PB96-964205
EPA/ROD/R06-96/103
May 1997
EPA Superfund
Record of Decision:
Vertac Superfund Site,
Operable Unit 3, Jacksonville, AR
9/17/1996
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RECORD OF DECISION
VERTAC SUPERFUND SITE
JACKSONVILLE, ARKANSAS
OPERABLE UNIT #3
GROUND WATER
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
SEPTEMBER 1996
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DECLARATION
VERTAC SUPERFUND SITE
RECORD OF DECISION
OPERABLE UNIT #3
SEPTEMBER 1996
SITE NAME AND LOCATION
Vertac Incorporated
Jacksonville, Arkansas
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action
for Operable Unit 3 (OU3), Ground tfater, for the Vertac,
Incorporated, site in Jacksonville, Arkansas, which was chosen in
accordance with the Comprehensive Environmental Response,
Compensation and Liability Act (CERCLA), 42 U.S.C. § 9601 et
seq. f and, to the extent practicable, the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP), 40 CFR
Part 300. This decision is based on the administrative record
for this site.
The State of Arkansas fully supports this remedy, and a
concurrence letter from the Arkansas Department of Pollution
Control and Ecology (ADPC&E) can be found in Appendix C. ??
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from
this site, if not addressed by implementing the response action
selected in this Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare,
or the environment.
DESCRIPTION OF THE SELECTED REMEDY
There are six operable units for the Vertac site. As stated
at length in the text of the ROD and described more fully below,
the Environmental Protection Agency (EPA) has determined that it
is technically impracticable to address non-aqueous phase liquids
(NAPLs), which constitute the principal threat posed to ground
water found underneath the site. However, EPA has also
determined that currently the ground water in the contaminated
Atoka aquifer is not used as a drinking water source due to
limited yield of this aquifer and the availability of municipal
water supplies, and therefore the reasonably anticipated ground
water use scenario does not include such a future use.
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Therefore, the remedy selected in this ROD for Operable Unit
3 will contain within the site's confines dioxin- and herbicide-
contaminated ground water that constitutes a low level long term
threat, will treat to State of Arkansas water quality standards
the ground water extracted from the site in connection with the
hydraulic containment of the contaminated ground water plume, and
will provide a legal mechanism by which EPA will reevaluate the
remedy selected in five-year intervals from the date the remedy
is initiated. These five-year periodic reviews will permit EPA
to assess any new technologies that may emerge in the future and
determine the appropriateness of amending this ROD at that time
to utilize such new technologies that would permit EPA to treat
the principal threat NAPLs.
The Vertac site can be divided roughly into two 100 acre
tracts. The northern half was never a part of the industrial
operations at Vertac, and therefor^ -toes not contain ground water
contamination. Additionally, ground water from contaminated
ureas to the south does not flow northward. The southern portion
of the site was the location of most manufacturing and waste
disposal areas during the site's active operational life.
Therefore, the southern portion of the site is heavily
contaminated. In addition, the southern portion of the site
contains three burial areas, two of which have been and continue
to be a confirmed source of ground water contamination, and the
third of which is suspected of being a ground water contamination
source. Those three disposal areas are the result of litigation
described below.
In 1980 EPA and ADPC&E jointly filed suit in the United
States District Court for the Eastern District of Arkansas
against Vertac and Hercules. A Consent Decree entered into by
EPA, ADPC&E, Vertac, and Hercules in January 1982 required that
an independent consultant assess the conditions of on-site wastes
and develop a proposed disposal method for the wastes. The
proposal, called the "Vertac Remedy,' was deemed by EPA to be
unsatisfactory. The Court decided in favor of the proposed
remedy, which was implemented in the summer of 1984 and completed
in July 1986. As part of the remedy, the Vertac plant cooling
water pond was closed and sediment from this unit was removed and
placed in an above-ground clay lined vault constructed adjacent
to where the cooling pond had been located. The Reasor-Hill and
Hercules/Transvaal Landfills were capped, and a french drain and
leachate collection system were installed around the burial
(landfill) areas. Those two landfills are not lined and are
known to be sources of ground water contamination. Ground water
monitoring wells were also installed, and a ground water
monitoring program was initiated.
Under the remedy EPA is concurrently selecting for OU2,
soils within the entire site with dioxin concentrations in excess
of 5 parts per billion (ppb) will be excavated and consolidated
within an on-site hazardous waste landfill designed and operated
in compliance with Subtitle C of the Resource Conservation and
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Recovery Act (RCRA), 42 U.S.C. § 6901 et sea.. so that the
greatest area of the site may be returned to
commercial/industrial use. Excavated areas will be backfilled
with clean soil, graded, and a vegetative cover established.
After remediation at the 5 ppb action level, the average dioxin
soil concentration site-wide will be at or below 1 ppb. However,
the areas subject to the Vertac Remedy located on the southern
portion of the site will remain in place due to the Court's
order. These areas, the 2 burial grounds, Mount Vertac, the
French drain and the wastewater treatment plant, will be
restricted, with access only allowed to on-site maintenance
workers. Additional restricted areas may be needed, for example,
for the current and future monitoring and extraction wells which
are or will be located in the southern portion of the site to
prevent ingress by trespassers and allow access for operation and
maintenance activities.
The remedy for Operable Unit j will reaaxt in the
restoration of ground water quality in some areas of the site and
on-site containment of contaminated ground water in areas where
restoration is not practicable due to the presence of substantial
volumes of NAPLs in fractured bedrock. Due to the technical
impracticability of treating the NAPLs, the ROD for Operable Unit
3 invokes a waiver from meeting drinkir.~ water standards, known
as maximum concentration levels (MCLs) under the Safe Drinking
Water Act (SDWA), 42 U.S.C. § 300f e£ sea.. and found at 40 CFR §
141.11-26, for these latter areas, which include the northern
portion of the central process area, and areas where wastes were
buried on-site as part of past operations and subject to the 1984
Court-ordered remedy. Ground water containment operations
implemented under Operable Unit 3 will be necessary for the
foreseeable future.
Ground water beneath much of the southern half of the site
is contaminated with dissolved-phase site compounds. Ground
water beneath the eastern part of '.: cen^ril process area moves
eastward, whereas ground water beneath the western part of the
central process area has a westward component. The remedy for
Operable Unit 3 involves the installation of ground water
extraction wells in key areas of the site to reverse the eastward
ground water gradient and use of the existing French drain, which
was installed as a result of a 1984 Court-ordered remedy, to
prevent off-site migration of contaminated ground water to the
west. The extraction wells are expected to retract the eastern
component of the waste plume, which if left unchecked, could move
off-site to a point of discharge (e.g., any creek hydraulically
connected to the aquifer or a similarly connected domestic water
well).
The remedy also includes removal of non-aqueous phase
liquids (NAPLs) from an old on-site water supply well in the
central process area into which some wastes were reportedly
dumped by site workers. This well contained a 1 foot thick layer
of light non-aqueous phase liquid, which was the thickest
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occurrence of NAPL observed at the site during the remedial
investigation. In addition to these engineering controls, deed
restrictions will be imposed to assure that no water wells are
installed on-site (other than those associated with containment
efforts) or in an area which could affect containment efforts,
and EPA will discuss with officials of the City of Jacksonville
whether the enactment of specific zoning ordinances prohibiting
such well installation is appropriate.
Finally, because hazardous substances will remain at the
site under this selected remedy, CERCLA Section 121(c), 42 U.S.C.
S 9621(c), requires EPA to reevaluate the remedy selected herein
in five-year intervals following the initiation of the remedy.
Therefore, should a technology emerge in the future that will
provide a practicable means to treat the principal threat NAPLs,
EPA will reassess this remedy and possibly amend this ROD to
^ 'iIre such a treatment technology.
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, except those that are waived for reasons of
technical impracticability, and is cost effective. This remedy
utilizes permanent solutions and alternative treatment
technologies, to the maximum extent practicable, and satisfies
the statutory preference for remedies that employ containment
where treatment of principal threats is impracticable but that do
address low level long term threats. However, this remedy does
permit, through the five-year periodic review process, the
possibility that at some future date this ROD may be amended to
utilize a technology that does employ treatment as a principal
element.
As stated above, because this remedy will not result in
removal of all NAPLs from the site, hazardous substances will
remain on a portion of the site. Pursuant to CERCLA Section
121(c), 42 U.S.C. § 9621(c), EPA shall review the remedial action
no less than every five years after initiation of the selected
remedial action to ensure that the remedy continues to provide
adequate protection of human health and the environment and that
permits the incorporation of some future technology that could
practicably address the principal threat NAPLs
Jahej'N.
ReaiJonal dminstrator
SEP 1 719S6
Date
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RECORD OF DECISION
CONCURRENCE DOCUMENTATION
FOR THE
VERTAC SDPERFUND SITE
OPERABLE UNIT #3
JACKSONVILLE, ARKANSAS
Philip Dellinger
Site Remediai-^Project Manager
6SFr
John Z_:jdale
Senior Attorney, 6SF-DL
Wren stenger, )2nief
Arkansas/Oklahoma Section, 6SF-AO
filliarii K. Honker, Chief
Superfund AR/OI^IX Branch, 6SF-A
\
Mark Peycke, Chief
Superfund Litigation and Enforcement Branch, 6SF-DL
Myron 0. Knuds6n, Director
Superfund Division, 6SF
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DECISION SUMMARY
FOR THE
VERTAC SUPERFUND SITE
JACKSONVILLE, ARKANSAS
OPERABLE UNIT #3
SEPTEMBER 1996
1.0 SITE LOCATION AND DESCRIPTION
The Vertac Incorporated Superfund Site (the site) is
approximately 193 acres in size, and is located on Marshall Road
in Jacksonville, Pulaski County, Arkansas, as shown in Figure 1.
Jacksonville is about 15 miles northwest of the State Capital,
Little Rock. Approximate.!./ 1,000 residents live within one mile
of the site, with residential areas bordering the entire east and
south sides. The west and northern sides of the site are bounded
by an industrial area and the Little Rock Air Force Base,
respectively.
The site consists of two parcels of land (Parcel 1 and
Parcel 2) that were acquired at different times during plant
operations (Figure 2). Parcel 1 (the southern acreage), which
contains the central process area, is approximately 93 acres and
has been in nearly continuous industrial use since 1948. Parcel
2, which is approximately 100 additional acres to the north, was
purchased by Vertac Chemical Corporation (Vertac) in 1978 but was
never used in the herbicides formulations operation. In 1979,
the 2,4,5-T storage shed was built adjacent to the Regina paint
building to contain empty Vertac 2,4,5-T waste drums. Parcel 2
does not contain production facilities and is currently used by
the United States Environmental Protection Agency (EPA) for drum
storage in newly-constructed warehouse buildings. An incinerator
constructed under the contract to the Arkansas Department of
Pollution Control and Ecology (ADPC&E) to burn drummed waste is
also located in the northern part of Parcel 1.
Topographically, the land has moderate relief, sloping from
about 310 feet above mean sea level (MSL) in the north to
approximately 260 feet near the southwestern corner. The central
process area is located on a south plunging topographic nose
bounded by Rocky Branch Creek on the west and Marshall Road on
the east. Land on the western side of Rocky Branch Creek has not
been used for manufacturing or disposal and is topographically
separated from the central process plant area by the creek. Land
on the eastern side of Marshall Road has not been used for
manufacturing and is geographically separated from the central
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34° 52' 30"-
Little Rock ,
c Air Force Base
SITE
LOCATION
I /srvvN, K !
/tt^LjJ.^ |.!.:|:
Source: U.S. Geotogica! Survey
7.5 Minute Series
CHmstead, AR (1987)
Cabot, AR (1987)
Jacksonville, AR (1987)
McAh-nont, AR(1986)
1248-331 11/1&92
QUADRANGLE LOCATION
SITE LOCATION MAP, VERTAC SITE
JACKSONVILLE, ARKANSAS Figure 1
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Regina Paint
Building
EPA Drum
Product storage V
Building
T Product
Stomga
Formulation*
Building
Paint
Storage
Building
Laboratory
Chemical
Qlaa* and
Inatrumant Shop
.outer. Hwculrt Incorpot.wl. """
MM Map UtttWS (torn Mw by CH,
Legand
Boundary Between
Parcels 1 and 2
>-__. Central Process Area
a Properly Line
Rocky Branch Creek
{J2J221 Buildings and Foundations
-* uuu Railroad
~ * Fence
200 400 600
Seal* In leal
SITE MAP, VERTAC SITE
JACKSONVILLE, ARKANSAS
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process plant area by Marshall Road. Land on the northern part
of the site has not been used for herbicide manufacture and is
generally up slope from the central process plant area.
2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES
2.1 SITE OPERATIONS HISTORY
The first facilities on the site were constructed by the
U.S. Government in the 1930's and 1940's. These facilities were
part of a munitions complex that extended beyond the present site
boundaries. Little is known about the operations that occurred
during that time period. In 1948, the Reasor-Hill Company
purchased the property and converted the operations to
manufacture insecticides such as DDT, aldrin, dieldrin, and
toxaphene. During the 1950's, Reasor-Hill manufactured
herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-
trichlorophenoxyacetic acid (2,4,5,-T), and 2,4,5-
trichlorophenoxypropionic acid (2,4,5,-TP), which is also called
Silvex. Drums of organic material were stacked in an open field
immediately southwest of the production area, and untreated
process water was discharged from the western end of the plant to
Rocky Branch Creek.
Hercules Powder Company, now known as Hercules, Inc.
(Hercules), purchased the Reasor-Hill property and plant in 1961
and continued to manufacture and formulate herbicides. The drums
that were in the open area southwest of the central process area
were buried in what is now referred to as the Reasor-Hill
Landfill. From 1964 to 1968, Hercules produced the herbicide
Agent Orange, a mixture of equal parts of 2,4,5-T and 2,4-D.
Hercules discontinued operations at the site in 1971.
From 1971 to 1976, Hercules leased the plant site to
Transvaal, Inc. (Transvaal), a predecessor company of Vertac.
Transvaal resumed production of 2,4-D and intermittently produced
2,4,5-T. Organic wastes from these manufacturing processes were
stored and then buried by Hercules on the site in what is now
referred to as the North Landfill area. Transvaal purchased the
property and plant from Hercules in 1976. In 1978, Transvaal
underwent a Chapter XI bankruptcy reorganization and ownership of
the site was transferred to the new company, Vertac Chemical
Corporation, which is the present owner.
In 1979, ADPC&E issued an order that required Vertac to
improve its hazardous waste practices, and in 1980 EPA and ADPC&E
jointly filed suit in federal district court against Vertac and
Hercules. A Consent Decree entered into by EPA, ADPC&E, Vertac,
and Hercules in January 1982 required that an independent
consultant assess the conditions of onsite wastes and develop a
proposed disposal method for the wastes. The proposal, called
the "Vertac Remedy", was deemed by EPA to be unsatisfactory. The
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court decided in favor of the proposed remedy, which was
implemented in the summer of 1984 and completed in July 1986. As
part of the remedy, the Vertac plant cooling water pond was
closed, and sediment from this unit was removed and placed in an
above-ground vault. The Reasor-Hill and Hercules/Transvaal
Landfills were capped, and a French drain and leachate collection
system were installed around the burial (landfill) areas. Ground
water monitoring wells were also installed, and a ground water
monitoring program was initiated.
Vertac operated the plant until 1986. On January 31, 1987,
Vertac abandoned the site and declared bankruptcy, leaving
approximately 29,000 drums of 2,4-D and 2,4,5-T wastes. Many of
these drums were corroded and leaking. At that time, EPA
initiated an emergency removal action to stabilize and secure the
site.
In 1988, ADPC&E contracted for the incineration of the
drummed waste, using a $10.7 million combined trust fund and
letter of credit obtained from Vertac during bankruptcy
litigation. A contract for the incineration of the drummed waste
was signed in 1989 between ADPC&E and Vertac Site Contractors
(VSC). VSC is a joint venture of MRK Incineration and Morrison-
Knudsen Environmental Services. In January 1992, ADPC&E approved
the VSC trial burn and production incineration began. Because of
the difficulty in handling the Vertac drummed waste material,
incineration operations took longer than originally anticipated.
In May 1993, the trust fund money had been expended with
approximately 50 percent of the waste destroyed under the State's
contract. In June 1993, EPA took over the incineration operation
and completed the incineration of the D-waste drums in September
1994. EPA contracted for the off-site incineration of the
remaining 3,100 drums of T-waste. Shipments of T-^ste to the
APTUS commercial hazardous waste incineration facility, located
in Coffeyville, Kansas, concluded on March 29, 1996.
On July 16, 1996, the Regional Administrator for EPA Region
6 executed a Non-Time Critical Removal Action Memorandum that
concluded the on-site incinerator support activities associated
with the on-site D-waste incineration, which had concluded on
January 2, 1994. That Action Memorandum authorized the off-site
disposal of 33,000 drums of salts (and the associated pallets)
that were generated during the on-site incineration of D-wastes,
and it authorized the on-site disposal within the RCRA Subtitle C
hazardous waste landfill of both 10,000 shredded pallets used to
store drummed waste materials and of 6,300 drums of incinerator
ash (and their associated pallets). In that Act ion Memorandum,
the Regional Administrator also granted a variance from the RCRA
Land Disposal Restriction (LDR) treatment standard applicable to
dioxin-containing wastes found at 40 CFR § 268.31. Specifically,
the Regional Administrator approved a treatability variance for
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the disposal of dioxin-contaminated wastes within the on-site
RCRA Subtitle C landfill of 5 ppb from the LDR standard of 1 ppb
pursuant to the procedures set out at 40 CFR § 268.44.
Therefore, should the LDR dioxin treatment standard be
applicable to the on-site disposal within the on-site RCRA
Subtitle C hazardous waste landfill if placement within the unit
occurs, the treatment standard is 5 ppb.
Currently, there are no manufacturing operations at the
site. At the time operations were shut down, Vertac "mothballed"
the plant. Mothballing involved flushing process lines and
draining several of the process vessels. Continuing activities
at the site include operation of an on-site water treatment plant
by Hercules under the terms of a 1984 Court-ordered remedy. The
treatment plant processes ground water collected in French drains
constructed downgradient (south and west) of the old waste burial
areas, and surface water runoff collected in a series of drainage
ditches and sumps that surround the central process area. This
treated water was originally piped to the West Wastewater
Treatment Plant (WWTP) owned and operated by the city of
Jacksonville and was discharged into Bayou Meto. As part of
ongoing remedial activities at the site, Hercules has recently
completed the cleaning and regrouting of certain sections of the
sewer lines that run through the site to the WWTP, and as such,
water that was discharged to the sewer interceptor on the site is
now treated and discharged directly into Rocky Branch Creek
(after meeting discharge limits established by ADPC&E).
The Vertac site was added to the National Priorities List
(NPL) of hazardous waste sites in 1982. Once the site was placed
on the NPL, money available from the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980, commonly
called Sup-rfund, 42 U.S.C. § 9601 et se_g., could be used to
investigate and study the problems at the Vertac site and find
ways to correct them to protect the public health and the
environment.
2.2 ENFORCEMENT ACTIVITIES
A Potentially Responsible Party (PRP) search was not
conducted since the Agency knew the identities of former owners,
operators, and some generators of waste at the Vertac site, and
since litigation was already ongoing prior to CERCLA activities.
However, CERCLA Section 104(e) information request letters were
mailed in March 1990, and later to several companies which had
"tolling agreements" with the Vertac Chemical Corporation and/or
Hercules.
The following is a chronology of enforcement activity at the
Vertac site:
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1. Litigation was filed in 1980 under Section 7003 of the
Resource Conservation and Recovery Act (RCRA), 42 U.S.C. §
6973, and other statutes by the United States and the State
of Arkansas against Vertac Chemical Corporation and Hercules
Inc. (the Parties). In January 1982 EPA and the State of
Arkansas entered into a Consent Decree with Vertac Chemical
Corp. and Hercules, Inc., in the litigation for developing a
remedial plan for certain on-site and off-site areas. After
EPA invoked dispute resolution and had a hearing on the
remedy, the Court ordered the implementation of the "Vertac
Remedy" in July 1984 (see Site History for a discussion of
the action taken).
2. In July 1986, pursuant to an agreement between the parties
and entry by the court, Vertac established an Environmental
Trust Fund as part of a bankruptcy agreement. Vertac placed
$6,700,000 in this fund to be used to remediate portions of
the plant. A $4,000,000 letter of credit was later added to
this Trust Fund also for the purpose of future site
remediation. Both EPA and the State of Arkansas had access
to this fund which was later used to incinerate the 29,000
drums of waste left at the site by Vertac.
3. In August 1986, EPA issued a Unilateral Administrative Order
(UAO) pursuant to Sections 104 and 106 of CERCLA, 42 U.S.C.
§§ 9604 and 9606, to all PRP's to require posting of warning
signs and the fencing of portions of the WWTP and certain
areas of Rocky Branch Creek. This work was performed by
Hercules.
4. In January 1987, EPA issued a notice letter to Vertac
Chemical Corp. that required Vertac Chemical Corp. to
continue operation and maintenance of the leachate
collection and treatment system which was established around
old on-site waste burial areas.
5. In June 1988, EPA signed an Administrative Order on Consent
(AOC) pursuant to Section 106 of CERCLA, 42 U.S.C. § 9606,
with Hercules to allow Hercules to implement the fine grid
sampling investigation for specific off-site areas.
6. In September 1988, EPA signed an AOC pursuant to Section 106
of CERCLA, 42 U.S.C. § 9606, with Hercules that required
Hercules to remove approximately 3,000 cubic yards of
dioxin-contaminated soil from residential yards near the
facility.
7. In July 1989, EPA signed an AOC pursuant to Section 106 of
CERCLA, 42 U.S.C. § 9606, with Hercules that required
Hercules to conduct the on-site Remedial
Investigation/Feasibility Study (RI/FS).
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8. In March 1990, EPA sent CERCLA Section 104(e) information
request letters to several companies which had been involved
in business deals with the Vertac Chemical Corp. and
Hercules Inc., including "tolling agreements".
9. In July 1990, EPA sent General Notice letters to the PRP's
regarding the proposed off-site remedial plan and other site
actions.
10. In February 1991, the U.S. District Court for the Eastern
District of Arkansas entered a Consent Decree between the
United States and "Phoenix Parties", which are companies
related to the Vertac Chemical Corp., and which carried on
the remaining business of Vertac under their names after
Vertac abandoned the site. Hercules appealed the entry of
the Consent Decree to the Eighth Circuit Court of Appeals,
which upheld the entry of the Consent Decree in April 1992.
Under the terms of the Consent Decree, the Phoenix Parties
have contributed $1,840,000 to a RCRA Closure Trust Fund,
and will contribute a percentage of pre-tax profits for 12
years, in return for release of liability.
11. Hercules, Inc., had opposed the United States' efforts to
select various CERCLA remedies at Vertac. This opposition
included a motion filed in September 1992 to enforce the
1982 RCRA Consent Decree. The parties were ultimately
unable to resolve their differences regarding this motion.
In June 1992 the District Court entered an order denying
Hercules' motion to enforce the Consent Decree and allowed
EPA to follow CERCLA procedures to select remedies for the
site.
12. The United States added CERCLA Section 107, 42 U.S.C. §
9607, cost recovery claims against Hercules, Dow Chemical
Company, and Uniroyal Chemical Limited of Canada, in a
complaint filed in March, 1992. By order of the trial court
in June 1992, this complaint was administratively closed,
and the claims asserted against Hercules, Dow, and Uniroyal
were consolidated with the existing litigation. Other
parties, including BASF AG, Standard Chlorine, and Velsicol,
have been added to the litigation as third-party defendants.
13. Special notice letters for Remedial Design/Remedial Action
(RD/RA) for the off-site areas were sent to the PRP's in
August 1992. No "good faith" offers were received in
response to the letter. A subsequent special notice letter
was sent in December 1992 to the PRP's after EPA revised the
scope of the remedial work at the off-site areas.
Negotiations regarding this work did not result in an RD/RA
Consent Decree.
8
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14. In June 1993, EPA issued a UAO pursuant to Section 106 of
CERCLA, 42 U.S.C. § 9606, with Hercules to allow Hercules to
implement the Remedial Design and Remedial Action for the
Off-site ROD, which was signed in September 1990.
15. In March 1994, EPA issued another UAO pursuant to Section
106 of CERCLA, 42 U.S.C. § 9606, to Hercules requiring it to
implement the Remedial Design and Remedial Action for the
Operable Unit 1 ROD, which was signed in June 1993.
