EPA Superfund
Record of Decision:
PB97-964605
EPA/541/R-97/049
November 1997
Monsato Chemical Co.
(Soda Springs)
Soda Springs, ID
4/30/1997
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RECORD OF DECISION
MONSANTO CHEMICAL COMPANY
Superfund Site
Caribou County, Idaho
April 1997
US ENVIRONMENTAL PROTECTION AGENCY
Region 10
Office of Environmental Cleanup
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Monsanto Record of Decision
Table of Contents
DECLARATION
II. DECISION SUMMARY 3
1. SITE LOCATION AND DESCRIPTION 3
2. SITE HISTORY AND ENFORCEMENT ACTION 7
3. HIGHLIGHTS OF COMMUNITY PARTICIPATION 12
4. SCOPE AND ROLE OF RESPONSE ACTION
WITHIN SITE STRATEGY 13
5. SUMMARY OF SITE CHARACTERISTICS 14
6. SUMMARY OF SITE RISKS 25
- NEED FOR ACTION 33
7. DESCRIPTION OF ALTERNATIVES 37
8. SUMMARY OF COMPARATIVE ANALYSIS
OF ALTERNATIVES 44
9. SELECTED REMEDY AND RATIONALE 49
10. STATUTORY DETERMINATIONS 55
11. DOCUMENTATION OF SIGNIFICANT CHANGES 57
III. RESPONSIVENESS SUMMARY
Appendix A - Additional Figures and Tables
Appendix B - Administrative Record Index
Figures
1) Monsanto Site Location Map 4
2) Plant Layout 8
3) Conceptual Model of Constituent Transport 16
4) Concentrations of Contaminants of Concern in Soils-Phase 1 19
5) Concentrations of Contaminants of Concern in Soils-Phase 2 20
6) Areas Where Groundwater Exceeds MCLs 22
7) Areas that Exceed Soil Remediation Goals 54
A-4) Location of Samples Used in Current Residential Scenarios
A-5) Location of Samples Used in Future Residential Scenarios
Tables
1) Exposure Assumptions for Industrial Scenario 28
2) Incremental Risk Over Background - Industrial Scenarios 29
3) Incremental Risk Over Background - Residential Scenarios 29
4) Summary of RME Risks in Excess of Background Risks 30
5) Summary of Alternatives Considered and ARARs 43
A-1) Identification of Chemicals of Potential Concern in Groundwater
A-2) Identification of Chemicals of Potential Concern in Soils
A-3) Identification of Chemicals of Potential Concern in Source Piles
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Declaration of the
RECORD OF DECISION
for the
Monsanto Chemical Company Superfund Site
Caribou County, Idaho
Statement of Basis and Purpose
This decision document presents the selected remedy for the Monsanto Chemical
Company Site (the Site) in Caribou County near Soda Springs, Idaho, which was
chosen in accordance with the Comprehensive Environmental Response,
Compensation and Liability Act (CERCLA), as amended, and, to the extent practicable,
the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). This
decision is based on the administrative record for the Site.
A letter indicating that the State of Idaho concurs with the selected remedy is attached.
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
This is intended to be the final remedy for this Site. Previous actions have already
addressed the principal sources of contaminant releases at the Site. The selected
remedy described in this document addresses the remaining threats posed by the Site.
The major components of the selected remedy by media are:
o GROUNDWATER: The selected remedy for groundwater is monitored natural
attenuation with institutional controls to prevent use of contaminated
groundwater for drinking purposes, until such time as cadmium, fluoride,
selenium, nitrate and manganese concentrations in groundwater decline to
below the primary Maximum Contaminant Levels (MCLs) or risk-based
concentrations for those substances.
o SOILS: For contaminated soils outside the Monsanto Plant boundary line (the
Plant), the selected remedy is an election by affected property owners for either:
a) institutional controls, or b) excavation of contaminated soils, replacement with
clean soil, and disposal of the contaminated soils within the Plant.
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o SOURCE PILES, AIR, SURFACE WATER AND SEDIMENTS: No further action
is necessary under CERCLA for source piles and materials within the Plant, nor
for air, surface water, or Soda Creek sediments.
Except as expressly stated in CERCLA, the NCP, or this ROD, the ROD is not designed
to address Monsanto's ongoing operations, or to preclude, or in any way affect, the
need for the Plant's ongoing operations to comply with other environmental laws or
regulations.
While not part of the selected remedy, the selected remedy assumes continued
operation of the Plant by Monsanto in compliance with all Federal and State
environmental requirements as well as the applicable closure requirements in the event
that the Plant ceases operation. If air emissions exceed permitted levels, they could
pose additional risks to human health or the environment or allow unacceptable levels of
contaminants to migrate to surrounding soils at or near the Site which could require
additional CERCLA action. The effect of ongoing and future air releases on surrounding
soils, human health and the environment will be evaluated during five-year reviews.
Remedial alternatives were not developed for alternative future industrial or residential
scenarios within the Plant and no remedy has been selected based on such scenarios
because Monsanto is considered highly likely to continue to operate the Plant for the
foreseeable future. Monsanto has just increased production and maintains it has the
reserves to profitably operate the Plant for over 30 more years.
Statutory Determinations
The selected remedy is protective of human health and the environment, complies with
Federal and State requirements that are legally applicable or relevant and appropriate to
the remedial action, and is cost-effective. The remedy utilizes permanent solutions and
alternative treatment (or resource recovery) technologies to the maximum extent
practicable for this Site. However, because the sources of contaminant releases have
been controlled and treatment of the remaining threats at the Site was not found to be
practicable, the selected remedy does not satisfy the statutory preference for treatment
as a principal element.
