United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R06-93/081
September 1993
SEPA Superfund
Record of Decision:
Fourth Street Abandoned
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REPORT DOCUMENTATION 11. REPORT NO. 2. 3. Recipient. A_slon No.
PAGE EPA/ROD/R06-93/081
4. Thle and Subthle 5. Report Date
SUPERFUND RECORD OF DECISION 09/30/93
Fourth Street Abandoned Refinery, OK 6.
Second Remedial Action - Final
7. Author(a) 8. Performing Organization Rept. No.
9. Performing Organization Name and Addr... 10 Project TaskJWork Unh No.
11. Contract(C) or Grant(G) No.
(C)
(G)
.
12. Sponsoring Organization Name and Addr888 13. Type of Report & Period eov8r8d
U.S. Environmental Protection Agency.
401 M Street, S.W. 800/800
~ashington, D.C. 20460 14.
15. Supplementary Notes
PB94-964207
16. Abstract (Llmh: 200 words)
The 42-acre Fourth Street Abandoned Refinery site is an inactive refinery located in
Oklahoma City, Oklahoma. The Fourth Street Abandoned Refinery (FSR) site is situated
over the Garber-Wellington bedrock formati.ons, which constitute the most important
source of ground water in Oklahoma County. However, the contaminated ground water in
the upper-most bedrock aquifer is rendered non-usable (class III) due to total.
dissolved solids greater than 10,-000 mg/kg and potential sources of non-site-related
contamination. Residents .and industries in the area receive water from reservoirs
surrounding the city. Land use in the area is predominantly mixed industrial and
residential, with four schools. Another Superfund site, the Double Eagle Refinery
(DER) , lies about 500 feet southwest of the FSR site. From the 1940s through the early
1970s, three companies conducted waste oil reclamation activities onsite at FSR. These
activities included collecting, storing, and re-refining used oil, and distributing
recycled oil products. Since both the FSR and the DER sites recycled used oils in a
similar manner, the two sites contain very similar wastes. Sulfates in the waste
suggest the use of sulfuric acid in clarification of the used oils. Sludge generated
by the reclamation process was disposed of in onsite impoundments. Contamination from
(See Attached Page)
17. Document Analysis a. Descriptors
Record of Decision - Fourth Street Abandoned Refinery, OK
Second Remedial Action - Final
Contaminated Medium: gw
Key Contaminants: VOCs (benzene), DNAPLs
b. IdentlfierslOpen-Ended Terma
c. COSATI Fl8ld1Group
18. AV811ablihy Stet-nt 18. S8curhy CI88s (thIs Report) 21. No. of Pages
None 72
20. S8curhy Class (thIs Page) 22. Price
None
50272.101
(Sle ANSI.Z39.18)
SIIlnst,uctions on R.".ISB
OPTIONAL FORM 272 (4-77)
(~rly NTIS-35)
-------
EPA/ROD/R06-93/081
Fourth Street Abandoned Refinery, OK
Second Remedial Action - Final
Abstract (Continued)
FSR has contributed to contamination in an area just south of the FSR site, known as the
"Parcel H" area, and possibly to the North Canadian River. Physical dumping also occurred
in a landfill area just west of the ~Parcel H" area, but this waste is not attributable to
either the FSR or DER sites. Principal threat wastes to the ground water are "pools" of
dense non-aqueous phase liquids (NAPLs) submerged beneath the ground water or in fractured
bedrock, and NAPLs floating on water. Site investigations determined that the upper and
lower water bearing zones are hydraulically connected, which poses a threat of
contamination to the Garber-Wellington aquifer, and the Northern Canadian River through
horizontal and vertical migration, respectively. Onsite operations ceased in the late
1960s or early 1970s. In 1989, EPA performed a removal action which included fencing the
site and posting warning signs. A 1992 ROD addressed both the onsite and offsite sources
of contamination including soil, sediment, debris, sludge, and surface water as the source
control OU. This ROD addresses a final action for the contaminated ground water. The
primary contaminants of concern affecting the ground water are VOCs, including benzene;
and dense non-aqueous phase liquids (DNAPLs). .
The selected remedial action for this site includes installing warning signs to provide
notification prior to drilling in the area; installing additional, deeper ground water
monitoring wells further downgradient; allowing ground water to naturally attenuate;
providing a contingent remedy for installing additional monitoring wells, increasing the
frequency of sampling, constructing a containment measure such as a slurry wall, and
implementing a remedial action plan for extraction, treatment, and disposal of
contaminated ground water, if contaminant concentrations increase in any of the alluvial
or upper Garber-Wellington monitoring wells, or if detectable concentrations of site
contaminants are found in the lower Garber-Wellington monitoring wells, signifying
horizontal or vertical migration of the ground water plume; establishing a routine
monitoring and maintenance program for ground water samplingl providing for routine site
inspections; and implementing institutional controls, including deed restrictions. The
estimated present worth cost for this remedial action is $1,463,056, which includes an
estimated annual O&M cost of $74,880. No present worth or.O&M costs were provided for the
contingent remedy.
PERFORMANCE STANDARDS OR GOALS:
Ground water cleanup goals are based on SDWA MCLs and health-based levels for protection
of human health and the environment. Ground water is expected to reach MCLs for some
-------
RECORD OF DECISION
FOURTIi STREET REFINERY SITE
GROUND WATER OPERABLE UNIT
OKLAIiOMA CITY, OKLAHOMA
UNITED STA1ES ENVIRONMENTAL PROTEcrION AGENCY
-------
CONCURRENCE DOCUMENTATION
FOR TIlE
FOURTH STREET RECORD OF DECISION
~~
Geo qe Malone
.Office of Reqional Counsel
ite Atto
:J:;b/# LJ/L -
~l Edlund, Chief
superfund proqrams Branch
6H-S
qe Alexander, Jr
Office of Reqional
~fr~
~ illyn M. Davis t Director
Hazardous Waste Manaqement Division
-------
DECLARATION
FOURTH STREET REFINERY SITE
GROUND WATER OPERABLE WIT
SklIUtory Prqert!IJCe for Treatment
. tI8 G Principal Element
Ullot
Met tI1Ul Fwe-Yeor Review is Required.
SITE NAME AND LOCATION
Fourth street Refinery site
Oklahoma city, Oklahoma
STATEMEN1' OF BASIS AND PURPOSE
This decision document presents the selected remedial action for
the Fourth street Refinery site (FSR site), in Oklahoma city,
Oklahoma, for the Ground Water Operable unit. The Source control
Operable Unit Record of Decision for this site was comple~ed and
signed on september 28, 1992. The remedy for the FSR 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
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DESCRIPTION OF THE SELECTED REMEDY
This Record of Decision (ROD) addresses the contamination in the
ground water, which includes non-aqueous phase liquids. principal
threat wastes include "pools" of dense non-aqueous phase liquids
(DNAPLs) submerged beneath the ground water or in fractured
bedrock, or MAPLs floatinq on water. This Ground Water Operable
unit addresses the principal threat at the site by monitorinq the
ground water to ensure that the contaminant levels are reduced with
time due to natural attenuation, once the surface contamination is
removed. Past oil production activities have J::endered the upper
ground water zone non-useable (Class III aquifer) due to the
presence of high Total Dissolved Solids. The data also sugqests the
possibility of an offsite source of contamination. Therefore,
implementation of a ground water recovery and treatment system is
not considered appropriate at this time. A potential exists for
contaminants to migrate vertically to a potential drinking water
aquifer, therefore, monitorinq to ensure that migration does not
occur is appropriate.
This action is the second and final operable unit for the FSR site.
This second operable unit is also referred to as the "Ground water
operable unit" (GOU). The first operable unit for the FSR site,
termed th. Source Control Operable Unit (SCOU), addressed the
source of contamination both onsite and offsite, which included
surface sludqes, contaminated surface water and sediment, and
contaminated soil and debris.
The major components of the selected remedy include:
.
Installation of additional ground water moni torinq wells.
Establishment of a routine monitorinq and maintenance
program for ground water samplinq and modeling, to
evaluate contaminant level reductions, upon removal of
the surface contaminant source materials.
.
.
A five-year review to analyze the data .obtained and
computer modelinq to determine if contaminant level
reductions are beinq achieved as expected, once the
surface source of contamination is removed.
continqency action that could be implemented if the
contaminant concentrations increase or the contaminant
plume migrates horizontally or vertically to a useable
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, because treatment of the hazardous constituents
in the ground water was not found to be practicable, this remedy
does not satisfy the statutory preference for treatment as a
principle element of the remedy.
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.
If 3tJ~~~
J . Winkle
Acting Regional Administrator
Region 6
Date
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DECISION SUMMARY
FOR THE
FOURTH STREET REFINERY SITE
GROUND WATER OPERABLE UNIT
OKLAHOMA CITY, OKLAHOMA
L SITE NAME. LOCATION. AND DESCRIPrlON'
The Fourth Street Refinery Superfund site ("FSR site", or "the
site") occupies the Southwest Quarter (SW 1/4) of section 36,
Township 12 North, Range 3 West, Indian Meridian, Oklahoma County,
Oklahoma City, Oklahoma. Located at 2200 NE Fourth Street, the
site is bounded to the south by the Union Pacific Railroad tracks
(which includes the ATSF - Santa Fe railroad tracks), to the north
by Northeast Fourth Street, and to the east by Interstate 35.
Martin Luther King Boulevard lies on the west side of the site as
an overpass to the railroad tracks. Two active industrial
facilities (which have not been associated with past site
operations) also lie adjacent to the mid-northern portion of the
site, just south of Northeast Fourth Street.
The Double Eagle Refinery site ("DER site") lies about 500 feet
southwest of the FSR site, just south of the railroad tracks and
just west of Martin Luther King (MLK) Boulevard. The FSR and DER
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 DER site as necessary. The DER
site will be addressed in a separate ROD. Figure 1 provides a
general location map. Figure 2 provides a schematic of both the
FSR and DER superfund sites, and shows the location of each site in
relation to the other. Figure 3 provides a site layout for the FSR
site.
Although industrial areas surround the site, the land use within ,a
1 mile radius of the FSR site is mixed industrial and residential.
One residence is located adjacent to the pipe storage Yard, just
north of the railroad tracks and to the east of Martin Luther King
Boulevard. A small neighborhood is located about 1/4 mile to the
northwest of the MLK Boulevard and Northeast Fourth Street
intersection. 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.