16. The liability phase of the on-going litigation was completed
in October 1994, when the United States was granted a motion
for summary judgement against Hercules, Inc., holding it
jointly and severally liable to the United States for past
and future response costs incurred at the site. The claims
made by the United States were against Hercules, Inc., Dow
Chemical Company, and Uniroyal under CERCLA Section 107, 42
U.S.C. § 9607, for recovery of costs related to the Vertac
site, including EPA removal costs. The claims against Dow
and Uniroyal were based on tolling agreements that those
companies had with Vt_cac, where they sent raw materials to
Vertac for processing into finished product that was shipped
back to them. These tolling agreements constituted
arrangements for disposal pursuant to CERCLA Section
107(a)(3), 42 U.S.C. § 9607(a)(3). Prior to a liability
phase trial, the United States settled its claims against
Dow through a Consent Decree for $3.5 million. Settlements
were also reached with Velsicol and the United States on
behalf of the Department of Defense.
The only United States claims remaining unresolved after
these settlements were those against Uniroyal. The
liability phase of the trial against Uniroyal was concluded
in November 1993. A jury, sitting both as an advisory jury
and a fact-finding jury, returned a verdict finding Uniroyal
also liable at the site for CERCLA Section 107 costs, but
that its involvement was divisible. To date, the Court has
not entered its order addressing the findings of the jury,
and the cost phase of the trial has not been initiated.
17. Although not specifically enforcement-related, several
separate citizens suits were filed seeking to halt
incineration of the 29,000 drums of dioxin contaminated
still bottom wastes which were stored at the site. They are
as follows:
After the incineration contract was finalized, but before
the first trial burn, came National Toxics Campaign (NTC),
et.al. v. ADPC&Er et. al.f seeking to enjoin the impending
trial burn. After six days of testimony, the trial court
denied a preliminary injunction based on the merits. NTC
subsequently dismissed its lawsuit in federal court.
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Incineration opponents sued again, in State chancery court,
on the morning of the same trial burn approved in federal
court during the NTC litigation. This suit, Ruby Brown and
Sharon Golgan v. ADPC&E, was filed in Pulaski County
Chancery Court. The chancellor denied the temporary
restraining order on the merits after a hearing that day.
After thousands of D-waste drums had been burned, ADPC&E's
director announced that T-waste would be burned after a
limited burn of T-waste so that ambient air and incinerator
stack data could be evaluated for risk considerations. This
announcement brought the lawsuit by the Arkansas Peace
Center (APC) et al., in October 1992. During this
litigation, control of the incineration passed from State to
EPA control, after State funds were exhausted.
The APC litigation resulted in a preliminary injunction (the
March 17, 1993, order mentioned above), a subsequent stay of
that injunction by the Eighth Circuit based on both
jurisdiction and the merits, and eventual dismissal due to
lack of jurisdiction.
After denial of a petition for certiorari to the U.S.
Supreme Court, plaintiffs filed suit again in chancery court
in April 1994. That case was removed to federal court and
eventually dismissed. In the dismissal order, the district
court found that the lawsuit was barred by CERCLA 113(h), 42
U.S.C. § 9613(h), since the lawsuit was clearly designed to
stop incineration. The District Court also found that
dismissal was appropriate based on res judicata, i.e., that
the same case had already been tried.
3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION
A community relations plan for the Vertac site was put in
place in 1983. This plan listed contacts and interested parties
within the federal, state, and local governments, various
organized affiliations, and local citizens. It also established
communication pathways to ensure timely dissemination of
pertinent information about site activities. Extensive community
outreach has been performed in Jacksonville over the years
through the release of information fact sheets, by conducting
frequent open houses and work shops, and through numerous
meetings with local civic groups and media representatives
(newspapers, radio and TV). Reports updating activities at the
site are also distributed to the Mayor, interested civic groups,
and the local media on a weekly basis. A satellite community
relations office was established in Jacksonville in July 1990 to
provide easy access to documents and information, and to provide
a local contact for questions and concerns.
10
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A Technical Assistance Grant (TAG) was awarded by EPA in
1989 to a citizens group called Jacksonville People With Pride
Clean Up Coalition (JPWPCUC). This award was challenged by
citizen groups that had competed for the grant and who alleged
that JPWPCUC was funded by the Potentially Responsible Parties
(PRP's) for Vertac. Upon investigation by EPA, the grant was
annulled after it was determined that the JPWPCUC TAG application
listed their source of matching funds as a bank account shared
with their larger "parent" group, the Jacksonville People With
Pride. This parent group had indeed accepted monetary
contributions from Vertac PRP's, and since these funds were not
distinct from those of JPWPCUC, EPA determined that a possible
conflict of interest could exist, resulting in annulment of the
TAG in December 1991.
TAG availability was again advertised in January 1992, and
the grant was awarded to the Concerned Citizens Coalition (CCC)
in April 1993 after considerable effort by EPA to facilitate
consolidation of four competing citizen groups. The CCC then
solicited several technical groups in order to select a technical
advisor for the TAG. The Environmental Compliance Organization
(ECO) was selected as the technical advisor and actively reviewed
site documents for the community.
EPA's Proposed Plan for addressing ground water at the site
was released to the CCC and the Mayor of Jacksonville at a
meeting on May 31, 1996. Public notice announcing the plan ran
in the June 4 Jacksonville Patriot, and the June 5 North Pulaski
Leader. As part of its decision on the remedy selected for
Operable Unit 3 (OU3), the Agency conducted a public open house
on June 11, 1996, at the Jacksonville City Hall to present the
Proposed Plan and answer questions. The EPA held a public
comment period regarding the RI/FS, Proposed P1^n and
Administrative Record from June 12, 1996, to duiy 26, 1996. The
documents in the Administrative Record were made available to the
public at the Jacksonville City Hall, the ADPC&E in Little Rock
and the EPA in Dallas. The public comment period was re-opened
on August 2, 1996 and closed on August 19, 1996. A formal public
meeting was held on July 16, 1996, at the Jacksonville City Hall.
Representatives from EPA presented a description of the site
geology, nature of ground water contamination, remedial
alternatives considered in the proposed plan, and EPA's preferred
alternative. The EPA solicited public comments at this meeting
and answered questions on the plan. Responses to all comments
received during the public comment period, either written or
verbally expressed at the public meeting, are included in the
Responsiveness Summary which is included as part of this ROD
(Appendix A).
This decision document presents the selected remedial action
for contaminated ground water at the Vertac site in Jacksonville,
Arkansas, chosen in accordance with CERCLA, as amended by the
11
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Superfund Amendments and Reauthorization Act and, to the extent
practicable, the National Contingency Plan (NCP). The decision
for this site is based on the Administrative Record.
4.0 SCOPE AND ROLE OF OPERABLE UNIT
The problems at the Vertac Superfund site are complex, and
the EPA has determined that site remediation can be accomplished
most efficiently in six phases. This ROD addresses one of the
six cleanup phases, i.e., Operable Unit 3, which encompasses site
ground water.
Ground water contaminants in several areas of the site
exceed Maximum Contaminant Levels (MCLs) defined under the Safe
Drinking Water Act (SDWA), 42 U.S.C. § 300f et seq., and found at
40 CFR §§ 141.11-141.26. The studies undertaken at the Vertac
Superfund site for Operable Unit 3 media have identified the
NAPLs at the site to be a principal threat in light of all the
media being remediated at the site. Generally, EPA associates
principal threats with liquids, areas contaminated with high
concentrations of toxic compounds, and highly mobile materials
that generally cannot be reliably contained. See NCP Section
300.430(a) (iii) (A), 40 CFR § 300.430(a) (iii) (A) . Low-level
threat wastes are those source materials that can be reliably
contained and that would pose only a low risk in the event of a
release. Wastes that generally are considered to constitute a
low-level threat include surface soils containing contaminants of
concern that are relatively immobile in air or ground water,
i.e., non-liquid, low volatility, and low leachability. See "A
Guide to Principal Threat and Low Level Threat Wastes, Nov. 1991,
EPA Pub. No. 9380.3-06FS). Here, the contaminated ground water
is an environmental medium that has become contaminated through
contact with the principal threat NAPLs. Therefore, the
contaminated ground water constitutes a low-level threat.
Although NAPLs at the site are considered a principal
threat because they contain high concentrations of toxic
compounds, the removal of these materials is not technically
practicable due to the presence of these materials in a fractured
bedrock aquifer. Therefore, EPA is invoking a waiver from
restoring ground water to meet Maximum Contaminant Levels
(MCL's). A detailed discussion of EPA's rationale for invoking
this Technical Impracticability waiver is outlined in Section
10.2.
Non-aqueous phase liquids will provide a long-term source
for dissolved phase contamination in ground water. However,
contaminant concentrations in ground water exposed to NAPLs are
generally several orders of magnitude lower than contaminant
levels in the NAPLs. Therefore, contaminated ground water is
considered a low level threat as per the EPA guidance document
12
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mentioned above. Thus, while the selected remedy does not
directly address the principal threat posed by the NAPLs
themselves, it does provide for on-site containment of the low
level threat contaminated ground water, and thereby prevents
likely exposure to receptors. The remedy is protective of human
health in that the medium which will contact the principal threat
is contained on-site. Additionally, the engineering controls to
contain ground water on-site will be supplemented with
institutional controls in the form of deed restrictions r- zoning
ordinances prohibiting the installation of water wells in the
area of the site. Also, while currently no effective technology
exists for the actual extraction from the fractured bedrock, the
technology to be employed to contain the ground water within the
site's confines has been proven to be effective and reliable for
such ground water containment (versus NAPL extraction). Finally,
CERCLA Section 121(c), 42 U.S.C. § 9621(c), requires that
whenever EPA implements a remedy that results in hazardous
substances remaining at a site, EPA must reevaluate that remedy
at least every five years from the remedy's initiation.
Therefore, by selecting a containment remedy due to the
impracticability of removing and treating the principal threat
NAPLs, EPA will be required by law to reevaluate this remedy
every five years. Thus, should a technology emerge that is
capable of addressing the NAPL, EPA will be required to evaluate
that technology and possibly to amend this ROD to utilize that
technology to address the principal threat wastes that are the
source of the ground water contamination.
The concentrations of dioxin and other site contaminants
present in the Vertac site ground water are generally several
orders of magnitude lower than the concentrations found in other
dioxin-contaminated site media (e.g. soils, drummed still bottom
wastes, and process tank sludges). Dioxins are characterized as
having a very low solubility in water and a very low vapor
pressure, which means that they do not readily leach to ground
water or vaporize to the air. Numerous studies have also shown
that dioxin binds tightly to fine-grained and organic-rich soils
or geologic strata, which characteristically further reduces its
mobility. In addition, other toxic compounds in ground water
beneath the Vertac site, if left unremediated, could present a
long-term threat to the public health and the environment due to
the potential for migration of contaminated ground water off-site
and the potential for cancer and non-cancer effects stemming from
long-term contact with that ground water. Migration could occur
to a point of discharge to surface water (e.g. Rocky Branch
Creek) or to off-site areas where contaminated ground water could
be produced through domestic water supply wells. Therefore, the
contaminated ground water constitutes a low level threat, both
with respect to its dioxin and other toxic components. See
"Guide to Principal Threat and Low Level Threat Wastes," EPA
Publication 9830.306FS, November 1991.
13
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Due to the technical impracticability of addressing the
NAPLs, EPA has developed remedial action objectives to address
the ground water compounds of concern at this site. These
objectives are intended to control the movement of the low-level
threat contaminated ground water at the site so that exposure of
an environmental receptor to the contaminants contained in the
ground water does not result in an unacceptable carcinogenic risk
or an adverse toxic response.
The remedial action objectives for ground water (OU3) are:
1. To prevent contamination of off-site ground water by
controlling ground water migration within the area of
the site through the use of ground water extraction
wells and the existing French drain system; and,
2. To prevent off-site human and environmental receptors
from potential exposure to contaminated ground water
discharges that would result in an adverse toxic
response or a carcinogenic risk greater than 1 x 10~4
to 1 x 10"6. Due to remedial efforts under other
cleanup phases described below, and restricted future
access to areas where on-site monitor wells, the
wastewater treatment plant, and the landfills exist,
the ROD for OU3 does not address remedial objectives
for on-site receptors.
A description of the six cleanup phases or operable units
that are currently in progress, or have been completed at the
Vertac site, appears below. Collectively, the completion of all
six phases is intended to address all environmental risks posed
by the site.
Phase 1 The "VERTAC REMEDY"
The ADPC&E issued an order in 1979 that required Vertac,
Inc., to improve its hazardous waste practices, and in 1980 EPA
and ADPC&E jointly filed suit in federal district court against
Vertac, Inc., and Hercules, Inc. A Consent Decree entered into
by EPA, ADPC&E, Vertac, and Hercules in January 1982 required an
independent consultant to assess the conditions of on-site wastes
and to develop a proposed disposal method for the wastes. The
proposal, called the "Vertac Remedy", was deemed by EPA to be
unsatisfactory and EPA returned to court in early 1984 for a
resolution. The court decided in favor of the proposed remedy,
which was implemented in the summer of 1984 and completed in July
1986.
As part of the remedy, the Vertac plant cooling water pond
and the equalization basin were closed and sediments from these
units were removed and placed into an above-ground vault. The
burial area was capped and a French drain and leachate collection
14
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system were installed around the burial areas. Ground water
monitoring wells were also installed and a ground water
monitoring program was initiated.
Phase 2 DRUMMED WASTE INCINERATION
In 1989, ADPC&E signed a contract to have approximately
29,000 barrels of 2,4-D and 2,4,5-T herbicide still bottom wastes
incinerated on-site. Wastes from the production of 2,4,5-T at
this site have been found to contain up to 50 ppm of dioxin,
while wastes from the production of 2,4-D generally contain
dioxin in the low parts per billion range. All drummed wastes
are treated as F-listed (dioxin containing) wastes pursuant to
RCRA, 42 U.S.C. § 6901 et seq.
To accomplish this incineration, the State used funds from
the trust fund that was established when Vertac went bankrupt.
Incineration of these wastes began in the fall of 1990. In June
1993, funding for the project was depleted and EPA assumed
immediate responsibility for incinerating the remaining drums as
a time-critical removal action undertaken pursuant to CERCLA
Section 104, 42 U.S.C. § 9604. In late September 1994, the
incineration of 25,179 drums of dioxin-contaminated 2,4-D waste
was completed at the Vertac site. In July 1995 EPA announced
that it would pursue the off-site incineration of approximately
3,200 drums of dioxin containing 2,4,5-T waste located at the
Vertac site. On November 9, 1994, a contract was signed between
the APTUS commercial incineration facility in Coffeyville,
Kansas, and EPA's prime contractor URS Consultants, to accept the
Vertac drummed T-waste material. The first shipment of T-waste
went to APTUS in November 1994, and the last shipment was sent
off-site on March 29, 1996.
Phase 3 VERTAC OFF-SITE AREAS
A Record of Decision (ROD) was signed in September 1990 to
address the cleanup of contiguous off-site areas that were
contaminated as a result of untreated and partially treated
surface and underground discharges of plant wastewater and other
releases. Elements of this operable unit include an active sewer
interceptor, portions of an old abandoned trickling filter
wastewater treatment plant, an active WWTP, and the Rocky Branch
Creek flood plain. The selected remedy called for removing
sediments from the active sewer interceptor, installing pipe
liners in the clean sewer, filling the abandoned interceptor with
grout, and removing sludge from the sludge digester in the old
wastewater treatment plant. Sludge drying beds in the old
wastewater treatment plant were capped with one foot of clean
soil and the aeration basin in the old wastewater treatment plant
was drained and demolished. Flood plain soils along Rocky Branch
Creek that are contaminated with dioxin in excess of one part per
billion (ppb) will be excavated for treatment at Vertac.
15
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Monitoring of fish in Rocky Branch Creek and Bayou Meto for
dioxin will continue.
As EPA proceeded with overall site remediation, it concluded
that it was appropriate to defer the disposal of the contaminated
soil and debris addressed in the 1990 Off-Site Areas ROD to make
the disposal of excavated off-site soils and debris consistent
with the disposal of on-site soils and debris. All other
elements of the off-site remedial action, except for the above-
mentioned off-site soils and debris disposal and the excavation
of flood plain soils, were completed in November 1995.
Hercules has completed the remedial design and has started
the remedial action under the terms of a Unilateral
Administrative Order issued in July 1993. The Order requires
Hercules to conduct the remedial design and remedial action to
implement the selected remedy, except the on-site incineration of
soils excavated from the Rocky Branch Creek flood plain and
contaminated sludges and debris from sewage treatment plant and
sediments from the interceptor lines was deferred to make the
disposal of excavated off-si' . soils consistent with the disposal
of on-site soils. All off-site remedial actions (except for the
excavation of flood plain soils) were completed in November 1995.
The excavation of the flood plain soils is expected to be
completed in early 1997.
Therefore, concurrent with the execution of the OU3 ROD, EPA
also is executing an amendment to the Off-Site Area ROD in
conjunction with the ROD for Vertac Operable Unit 2 (OU2), On-
Site Soils and Underground Utilities. That ROD addresses both
the on-site soils having dioxin concentrations in excess of 5
parts per billion (ppb) and the excavated soils from the Rocky
Branch Creek Flood Plain, the sediments removed from the sewage
collection lines leading to the Old Sewage Treatment Plant, and
the sludge removed from the sludge digester. The remedy selected
in that ROD for the above-mentioned contaminated soil and debris
is on-site disposal in an on-site hazardous waste landfill that
will be constructed and operated in compliance with applicable
substantive requirements under Subtitle C of the Resource
Conservation and Recovery Act (RCRA), 42 U.S.C. § 6901 et seq.
Phase 4 ON-SITE ABOVE GROUND MEDIA (Operable Unit 1)
A ROD for the above ground media was signed in June 1993.
The above ground media include buildings, process equipment,
leftover chemicals in the process vessels, spent activated
carbon, shredded trash and pallets, and miscellaneous drummed
wastes at the site. The selected remedy consisted of: (1) On-
site incineration of F-listed process vessel contents, spent
carbon, shredded trash and pallets, and miscellaneous drummed
wastes; (2) off-site incineration of PCB transformer oils and
non- F-listed process vessel contents; (3) recycle/reuse of
16
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decontaminated process equipment to the maximum extent
practicable; (4) on-site consolidation of debris resulting from
demolition of buildings and equipment that cannot be
recycled/reused in a RCRA subtitle C landfill; (5) the deferral
of a decision on the treatment of approximately 2,770 cubic yards
of residential soils contaminated with 2,3,7,8-
tetrachlorodibenzo-p-dioxin (TCDD) Hercules, Inc., had excavated
as a removal action in 1990 from contiguous residential areas
south of the site; (6) disposal of treatment residues consistent
with disposal of ash and salt that was generated by the
incineration of drummed wastes at the site; and, (7) the
construction of a RCRA Subtitle C landfill on-site.
A Unilateral Administrative Order (UAO) was issued to
Hercules, Inc., in March 1994 requiring it to perform the
remedial design and remedial action under the ROD for OU1.
Hercules' remedial design work plan has been approved. Part of
the work plan expressed interest in pursuing off-site
incineration as the means to perform the actions under the ROD.
Therefore, Hercules has signed a contract with APTUS, an off-site
commercial hazardous waste incineration facility. An Explanation
of Significant Difference (BSD) was issued in May 1995 by EPA to
allow such off-site incineration. Hercules has completed off-
site incineration of F-listed and non- F-listed liquids and
solids that were present in the process vessels. The remedial
design is expected to be complete by the end of 1996. Hercules
has commenced construction of the on-site RCRA Subtitle C
landfill, with completion expected in November 1996. Also,
Hercules has commenced the off-site shipment of activated carbon
that was used for the treatment of leachate and storm water,
which should be completed by the end of 1996. All remedial
actions for this Operable Unit are expected to be completed by
the end of 1997.
Phase 5 SOILS AND UNDERGROUND UTILITIES (Operable Unit 2)
Operable Unit 2 (OU2) media are the subject of the ROD
executed concurrently with the OU3 ROD, and addresses surface and
subsurface soils, underground utilities, underground fuel storage
tanks, foundations, curbs and pads. In addition, in conjunction
with an amendment to the Off-Site Areas ROD, the ROD for OU2
addresses media originally intended to be addressed by the Off-
Site Areas ROD, which consist of contiguous soils from the Rocky
Branch Creek flood plain, sludge from the Old Sewage Treatment
Plant sludge digester, and the sediment from the associated
interceptor lines (which are considered to be contiguous to the
site due to the continuous connection to the site via the sewer
interceptor). Finally, the ROD for OU2 also addresses bagged
soils Hercules had excavated from contiguous residential yards in
1990 as part of a removal action, the treatment of which EPA
deferred in the OU1 ROD.
17
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Because of the similarity of OU2 low level threat media to
the low level threat media from the Off-Site Areas ROD and
contiguous off-site residential soils Hercules had excavated
during a 1990 removal action, EPA has chosen to address them in
the OU2 ROD so that similar waste materials associated with the
Vertac site would be treated in a consistent manner.
The ROD for the off-site area, September 1990, called for
the excavation and incineration of soils in the flood plain area
along Rocky Branch Creek that had a 2,3,7,8-TCDD concentration
greater than 1 ppb. The estimated volume of flood plain soils is
approximately 4,100 cubic yards. The off-site ROD also called
for the incineration of sludges removed from the digester and
sediments from the interceptor that connected the Old Sewage
Treatment Plant to the Vertac facility. The approximate volume
of sludges from the digester is 800 cubic yards, and the
approximate volume of sediments from the interceptor line is 2
cubic yards. The ROD for OU1 deferred the treatment decision for
the bagged soils removed from residential yards as a part of a
removal action in 1990. The total volume of bagged soil is
estimated at 2,770 cubic yards. The final disposition of these
materials will be discussed in detail in the ROD for OU2.
Phase 6 GROUND WATER
Hercules completed the RI/FS for this phase of the site
cleanup in September 1995. Since that time, contaminated ground
water at the site has been designated as a separate operable
unit, Operable Unit 3, which is the subject of this ROD. Ground
water at the Vertac site is contaminated with, among other
things, chlorophenols, chlorophenoxyherbicides, and dioxin.
Ground water remediation will pose certain technical challenges
due the combination of complex subsurface geology (tilted,
fractured bedrock) and the presence of dense nonaqueous phase
liquids (DNAPLs). More detailed information on the site ground
water and the nature of contamination is discussed in Sections
5.2 and 5.3 of this document.
5.0 SUMMARY OF SITE CHARACTERISTICS
5.1 DEMOGRAPHY AND LAND USE IN THE AREA OF THE SITE
The Vertac site covers approximately 193 acres on Marshall
Road within the city limits of Jacksonville, Arkansas, population
29,000. Approximately 1,000 residents live within one mile of
the site with residential areas bordering the entire east and
south sides. The west and northern sides of the site are bounded
by an industrial area and the Little Rock Air Force Base.
The Vertac site is currently zoned for industrial use and
has been used for commercial/industrial operations for
18
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SCALE IN FEET
APPROXIMATE
Figure 3
Land Use Zoning Map
-------
approximately 50 years. Land use zoning near the Vertac plant is
shown in Figure 3. The area just south of the Vertac site,
between Marshall Road and the Missouri-Pacific railroad tracks,
south to West Main Street, is a residential area made up of both
single family homes and apartments. The area immediately west of
the railroad tracks and north of West Main Street has recently
been developed and supports several light industries. The area
between West Main Street and South Redmond Road is commercial and
light industrial. Just south of South Redmond Road is
undeveloped land that includes the Jacksonville Sewage Treatment
Plant, DuPree Park, and Lake DuPree. On to the south, the rest
of the area consists predominantly of irrigated rice fields and
woodlands.
5.2 SOILS AND GEOLOGY
5.2.1 Soils
Soils in the area of the plant are classified as the
Leadvale-Urban land complex with a 1 to 3 percent slope. The
Leadvale series soils are composed of moderately well-drained
soils in valleys, formed mainly of loamy sediment and washed from
uplands consisting of weathered shale, siltstone and sandstone,
such as those that underlie the site. Leadvale soils are
generally described as having moderately low permeability and a
seasonally perched water table. The Leadvale-Urban land complex
consists of areas of Leadvale soils that have been modified by
urban development. Because of the extensive development and
earth-moving activities at the site, natural soil characteristics
have been obscured.
5.2.2 Geology
Tne site lies in the transition zone between the Coastal
Plain and the Interior Highlands Physiographic Province. The
surficial geology of the Coastal Plain Province in the region
surrounding the site is dominated by westward thinning wedge of
unconsolidated sediment consisting of the Tertiary Age Clairborne
Group, Wilcox Group, and Midway Formation.
The Clairborne Group and the Wilcox Group are
undifferentiated along the fall line that occurs in the site
area. The wedge onlaps the Rocks of Pennsylvanian Age lower
Atoka Formation, which dominate the geology of the Interior
Highlands Province in the region surrounding the site.
Quaternary alluvium and terrace deposits occur locally along
drainages in both provinces and are more common in the Coastal
Plain Province. A generalized summary of the geologic formations
surrounding the site is presented in Table 1. A map of the site
geology is presented in Figure 4.