Because this remedy will result in hazardous substances remaining on Site above
health-based levels, a review will be conducted within five years after commencement of
remedial action to ensure that the remedy continues to provide adequate protection of
human health and the environment.
fhuck Clarke
Regional Administrator
U.S. EPA Region 10
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RECEIVED
IDAHO DEPARTMENT
OF HEALTH AND WELFARE _ __
DIVISION OF MAY 05 199»
ENVIRONMENTAL QUALITY , r. nff.
Environmental Cleanup Uifiee
1410 North Hilton. Base. ID 83706-1255. (208) 373-0502 phi,ip E Batt
April 29, 1997
TimBrincefield-HW-113
US EPA Region 10
1200 Sixth Ave.
Seattle, WA. 98101
Subject: State of Idaho Concurrence on the Monsanto, Soda Springs, Record of
Decision (ROD).
Dear Mr. Brincefield:
Thank you for providing the State of Idaho an opportunity to review and comment on the
Monsanto, Soda Springs, Idaho Superfund Record of Decision. Staff from Idaho Division
of Environmental Quality, Pocatello Regional Field Office, Central Office and the Attorney
General's Office, have reviewed and provided comments on the document. Those
comments have been addressed in the final ROD. We also believe EPA has appropriately
addressed comments provided by the community and other affected parties.
Your consideration of our input in selecting the remedy for this site is appreciated. We
concur with the remedy selected by EPA in the April 1997 Record of Decision for the
Monsanto Chemical Company Superfund Site.
Sincerely,
Wallace N. Cory, P.I
Idaho Division of EnvlcQrimental Quality
Administrator
WNC:mp
cc: Mark Lowe, Pocatello Field Office Administrator
Dean Nygard, Remediation Bureau Chief
Rob Hanson, Superfund Program Manager
Steve Goddard, A.G.'s Office
Curt Fransen, A.G.'s Office
Gordon Brown, Pocatello Field Office Remediation Project Officer
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DECISION SUMMARY
Monsanto Chemical Company Superfund Site
Caribou County, Idaho
1. SITE LOCATION AND DESCRIPTION
The Monsanto Chemical Company Superfund Site is located in Caribou County, Idaho,
approximately one mile north of the City of Soda Springs (see Figure 1). CERCLA regulations
define the term "site" as "the area! extent of contamination and all suitable areas in very close
proximity to the contamination necessary for implementation of the response action." The
Monsanto Site (the Site) includes an active elemental phosphorus plant operated by the
Monsanto Company (the Plant) and those portions of the surrounding property which have
been contaminated by Plant operations or are necessary for the conduct of the selected
remedy. The term "Plant" is used in this ROD to refer to those portions of the Site which are
owned by Monsanto and used for their elemental phosphorus manufacturing operations.
The Plant occupies approximately 540 acres in a tributary valley to the Bear River; the entire
Site, including the Plant, includes about 800 acres. Land use in the vicinity of the Plant is a
primarily agricultural and industrial. The closest surface water body is Soda Creek, located
approximately 2.000 feet west of the Plant.
Population density in the area is sparse. Within 1 mile of the Site there are about 30 residents,
and within 2 miles there are about 1,400 residents. About 3,000 residents, which includes the
most of the population of the City of Soda Springs (the City), live within 3 miles of the Site.
Most of the community residents' water is supplied from the City. This water is obtained from
Formation Springs located to the northeast of the City and the Plant, and from Ledge Creek
Springs to the southeast. Both City springs are in different hydrogeological systems from, and
are therefore unaffected by, the Site. Twenty-two domestic water supply wells are registered
within 3 miles of the Site (most of them upgradient), as well as seven irrigation wells. Hooper
Springs, located downgradient but showing no evidence of contamination, is occasionally used
by tourists and residents for drinking. The only domestic well known to have been affected by
groundwater contamination is at a home located 0.2 miles south of the Plant. This home was
connected to City water by Monsanto after selenium contamination was found in the well.
A number of other industrial sites are located in the valley. These include:
• Kerr-McGee Chemical Corporation (production of vanadium compounds), across
Highway 34 from the Monsanto Plant;
City Industrial Park (various), adjacent to the Monsanto Plant to the Southeast;
Evergreen Resources (fertilizer products) and Soda Springs Phosphate
Industries (fertilizer products) 1,000 to 2,000 feet southeast of the Plant; and
Nu-West Industries (phosphoric acid production and fertilizer products), four
miles north of the Monsanto Plant (not shown on Figure 1).
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Climate
The climate around Soda Springs is semi-arid, with hot summers and cold winters,
characterized by relatively low precipitation (Rl report cites averages of 16 and 19 inches per
year), and high evapotranspiration (averages range from 1 to 8 inches per month).
Surface Hydrology
The major river in the vicinity of the Monsanto Plant is the Bear River, located approximately
two miles to the south and southwest of the Monsanto Plant. Regional manmade surface
waters include Alexander Reservoir and Blackfoot Reservoir. Natural local surface-water
features in the Monsanto Plant vicinity include Soda Creek, Ledger Creek, Big Spring Creek,
two wetland areas, and numerous springs and spring-fed ponds. Local manmade surface-water
features include the ponds within the Monsanto and Kerr-McGee Plants and Soda Creek
Reservoir to the west.
Soda Creek, which is a tributary of the Bear River, forms the main surface water drainage for
the Plant and the surrounding area. Soda Creek originates at Fivemile Meadows and flows
south (about 2,000 feet west of the Plant) to its discharge into Alexander Reservoir. Soda
Creek is used for power generation and irrigation. There are three powerhouses located above
Alexander Reservoir. Under a National Pollutant Discharge Elimination System (NPDES)
Permit (which requires measurement of pH and temperature), Monsanto discharges non-
contact cooling water into Soda Creek via an underground pipeline. An irrigation diversion dam
is located just downstream of the Monsanto effluent outfall, and flow is diverted from the creek
for parts of the year.
Geology
The geology (and resultant hydrogeology) in the vicinity of the Site is quite complex.