- - - - ---
-- ----- --
-------
OK1.AHOMA
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DOUBLE ~ AND FOURTH STREEi
SUPEnFUNO SITa.
OKLAHOLtA CITY. OKLAHOUA
2
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APPROXIMATE SCAL£
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FIGURE 2 SCHEMATIC OF SITES
DOUBLE EAGLE AND fOURTH STREET
SUPERfUND SITES
FWOR DANIEL OKlAHOMA CITY. OI(lJ\HOMA
DIR: P: ENVIRO 06639631 . ENV CAD fiLE NO.: flG20ERI
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- BURIED WASTE
t:1 OIL DERRICK
FIGURE 3 SCHEMATIC OF SITE
FOURTH STREET
FOURTH STREET SUPERRJND SITE
OKlAHOMA CITY. OKLAHOMA
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The FSR site has contributed to offsite contamination in an area
just south of the site, referred to as the "Parcel H Area". 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.
IL SITE mSTORY AND ENFORCEMENT ACl'IVITIES
SiU lIlstor1
The Fourth street Refinery collected, stored, and re-refined used
oils and distributed the recycled product. The refinery was active
in the early 1940's and was noted on historical aerial photographs
available as early as 1941. Refining operations were conducted on
land owned by the Chicago, Rock Island and Pacific Railway Company.
Planet Oil and Refining Company participated in the waste oil
reclamation business during the early part of the 1940's through
the early 1960's. Elliot Refining Company conducted waste oil
reclamation activities during the late 1940's through the 1960's.
Salyer Refining Company performed waste oil reclamation operations
from the late 1940's through the 1960's. These three companies
conducted waste oil reclamation activities on-site. operations
ceased in the late 1960's or early 1970's. .
Refinery operations at the FSR site apparently recycled used oils
in a similar manner to that process employed at the DER site.
Sulfates in the waste suggest the use of sulfuric acid in
clarification of the used oils. Sludges generated by the
reclamation process were disposed of in on-site impoundments.
A preliminary assessment of the site was completed in April, 1984,
and a reconnaissance site inspection was conducted in October,
1984. subsequent soil and water sampling was performed in June and
December of 1985, in the Main site Area. Further soil and offsite
municipal well water sampling was conducted in 1986, along with the
installation of ground water monitoring wells. An Expanded site
Inspection was conducted in 1987 throuqh 1988, which confirmed that
the site should be ranked for inclusion on the National Priorities
List (NPL). In March 1989, the FSR site was included 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) project for
the Ground Water Operable unit (GOU) was initiated in June 1992 for
the FSR site; and the RI and FS reports were both completed in July
1993. Due to the close proximity of the FSR and DER sites, and due
to the similar types of wastes present at both sites, EPA assigned
one contractor to conduct the RIfFS 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.
Enforcement ActivUlG
In July, 1989, General Notice Letters were sent to the three (3)
current owners of the FSR site. The General Notice Letters
informed these parties that they may be responsible for future
response measures taken at the site. These parties were afforded
the opportunity to conduct a removal necessary at the FSR site;
however, the parties expressed an unwillingness to perform or
finance the removal action. In september 1989, EPA performed the
removal action, which included fencing the site and posting warning
signs to alert potential trespassers.
In October, 1989, Special Notice of potential Liability Letters
were sent to three (3) current owners, affording them the
opportunity to conduct the RI/FS at the FSR site. The current
owners declined to participate in either the financing, or the
actual performance of the RI/FS.
Later, in 1990, the RI/FS project for the Source Control operable
Unit was initiated by EPA, and has been completed. simultaneously
with the performance of the RI/FS, EPA proceeded to collect
liability information regarding the PRPs activities at the site.
On March 12, 1993, 7 PRPs (3 current owners and 4 newly identified
PRPs) were issued Special Notice Letters affording them the
opportunity to participate in the Remedial Design/Remedial Action
(RDfRA) for the Source control Operable unit. Only one (1) PRP
submitted an offer to reimburse the EPA. No settlement agreement
has been reached in regard to that offer.
On March 31, 1993, General Notice letters for the RD/RA for the
Ground Water Operable Unit were issued to the four newly identified
PRPs. That letter also included information "regarding" the RIfFS
for the GOU which was already underway. Only the newly identified
PRPs were issued General Notice letters at that time, since the 3
current owners were previously given an opportunity to participate
in RIfFS activities in October 1989, before the site was separated
into two Operable Units. Additional information concerning the
Operable Units is given below in section 'IV.
In. mGHLIGHTS OF COMMUNllY PARTICIPATION
This decision document presents the selected remedial action for
the GOU for the FSR superfund site, in Oklahoma City, Oklahoma.
This action is chosen in accordance 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
1.1.3 (k) (2) (B) (i-v) and 1.1.7, were met during the remedy process. The
RI and FS 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 Oklahoma Department of Environmental Quality (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 Chronicle, on August 5, 1.993.
The EPA and ODEQ held an Open House in Oklahoma City on February
1.8, 1.993, to explain the superfund process and to notify ~e public
that RI activities for the GOU had bequn. 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, 1.993. No requests were received to extend the comment
period. One written comment was received 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 ODEQ 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 comment 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 RIfFS project for the SCOU for the FSR 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 seou, the shale
layer was not found to be present. Shallow and deep alluvial wells
were installed around the perimeter of both the FSR and DER 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 .(GrOU11~ w~t~r - op~rapl_e 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
the FSR site pertaining to the surface contamination are the acidic
sludges 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 (NAPLS) submerged
beneath ground water or in fractured bedrock, and NAPLs floating on
ground water. The contaminated ground water in the area of the
site is classified as a Class III aquifer by EPA. Class III
aquifers are considered unusable due to the presence of Total
Dissolved Solids (TDS) in excess of 10,000 parts per.mil1ion (ppm).
The remedial obj ecti ves 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 ~seable
ground water supplies.
v. SUMMARY OF SITE CllARAcrERlSTICS
General Overview
The FSR site and the Parcel B Area (located just south of the FSR
site) are not located in the 100 year floodplain. Prior to
construction of Interstate 35, the North Canadian River meandered
through the FSR site. During construction of the highway, the
river was diverted to the south side of I-35, and is now located
approximately one half-mile to the south of the FSR site.
Ponds on the FSR site and portions of the Parcel B 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 aerial photographs and not on actual site
surveys. During the RJ:, it was determined that the vegetation
around open water areas in the eastern portion of the FSR site and
on Parcel H, appear to consist of grasses likely to be prairie
grass species rather than wetlands species.
-- .--. ---
-- - - - ---
-------
Twelve alluvial monitoring wells were installed at the FSR site.
Five of the alluvial monitoring wells were installed with 10 feet
screens placed between 8 and 18 feet in depth. six of the alluvial
wells were installed with five feet screens placed at about 33 to
38 feet below ground surface; and the remaining well (FFMW-007)
screened at 12 to 17 feet below ground surface. six bedrock
monitoring wells were installed around the perimeter of both the
FSR and DER 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 29 to 39 feet below ground surface across the
FSR site. The monitoring well locations are shown on Figure 4.
GeneNl Geology tmd Hydrogeology ClulrtlClerlzatlon
The FSR 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 FSR 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 FSR site begins
approximately 29 to 39 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.
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 freshwat~r~upply -
-------
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DOUBLE EAGLE AND fOURTH STREET
SUPERFUND SITES
OKlAHOUA CItY. OKWlOMA
ENY CAD filE NO.: flG3-2R'
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t~~~1J QABR-SNfOSMNE
,Y.I. . 20
~==-
~OTES: .
1. SllSURf'ACE GE:OUJGIC ~ ME IIASID ON
SAMPLE oe.cRPI1OHS FROM UCiNROIIIIO WELL 8OAIIO
LDGS. G£OLOGIC CONDIIIONS SHOWN /MAY fROM UONItUIIINCJ
. WEWI ARE ~ AND IIA"NOT IIEPR£SDfI' AC1UAL
. c:ota11OHS. . ...., :',;'. '", :.". .
2. SU fIGURE S-2 _'lItE UICA1IIN at H CROSS-su:naN.
NMI1I1N11L IS tIDT TO st.ALE
FIGURE 6
ara 0fIII! CROSS SEcnoH A-It
DOUBLE tMlE . fOURTH S1REEf
SUPfRfUHO SITES
DIR:
. .
'.. ~.
':'1' !
" ",
";~~':~: '..t~:; ::~~.~,::: ,.
. ;<'.~
. ~j" :. :'.: .
,,":;~'hhF#1.it~}"~; .
.~. ;"
'. " .: . . . ~
. .
,"',
>; ,".-:
.".
. ~ ...'.".
-------
-'It.
is the presence of high Total Dissolved Solids (TDS) in the ground
water. Shallow ground water 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 FSR site revealed
that the TDS ranged from 1,340 ppm to 61,000 ppm with an average of
about 10,900 ppm. 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 2600 ppm to 110,000 ppm with an average of 31,500 ppm for the
six bedrock wells installed aroqnd the perimeter of both the FSR
and DER sites. 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 alluvial
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.
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 FSR and DER 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.- ------.-
13
-------
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LEGEND:
.FOP-IO fllEZOU£TER
.""'-003 IIONI'ORINO.WEU.
FI/Dt/HI STAfF CAUGE
8£HZOfE PlUME (ppb)
ms CONaNfRAfIONS (PPl")
APPROXlUAfI: sc:AU:
~ 4~
Fm
I
800
DDPOSED WAStE
~
FIG.
7
tDS CONCENTRATIONS
-------
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
groundwater 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 4.5 to 9.5 feet
below ground surface. Subsequent ground water monitoring indicates
that the ground water levels range from about 4 to 12 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 01 Contmnlntltlon
The Ground Water RIfFS 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 RIfFS 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 rel~ted to the refinery process. The most commonly found
organic chemicals were Chlorinated Hydrocarbons and Benzene
compounds. Lead and arsenic were the primary metal contaminants
found in ground water samples taken during the investigation. The
cac's are discussed in detail in section VI - summary of site
Risks.
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. S 9601(14), and
40 C.F.R. S 302.4. Although there was no free phase contamination
noted during drilling operations, these chemicals are contaminants
associated Dense Non-Aqueous Phase Liquids (DNAPLs). Past EPA
experience indicates that sites containing DNAPL contamination are
very difficult to remediate.