20
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The contact between the Tertiary Age sediments and the
Pennsylvanian Age rocks occurs along a regional trend of
northeast to southwest and is present in the area of the site.
On a local scale, the trend of the contact depends on the current
erosional surface and the paleotopographic surface of the Atoka
Formation. The strike of the Wilcox Group Sediments and the
Midway Formation tends toward the northeast-southwest. The dip
of the sediments is low and oriented toward the southeast. The
Midway Formation was deposited onto the irregular and wea+^ered
surface of the Atoka Formation, which was folded and fractured
during the late stages of the Alleghenian orogeny. The Atoka
Formation was later uplifted and weathered. In the area of the
site, the strike of the beds in the Atoka Formation trends about
N70°W and the dip is approximately 35° to the northeast.
The Atoka Formation, which comprises the contaminated
aquifer at the site, outcrops along Rocky Branch Creek in the
western part of the site. Unweathered Atoka strata consist of
alternating beds of highly consolidated and fractured sandstone,
siltstone, and shale. The principal water-bearing units in the
formation are the sandstone beds, which are characterized by low
primary or intergranular porosity, and relatively effective
fracture porosity. The sandstones are confined or semi-confined
by the shale and siltstone units. Across most of the site the
Atoka Formation exhibits vertical zonation consisting of 2 to 18
feet of unconsolidated weathered bedrock underlain by up to 35
feet of consolidated, weathered bedrock, which overlies
consolidated, fresh bedrock.
5.3 HYDROLOGY
5.3.1 Surface Water
Because of the potential for surface runoff to transport
potentially contaminated soils off of the site, previous remedial
actions included the installation of sumps to collect the first
flush of surface water runoff from the central process area for
treatment. After treatment, this water is discharged to Rocky
Branch Creek. Runoff that exceeds the capacity of the sumps
currently flows to the Rocky Branch Creek. The ROD for OU2
partially addresses potentially contaminated sediments that
bypass the sumps after they are inundated by heavy rains.
There are two major drainageways in the area, Rocky Branch
Creek, and Bayou Meto, which is a tributary to the Arkansas
River. Rocky Branch Creek flows through the part of the site
west of the central process area. Approximately 2 miles
downstream, Rocky Branch Creek flows into Bayou Meto.
21
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CLEAN
SAND
BEDS
YIELD
DOMESTIC
SUPPLIES
GENERALLY
NON-WATER
BEARING
DEEPLY BURIED.
SALINE WATER
WATER BEARING IN
OUTCROP ONLY,
DOMESTIC SUPPLIES
UP TO 1 0 GPM
M327 4127
TABLE 1 SUMMARY OF SELECTED GEOLOGIC FORMATIONS AND WATER - YIELDING
CHARACTERISTICS FOR REGION SURROUNDING VERT AC SITE
Plebuch 11960]
-------
R. 11W. R.I ON.
F- .'.
>, \-
/ Mi! / tSD ) \
,^**.-;lP,
\
Legend
Tertiary -I
Pennsylvanian
U/ilCox G'Oup - Orange red
i to Red brown ^Nty Sand
j lo Sirty Clay
l Midway F or matjon Ught Gt^y
Clay or Silcy Clay
l Atoka Formation . Iniertied-Jco
Sandstones. Siltitones ana Shnft-s
Geologic Contort. D^ihcd
\Vhere Approximate
Note Geology adapted from Stone. 1984
w-
400 800
1200
Scale In Feet
Source Verwc Site Boundary and Phoiogiamm!
Survey Prepared by West nnd Associate1
FIGURE 4
SITE SURFICIAL GEOLOGY MAP
VERTAC SITE, JACKSONVILLE. AR
-------
Surface drainage ditches on the western part of the site
direct local runoff westward toward Rocky Branch Creek. An
earthen dam was constructed across the creek in the early 1950's
to form a cooling water pond that was used to supply non-contact
cooling water to the plant.
At its maximum extent, the pond extended to a distance of
about 1,000 feet north of the dam. The pond was adjacent to the
north burial area. The dam was removed and the cooling water
pond was closed in July 1985. Rocky Branch Creek was diverted
around the location of the former cooling water pond as a part of
the pond closure. The diversion is maintained today by an
earthen dike along the eastern side of the creek.
Surface water runoff from the western part of the central
process area, including the central ditch that transects the
central process area, is contained in drainage ditches that
divert the initial runoff to sumps. The sumps are connected to
the water treatment plant, which uses activated granular carbon
to treat the water.
Surface drainage ditches in the northeastern part of the
site direct runoff eastward toward a primary ditch that lies
along the western side of Marshall Road. This ditch directs
water toward Rocky Branch Creek south of the site.
5.3.2 Ground Water
Ground water in the area near the site occurs in both the
unconsolidated surface deposits and the underlying bedrock.
These strata are generally not considered to be major sources of
ground water near the site. Ground water supplies in the region
are generally obtained from the unconsolidated sands and gravels
in the Tertiary and younger Quaternary sediments. Most ground
water is produced from wells completed in the sands within the
Wilcox Group and basal sands and gravels within the Pleistocene
alluvium and terrace deposits. Yields from these deposits can
range up to 2,000 gallons per minute (gpm).
Ground water at the site is first encountered approximately
5 to 10 feet below the ground surface. Ground water in the
unconsolidated surface deposits is present in the primary
intergranular pore space. Porosity in the bedrock primarily
exists as fractures and partings within the rock. Due to low
porosity and permeability, the ground water yield of the Atoka
units is low. Some domestic ground water supplies are obtained
from the Atoka Formation. Yields can range up to 10 gpm.
Ground water movement in the bedrock is dominated by flow
along the fractures primarily within the sandstone units. The
general direction of flow is outward from the central process
area (CPA), which appears to act as a recharge area. Within the
24
-------
CPA, a ground water divide separates flow to the east and west.
Flow to the west of this divide moves toward Rocky Branch Creek.
The existing French drain (installed as part of the "Vertac
Remedy") was designed to intercept the shallow ground water and
associated site-related contaminants flowing in this westward
direction before it reaches the creek. Western components of
ground water flowing within the central process plant area appear
to be influenced by the central ditch. Evidence of this
includes, perennial seeps along the banks of the ditch and by
deflection in the ground water elevation contours in areas
adjacent to the ditch. Figure 5 depicts the shallow ground water
flow model for the site.
Ground water is not currently used at the site for any
purpose and there are no ground water supply wells within 1/2
mile of the site. Ground water resources from the Atoka are not
currently and are not expected to be used for drinking water
purposes in the vicinity of the site because of the low yield of
the aquifer and the availability of municipal water supplies.
Therefore, EPA has made the reasonable assumption that future
ground water use patterns -*ith respect to the Atoka within and
adjacent to the site will not change. Thus, EPA has concluded
that in the future the ground water will not be used as a
drinking water source. The nearest public water supply wells are
located approximately 2.5 miles southeast of the site. These
wells produce from the Wilcox Formation which is present over the
northeastern portion of the site, but has not been found to be
contaminated. The Wilcox Formation does not exist where NAPL
contamination has been detected at the site.
Overall, the hydrology in the area of the site is influenced
by the location of Rocky Branch Creek, the French drain, the
central ditch, and the hydraulic characteristics of the
unconsolidated surface deposits, weathered bedrock, and fresh
bedrock.
5.4 REMEDIAL INVESTIGATION FINDINGS
5.4.1 Background
Site investigations and remedial actions have been performed
at the site since 1978. Figure 6 shows an overview of the
remedial action performed at the site to date, mostly involving
the closing of a cooling water pond, capping old landfills and
burial areas, and the installation of a french drain leachate
collection system around the landfills and an on-site wastewater
treatment plant.
Hercules, Inc., completed the RI for OU2 Phase 1 in December
1992 which addressed surface and subsurface soils, shallow ground
water, and underground structures such as underground utilities,
foundations, curbs, pads and fuel storage tanks. The USTs have
25
-------
*\. "^r^--! LO JlHI"4£<*
xT°- ** " T " ^"~
Legend
Approximate Boundary of Rechargp
Area (Varies with Seasonal \fatn- LevH Ch,im
Covered Area
Recharye Area
* Discharge Area
JU Seep/Spring Location
gM| Area of ReguMrty Ponded Water
P Downward Component of Hydraulic
Gradient at Well Pair
U Upward Compon*/nt of Hydraulic
Gradient at Wed Pair
_. _ Property Boundary
a^ Direction of Potential
Groundwater Flow
400
800
Seal* In F*«t
Notes: 1 Some jmafl covered areas may exitt wtthin rhe
central process area but are hidden from view
and are too vnatt to display
2. Seep/iprfng locations were observed during
the Rl (nveitfqatlon by WESTON personnel
3 The occureocei of seepi and sprtngi vary
with seasonal and other types of pieiomptric
fluctuations
Vertac Site Boundary and Photoqrammetric
Sun«y frepved by Wen and AuociMei. Inc
North Zone (NAO
FIOUNEi
HALLOW OROUND WATER
FLOW MODEL
verrActrrc
JACKSOHVtiE, AK
-------
Legend
Capped Equalization Basin Area
Sediment Containment Vault
Capped Reasor-HiU Landfill Area
Capped North Landfill Area
Closed Cooling Pond Aren
Excavated Surface Soils Area
Asphalt-Capped Blow Out Area
Scraped Areas
French Drain
Slurry Wall
Fence Line
Central Ditch
Railroad
Diversion Dike
Clay Barrier Wad
Drainage Ditch,
Gunnite-Covered
Surface Water Sump
Buildings and Foundations
w
400 BOO 1200
Scale In Feet
Source: Vertac Site Boundary and Photogrammetric
Survey Prepared by West and Associates. Inc.
Projection: Arkansas Coordinate System.
North Zone (NAD 1983)
FIGURE 6
MAP SHOWING AREAS OF
PAST REMEDIALTION AT
VERTAC SITE
JACKSONVILLE, AR
-------
since been addressed. Hercules, Inc., emptied these underground
storage tanks (USTs) and filled them with grout. The OU2 Phase 2
RI, completed in September 1995, principally addressed deep
ground water contamination, the occurrence of non-aqueous phase
liquids (NAPLs), and some additional soil investigation in the
northern part of the site. Ground water has since been split off
into a separate operable unit (OU3), addressed by this ROD, for
the purpose of expediting the completion of the soils and
underground structures remediation effort selected in the ROD for
OU2.
Ground water-related activities conducted in the Phase 1 RI
included the installation of 27 monitoring wells, which have been
used for measuring ground water elevations and collecting ground
water samples. Additionally, stratigraphic borings were drilled
to assist in characterizing the hydrogeological framework for the
site. Short term pump tests were also conducted to define the
hydraulic characteristics of the site aquifer.
The primary objective of the Phase 2 RI was to resolve
information gaps remaining after completion of the Phase 1 RI.
One of the information gaps related to ground water was the
extent of non-aqueous phase liquid (NAPL) contamination. To
address these gaps, test pits and additional monitoring wells
were installed, sampled, and assessed for the presence of light
non-aqueous phase liquids (LNAPLs) and dense non-aqueous phase
liquids (DNAPLs).
5.4.2 Nature of Ground Water Contamination
The RI results revealed that the Atoka Formation was the
primary geologic formation at the site, and the only formation
exhibiting the presence of site-related contaminants. Site-
relatea ground water contaminants of concern (COCs) are shown in
Table 2. Ground water sampling from on-site monitoring wells
indicates the highest concentrations of dissolved-phase compounds
outside of the landfill areas appear to be contained primarily
within the Central Process Area (CPA), although there is evidence
that some site contaminants have migrated eastward, to an area
near the eastern property boundary. Based on the sampling
results, EPA does not believe contaminants have moved beyond the
eastern site boundary in concentrations exceeding Maximum
Contaminant Levels as defined under the Safe Drinking Water Act
(SDWA), 42 U.S.C. § 300f et seq., or Plume Contaminant Levels
established in this ROD.
28
-------
Table 2.
CONTAMINANT
2 -Chlorophenol
4-Chlorophenol
2 , 4-Dichlorophenol
2 , 6-Dichlorophenol
2,4, 5-Trichlorophenol
2,4, 6-Trichlorophenol
Toluene
Tetrachlorobenzene
2,4-D
2,6-D
Silvex
2,4,5-T
2,4,6-T
2,3,7,8-TCDD
RANGE OF DETECTED CONCENTRATIONS*
0.002-66.7 mg/L
0.001-61.4 mg/L
0.0012-597 mg/L
0.001-90.1 mg/L
0.002-411 mg/L
0.001-94 mg/L
0.002-440 mg/L
0.008-2.9 mg/L
0.00015-1,640 mg/L
0.006-1,100 mg/L
0.00036-110 mg/L
0.0001-380 mg/L
0.004-210 mg/L
0.85-2,080 ng/L
* Includes estimated
sample quantitation
concentrations, usually below the minimum
limit.
Primary areas of concern that may be source a_ as for ground
water contamination within the CPA were identified in the RI as
follows (see also Figure 7):
Monitoring Well 80 (MW-80) and MW-81 near the chemical sewer
and down dip from the central ditch.
Southern margin of the north landfill where uncapped burial
areas were reported north of the existing chlorination plant
(near MW-64) west of the product storage building.
MW-71/MW-72 area down-gradient from reported uncapped burial
area west of the product storage building and down-gradient
from the east drum field.
MW-78/MW-79 area within the blow out area and down-gradient
from the recycle liquor basin.
29
-------
Estimated
Boundary of
Groundwater Plum's
East Drum Storage
Field Area
Boiler House
Area
Legend
|"" " "^ Major Source Areas for
» MM I Groundwater Contamination
Reasor Hill Well
- . .C-$. - - chemical Sewer
Capped Equalization Basin Area
Sediment Containment Vault
Capped Reasor-HIII Landfill Area
Capped North Landfill Area
Closed Cooling Pond Area
Excavated Surface Soils Area
Asphalt-Capped Blow Out Area
French Drain
Slurry Wall
Central Process Area Boundary
Clay Barrier Wall
Buildings and Foundations
Direction of Potential
Groundwaler Flow
Potentially Recoverable
NAPLs Detected
Traces of NAPLs Detected
Areas of Elevated Levels of
Dissolved Compounds
Test Pits with Traces of NAPL
o
400
BOO
1200
Scale In Feet
Vertac Site Boundary and Photogrammetric
Survey Prepared by West and Associates. Inc.
Projection: Arkansas Coordinate System.
North Zone |NAO 1983|.
FIGURE 7
LOCATIONS OF OBSERVED NAPL
AND DISSOLVED-PHASE
SITE-RELATED COMPOUNDS
VERTAC SITE. JACKSONVILLE, AR
-------
Reasor-Hill well area where drums of waste were reportedly
disposed into the well.
NAPLs or possible evidence of NAPLs were observed at the
following monitoring locations:
The Reasor-Hill well.
The Tetrachlorobenzene spill area, which includes test pits
TP-1, TP-2 and stratigraphic boring XB-3.
Monitoring Well MW-23A.
Stratigraphic Boring XB-19.
Existing French drain system.
Central ditch, and test pits in central process area.
Monitoring Well MW-64.
Monitoring Well MW-71.
Monitoring Wells MW-62 and MW-63.
Of the above locations, NAPLs were only observed in
recoverable quantities at the Reasor Hill Well, stratigraphic
boring XB-3, and at MW-23A.
A long term pilot ground water extraction test was performed
to collect information to support design of a potential future
ground water extraction system. The results of the test showed
that very low pumping rates of 4 gallons per minute (gpm) or less
per well resulted in an area of hydraulic influence within the
water bearing unit being tested that is at least 1,020 feet long
and 355 feet wide. In addition, improvements in water quality
were found from samples collected from the margins of the zone of
influence.
The Remedial Investigations described above indicate that
ground water contamination at the site is complex, resulting from
past waste management and disposal practices. Sources of
contamination include on-site landfills, spills and discharges
into the central ditch, Reasor Hill well, and other parts of the
central process area. Both dissolved phase and nonaqueous phase
contamination exist in the subsurface aquifer. Nonaqueous phases
include both DNAPLs and LNAPLs.
31
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6.0 SUMMARY OF SITE RISKS
6.1 RISK ASSESSMENT DESCRIPTION
An evaluation of the potential risks to human health and the
environment from site contaminants associated with ground water
was presented in a separate document called the OU2 Baseline Risk
Assessment. The baseline risk assessment was completed in
concert with the development of the RI/FS. The purpose of the
baseline risk assessment is to evaluate the potential risk to
human health and the environment from site contaminants prior to
remediation. The results from the baseline risk assessment are
used to establish cleanup goals for the contaminants at the site
that pose the greatest risk. The OU2 baseline risk assessment is
divided into two main sections, the Human Health Risk Assessment,
and the Ecological Risk Assessment.
In general, a risk assessment is a procedure which uses a
combination of facts and assumptions to estimate the potential
for adverse effects on human health and the environment from
exposure to contaminants fov1 at a site. The environmental or
ecological risk assessment is conducted to determine if there are
any current or potential impacts on ecological receptors
attributable to the unremediated site. Human health risks are
determined by evaluating known chemical exposure limits and
actual concentrations at the site as identified during the RI
sampling activities. In the risk assessment, carcinogenic risks
(from chemicals that are known or believed to cause cancer) and
non-carcinogenic health risks (from chemicals that are not known
to cause cancer, but can cause a range of other illnesses) are
calculated.
6.2 IDENTIFICATION OF CHEMICALS OF CONCERN
This section summarizes the site data that were used to
evaluate potential health risks to human and nonhuman receptors.
The substances that were considered for each exposure medium
include the following:
Surface Soil - Chlorophenols
- Chlorophenoxyherbicides
- 2,3,7,8-TCDD
Ground Water - Acetone
Chloroform
Chlorophenols
Chlorophenoxyherbicides
- Methylene Chloride
Nitroaromatic explosives
Priority pollutant metals
- 2,3,7,8-TCDD
Tetrachlorobenzene
32
-------
Toluene
Surface Water - Chlorophenols
Chlorophenoxyherbicides
- 2,3,7,8-TCDD
Toluene
An effort was made to focus the risk assessment on those
chemicals that are of greatest concern for a given medium.
Chemicals that were infrequently detected in a medium that was
sampled systematically, unless there was evidence for a "hot
spot" were eliminated (see U.S. EPA guidance, 1989 (b)).
Tables 3, 4, and 5 present the data summary for substances
of potential concern for each medium and their frequency of
detection. Please note that the terminology used in Tables 3
through 5 is consistent with the terminology set out in the EPA
guidance document "Supplemental Guidance to Risk Assessment
Guidance for Superfund (RAGS): Calculating the Concentration
Term," OSWER Publication 9285.7-081, 1992. Therefore, the term
"Upper 95% Confidence Lim:'1- of the Geometric Mean" used in Tables
3 through 5 actually means the upper 95% confidence limit of the
arithmetic mean. However, when evaluating the combined risk
posed by all the COCs at the site, dioxin contributed over 99
percent of the total risk.
6.3 HUMAN HEALTH RISK ASSESSMENT
6.3.1 Summary
A baseline risk assessment was conducted for the Vertac site
where risks were evaluated using current site conditions for
three potential receptor scenarios: teenage trespasser, current
unprotected worker, and future unprotected worker. Exposure
routes assessed for the trespasser scenario included dermal
contact with soil, incidental ingestion of soil, contact with
surface water, and inhalation of particulates or vapors.
Exposure routes accessed for the current unprotected worker
scenario included incidental ingestion of soil, dermal contact
with soil, dermal contact with surface water and water from the
production outfalls at the site, and the inhalation of airborne
particulates and vapors. A future unprotected worker was assumed
to be exposed to the same substances of concern as the current
unprotected worker with the addition of the ingestion of site
ground water. It should be noted, however, that the cleanup goal
proposed by EPA for the site does not consider that a future
worker will be consuming ground water. Public water supplies are
readily available and the future use of site ground water as a
drinking water source will be prohibited through institutional
controls.
33
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Table 3
Substances of Potential Concern in Groundwater
Data Summary Atoka Formation
Substance
Frequency of
Detection*
(Range of) Sample
Quantitation Limit(s)
(mg/L)b
Range of Detected
Concentrations
(mg/Lr
Adjusted Geometric
Mean Concentration
(mg/L)b
Upper 95% Confidence
Limit of the Geometric
Mean Concentration
(mg/L)»
Organics
Acetone
Chloroform
2-Chlorophenol
4-Chloropheno!
2,4-D
2,6-D
2,4-Dichlorophenol
2,6-D ichlorophenol
Methylene chloride
Phenol
Silvex
2,4,5-T
2,4,6-T
2,3,7,8-TCDD
Tetrachlorobenzene
Toluene
2,3,6-Trichlorophenol
2,4,5-Trichlorophenol
5/15
3/15
34/76
38/80
52/85
35/47
43/81
35/81
2/15
20/47
41/85
45/85
31/47
9/39
12/30
41/85
19/80
44/81
0.0021-0.11
0.005-0.05
0.005-0.055
0.005-0.014
0.0001-0.027
0.005
0.005-0.06
( 105-0.82
0.005-0.063
0.005
0.0005-0.54
0.00013-0.007
0.005
0.01-1.8
(ng/L)
0,01-0.40
0.001-0.82
0.005-0.82
0.005-4.1
0.009-0.030
0.002-0.030
0.002-66.7
0.001-61.4
0.00015-1,640
0.006-1,100
0.0012-597
0.001-90.1
0.022-0.10
0.001-10
0.00036-110
0.0001-380
0.004-210
0.85-2,080
(ng/L)
0.008-2.9
0.002-440
0.002-8.92
0.002-411
0.0095
0.0049
3.0
13
4,200d
10,COOd
55
4.4
0.0077
1.0
23
430d
230d
13
(ng/L)
0.041
l,100d
0.048
19
0.016
0.0071
16
100d
160,000d
2,000,000d
580
25
0.013
7.6
230d
ll,000d
8,700d
97
(ng/L)
0.10
29,000"
0.095
130
-------
Table 3
Substances of Potential Concern in Groundwater
Data Summary Atoka Formation
(continued)
Substance
Frequency of
Detection'
(Range of) Sample
Quantitation Limit(s)
(mg/L)b
Range of Detected
Concentrations
(mg/L)b'c
Adjusted Geometric
Mean Concentration
(mg/L)b
Upper 95% Confidence
Limit of the Geometric
Mean Concentration
(mg/L)b
Organics (continued)
2,4,6-Trichlorophenol
Inorganics
Antimony
Arsenic
Chromium
Copper
Lead
Mercury
Nickel
Silver
Thallium
Zinc
38/80
3/26
2/26
5/26
3/26
2/26
9/26
10/18
11/26
4/26
22/22
0.005-0.82
0.060
0.010
0.010
0.025
0.003
0.0002-0.00025
0.040
0.010
0.010-0.10
0.0205
0.001-94
2.1
9.9
O.J22-0.029
0.0036-0.013
0.0020-0.012
0.0066-0.025
0.0036-0.011
0.00022-0.00076
0.011-0.109
0.0034-0.0094
0.010-0.100
0.011-0.270
0.029
0.0053
0.0050
0.013
0.0018
0.00023
0.032
0.0056
0.031
0.043
0.030"
0.0056
0.0055
0.014
0.0021
0.00031
0.049
0.0060
0.060
0.063
'Ratio of the number of wells in which the substance was detected during one or more sampling rounds *o the total number of wells sampled.
"With the exception of 2,3,7,8-TCDD, which is expressed in units of ng/L.
Includes "J" values, which are estimated concentrations, usually below the minimum sample quantitation Umit.
dExceeds the maximum reported concentration (Subsection 2.1).
'Sample quantitation limits were not available. The contract-required detection limit/instrument detection limit (CRQL/IDL) is indicated.
-------
Table 4
Substances of Potential Concern in Soil
Data Summary All Samples
Substance
2-Chlorophenol
2,4-D
2,4-Dichlorophfcnol
2,6-DichJorophenol
Silvex
2,4,5-T
2,3,7,8-TCDD
Tetrachlorobenzened
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
Frequency
of
Detection3
19/138
122/127
77/138
33/138
105/124
125/129
443/1,146
1/1
53/137
53/136
Range of
Sample
Quantitation
Limits
(mg/kg)b
0.33-18
0.023-4.2
0.042-18
0.33-18
0.012-670
0.012-670
0.01-4.5
(ng/g)
NI
0.33-3.8
1.7-91
Range of
Detect' 1
Concentrai.ons
(mg/kg)b'c
0.047-3.0
0.0053-5,500
0.034-360
0.066-15
0.0012-290
0.0016-710
0.04-2,200
(ng/g)
670,000
0.033-270
0.047-79
Adjusted
Geometric
Mean
Concentration
(mg/kg)b
0.34
580
3.0
0.54
28
63
5.3
(ng/g)
NA
1.9
2.6
Upper 95%
Confidence Limit
of the Geometric
Mean
Concentration
(mg/kg)b
0.39
3,100
5.0
0.66
110
250
9.2
(ng/g)
NA
3.0
3.4
NA = Not applicable
MI = Information was not available
"Ratio of the number of sampling locations at which the substance was detected to the total number of sampling locations, with the exception of
2,3,7,8-TCDD. The frequency of detection for 2,3,7,8-TCDD is the ratio of the number of composite samples in which 2,3,7,8-TCDD was detected to
the total number of composite samples.