Regionally, the Plant is located near the southern end of the Blackfoot Lava Field that has filled
a valley bordered by the Chesterfield Range and the Soda Hills on the west, and by the Aspen
Range on the east. Locally, the Plant is underlain by a thin veneer of soils that overlie basalt
flows of the Blackfoot Lava Field. Five basalt flows, separated by sedimentary interbeds or
weathered basalt zones, are present beneath the Plant. The basalt flows vary in thickness from
less than 10 feet to 80 feet. The sedimentary units and weathered basalt zones range from 1 to
23 feet thick. The basalt flows overlie the Salt Lake Formation.
Fault displacement has apparently interrupted lateral groundwater flow and created springs in
the vicinity of the Plant. A series of north-northwest trending faults, typically 1,000 to 1,500
feet wide and up to 2.5 to 3 miles long, extend from the southeast of the Plant north to the
Blackfoot Reservoir. A prominent fault enters the Plant near the northwest corner and appears
to die out just west of the southeast comer of the Plant. A subsidiary fault parallels this fault
approximately 1,500 feet to the southwest.
Several normal faults exist east of the Plant that appear to act as a hydraulic barrier, such that
groundwater west of the Finch Spring fault apparently does not flow into the Ledger Creek
Springs area.
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Soils
The soils around the Plant are largely classified as clayey silt with some sand and a trace of
gravel. Soil depth in the area typically ranges from 3 to 23 feet. There was no appreciable
difference between samples collected from the 0-to-l-inch depth interval and those collected
from the O-to-6-inch depth interval. Soils within the Plant are covered by facilities and materials
and cannot be correlated with the surrounding soils.
Hydrogeology
There are three dominant groundwater systems in the region of the Monsanto Plant:
The Mead Thrust Aquifer System receives recharge by precipitation over the
mountains to the east of the Plant. The direction of groundwater movement in this
system is westward. Groundwater discharge occurs through several springs along
faults at the eastern margin of the Blackfoot Lava Field, including Formation Spring.
The Chesterfield Range Aquifer System receives recharge from the Chesterfield
Range to the west of the Plant. Groundwater from this system discharges along the
western margin of the Blackfoot Lava Field via deep, normal faults.
The Shallow Groundwater System consists of water that comes into contact with the
upper basalts of the Blackfoot Lava Field. The direction of groundwater movement in
this system is typically to the southwest but can be affected by faults and pumping of
production wells (for process water)at both Monsanto and Kerr-McGee. Groundwater
discharges from this system into Soda Creek, Alexander Reservoir, and the Bear River.
Groundwater from these systems flows through four local hydrogeologic zones located beneath
the Plant, described in greater detail in the Rl. The Surficial Deposit Zone (SDZ) is only present
in the northeast portion of the Plant at a thickness of about 10 to 40 feet. The Salt Lake Zone
(SLZ) is located in the north central and northeast portions of the Plant, and may also be
present beneath the Lower Basalt Zone. The Upper Basalt Zone (UBZ) is an aquifer underlying
the Plant at depths ranging from about 20 feet below ground surface (bgs) in the northeast
comer of the Plant, to about 100 feet bgs in the center of the Plant. The Lower Basalt Zone
(LBZ) underlies the UBZ and the Plant at depths of at least 250 feet bgs. Groundwater flow in
the UBZ and the LBZ is influenced by faulting and by pumping of the Plant production wells.
The estimated hydraulic conductivity for the basalts below the Plant ranges from 0.04 to 676
ft/d. Hydraulic conductivity values appear to decrease with depth, and vary between interflow
zones. Several multiple well aquifer tests were conducted to characterize the aquifers below
the Plant. On of the key findings of those tests was that the Monsanto and Subsidiary Faults
serve as barriers to groundwater flow for their length beneath the Plant, thus preventing
hydraulic communication between some of the different groundwater regions.
Groundwater in the vicinity of the Plant can be characterized as either fresh or sodic, with sodic
water defined by a bicarbonate alkalinity exceeding 700 mg/L. Fresh water occurs
predominantly in the UBZ in the Plant vicinity. Sodic water occurs in the LBZ on the west side
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of the Plant, and fresh water occurs in the LBZ on the east.
2. SITE HISTORY AND ENFORCEMENT ACTION
The Monsanto Soda Springs Plant processes locally mined phosphate ore to produce elemental
phosphorus. In 1952, Monsanto purchased the Plant site, built the Plant, and started
operations. The fenced Plant consists of more than a dozen administrative and processing
buildings plus ore piles, slag piles, by-product materials, surface impoundments, and a solid-
waste landfill.
The Plant is currently staffed with about 400 employees. Two of three on-site production wells
previously provided potable water for employee consumption. In December, 1989, a new well,
upgradient from all Plant operations was installed to provide potable water for employee use
separate from process water.
Approximately 1 million tons of phosphate ore are processed through the Plant each year. The
ore is first "nodulized" in a rotary oxidation kiln where organic contaminants are released and
burned. Some fluorides (about 0.7 pounds per hour) are released from the process stacks in
accordance with the Clean Air Act permit for this process. Carbon monoxide generated in the
final electric arc furnaces is recycled as a supplemental fuel to provide heat for the nodulizing
process.
Nodulized ore to be reduced to elemental phosphorus is fed with coke and silica into three
electric arc furnaces. The process gases contain phosphorus, silicon tetrafluoride, and carbon
monoxide. The phosphorus is condensed out for recovery, and the particulates are removed by
electrostatic precipitators. The carbon monoxide is cycled back to the nodulizer as a fuel, and
the particulate from the nodulizer operation is removed by high energy venturi scrubbers.
Molten slag from the process is periodically tapped from the furnace. The heavy fraction of the
slag consisting primarily of metals (iron, vanadium, and others) is tapped separately and sold as
a material for extraction of the vanadium.