The maximum, minimum, and mean concentrations of contaminants found
at the FSR site are listed in Table 1. Ground water samples taken
at the site also contained high concentrations of Total Dissolved
Solids (TDS). Five of the six bedrock aquifer samples had
concentrations greater than 10,000 ppm, indicating that the bedrock
aquifer is a Class III aquifer according to the EPA Ground Water
Classification system.
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 bedrock aquifer at the FSR site boundary.
-------
Table 1
Monitoring Well Statistical Data Summary
NO. OF MAXIMUM MINIMUM MEAN
DE1'EC1'S
PARAMETER 1Uft"-\ IU~\ fUM'
AlumInum ~ 679OO.co 152J1O 1080U11
Anllmonv ,. 14.70 14.70 1US
Ar88nIc 2!W8 149.00 5.2D 1UC
BarMn ~ 1780.00 1~JIO sauo
14/.18 4.00 1.30 1.13
Caclmlurn 1. 1.30 1.30 1.115
CaIcIImI 3$18 1190000.00 77400.00 --
CIIronWrn 17138 71.80 2.80 11.A1
Cobd 1!i38 2UO 5.70 ...
ICoDD8r 8008 22.80 7.2D 7..-
Iron 31138 5S8OO.oo 1710.00 111285A8 ,
I.8ad rt138 73.20 1.70 14M
~~ HI38 37SOOO.OO 12700.co 77la.11 :
.. 5350.00 310.00 18.42:
NIcIf8I 11138 54.10 7.40 11.07:
PoIu8Un 38138 24200.00 830.00 8410.. .
8eIInIuIn U8 12.80 ruo U2
80cIuIII 3!i38 3130000.00 120.00 85U1.11 :
Vlnadllln . 3CtI38 1110.00 3JlO 4U3:
2Jnc r.we 214.00 7.40 K.CI8
.C:~ U8 27.00 8.00 7.:
1:we 12.00 1.m 4.8 :
Ac8IonI 1CW8 -.00 4.m 23.81 ;
CUbon DI8uIIId8 ,. 1.00 I.GO 4JiB !
1.1-DIcHaroII18nI "11 2.00 2.CIO 4.8 I
1.1-DlchlarCM1W18 7. 12.00 2.00 4.
1,2-DIctIIaro8I18I8 8.&18 21.00 1.00 5.-
1,2-DIc:IIIaroIbn8 .. aoo 2Z.OO U8 i
2-BuIancN 2M 8.00 7.m ...
1 1 1 -TddIIonI8Ihan8 ,. 4.GO 4.GO .... '
Tio~.. ... 11.00 2.00 4.12 ;
B8nZ8I8 , 1138 240.00 2.00 12.11 .
ChIarobInZII8 2M 28.00 I.CIO &JII.
I BIIvI B8nrIIn8 ,. 8.00 ..00 4A i
XYI8nI8 ftDtII) US 2CIO.OO 10.00 ,.....
Ph8noI .us 17D.OO 8.CIO 1Q.7I i
... tiM a.oo 2.00 a.W
1 DlcNaroll8nz8M ,. O.IID O.IID a..
1,4-DIc:I....... 2M 1.00 IJIO a..
1,2-1:IIc:IIIaroII818 ... 27.00 1.110 ...
4- 1. 8.00 8.CIO U1
1. 2.00 IJIO a..
2.4 2.GI 71J1J 2.00 1.11
M8 ss.oo IJIO ...
2 U8 G.7O UO 4.1t
,. . OJM OJM ...
US G.IO OJIO ..
Me 11J1J UO ....
PhlMo".". ,. 0.40 OAO S..
AnIIIr8DInI 1J38 0.40 GAG 8~.
DI-n .... 12t38 2.CIO UO -.1t
- ,. - . --. o.eo 0.80 ...
bIIC2- 14/.18 200.00 o.so 8M
CIrb8ZD/8 1/1' o.eo UO .t:n
LIndane laanuna-BHQ 1fD 0." 0.11 .OM
d8IIa-BHC 'Hl'1 om O.os OJD
-------
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
groundwater gradient is to the southeast, although some mounding
was noted directly under the site. Modelling 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 Miaration in the ~lluvial ~auifer
The water level measurements indicate a ground water mounding
effect near standing bodies of water in and near. the FOurth street
site However, regionally, the ground water in the alluvium flows
towards the North Canadian River (southeast). The average ground
water flow rate for the FSR site was estimated to be 20 ft/year for
the 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, contaminated soils were
discovered, 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.
It is important to note that contaminant mass loading rates were
estimated to provide an approximation of contaminant concentrations
at the current well locations. Table 2 shows a comparison of
observed and modeled predictions for benzene and chlorobenzene
concentrations in the alluvial aquifer. Table 2 shows that when
observed benzene concentrations at FFMW404 and observed
chlorobenzene concentrations at FFMW505 are matched by the model,
predicted concentrations at other monitoring wells are
significantlY higher than those observed. This same trend is also
observed for other contaminants.
contaminant Miaration in the Bedrock Aauifer
The water level measurements from the bedrock monitoring wells
indicate that the flow direction of the upper portion of the
Garber-Wellington aquifer is generally to the southwest. 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 lonqitudinal and transverse dispersivity. Figure 9 shows
the predicted current benzene plume in the bedrock aquifer based on
the aforementioned assumptions. Table 3 shows a comparison of
model predicted concentrations and analytical results for the
-------
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I ci
~
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~ 1CI.~ElCI
a:
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200
fHMW-001-0
PARCEL "11 AREA
-0 BMW-J
. I
o
1 00 200
FEET
.
400
ORIGIN
MONITORING WELL
CONTAMINANT PLUME (ppb) FWOR DANIEL
~
. FIG. 8 PREDICTED CURRENT BENZENE PLUME
IN ALLUVIUM fOR 50' lONGITUDINAL DISPERSIVITY
FOURTH STREET SUPERFUND SITE
OKLAHOMA CI'TY. OKlAHOMA
-------
TABLE 2
COMPARISON OF OBSERVED AND MODEL PREDICTED BENZENE AND
CHLOROBENZENECONCENTftATIONSIN ALLUVIAL MONITORING WELLS
MONITORING WELLS BENZENE CHLOROBENZENE
. Observed Predicted Observed Predicted
~
\0
FFMW001 & FFMW101 ND 3001 1 J 667
FFMW002 & FFMW202 ND 193 3 430
FFMW003 0.8 J 112 40 249
FFMW004 & FFMW404 110 110 ND 245
FFMW005 & FFMW505 24 130 290 290
FFMW006 28 203 1 J 450
FFMW007 & FFMW707 1 J 297 48 660
Notes: 1 - All concentrations are given In ug/L (Ppb).
"J" - '!he associated numarical value
is an est:imated quantity.
-------
"
"
"
t\)
o
)
~
OIL
W WEll
t::I!J
a
.
o
1 00 200
FEET
I
400
fiG. 9 PREDICTED CURRENT BENZENE PLUME
ORIGIN IN BEDROCK
MONITORING WELL FOURTH STREET SUPERFUND SITE
CONTAMINANT PLUME (ppb) PWOR DANIEL OKLAHOMA CITY. OKLAHOMA
-------
Table 3
COMPARISON OF OBSERVEDAND MbDEl PREDICTED CONTAMINANT
CONCENTRATIONS IN BEDROCK MONITORING WEllS
t.)
....
ANAL YTE BMW-3 BMW-4 BMW-5
OBSERVED PREDICTED OBSERVED PREDICTED OBSERVED PREDICTED 2
BARIUM 1310 1 1310 2ZT 212 1210 2447
MANGANESE 18300 18300 483 1150 3890 36100
ALDRIN 0.01 J 0.01 ND 0.0003 ND 0.02
BENZENE 45 62 ND 2 125 J 125
CHLOROBENZENE ND 106 ND 3 212J 212
CHLOROFORM 0.9 J 1 0.7 J 0.03 2 2
1,4-DICHLOROBENZENE ND 13 ND 0.4 25J 25
1,2-DICHLOAOETHANE 15 15 ND 0.4 12 30
HEPTACHLOR 0.03 J 0.03 0.01 J 0.0009 0.02 J 0.06
mlCHLOROETHENE 4 4 ND 0.1 7 8
VINYL CHLORIDE NO 13 ND 0.4 25J 25
. . Notes:
1 - All concentrations are given In ug/L (ppb).
2 - Predicted concentration at BMW-5 with flow towards BMW-5.
"J" - '.lt1e associated nunerical value is an estimated quantity.
-------
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LEGEND:
8f1)P-IO PlEZOM£1(R
. NW-003 NONIToafO tIUL
F't/DI," , STAFF OAUCE
- - - BENZOfE PlUME (ppb)
ms CONCOIIRA11ONS (ppm)
N'PROXlMAT£ SCAlE
~ I
° 100 200 400
I
800
Fm
DVIPOS£O WAnt
~
~IGI 10 IDS CONCENTRATIONS
WITH PREDICTED BENZENE PLUME
FOURTH STREET SUPERFUND SITE
OKLAHOMA CItY, OKlAHOMA
ENY CAD FilE NO.: FGJ11FS
-------
samples from the bedrock monitoring wells. Also, Fiqure 10 is
provided to show the current benzene plume at 20 ppm, with the
respective level of TDS contamination.
na"ac~ on ~he lIor~h Canadian River
The receptor point for the alluvial aquifer was assumed to be the
North Canadian River (River). Fiqure 10 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 Fourth street site.
Table 4 shows the maximum concentration predicted by the model in
the alluvial aquifer just before the qround water is discharged to
the river. Data in Table 4 also indicates that mixing of qround
water with the surface water in the river reduces contaminant
concentrations siqnificantly. This results in concentrations
siqnificantly below the ambient water quality criteria for the
river as shown in Table s.
VI. SUMMARY OF SITE RISKS
Hunum Health RIsks
As part of the Remedial Investigation for the GOU at the FSR site,
a quantitative risk assessment was performed to estimate human
health risks posed by the miqration of contaminants within the
ground water, and lateral migration of contaminants to surface
waters from the FSR site. This section presents a summary of the
Baseline Human Health Risk Assessment for exposure of humans to
contaminants existing within the ground water that are attributable
to the site. The baseline risk assessment provides the basis for
taking action and indicates the 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 qround 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 qround
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
-------
Parameter
Table 4
IMPACT OF FOURTH STREET SITE ON NORTH CANADIAN RIVER'
THROUGH ALLuVIUM AQUIFER
Bac ground
Vin I Chloride
1,2- Dichloroethane
Trichloroethene
Benzene
Chlorobenzene
1,4- Dichlorobenzene.
bls 2-Chloroeth lethe
Arsenic
Barium
Be lIum
Cadmium
Chromium
Lead
Nickel
Vanadium
~
~
On -site Concentration
Maximum Location
FFMW505
FFMW404
FFMW404
FFMW404
FFMW505
FFMW505
FFMW707
FFMW404
FFMW404
FFMW007
FFMW002
FFMW003
FFMWOO2
FFMW101
FFMW007
1 - No adsorplon assumed for organic contamnants. See Table 4-2 for retardEilon factors for metals.