"With the exception of 2,3,7,8-TCDD, which is expressed in units of ng/g.
Includes "J" values, which are estimated below the minimum sample quantitation limit.
dThese data are evaluated in the hot spot analysis (Subsection 3.5).
-------
Table 5
Substances of Potential Concern in Surface Water
Data Summary All Sample Locations
Substance
2-Chlorophenol
4-Chlorophenol
2,4-D
2,6-D
2,4-Dichlorophenol
2,6-Dichlorophenol
Phenol
Silvex
2,4,5-T
2,4,6-T
2,3,7,8-TCDD
Toluene
Frequency of
Detection3
6/6
6/6
6/6
6/6
6/6
6/6
6/6
6/6
6/6
6/6
3/6
6/6
Range of
Sample
Quantitation
Limits
(/WL)b
0.8-5
1.1-5
2-5
2-5
1-5
0.5-50
0.6-5
1-2
1-2
1-2
2-10
(ng/L)
5-21
Range of Detected
Concentrations
(^/L)b'c
0.85-460
1.2-8,800
2.9-17,000
2.0-5,400
1.8-6,800
1.0-1,100
0.60-620
1.0-1,100
1.7-3,300
1.1-11,000
2.0-12
(ng/L)
0.022-3,900
Adjusted
Geometric
Mean
Concentration
(/^/L)b
18
230
1,100
500
200
13
24
84
200
240
1.6
(ng/L)
52
Upper 95%
Confidence Limit
of the Geometric
Mean
Concentration
(/45/L)b
420
480,000d
2,700,000d
45,000d
290,000d
350
4,600d
18,000d
44,000d
33,000d
1.9
(ng/L)
9,900d
-------
Table 5
Substances of Potential Concern in Surface Water
Data Summary All Sample Locations
(continued)
Substance
2,3,6-Trichlorophenol
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
Frequency of
Detection3
5/6
6/6
6/6
Range of
Sample
Quantitation
Limits
(^/L)b
1.2-50
1.5-5
1.1-5
Range of Detected
Concentrations
(A/L)b'c
2.0-69
1.6-5,000
1.7-1,500
Adjusted
Geometric
Mean
Concentration
(/4S/L)b
4.1
130
29
Upper 95%
Confidence Limit
of the Geometric
Mean
Concentration
(^g/L)b
12
350,000d
2,500d
'Ratio of the number of sampling locations at which the substance was detected to the total number of sampling locations.
"With the exception of 2,3,7,8-TCDD, which is expressed in units of ng/L.
Includes "J" values, which are estimated below the minimum sample quantitation limit.
dExceeds the maximum reported concentration (Subsection 2.1).
-------
6.3.2 Exposure Assessment
The potentially exposed populations and the pathways through
which they could be exposed for current and future site
conditions are discussed below.
Current and Future Land Use
The land occupied by the Vertac facility is zoned
commercial/industrial. While there are no manufacturing
operations at the site, it is reasonably anticipated that future
use could include commercial development. Continuing activities
include general maintenance of the plant, maintenance of previous
remedies, and operation of a wastewater treatment plant by PRP
site maintenance workers. Deed restrictions are in place that
will prevent future residential development of the site.
Additional deed restrictions will be sought to limit future
commercial development of portions of the site that will contain
waste disposal areas and are otherwise encumbered by long term
remediation and perpetual operations and maintenance activities.
The land located west and north of the plant is also used
for commercial/industrial purposes. Residential areas are
located directly east and south of the plant.
To assess the current and reasonably anticipated future land
use, four receptors were evaluated: A trespasser, a passerby, a
current unprotected worker, and a future unprotected worker.
Trespassers and workers are the most likely future receptors at
the site and represent those individuals with the highest
potential for exposure to site related substances of concern.
A trespasser could enter the site unnoticed by either
climbing or crawling under one of the fences either currently or
in the future. A teenager between 12 and 18 years of age was
evaluated for this scenario.
A passerby could walk by the east side of the site along
Marshall Road in the future. A teenager between 12 and 18 years
of age was evaluated for future exposure using this scenario.
Although any exposure is considered remote using this future
scenario, it was evaluated since the strip of property along the
west side of Marshall Road may eventually be unrestricted and
without a fence, allowing for future commercial/industrial
development.
Current and future worker scenarios were also evaluated.
Because this site is zoned commercial/industrial, a maintenance
worker is the individual who has the greatest potential to
contact on-site media on a regular basis, both currently and in
the future.
39
-------
Potential Exposure Pathways
Trespasser
It is possible for a trespasser to be exposed to substances
of concern on the site through contact with soil, surface water,
and air. Potential soil exposure routes include dermal contact
and incidental ingestion of soil.
Of the on-site surface waters, a trespasser is most likely
to come into contact with Rocky Branch Creek, which is located
within the western margin of the site. Due to the shallow nature
of the creek, with a depth of approximately 1 foot, only dermal
contact was evaluated. The potential for a trespasser to come
into contact with outfalls that flow to Rocky Branch Creek was
considered to be unlikely, due to the fact that they flow only
during periods of high rainfall.
The trespasser could also be exposed to chemicals of concern
through the inhalation of airborne substances originating from
surface soil and surface wal c (particulate and/or vapor).
The potential for a trespasser to become exposed to site
ground water was considered to be remote. Even if ground water
were to be used on the site in the future, it is likely that the
ground water would be used only after treatment. Thus, this
exposure pathway was not evaluated.
Casual Passerby
A casual passerby was considered for possible exposure to
site related contaminants along the east side of the site
adjacent to Marshall Road, since the existing fence located at
the property boundary will be moved to the west after remedial
action is complete so as to minimize the areas of the site that
will be restricted in that fashion. EPA will not be certain of
precise fence locations until the remedial design phase of the
OU2 soil remediation. However, a casual passerby will have no
actual exposure after remediation since there is no complete
pathway. If the remote possibility is considered for contact of
the passerby through dermal contact and incidental ingestion
similar to a trespasser, this would be a conservative assumption.
After remedial action there will be a greenbelt in this area
to camouflage the site from view of the motorists along Marshall
Road. This greenbelt will be enhanced with vegetation consisting
of grass and fast-growing native trees which will nearly
eliminate any contaminants from becoming airborne for contact
with the passerby. When the site is remediated to 5 ppb the
average concentration of dioxin in the area along Marshall Road
will be less than 1 ppb. This is due to the fact that after
grids where dioxin concentrations exceeding 5 ppb are excavated
40
-------
and replaced with clean backfill material, data indicate that
average dioxin concentrations along Marshall Road will be at or
below 1 ppb because some portions of that area currently have
dioxin concentrations less than 1 ppb. The process of averaging
resulting dioxin concentrations results in a less than 1 ppb
average.
Extremely conservative assumptions were made to calculate
the risk for a casual passerby. Using the most conservative
assumptions possible, the risk posed by the site after
remediation was within EPA's acceptable risk range. Therefore,
the site cleanup to 5 ppb provides for a fully protective remedy.
See memorandum from Ghassan Khoury to Philip Allen in the
Administrative Record.
Current Unprotected Worker
The current unprotected worker was assumed to be exposed to
substances of potential concern through the same exposure routes
as the trespasser: Incidental ingestion of soil, dermal
absorption of soil, dermal absorption from surface water, and
inhalation of airborne soil and vapors. The on-site worker could
also potentially come into contact with all on-site surface
waters, including outfalls, on a regular basis. Contact could
occur during performance of general maintenance activities.
However, because ground water has no current on-site uses, the
current worker has limited potential for contact with ground
water. Thus, the ground water pathway was not evaluated.
Future Unprotected Worker
The future unprotected worker was assumed to be exposed to
the substances of potential concern through the same exposure
routes as the current unprotected worker, with the addition of
the ingestion of site ground water. Ground water is currently
not used as a drinking water source for the site, and it is
unlikely that it will be used as such in the future because of
the availability of public water. Conservatively, this pathway
was evaluated, but EPA did not include this exposure route in
developing remediation goals for the site.
A summary of the exposure pathways used for quantitative
evaluation is shown in Figure 8. Models used to calculate
intakes, i.e., doses of the substances of concern for each
receptor through the various exposure routes are shown in Tables
6, 7, 8, 9, 10, and 11.
6.3.3 Toxicity Assessment
The toxic effects of a chemical generally depend upon the
level of exposure (dose), the route of exposure (oral,
inhalation, dermal), and the duration of exposure (acute,
41
-------
S(
3URCE MECHANSM SOURCE
SOIL
DUST GENERATION i
VOLATILIZATION \ 1
* AIR
RUNOFF ^ DRA.NAGE
HUNUI-hl J ROCKY CREEK
.- » BRANCH
j
LEACHING
GROUNDWATER
RELEASE
11 kk^WlH C/^l ID^C
MECHANISM
,-
VOLATILIZATION
i » AIR *
I
i _^
DISCHARGE
VOLATILIZATION \ * AIR
1
UISCHAHGL-
WATER J
r COLLECTION j "
SYSTEM'
"
L5GEND: . i Exposure pathway to receptor p3th«,au
X Exposure route was ' cannot be completed .--- Pathway
quantitatively evaluated , , K ». uncertain
O Exposure route was U Exposure route is highly unlikely
qualitatively addressed
S Safety issue- not addressed NOTES: - System includes leachate collection - trench
in risk assessment drains and water treatment plant
RECEPTOR
POTENTIAL / £&, g / /
EXPOSURE //'gjj? / £ * / & *
^r J^" ^f 1 *^^
i 1
INHALATION
INHALATION
INGESTION
DERMAL
CONTACT
INHALATION
INGESTION
DERMAL
CONTACT
INHALATION
INGESTION
DERMAL
CONTACT
DERMAL
CONTACT
VAPOR
INHALATION
INGESTION
DERMAL
CONTACT
L_JL_ L^_JL_JL_
T~x^ || x x
CJLJLJL- x
i "
rnr x x
r~5~" io_ ii °
r~u~n «
[~F~II x |Lj<
cm ii ° ii °
L u II u IL u
1 X II X ][ X
-H . 11 s - || s
H_L ii ir«~~
rr ii i T~T~I
r~r u . IL o
HERO VERM-1/M.G \HOME\DM\C\RSKC
RP
FIGURE 8 CONCEPTUAL MODEL OF POTENTIAL EXPOSURE ROUTES
-------
Table 6
Model for Calculating Doses through the
Incidental Ingestion of Soil
Soil Ingestion Dose CS * SIR * EF * ED
(mg/kg-day) = BW * AT
Where:
CS = Chemical concentration in surface soil (mg/kg)
SIR = Soil ingestion rate (kg/day)
EF = Exposure frequency (days/year)
ED = Exposure duration (years)
BW = Body weight (kg)
AT = Averaging time (days)
Exposure Assumptions
All Scenarios:
CS = Surface soil exposure concentrations presented in Table 3-2
Trespasser:
SIR = 5.0E-05 kg/day (U.S. EPA, 1994a)
EF = 1 day/week, 26 weeks/year
ED = 5 years
BW = 56 kg, average weight of a 12-to 18-year old (U.S. EPA, 1989a)
AT = 365 days/year x 5 years (for evaluating noncancer risk)
= 365 days/year x 70 years (for evaluating cancer risk)
Worker (Current and Future):
SIR = 5.0E-05 kg/day (U.S. EPA, 1991)
EF = 250 days/year (U.S. EPA, 1991)
ED = 25 years (U.S. EPA, 1991)
BW = 70 kg (U.S. EPA, 1991)
AT = 365 days/year x 25 years (for evaluating noncancer risk)
= 365 days/year x 70 years (for evaluating cancer risk)
-------
Table 7
Model for Calculating Doses through
Dermal Absorption from Soil
Soil Dermal Absorption Dose CS * SA * AF * ABS (or RABS^ * EF * ED
(mg/kg-day) = BW * AT
Where:
CS = Chemical concentration in surface soil (mg/kg)
SA = Skin surface area available for contact (cm2/day)
AF = Soil-to-skin adherence factor (kg/cm2)
ABS = Absorption factor (unitless)
RABS = Relative dermal absorption factor (unitless)
EF = Exposure frequency (days/year)
ED = Exposure duration (years)
BW = Body weight (kg)
AT = Averaging time (days)
Exposure Assumptions
All Scenarios:
CS = Surface soil exposure concentrations presented in Table 3-2
AF = l.OOE-06 kg/cm2, reasonable upper limit of soil adherence factor (U.S.
EPA, 1992a)
ABS = 0.03 for dioxin (U.S. EPA, 1992a)
RABS = 0.50 for all chemicals except dioxin, based on guidance in U.S. EPA, 1989c
Trespasser:
SA = 1,950 cm2/day, based on the average arm and hand surface area of a 12- to
18-year old (U.S. EPA, 1989a)
EF =1 day/week, 26 weeks/year
ED = 5 years
BW = 56 kg, average weight of a 12- to 18-year old (EPA, 1989a)
AT = 365 days/year x 5 years (for evaluating noncancer risk)
= 365 days/year x 70 years (for evaluating cancer risk)
-------
Table 7
Model for Calculating Doses through
Dermal Absorption from Soil
(continued)
Worker (Current and Future):
j*
SA = 2,000 cm2/day, based on the average arm and hand surface area of adult
males (U.S. EPA, 1989a)
EF = 250 days/year (U.S. EPA, 1991)
ED = 25 years (U.S. EPA, 1991)
BW = 70 kg (U.S. EPA, 1991)
AT = 365 days/year x 25 years (for evaluating noncancer risk)
= 365 days/year x 70 years (for evaluating cancer risk)
-------
Table 8
Model for Calculating Doses through the
Inhalation of Airborne Soil
Soil Inhalation Dose CS * RD * IV * EF * ED
(mg/kg-day) = BW * AT
Where:
CS = Chemical concentration in surface soil (mg/kg)
RD = Respirable-size soil particle concentration in air (i.e., PM10) (kg/m3)
IV = Inhalation volume (m3/day)
EF = Exposure frequency (days/year)
ED = Exposure duration (years)
BW = Body weight (kg)
AT = Averaging time (days)
Exposure Assumptions
All Scenarios:
CS = Surface soil exposure concentrations presented in Table 3-2
RD = 3.1E-08 kg/m3 (URS, 1990)
Trespasser:
IV = 2.5 m3/day, based on 1 hour of moderate activity on the site (U.S. EPA,
1989a)
EF =1 day/week, 26 weeks/year
ED = 5 years
BW = 56 kg, average weight of a 12- to 18-year old (U.S. EPA, 1989a)
AT = 365 days/year x 5 years (for evaluating noncancer risk)
= 365 days/year x 70 years (for evaluating cancer risk)
-------
Table 8
Model for Calculating Doses through the
Inhalation of Airborne Soil
(continued)
Worker (Current and Future):
IV = 20 m3/day (U.S. EPA, 1991)
EF = 250 days/year (U.S. EPA, 1991)
ED = 25 years (U.S. EPA, 1991)
BW = 70 kg (U.S. EPA, 1991)
AT = 365 days/year x 25 years (for evaluating noncancer risk)
= 365 days/year x 70 years (for evaluating cancer risk)
-------
Table 9
Model for Calculating Doses through the
Inhalation of Vapors
Vapor Inhalation Dose CA * IV * EF * ED
(mg/kg-day) = BW * AT
Where:
CA = Chemical vapor concentration in air (mg/m3)
IV = Inhalation volume (m3/day)
EF = Exposure frequency (days/year)
ED = Exposure duration (years)
BW = Body weight (kg)
AT = Averaging time (days)
Exposure Assumptions
All Scenarios:
CA = Vapor concentrations presented in Table 3-2
Trespasser:
IV = 2.5 m3/day, based on 1 hour of moderate activity on the site (U.S. EPA,
1989a)
EF = 1 day/Seek, 26 weeks/year
ED = 5 years
BW = 56 kg, average weight of a 12- to 18-year old (U.S. EPA, 1989a)
AT = 365 days/year x 5 years (for evaluating noncancer risk)
= 365 days/year x 70 years (for evaluating cancer risk)
Worker (Current and Future):
IV = 20 m3/day (U.S. EPA, 1991)
EF = 250 days/year (U.S. EPA, 1991)
ED = 25 years (U.S. EPA, 1991)
BW = 70 kg (U.S. EPA, 1991)
AT = 365 days/year x 25 years (for evaluating noncancer risk)
= 365 days/year x 70 years (for evaluating cancer risk)
-------
Table 10
Model for Calculating Doses through
Dermal Absorption from Surface Water
Surface Water
Dermal Absorption Dose = CSW * CF-1 * SA * PC * ET * CF-2 * EF * ED
(mg/kg-day) BW * AT
Where:
CSW = Chemical concentration in surface water (mg/L)
CF-1 = Conversion factor (mg//jg)
SA = Skin surface area available for contact (cm2)
PC = Dermal permeability coefficient (cm/hour)
ET = Exposure time (hours/day)
CF-2 = Conversion factor (L/cm3)
EF = Exposure frequency (days/year)
ED = Exposure duration (years)
BW = Body weight (kg)
AT = Averaging time (days)
Exposure Assumptions
All Scenarios:
CF-1 = 1 rag/1,000 u%
PC = Permeability coefficient, presented in Table 3-9
CF-2 - 1 L/1,000 cm3
Trespasser:
CSW = Surface water exposure concentrations for Rocky Branch Creek, presented
in Table 3-2
SA = 1,970 cm2, average hand and foot surface area of a 12- to 18-year old (U.S.
EPA, 1989a)
ET = 1 hour/day
EF = 1 day/week, 13 weeks/year
ED = 5 years
BW = 56 kg, average weight of a 12- to 18-year old (U.S. EPA, 1989a)
AT = 365 days/year x 5 years (for evaluating noncancer risk)
= 365 days/year x 70 years (for evaluating cancer risk)
-------
Table 10
Model for Calculating Doses through
Dermal Absorption from Surface Water
(continued)
Worker (Current and Future):
CSW = Surface water exposure concentrations based on all surface waters,
presented in Table 3-2
SA = 840 cm2, average hand surface area of an adult (U.S. EPA, 1989a)
ET = 1 hour/day
EF = 1 day/week, 50 weeks/year (U.S. EPA, 1991)
ED = 25 years (U.S. EPA, 1991)
BW = 70 kg (U.S. EPA, 1991)
AT = 365 days/year x 25 yean ^or evaluating noncancer risk)
= 365 days/year x 70 years (for evaluating cancer risk)
-------
Table 11
Model for Calculating Doses through the
Ingestion of Groundwater
Groundwater Ingestion Dose CGW * GIR * EF * ED
(mg/kg-day) = BW * AT
Where:
CGW =
GIR =
EF =
ED =
BW =
AT =
Chemical concentration in groundwater (mg/L)
Groundwater ingestion rate (L/day)
Exposure frequency (days/year)
Exposure duration (years)
Body weight (kg)
Averaging time (days)
Exposure Assumptions
Worker (Future):
CW = Groundwater exposure concentrations presented in Table 3-2
IR = 1 L/day (U.S. EPA, 1991)
EF = 250 days/year (U.S. EPA, 1991)
ED = 25 years (U.S. EPA, 1991)
BW = 70 kg (U.S. EPA, 1991)
AT = 365 days/year x 25 years (for evaluating noncancer risk)
= 365 days/year x 70 years (for evaluating cancer risk)
-------
chronic, subchronic, or lifetime). Thus, a full description of
the toxic effects of a chemical includes a listing of what
adverse health effects the chemical may cause (carcinogenic and
noncarcinogenic), and how the occurrence of these effects depends
upon dose, route, and duration of exposure.
Slope factors (SF's) have been developed by EPA for
estimating excess lifetime cancer risks associated with exposure
to potentially carcinogenic contaminants of concern. Sf's, which
are expressed in units of (mg/kg-day)"1, are multiplied by the
estimated intake of a potential carcinogen, in mg/kg-day, to
provide an upper-bound estimate of the excess lifetime cancer
risk associated with exposure at that intake level. The term
"upper bound" reflects the conservative estimate of the risks
calculated from the SF. Use of this approach makes
underestimation of the actual cancer risk 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.
References doses (RfDs) have been developed by EPA for
indicating the potential for adverse health effects from exposure
to contaminants of concern exhibiting non-carcinogenic adverse
health effects. RfD's which are expressed in units of mg/kg-day,
are estimates of daily (maximum) exposure levels for the human
population, including sensitive subpopulations. Estimated
intakes of contaminants of concern from environmental media
(e.g., the amount of chemical ingested from drinking contaminated
ground water) can be compared to the RfD. RfD's are derived from
human epidemiological studies or animal studies to which
uncertainty factors have been applied to account for the use of
animal data to predict effects on humans.
Toxicity information used to calculate the risk for
carcinogenic risk including the slope factor, the weight of
evidence, and source of the toxicity information can be found in
Tables 12 and 13. Chronic and subchronic references doses used
in the toxicity assessment can be found in Tables 14 and 15.
In numerous public forums over the past year, EPA has
summarized the preliminary results from the dioxin reassessment
study in order to accept public comment during the scientific
peer review process. One of the major conclusions was that the
"weight-of-evidence" suggested that dioxin, furans, and dioxin
like compounds are likely to present a cancer hazard to humans,
and that a risk specific dose of dioxin at 0.01 pico grams (pg)
TEQ per kilogram (kg) of body weight per day, resulted in one
additional cancer in one million. This risk specific dose
estimate represents a plausible upper bound on risk based on the
evaluation of both animal and human data. With regards to
average intake, humans are currently exposed to background levels
52
-------
Table 12
U.S. EPA and IARC Categorizations of the Carcinogenic
Substances of Potential Concern
Substance
EPA
Carcinogenicity
Category*1''
IARC
Carcinogenicity
Category^
Organics
Chloroform
Methylene chloride
2,3,7,8-TCDD
2,4,6-Trichlorophenol
B2
C
B2
B2
2B
2B
2B
NC
Inorganics
Arsenic
Lead
A
B2
1
2B
'References: IRIS, 1995; U.S. EPA, 1994b
"Category definitions (U.S. EPA, 1986b):
A = Human carcinogen (sufficient evidence from epidemiologic studies).
B2 = Probable human carcinogen (sufficient evidence from animal studies and inadequate or no human
data).
C = Possible human carcinogen (limited evidence from animal studies and no human data)
"Reference- WHO, 1987
"Category detinition (WHO, 1987):
1 = Human carcinogen (sufficient evidence of Carcinogenicity in humans).
2B = Possible human carcinogen (limited evidence of Carcinogenicity in humans in the absence of
sufficient evidence of Carcinogenicity ir experimental animals; inadequate evidence of Carcinogenicity
in humans or no human data and sufficient evidence of Carcinogenicity in experimental animals; or
inadequate evidence of Carcinogenicity or no data in humans and limited evidence of Carcinogenicity
in experimental animals, with supporting evidence from other relevant data).
NC = Not categorized.
-------
Table 13
Cancer Slooe Factors
Substance
Inhalation
Slope Factor
(mg/kg-day)-1
Reference
or Basis
Oral Slope
Factor
(mg/kg-day)-1
Reference
or Basis
Dermal Slope
Factor*
(mg/kg-day)-1
Organics
Chloroform
Methylene chloride
2,3,7,8-TCDD
2,4,6-
Trichlorophenol
NC
NC
1.5E+05
9.7E+03
l.lE-02b
U.S. EPA,
1994b
OSF
IRIS, 1995
6.1E-03
7.5E-03
1.5E+05
9.7E+03
1.1E-02
IRIS, 1995
IRIS, 1995
U.S. EPA,
1994b
ChemRisk,
1990
IRIS, 1995
NC
NC
3.0E+05
1.9E + 04
2.2E-02
Inorganics
Arsenic
Lead
NC
NC
1.75E+00C
NTV
IRIS, 1995
-
NC
NC
"Dermal slope factors were derived from the oral slops factors as described in Subsection 3.3.2.3.
"Derived from a unit risk, assuming the inhalation of 20 m3 of air per day and a body weight of 70 kg (U.S. EPA,
1994b).
T)erived from a unit risk, assuming the consumption of 2 liters of water per day and a body weight of 70 kg
(U.S. EPA, 1994b).
NC = Substance is not of concern through this exposure route.
NTV = A toxicity value was not available.
OSF = Oral slope factor was used (Subsection 3.3.2.2).
