United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R07-93/071
May 1993
PB94-964304
v>EPA Superfund
Record of Decision
Syntex Facility, MO
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RECORD OF DECISION
GROUND WATER OPERABLE UNIT * 2
SYNTEX AGRIBUSINESS, INC.
VERONA, MISSOURI
Prepared by:
U.S. ENVIRONMENTAL PROTECTION AGENCY
April 8, 1993
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RECORD OF DECISION DECLARATION
SITE NAME AND LOCATION
The Syntex Agribusiness, Inc. site is located west of the
city of Verona in Lawrence County, Missouri.
STATEMENT AND BASIS OF PURPOSE
This decision document represents the selected remedial
action for the ground water at the Syntex Agribusiness, Inc. site
near Verona, Missouri. This remedy was chosen in accordance with
the Comprehensive Environmental Responsibilities, Compensation,
and Liabilities Act (CERCLA), as amended by the Superfund
Amendments Reauthorization Act (SARA), and to the extent
practicable, the National oil and Hazardous Substances Pollution
Contingency Plan (NCP). This decision is based on the
administrative record for this site. The remedial action
activities conducted under operable unit 1 at the site greatly
mitigated the potential threat to public health and the
environment from this site. The selected remedy for this
subsequent ground water operable unit is to take no further
action at this time with continued ground water monitoring.
DECLARATION
EPA believes that no further remedial action is necessary
for ground water at the site to ensure protection of human health
and the environment. Previous and ongoing remedial responses
under operable unit 1 have greatly reduced the threat from past
sources of contamination. Ground water contaminant levels at
this site are within the acceptable risk range established by
the NCP.
Ground and surface water monitoring will continue for two
years following the issuance of this record of decision. An
assessment will be conducted by EPA at the end of the monitoring
program to ensure that this remedy remains protective of human
health and the environment.
A five-year review for this operable unit will be performed
as hazardous substances, pollutants, or contaminants remain at
the site. A separate five-year review will be conducted in 1993
for the remedial action for operable unit 1 which was initiated
in 1988.
, ./i(
,/ ill iam W. Rice
/ Act' g Regional Administrator
)/?f7J--
. ~, e
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DECISION SttMMARy
SITE DESCRIPTION
The Syntex Agribusiness, Inc. facility is located west of
the city of Verona, (population SOO) in south-central Lawrence
county in extreme southwest Missouri. The facility occupies
approximately 180 acres, primarily along the east bank of the
spring River (Figure 1), which flows northward through the length
of the property.
Most of the active portion of the facility is located within
protected areas of the 100-year Spring River floodplain. The
area is characterized by karst topographic features such as
solution cavities and springs. The maximum floodplain elevations
(1260 feet above Mean Sea Level (MSL» occur at the south end of
the property, decreasing to approximately 12S2 feet MSL near the
northern property boundary at a gradient of approximately 0.002
feet/mile. The highest elevations on the property are located
west of Spring River where bluffs rise to approximately 13S0 feet
near the north end of the trench area.
The industrial facility is surrounded on three sides by
property used for agricultural purposes. A predominantly
. residential setting is located to the east of the site in the
city of Verona. Scattered residences are located within the
Spring River floodplain down-gradient from the site. The Spring
River is used for recreational and industrial purposes within
southwestern Missouri.
SITE HISTORY AND ENFORCEMENT ACTIVITIES
In the 1960's, Hoffman-Taff, Inc. owned and operated the
facility at Verona, Missouri. Hoffman-Taff produced 2,4,S-
trichlorophenoxy-acetic acid (2,4,S-T) for the u.S. Army as part
of the production of the defoliant commonly known as Agent
Orange. In 1968, Hoffman-Taff leased a portion of a building at
the facility to Northeastern Pharmaceutical and Chemical Company
(NEPACCO) for the production of hexachlorophene. In 1969, Syntex
Agribusiness, Inc. (Syntex) purchased the facility from Hoffman-
Taff at Verona.