9'
"Underflow solids" (UFS) are fine grained particulate matter removed from rotary-kiln exhaust
gas in a wet slurry, which is settled and dewatered in the hydroclarifier. The resulting coarse-
to-fine solids are stockpiled in the northeast comer of the plant and recycled slowly in the
process due to its low-grade phosphate ore value.
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Monsanto Site
PLANT LAYOUT
Figure 2
MONTGOMERY WATSON
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Previous Studies
Monsanto initiated a number of environmental studies to characterize potential impacts from its
operations. In 1980, the slag was analyzed for Extraction Procedure toxicity parameters
established by the Environmental Protection Agency (EPA) and found not to exceed any of the
standards. In 1984, Colder Associates was commissioned to evaluate groundwater and
surface water impacts resulting from current and past activity. Thirty-one new monitoring wells
were installed to supplement seven existing wells (additional wells have been added
subsequently). This investigation showed groundwater under the Site to be contaminated with
fluoride, cadmium, selenium, vanadium, and other inorganic species of less concern. The
sources of the contamination were hypothesized to be the underflow solids pond, the northwest
pond, and the hydroclarifier. The underflow solids pond and northwest pond were subsequently
taken out of service (see below). The hydroclarifier has been rebuilt to allow complete
inspection for leakage, none of which has been found.
A separate plume showing contamination with chloride, sulfate, and vanadium exists in the
southeast portion of the Site. This plume originates east of the Monsanto Site.
Listing on the National Priorities List
In 1987, Ecology and Environment, Inc. (E.& E.), an EPA contractor, performed further
sampling as part of a site inspection. Contamination was found in monitoring and production
wells. One of the contaminated production wells was being used for drinking water by Plant
employees at the time. Subsequent to that inspection, the Site was evaluated for inclusion on
the National Priorities List (NPL) of Superfund sites requiring investigation and, if necessary,
cleanup of uncontrolled releases of hazardous substances to the environment.
EPA proposed the Monsanto Site to the NPL in May, 1989; the Site was made final on the NPL
on August 30, 1990 (55 Fed. Reg. 35502). EPA took this action pursuant to its authority under
Section 105 of the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA). EPA and Monsanto negotiated an Administrative Order on Consent (AOC),
pursuant to which Monsanto agreed to perform a Remedial Investigation/Feasibility Study
(RI/FS) for the Soda Springs Site. The AOC was issued by EPA on March 19,1991.
Remedial Measures to Date
Since 1983, investigations and actions by Monsanto in conjunction with EPA's activities
pursuant to CERCLA have resulted in significant environmental improvements and reduced
emissions at the Plant. Some of these improvements were made independently by Monsanto,
and others were done to comply with state and/or federal requirements. These actions have
addressed many of the known and suspected sources of contamination investigated during the
RI/FS. The measures included the following:
• In August, 1985 the hydroclarifier, which was suspected as potentially affecting
groundwater, was replaced with a unit that includes a synthetic liner, a leachate
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collection system, and a monitoring well network.
In 1986, an old coke and quartzite dryer and wet scrubber was replaced with a more
efficient dryer and dust collector, resulting in air emission reductions of over 95 percent.
In 1986, four underground fuel storage tanks were replaced with aboveground tanks
with concrete sumps. These underground tanks were removed to comply with new
regulations. There was no indication that leaking had occurred.
In September, 1987, four parallel high energy venturi scrubbers, separators, fans, and
stacks were installed to provide additional scrubbing of kiln exhaust. The parallel
arrangement of equipment effectively reduces upset/breakdown emissions that would
occur if only one or two fans existed. This project resulted in a reduction of particulate
emissions of about 95 percent and contributes to a cumulative cleaning efficiency of
99.9 percent.
In 1987, four wells (TW-3, TW-4, TW-5, and TW-6), which were discovered to be
creating hydraulic communication between upper and lower aquifers due to poor
construction, were abandoned in accordance with regulatory guidelines.
In 1983, the old underflow solids ponds, suspected as sources of groundwater
contamination, were taken out of service. Much of the solids were subsequently
excavated and recycled. In 1988, the upper layer of contaminated soil was removed,
and the depression was backfilled with material excavated from the northwest pond (see
below) and clean material. The ponds were then filled with molten slag and sealed with
a bentonite cap to isolate the remaining underflow solids from infiltration and prevent
further migration of contaminants. Solids that remained in the pond are below the cap,
but above the water table.
In 1988, the northwest pond, also a suspected groundwater contamination source, was
closed and excavated. Discolored soils were removed and deposited in the old
underflow solids ponds. The base of the pond was sealed with bentonite. The area is
currently permitted by the Idaho Department of Environmental Quality to receive Plant
sanitary solid waste and is being operated as a lined general waste landfill.
In 1988, a new Plant drinking water well (PW-4) was installed upgradient of known and
suspected source areas to prevent degradation of the potable water supply. A new
independent potable water distribution system was installed with the new well, thus
preventing cross-connection of potable and raw process water at the Plant.
Between 1985 and 1989, several wells were installed around the hydroclarifier and used
as recovery wells to intercept contaminated groundwater. The groundwater was
pumped into the new hydroclarifier. Three wells were pumped intermittently at a rate of
approximately 12 gallons per minute (gpm) per well from 1985 to 1989. The Plant
stopped pumping these wells in the spring of 1989 based on potential listing of the Plant
for the NPL and has not resumed since then.
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Since 1990, fugitive emissions from the baghouse dust disposal pile have been reduced
through improved handling procedures and placing crushed slag on the surface of
unused portions of the pile. Additional projects have significantly reduced fugitive air
emissions from the conveyance of slag from the furnace.
During 1992, emission controls were implemented in the nodule reclaim area. These
controls included a stationary stacking tube and dust collectors at material transfer
points to reduce fugitive dust emissions.