-------
Table 14
Chronic Reference Doses (RfDs)
Substance
Inhalation RfD
(mg/kg-day)
Organics
Acetone
Chloroform
2-Chlorophenol
4-ChIorophenol
2,4-D
2,6-D
2, V-Dichlorophenyl
2,6-Dichiorophenyl
Methylene chloride
Phenol
Silvex
2,4,5-T
2,4,6-T
2,3,7,8-TCDD
Tetrachlorobenzene
Toluene
2 3,6-Trichlorophenol
NC
NC
5.0E-03
NC
l.OE-02
NC
3.0E-03
3.0E-03
NC
NC
8.0E-03
l.OE-02
NC
NTV
3.00E-04"
NC
NC
Reference
or Basis
ORD
ORD
ORD
ORD
ORD
ORD
ORD
Oral RfD
(mg/kg-day)
Reference
or Basis
Dermal RfD1
(mg/kg-day)
l.OE-01
l.OE-02
5.0E-03
5.0E-03
l.OE-02
l.OE-02
3.0E-03
3.0E-03
6.0E-02
6.0E-01
8.0E-03
l.OE-02
l.OE-02
NTV
3.0E-04C
2.0E-01
l.OE-01
IRIS, 1995
IRIS, 1995
IRIS, 1995
Isomer
IRIS, 1995
Isomer
IRIS, 1995
Isomer
IRIS, 1995
IRIS, 1995
IRIS, 1995
IRIS, 1995
Isomer
IRIS, 1995
IRIS, 1995
Isomer
NC
NC
4.5E-03 (dw)
4.5E-03 (dw)
5.0E-C3 (d)
5.0E-03(d)
2.7E-03 (dw)
2.7E-03 (dw)
NC
5.4E-01 (g)
4.0E-03 (d)
5.0E-03 (d)
5.0E-03(d)
NTV
NC
1.8E-01 (g)
5.0E-02 (d)
-------
Table 14
Chronic Reference Doses (RfDs)
(continued)
Substance
Inhalation RfD
(mg/kg-day)
Reference
or Basis
Organics (continued)
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
l.OE-01
l.OE-01
Inorganics
Antimony
Arsenic
Chromium
Copper
Lead
Mercury
Nickel
Silver
Thallium
Zinc
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
ORD
ORD
Oral RfD
(mg/kg-day)
Reference
or Basis
Dermal RfD*
(mg/kg-day)
l.OE-01
l.OE-01
IRIS, 1995
Isomer
5.0E-02 (d)
5.0E-02 (d)
4.0E-04
3.0E-04
5.0E-03d
3.7E-02'
NTV
3.0E-04
2.0E-02
5.0E-03
MTV
3.0E-01
IRIS, 1995
IRIS, 1995
IRIS, 1995
U.S. EPA, 1994b
U.S. EPA, 1994b
IRIS, 1995
IRIS, 1995
IRIS, 1995
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
"Chronic dermal RfDs were calculated from the chronic oral RfDs as described in Subsection 3.3.3.3. The rorte by which the chemical was administered
in the studies on which the oral RfD was based is indicated in parentheses as follows:
d = diet
dw = drinking water
g = gavage
The inhalation RfD was used only in the hot spot analysis (Subsection 3.5).
-------
Table 14
Chronic Reference Doses (RfDs)
(continued)
^Value is for 1,2,4,5-tetrachlorobenzene, the only RfD available for a tetrachlorobenzene.
dValue is for chromium VI (Subsection 3.3.3.1).
'Derived from the current drinking water standard, assuming the consumption of 2 liters of water per day rnd a body weight of 70 kg (U.S. EPA, 1994b).
'RfDs were available only for specific thallium salts. Because the speciation of thallium in media samples is not known, an RfD was not selected.
NC = Substance is not of concern through this exposure route.
NTV = A toxicity value was not available.
ORD = The oral RfD was used.
-------
Table 15
Subchronic Reference Doses (RfDs)
Substance
Inhalation RfD
(mg/kg-day)
Reference
or Basis
Organics
Acetone
Chloroform
2-Chlorophenol
4-Chlorophenol
2,4-D
2,6-D
2,4-Dichlorophenyi
2,6-Dichlorophenyl
Methylene chloride
Phenol
Silvex
2,4,5-T
2,4,6-T
2,3,7,8-TCDD
Tetrachlorobenzene
Toluene
2,3,6-Trichlorophenol
NC
NC
5.0E-02
NC
l.OE-02
NC
3.0E-03
3.0E-03
NC
NC
8.0E-03
l.OE-01
NC
NTV
NC
NC
NC
ORD
ORD
ORD
ORD
ORD
ORD
Oral RfD
(mg/kg-day)
Reference
or Basis
Dermal RfD"
(mg/kg-day)
NC
NC
5.0E-02
5.0E-02(D)
l.OE-02
l.OE-02
3.0E-03
3.0E-03
NC
6.0E-01(D)
8.0E-03
l.OE-01
l.OE-01
NTV
NC
2.0E + 00(D)
l.OE + 00
U.S. EPA, 1994b
Isomer
U.S. EPA, 1994b
Isomer
U.S. EPA, 1994b
Isomer
U.S. EPA, 1994b
U.S. EPA, 1994b
U.S. EPA, 1994b
Isomer
U.S. EPA, 1994b
Isomer
NC
NC
4.5E-02 (dw)
4.5E-02 (dw)
5.0E-03 (d)
5.0E-03(d)
2.7E-03 (dw)
2.7E-03 (dw)
NC
5.4E-01 (g)
4.0E-03 (d)
5.0E-02 (d)
5.0E-02(d)
NTV
NC
1.8E + 00 (g)
5.0E-01(d)
------- An error occurred while trying to OCR this image.
-------
of dioxin-like compounds on the order of 3-6 TEQ's pg/kg/day.
Therefore, plausible upper-bound risk estimates for general
population exposures to dioxin and related compounds (at
background levels) may be as high as 1 in 10,000 (1X10"4) to 1 in
1,000 (1X10"3) . High end estimates of body burden of individuals
in the general population (approximately the top 10% of the
general population) may be greater than 3 times higher.
What should also be noted here is that the risk calculations
presented in the baseline risk assessment (and reported in this
summary) for dioxin are based on exposure to 2,3,7,8-TCDD only.
Additional sampling performed by the PRP at the request of EPA
shows that other dioxin and furan compounds are present at the
site, and could contribute to approximately 20 percent greater
risk than TCDD alone, i.e., the risk estimates presented could be
adjusted upward by 20 percent.
It is also important to note that the non-cancer risks
outlined in the baseline risk assessment and summarized here do
not address the non-cancer risks associated with low level
exposures to dioxin. As a result, the baseline risk assessment
may underestimate the non-cancer risk associated with exposure to
site contaminants. The reason being is that a reference dose
(the daily intake of a chemical to which an individual can be
exposed without experiencing non-cancer health effects) has not
been established by EPA for dioxin at this time. If a reference
dose were to be calculated for dioxin based on human and animal
data, it could result in an acceptable intake level for humans
below the current level of daily intake in the general
population. EPA's dioxin reassessment study has suggested that
at some dose, and possibly within one order of magnitude of
average background body burdens, dioxin exposure can result in
nonca--~r health effects in humans. These effects include
developmental and reproductive effects, immune suppression, and
disruption of regulatory hormones.
6.3.4 Risk Characterization
Cancer Risk
The risk of getting cancer from exposure to a chemical is
described in terms of probability that an individual exposed for
his or her entire lifetime will develop cancer by the age 70.
For carcinogens, risks are estimated as the incremental
probability of an individual developing cancer over a lifetime as
a result of exposure to the carcinogen. Excess lifetime cancer
risk is calculated using the following equation:
Cancer Lifetime Cancer
60
-------
Risk = Averaged x Slope
Dose Factor
(mg/kg-day) (mg/kg-day) ~l
These risks are probabilities that are generally expressed
in scientific notation (e.g., 1 x 10"6 or IE) . An excess
lifetime cancer risk of 1 x 10"6 indicates that, as a reasonable
maximum estimate, an individual has a 1 in 1,000,000 chance of
developing cancer as a result of site related exposure t^ *
carcinogen over a 70-year lifetime under the specific exposure
conditions at a site.
Tables 16, 17, and 18 summarize the potential lifetime
cancer risk for the three exposure scenarios examined in the risk
assessment.
The calculated excess lifetime cancer risk for the
trespasser scenario was 8X10"5 or approximately 8 in 100,000.
The exposure routes that posed the majority of the risk to the
trespasser were through dermal absorption from surface water,
incidental soil ingestion, and dermal contact with soil. TCDD
dioxin was the only contaminant that contributed to an excess
cancer risk greater that 1X10"6.
The calculated excess lifetime cancer risk for the current
unprotected worker scenario based on all exposure routes was
approximately 1 in 1,000 or 1X10"3. This risk exceeds EPA's
acceptable risk range. The exposure routes that posed the
majority of the risk to the current unprotected worker were
through dermal contact with soil (6X10~4), dermal contact with
surface waters (5X10"4) , and incidental soil ingestion (2X10~4) .
The calculated excess lifetime cancer risk for the future
unprotected worker scenario based on all exposure routes was
approximately 5 in 100 or 5X10"2. This risk exceeds EPA's
acceptable risk range. The exposure routes that posed the
majority of the risk to the future unprotected worker were
through soil ingestion (2X10"4) , dermal contact with soil (6X10"
4) , dermal contact with surface water (5X10"4) , and ground water
ingestion (5X10"2) .
Over 99 percent of the calculated risk for all exposure
scenarios was contributed by 2,3,7,8-TCDD. As mentioned earlier,
when all dioxin and furan congeners are factored into the risk
estimates, those estimates may be 20 percent higher.
Non-cancer Risk
The potential for non-carcinogenic effects is evaluated by
comparing an exposure level over a specified time period (e.g.,
61
-------
TABLE 16
POTENTIAL LIFETIME CANCER RISK
TRESPASSER
SUBSTANCE
2,3,7,8-TCDD (U.S. EPA)
(ChemRisk)
2,4,6-Trichlorophenol
TOTAL (U.S. EPA)
TOTAL (ChemRisk)
SOIL
INGESTION
6 27E-06
4.05E-07
1.70E-10
6.27E-06
4.06E-07
DERMAL
ABSORPTION
FROM SOIL
1.47E-05
9.29E-07
3.31E-09
1.47E-05
9.32E-07
SOIL
INHALATION
9.72E-09
6.28E-10
2.63E-13
9.72E-09
6.29E-1u
VAPOR
INHALATION
1.94E-10
1.26E-11
2.50E-14
1.94E-10
1.25E-11
DERMAL
ABSORPTION
FROM SURFACE
WATER
6.39E-05
4.05E-06
4.41E-10
6.39E-05
4.05E-06
TOTAL
8.48E-05
5.38E-06
3.92E-09
TOTAL LIFETIME
CANCER RISK (U.S. EPA) 8.49E-05
TOTAL LIFETIME
CANCER RISK (ChemRisk) 5 39E-06
-------
TABLE 17
POTENTIAL LIFETIME CANCER RISK
CURRENT UNPROTECTED WORKER
SUBSTANCE
2,3,7,8-TCDD (U.S. EPA)
(ChemRisk)
2,4,6-Trichlorophenol
TOTAL (U.S. EPA)
TOTAL (ChemRisk)
SOIL
INGESTION
2.41E-04
1.56E-05
6.53E-09
2.41E-04
1.56E-05
DERMAL
ABSORPTION
FROM SOiL
5.79E-04
3.67E-05
1.31E-07
5.79E-04
3.68E-05
SOIL
INHALATION
2.99E-06
1.93E-07
8.10E-11
2.99E-06
1.93E-07
VAPOR
INHALATION
5.98E-08
3.86E-09
7.69E-12
5.98E-08
3.87E-09
DERMAL
ABSORPTION
FROM SURFACE
WATER
4.68E-04
2.97E-05
1.14E-06
4.70E-04
3.08E-05
TOTAL
1.29E-03
8.21E-05
1.28E-06
TOTAL LIFETIME
CANCER RISK (U.S. EPA) 1.29E-03
TOTAL LIFETIME
CANCER RISK (ChemRisk) 8.34E-05
-------
TABLE 18
POTENTIAL LIFETIME CANCER RISK
FUTURE UNPROTECTED WORKER
SUBSTANCE
Chloroform
Methytene chloride
2,3,7,8-TCDD (U.S. EPA)
(ChemRisk)
2,4,6-Trichlorophenol
Arsenic
Lead
TOTAL (U.S. EPA)
TOTAL (ChemRisk)
SOIL
INGESTION
NA
NA
2.41E-04
1.56E-05
6.53E-09
NA
NA
2.41E-04
1.56E-05
DERMAL
ABSORPTION
FROM SOIL
NA
NA
5.79E-04
3.67E-05
1.31E-07
NA
NA
5.79E-04
3.68E-05
SOIL
INHALATION
NA
NA
2.99E-06
1.93E-07
8.10E-11
NA
NA
2.99E-06
1.93E-07
VAPOR
INHALATION
NA
NA
5.98E-08
3.86E-09
7.69E-12
NA
NA
5.98E-08
3.87E-09
DERMAL
ABSORPTION
FROM SURFACE
WATER
NA
NA
4.68E-04
2.97E-05
1.14E-06
NA
NA
4.70E-04
3.08E--05
GROUNDWATER
INGESTION
1.51E-07
3.41E-07
5.08E-02
3.29E-03
3.81E-04
3.4 ;E-05
NTV
5.13E-02
3.70E-03
TOTAL
1.51E-07
3.41 E-07
5.21E-02
3.37E-03
3.82E-04
3.42E-05
NTV
TOTAL LIFETIME
CANCER RISK (U.S. EPA) 5.26E-02
TOTAL LIFETIME
CANCER RISK (ChemRisk) 3.79E-03
NA - Not applicable. Chemical is not of concern through this exposure route.
_ Not calculated because a slope factor was not available.
-------
lifetime) with a reference dose derived for a similar exposure
period. The ratio of exposure to toxicity is called the hazard
quotient. By adding the hazard quotients for all contaminants of
concern which affect the same target organ (e.g., the liver)
within a medium or across all media to which a population may
reasonably be exposed, the Hazard Index (HI) can be generated.
In general, a total hazard index of 1 is used as a benchmark of
potential concern for non-cancer health effects.
Hazard Daily Reference
Quotient = Intake -=- Dose
Tables 19, 20t and 21 summarize the hazard quotients and indices
calculated for the same potentially exposed individuals.
The total hazard index calculated for contaminants of
concern other than dioxin for a trespasser was approximately 0.4,
based on soil ingestion, soil inhalation, dermal contact with
soil, and dermal contact with surface water. Again, the
benchmark of concern for non-cancer health effects is 1. A total
hazard index of approxima' sly 4 was calculated for the current
unprotected worker with dermal contact with 2,4-D contributing
most of the risk. For the future unprotected worker a hazard
index of 5,520 was calculated. The ground water ingestion
pathway contributed most to the non-cancer risk for the future
unprotected worker. Again, in this ROD EPA did not consider the
ground water ingestion exposure route in developing the
remediation goals for this site, because drinking water for the
Jacksonville area is provided from sources near Little Rock, and
it is doubtful that any wells on this property will ever be used
for domestic purposes.
6.3.5 Uncertainty Analysis
Within the Superfund process, baseline risk assessments are
developed to provide risk managers a numerical representation of
the severity of contamination present at a site, as well as to
provide an indication of the potential for adverse public health
effects. There are many inherent and imposed uncertainties in
the risk assessment process. Some of these uncertainties may
lend in the underestimation of site risk others in its
overestimation.
Factors that Tend to Underestimate Exposure/Risk
Lack of RfDs or Sfs for all chemicals of concern;
Nonquantification of some exposure pathways;
Exclusion of chemicals present but not detected;
65
-------
TABLE 19
HAZARD QUOTIENTS AND INDICES
TRESPASSER
SUBSTANCE
2-Chlorophenol
4-Chlorophenol
2,4-0
2,6-D
2,4-Dichlorophenol
2,6-Dichlorophenol
Phenol
Silvex
2,4,5-T
2,4,6-T
2,3,7,8-TCDD
Tetrachlorobenzene
Toluene
2,3,6-Trichlorophenol
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
HAZARD INDEX (BY EXPOSURE ROUTE)
SOIL
INGESTION
4.96E-07
NA
1.97E-02
NA
1.06E-04
1.40E-05
NA
8.75E-04
1.59E-04
NA
NTV
NA
NA
NA
1.91E-07
2.16E-07
2.09E-02, _ . ,
~
DERMAL
ABSORPTION
FROM SOIL
9.67E-06
NA
3.84E-01
NA
2.07E-03
2.73E-04
NA
1.71E-02
3.10E-03
NA
NTV
NA
NA
NA
3.72E-06
4.22E-06
4.07E-01
SOIL
INHALATION
7.69E-10
NA
3.06E-05
NA
1.64E-07
2.17E-08
NA
1.36E-06
2.46E-07
NA
NTV
NA
NA
NA
2.96E-10
3.35E-10
3.23E-05
VAPOR
INHALATION
1.34E-10
NA
NC
NA
3.60E-08
6.04E-09
NA
5.96E-09
3.18E-09
NA
NTV
NA
NA
NA
5.09E-10
3.18E-11
5.19E-08
DERMAL
ABSORPTION
FROM SURFACE
WATER
=======?02f^06'
1.60E-05
2.75E-04
8.68E-05
3.62E-04
2.22E-05
4.38E-08
9.96E-05
2.76E-05
1.55E-05
NTV
NA
5.01 E-07
2.85E-07
1.58E-06
5.62E-07
9.10E-04
HAZARD INDEX
(BY
SUBSTANCE)
1.22E-05
1.60E-05
4.04E-01
8.68E-05
2.54E-03
3.09E-04
4.38E-08
1.80E-02
3.29E-03
1.55E-05
NTV
NA
5.01E-07
2.85E-07
5.49E-06
5.00E-06
TOTAL HAZARD INDEX 4.29E-01
NA - Not applicable. Chemical is not of concern through this exposure route.
NC - Not calculated because an exposure concentration could not be determined (Appendix E).
NTV - Not calculated because an RfD was not available.
-------
TABLE 20
HAZARD QUOTIENTS AND INDICES
CURRENT UNPROTECTED WORKER
SUBSTANCE
2-Chlorophenol
4-Chlorophenol
2,4-D
2,6-D
2,4-Dichlorophenol
2,6 - Dichlorophenol
Phenol
Silvex
2,4,3-T
2,4,6-T
2,3,7,8-TCDD
Tetrachlorobenzene
Toluene
2,3,6-Trichlorophenol
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
HAZARD INDEX (BY EXPOSURE ROUTE)
SOIL
INGESTION
3.82E-05
NA
1.52E-01
NA
8.15E-04
1.08E-04
NA
6.73E-03
1.22
-------
TABLE 21
HAZARD QUOTIENTS AND INDICES
FUTURE UNPROTECTED WORKER
SUBSTANCE
Acetone
Chloroform
2-Chlorophenol
4-Chlorophenol
2,4-D
2,6-D
2,4-D ichlorophenol
2,6-Dichlorophenol
Methylene chloride
Phenol
Silvex
2,4,5- F
2,4,6-T
2,3,7,8-TCDD
Tefrachlorobenzene
Toluene
2,3,6-Trichlorophenol
2 ,4,5 - Trichlorophenol
2.4,6-Trichlorophenol
Antimony
Arsenic
Chromium
Copper
Lead
Mercury
Nickel
Silver
Thallium
Zinc
HAZARD INDEX (BY EXPOSURE ROUTE)
SOIL
INGESTION
NA
NA
3.82E-05
NA
1.52E-01
NA
8.15E-04
1.08E-04
NA
NA
6.73E-03
1.22E-02
NA
NTV
NA
NA
NA
1.47E-05
1.66E-05
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
1.72E-01
DERMAL
ABSORPTION
FROM SOIL
NA
NA
7.63E-04
NA
3.03E+00
NA
1.63E-02
2.15E-03
NA
NA
1.35E-01
2.45E-01
NA
NTV
NA
NA
NA
2.94E-04
3.33E-04
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
3.43E+00
SOIL
INHALATION
NA
NA
4.73E-07
NA
1.88E-03
NA
1.01E-05
1.33E-06
NA
NA
8.34E-05
1.52E-04
NA
NTV
NA
NA
NA
1.82E-07
2.06E-07
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
2.13E-03
VAPOR
INHALATION
NA
NA
8.22E-08
NA
NC
N i
2.22E-06
3.72E-07
NA
NA
3.67E-07
1.96E-06
NA
NTV
NA
NA
NA
3.13E-07
1.96E-08
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
5.33E-06
DERMAL
ABSORPTION
FROM SURFACE
WATER
NA
NA
5.06E-03
1.16E-01
4.72E-02
1.50E-02
2.48E-01
3.09E-03
NA
1.55E-05
1.20E-02
3.98E-02
7.99E-02
NTV
NA
1.60E-03
2.24E-05
8.61 E-03
2.91 E-03
NA
NA
NA
' NA
NA
NA
NA
NA
NA
NA
5.79E-01
GROUNDWATER
INGESTION
1.57E-03
6.95E--03
3.13E+01
1.19E+02
1.57E+03
1.08E+03
1.89E+03
8.15E+01
2.12E-03
1.24E-01
1.35E+02
3.72E+02
2.05E+02
NTV
3.26E+00
2.15E+01
9.30E-03
1.27E+01
9.69E-01
7.09E-01
1.83E-01
1.08E-02
3.70E-03
NTV
1.01E-02
2.40E-02
1.17E-02
NTV
2.05E-03
5.52E+03
HAZARD INDEX
(BY
SUBSTANCE)
1.57E-03
6.95E-03
3.13E+01
1.19E+02
1.57E+03
1.08E+03
1.89E + 03
8.15E+Q1
2.12E-03
1.24E-01
1.35E+02
3.72E+02
2.06E+02
NTV
3.26E+00
2.15E+01
9.32E-03
1.27E+01
9.72E-01
7.09E-01
1.83E-01
1.08E-02
3.70E-03
NTV
1.01E-02
2.40E-02
1.17E-02
NTV
2.05E-03
TOTAL HAZARD INDEX 5.52E+03
NA - Not applicable. Chemical is not of concern through this exposure route.
NC - Not calculated because an exposure concentration could not be determined (Appendix E).
NTV - Not calculated because an RfD value was not available.
-------
Factors that Tend to Overestimate Exposure/Risk;
Use of conservative exposure assumptions;
Use of conservative RfD's or Sf's;
Factors that could either Over or Underestimate
Exposure/Risk;
Use of 1/2 the detection limit; and
Possible occurrence of hotspots.
6.3.6 Central Tendency Exposure
In February 1992 a guidance memorandum from the Deputy
Administrator of EPA required that all Superfund risk assessments
evaluate both reasonable maximum exposure (RME) and central
tendency exposures. Exposure assumptions in the ROD up to this
section have been based on RME. The central tendency scenario
represents the risk from more of an "average" exposure (see
Table 22).
6.4 ECOLOGICAL RISK ASSESSMENT
The objective of the ecological risk assessment is to
identify and estimate the potential for adverse ecological
effects to terrestrial and aquatic flora and fauna from exposure
to hazardous substances found in the soil and surface waters at
the Vertac site, including Rocky Branch Creek. An ecological
risk assessment is subject to a wide variety of uncertainties.
Virtually ever step in the risk assessment process involves
numerous assumptions that contribute to the total uncertainty in
the final evaluation of risk. The uncertainty incorporated in
this assessment may result in an increase or decrease of the
estimation of potential ecological risks. However, when
possible, conservative approaches are used in uncertain
situations. The conservative method tends to increase the
estimated risk and therefore is protective of ecological
resources. The substance of potential concern concentration
data, exposure assessment factors, and toxicity value selection
are the major contributors to uncertainty in the risk assessment.
Therefore, the ecological risk assessment for the OU3 media used
conservative, yet realistic, assumptions.
In general, the approach for conducting the ecological risk
assessment parallels that used in the human health risk
assessment. Habitats and organisms potentially affected by site-
related chemicals were identified. For some organisms, the risk
estimated was due to direct exposure to site chemicals, such as
through ingestion of site surface water, and for other organisms
simple models were used to determine exposure to site
69
-------
TABLE 22
Summary of Potential Cancer Risks and Hazard Indices"
Central Tendency Case
Scenario
Trespasser
Current Unprotected Worker
Future Unprotected Worker
Total Lifetime Cancer Riskb
4E-06 (ChemRisk)
7E-05 (U.S. EPA)
IE-OS (ChemRisk)
2E-04 (U.S. EPA)
2E-04 (ChemRisk)
2E-03 (U.S. EPA)
Total Hazard Index
2E-02
2E-01
2E + 03
"Values are rounded to one significant figure.
"ChemRisk = Cancer risk was calculated using the slope factor for 2,3,7,8-TCDD developed by ChemRisk.
U.S. EPA = Cancer risk was calculated using the slope factors for 2,3,7,8-TCDD developed by U.S. EPA.