2 - No retardation was assumed for barium and chromium.
-------
Table S
Water Quality Criteria Cor the
Protection of Fresh Water Aquatic We
EeoIogical Risk Assessment
Fourth Street Site
t\)
VI
TOIic:ItI V... (uaIU
c--~ of CaaI:era PredicCed Am8 CIIraaic
&afKe W....
c.,..,...~~ (VIfI1 0kIabama Vm-A Other 0Id8b0aIa VSEPA OIlIer
wQC wQC c.iferia4 wQC wQC' w~
V'~ 0JI0ride 0.065 J - - - - -
I,2-DidIIoIoedwIe 0.069 - - 118,000 - - 20,000
Tric:IIJoroeIban 0.001 - - 18,000 - - 8,400
Bear.ene 0.157 - - 5,300 2,200 - -
a.Jocobemeae 0.350 - - 250 - - 50
1,4-Dicblcx~ 0.057 - - 1,120 - - 761
b~ 0.003 - - 238,000 - - -
AI8Iio 3.93 360 360 - 190 190 -
Barium 16.4 - - 50,000 - - -
8elyUium 0.000 - - 130 - - 5.3
0Idmhurt 0.003 143 17 - 3.10 3.10 -
0Ir0miuni (foral) O.onl - 16 - so II -
Le..t 2.68 417 417 - 16 16 -
Nkbt 0.034 4200 GOO - 466 466 -
VIIIIdium 7.67 - - - - - -
J. From T8b1e 5-11
a. 0kIIh0mI VI" ~ Crit8ia (1989)
So VSEPA W- QuIIity Cderia (1986)
.. Prom CJemeaI8 (1985) 01' eItimIted IoweIt obIaYecI effect vllue (USEPA 1986).
J. Not available or not Jllllliiable
.. Bued 00 Iwdneu value of 360 mg/I u CaCQ .. provided in Section 4.0
,. USEPA Criteria tbr hoxavaled Cr .... Otlahoml Criteria tbr !QCaJ Cr.
Sb8cIed boX8I indic8Ie ~.- ofwarer quality criteria vllue.
FILII: H,~1IFINALYI'o\8I.EIIIIII$T8L.F1
-------
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 10-8 (1 in 10,000 to 1 in 1,000,000
respectively) excess cancer risks for hazardous vaste site
remediations. The NCP stipulates a 1 X 10-8 risk level as a point.
of departure in risk management. When evaluating ground water
contamination, EPA also considers the Maximum Contaminant Levels
(HCLs) in the Safe Drinking Water Act as appropriate remedial
. 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 Garber-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. The risk assessment is based on the
establishment of a future pathway by the use of ground water at a
depth of 60 feet below the ground surface.
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 (nhealth 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 fora of cancer
from everyday sources, over a 70-year life span is estimated at a
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.
'1'0 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.
ldentijfclltlon 0/ CMmlctIIs 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.
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 ip 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.
Toxlclt] AssISSIMIIt
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
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 -iILthis assessment
-------
:.,,:,
Table 6
DetermiDatiOD of FilIal COCS
Fourth Street Site
eo..I",..d_.d~ of Coac:era
Risk Criterioa Dermal ClildlAdult
CaJM1IatM Risk
aDd
JnhqJafInn
OIDdlAduIt
CARCIN()GINS
AJdriIiI
~
.1&7
1&7
-
1&7
1&7 6.7B-7n.9&6 HA4 2.5fr.7/S.0&7
~_. 1&7 4.mlll.3Ji..7 1.m6fS.9&6 5.m8ll.2E-7
1.4-DidI1cxn1-,...,.,I 1&7 1.4&613.9&6 HA4 3.0B&'6.256
1~ 1&7 HA' 3.2&519.9&5 1.3&5/2.6&5
1&7 1.6&714.7&-7 HA4 1.3B6'2.6&6
~
~ 1&7 6.7B-7n.9&6 5.7&7n.7&6 . 4.2B-7J8.5B.7
- - ......t>..~4.--
Vi Q1ori&I 1&7 NA' 9.3&5/2.9&4 2.4B4'4.9&4
NON-CARCINOGENS
1&01 4.4&2I1~1 NA4 6.9J3.2fJ.4&2
~ 18-1 HA' HA4 7.5113.51 ..
Barium' 1&1 NA' NA4 - 2.OS+0r7.9&1
':; :.:v,:;,.:':':,: ,:',:~ "
.a.boI-,~w}
1&1
9.OB-2I2.GI
5.8E+OIJ.6Ji+O
5.8&112.4&1
1~-~
a.l~
1&1
1&1
'~',,~.:~"~::~:~#,~~~:~., ::",)::.:.. :.
;,~,:¥:'::i5:f..:~~~' \~~~:Kfl:~~~;.~/~'~ i~~~1~~M=':.~.~~ ~fr;'~
3':';'':'~ :,ARt . :,:.i#l~~'
~ . .;;,.~ ..~~'.:.-?:ofi4.':"='''''
.,~o.;o~.../..<::t:.:~o:~"";.~.~'~':~o..:':'t~:S: .x..~i>( o. ',.:'
~;:,:¥;1,"::\.$ O.-ioi-~,..O"''''">';~'o:.''~... ~~~ : .*...
~,~ .~\!~ :~t.~::'1~~'Zf ~~~l~: .;t:~:
.. ''''~;a;' ~'~~... ~~;,' "..c~~;,'~~--=\~
,~,""\:'.f:~. ;'r'-;..~.:'~~,~,"~~~'-:.~
s
,
.,
.
CX)C &om lilt .........:..w by ~ ~ Maaaaer 'ADeD 199'J).
CX)C ~~ lei' . "'.v..- dBriIied In SectKa 5.2.2 oflhil ftIIXIIt. .,
~ DDt ~ CD ~ ..~W'ft!.. See Secdm5.2.Uofdlil ~
~ DDt ~ CD ()o1l.h.~.:I-r 810 Jaw 1IeaIy'. :uw n-.-t dOt ...a-.~.. wciJbL See SeC8iaD
5.2.4.2" of daii ftP.ort.
~1:b:~=-we118. No.rfWntdllDp~
~IPIIiaD for CIIdmium VIIS DOt ~Added 1iDce.n Jabo~ cilia for Ibo Wrack wen. W8I ftjectec1
SbadecI caPnm-t. wae dropped . cae ... em riat criteria.
.
2
,
.
~H.~'1'1U8
-------
include the reference dose (RfD) used to evaluate noncarcinoqenic
effects and the slope factor to evaluate carcinoqenic potential.
RfDs have been developed by EPA for indicatinq the potential for
adverse health effects from exposure to contaminants of concern
exhibitinq noncarcinoqenic effects. RfDs, which are expressed in
units of mq/kq-day I 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 drinkinq water) can be
compared to the RfD. RfDs are derived from human epidemioloqical
studies or animal studies to which uncertainty factors have been
applied (e. q. I 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 noncarcinoqenic effects to occur. The purpose of the RfD
is to provide a benchmark aqainst which the sum of the other doses
(i.e. those projected from human exposure to various environmental
conditions) might be compared. Doses that are siqnificantly hiqher
than the RfD may indicate that an inadequate marqin 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 I noncarcinoqenic or carcinoqenic
risks associated with dermal exposure can be evaluated usinq an
oral RfD or-an oral slope factor. Exposures via the dermal route
qenerally 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 inteqrated
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 orqanisms 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 performinq the same or
similar functions. To lose orqan function, a siqnificant 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 exhibitinq noncarcinoqenic effects
for use in risk assessment are generally developed usinq EPA 's RfDs
developed by the Reference Dose/Reference concentration ("RfD/RfC")
Work Group and included in the iRiS.
For chemicals that exhibit carcinoqenic effects, most authorities
recoqnize that one or more molecular events can evoke chanqes in a
sinqle 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 10.8 (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 mq/kg-day, to provide an upper-bound
estimate of the excess lifetime cancer risk associated witll
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, quali tati vely 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
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
B1) 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 has been assigned
a carcinogenicity weight-of-evidence category. These chemicals are
presented in Table 7 with the respective Referenced Doses and
Potency Factors. .
Hunum RIsk Clumu:teriztltUJn
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 (RNE)
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-
ters. An estimate of average exposure is cal.culated by using
averaqe or central tendency factors (Central Tendencies are.
discussed below).
-------
.-.
Table 7
Refereace Oases aDd Slope FactGrs for ('«)o.,...~dnank of Caaeem
. Fourth Street Site
",
co-o.-_nt of Caaan 1tfD(O) Itf1)(1) SF(O) $F(l)
maJkrI., ffll/kllday mrJlr.llday mrJkllday
~tMn!I 6.O&C -' NA' . MA'
AIdriD 3.0&05 ..) 1.7E+Ol 1.7E+Ol
",... 3.~ ..) 1.IE+OO' 5.0E+Ol'
Barium 7.c&G2 ..) NA' NA'
~ -' -' 2.9&02 2.9B-01
C2IIanIIIIID 6.05QS ..) 13B+OO I.3E+OO
~4)1- 1.0502 ..) 6.tB-03 LtBG1
~ 2.0&02 5.0&43 NA' &2
I>DicIdoiabcmao 9.0&02 4.CJB..01' NA2 &'
1""'~ ..) 2.0B-0l 2.45C -'
1>~ ..) -' 9.1E02 9.1]).02
a.l~ 1.CJB.02 -' NA2 &2
1Lt....a.1ftr' 5.0&04 ..J. ~+OO 4.58+00
tI..pN-i' " 5JJB.03 1.0&04 NAt NA'
~.~~ -' _I 1.1~ 6.~
V"my) Q1oride' ..) -' 1.9B+OO 3.0B-0l
~:. .
,.
,,- .