The production of 2,4,S-T and hexachlorophene involved the
intermediate production of 2,4,S-Trichlorophenol (TCP) and
subsequently the potential formation of 2,3,7,8-
tetrachlorodibenzo-p-dioxin (dioxin). However, these materials
were removed from the pharmaceutical grade hexachlorophene, thus
producing waste streams containing TCP and dioxin. These waste
streams were managed in storage tanks and lagoons located onsite.
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Figure 1.
site Location Map
A Consent Order was signed between EPA and syntex pursuant
to section 3013 of RCRA 42, U.S.C. 66934, on August 6, 1982. The
agreement provided for 1I...monitoring, testing, analyses, and
reporting regarding the disposal areas on the Facility.1I
2
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A subsequent administrative order on consent between Syntex
and EPA was signed September 6, 1983, pursuant to Section 106 of
CERCLA, 42 U.S.C. 09607, and Section 3013 of RCRA, 42 U.S.C.
06934. The order required the following actions:
posting of warning signs around specified disposal areas:
development and submittal of a sampling and Analysis Plan
(SAP) to define the nature and extent of dioxin
contamination:
implementation of the SAP upon approval by EPA:
development and submittal of a Fish and Sediment Sampling
Plan for the dioxin contamination in Spring River:
implementation of the Fish and Sediment Sampling Plan upon
approval by EPA:
preparation and submittal of a Remedial Alternatives Report:
preparation and submittal of an implementation plan that
would include plans and specifications for the preferred
remedial alternative(s), schedule for implementation and
reporting, description of the necessary reports and safety
plans.
In May 1988, EPA issued a Record of Decision (ROD) that
selected remedial actions for cleanup of contaminated soils and
equipment at the facility and associated ground water monitoring. .
Pursuant to the 1983 administrative order, EPA, the Missouri
Department of Natural Resources (MDNR) and Syntex developed an
Implementation Plan to achieve the cleanup measures proposed in
the ROD for operable unit #1 (OU 1).
In accordance with the ROD, dioxin-contaminated soils from
four areas within the Spring River floodplain (Figure 2) were
excavated and transported to the EPA Mobile Incineration System
for thermal treatment and disposal. The excavated areas were
then backfilled with clean topsoil and a vegetative cover was
established. Remediation of contaminated soils located east of
Spring River was completed in 1989.
Dioxin-contaminated soils associated with the trench area
located on bluffs west of Spring River were capped in place with
a 12-inch clay layer and an overlying 12-inch topsoil layer which
has supported a vegetative cover. In addition, a gravel drainage
interception channel was installed upgradient of the trench area.
A five-year review will be conducted in 1993 for the remediation
of the dioxin-contaminated soils conducted under the ROD for
OU 1.
3
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Figure 2. Former Areas of Dioxin Surface contamination
The Implementation Plan included land-use restrictions at
the site to maintain an industrial-use status for the property.
Additionally, the site is included on the state of Missouri
Registry of Abandoned or Uncontrolled Hazardous Waste Disposal
Sites.
4
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COMMUNITY PARTICIPATION
Public participation in the selection of a final remedial
action for the Syntex Agribusiness site in Verona, Missouri began
with the release of the Syntex "Remedial Alternatives Report,"
EPA's "Proposed Plan for Final Management of Dioxin contaminated
Soil and Equipment, Syntex-Verona" and Administrative Record on
March 21, 1988. The Syntex-Report evaluated remedial
alternatives for the dioxin-contaminated soil and equipment and
presented general plans for future monitoring of ground water.
The ROD for operable unit 1 provided for the excavation and
treatment above an action level of 20 parts per billion (ppb)
dioxin in surface soils and maintenance of a vegetative cover
over soils containing between 1 ppb and 20 ppb dioxin.