-------
contaminants through indirect exposure routes, such as eating
contaminated vegetation. The potential for effects to occur was
evaluated by comparing benchmark criteria, such as acceptable
daily intakes to estimated exposures. This comparison resulted
in the calculation of hazard quotients. In general, a hazard
quotient greater than 1 indicated a potential for impacts to
occur as a result of exposure to a particular chemical.
Potential ecological risks were evaluated for two mammalian
species and three avian species. The potential for adverse
ecological effects on aquatic fauna of the Rocky Branch Creek
were also estimated. The results of the ecological risk
assessment showed that each of the organisms evaluated had a
hazard index exceeding the benchmark of 1. The total hazard
indices for the ecological receptors evaluated ranged between 3.4
and 54.
While this data suggest that dioxin contaminated sediments
in Rocky Branch Creek have resulted in ecological impacts, until
the site is remediated and the source of dioxin contamination
eliminated, the potential for continuing impacts exists through
contaminated surface soils, sediment transport and groundwater
seeps. However, with the OU2 remedy, the primary source will be
removed through consolidation of dioxin contaminated soils in an
on-site landfill and sediment transport resulting from the sump
overflows and storm water runon/runoff will be reduced or
eliminated through storm water management.
Groundwater seeps from the contaminated areas of the site
into Rocky Branch Creek are currently impeded by the French Drain
system installed along the western edge of the site and bordering
the on-site burial grounds, thereby preventing another potential
source of contamination for Rocky Branch Creek. Stream data
indicate no measurable dioxin concentrations, for example,
following rain events. Since Rocky Branch Creek is not a
perennial waterbody and does not flow through the site, the
removal of the contaminated soils and elimination of untreated
discharges and possible groundwater seeps will essentially
eliminate future impacts. While data suggest that existing
impacts in Rocky Branch Creek are on the decline, any actions to
remove contaminated sediments in Rocky Branch Creek would be cost
prohibitive, but more importantly, any disturbance of the
existing sediment could prove catastrophic, possible even
destroying the entire existing ecosystem. As such, this remedy
in addition to the other on-going remedies at the site will
effectively remove the contamination source and the storm water
transport concern allowing Rocky Branch Creek to continue, in
essence, a natural attenuation process.
In addition to the Ecological Risk Assessment, fish tissue
data collected for TCDD from the Rocky Branch Creek/Bayou Meto
watershed areas near the site suggest that contaminants of
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concern continue to pose an actual threat to local ecological
receptors. EPA issued a ROD in September 1990 addressing the
Vertac off-site areas. One of the ROD requirements was to
monitor fish in the streams for dioxin and continue the ban on
commercial fishing and the advisory that discouraged sport
fishing as long as fish tissue dioxin levels are above Food and
Drug Administration (FDA) alert levels. FDA issued a health
advisory stating that fish with 2,3,7,8-TCDD > 50 parts per
trillion (ppt) should not be consumed, and levels below 25 ppt
pose no serious health threat. Based on this guidance, the
Arkansas Department of Health (ADH) has established an advisory
level of 25 ppt in fish flesh. The current advisory encompasses
Bayou Meto from Arkansas Highway 13, upstream to the mouth of the
discharge from Jacksonville West Wastewater Treatment ponds,
including Rocky Branch Creek and Lake Dupree.
Based on 1994 fish tissue sampling results, dioxin
concentrations appeared to generally decrease with increasing
distance from the site. The highest dioxin concentrations were
found in Big Mouth Buffalo from Rocky Branch Creek and Bayou Meto
upstream of Hwy 67-167. The concentrations found were 73 ppt and
94 ppt as TCDD TEQ's, respectively. Concentrations of TCDD for
White Crappie at the Rocky Branch Creek location was 26 ppt, and
19 ppt for Large Mouth Bass at the Bayou Meto 67-167 location.
At the Arkansas Highway 161 location, TCDD concentrations ranged
from 22 to 36 ppt depending upon the species of fish sampled.
In comparison, as a part of EPA's National Bioaccumulation
Study (EPA, 1992), fish data were collected to help identify
background levels of dioxin in fish. Sixty fish samples were
collected from fresh and estuarine waters at a total of 34 sites
away from points of obvious industrial activity. The average TEQ
was 1.2 ppt (assuming half the detection limit for non-detects).
When looking at all areas (not just pristine or background) EPA
(1992) found an average of 11 ppt TEQ for 314 stations sampled.
6.5 REMEDIAL ACTION GOALS
Site contaminants dissolved in ground water are migrating
away from the CPA primarily to the west and east, which are the
predominant directions of ground water flow. The westward
migration is impeded by the French drain located between the CPA
and Rocky Branch Creek. Without future remediation or
containment efforts, compounds dissolved in the ground water have
the potential to migrate off-site, particularly along the eastern
portion of the site where residential neighborhoods are located.
The rate of migration of the dissolved phase contamination
depends upon the organic carbon sorption coefficients, molecular
weights, solubility in water, and other compound-specific
parameters. Site-specific data show that compounds with the
highest molecular weights and lowest solubilities (i.e.,
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chlorophenoxyherbicides, tetrachloro-benzene, and 2,3,7,8-TCDD)
have migrated to a lesser extent than more mobile site compounds
such as the chlorinated phenols.
The applicable remedial action objectives for OU3 that
relate to ground water plume containment, versus restoration,
are:
To prevent potential contamination of off-site ground water
by controlling ground water migration in the area of the
site through the use of ground water extraction wells and
the existing French drain system.
Ground water will be monitored for contaminant
concentrations using monitor wells at or near the plume
boundaries. Risk-based plume concentration levels (PCLs)
will be used as a trigger to implement additional ground
water controls to prevent off-site migration of ground water
above health-based levels. The proposed PCLs are shown in
Table 23. These levels were calculated for several of the
contaminants at the t.Ite that were selected based upon their
mobility and toxicity. The calculations are based on dermal
exposure to head, hands and feet, incidental oral ingestion,
and inhalation of volatiles. If the PCLs, also referred to
as trigger levels, are exceeded, then additional actions,
such as increased extraction well pumping rates, will be
taken to prevent off-site migration of contaminated ground
water. The proposed trigger levels may be revised following
additional testing. Any changes to these levels will be
identified in the final remedial design package.
To prevent off-site human and environmental receptors from
potential exposure to contaminated ground water discharges
that would result in an adverse toxic response, or a
carcinogenic risk greater than 1 x 10~4 to 1 x 10~6.
Ground water in the area of the Vertac site is relatively
shallow (5 to 10 feet depending upon location and rainfall)
and as such, migration of highly contaminated shallow ground
water into nearby surface waters is possible if left un-
contained. Direct dermal contact with contaminated surface
waters and incidental ingestion would be the most likely
exposure route for ground water contaminants. In addition,
because there are no restrictions on the use of ground water
for areas around the Vertac site, the possibility exists
that ground water wells could be installed in nearby
residential areas, with the water being used for domestic
purposes such as irrigation and watering. Exposure under
this scenario again would primarily be through dermal
contact and incidental ingestion. Therefore, the trigger
levels that would initiate more aggressive plume containment
measures established at or near the plume boundaries reflect
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both carcinogenic and non-carcinogenic risks based on
dermal, incidental ingestion, and inhalation exposure
pathways. The rationale used to calculate these levels is
discussed below.
Conventionally, remedial action goals, more commonly
referred to as "remedial action levels," are established for
ground water based on site exposure to workers or residents
through ground water ingestion and dermal contact. Because the
ground water at the Vertac site will not be used for domestic or
commercial purposes due to deed restrictions and other land use
restrictions to be imposed, the ingestion pathway was not
considered as a potential exposure pathway. Most of the surface
area where ground water contamination exists will be fenced off
and not physically accessible to residents. Additionally, deed
restrictions will be imposed to prevent installation of water
wells on the site.
The use of ground water at the Vertac site is not considered
likely, due to restricted future access to the site, deed
restrictions, and limited ground water yield from on-site
aquifers. Additionally, production rates and movement of the
contaminated ground water are so limited that it is feasible to
retract and contain the ground water contamination within the
general source area of the contamination. Finally, the fractured
geology in the area provides seeps and cracks into which NAPLs
tend to collect. Conventional aquifer remediation methods are
relatively ineffective at restoring ground water in fractured
aquifers contaminated with DNAPL due to, among other things, the
surface tension of the waste, potentially limited communication
between fractures, and relatively low solubilities of the DNAPL
wastes. A more detailed discussion regarding the technical
infeasibility of restoring this aquifer is included in Section
10.2. Therefore, EPA has concluded that containment of the
contaminated groundwater plume within the site's boundaries,
versus technically impracticable ground water restoration through
removal of the LNAPL and DNAPL contaminant sources, is
appropriate.
In order to ensure that plume retraction and containment
within the site's boundaries is in fact occurring, EPA has
established criteria for ground water contaminant concentrations
at or near the plume boundary based on both carcinogenic and non-
carcinogenic PCLs for specific contaminants of concern detected
in the ground water. Along with aggressive ground water
extraction, where the extracted ground water will be treated and
discharged from the on-site water treatment plant into Rocky
Branch Creek after meeting State water quality standards, ground
water monitoring will take place. The purpose of this ambient
ground water monitoring is to ensure that the contaminated plume
does not move off-site. Therefore, in order to be able to define
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the plume's boundaries, it is necessary to establish trigger
levels for several specified compounds.
The contaminants selected for monitoring are shown in Table
23 along with calculated trigger levels. The basis for selecting
these constituents is that they represent the most mobile and/or
the most toxic contaminants at the site. For constituents other
than 2,3,7,8-TCDD, the levels were determined by considering
dermal exposure, incidental oral ingestion, and inhalation of
volatiles (for volatile compounds only), and reflect both
carcinogenic and non-carcinogenic risks. For reasons discussed
below, the level for 2,3,7,8-TCDD was determined based on
incidental oral ingestion only. The resulting level reflects
carcinogenic risk. The hypothetical scenario used in all trigger
level calculations is based on contaminated ground water entering
Rocky Branch Creek or other areas at the site, and a
child/teenager exposed by periodically entering or playing in
areas where ground water may discharge to the surface. The
calculations assumed exposure for 1 hour, 60 days per year for a
10 year period (from age 7 to 17). The levels do not reflect
contamination that may already exist in the creek.
The reassessment of dioxin, Health Assessment Document for
2,3,7,8-TCDD and Related Compounds Volume 1, June 1994, cited
studies indicating that 2,3,7,8-TCDD was absorbed dermally at a
very slow rate (rate constant of 0.005 per hour). Results of
these studies also suggest that the majority of the compounds
remaining at the skin exposure site were associated with the
stratum corneum and did not penetrate through to the dermis.
Therefore, only oral ingestion was considered in the scenario for
2,3,7,8 TCDD and a monitoring level of 7E-06 mg/1 was calculated
based on a target excess lifetime cancer risk of IE-OS.
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Table 23
CONTAMINANT
Chlorophenol-2
Dichlorophenol-2 , 4
2,4-D
Silvex (2,4,5-TP)
Toluene
Trichlorophenol-2 ,4,5
Trichlorophenol-2 ,4,6
2,4,5-T
2,3,7,8-TCDD
TRIGGER LEVEL*
6 mg/1 (N)
2 mg/1 (N)
210 mg/1 (N)
84 mg/1 (N)
9 mg/1 (N)
52 mg/1 (N)
0.1 mg/1 (C)
210 mg/1 (N)
7 ng/1 (C)
* (N) - Noncancer Risk-Based Concentration
(C) - Cancer Risk-Based Concentration
7.0 DESCRIPTION OF ALTERNATIVES
7.1 ALTERNATIVES
Due to the technical impracticability of extracting and
treating the NAPLs found under the Vertac site, EPA has
formulated remedial action alternatives for OU3 to address
envir«- ^antal concerns associated with the presence of low level
threat site-related compounds in the ground water beneath the
site. As discussed in Section 4.0, the NAPL contamination at the
site is considered a principal threat that is technically
impracticable to address. Therefore, the goal of the remedial
alternatives evaluated in the feasibility study (FS) beyond the
mandatory no action alternative was to address the resulting
ground water contamination caused from ground water's direct
contact with this principal threat. Thus, with the exception of
the no action alternative, the other two alternatives evaluated
in this ROD address the low level threat posed by the
contaminated ground water and provide a mechanism for EPA to
reassess every five years the containment remedy provided by
those two alternatives. (Where EPA implements a remedy that
results in hazardous substances remaining at a site, pursuant to
CERCLA Section 121(c), 42 U.S.C. § 9621(c), EPA is required to
evaluate every five years that remedy.) Therefore, under the two
action alternatives, EPA will be required to assess whether a
technology has emerged that is capable of addressing the
76
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principal threat NAPLs, and possibly utilize that technology by
way of an amendment to this ROD.
The purpose of the alternatives development process is to
generate remedial action alternatives that provide a range of
approaches and effectiveness in addressing ground water at the
site. A total of three alternatives were evaluated for OU3.
Alternative l No Action
DESCRIPTION
The no action alternative for OU3 media at the site provides
a basis for comparing existing site conditions with those
resulting from implementation of the other proposed alternatives.
Under the no action alternative, no additional measures would be
used to remediate, or contract and contain, contaminated ground
water at the site. No institutional controls, facility
maintenance, or monitoring would be implemented, except for those
being performed in accordance with the 1984 Court Order.
Implementing no remedial activities for the OU3 media at the
site allows the existing contaminant sources to remain in place
or migrate to off-site areas. Contaminated ground water is
currently not presenting an immediate threat to the environment
or posing any substantial risk to human health. However,
evidence has shown that the site-related contaminants are slowly
migrating outward from the CPA of the site and will continue to
do so if left unchecked. Shallow ground water flow to the west
and south appears to be impeded by the French drain and central
ditch. Migration to the east is currently uncontrolled. Without
any remedial measures to control the movement of this plume, the
site-related contaminants are expected to move beyond the
boundary of the site into the residential area.
The Superfund program requires that a no action alternative
be considered at every site as a basis of comparison when
evaluating other alternatives. This alternative would not
decrease the toxicity, mobility, or volume of contaminants,
adequately protect human health or the environment, or comply
with State and Federal environmental regulations, and therefore,
was not selected.
COST AND TIME OF IMPLEMENTATION
Capital Cost: $0
Annual Operation and Maintenance: $0
Present Worth - Capital and O&M: $0
Time of Implementation: 0 years
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Alternative 2 Ground water Hydraulic Containment and Treatment
and Discharge of Treated Extracted Ground Water
DESCRIPTION
This alternative would include the installation of some
additional ground water extraction wells primarily in the eastern
porion of the central process area to control ground water
movement toward the eastern margin of the site, and to provide
treatment of the dissolved phase plume that is extracted from the
hydraulic containment operations. Based on the results of the
previously-conducted short term pump tests and on the extended
duration pump test, this series of extraction wells is expected
to produce a hydraulic barrier to eastward ground water migration
at a pumping rate of only 2 to 4 gallons per minute (gpm) per
well and at the same time reduce the contaminant concentrations
in the center of mass. Figures 9 and 10 show the conceptual
layout of the extraction well system. The existing French drain
system will continue to restrict shallow ground water movement
toward Rocky Branch Creek in the areas where it is currently
installed.
Ground water recovered from the extraction wells will be
pumped into the on-site wastewater treatment plant. This plant
at present treats ground water intercepted by the French drain
through a two step process of oil/water separation to remove
NAPLs followed by aqueous-phase treatment with activated carbon.
The treated water is then discharged into Rocky Branch Creek and
is required to meet standards established by the ADPC&E.
The existing Reasor-Hill well, located west of the CPA, will
be reconditioned to allow extraction of non-aqueous phase liquids
from the arnifer. Any aqueous phase liquids collected in the
process will be treated in the on-site wastewater treatment plant
and subsequently discharged into Rocky Branch Creek. The NAPLs
will be separated from the ground water and treated using the
same method currently employed for the NAPLs collected from the
existing French drain. Likewise, MW-92 will be used as an
extraction well on a downdip sand. Other wells may be used
depending on the analysis of data gathered in the remedial design
phase.
To monitor the performance of the extraction wells, a ground
water monitoring program will be established. This ground water
monitoring will ensure that containment is being maintained.
Ground water elevation data and contaminant concentration data
will be used to determine if and when increased or decreased
extraction rates are necessary to contain the plume in response
to seasonal precipitation rates. The monitoring program will
also be designed to provide indications of long term changes in
site conditions, allowing for modifications to the remedial
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O...... 57 Observation Well. Water Levels were
w Measured Manually Using a W^ler
Level Probe
French Drain
Slurry Wall
hence Line
Property Boundary
Central Process Area Boundary
Central Ditch
- -- V' ' ' 'V^M^/ nV
b^ ' \ wy^J I I:>M\X/(.|»
^^ tf ^MW '>''
Source Vertac Site Boundary and Pnotoqrdmrnelru
Survey Prepared by West and Associates. Ini
/
-f -{ r
Prelection Arkiruai Coofdlnate Systerr
Nonn Zone [Nft> l»83|
FIGURE a
CONCEPTUAL GROUND WATER
RECOVERY WELL LOCATIONS
VERT AC SITE
JACKSONVILLE. AR
-------
NORTH
SOUTH
Extraction
Well
Extraction
Well
Extraction
Well
Extraction
Well
Consolidated
Weathered
Shale and Siltstone Unit
95P-1675 3/28/95
FIGURE 10 CONCEPTUAL GROUNDWATER EXTRACTION WELL CROSS SECTION
VERTAC SITE, JACKSONVILLE, AR
-------
action program. Figure 11 depicts some of the wells that could
be used in the ground water monitoring program.
The number and location of the ground water extraction wells
and the ground water monitoring wells will be selected during the
remedial design phase based on the results of additional ground
water investigation and a better understanding of the site
hydrogeology. The design may be modified based on information
gathered during implementation, and it is anticipated that a
phased approach will be necessary for the extraction and
monitoring well design. After the completion of the extraction
wells, pumping tests will verify the radius (zone) of influence
for each extraction well. If tests reveal that a particular
extraction well does not attain sufficient containment, new or
supplemental locations will be needed.
As discussed in Section 6.5, monitor wells will be used in
areas near the contaminated ground water plume boundary to
monitor contaminant concentrations. If these concentrations
exceed the trigger levels shown in Table 23, additional action to
contain contaminated groui "*. water (e.g. additional extraction
wells, increased extraction rates, etc.) will be required.
Deed restrictions and land use controls such as the
enactment of ordinances prohibiting water well installation
within the zone of ground water contamination must be established
for the site. Deed restrictions are easily implemented and would
provide legally binding controls to ensure that the site ground
water would not be used for domestic purposes in the future. The
Vertac Receiver is in a position to impose, on a voluntary basis,
appropriate deed restriction that would run with the land and
would ensure that land use be restricted to industrial activities
and would alert any future purchaser of the fact that hazardous
substances are present in ground water.under the site.
Operation and maintenance activities would also be necessary
as a part of this alternative. Repairs to extraction wells and
the associated piping system, including periodic inspection or
replacement of ground water pumps, would be expected.
COST AND TIME OF IMPLEMENTATION
Capital Cost: $908,000
Annual Operation and Maintenance: $126,000 year 1
$109,000 years 2-30
Present Worth - Capital and O&M: $2,525,000
Time of Implementation: 1 year
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// MW-J4A* \i\ if..^m' j, ..
jj MW-23A«»\\ -| *PZ-H4//
'.--=-^ , nt----T-*3Br-
8LV._^<^(OT(/.8i9W *w!- « i « O
FIGURE 11
POTENTIAL (WOUND WATER
MONITORING WELLS
VERTACSFTE
JACKSONVILLE. ARKANSAS
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Alternative 3 Ground Water Hydraulic Containment and Treatment
with Source Recovery
DESCRIPTION
Under Alternative 3, all remedial measures prescribed in
Alternative 2 would be implemented. Additionally, source
recovery measures would be implemented to increase removal of
potentially mobile NAPLs and high concentration contaminated
ground water in the northern portion of the CPA. Source recovery
would be implemented in parts of the CPA from existing wells that
appear to have potentially recoverable amounts of NAPLs and
higher concentration dissolved contaminants based on observations
and results obtained during the RI, and additional investigative
measures implemented during pre-design phases. During the design
phase, the best method of source recovery would also be
evaluated. It is expected that source recovery would consist
primarily of small volumes of NAPLs and higher concentration
dissolved-phase ground water, and it is doubtful whether
restoration of the aquifer to drinking water quality could be
accomplished.
Although it is expected that the pumping rate would be low,
the pumping rate would be established to optimize the volume of
NAPLs recovered during field testing. The extracted ground water
would be phase-separated to recover the non-aqueous phase
liquids. Any recovered aqueous phase liquids would be treated in
the existing wastewater treatment plant, and recovered NAPLs
would be treated by the same method implemented for NAPLs from
the French drain system. After treatment in the on-site water
treatment plant so as to meet Arkansas water quality criteria,
the waste water would be discharged into Rocky Branch Creek.
COST AND TIME OF IMPLEMENTATION
Capital Cost: $1,384,000
Annual Operation and Maintenance: $163,000 year 1
$146,000 years 2-30
Present Worth - Capital.and O&M: $3,550,000
Time of Implementation: 1 year
7.2 ARARS
In conducting a remedial action, EPA is required to attain a
degree of cleanup for a given site that assures protection of
human health and the environment. "Applicable or relevant and
appropriate requirements" (ARARs) are the federal, state, or
local requirements that ensure such a cleanup standard. (See
CERCLA Section 121(d), 42 U.S.C. § 9621(d), and NCP Section
300.410(9), 40 CFR § 300.410(g).) Applicable requirements are
those standards, requirements, criteria, or limitations
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promulgated under federal environmental, state environmental, or
facility siting laws that specifically address a hazardous
substance, pollutant, contaminant, remedial action, location, or
other circumstance found at a CERCLA site. However, CERCLA
Section 121(d)(4), 42 U.S.C. § 9621(d)(4), and Section
300.430(f)(1)(c), 40 CFR § 300.430(f)(1)(c), allow EPA to select
remedial alternatives that do not meet an ARAR if one of seven
conditions arise. Those conditions are summarized as follows:
The remedy under consideration is only an interim
remedy and is not the final or permanent remedy
selected for the site.
Compliance with such standards would create greater
risks to public health that the benefit it would
provide.
Compliance with standards is "technically
impracticable".
A different remedy exists that provides public health
protection "equivalent" to the preferred cleanup
standard.
A more stringent state standard, which would otherwise
be applicable, has not been consistently applied to
other sites in the state.
Compliance with an applicable state requirement would
effectively result in the state-wide prohibition of
land disposal of hazardous substances.
" The cost of the remedy is too expensive, considering
the other demands on the Fund.
Relevant and appropriate requirements are those standards,
requirements, criteria, or limitations promulgated under federal
environmental, state environmental, or facility siting laws that,
while not "applicable" to hazardous substances, pollutants,
contaminants, remedial actions, locations, or other circumstances
at a CERCLA site, address problems or situations so that their
use may be suited to the particular site. Factors that may be
considered in making this determination, when the factors are
pertinent, are discussed at NCP Section 300.440(g)(2), 40 CFR
§ 300.400(g)(2). They include, among other considerations,
examination of: The purpose of the requirement and the purpose
of the CERCLA action; the actions or activities regulated by the
requirement and the remedial action contemplated at the site; and
the potential use of resources affected by the requirement and
the use or potential use of the affected resource at the CERCLA
site.
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ARARs are divided into chemical-specific, location-specific,
and action-specific requirements. Chemical-specific requirements
govern the release to the environment of materials possessing
certain chemical or physical characteristics or containing
specific chemical compounds. Chemical-specific ARARs are
numerical standards. These values establish the acceptable
amount or concentration of a chemical that may be found in, or
discharged to, the ambient environment.
Location-specific ARARs relate to the geographic or physical
position of the site, rather than to the nature of site
contaminants. These ARARs place restrictions on the
concentration of hazardous substances or the conduct of cleanup
activities due to the site's location in the environment (i.e., a
site located in a flood plain).
Action-specific ARARs are usually technology- or activity-
based requirements, or are limitations on actions taken with
respect to hazardous substances. A particular remedial activity
will trigger an action-specific ARAR. Action-specific ARARs
dictate how the selected remedy must be implemented.
Only the substantive portions of requirements are ARARs.
Administrative requirements are not ARARs and, thus, do not apply
to actions conducted entirely on-site. Administrative
requirements are those that are non-substantive requirements that
involve such actions as consultation, issuance of permits,
documentation, reporting, record keeping, and enforcement. The
CERCLA program has its own set of administrative procedures that
assure proper implementation of CERCLA because the application of
additional or conflicting administrative requirements could
result in delay or confusion. Provisions of statutes or
regulations that contain general goals that merely ^xpress
legislative intent about desired outcomes or conditions, but are
non-binding, are not ARARs.