In 1993, Plant sewage evaporation ponds were taken out of service and the Plant was
connected to the City wastewater collection system. The ponds were closed in 1995.
In 1995, pilot-scale demonstration projects were initiated to evaluate the effectiveness of
several types of dust suppressants for on-Plant stockpiles. The most successful was
application of a concrete/synthetc slurry mixture, which dries to a crusty surface,
effectively preventing fugitive emissions from piles on which it is applied. As of this time
(Spring 1997), Monsanto reports that the Plant has continued to use this method to
control emissions from piles which are not being actively used. Piles which are still
being used are not currently covered, although efforts are made to minimize fugitives.
Monsanto maintains that it is taking all feasible measues to minimize fugitive emissions
from the Plant.
Regulatory Status
A review of the Plant's regulatory status as of August, 1996, shows that the Plant is in
compliance with the Resource Conservation and Recovery Act (RCRA), the Clean Air Act
(CAA), the Toxic Substances Control Act (TSCA), and the National Pollutant Discharge
Elimination System (NPDES). In addition, the Monsanto Plant has received awards from the
Occupational Safety and Health Administration (OSHA) because of its implementation of worker
safety programs, compliance with OSHA regulations, and worker safety record.
Monsanto has complied with the requirements of the RI/FS AOC.
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3. HIGHLIGHTS OF COMMUNITY PARTICIPATION
At the Monsanto Site, EPA has met all requirements of CERCLA Section 117 and the NCP for
public participation at NPL sites. Nomination of the Site to the NPL followed extended public
comment. Subsequent to listing the Site on the NPL, EPA conducted community interviews to
identify community concerns and developed a Community Relations Plan to guide future
public involvement in the RI/FS. The Site Community Relations Plan was published in 1990,
and will be updated after ROD signature and before the start of remedial design.
An Information Repository was established and has been maintained at the Soda Springs
Public Library. An Administrative Record and Site File, which are available for review at the
Information Repository in Soda Springs and the EPA Regional Office in Seattle, were
established and have been maintained since the beginning of this project.
Numerous fact sheets were produced during the RI/FS to keep members of the community
informed and to solicit their input on the project. The following are the dates for the more
significant fact sheets and the topics they addressed:
Dec. 1991 Introduction to the Superfund Process;
May 8,1992 Monsanto to Conduct Additional Testing This Spring and Summer;
Mar 15, 1994 Investigation Nearly Complete; Risk assessment being prepared;
July 27, 1994 Congressional Update - Superfund Studies Underway;
June 29,1994 Postcard/advertisement for July 13,1994, Open House describing the
progress of the Remedial Investigation;
Oct. 3, 1994 EPA Responds to Community Questions; Risk Assessment Report
Delayed for More Work;
Jan 27,1995 Risk Assessment Results;
June 2, 1995 Objectives for Clean Up/ Recap of Remedial Investigation and Risk
Assessment Work;
July 29, 1996 Proposed Plan and Invitation to comment on the Plan.
In addition, several public meetings were held to inform community members and solicit their
input on the project. EPA, with help from the Idaho Division of Environmental Quality (DEQ) of
the Idaho Department of Health and Welfare (IDHW), planned and publicized these meetings.
Monsanto also participated by presenting the results of their studies and answering questions.
One such meeting was held on July 13, 1994, at which the results of the Rl and
the plans for upcoming risk assessment and FS work were presented.
Another such meeting was held June 20, 1995, at which the results of the risk
assessment and preliminary FS efforts were presented.
Approximately 25-30 people (including Monsanto Chemical Company and government
representatives) attended each meeting. Before each meeting the Agencies discussed the
meeting agendas with the Mayor of Soda Springs and Monsanto representatives, and after
each meeting the Agencies reviewed the results of the meetings with the Mayor to ensure that
community concerns were clearly understood.
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In accordance with CERCLA requirements, once the RI/FS was complete EPA issued a
Proposed Plan for a 30-day public comment period. The Proposed Plan (Plan) provided
information on the alternatives considered and identified the preferred remedial alternative. The
start of the comment period was announced in a Public Notice placed in the Caribou County
Sun, in a fact sheet, and in the Plan, which was sent to the entire mailing list maintained by
EPA for the Site on July 29,1996. Both the Caribou County Sun and the Idaho Statesman
published articles describing the Plan and announcing the public comment period. Owners of
property adjacent to the Monsanto Plant were sent the Plan with a cover letter which pointed
out that they or their property could be affected by the Plan, and were urged to review the Plan
and to provide comments.
On August 13, 1996, EPA held a Public Meeting to describe the Plan and take formal public
comments. The meeting was transcribed by a court reporter and all comments received are
addressed in the Responsiveness Summary portion of this ROD.
On August 21, 1996, EPA received a request for a 30-day extension to the public comment
period from the Mayor of Soda Springs, in order to give the Mayor, local officials and residents
more time to review the Plan and provide comments. In response, EPA extended the comment
period by 30 days, until September 30, 1996. All comments received at the public meeting and
through the mail during the 60-day public comment period were considered in making this
decision and have been summarized and addressed in the Responsiveness Summary.
4. SCOPE AND ROLE OF RESPONSE ACTION WITHIN SITE STRATEGY
The selected remedial actions are intended to be the final remedy for this Site.
The remaining threats to human health and the environment posed by the Site are from
potential human exposure to groundwater contamination and contaminated soils. The
previously uncontrolled sources of contamination and fugitive air emissions which led to listing
have been addressed by various remedial, compliance, and worker health and safety measures
implemented since listing. The selected remedy addresses the residual contamination in soils
surrounding the Plant and the underlying groundwater.