Ground water data collected from the monitoring well network
was presented for public comment in the Remedial Investigationj
Feasibility Study (RIjFS) prepared by Syntex for the ground water
operable unit. The RIjFS and the Proposed Plan for OU 2 were
released for public review and comment on August 11, 1992 through
september 10, 1992. A public meeting was held on August 18,
1992, to present and discuss the Proposed Plan for the ground
water operable unit. Response to comments received on the
selected remedy at the public meeting and during the public
comment period are included in the attached Responsiveness
Summary.
The documents EPA relied upon for selecting this remedial
alternative are included within the Administrative Record. A
repository for the administrative record file has been
established at the Lawrence County Courthouse in Mt. Vernon,
Missouri for public review.
SCOPE AND ROLE OF THE OPERABLE UNIT
The OU 1 ROD stated that existing ground water data was
insufficient to determine ground water remediation needs at that
time. The ROD required further monitoring to characterize the
nature and extent of potential ground water contamination at the
site. Accordingly, additional ground water monitoring wells were
installed at the facility to obtain the necessary data upon which
to base a decision.
An operable unit is a discrete action that comprises an
incremental step towards comprehensively addressing site
problems. At this site, EPA has defined the soils and equipment
remediation as OU #1 and the ground water investigation as OU #2.
Ground water monitoring of the uppermost aquifer (alluvium/
5
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shallow carbonate bedrock) beneath the Syntex Verona Facility
began in 1985 following installation of monitoring wells MW-1
through MW-10 in the floodplain alluvium (Figure 3). Monitoring
was performed to detect potential releases, if any, of volatile
organic contaminants to the shallow ground water at the site
through 1988. Several organic compounds were tentativeiy
identified in the ground water at the site.
Subsequent to the 1988 ROD for OU 1, the Verona
Implementation Plan was developed to define additional ground
water characterization needs, determine the effectiveness of
soils remediation for OU 1, provide post-remediation monitoring,
and to characterize ground water flow beneath the site.
To determine whether further remedial action was necessary
with respect to the ground water, eleven additional monitoring
wells (Figure 3) were installed at the site. The resulting 21-
monitoring well network has been used to help determine the flow
characteristics of ground water at the site and to more
accurately define the extent of low-level organic and inorganic
constituents in the ground water at the site. Several floodplain
monitoring wells have been sampled on a quarterly basis since
1989.
SITE CHARACTERISTICS
The facility overlies alluvial deposits which rest
unconformably upon an eroded carbonate bedrock surface. The
alluvium consists of fine to coarse-grained clastic sediment
ranging from 10 to 30 feet in thickness. The alluvial deposits
are underlain by carbonate bedrock which consists of fractured
cherty limestone. The Northview Shale which underlies the
carbonate bedrock, acts as a confining bed for vertical ground
water movement in this area. The thickness of the shallow
bedrock is controlled largely by position of its erosional
surface, and is approximately 90 feet in thickness below the
facility. There is no confining layer between the alluvium and
the shallow bedrock suggesting that these two units act as a
single aquifer.
static water measurements from alluvial monitoring wells
MW-1 to MW 10 were used to determine the potentiometric surface
of the shallow unconfined aquifer. The data collected indicates
that ground water flow in the alluvial aquifer moves in a north-
northwesterly direction at the site (Figure 4). The direction of
qround water flow may be influenced by the presence of a buried
channel which parallels the spring River at the site.
6
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Figure 3. Site Monitoring Well Location Map
7
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Ground Water Flow
Ground water flow velocity data was also collected from
monitoring wells MW 1-10. These tests indicate pydraulic
conductivities that range from 4. 78X10" to 9x10' em/see (Table
1). These values are consistent with typical hydraulic
conductivities for deposits consisting of silty sands and
gravels. Ground water flow velocities for the bedrock aquifer
were significantly lower than those of the a~uvial aqu;!er, with
hydraulic conductivities ranging from 3.9x10' to 8.9x10 em/see
(Table 2). These low conductivities suggest that ground water
flow in the bedrock aquifer is likely controlled by fracture
porosity where wide variations in velocity may exist depending on
the extent of fracturing in a particular section.