RtD(0)-
RfD(I) -
SP(O) -
SP(I)-
. ,
.0000nlweace cICIIe tbr ~ eft'ecII
w.-~ ~.. dale for uQ/HII~ etrecII
0raI1kIpe ,.. tar -~ cft'ecIa .
1--t.tLw.11apo fleW far --.. c&:Is
,- . .'
I
.
2
,
, .
s
- ~ daIa weI8 - &VIiJIbIe flam 1RJS (1993) or BEAST (1992). .
NA ~ ooe"amm.nt bas - beat &..-II\4.11ed to cdDbit CIICiDapic eft"ecII in "-
Ta1icity fidar fiom HBAST (1991)-
Toxicity tictDrI pIOVidrd by EPA ... 6 (RauII8t 1993&).
Ta1icity f8cIoI8 pavided by EPA ReaiaD 6 {RII8cIIer 1993b).
FILE: ~..............~
-------
The exposure point concentrations were based on ground water
modelinq performed in the RI. Exposure concentrations were modeled
for five year time intervals. The hiqhest concentration occurs at
year o. . Risk calculations for child exposure are based on the
assumption that the exposure point concentration remains unchanqed
over the six-year exposure duration. The hiqhest risk would,
therefore, occur using the exposure concentrations from year o.
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.
Centrfll Tendenda
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
mm and central tendency is shown in Table 8.
Rlsk SUlll1lUR'1 .
Potential exposures to contaminants in the Fourth street ground
water 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 usinq the future well.
Sixteen contaminants were identified as COCs' based on risks
presented by dermal contact, inhalation exposure, and inqestion of
ground water contaminated by the Fourth Street 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 qoal 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 12 in 10,000 (1.2 E-03) and 48 in
100,000 (4.8 E-04) for adults and children, respectively.
The Hazard Indices for both adult and child receptors were above
the EPA qoal of 1.0 for the inqestion and inhalation pathways. The
total Hazard Index representing residential ground water exposure
is 160 (1.6 E+02) for adults and 410 (4.1 E+02) for children.
-------
Table 8
EIpasure AsnmP;- far Reamaab1t ldlnhmp Ewpaue and CadraI TeadeDcy
Dermal ~~J IJIIfSIicm 8Dd J~)gtinQ of Groundwater
Off-site lt8ideat i'uIure Use Scea8rio
Fourth SCnet Site
.,
Jteason-"'" IIA_:......~ CadraI Teadeaq
ElpCJAte
Cbild Adult Cbild Atit
DEItMAL
AlP GIaup~) 1~ 18-10 1~ 18-10
Di1I11q1 MIed (per)'llr) 3SO 350 3SO 350
Van ~ (per 10 year Jia) 6 30 6 ,
.. WtiPt (ta) 15 10 15 10
-
Sadice Ala ~ (em') '7200 20,000 1200 20,000
1Iams~ prt Day (hr/c1ay) 0.2 0.2 0.2 0.2
iiWat~ (l/cIay) 1 I 1 1
- . INGISl'ION
,. GIa1p (yan) 1~ 18-70 1~ 18-70
DayI ~- (pet year) 3SO 350 3SO 350"
Ya ~ (per 70 year life) 6 30 6 9
Body Wapt (k8) 15 .. 70 15 10
IDiab Rare (lJday) 1 2 0.1 1.4
INHALATION
Aao Gsaap (yeuI) '
1~ 18-70 1~ 18-10
D.p BJpoeed (per year) 3SO "350 350 3SO
Y..~ (per 10 year life) 6 30 6 9
Body Wtigbt (k&) 15 10 15 70
IIdab Bate (d/day) .5 15 5 15
Vol"';"';"" PICIot qJaI) 0.5 0.5 o.s 0.5
n.E: H~\TA8UNIiCS-TIILFS
-------
'.
Table 9
Risk &"""&"-1 tar GrouadwaRr Exposure
Faarda Street Site
- ....
PWLWtV Child Adult
DerD8I 1.1&05 3.0E-G5
Omcer Risk .
I..-1tdW. 1.7&04 5.3:&04
1J14aa 3.C)&04 6.3:&04
TG8IIIUsk 4.8604 1.m03
DenalI 1.3501 3.1E01
Bazanl'JDcIs (HI) ........... 6.25+00 3.8E+OO
JqesPaa 4.0E+02 1.&+02
Teal m 4.1E+02 1.&+02
fILQ H.~7\FDIAIJI'ABU!S\B:S-TIL.FS
-------
Results of the risk calculations indicated that adults and children
are at risk from exposure to the contamination in the ground water
for potential carcinoqenic and toxic effects.
A summary of the risks calculated usinq averaqe exposure factors is
presented in Table 10. Althouqh 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 inqestion
pathway, the chanqes were not siqnificant enouqh to chanqe the
conclusions of this assessment. The total cancer risks from
residential ground water exposure were reduced to 31 in 100,000 and
39 in 100,000 for adults and children, respectively. The total
Hazard Index representinq ground water exposure was reduced to 37
for adults and 290 for children.
site-specific maximum contaminant levels were compared against the
drinking water Maximum contaminant Levels (MCLs) in Table 11.
Since the ground water can potentially be used as a future drinkinq
water source, MCLs would be considered ARARs (Applicable or
Relevant and Appropriate Regulations) for the site. As part of the
modelling effort, the estimated time for contaminants to attain
MCLs throuqh natural attenuation was calculated. These
calculations were made assuming that the surface contamination was
removed from the site. The MCLs were exceeded for two metals
including barium and manganese. Barium is expected to reaCh the
MCL level by year 20 but is not expected to reach an acceptable
health risk level in the next 150 years, based on computer modeling
performed as part of the RI, assuming natural attenuation occurs.
Manqanese is not expected to reach the MCL level or an acceptable
health risk level in the next 150 years.
The MCLs were exceeded by five organics including benzene,
chlorobenzene, 1,2-dichloroethane, trichloroethane, and vinyl
chloride. Benzene, 1,2-dichloroethane and vinyl chloride were also
major contributors to the cancer risks calculated for the exposure
pathways. Chlorobenzene contributed siqnificantly to the overall
non-cancer risk. Based on ground water modeling, benzene is
expected to reach the MCL level by year 160. 1,2-Dichloroethane is
expected to reach the MCL level by year 105. Trichloroethane is
expected to reach the MCL level by year 45.' vinyl chloride is
expected to reach the MCL level by year 135. Chlorobenzene is
expected to reach the MCL level by year 60. Benzene,
trichloroethane, chlorobenzene, vinyl chloride and '1,2-
dichloroethane will take more than 150 years to achieve an
acceptable concentration from a human health risk standpoint.
contaminants in the ground water 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.
- ._- - -.-
-------
Table 10
Risk Summary for Groundwater Exposure
Averap ~ Factors
Fourth Street Site
Pathway . Child Aclult
Derm8I 1.1&05 9.5S06
CaDc:er B1* ,...htInn 1.7S04 1.6504
"'ilslIoa 2.1E04 1.4&04
To8aI.. 3.9&04 3.1&04
DemaII I.3E-Ol 1.2&01
Hazard Inc1el (BJ) ,........... 6.28+00 1.21+00 .
11 '''m 2.8B+02 3.6+01 "OJ
.,,"
Ta8Im 2.91$+02 3~7I+01' .~...
'.. .
..' .
<:.;: ..
. . 0" ',.:' :. ': ~ ' :
, .,0" ."
. . :'~:' :':". ,}",>:('f.:.;;.[.?-"~.:y,.. )t\'.
," . . .
. . . '.~. ~ ~'.
'.
'. .:: .~.,: ".~:' ...> :~'.".
. . ."',
," '.' .,.
,. .
.~
. .
. .'
. .
06 "I .'
. .. ..
..
. .
. '.
. :\,'
. . .
. : r..
. "". :. ..' .
. ":;""":, ::.. .
fIL2: H.~'CI'"..~'IIL.FS
-------
Table 11
Fourth Street Site
CGmparison of Conbaminsmt ~~ (MCL)
With DriDkiD& Water MPmvm Qpdmnmsmt LeteIs
Maximum
MocJeIIed MCLs MCL ExcursioD
C..'Ai,,:-nt of Camera ConeadtUon maIL
D1J/L
CARCINOGENS
Aldrin 1.73E-05 NA NA
Anaic 3.30:603 5B-02 -
h- 1.0m0l 5B.()3 ./
BelyDium O.OOE+OO 4&Q3 -
CIlordaDe 3.46E.05 NA NA
CIloroform 1.73:603 1:&01 -
1.4-Dicb10r0be:m:eDe 2.26B02 7.5&02 -
1,2-Dicbloroetbme 2.6OE-02 5B.()3 ./
HcpCIcblor S.21B.os 4E-04 -
Trichlorodbeae 6.93:&03 5B.()3 ./
Vmyl C1l9ride 2.26:&02 2E-03 .I
NON..cARClNOGENS
AccaaphtbcDo 6.48B02 NA NA
Barium 2. 14E+OO 2E+OO ./
Cadmium ND 5B.()3 ND
Qlorobem.eDe 1.83B-Ol IE-()! ./
1,2-DichloI'A~~ 7.60:&01 6:&01 -
Cis 1.2-DichloroetbeDe 6.48:&01 7E.()2 -
It:ad O.OOE+OO 1.5&02 -
Manganese 3. 12E+Ol SE.()2 "
Men:my 7.20&04 2E-03 -
Nickel O.OOE+OO mol -
Se1a1ium O.OOE+OO SE02 -
NA = MCL DOt prnmnIgptwI for Ibis c:ont-mimmt
- = MaYin'RJI'II CCI1CCDtratioD cIid DOt exceed the MCL.
.t == Mmmmn ~tatiCD excecdecJ the MCL.
ND = CcD:a1tration for cadmium was DOt detamiDed IiDce I11IaboJato1y data for the becboc:k weUa WIll ft!iectecL
-------
Uncertillnties Ass~d with 1M HUIIUI1I Hefllth RIsk CtIlculatlons
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 Fourth Street 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 fram 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.
The analytical data for cadmium in the Fourth street bedrock wells
was rejected, therefore, concentrations were not available to
evaluate the . risk from this contaminant.
Bstimation or Exposure Point Concentrations
The ground water modelinq utilized to estimate the exposure point
concentration is discussed in RI. The COCs which were not modeled
were evaluated by factoring the modeling results.