The Monsanto Plant is an operating facility. Except as stated expressly in CERCLA, in the
NCP, or in this ROD, this ROD is not designed the address the Plant's ongoing operations or
preclude or in any way affect the need for Monsanto's ongoing operations to comply with other
environmental laws or regulations. The selected remedy assumes continued operation of the
Plant by Monsanto in compliance with all Federal and State environmental requirements as well
as the applicable closure requirements in the event the Plant ceases operation.
The Plant is subject to National Emission Standards for Hazardous Air Pollutants (NESHAP)
regulation under the Clean Air Act and State Air permits to Construct and Operate pursuant to
IDAPA 16.01.1012 (Rules and Regulations for the Control of Air Pollution in Idaho). Under
these regulations, Monsanto is required to control fugitive dust emissions and is subject to
inspections. Compliance with these requirements provides adequate protection of public health
and the environment. If Monsanto fails to remain in compliance, such failure could lead to
13
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unacceptable risks and the need to re-evaluate the protectiveness of this CERCLA response
action. This ROD requires No Further Action for air and source piles under the assumption that
existing controls, including dust suppression of the underflow solids and treater dust piles will be
maintained, and efforts will be made to eliminate the piles in the future. If during 5-year reviews
concentrations in soils surrounding the Plant are found to increase or dust emissions have
exceeded permitted levels and pose significant risks to public health or the environment,
additional action will be considered.
The Resource Conservation and Recovery Act (RCRA) lists solid wastes that are regulated as
hazardous wastes in 40 C.F.R 261.3. Solid wastes generated from the extraction, beneficiation
and certain processing of ores are excluded from this listing (40 C.F.R 261.4). Monsanto has
evaluated process waste streams and activities throughout the plant for hazardous waste
characterization. Appropriate measures have been taken to comply with RCRA requirements
regarding non-exempt waste streams that were characterized as hazardous. A RCRA permit
for the Plant is not required based on current law. The Plant operates as a small quantity
generator of hazardous wastes (40 C.F.R 262.34) for generation of items such as spent safety-
clean solvents, fluorescent light bulbs, aerosol cans, and nicad batteries.
Former off-Site uses of slag were not evaluated in this RI/FS. Such uses and associated
potential risks are being addressed under Administrative Orders on Consent issued by EPA,
most recently in 1996, pursuant to Section 7003 of RCRA, to Monsanto and the FMC
Corporation (a producer of similar slag).
Remedial alternatives were not developed for alternative future industrial scenarios within the
Plant and no remedy has been selected based on such scenarios because the Plant is
expected to operate for the foreseeable future. Monsanto has just increased production and
has indicated it has the reserves to profitably operate the Plant for over 30 more years.
5. SUMMARY OF SITE CHARACTERISTICS
Between March 1991 and November 1995, a Remedial Investigation was performed to
determine the nature and extent of contamination at the Site. Soil, sediment, surface water,
and groundwater samples were collected, and air emissions were evaluated through modeling .
Air, surface water, soils surrounding the Plant, source piles, and groundwater were identified as
media of potential concern at the Site. Details of the investigations and the nature and extent of
contamination present at the Site are provided in the Rl report.
Risk-Based Concentrations (RBCs) were initially developed for screening purposes based on a
conservative target carcinogenic risk of 1E-07, and a target hazard quotient (HQ) of 0.1 for all
media, using toxicity values and EPA default exposure assumptions for a residential scenario.
Similarly, RBCs were developed for on-Plant source materials using industrial scenario default
parameters. RBCs for radionuclides were calculated using the residential and industrial
exposure default parameters from Risk Assessment Guidance, Part B (U.S. EPA 1991), as
modified in August, 1992, by EPA Region 10.
14
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< In summary, after screening using conservative human health and ecological screening values,
the contaminants of potential concern in soils and on-Plant source piles include radionuclides
(radium-226, lead-210, and uranium-238) and chemicals (arsenic, beryllium, selenium and
zinc). The groundwater contaminants of potential concern include those substances detected
at concentrations above primary MCLs, i.e. cadmium, fluoride, nitrate, and selenium, and
manganese, which is present above a secondary MCL. After this initial screening for
preliminary contaminants of concern, the risk assessment (and the rest of this ROD) used
RBCs equivalent to carcinogenic risks of 1x10* and/or a HQ of 1.0 to identify contaminants 6f
concern. More details follow.
Nature and Extent of Constituent Releases
The nature and extent of constituent releases at the Monsanto Plant are summarized below by
the environmental media characterized during Phase I and II Rl field activities. Figure 3 shows
the conceptual Site model developed in the Rl.
Sources of Constituent Release
Numerous media were evaluated in detail with respect to their potential to be sources of
environmental contamination at the Monsanto Plant. Potential sources included:
Ore and coke stockpiles;
Nodule stockpiles;
Baghouse dust;
Calcium silicate slag piles;
Coke and quartzite dust slurry pond;
Nodule fines piles;
Non-contact cooling water effluent;
Treater dust stockpiles;
Underflow solids piles;
Unpaved haul roads; and
Process stacks air emissions.
Fugitive dust emission is the principal mechanism of hazardous constituent release to the
environment surrounding the Monsanto Plant for ore and coke stockpiles, nodule stockpiles,
baghouse dust, the coke and quartzite dust slurry pond, nodule fines piles, treater dust
stockpiles, underflow solids piles, and unpaved haul roads. Gaseous emission is the principal
release mechanism for both the process stacks and during calcium silicate slag pouring. Decay
of naturally-occurring radionuclides in the ore stockpiles, underflow solids piles, and the calcium
silicate slag pile is also a potential release mechanism.
Three primary groundwater contaminant plumes have been defined below the Monsanto Plant.