8
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Well*
MW-l
NTW-2
MW-3
MW-4
MW-5
MW-6
NfW-7
MW-8
MW-9
MW-10
Calculated KCcm/sec)
From Slug Testing
1.19
2x
x 10s
10'2
3.9 x 10°
2x
1 X
4x
9x
4.78
123
538
io-2
io-2
1C'2 1
io-2
x icr1
x icr2
x 10'3
Table 1. Slug Test Results of the Alluvial Section of
the Shallow Aquifer
WeD
MW-12
MW-12
MW-12
MW-13
MW-13
MW-13
MW-17
MW-17
MW-17
Kern/sec
1.1 x icr6
5.4 x ID"6
12 x itr6
83 x IO-7
3.9 x 1CT7
6^ x IO-7
6.4 x lO*7
8.9 x W*
6.0 x 1(T7
Table 2. Estimated Hydraulic Conductivity of Bedrock Based
on Packer Test Results
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Ground water monitoring to characterize the water quality of
the shallow aquifer began in October 1985, following installation
of monitor wells MW-1 through MW-10 in the floodplain alluvium.
Syntex was required to analyze ground water samples for the
following minimum list of parameters:
pH
Conductivity
Total Organic
Calcium
Magnesium
Chloride
Sulfate
Nitrate
Phenol
Arsenic
Barium
Chromium
Xylenes
Carbon
Lead
Manganese
Selenium
Sodium
Acetone
Dichloromethane
Toluene
Chlorobenzene
Ethylbenzene
1,4 Dichlorobenzene
Tetrachloroethane
Tetrachloroethene
Iron
A total of twenty-one wells have been installed at the
Verona site to collect physical and chemical data relating to
ground water flow and quality. Based on data collected prior to
1988, monitoring wells 6 and 7 were determined to be situated to
intercept contaminants downgradient from the potential source
areas.
Well #1 was originally designed
background concentrations. However,
indicates that it may be affected by
not truly represent background water
to determine ground water
analysis of data for well #1
on-site conditions and may
quality.
Ground water sampling results indicate the presence of
several volatile organic compounds which exceed Maximum
contaminant Levels (MCLs). Table 3 shows the volatile organic
compounds detected above MCLs in the wells which were sampled
between January 1991 and April 1992. MCLs for dichloromethane,
1,1 dichloroethane, and toluene were exceeded. MCLs are
standards utilized by municipal water supplies for safe drinking
water and are noted here for comparison purposes. In addition,
the compounds acetone and chlorobenzene, for which no MCLs are
available, have been detected in shallow ground water samples
(Table 4).
Nine inorganic constituents were detected in concentrations
above MCLs established for drinking water supplies. They include
arsenic, barium, cadmium, chromium, lead, selenium, antimony,
nitrate, and fluoride. Three additional inorganic analytes,
iron, chlorides and manganese, were present above secondary MCLs.
10
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Table 3
Volatile Organic Compounds Detected Above MCLs in Shallow Groimdwatcr Samples,
January 1991 to April 1992, Syntex Verona Facility
Well No.
MW-I
MW-2
MW-3
MW-4
MW-5
MW-6
MW-7
MW-8
MW-9
MW-IO
MW-II
MW-12
MW-I 3
MW-14
MW-I4A
MW-I 5
MW-I5A
MW-I5B
MW-16
MW-I6H
MW-17
MW-18
1/30/91
NO*
NS'"
NS
NS
Nl)
ND
ND
NS
ND
NS
ND
Dry -
Dry
ND
ND
ND
ND
ND
ND
ND
Dry
ND
Sampling Date
4/25/91
Dichloromelhane (1 10)"
NS
NS
NS
NS
Dichloromethane (441)
Dichloromethane (25)
NS
ND
NS
ND
Dry
Dry
ND
ND
ND
Dichloromelhane (364)
ND
ND
ND
Dry
Dichloromethane (66)
7/31/91
ND
NS
NS
NS
ND
ND
ND
NS
ND
NS
NS
Dry
Dry
Dichloromethane (603)
1,2-Dichloroethane (643)
ND
ND
ND
ND
Dichloromethane (1000)
Toluene (1000)
ND
Dry
NS
10/31/91
Dichloromethane (13)
NS
NS
NS
NS
ND
ND
NS
ND
NS
NS
Dry
Dry
ND
ND
ND
ND
ND
ND
ND
Dry
NS
1/28/92
ND
NS
NS
NS
ND
ND
ND
NS
ND
NS
NS
Dry
Dry
ND
ND
ND
ND
ND
ND
ND
Dry
NS
4/7/92
ND
NS
NS
NS
ND
ND
ND
NS
ND
NS
NS
Dry
Dry
ND
ND
ND
Dichloromethane (19)
ND
ND
ND
Dry
NS
' ND • None delected ihcwe MCL.