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 or Tozicltv ana Associatea Constants
The estimation of potential human health impacts due to exposure to
site-related contamination utilizes various toxicity constants
derived.by.theEPA.or.appt'oved by EPA for use in human health risk
-------
assessments. These constants are developed based on information
derived from direct exposure (animal) or human epidemioloqical
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
the protection of human health.
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 evaluation of
these contaminants they have been grouped with similar chemicals
and are evaluated usinq toxicity factors from contaminants. within
the group. The contaminants grouped in this. assessment are ketones
which include 2-butanone, 2-hexanone, acetone, and 4-methyl-2-
pentanone.
ExDosure ASSumDtioDS
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:
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 averaq~ factors affected the
risk calculations for adult exposure in all three pathways since
the exposure time was reduced to nine years. Exposure throuqh
inqestion of ground water was also affected since the inqestion
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 unchanqed
durinq the nine year exposure period.
Use of the central tendency factors decreased the calculated risk,
but did not siqnificantly affect the status of the COCs.
Risk Characterization
A number of assumptions were also made in estimatinq the outcome of
potential human exposures to site-related compounds. carcinoqens
in combination are presumed to exert their effect in an additive
fashion, whereas sYnerqism or antaqonism may be present in some
cases. Non-carcinoqens are also presumed to act in an additive
fashion; however, this approach does not take into consideration
that different contaminants target different orqans and orqan
systems. Particularly sensitive populations or individuals may
exist, which may not become obvious until after exposure.
Assumptions reqardinq exposure are often very conservative.
Uncertainties enterinq into the analysis from the initial measure-
ment of dose and animal weiqht in the first lab study to the
interpretation of lab results to extrapolation between species to
the modelinq of environmental dispersion, as well as other issues
have a compounding (multiplicative) effect on the final uncertainty
of the risk estimate.
Effects seen at bigh 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 Ecoloqical Risk Assessment (ERA) is an inteqral part of the
RI/FS of the Fourth street site. The purpose of the ERA is to
determine current and/or potential baseline impacts on ecoloqical
receptors that are attributable to toxicoloqical stress from the
unremediated Fourth street 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;
As~essment of exposure using ecological and toxicological
stressor components; and
Integration of all above-noted components for ecological risk
est~ation and description of sources of uncertainty.
TozicaD~ S~r.ssors
Concentrations of seven (7) organic and eight (8) inorganic COCs
were predicted for surface water in the North Canadian River
adjacent to the Fourth street site from ground water inflow.
Further model predictions were used to estimate contaminant
concentrations in river-borne suspended s~diment 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 wors~-case
scenario.
CODceDtual Bcoloaica1 H04e1
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,
.
uptake by upper food chain (piscivorus) vertebrates from lower
food chain vertebrates and invertebrates.
-------
Table 12
Predicted Conl-ad.a8iom of ContPDlllllnk
of CaDc:em for tile North Qmadian River
. Dear tile Fourth Street Site
PrecIided ~OD by Media EsthnSll~
(;(hk'AmIlllllnf of Coac:em Arriftl 'I'iDIi
SurfIM:e IDterstitiai Suspended (Years)
water waW So6~
(uaIL) (uaIL) (ugIKg)
::0i:$;~~~f>1}Sti;~:~h::t>:;( :,:;,:.:V~:~~;~~:;~, :::(~:~ :t(~/;~j:~~~!~~~~:~~\~~:~;, 1~i1(.j:~rt:~~~h~,:;t1~&~~t;:,:: :~~tf~i:;'~F:i;;i: ::::;~~:!.::::~t::>.' ;:::X ::~~:.:~:~;:,~>~~~(:~ ':,;::~:YT:::: ;:,
Vmyl Qloride 6.50:&02 6.5OE.02 0 115
1,2-DicIJlotooefh- 6.90:&02 6.90&02 0 115
Trich10r0etbaDe UIOE43 1.00E-03 0 115
p,.,n- 1.S7E01 1.S'7E-Ol 0 115
QlornI-t- - 3.50E-Ol 3.50&01 0 115
1.4-Dic:hIorobeazmo 5.70:&02 5.7OE.02 0 115
bis(2-chloroelhy1)etha' 3.00S03 3.00E-03 0 115
,:~t~;~f' ::'~4::::::'=:;..,::~::;~?~.'::~::}~{:::?i:':;.:'r:::: "':;~::?Yt\:10:~~I~:~~i~;: '~[,:,~}:~;:~::~:BltS:~\;~2r~1 :~,:~:::;:~:r;~~::~::~~;::,I:;~:~;<':;);:;;': ' ..... ;
::.',;::':~;:: ::'\',:": :~,\ ::~ <,:' ::~'<: "
-
AneDic 3.93E+OO 3.93E+OO 7.86E+Ol 1250
Barium 1.64E+02 1.64E+02 0 115
Bayllium 2.00E-m 2.00~ 5.80E-m 2000
Cadmium 3.00S03 3.00E03 1.20E~ 1150
Cuomium 9.21E'()1 9.21&01 6.90E+OO 115
Lead 2.68E+OO 2.68E+OO 7.06E+Ol 15000
Nickel 3.40&02 3.40&02 3.73E.02 2800
Vanadium 7.67E+OO 7.67E+OO 1.000+Ol 900
I. From Qapter 4.0 of this report.
2. AsIA~ eqwd to surface wab:I' c:ooceatra1icm OOo.lIl...dm ~ma
s. ~ by tho equaDoa:
Coac. ~..d Solids = Cone. SUrface W.. x distn~ coefticieat (Kd)
-------
Generally, toxicants are translocated throughout the ecosystem by
the specified pathways where they become available to flo~a 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, phytoplankton (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 pisci vorous fish (Largemouth
Bass). contaminant uptake routes for each ecological class are
summarized in Table 13.
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 cae 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 9f 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).
- - - + - -- - - --
------- _'__-4
-------
Table 13
GeaenI O...hIJtI...nt UpCake 1taates
CaaI:epIuaI EeoJoeieaI Model
~ltiskA51I!--
Fourda Skeet SIt
'.."
~-.f""" ~'i:...,uJatJ9n
~"'a- Sarf8ce ~ SIBpended Vecetatiaa. Iaftrtebrate I1sh
Wiler Water Solids
." .,. ",,~...,.,. .. ,=""".~.. '0 ..' )~.. .t.~1'~~~~~~ ;o,o~~~~@~&~~ ~.~..:~~,;jt'o.': fl~:~~:P~t:f :~i:,~:1.~~;~'~ ;'~.: ,;~ ~)~,:, '10. '.::~'~'~
~....::\ ~ at."'. x:.: .::--.~YV..'~~'.,,-, ~K-~i:#. :~~\~!~~~t5\f~;:; C!:~; ~~:;:::~;~: :::::~~g'~ ':~{~ .:,,~ :>,~':i
~.,. ,.(. "0- . .°0.. ,.':>:-;.: ~:~:;:~~:~:!:~ i~;~~1~." ..,.;.~z~~:..~~
'~ . o. ....-.. .. .. ...-. ~': ;-0<.:
~;'i':. .. " " " "
..
(FII1ieI4 JetiaIDw) .' '.
PUWxo', ..,.' " " "
~ .~ BIll)'
-------
Table 14
TCJJI&d Doses and Huard QuoIIeab
'or die Aqade QM'Gn Food Web ~
Fcath Street Site
..
0'\
......... ,..........
C~~_. ~ <:'1 ! ....... . DIet ,.... c~w a 1<1.& ,..,..,
.,c-.. "" ......~- u. ~ ...... &.rei ClaD-
. F8It (If/III) ...., 0.1 """" ti8It
VI II II v-n 1-15 .... V""" ,
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I~ 4.ezB.GS 2.ID64D 0 1.7SC12 2.Om02 0 3.1ZB411 1.41s.04 2JIOB+04 4.21&G1
~ 2.2AHJ 1.2&01 0 1.23&04 1.35BO:t 0 1.4'1B4S, 3.2AJ1.OS 2.21B+CM 1.43s.4W
..... 6.'DB4D 2.18+01 0 8MB01 S.3OB+GO O' . 538B+CIO I.IISGI 4.418+03 169&0$
0iIi...,t,...., 41'" 1MB'" P.16B+01 0 1.138+48 IMB+4I& 0 1.%78+01 2.808+01 1.418+01 1.99£.Q1
I.~ 6.42&01 8A10601 0 1.04&Ctl 1.11&01 0 8.'7SBCJ1 1.93BC 6.228+01 3.10&0$
~ 2JIOACM 1.10B01 0 4.GB04 4.'" 0 SAI- 1.19Ji.04 1.648+04 UI~
Armo 1.268'" I.'" 1.56BiOi l.oaB+GJ I"'" f.2IB+OII 1.218+03 2MB+Ol S.3OB+01 s.ozs.cn
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..,... SJII801 S.8G1 lAmC11 1.5G01 S.-cr1 U4BCM 1.I4BOi 4.G65CIJ 1"+01 2.71s.04
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NJcbI '-8+aD' '-8+GD." ;: 6.9J&Ol-: 2ID+GD~ ;"..$.10&01:, 1.9I&CD U31+GJ 6.J9B.01 5.3OB+Ol 1.30&03
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,,' ..r;~~...;";;:f..::'- .;:)
TCIIII ..... QJIIIIIIj .:. .,, " '.98SGI
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"I-"''''''''''~ 1 .1.1",........11.1 ''''.1_...:1 "DIJ,""""~ID.'
.. 1-""IRk~""'4Iaaa ... ".."'''''''~IO.,
to 8I8Doh J. 1 "jo...lIn-,,-t 1 ""1 It t ...... . . .~..
.. ~ ( ..,jIoo-'''- .... a""""""''''. -...,....... a"'""",.
.. .....,...... ~1I.
-------
T8IIIe 15
Taddt1 Dales 8Dd""", Q.I6;.'"
far ... AqaItIc l'IIcIwiN l'ocidW~ ~ :,
.. raartla.~",.~:-, .;.'..
, .
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15. ... ..,..
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6S&4U 1.61&02 ,UIHZ 1.I4BGI
'6JMM1 2.07&G& 6.25M1 . 1.31&01 '
5.crma1 135801 UISGJ 1.41&04
2.S4B+4IO 5_'" ' 1.131... 1.'73BOI
19JI'" IMI+01 3.3D+CD, 1A11...