State standards that are identified in a timely manner by
the state in which a Superfund site is located and are more
stringent than federal requirements may be applicable or relevant
and appropriate. To be an ARAR, a state standard must be
"promulgated," which means that the standards are of general
applicability, are legally enforceable, and have been equally
applied.
Additional standards may be identified as "to be considered"
(TBC). The TBC category consists of advisories, criteria, or
guidance which was developed by EPA, other federal agencies,
states, or local agencies that may be useful in developing CERCLA
remedies. These may be considered as appropriate in selecting
and developing cleanup actions.
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Because of the extremely complex hydrogeological conditions
at the site and the lack of existing technologies that are
effective in extracting NAPLs from a tilted, fractured bedrock
system, the Agency does not believe restoration of contaminated
ground water to SDWA MCLs is feasible in some areas of the site.
In addition, the contaminated Atoka aquifer exhibits low ground
water deliverability and is generally not used as a water source
in the area. Therefore, a waiver for meeting MCLs in these areas
based on technical impracticability is warranted. A detailed
discussion on the rationale for this waiver is included in
Section 10.2.
The primary ARARs considered potentially applicable to OU3
media, are listed in Table 24. These potential ARARs were
identified based on site-specific conditions and are described in
more detail in the remainder of this section.
In identifying ARARs for OU3, it is important to recognize
that the Vertac site has three existing burial areas that are
closed under a 1984 Court Order. In that Order, dated July 18,
1984, in the matter styled U.S. v. Vertac Chemical Corporation
and Hercules, Inc., E.D. Ar., Western Division, No. LR-C-80-109,
Judge Henry Woods concluded that the Vertac Plan, which EPA
opposed, but which the State of Arkansas supported, was superior
to an alternative plan submitted by EPA. Specifically, the
Vertac plan allowed the burial in the North Burial Area of
barrelled waste containing up to 100 ppm dioxin and allowed the
burial in that location of chlorinated phenols, anisoles,
chlorinated benzenes, 2,4-D, 2,4,5-T, and the burial of aldrin,
dieldrin and DDT in the Reasor-Hill Burial Area. In addition,
the Court ordered the creation of "Mount Vertac," which consisted
of an above-ground vault lined with a single clay liner located
at the sit<~ of a closed cooling pond, whose contaminated soils
and sediments were then placed within the vault. Finally, the
Court in its Order concluded that the dioxin-containing barrels
buried in the North Burial Area do not pose a serious danger of
moving off-site underground (with which finding EPA disagrees).
See Order of July 18, 1984, at page 4. Therefore, pursuant to a
final order of the Court with respect to those areas, the
containment by burial of dioxin wastes in concentrations up to
100 ppm do not constitute a principal threat to the public health
or the environment.
Table 24. Primary ARARs Potentially Applicable to Ground water
at the Vertac Site, Jacksonville, Arkansas
Chemical-Specific
Resource Conservation and Recovery Act (RCRA), 42 U.S.C. §
6901 et sejj.
Clean Water Act (CWA) , 33 U.S.C. § 1251 e£
86
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Safe Drinking Water Act (SDWA) , 42 U.S.C. § 300f fit
Clean Air Act (CAA) , 42 U.S.C. § 7401 fit seq.
Arkansas State Ground Water Quality Protection Strategy
Water Quality Standards for Surface Waters of the State of
Arkansas, ADPC&E Reg. No. 2
State Administration of the National Pollutant Discharge
Elimination System, ADPC&E Reg. No. 6
Arkansas Underground Injection Control Code, ADPC&E Reg. No.
17
Location-Specific
Resource Conservation and Recovery Act, 42 U.S.C. § 6901 fit
seq.
State Administration of the National Pollutant Discharge
Elimination System, ADPC&E Reg. No. 6
Action-Specific
Resource Conservation and Recovery Act, 42 U.S.C. § 6901 fit
Clean Water Act, 33 U.S.C. § 1251 fit seq.
Clean Air Act, 42 U.S.C. § 7401 fit Sfiq.
Water Quality Standards for Surface Waters of the State of
Arkansas, ADPC&E Reg. No. 2
State Administration of the National Pollutant Discharge
Elimination System, ADPC&E Reg. No. 6
Rules and Regulation Governing the Certification of
Wastewater Utilities Personnel Reg. No. 3
7.2.1 Federal ARARs
Resource Conservation and Recovery Act
The Resource Conservation and Recovery Act, 42 U.S.C. § 6901
fit SfiS.) :
RCRA Subtitle C established a comprehensive regulatory
program to control and manage hazardous waste from the time
of generation to disposal.
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Under RCRA Subtitle D, EPA promulgated regulations
containing guidelines to assist in the development and
implementation of state non-hazardous solid waste management
plans.
RCRA requirements may be ARARs to OU3 because some residues
resulting from treatment of ground water at the Vertac site may
constitute RCRA hazardous wastes. In general, RCRA regulations
apply to the management of RCRA hazardous wastes and RCRA waste
management facilities. Regulations promulgated under RCRA
generally provide the basis for management of hazardous waste and
establish technology-based requirements for hazardous waste
facilities.
Chemical-Specific Requirements
Hazardous Waste Identification
The regulations governing the identification and
classification of RCRA hazardous wastes are found at 40 CFR Part
261. These regulations may ' 3 applicable to residues generated
from a ground water treatment system. Residual material would
have to be tested to determine its RCRA classification as
follows:
Characteristic hazardous wastes (defined at Subpart C of 40
CFR Part 261), which involve evaluation of the following
general waste characteristics:
Ignitability (D001 waste)
Corrosivity (D002 waste)
Reactivity (D003 waste)
Toxicity (D004 - D043 wastes) due to specific chemical-
specific compounds.
Specific tests cited in the regulations are used to
determine if a solid waste also constitutes a RCRA characteristic
hazardous waste. The maximum concentrations of contaminants
allowed in the leachate of a solid waste before the solid waste
is considered hazardous for the toxicity characteristic (TC) are
presented in 40 CFR § 261.24. Site-related compounds for which a
TC level has been identified include:
Waste Code Compound Name TC Level
DO16 2,4-Dichlorophenoxyacetic Acid 10.0 mg/L
DO41 2,4,5-Trichlorophenol 400 mg/L
DO42 2,4,6-Trichlorophenol 2.0 mg/L
DO17 Silvex 1.0 mg/L
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RCRA Action-Specific ARARs
Action-specific ARARs are usually technology or activity-
based requirements or limitations on actions taken with respect
to hazardous wastes. These requirements may be triggered by the
particular remedial action that is selected to accomplish the
selected alternative.
General TSD Facility Requirements
General TSD facility requirements under RCRA apply to those
facilities that treat, store, or dispose RCRA hazardous wastes.
The requirements that could potentially be ARARs at the site
include:
General facility standards (40 CFR Part 264, Subpart B)
including those for waste analysis.
Preparedness and prevention standards (40 CFR Part 264,
Subpart C) addressing facility design and operation and
required equipment.
Contingency plan and emergency procedures (40 CFR Part 264,
Subpart D).
Manifest system recordkeeping and reporting (40 CFR Part
264, Subpart E) to continuously track off-site hazardous
waste transport.
Underground Injection (40 CFR Part 264.1 Subpart A)
stipulates compliance with the requirements of 40 CFR 264 as
required by the SDWA.
Ground Water Monitoring
Regulations found at 40 CFR § 264.91 stipulate that owners
or operators of certain RCRA treatment, storage or disposal (TSD)
units (ix£., landfills, impoundments, waste piles) must conduct a
ground water monitoring and response program. Although these
requirements are not applicable to site-wide monitoring that may
be part of a selected remedy for ground water, the RCRA ground
water monitoring program may be consulted, where relevant and
appropriate. Ground water monitoring wells will be used to track
the operation and performance of the selected remedy. The number
and location of the monitoring locations will be determined by
site-specific conditions. Existing monitoring wells will be
utilized if their location and construction are consistent with
the monitoring objectives.
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Clean Water Act fCWAl
The Clean Water Act, 33 U.S.C. § 1251 et seq., required EPA
to establish regulations to protect the quality of surface waters
across the nation. The CWA may be applicable to treatment and
discharge of water recovered as part of remedial action for OU3
ground water.
Under the CWA, three interrelated areas were identified for
regulation:
Establishment of water quality standards;
Establishment of stormwater runoff control; and
Establishment of effluent standards (discharge limitations)
intended to ensure compliance with applicable water quality
standards.
Water quality standards represent chemical-specific
requirements, while stormwater runoff controls and effluent
standards are action-based requirements. Each is addressed
separately below.
Chemical-Specific Requirements
Water Quality Criteria (WQC)
CERCLA Section 121(d)(2)(A), 42 U.S.C. § 9621(d)(2)(A),
states that remedial actions shall attain Federal water quality
criteria where they are relevant and appropriate under the
circumstances of the release or threatened release. Water
quality criteria are non-enforceable guidance developed under the
CWA Section 304, 33 U.S.C. § 1314, but are,used by the state, in
conjunction with a designated use for a stream segment, to
establish water quality standards under CWA Section 303, 33
U.S.C. § 1313. In determining the applicability or relevance and
appropriateness of water quality criteria, the most important
factors to consider are the designated uses of the water and the
purposes for which the potential requirements are intended.
Water quality criteria have been developed based on:
Protection of human health. These levels have been
developed based on two separate potential exposure pathways.
The first criterion is based solely on consumption of fish,
while the second criterion considers both consumption of
fish and consumption of water.
Protection of aquatic life. These levels have been
developed based on acute toxicity and chronic toxicity
effects to aquatic organisms.
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Whether a water quality criterion is appropriate and which
form of the criterion is appropriate depends on the likely
route(s) and receptors of exposure. The State of Arkansas has
used these Federal guidelines to establish surface water
standards. These standards, as set forth by the State, are
discussed under the category Regulation' 6 below.
Action-Specific Requirements
Direct Discharge of Treatment System Effluents
Direct discharge of waste waters to a surface water is
governed by the NPDES permitting requirements. 40 CFR Parts 122,
125, and 129 as applicable to point source discharges to waters
of the United States, which require:
The use of the Best Available Technology (BAT) economically
achievable to control toxic and nonconventional pollutants.
Use of best conventional control technology (BCT) is
required to control conventional pollutants. Technology-
based limitations may be determined on a case-by-case basis.
40 CFR § 122.44 and state regulations approved under 40 CFR
Part 131 require compliance with applicable Federally-
approved state water quality standards. These standards
may be in addition to or more stringent than other Federal
standards under the CWA.
40 CFR § 122.44(e) requires that discharge limitations must
be established at more stringent levels than technology-
based standards for toxic pollutants.
40 CFR § 125.100 requires that Best Management Practices
(BMP) be developed and implemented to prevent the release of
toxic constituents to surface waters.
40 CFR § 122.41(i) requires that discharges must be
monitored to assure compliance with Federally-approved state
water quality standards. The discharger will monitor the
mass of each pollutant, the volume of effluent, and the
frequency of discharge and other measurements as
appropriate.
The direct discharge requirements may be applicable if
waters generated during the remediation are discharged to Rocky
Branch Creek. ADPC&E would establish discharge limitations which
would apply to the site wastewaters if they are discharged to
Rocky Branch Creek. Water generated during the remedial action
for OU3 would need to be treated to meet the discharge limits.
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Safe Drinking Water Act
The SDWA (42 U.S.C. § 300f e± sea.) requires EPA to
establish regulations to protect public health from contaminants
in drinking water. Potential SDWA ARARs identified are chemical-
specific as discussed below.
Chemical-Specific Requirements
EPA has promulgated primary and secondary drinking water
standards that are applicable to public water systems. Public
water systems are defined as systems for the provision of piped
water for human consumption with at least 25 persons. Primary
drinking water standards are enforceable standards that are not
to be exceeded in public water supplies. Secondary drinking
water standards are nonenforceable (at the Federal level)
standards that are intended to serve as guidelines for use by
states in regulating water supplies.
National Primary Drinking Water Standards
National Primary Drinking Water Standards are set out at 40
CFR § 141 and are expressed as maximum contaminant levels (MCLs).
MCLs for 30 toxic compounds, including the 14 compounds adopted
as RCRA MCLs, have been adopted as enforceable standards for
public drinking water systems (40 CFR §§ 141.11-141.26). An MCL
is required to reflect the technical and economic feasibility of
removing the contaminant from the water supply. The MCLs
applicable to ground water at the Site are shown on Table 25.
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Table 25
SAFE DRINKING WATER ACT DRINKING WATER STANDARDS
VERTAC SITE, JACKSONVILLE, ARKANSAS
Site-Related compound
Chloride
2-Chlorophenol
4-Chlorophenol
2 , 4-Dichlorophenol
2 , 6-Dichlorophenol
2,4, 5-Trichlorophenol
2,4, 6-Trichlorophenol
Toluene
Tetrachlorobenzene
2,4-D
2,6-D
2,4,5-T
2,4,6-T
2,4,5-TP (Silvex)
2,3,7,8-TCDD (Dioxin)
MCL (mg/1)
_
_
_
_
_
_
_
1.0
_
0.07
_
0.05
3.00E-08
SMCL (mg/1)
250
_
-
NOTES: MCL = Maximum Contaminant Level
SMCL = Secondary Maximum Contaminant Level
= No level has been established.
Pertinent SDWA regulations found at 40 CFR §§ 142.4 and
142.5 allow public water suppliers to obtain exemptions and
variances from complying with MCLs under certain situations.
However, it must be shown that noncompliance will not result in
an unreasonable risk to human health.
Secondary Drinking Water Standards
Secondary Drinking Water Standards are established for 13
parameters set out at 40 CFR § 143 and are expressed as Secondary
Maximum Contaminant Levels (SMCLs). The SMCLs applicable to the
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Site are identified on Table 25. The SMCLs are non-enforceable
at the Federal level but are aesthetic-based guidelines (i.e.
taste and odor criteria that take into consideration available
treatment technologies and cost of treatment).
Chemical-Specific Requirements
Underground Injection Control (UIC) Program
As part of the SDWA, the EPA has set forth requirements for
permitting, operation, and closure of injection wells (40 CFR §§
144 and 146). Although there are no active or planned injection
wells at the site, a few drums of waste materials were reportedly
dumped down the Reasor-Hill well. The requirements or the UIC
program are dependant on the classification of the injection
well. Classifications are as follows:
Class I Wells used by generators of hazardous wastes, or
other industrial or municipal wells, to inject
fluids beneath the lowermost formation containing,
within one-quarter mile of the well bore, an
underground source of drinking water.
Class II Wells which inject fluids a) which were brought to
the surface in connection with oil or natural gas
storage operations, b) for enhanced recovery of
oil or natural gas, or c) for storage of liquid
hydrocarbons.
Class III Wells which inject fluids for extraction of
minerals.
Class IV Wells used by generators of hazardous wastes, or
other industrial of municipal wells, to inject
fluids into a formation containing, within one-
quarter mile of the well bore, an underground
source of drinking water. The Reasor-Hill well
would likely be included in this classification.
Class V Wells not included in Classes I, II, III, or IV.
Although specific standards for closure of Class IV wells do
not exist, there are standards for plugging and closure of Class
I wells.
7.2.2 STATE ARARS
Regulation No. 2; Water Quality Standards for Surface Waters
Pursuant to the Arkansas Water and Air Pollution Control Act
(AWAPCA), ACA 8-4-101 - 106, 8-4-201 - 229, and 8-4-301 - 313,
and in compliance with the requirements of the Federal Water
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Pollution Control Act, the State of Arkansas has developed water
quality standards for all surface waters, interstate and
intrastate. Established water quality standards are based upon
present, future, and potential uses of the surface waters of the
state and criteria developed from statistical evaluations of past
water quality conditions and a comprehensive study of least-
disturbed, ecoregion reference streams. The standards are
designed to enhance the quality, value, and beneficial uses of
the water resources of the state; aid in the prevention, control,
and abatement of water pollution; provide for the protection and
propagation of fish and wildlife; and, provide for recreation in
and on the water.
General standards for color, taste and odor, solids, toxics,
and oil/grease have been developed. In addition, specific
standards for temperature, turbidity, pH, dissolved oxygen,
radioactivity, bacteria, toxics, nutrients, oil/grease, and
mineral quality have been developed depending on the individual
ecoregions within the state. The site is situated within the
Arkansas River Valley Ecoregion.
Water quality standards relate to the existing on-site
treatment plant and its off-site discharges. As part of OU3, the
existing treatment plant may be utilized to treat extracted
ground water generated as part of the remediation. The existing
treatment plant, which treats water collected from the existing
French drain, discharges to Rocky Branch Creek according to
standards established by the ADPC&E.
Regulation 3; Certification of Wastewater Utilities Personnel
Operators in responsible charge of wastewater treatment
facilities are required to be licensed and certified by ADPC&E in
order to safeguard the public health and protect the waters of
the state from pollution. Certification typically includes
training, classifying, and licensing of treatment plant
operators.
Regulation 6t State Administration of the National Pollutant
Discharge Elimination System (NPDES)
The technical, versus procedural, requirements of an NPDES
permit may apply if wastewaters generated at the site are
directly discharged off-site into Rocky Branch Creek. Further,
the technical, versus procedural, requirements of a storm water
permit may apply if stormwater discharges associated with the
site remedial activities that involve disturbing more than five
(5) acres are discharged off-site to Rocky Branch Creek. An
individual NPDES permit may be issued by the ADPC&E, or general
permit coverage may be obtained under the Department's General
NPDES Permit No. ARROOAOOO. Obtaining NPDES coverage for off-
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site stormwater discharges requires submission of an individual
application, or notice-of-intent (NOI), development and
implementation of a stormwater pollution prevention plan, and
possibly stormwater sampling and monitoring.
The existing treatment plant on-site may be used to treat
wastewaters generated as part of the OU3 remediation. NPDES
discharge limits have been established by ADPC&E.
Regulation No.17: Arkansas Underground Injection Code
The Arkansas Underground Injection Control (UIC) Code (March
1989) was adopted under the Arkansas Water and Air Pollution
Control Act to qualify the State of Arkansas for authorization
for its UIC program pursuant to the SDWA. The code adopts the
Federal regulations of the SDWA pertaining to underground
injection. These regulations may be relevant and appropriate to
the Reasor-Hill well because some wastes were reportedly disposed
in the well at one time.
Regulation 23: Hazardous Wa^ce Management Code
The Arkansas Hazardous Waste Management Act of 1979 and the
Arkansas Resource Reclamation Act of 1979 are known together as
the Arkansas Hazardous Waste Management Code (amended June 1992),
ADPC&E Reg. No. 23. This code resembles the federal hazardous
waste management regulations promulgated under RCRA. The
Arkansas Hazardous Waste Management Code contains chemical-,
location-, and action-specific criteria that may be ARARs for
OU3.
Arkansas State Ground Water Quality Protection Strategy
The objective of Arkansas' ground water strategy is to
formulate and recommend a management program to protect the
quality of ground water resources. Arkansas' Ground Water
Quality Protection Strategy outlines water quality criteria for
ground water (drinking water) within the State. Arkansas has
adopted the recommended standards for drinking water set by the
SDWA. The Arkansas Department of Health uses the National
Primary Drinking Water Standards in setting the criteria to which
public water supplies must adhere.
Other State ARARs that may be applicable include:
Arkansas State Highway and Transportation Department
Hazardous Waste Transportation Permits
Arkansas Soil and Water Conservation Commission
- Arkansas Water Plan
Arkansas Ground Water Protection and Management
Act (Act 154 of 1991)
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Arkansas Department of Health
Rules and Regulations Pertaining to General
Sanitation (April 1974)r.
Individual Water Supply System (Bulletin No. 12
Revised June 1967)
Arkansas Water Well Construction Commission
Arkansas Water Well Construction Code Rules and
Regulations (Revised July 1988)
Arkansas Water Well Construction Act (March 1989)
State Board of Registration for Professional Geologists
Registration of Geologists Act of 1987 (Act 701)
Arkansas Game and Fish Commission
Arkansas Fragile Menagerie (January/February 1986)
Endangered and Threatened Species in the Natural
State
Arkansas List of Federally-Endangered and
Threatened Species
8.0 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
EPA is required to analyze each of the individual
alternatives against a set of 9 criteria and develop a
comparative analysis that focuses upon the relative performance
of each alternative against those criteria.
The nine evaluation criteria are as follows:
1. Overall Protection of Public Health and the Environment
This criterion addresses the way in which a potential remedy
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 may be through engineering
controls, treatment techniques, or other controls such as
restrictions on the future use of the site. Total elimination of
risk is often impossible to achieve. However, a remedy must
minimize risk to assure that human health and the environment
would be protected.
2. compliance with ARARs
Compliance with ARARs, or "applicable or relevant and
appropriate laws and regulations," assures that a selected remedy
will meet all related federal, state, and local requirements.
The requirements may specify maximum concentrations of chemicals
that can remain at a site; design or .performance requirements for
treatment technologies; and, restrictions that may limit
potential remedial activities at a site because of its location.
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3. Long-Term Effectiveness or Permanence
This criterion addresses the ability of a potential remedy
to reliably protect human health and the environment over time,
after the remedial goals have been accomplished.
4. Reduction of Toxicity, Mobility, or Volume of Contaminants
This criterion assesses how effectively a proposed remedy
will address the contamination problems. 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.
5. Short-Term Effectiveness
This criterion addresses the time factor. Technologies
often require several years for implementation. A potential
remedy is evaluated for the length of time required for
implementation and the potential impact on human health and the
environment during the implementation.
6. Implementabillty
Implementability addresses the ease with which a potential
remedy can be put in place. Factors such as availability of
materials and services are considered.
7. Cost
Costs (including capital costs required for design and
construction, and projected long-term maintenance costs) are
considered and compared to the benefit that will result from
implementing the remedy.
8. State Acceptance
The State of Arkansas has had an opportunity to review the
FS, the Proposed Plan and the ROD, and offer comments to EPA.
The State of Arkansas fully supports EPA's preferred alternative.
9. Community Acceptance
During the public comment period, interested persons or
organizations have commented on the alternatives. EPA has
carefully considered these comments in making its final
selection. The comments received in response to EPA's Proposed
Plan for OU3 are addressed in a document called a responsiveness
summary which is included as Appendix A of this ROD. For
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additional information on community participation, refer to
Section 3.0 of this document.
The nine criteria are categorized into three groups:
Threshold criteria, primary balancing criteria, and modifying
criteria. The threshold criteria must be satisfied 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 public comment is received on the Proposed Plan.
Threshold Criteria
Overall protection of human health and the environment.
Compliance with ARARs (applicable or relevant and
appropriate requirements of other Federal and State
environmental statutes).
Primary Balancing Criteria
Long-term effectiveness and permanence.
Reduction of toxicity, mobility, and volume through
treatment.
Short-term effectiveness.
Implementability.
Cost.
Modifying Criteria
State acceptance.
Community acceptance.
8.1 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES
1. OVERALL PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
Alternative 1 (no action) does not provide adequate
protection of human health and the environment considering the
potential long term effects of ground water migration off-site.
Under current conditions, the site does not pose a direct threat
from ground water, but continued uncontrolled ground water
migration to the east from the CPA may result in site-related
compounds exceeding MCLs, promulgated under the SDWA, 42 U.S.C. §
300f et sejj., off-site in the future.
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Alternatives 2 and 3 offer adequate protection of human
health and the environment due largely to the fact that
contaminated ground water would be drawn back to, and contained
within the site's boundaries. Thus, following the imposition of
necessary deed restrictions to ensure no on-site use of untreated
ground water would occur in the future, all contact pathways to
the contaminated ground water would be prevented. Ground water
flow from the CPA will be restricted in all directions by new
extraction wells and controls previously implemented. Ground
water monitoring requirements and deed restrictions will be
implemented to provide additional protection.
Alternative 3 may provide some degree of additional
protection through the operation of additional source recovery
wells within the northern portion of the CPA. These wells would
be installed in areas where recoverable NAPL is suspected or
where high concentrations of dissolved phase ground water
contamination were observed, and therefore could reduce the
spread of dissolved-phase ground water contamination. The added
benefit of this product recovery on ground water quality over
Alternative 2 is not expected to be substantial because
significant quantities of unrecoverable NAPL in the fractured
rock would still act as a source of contamination for dissolved
phases. Therefore, the additional overall protective benefit
derived from implementing Alternative 3 is considered to be de
minimis.
2. COMPLIANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE
REQUIREMENTS (ARARs)
Alternative 1 would not comply with ARARs. Site-related
contaminants would remain above MCLs within the CPA, and no
attempt-, would be made to remove or control the ground water
moving to the east. Alternative 2 would provide control of
ground water movement to the east by the installation and use of
new extraction wells and the use of MW-92. The existing French
drain system would impede ground water movement to the west and
south, and a reconditioned Reasor-Hill well would remove some
NAPL contamination.