( ) - rnitcenlritiiin in
' NS - N<4 umpled.
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Table 4
-
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Well "0, IIJOI9I 4125191 1/J1191 1001191 IflII91 4f7m
MW-I Acetone (7J)" Acetone (1370) Acelon. (525) ND' ND ND
MW.2 NS ". NS NS
NS NS NS
MW.J NS 'NS NS NS NS NS
MW4 NS NS NS NS NS NS
MW.S Acetnne (22) NS Acelnne (69.1) Chlorubenuo. (18) Chlorub.nune (58) Chloruheauen. (51)
Cldomhenzene (JO) C.rtJon dilUlfid. (2 I)
M W -6 Chlorubenzene (2 I 5) Acelone ()470) Acetone (12,291) Acelone (22) Chlorubenz.ne (261) Chlorubenz- (224)
Ethylhenzell8 (2) ChlorolJenzen. (231) <"lIl..rohenzene (446) Ethylbenzell8 (21) Ethylbenzene (22)
Xylene. (76) Xylentl (21) Elhylbellun. (68) Xyl- (51) Xylene. (:11)
Toluene (27)
Xylene. (211)
MW-7 Acetone (II) Acetnne (12) Acelone (I 591) Actlone (10) Chlorubcnzene (12) Chlorubenzene (IS)
rhl..ruhe"zeIl8 (10)
MW.I NS NS NS NS NI NS
MW-9 Acetone (12) Chlunlhenzene (JJ) Acetone (199.1) Acelone (:IJ1) Chlombenzene (2]6) Chlorubenzene (217)
CIiI..r.lhelllClle (116) Chlnruhenune (162) Chlnn,benune (J05)
. Carbon di.ulfid. (28)
MW-IO NS NS NS NS NS NS.
MW-II Acelone (4949) Acetone (J9JO) NS NS NS NS
MW-12 Dry Dry Dry Dry Dry Dry
MW-IJ Dry Dry Dry Dry Dry Dry
MW-14 Acetone (:J106) Acetone (4470) Acetone (18,149) Acelone (55) ND ND
MW-14A Acelone (108]) Acelone (870) ND ND Acetone (:18) ND
MW-15 Acetone (J I) ND Acelone (2n8) ND ND ND
MW.15A Acelnne aO) Acetone (8290) Acelone (J 110) Acelono (14) ND ND
MW-15H Acetone (54) Acelone (560) Acelone (2585) Acelnne (4505) Chlorubenzene (57) Chlornbenun. (107)
Cltlnnohenulle (71) Chlurohellune (64)
Xylelltl (7)
MW.16 Acelo...e (556) Aceln..e (J30) Acelone (11,796) Acelnn" (246) ND ND
MWIIIII NI) Acel..ne (611)00) A«'nn" 8)71) Nil NI> Nil
MW.17 Ury Dry Ory Ury Dry Ory
MW.18 Acelone (46) Ace'one (960) NS NS NS NS
Other Volatile Organic Compounds Detected In Simllmv Groundwater Samples,
.January 1991 to April 1992, Syntex Verona Facility
. NU . Nnne del.~led.
.. ( ). Cnncenl..tliun in 'lg/l~.
... NS . N"t ..mr,.d.