9.211'" I..,IBOI 9.311+GO 107&01
UIBC 4.RCD d. ' 13IBC. 5.10B0f
I.UI+CD I.NB+CD " '1.3II+CD' 2.I9B...I
1.39B+CD 2.458+03 " 3.148+03 IMB...I
1."10&01 3A1OHZ ' 2JIO&01 4.42BOJ '
.,.651+410 I_+GO I 9ASB+GO 2mB01
1.S'7B+01 2.8+01 4331+01 ' 9.511+GO
1.378+01 1.058...1 2.118+01 4.-+GO
1.1.+410 5.10601 . 1.61B+GO UIHZ
U2B+01 1.ISB+01 ".6'78+01 1.."'1
...
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-------
SummarY or Pre4icte4 Bcoloaical Risk
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 COCs
is provided in Table 16. .
sources or 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 'Driori decision to weight the
evaluation process qualitatively toward higher probability of a
type 1 error instead of a type 2 error. uncertainties and
assumptions present in this evaluation included:
.
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/L caCOs
and total metals analyses;
.
contributory risk from background concentrations of the
toxicant stressors was not removed from the overall risk
summary ;
.
Time frame constraints for the predicted arrival of
contaminants were not considered and maximum contaminant.
concentrations were-used as a worst-case scenario; and,
-------
Table 16
Summary of Potmtill Aeufe IDd CbroDic
TOIicity ror Each EcoJoabI Campar8ment
For 8be C....1nanh of CoDCeI'D
~ IUS MIl J-.ent
Faurtb Street Ste .
~I Camputmeat PoteatiaI TGIIcIV
AcuIe Oaro*
'F~-iiil~tJfb"""'''<''~''~':''A' '''''''':'s'Y'':~',~f 's.~.'''':~ ":'.~:' :~":;~"'~~>'''''<'x.!> ,~~::::..;:.:~~:~. ~.: '..=::~~:>~.
:n~'.., ,If, ...' . .'. .::~.~..~.,...;..:.~~:~:~:~...., ~:..:-:;:';::~:.: N.::~~~'~::",,::::;f~:~~.~:. :-s~.~~:.... ~.:. ~'(.:;:::.~;~:
Malt SaI8itiw Speda' _I .
-
. ':-"'..:.:W';~'~~'. i8tf~... :..(~~~'~. . .~""... ,},;........ ":.!'.",,' ... :.- °0 ~'~~~) --,::;.;".~":"::~ J~;~~~2~~;:~~~~~~ r:'~; ~:~~;:'~:"A~' :::i;:::~~~
. I0Il Y. .,. ... . ....(.:~ ~,..:: .:}~1:,~.$.~ ...,,=!;,y...... ~1-.':'
.. '''. ,..,.... ,0 "". :0' ... .., . -0" ,". .o'~, ," ...:,":\ "'..::.. «,...,>~)~-,:-";.< .:.'~
a- AJpt1 - V_Ii..
W.. MiIfaiP - V_II~
;~~,:.: ~'.~;:~?':. "~:,;~\{~~:,:,~~,~::':S~:"~,}~~::~~:;:}'':.\:.:;~1 :. ~ ~.:'~~;J(:i;'~~-=:':~~~~~ . ..'0 ':.$.~':i': /ff::~;~y~~
..;..1': '.
').:.' ,:.".. ...::. .". .."'\.-. :.~ .~'.....'V,,-.<
Wiler"'. V~.... . V-Au.,.
~~~~i'~'2~;>';.:f;~::":/:':~'1..~.'~'''} $ ~':":~ ~;'Ai;~'*7.~r:"f.~::.' .... . ,:;
~:.~ ~;~~'_:-~". -: ,<~:tt:"~ -..."...
'. ... .'. .~ '. " "
F'" Miaaow (cfirrdJ - .. -
Patbe8I MDmaw (via focxI d8Ja1 - -
Patbe8I MiaaDw 0'"nl-m IIIzaId) - -
La..-- .6.. (dhtd'f '. .." , .:. ..
- "."- .-
1M.- -4" (via food d»iA1 .. .' ,
- -
1-.- ..tL .. (r'o.-.J.t;ye haad) - .. .-
...,. -
L -110 ID1icic, predicIed
:L .. Table 5-15
s. .. Table 5-16
4. .. TIbJe 5-17
s. ..Table 5-18
.. .. Table 5-21
1. .. nbIo 5-22
..
, : :' ::,'
,.\ "
-...._--- --~.
-------
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.
VB. REMEDIAL AcrION GOALS
.
Based on the review of the ground water. sampling data from both the
alluvial wells and the bedrock monitoring wells at 'the FSR and the
DER sites, EPA has determined the alluvial aquifer and 'the upper
portion of the Garber-Wellington (bedrock) aquifer to be a Class
III aquifer. Contaminants of concern detected in the alluvial
wells include arsenic, benzene, 1,4-dichlorobenzene, 1,2-
dichloroethane, trichloroethene, vinyl chloride, barium,
chlorobenzene, 1, 2-Dichlorobenzene, and manganese. Contaminants of
concern detected in the upper portion of the Garber-Wellington
(bedrock) aquifer include arsenic, benzene, chloroform, 1,4-
dichlorobenzene, 1,2-dichloroethane, trichloroethene, vinyl
chloride, acenaphthene, barium, chlorobenzene, 1,2-dichlorobenzene,
cis-1, 2-dichloroe'thene, and manganese. Concentrations of these
contaminants exceed the Maximum Concentration Limits (MCLs) and
pose a 12 in 10,000 excess cancer risk to adults that may use these
zones as a drinking water supply.
To be classified as a Class III aquifer (~nes for Ground-
Water -Classification under the EPA Ground-Water Protection
strateav. 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 TOS in the alluvial aquifer were
10,900 ppm and 61,000 ppm, respectively; and in the upper portion
of the Garber-Wellington (bedrock) aquifer the TOS were 27,500 ppm
and 71,000 ppm, respectively, for the wells installed at the FSR
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 is
classified as a Class IIA aquifer);
Ensure that 'the North Canadian River is not impacted by
contaminants from the site.
2)
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
qoals (i.e., below risk-based levels and potential ARARs). See
Table 4. Therefore, the qoals applicable to the contaminated
qround water are the Chemical-Specific ARARs identified for the
upper Garber-Wellinqton (bedrock) aquifer and the health based
levels for COCs necessary for protection of human health and the
environment. .
Table 17 provides a list of the standards that the potential
remedial action technoloqies must achieve if the qround water is
used as a public drinkinq water source. These standards are
applicable to the upper Garber-Wellinqton aquifer at a down-
qradient well located at the site boundary and at a depth of 60
feet. .
Althouqh contaminants in the alluvial aquifer and the upper portion
of the Garber-Wellinqton aquifer are, above MCLs for several
chemicals, restoration is not warranted since the subj ect portions
of the qround water is cateqorized as a Class ,XIX aquifer. Based
on the classification of these aquifers, no further action would be
required. However, there is no confininq "aquitard" between the
upper and lower water bearinq zones and there is still concern that
downward miqration of contaminants to a deeper useable zone could
occur.
Because the alluvial and upper portion of the Garber-Wellinqton
aquifers are Class XXX aquifers, these qoals are not applicable.
VIIL DESCRIYl'ION OF ALTERNATIVES
A Feasibility study was conducted to develop and evaluate remedial
alternatives for the FSR site for the GOU. Remedial alternatives
were assembled from applicable remedial technoloqy process options
and were initially evaluated for effectiveness, implementability,
and cost based on enqineerinq judqement. 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.
Remedlal Action Alte17Ultives
Four remedial alternatives were initially considered for qround
water remedial action in the Feasibility study for the Fourth
street site. These alternatives are: 1) No Action, 2) Limited
Action, 3) Precipitation of Metals and Activated Carbon Treatment
of orqanic Contaminants, and 4) Precipitation of Metals and
Bioloqical Treatment of Orqanics. Durinq the initial development
of these alternatives, Alternative 4 was considered inappropriate
and was eliminated. The co~t of Alternative 4 was siqnificantly
hiqher than Alternative 3, yet it did not provide an additional
level of -risk -reduction.
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Table 17
Remedial Action Goals
ether .
Anllyte
Ar88nIc .
BarUn *
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The following alternatives to address
contamination at the FSR site were evaluated:
the
ground
water
1.
_0 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 al ternati ves. 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.
Limite4 Action
Maior ComDonents of the Limite4 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
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 is not feasible 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 installation of additional deeper
monitoring wells further down-gradient will allow the EPA to ensure
that contaminants 'do not migrate deeper, or to a receptor point
offsite, and determine if an offsite source of contamination
exists. Modelling 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 reduce these
contaminant levels over time. Natural attenuation relies on the
ground water's natural ability to lower the contaminant
concentrations over time through pbysical, 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
obj ect:i ve~.-
_. - _.
- - ----..
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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 site would also be re-evaluated
every five years to determine if further actions need to be taken
with regard to the ground water. If the ground water monitoring
indicates that the lower Garber-Wellington aquifer is becoming
contaminated by site contaminants, or the lateral spread of
contaminants is occurring, 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 aiternative 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 1) 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 componen1:s: 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
Main~enance Costs: $74,880; Total Present Net Worth: $1,463,056.
%norqanic Precipi1:a1:ion and Ac1:iva1:e4 carbon ~r..ta8D1: for
orqanic contaminants
Ma;or comDonen1:s of 1:he Remedial Al1:ernative. 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.
3.
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- ,_..~
compon.nt:s or t:h. ..covery 8yst:_1 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
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 2S years
would be required for contaminant levels to reach the remedial
action goals. Additionally, the contaminant plume. will
theoretically be contained thereby mitigating further off site
migration of the plume. .
component:s or t:h. ~rea=.Dt: 8yst:_: The chemical treatment system
that would be employed under this al ternati ve 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 enh~ced 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 syatem: 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.
components of the Operation and ..int.DaDe. Program: Since the
ground water recovery and treatment system will require
approximately 1 year to install and 2S 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
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(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.
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 RAGs). 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.
IX. 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 CrItma
The nine criteria used in evaluating all of the alternatives are as
follows:
a) Threshold Criteria
OVerall Protection or Human Health ana the BDvironment 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
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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.
ComDliance with ARARs, or "applicable or relevant and appropriate
requirements", assures that an alternative will meet all related
federal, state, and local requirements.
b) Primarv BaJancinq Criteria
Lona-tera Bffectiveness an4 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
accomplished.
