminant which may present an imminent and substantial danger
to the public health or welfare, the President is authorized to act
consistent with the national contingency plan, to remove or arrange
for the removal of, and provide for remedial action relating to
such hazardous substance, pollutant, or contaminant at any time..."
Therefore, manganese is still considered a contaminant of concern.
Comment:
The commenter wrote that Heptachlor and Aldrin, among others, have
been listed as contaminants of concern. Heptachlor and Aldrin are
not, however, typical ground water contaminants from oil recycling.
Response:
Heptachlor and. Aldrin are contaminants encountered in the ground
water at the site and pose a risk to human health and the
environment, and are therefore contaminants of concern. However,
Heptachlor and Aldrin are not normally expected to be encountered
as contaminants of concern at oil recycling sites.
8
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Comment:
The conunenter wrote that all cleanup levels for contaminants of
concern are inconsistent with the MCLs.
Response:
The remedial goals that were listed in the Proposed Plan were
tentative goals based on information from the Source Control
Operable Unit. The final Remedial Action Goals, if a ground water
restoration system were implemented, are listed in the ROD in Table
17. However, because the alluvial and upper portion of the Garber-
Wellington aquifers are Class III aquifers, these goals are not
applicable.
Comment:
The commenter wrote that in light of the low contaminant level in
the ground water, the low quality of the area's ground water, and
the plans to remove the sources of contamination at the Double
Eagle Site, "no action" is a more appropriate and cost effective
remedial option than EPA's selected "limited action" remedy.
Response:
The quality of shallow ground water beneath the Double Eagle site
has been affected by past oil and gas production activities in the
area, and the alluvial and upper bedrock aquifers are considered a
Class III zone. However, in order to ensure to the public that no
future threat is posed by potential migration of the site related
contaminants, continued monitoring and analyses are included in the
Limited Action remedy. EPA considers the Limited Action remedy to
be the most appropriate and prudent action at the site.
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Attachment 1
Document Transmittal Acknowledgment
From:
U.S. EPA Region 6
Sent by: Mava Davis
To:
of
Ms. Denyvetta Davis
Ralph Ellison Branch Library
2000 N.E. 23rd Street
Oklahoma City, OK 73111
(405) 424-1437
_, acknowledge that on this
ft
day
_, 1993,1 received from U.S. EPA Region 6, the second submittal
it'
!
of the administrative record for the Double Eagle Refinery Superfund Site - Ground
Water Operable Unit
[Documents included in the second submittal Ground Water Operable Unit AR
the July 27,1993 Remedial Investigation, the July 27,
August 5,1993 Proposed Plan of Action]
;:-:S -V$&&^:'
^f^^.r^f,^^--
/~\ -\1K. S&'rC.,0-..»i-;^,
^W/;vW '* ^&^%^^ftv
Please return this form to: Mava Davis, (6H-MQ
U.S. EPA Region 6
1445 Ross Avenue, Ste. 1000
Dailas,TX 75202-2733
(214) 655-6484 :
''-?-a?'.-1
YDPRA File 3732. sos
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Document Transmittal Acknowledgment
From: U.S. EPA Region 6 Sent by: Mava Davis
To: Mr. Scott Thompson 0206
Oklahoma State Department of Health
1000 N.E. 10th Street
Oklahoma City, OK 73117-1299
(405) 271-7159
. acknowledge that on this h day
is _£
of fvy^j'r 1993, 1 received from U.S. EPA Region 6, the second submittal
O
",
of the administrative record for the Double Eagle Refinery Superfund Site - Ground
'.'.''
Water Operable Unit .'V-
[Documents included in the second submittal Ground Water Operable Unit AR are
the July 27,1993 Remedial Investigation, the July 27,1993 Feasibility Study, and the
August 5,1993 Proposed Plan of Action] |: 4
Please return this form to: Mava Davis, (6H-MQ
U.S. EPA Region 6
1445 Ross Avenue, Ste. 1000
Dallas, TX 75202-2733
(214) 655-6484
-s^A
cc: DPRA File 3732. 803
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AITftCHMENT "C"
MARK S. COLEMAN W^^S^ DAVID WALTERS
Executive Director ^3£J;Ji&: , Governor
' State of Oklahoma
DEPARTMENT OF ENVIRONMENTAL QUALITY
November 15, 1993
<=% g rn
Don Williams, Chief "$1 "^ -3
Oklahoma/Texas Remedial Section (6H-SR) c: ^
United States Environmental Protection Agency S _g
1445 Ross Avenue, Suite 1200 02 r£
Dallas, TX '/5202-2733 ;£ fS
^ en
RE: Double Eagle Superfund Site, Oklahoma City, Oklahoma Q &"
Dear Mr. Williams:
My staff and I have reviewed the draft Record of Decision (ROD) for
the Ground Water Operable Unit for the Double Eagle Superfund Site
that was received by our office on October 25, 1993. Although we
concur with the selected remedy that is described in the ROD, we
cannot completely concur with the site characterization, ground
water modeling, and risk assessment sections. The DEQ does not
'-. believe that the hydrological setting or the extent and degree of
ground water contamination has been adequately determined.
However, DEQ does believe that enough site characterization has
been achieved to choose the appropriate remedy for the site and
expects the characterization inadequacies to be solved during the
Remedial Design.
Sincerely,
^ Dennis Hrebec, Ph.D., Director
Superfund Division
1000 KorthMM Tenth Stnrt, OkUlxma City. OUahaai 73117-1212
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