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Upon review of the ground water analytical data, it appears
that an inexactly defined area of metals and organic ground water
contaminants is present at various times at a location
downgradient of the former au 1 contaminated soils areas. The
affected area is located north of the waste water treatment plant
and former Lagoon Area, and is approximately bounded to the east
and west by the former Slough Area and Spring River,
respectively. Acetone, dichloromethane, and chlorobenzene were
among the organic contaminants most commonly detected in
monitoring wells in this area (MW-5, 6, 7, 9, 15, 15A, 1SB, 16,
and 16B). In 1989, dioxin was reported at 5.3 part per trillion
(ppt) from well 16. However, since dioxin has not been
consistently found in the ground water and was not evaluated in
the risk assessment, further monitoring will be conducted to
better define its presence. Acetone and chlorinated solvents,
such as dichloromethane and chlorobenzene, are volatile
compounds. As such they readily volatilize during transport.
These compounds also readily biodegrade in waste water treatment
processes and may biodegrade in ground water. The lack of
persistence exhibited by these compounds in the ground water
beneath the site indicates that they may not be attributable to
historic soils contamination at the facility.
The confining layer at the base of the shallow aquifer
appears to restrict movement of contaminants into the deep
bedrock aquifer. The shallow ground water beneath the floodplain
at the site discharges to the Spring River along and downstream
of the Syntex facility, thus the river defines the westernmost
aerial extent of ground water contaminants in the shallow aquifer
below the floodplain. Due to the general ground water flow
direction, the river would also be expected to intercept any
contaminated ground water leaving the site within a short
distance of the northern property boundary. Further, due
primarily to biodegradation and volatilization, some of the
historically detected organic contaminants may be permanently
removed from the ground water system before the ground water
discharges to the Spring River.
Because dioxin has the tendency to bioaccumulate in fish,
SYntex has sampled fish and sediment annually for dioxin from
locations in the Spring River downgradient of the site.
Analysis of fish filets indicated a maximum level of 40 parts per
trillion (ppt) dioxin in 1982, and had decreased to a level of
4.8 ppt by 1987. The Food and Drug Administration advisory level
for dioxin in edible portions of fish is 25 ppt for reduced
consumption and curtailment at 50 ppt. Table 5 illustrates the
decline of dioxin levels in fish between 1988 and 1992, after the
implementation of au 1.
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. I 19921
Site 1988 1989 1990
1 3.0/3.2 4.7/3.3 1.8/2.1 (1.6)2/2.2
2 4.2/5.9 3.5/4.1 1.9/2.0 1.0/1.9
Note: The two values presented for each site
and year represent an independent analysis of
duplicate composite samples
Table 5.
Dioxin Concentrations (ppt) in Fish Filets From
the Spring River, Missouri
SUMMARY OF SITE RISKS
As part of the remedial investigation activities, an
analysis was conducted to estimate the human health or
environmental problems which could result from exposure to ground
water at the site. This analysis is commonly known as a baseline
risk assessment. The purpose of the baseline risk assessment is
to provide a public health evaluation of potential ground water
contamination remaining following the cleanup of contaminated
soils onsite. The risk assessment was prepared using data
acquired during the remedial investigation for the past two years
and using assumptions regarding maximum exposures that could be
reasonably expected for an individual at or near the site. This
scenario is defined as the Reasonable Maximum Exposure (RME)
scenario. The Baseline Risk Assessment conducted for OU 2 is
included in the Administrative Record.