Re4uction of Toxicity. lIobility. or Volume of contaminants throuah
Treatment assesses how effectively an alternative will address the
contamination on 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 Bffectiveness addresses the time it takes for remedy
implementat;.ion. 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.
rmDlementability 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 proj ected long-term operation and
maintenance costs) is considered and compared to the benefit that
will result from implementing the alternative.
r;lModifvino Criteria
Sta1:e 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 AcceD~aDce 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.
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ComptllYltlve Analjsls
This comparative analysis presents an analysis of each alternative
in relation to each other usinq the nine criteria. The analysis is
used to identify the relative advantaqes of one al ternati ve versus
another alternative.
overall Protection of HUman Health an4 the Environment
Alternative 1 does not achieve the remedial action objectives and
does not provide protection to human health and the environment.
Al thouqh 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 bedrock aquifers are Class
III aquifers, they will not be used as water supplies. Ground
water monitorinq will alert EPA to any potential for movement of
site contaminants to a potential drinkinq water aquifer. This
alternative will also provide information about chanqes 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 to the lower Garber-
Wellinqton or impact the river, or if the contaminant levels are
not reduced as expected, continqency measures will be taken to
ensure protection of human health and the environment. Federal
drinkinq water standards would be attained in approximately 60 -
150 years.
Alternative 3 would provide the qreatest protection of human health
and the environment from exposure to contaminants from the site;
however active remediation is not warranted at this time.
comDliance with ABARe
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. Act ion-
specific ARARs are listed. in Table 18. Implementation of
Al ternati ve 3 is expected to achieve the drinkinq water standards,
incl\,1ded in the Safe Drinkinq Water Act, for the contaminated
qround water more quickly than Al ternati ve 1 or 2. Al ternati ves 2
and 3 provide the information necessary to determine achievement of
the qround water ARARs. Alternative 1 would not provide sufficient
information to assess lateral or vertical contaminant miqration.
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-Wellinqton aquifer
as a water supply.
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Table 18
Actl~n Specific ARARs
01
\0
Action Requl.......nt '18""uI8- fOr ,........ AMR Citation
Long-term Groundwater Instalation and maintenance of Site related contaminants detected 40 CFR Part 264
Monitoring prognm groundwater monitoring wells for long-term In groun~r above background levels. . (Subpart F)
monitoring program.
Discharge of Water EstablIshment of treatment stll1dards Discharge of eIIuent to waters o'the 40 CFR Part 122
meeting best available technology, water United 8t.88.
quality 8181dard8 or water quality based
toxicity limits. Establishment of best
management practices tof'educe discharge ."
pollution. May require a pennlt based on
location of receiving waler.
Discharge to P01W Dlscherge of poll..-anta that pass through the. Applcable to IncIINct dl8ctwge of 40 CFR Part 403
. P01W without treatment, Intelfere with the pollu18nt8 to . POTW.
P01W operation, contaminate the P01V/ .
sludge, or endanger the P01W workelS .
.Is prohibited.
.'
Treatment of Contaminated Treatment of hazardous waste In a unit Applcable. to treatment o' hazardous waste 40 CFR Part 264
Groundwater req~l8s applcaUon of certain design and In a unit. Does not Include In-situ
constnlctlon requirements. Standllds are treatment.
applicable to tanks, Impoundmerts, land
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Lona-term Effectiveness and Permanence
Al ternati ve 3 provides the greatest degree. of lonq-term
effectiveness and permanence because the contaminant levels
arereduced more quickly than Al ternati ves 1 or 2. Treatment of the
contaminants present in the recovered ground water also provides a
greater degree of lonq-term effectiveness and permanence because
the contaminants are either degraded, absorbed, or altered to a
more stable form. Treatment residues associated with the
Al ternati ve 3 are manaqeable and will be disposed in a manner that
minimizes the lonq-term potential for cross media impacts.
However, the success of Al ternati ve 3 at removinq the contamination
from the alluvial and the upper portion of the Garber-Wellinqton
aquifers is highly questionable since A) there is a possibility of
an offsite 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, althouqh
Al ternati ve 3 may reduce contaminant levels in the short term, but
it may not be siqnificantly more effective in the lonq 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 siqnificant reduction in
overall risk.
Alternative 2 can effectively monitor the contaminant
concentrations in the alluvial, and upper and lower Garber-
Wellinqton aquifers. The reduction in concentrations of site
contaminants, upon removal of the surface contamination, is
expected to be permanent. With the source removed, site
contaminants will not leach into the ground water. However, the
permanence of any reduction in risk from overall contamination of
these aquifers is questionable due to the presence of a source of
contamination not attributable to the FSR site.
Reduction of Toxici tv. Hobili tv. or Volume Throuah Treataent
Alternatives 1 and 2 do not provide a reduction in toxicity,
mobility, or volume throuqh 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-
Wellinqton. However, the overall reduction attributable to
Alternative 3 is questionable, because of the presence of
contaminants associated with DNAPLs. The precipitation of
inorqanic contaminants, and the carbon absorption under Al ternati ve
3 is considered an irreversible process, and provides a permanent
reduction in toxicity and mObility. However, the overall reduction
in toxicity may not be siqnificant due to other potential sources
of orqanic contamination in the area.
. .. - -- - ...-.
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Shor~-~.rm Btt.c~iveDes8
The short-term risk associated with Alternative 1 is a continuation
of the risk currently associated with the si~e. :In the short-term,
the risk from contaminated ground water is minimal since use of the
ground water as a drinkinq water source is considered a future use
exposure scenario. OVer the short term, implementation of
Alternatives 2 and 3 would not siqnificantly increase the risk to
the community or site workers. The additional risk associated with
construction of a monitorinq system or a recovery system
(Alternative 3) can be manaqed by application of enqineerinq and
short-term access controls.
Transportation of treatment residues associated with Alternative 3
can potentially cause exposure to the qeneral public and the
environment should a mishap occur durinq transportation. However,
transportation of wastewater treatment residues is a common and
well manaqed practice in the industry and is not expected to cause
a siqnificant increased risk in the short-term. The transportation
of these residues would have to be conducted in compliance with all
applicable requirements of the u.s. Department of Transportation.
:ImplemeDtabili~v
-
Alternative 1 is the easiest to implement. Alternative 2 involves
installation of a ground water monitorinq system which does not
require siqnificant construction activity. Alternative 3 requires
the same elements of Al ternati ve 2 with the addition of a recovery
and treatment system. The treated ground water would be required
to meet comparable permitted discharqe standards (National
Pollutant Discharge Elimination System) in the Clean Water Act.
The construction of a ground water monitoring and/or recovery and
treatment system with operation, monitorinq, 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.
Some of the chemicals detected in the ground water beneath the FSR
site such as dichloroethane, trichloroethane and dichlorobenzene
are associated with DNAPL contamination. Past experience indicates
a hiqh degree of difficulty in remediatinq 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 remediatinq this type of
contamination is questionable.
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.t,<'.
Cost
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
implemented for a significantly reduced cost and provide the
flexibility to continue assessment of ground water contaminant
levels.
state AcceDtance
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.
communitv AcceDtance
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 SELECfED 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 Fourth Street 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 offsite, and determine if an
offsite source of contamination exists.
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.
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.
Routine inspections to ensure that public use of the upper
zone of the Garber-Wellington Aquifer does not occur prior to
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 monitoJ;'ing 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.
.
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
Al ternati ve 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 1:1:1: aquifers. Also, the data obtained
during the investigation stage of the project suggests the
possibility of an offsite, upqradient 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,
a pump and treat alternative (Alternative 3) could be implemented
at a much higher cost, but 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 al ternati ves, EPA believes. that the preferred
remedy will achieve this qoal. :If monitorinq does not indicate a
reduction in the concentration of ground water cont~ination 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.
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. This remedy utilizes permanent
solutions and alternative treatment technologies to the maximum
extent practicable for this site. However,.because treatment of
the "contaminated 'ground water. was not found to be warranted at this
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o
.
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) .
cOD~iDa.Dav a.asur.s:
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 qround water aquifers, and 2) whether the contamination has.
migrated vertically or horizontally.
If during the monitoring, detectable concentrations of site
contaminants. are found in the lower Garber-Wellington monitoring
wells, or if the contaminated portions of the ground water show an
increase of 30 percent 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, BPA 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.
.
.
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.
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Al ternati ve 2 will provide protection to human health and the
environment by allowinq the EPA to monitor the qround water to
confirm contaminant level reductions (as predicted), and ensure
that contamination miqration does not reach a receptor point.
Alternative 1 is not considered appropriate since the "No-Action"
alternative will not allow monitoring of the qround water to
provide protection to human health and the environment.
Since the data suqqests the possibility of an offsite source of
contamination, and the industrialized nature of the adjacent
properties, an investiqation is currently beinq conducted by other
proqrams 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
environment. 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 qranted. The selected
remedy must also be cost-effective and utilize treatment or
resource recovery technoloqies 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 qround water at the FSR
site meet the statutory requirements.
Protection 01 HUllUln Health tmd 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 drinkinq water well was.
installed at the site boundary and within the area of the
contaminant plume. Al ternati ve 2 provides control of this exposure
route by reducinq the likelihood' that a drinkinq water well will be
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
drinkinq water source.
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o
o
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. Thro~gh natural
attenuation, contaminant levels are expected to be within the
remedial action obj ecti ves 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.
ComplUmce wUh AR.4Rs
The ground water at the exposure point is not currently us~d as a
public drinking water source due to the high total dissolved solids
from pa-st 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-Effectlveness
The selected remedy is considered cost effective since it is much
less expensive than Al ternati ve 3, yet provides adequate protection
to human health and the environment. The "No-Action" alternative
is not considered acceptable since it provides no protection to
human health and the environment.
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Utlll%atlma 01 P.mummt SolutIons iIIId Treatment or RestJlI1ft R6ctwe" Technologies to 1M
Mtalmum Extent PractIcaIJk .
Alternative 2 is not considered permanent because t:his alternative
will not actively remove 'the contamination within 'the aquifer and
restore 'the ground water to KCLs. 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 offsite source of contamination exists, and that
the classification of the aquifer as a Class III zone remains
appropriate.
Alternative 2 18 considered permanent in the sense that 'the five-
year review will allow ground water sampling and analysis, and
modelling 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 lor Treatmmt as a Principal Element
Treatment is not a principal element of al ternati ve 2; however, it
.is considered the best alternative considering 'the specific
conditions and circumstances at the site.
XIL 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 FSR site, has been included.
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