These plumes occur below the three main sources of groundwater contamination found in the
Rl: the Northwest Pond, the hydroclarifier, and the old underflow solids ponds. The Rl
concluded that Monsanto actions to eliminate these sources of constituent releases to
groundwater and cap them to reduce or eliminate infiltration have been successful in controlling
all known releases and have resulted in measurable, declining concentrations of concern in
15
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Prnaulnt wlndt
7
Extraction ol affected groundwater lor process use. Non-
contact cooling water Is discharged; process water Is
recycled In closed-loop systems and eventually evaporated
Effluent drainage flow to
Soda Creek discharge
Historical sources of Infiltration to
groundwater—mitigated by previous
remedial measures
-------
groundwater. While the sources appear to have been adequately controlled, residual
contaminants bound up in the pore space of the vadose zone and aquifer appear to likely to
continue to release declining levels of contaminants for some period of time. Modeling done to
support the RI/FS predicted that all contaminants should achieve background levels within 5 to
30 years, depending on the contaminant and its rate of retardation in groundwater.
Air Quality
The Monsanto Plant has attained and continues to meet emission requirements for sulphur
dioxide and fluoride, which are monitored by Monsanto and reviewed by the State of Idaho
under the Clean Air Act. Radionuclide emissions from the stacks are regulated under the
NESHAP and are in compliance with those standards, which are based on emissions achieved
by the control technology at this Plant.
A detailed inventory of source emissions was conducted to provide input for the Phase II Rl air
dispersion modeling assessment. Air dispersion modeling for the Phase II Rl was used to
calculate annual average ambient air concentrations and deposition rates for total suspended
particulate matter (TSP), inhalable particulates (PM10), and trace contaminants in TSP,
including these contaminants of potential concern: arsenic, beryllium, cadmium, manganese,
silver, vanadium, zinc, molybdenum, fluoride, lead-210, polonium-210, radium-226, thorium-
230, uranium-234, and uranium-238.
The primary sources of trace constituent emissions were identified from modeling as the kiln
venturi scrubbers, wind erosion of the underflow solids (UFS) stockpile, slag handling
operations, nodule handling operations, taphole fume collectors, nodule crushing and screening
scrubber, and kiln cooler spray tower.
The dispersion modeling analysis indicates that air emissions from the Plant are generally
transported along a North North East-South South West axis in accordance with the prevailing
wind directions.
The primary sources that individually may contribute > 10% to the total annual average
deposition rates of trace contaminants are wind erosion of the UFS stockpile, stack emissions
from the nodule crushing/screening scrubber, wind erosion of the ore stockpile, wind erosion of
the treater dust stockpile, and wind erosion of the slag stockpile.
Surface-Water and Sediment Quality. Soda Creek is the only natural stream which is nearby
and potentially affected by the Site. The upper portions of Soda Creek do not support a
fisheries resource due to naturally-occurring carbon dioxide concentrations in the water. The
lower reach of Soda Creek, just above its confluence with the Alexander Reservoir, provides a
marginal trout fishery for local residents. Fish in the Alexander Reservoir and Bear River
include rainbow and cutthroat trout whitefish, yellow perch, dace, and shiners.
Surface water from Soda Creek and the irrigation canal, sediments in Soda Creek and the
Alexander reservoir, and Monsanto Plant effluent were sampled and analyzed. Statistical
analyses were performed on the water and sediment data to determine which downstream
parameters are elevated with respect to upstream concentrations. Each elevated constituent
17
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was subjected to a preliminary risk-based screening to determine which are considered
contaminants of potential concern.
Surface Water. Except for nitrate, none of the elevated contaminants found in Soda Creek
downstream of the effluent discharge exceeded preliminary human health or ecological risk-
based screening criteria. Nitrate exceeded the risk-based screening value, one-tenth of the
hazard quotient, based on ingestion of surface water by infants. This is considered an unlikely
exposure scenario for Soda Creek due to the high sodic content. In addition, the nitrate
concentration is less than the Maximum Contaminant Level (MCL). Therefore nitrate was
eliminated from further consideration and no contaminants of potential concern were identified
for surface water,
Sediments. Sediments collected from Soda Creek downstream of the effluent outfall in the Rl
were found to contain elevated levels of arsenic, cadmium, copper, nickel, selenium, silver,
vanadium, and polonium-210. As a result, the Ecological risk assessment initially concluded
that action might be warranted, and a decision was made to do an additional sediment
investigation, including toxicity testing. Subsequently, additional samples were collected and
toxicity testing was conducted on sediments collected upstream and downstream of the effluent
outfall using benthic invertebrates. The control samples collected upstream of the effluent
outfall possessed an inherent toxicity relative to the laboratory controls, apparently due to the
naturally occurring sodic content. Sediment samples collected downstream of the effluent
outfall showed a greater toxicity than upstream controls. Ultimately, no correlation was ever
established between elevated Site-related contaminants and toxicity.
Soil Quality
Surface and subsurface soil samples were collected from fields surrounding the Monsanto
Plant. Regional control samples were collected from soils similar to those that surround the
Plant in areas thought to be unaffected by Monsanto Plant emissions. For risk assessment
purposes, EPA used results from the O-to-1 inch depth interval as the most likely zone of
human exposure. Contaminants elevated above background for the O-to-1 inch depth interval
were aluminum, arsenic, beryllium, cadmium, chromium, manganese, silver, vanadium zinc,
lead-210, polonium-210, radium-226, thorium-230, and uranium-238. The elevated soil
contaminants that exceeded risk-screening criteria for residential use and were thus considered
contaminants of potential concern were arsenic, beryllium, cadmium, vanadium lead-210,
polonium-210, radium-226, thorium-230, uranium-238. No soil constituents exceeded
ecological screening levels. Tables showing these results in detail are included in Appendix A.
Many of the contaminants of potential concern were clustered outside the northern and
southern boundaries of the Plant. The general distribution of contaminants of potential concern
in the soils surrounding the Plant is shown in Figures 4 and 5.
18
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Monsanto Chemical /
Company.