For the purposes of this risk assessment, EPA considered the
RME scenario to be a family living immediately downgradient of
the site and relying on a water well completed within the shallow
alluvial aquifer as a sole source of water for drinking and other
purposes. Such persons would be exposed to the ground water by
ingestion of drinking water, and through dermal exposure and
inhalation while showering. The additive carcinogenic risk for
this scenario based upon exposure to ground water located
immediately downgradient of the site would result in less than 5
excess cancers per 100,000 people exposed for an adult over 30
years of chronic exposure, and less than 3 excess cancers per
100,000 for children living adjacent to the site. The additive
non-carcinogenic risk is 0.844 for an adult over.30 years of
exposure and 0.372 for a child. When evaluating risk resulting
from exposure to hazardous substances for people at or near a
Superfund site, EPA considers the exposure to be unacceptable if
it results in a carcinogenic risk greater than one additional
cancer per 10,000 people exposed or a non-carcinogenic hazard
index greater than 1. Thus, EPA believes that the risk posed to
the individuals in this scenario falls within an acceptable risk
range at this time.
14
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Significant uncertainties exist with this RME scenario which
may result in an overestimation of the risk. These uncertainties
include the assumptions that a residence would be established
immediately adjacent to the area of ground water contamination
and that a municipal water supply would be unavailable. Land use
restrictions have been established for the site that will limit
the property to industrial use and ensure residential exposure
does not occur. Additionally, the level of contaminants used in
this assessment was developed by combining contaminants detected
across several wells in the monitoring well network and
projecting those concentrations to the RME well. Lesser
concentrations of each contaminant could reasonably be expected
at a point down-gradient from the source of contamination.
In an attempt to better define potential downgradient
receptors, EPA identified and sampled three residential wells
within approximately one mile downstream of the site. Analysis
of these samples found no contamination in these downgradient
residential wells. Thus, under current site conditions it does
not appear that any contaminants have migrated to any potential
downgradient receptors.
SUMMARY OF ALTERNATIVES
The primary purpose of a Feasibility study (FS) is to ensure
that appropriate remedial alternatives are developed and
evaluated for consideration in selecting a remedial action. The
FS for OU 2 identified the following alternatives for this site:
1.) No action; 2.) No action with continued ground water
monitoring; 3.) Ground water pumping and treatment.
Alternative 1: No Action
The no action alternative provides a baseline for comparing
other alternatives. Because no remedial action would be
implemented, long-term human health and environmental risks for
the site essentially would remain the same as those identified in
the baseline risk assessment.
Alternative 2: No Action With continued Ground Water Monitoring
Alternative 2 entails no further action with continued
monitoring of the of the monitoring well network and installation
of additional monitoring well clusters. As with Alternative 1,
potential long-term human health and environmental risks for the
site essentially would remain the same as those identified in the
baseline risk assessment. In this alternative, monitoring would
be done for a dozen additional compounds (Table 2) on a quarterly
basis for the flood plain monitoring wells. However, after the
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first year, all parameters whose levels have remained constant
would be monitored semi-annually. Surface water sampling of
Spring River upstream and downstream of the facility and the
formerly contaminated areas would be conducted in coordination
with the ground water monitoring program. A risk assessment
would be conducted at the end of the two-year monitoring program
to ensure that the "no action" approach remains protective of
human health and the environment.
TABLE 6.
10.
11.
12.
Additional Compounds to ~e Analyzed for Alternative t2
1.
Dioxin (2,3,7,8 Tetrachlorodibenzo-p)
2.
Heptachlor
Heptachlor Epoxide
3.
4.
1,4 Dichlorobenzene
5.
Bis (2-Ethylhexyl) phthlate
6.
Antimony
7.
Tetrachlorobenzene (1,2,4,5)
Triclorobenzene (1,2,4)
8.
9.
1,3 Dichlorobenzene
Naphthalene
Hexachlorophene
1,4 Dioxane
Additional monitoring wells would be installed both
upgradient and downgradient from the facility. One upgradient
monitoring well would be installed to ensure background
conditions are fully characterized upgradient (south) from the
facility and formerly contaminated areas. The purpose of
installing the downgradient monitoring wells would be to confirm
the leading edge of any potentially migrating plume downgradient
(north) of the facility and formerly contaminated areas.
This alternative is readily implementable. Sufficient labor
and analytical services exist to meet the requirements of the
alternative. There would be no additional risks posed to the
community, workers, or the environment as the result of this
alternative being implemented. The two-year present worth cost
of this alternative is estimated to be $120,000, with a projected
$50,000 for capital expenditures.