Alternative 3 would provide source recovery from additional
wells in the central process area. Alternatives 2 and 3 would
not restore ground water to MCLs under the northern portion of
the CPA, under the landfills, or in downdip aquifers consisting
of correlative strata to these areas. Therefore, those
Alternatives would not attain the applicable ARARs, which are the
Safe Drinking Water Act's (SDWA's) MCLs found at 40 CFR §§ 141.11
- 26. Removal of all source NAPL and residual product in the
bedrock is not technically achievable. However, due to the fact
that NAPL extraction is technically impracticable, which fact
prevents this ROD from addressing the principal threat in
question, the purpose of Alternatives 2 and 3 is to prevent
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contaminants from migrating off-site, where contact pathways may
exist. For these reasons, a waiver from meeting MCLs in these
areas, based on a waiver for reasons of technical
impracticability, was invoked. Nonetheless, Alternatives 2 and 3
are protective of human health and the environment due to the
fact that they prevent contact with contaminated ground water.
3. LONG TERM EFFECTIVENESS AND PERMANENCE
The long term effectiveness of remedial actions for ground
water can best be measured by the ability of the remedial
technologies to prevent migration of site-related contaminants to
off-site areas. Alternatives 2 and 3 would provide long term
containment for contaminated ground water in the eastern part of
the site, while existing site hydrology and systems installed as
part of the 1984 Court Order will retard ground water movement in
other directions. A ground water monitoring program will verify
that the selected remedy is effective.
Additional source recovery in Alternative 3 may have a
positive effect on long term ground water quality but is
dependent on the volume of higher concentration contaminants
removed relative to the volume of unrecoverable source material
that will remain in the rock. The additional NAPL removed under
Alternative 3 would not significantly improve the overall ground
water quality when compared to Alternative 2 due to the large
volumes of NAPL waste that will remain in the subsurface even if
Alternative 3 were implemented. Alternative 1 would not provide
for control of ground water migration to the east, and therefore
does not present a long term solution.
4. REDUCTION OF TOXICITY, MOBILITY, OR VOLUME OF THE
CONTAMINANTS THROUGH TREATMENT
No significant reduction in the toxicity, mobility, or
volume was expected from the implementation of Alternative 1.
The mobility of dissolved-phase contaminants would be restricted
by the existing systems in the west and south, but would continue
to be uncontrolled to the east. Alternatives 2 and 3 will
control the mobility of ground water moving to the east, and will
reduce the toxicity of the collected ground water and the
recovered product from the Reasor-Hill well by treatment. The
installation and operation of additional source recovery wells in
Alternative 3 would represent an increased reduction in the
toxicity, mobility, and volume, when compared to Alternative 2.
However, due to the technical impracticability of extracting the
NAPLs, which constitute the principal threat, treatment of such
material is not practicable. Nonetheless, Alternatives 2 and 3
result in the containment and confinement of the contaminated
ground water, which is fully protective of human health and the
environment.
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5. SHORT TERM EFFECTIVENESS
No additional short term impacts were expected from
implementation of Alternative 1. The implementation of
Alternatives 2 and 3 will result in a few short term impacts.
Typically these will include Work-related hazards experienced by
site workers during the installation of the extraction well
system and the reconditioning of the Reasor-Hill well. The
impacts associated with the drilling of the extraction wells and
the redrilling of the Reasor-Hill well are the same as the
impacts encountered during the installation of monitoring wells
and soil borings during the remedial investigation. Underground
utility maps will be reviewed prior to well installation to
verify that there is no possibility of penetrating active utility
lines. Appropriate personal protection equipment will be used to
prevent exposure to contaminated ground water or NAPLs that may
be encountered during well installation activities.
6. IMPLEMENTABILITY
No implementation issues are applicable to the no action
alternative. Alternatives 2 and 3 are administratively and
technically feasible, to the extent that ground water retraction
and containment are concerned. General construction techniques
will be required to install the extraction wells and recondition
the Reasor-Hill well. Pump testing of the ground water
extraction wells will be implemented to verify that proper
hydraulic influence is obtained. The steps taken during the
reconditioning of the Reasor-Hill well will vary depending upon
the conditions encountered in the well. The implementation of
source recovery measures as part of Alternative 3 would need to
be performed in a phased approach, with each well being evaluated
to determi e the best source recovery method.
7. COST
The capital costs associated with these alternatives ranged
from $939,000 for Alternative 2 to $1,367,000 for Alternative 3.
Annual operations and maintenance (O&M) costs ranged from
$126,000 for Alternative 2 (year 1) to $169,000 for Alternative 3
(year 1). Net present value of the alternatives over a 30 year
period is estimated to be $2,525,000 for Alternative 2 and
$3,550,000 for Alternative 3.
Alternative 1 is the least expensive of the three
alternatives examined, but does not meet any of the other
evaluation criteria. Alternative 3 is more expensive than
Alternative 2, and is similar to Alternative 2 in relation to the
evaluation criteria, except that it may provide some additional
long term reduction in toxicity and mobility of site compounds.
Additional benefit gained from Alternative 3 over Alternative 2
in relation to the costs expended is problematic, due to the fact
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that NAPLs are present in fractured bedrock and will provide a
source of ground water contamination for the foreseeable future.
Extraction of NAPLs from fractured rock systems using current
technologies has not met with much success.
8. STATE ACCEPTANCE
The ADPC&E reviewed copies of the remedial investigation,
the baseline risk assessment, the feasibility study and the
Proposed Plan and has provided technical support on all efforts
involving OU3. ADPC&E concurs with the selection of Alternative
2 as the preferred remedy for the site (see Appendix B).
9. COMMUNITY ACCEPTANCE
EPA solicited input from the community on the remediation
alternatives proposed for the ground water contamination at the
site. Community comment was an important consideration in the
final evaluation of the remedial alternatives. No comments
opposing EPA's proposed remedy were received. All comments
received during the public comment period and at the public
meeting are addressed in the Responsiveness Summary of this ROD,
which is included as Appendix A.
9.0 THE SELECTED REMEDY
EPA has considered the requirements of CERCLA, the detailed
analysis of the alternatives using the nine evaluation criteria,
consultation with the Arkansas Department of Pollution Control
and Ecology, and public comments in selecting the preferred
remedial alternative for OU3. The preferred alternative is
Alternative 2, which involves the installation of extraction
wells in the CPA to hydraulically control the off-site migration
of contaminated ground water to the east, the continued operation
of the existing French drain system to impede ground water
contaminant migration to the south and west, and the proposed use
of the Reasor-Hill well and MW-92 as additional extraction wells.
These latter two wells will also help remove contaminants from
the center of mass.
Additional source removal efforts were not pursued in the
preferred remedy because of the extremely complex hydrogeological
conditions at the site and the lack of existing technologies that
are effective in extracting NAPLs from a tilted, fractured
bedrock system. The Reasor Hill well contains the thickest
occurrence of NAPL identified at the site during the Remedial
Investigation (approximately 1 foot of LNAPL). Minor source
removal from a few other selected wells would not materially
affect the long term ground water remediation effort at the site
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in relationship to the cost expended. Specifically,
implementation of Alternative 3 would not achieve MCLs for ground
water in the northern part of the Central Process Area or in the
areas of the old landfills because large quantities of NAPLs
would remain in the subsurface in these areas. Due to the fact
that it is technically impracticable to extract those NAPLs, it
is not possible to attain the MCLs set out at 40 CFR §§ 141.11-
26. Therefore, as explained in detail at Section 10.2 below,
this ROD formally waives those MCLs as applicable ARARs due to
the technical impracticability of achieving them. Nonetheless,
the selected remedy is protective of human health and the
environment since it results in the containment of contaminated
ground water, which poses a relatively low long term threat.
Such a containment strategy is consistent with Section
300.430(a)(iii)(B) of the NCP, 40 CFR § 300.430(a)(iii)(B), which
states:
EPA expects to use engineering controls, such as
containment, for waste that poses a relatively low long term
threat or where treatment is impracticable.
NAPLs will provide a long term source for dissolved phase
contamination. Therefore, based on the nature of the
contaminants and the complex subsurface geology at the Vertac
site, EPA has concluded that meeting MCLs in this area will not
be possible in the foreseeable future. In addition, the ADPC&E
has agreed with this conclusion. Finally, the contaminated Atoka
aquifer exhibits low ground water deliverability and is generally
not used as a water source in the area. Therefore, a reasonably
anticipated future ground water use scenario does not involve the
use of the Atoka as a future drinking water source.
Therefore, for the reasons stated above, taking into account
the land and ground water use controls that can and will be
implemented within the site confines, containment, versus
restoration, is the goal of the preferred alternative. In order
to implement a containment remedy, a technical impracticability
waiver from meeting MCLs is warranted for aquifers beneath the
CPA, the landfills, and correlative downdip strata to those
comprising these aquifers.
Nonetheless, the preferred alternative will allow the
possibility that other areas of the site, i.e., east of the
central process area, and possibly some areas south of the
central ditch, could remain above MCLs and PCLs. EPA will
establish the exact location of the monitoring wells that will be
used to monitor PCLs during the remedial design phase of the
project. If during the implementation and operation of the
ground water remedy, contaminants of concern are found to exceed
the PCLs defined in Table 23 at monitoring wells to be identified
based on the additional studies at the site, additional ground
water monitoring and remediation efforts will be required to
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ensure that contaminants do not exceed MCLs beyond the
established site boundary.
Initially, if PCLs are exceeded, then site contaminant
monitoring will increase from semi-annually to quarterly. If
contaminant concentrations remain the same or increase during the
following 4 quarterly sampling events, additional ground water
containment measures will be considered necessary. Such measures
would be consistent with those established in the preferred
alternative, and would include, but not be limited to, changing
pumping rates on existing ground water extraction system and/or
installing new or reworking existing wells to provide better
contaminant capture and control.
10.0 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, 42 U.S.C. § 9621, also
requires that the selectee" remedial action comply with applicable
or relevant and appropriate environmental standards established
under Federal and State environmental laws, unless a waiver is
granted. The selected remedy must be cost-effective and utilize
permanent solutions and alternative technologies or resource
recovery technologies to the maximum extent practicable. The
Superfund statute also contains a preference for remedies that
employ treatment that permanently and significantly reduce the
volume, toxicity, or mobility of hazardous wastes as a principal
element. The following sections discuss how the selected remedy
meets the statutory requirements.
10.1 PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
The selected remedy is protective of human health and the
environment. The remedial action objectives and goals specified
in section 6.5 of this ROD will be met.
The remedy for the site ground water is protective of human
health and environment because:
1) Contaminated ground water beneath the site will be contained
on-site by use of the existing controls and by ground water
production from selected existing wells on-site and
additional wells to be installed following the remedial
design phase. By containing ground water on-site using
proven and reliable technology, the possibility of direct
contact off-site is eliminated.
2) Deed restrictions will be established for the site that
would include a prohibition against installing water wells
at the site other than those associated with the ground
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water containment remedy. Deed restrictions are easily
implemented and would provide legally binding controls to
ensure that the site ground water would not be used for
domestic purposes in the future. In addition, EPA will
discuss with the City of Jacksonville the possibility of the
City's imposing specific land use controls, such as enacting
zoning ordinances that would prohibit the installation of
water wells both on-site and areas immediately off-site
where ground water wells could affect the on-site
containment efforts.
10.2 TECHNICAL IMPRACTICABILITY WAIVER
As reflected in Hercules, Inc's., September 1996 report
titled "Request for Technical Impracticability Waiver for
Operable Unit 3, Vertac Site, Jacksonville, Arkansas - Final",
which is found in the administrative record for OU3, removal of
all source NAPL and residual product in the bedrock is not
technically achievable because of the complex geology and
hydrology of the site, and due to the nature of the
contamination. For this reason, and as discussed in greater
detail below, the Agency hereby waives applicable ARARs under the
Safe Drinking Water Act (SDWA), 42 U.S.C. § 300f e± sejj., for
areas where substantial NAPL contamination exists. As discussed
at Section 7.2.1 of this ROD, those SDWA applicable requirements
are the National Primary Drinking Water Standards, which are
expressed as maximum contaminant levels (MCLs) and are set out at
40 CFR §§ 141.11-26). Ground water resources in the contaminated
aquifer are not currently used nor are they expected to be used
as a drinking water source in the general vicinity of the Vertac
site. The areas of the site affected by this waiver include
those beneath the northern part of the CPA, the areas beneath the
landfills addressed by the 1984 Court order, and down-dip
correlative strata of formations in these areas. Areas included
in the waiver are shown in Figure 12. Ground water beneath
portions of the site outside of the areas subject to the waiver
may meet MCLs in the future, based on implementation of the
ground water remedy. A detailed discussion of EPA's rational for
applying this waiver follows.
Remedial Investigations performed on the site have shown
the site to be contaminated with both LNAPLs and DNAPLs, which
occur beneath several areas of the site. Based on information
gathered on historical waste disposal and handling practices, and
on technical information from the remedial investigations, the
EPA is aware that substantial volumes of NAPLs exist in the
subsurface of the site.' Mahy of these wastes have very high
viscosities, which means that they are in an almost solid state
at the temperatures in the near subsurface. As discussed
previously, porosity in aquifers of the Atoka Formation is
dominated by fracture porosity within the sandstone units.
Additionally, the NAPLs are relatively insoluble. Due to these
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i J
I WM\X/-43 '
^MW-22
Legend
^MW-57 Monitoring Well
. _ _ French Drain
Slurry Wall
^_~~^__ Fence Line
LI^_ Property Boundary
^i>u±i£j.i Central Process Area Boundary
Central Ditch
w-
Scale \n Feet
Source. V/en^t Si[e Bod.id^ry
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characteristics, using currently available conventional or
innovative extraction technologies, coupled with the low pump
rates encountered in the site's subsurface, restoration of ground
water is not technically practicable.
Currently there are no proven remedial technologies for
completely removing subsurface DNAPL in reasonable timeframes
other than excavation. Excavation will be used to remove some
ground water contaminant sources such as the tetrachlorobenzene
(TCB) spill area as part of soil remediation at the site
(Operable Unit 2). However, EPA does not believe excavation of
all NAPL sources at the site is feasible due to the widespread
nature of NAPL contamination, the existence of NAPLs in fractured
bedrock, and the depths at which the contaminants are found.
Conventional pump and treat technologies are generally
ineffective at removing NAPL wastes in a fractured bedrock
setting. Surface tension, relative insolubility, and high
viscosity of NAPL wastes, as well as limited communication
between fractures, are specific factors that make restoration of
the Vertac aquifer using conventional pump and treat methods
impracticable. Although some technologies exist which are
designed to mobilize DNAPLs for removal, the Agency does not
believe these technologies would be successful if implemented at
the site. These technologies involve the injection of
surfactants, alkaline agents, polymers, solvents, or steam into
the aquifer to mobilize NAPL. The liquids are then produced
along with NAPL through extraction wells. A potential risk with
using these methods is that they may increase the risk posed by
the contaminants by making them more mobile and thus increasing
the potential for off-site movement.
^ ; direction of movement of PNAPL wastes is not necessarily
the same as the ground water flow direction. Instead, since
these wastes are more dense than ground water, they tend to move
downward through the aquifer as a result of gravitational forces.
At the Vertac site it is possible that DNAPL waste may move along
fractures and/or bedding planes in a down-dip direction toward
the north. For this reason, the Agency is including some down-
dip strata, correlative with contaminated strata in the northern
CPA and the landfills, in the waiver as shown in Figure 12.
Specifically, the Agency is including a downdip distance
equivalent to a horizontal distance of 250 feet. It is believed
that the volume of DNAPL waste disposed at the Vertac site will
be captured within the fracture system within this down-dip
distance.
CERCLA Section 121(d)(2)(A), 42 U.S.C. § 9621(d)(2)(A),
states that CERCLA response actions that involve hazardous
substances remaining on-site shall attain legally applicable, or
relevant and appropriate substantive requirements of Federal or
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state law (ARARs). However, in pertinent part, CERCLA Section
121(d)(4)(C), states:
The President may select a remedial action meeting the
requirements of paragraph (1) that does not attain a level
or standard of control at least equivalent to a legally
applicable or relevant and appropriate standard,
requirement, criteria, or limitation as required by
paragraph (2) (including subparagraph (B) thereof), IT the
president finds that-
(C) compliance with such requirements is technically
impracticable from an engineering perspective...
In addition, Section 300.430(f)(2)(C) of the NCP, 40 CFR §
300.430(f)(2)(C)f states:
An alternative that does not meet an ARAR under federal
environmental or state environmental or facility siting laws
may be selected under the following circumstances:
(3) Compliance with the requirement is technically
impracticable from an engineering perspective...
As discussed above, currently available conventional and
innovative technology cannot practicably extract both the NAPL
and DNAPL components of the contaminated ground water found at
the site so as to attain the SDWA MCLs. However, aggressive
ground water pumping within the site's confines as selected in
Alternative 2 is a technically feasible means to contain the
contaminated ground water plume. NCP Section
300.430(a)(1)(iii)(F), 40 CFR § 300.430(a)(1)(iii)(F), states:
EPA expects to return usable ground waters to their
beneficial uses wherever practicable, within a timeframe
that is reasonable given the particular circumstance of the
site. Where restoration of ground water to beneficial uses
is not practicable, EPA expects to prevent further migration
of the plume, prevent exposure to the contaminated ground
water, and evaluate further risk reduction.
The source containment strategy described in Alternative 2
and selected in this ROD effectuates the primary objective for
any CERCLA remedy, which is overall protectiveness, which it will
attain by preventing exposure to the contaminated ground water.
This remedy is also entirely consistent with the NCP passage
cited above. Such source containment will also contribute to the
long term management of contaminant migration by limiting the
further contamination of ground water and the spread of
potentially mobile sources, such as NAPLs. In addition,
effective source containment may permit the restoration of that
portion of the aqueous plume that lies outside of the containment
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area by preventing continued contact with the contaminated plume.
Finally, effective containment may facilitate the future use of
new remedial technologies that may become available which could
provide a permanent remedy for the NAPL problem without
increasing the risk of off-site migration (which is a risk that
recently developed technologies for NAPL removal pose).
Finally, the aggressive ground water containment remedy
selected in this ROD will permit the remediation of the aqueous
plume that will be extracted, treated, and discharged into Rocky
Branch Creek after meeting applicable State water quality
criteria. By pumping and treating the contaminated ground water
and discharging the treated ground water into Rocky Branch Creek
(versus reinjecting the treated ground water), the remedy
selected will prevent the further spread of contaminated ground
water, and will result in the reduction of the aqueous plume's
size. Such a plume size reduction will ultimately cause the
plume to contract, thereby preventing the plume from encroaching
outside of the site's boundaries.
Therefore, for the reasons stated above, EPA hereby waives
as an ARAR for the portions of the ground water remedy shown in
Figure 12, the SDWA's maximum contaminant levels (MCLs) set out
at 40 CFR §§ 141.11 - 26, due to the technical impracticability
of attaining those standards. However, EPA believes that the
source containment remedy selected herein is fully protective of
the human health and the environment because it will prevent
further migration of the plume, prevent exposure to the
contaminated ground water, and will permit EPA to evaluate
further risk reduction technologies that may emerge in the
future.
10.3 COMPTTANCE WITH ARARs
The selected remedy will comply with all location- and
action-specific ARARs. Extracted ground water will be treated in
an on-site treatment plant, which will be required to comply with
applicable discharge requirements. The Reasor-Hill well will be
reconditioned, if necessary» and used for source recovery to
remove NAPLs. Therefore, closure requirements under SDWA and
Arkansas Regulation No. 17 are not applicable.
The remedy may comply with the chemical-specific
requirements of the SDWA to the east and north of the central
process area, as well as some areas south of the central ditch
and east of the landfills. In these areas, the primary ground
water concern relates to dissolved-phase, site-related compounds.
The proposed pump and treat system should draw these compounds
towards the extraction for collection and treatment.
The selected remedy will not comply with the chemical-
specific requirements of the SDWA in the northern portion of the
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CPA and in the areas of the landfills. Residual product trapped
interstitially in pore spaces in the weathered bedrock and within
fractures in the fresh bedrock beneath these areas will act as
continuous sources of dissolved-phase contamination. Therefore,
as discussed in Section 10.2 above, a waiver from meeting these
requirements based on technical impracticability is warranted.
The remedy will comply with all substantive requirements
associated with the operation of a waste water treatment plant
and with the treatment and discharge of ground water into Rocky
Branch Creek under State and Federal law as described at Sections
7.2.1 and 7.2.2 above.
In addition, the implementation of the remedy will also
comply with all substantive requirements applicable to the
development and operation of extraction wells. Finally, any well
cuttings generated during the development of the extraction and
monitoring wells that are determined to exceed the 5 ppb cleanup
level selected for soil and debris in the ROD for OU2 will be
disposed of in the on-site RCRA Subtitle C landfill or in a
manner that meets applicable requirements. As discussed in the
ROD for OU2, the on-site disposal of such soils and debris do not
invoke the RCRA land disposal restrictions because placement
within the disposal unit will not occur. However, as also
discussed in the ROD for OU2, the construction and operation of
the on-site RCRA Subtitle C landfill will comply with all
applicable substantive RCRA requirements.
10.4 COST EFFECTIVENESS
The selected remedy for Operable Unit 3 is cost effective
and is fully protective of human health and the environment based
on future land use objectives. Section 300.430 (f)(ii)(D) of the
NCP, 40 CFR § 300.430(f)(ii)(D), requires EPA to determine cost-
effectiveness by evaluating the following three of the five
balancing criteria to determine overall effectiveness: Long-term
effectiveness and permanence, reduction of toxicity, mobility, or
volume, and short term effectiveness. Overall effectiveness is
then compared to cost to ensure that the remedy is cost
effective. EPA believes that the selected remedy meets these
criteria.
The estimated present worth cost for the selected remedy for
ground water is $2,525,000. The variation in remedy costs
evaluated for ground water ranged from $2,525,000 for Alternative
2 the selected remedy, to $3,550,000 for Alternative 3, which
constitutes the selected remedy plus the extraction of some
additional NAPLs. Even though the selected remedy does not
provide for a restoration of site ground water, the containment
measures mentioned above will prevent site contaminants from
moving off-site to possible receptors.
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10.5 UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE
TREATMENT TECHNOLOGIES TO THE MAXIMUM EXTENT PRACTICABLE
EPA has determined that the selected remedy represents the
maximum extent to which permanent solutions and treatment
technologies can be utilized in a cost-effective manner for this
operable unit. EPA's selected remedy will prevent contamination
of off-site ground water by containing contaminated ground water
beneath the site.
Of those alternatives that were protective of human health
and the environment, and that comply with ARARs, EPA has
determined that the selected remedy provides the best balance in
terms of long-term effectiveness and permanence, reduction in
toxicity, mobility, or volume achieved through treatment, and
taking into consideration short-term effectiveness,
implementability, costs, and State and community concerns.
As discussed earlier in this ROD, it is technically
impracticable to address through extraction and treatment NAPLs,
the principal threats to the ground water using conventional or
innovative technologies. However, having made that
determination, EPA's selected remedy does address the
contaminated ground water by containing it and by preventing
further ground water contamination and migration. In addition,
the implementation of the remedy will result in the treatment to
Arkansas State water guality standards of that component of the
ground water plume extracted from the aquifer. Also, by
confining the ground water plume within the site's boundaries,
the remedy will allow for the possibility of utilizing some
future technology that may be capable of effectively addressing
the NAPL principal threat material. Finally, because
implementation of this remedy will result in the NAPLs remaining
in place, CERCLA Section 121(c), 42 U.S.C. § 9621(c), requires
that EPA review the OU3 remedial action no less than each five
years after the remedy is initiated. Thus, should an effective
technology emerge, EPA is required by that section of CERCLA to
assess its applicability within the five-year review process.
10.6 PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT
As discussed above, it is technically impracticable to treat
the principal threat posed by the NAPLs. However, it is not
necessary ox- appropriate for the OU3 remedy to meet the general
statutory preference for treatment as a principal element because
EPA has already acknowledged that it is technically infeasible to
do so. However, it is possible to address the long term low
level threat the contaminated ground water poses and to prevent
further ground water contamination and off-site migration through
the containment remedy selected herein. This containment remedy
does conform with the NCP's preference for implementing such a
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containment remedy where treatment is impracticable or where a
contaminated medium, such as the ground water at issue here,
poses a relatively low long term threat. See NCP Section
300.430(a)(iii)(B), 40 CFR § 300.430(a)(iii)(B). The containment
remedy will essentially result in a "pump and treat" remedy for
contaminated ground water outside of the areas of the Technical
Impracticability waiver.
EPA has determined through its evaluation of site data and
the remedial alternatives that the extent to which treatment
should practically be employed (i.e., restoration of the entire
contaminated aquifer beneath the site) is none.
11.0 DOCUMENTATION OF SIGNIFICANT CHANGES
There are no significant changes in this ROD from the
original proposed plan to address contaminated ground water at
the Vertac site.
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