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Alternative 3: Ground Water Pump and Treatment
This alternative involves pumping groundwater from
extraction wells and treating the water using chemical
precipitation to remove the inorganic fraction of the groundwater
and air stripping to remove the organic fraction. Precipitation
is a process by which the chemical equilibrium of the water is
altered to reduce the solubility of metals. The metals
precipitate out as a solid and are removed from the ground water
by solids removal processes such as clarification and filtration.
The resulting sludge would be transported to an off-site disposal
facility. After the metals are removed, the ground water would
be routed to an air stripper to remove any organic contaminants
that may be present.
This alternative would reduce the toxicity, mobility, and
volume of contaminants which might be present in the water.
However, due to the inconsistent contaminant levels detected at
each well within the target volume, the need for a pump and treat
system has not been established at this time. This alternative
is readily implementable should contaminants be discovered at
levels which pose an unacceptable risk. The present worth cost
for of this alternative is estimated to be $3,500,000 with a
projected $1,100,000 for capital expenditures.
DESCRIPTION OF THE SELECTED ALTERNATIVE
Based on current information, Alternative ~2 -- No Action
with Continued Ground Water Monitoring is EPA's preferred
alternative. EPA believes that no significant health threat
currently exists as a result of the residual ground water
contamination attributable to historic waste disposal practices
at the facility. Therefore, no remedial action is warranted for
the ground water at this time. This alternative includes a two-
year program to monitor ground water quality at the site. A
ground water assessment will be conducted at the end of the
monitoring program to ensure that ground water contamination does
not pose an unacceptable risk to human health or the environment.
Where a site poses an unacceptable risk to human health or
the environment, Section 121 of CERCLA, as amended by SARA,
requires EPA to evaluate selected remedial alternatives against
nine criteria. The first step is to ensure that the alternative
satisfies the threshold criteria. The two threshold criteria are
overall protection of public health and the environment and
compliance with applicable or relevant and appropriate
requirements (ARARs). Alternatives that do not satisfy these
criteria are rejected and not evaluated further. The second step
is to compare the alternative against a set of balancing
. criteria. The NCP established five palancinq criteria which
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include long-term effectiveness and permanence: reduction in
toxicity, mobility, or volume achieved through treatment:
implementability: short-term effectiveness: and cost. The third
and final step is to evaluate the alternative on the basis of
modifying criteria. The two modifying criteria are state and
community acceptance.
However, in some situations, such as the case for OU 2, the
Baseline Risk Assessment conducted during the RI demonstrates
that conditions at the site pose little current or potential
threat to human health or the environment. Under such
circumstances, the statutory standards of CERCLA Section 121
(e.g., compliance with ARARs, cost effectiveness) are not
triggered and these requirements need not be addressed in
documenting that a "no action" decision is appropriate for a site
or operable unit.
The 1988 remedial action greatly removed dioxin and
associated volatile organic compound (VOC) soil contamination at
this site. Reported concentrations of contaminants are currently
present at low levels and represent little risk to human health
and the environment. Based upon trends observed from historical
data, the low levels of contaminants present should continue to
attenuate over time.
As part of a separate National Pollutant Discharge
Elimination System (NPDES) permit requirement, three additional
monitoring wells are planned to be installed directly
downgradient from the spray irrigation system located on the
south end of the facility property. These three monitoring wells.
will be completed in the shallow alluvium to characterize any
possible ground water contamination which may be attributable to
the current land application of treated waste water at the
facility.
The selected remedy presented in this record of decision
represents the final remedy selection at this site. The five-
year review will include an assessment of the additional ground
water monitoring information collected subsequent to the issuance
of this decision document. This review will be conducted in
accordance with CERCLA, and applicable guidance and in a manner
that will assure the continued protection of public health and
the environment. A five-year review is required for all sites
where hazardous substances, pollutants, or contaminants remain
above levels that allow for unlimited use and unlimited exposure.
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