Uononto Plant Boundary
A> 5.4
B* 3.5
Cd 83
Pb-210 7.2
FU-226 3.4
U-2JI 3.1
Zn 1740
A> 5.6W.6D
B« 2.0C.OO
Cd 1&0/14JO
Pb-2io
R*-226 4JV3.8D
O-236 4JV4.1D
Zn
As 4.0
B, t.O
C<) 6.8
Pb-210 10
R»-226 5J
U-2U
Zn 130J
Sam: SaO* Spring*. **tnPn*ntan*Enl962. ma
UanuMa. Plus* u m Owen (OaUft, I995J.
EXPLANATION
S-x or S2-x ^ Phase I soil sample locations
MS2-x (•) Phase II sol sample locations
The values presented are from soil samples collected (ram 0-1'
depth Interval.
Metal (As, Be. Cd, Zn) concentrations are In mgAo. Radkxuoide
(Pb-210. Ra-226. U-238) concentrations are In pCa/fl. A T suffix
Indicates an estimated concentration and a IT Indicates the
result of a duplicate sample.
Arsenic (As)
Beryt§om(Be)
Cadmium (Cd)
Lead-210 (Pb-210)
Radium (Ra)-226
Uranium (U)-238
2nc(Zn)
0 2000
Scale In Feet
Monsanto Site
CONCENTRATIONS OF CONTAMINANTS
OF CONCERN IN SOILS - Phase 1 Samples
Figure 4
-------
A> 1.7R
B. O.ZSU
Cd 0.57
Pt-210 3J
Ra-226 1.2U
U-Z30 1.2U
Zn
Sam:SodiSpring*. UttaPt
EXPLANATION
S-x or S2-x • Phase I sofl sample locations
US2-X ® Phase II sofl sample locations
Constituent
Arsenic (As) '
Berylliurn (Be)
Cadmium (Cd)
Uad-210(Pb-2lO)
Radium (Ra)-226
Uranium (U)-238
The values presented are from soB samples coDected from the
O'-l1 depth WervaL
Metal (As. Be. Cd. Zn) concentrations are In mp>kg- RadbnudkJe
(Pb-2»0. Ra-226. U-238) concentrations are In pCVg. A IT suffix
indfcates the oonstltuent was not detected at or above the
concentration Indicated, a T indicates an estimated
concentration, and a *D* Indicates the result of a duplicate
Monsanto Site
CONCENTRATIONS OF CONTAMINANTS
OF CONCERN IN SOILS - Phase 2 Samples
Figure 5
-------
Groundwater Quality
Groundwater from 60 well locations and 18 spring locations at and in the vicinity of the
Monsanto Plant were sampled and chemically analyzed by Monsanto from the mid 1980's to
the present. Control data were obtained from wells and springs upgradient of any known
sources of constituent releases from the Monsanto Plant, and were separated according to
groundwater type (fresh or sodic). Upper tolerance limits (UTLs) based on human consumption
were established for the control data for each constituent in each groundwater type.
The maximum concentration of each constituent by groundwater region and groundwater type
was compared to the corresponding UTL for that constituent (see Appendix A). Contaminants
with maximum concentrations exceeding the UTL for each groundwater region and
groundwater type were considered elevated contaminants. Of those, calcium, magnesium,
potassium, and sodium are essential nutrients, and bicarbonate is a nontoxic substance,
therefore these contaminants were eliminated from further consideration in the Rf. Beryllium
and chromium were detected sporadically, and were eliminated from further consideration.
The remaining elevated contaminants were reviewed by preliminary risk-based screening. In
this screening, the maximum concentrations of each elevated constituent (by groundwater
region and type) were compared to background, MCLs, and human health risk-based
concentrations using standard default values. Elevated contaminants with maximum
concentrations exceeding the screening values in fresh groundwater were: ammonia nitrogen,
arsenic, cadmium, chloride, fluoride, iron, manganese, molybdenum, nickel, nitrate, selenium,
sulfate, vanadium, and zinc. Elevated contaminants with maximum concentrations exceeding
screening values in sodic groundwater are the following subset of the fresh groundwater group:
ammonia, nitrogen, arsenic, chloride, molybdenum, nickel and vanadium.
Chloride, iron, and sulfate failed preliminary risk-based screening solely due to exceedances of
their respective secondary MCLs (e.g. odor, color). Since secondary MCLs are aesthetic-based
rather than health-based criteria, these contaminants do not represent potential risks to human
health and were eliminated from further consideration as contaminants of potential concern.
Manganese also exceeded the secondary MCL. However, it was retained as contaminant of
concern because of exceedences of risk-based concentrations (0.18 mg/l equated to an HI of 1
in the Monsanto and Kerr-McGee assessments) beneath the Plant, not the secondary MCL.
Off-Plant migration of contaminants has only been detected in the UBZ-2 groundwater region.
Therefore, contaminants of potential concern for groundwater were identified as those elevated
contaminants in the freshwater portion of UBZ-2 region that exceeded risk-based screening
criteria, plus all Site-related contaminants which exceeded MCLs. These contaminants were
cadmium, fluoride, manganese, molybdenum, nickel, nitrate-nitrogen and selenium. Tables
showing these results in detail are included in Appendix A.
Biota.Quality
As previously discussed, toxicity testing has been conducted on selected Soda Creek sediment
samples. No effects on biota were identified that could be associated with the elevated
concentrations of cadmium found in the sediments. No exceedances of water quality criteria
for protection of aquatic organisms were identified.
21
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MONSANTO
PLANT
srre
KERR-McGEE
PROPERTY
KERR-McGEE
PLANT SITE
MORMON 8
-------
Population and Environmental Areas that Could Be Affected
The City of Soda Springs is located approximately one mile south of the Monsanto Plant and
has a population of about 3,000. The Monsanto Plant employs about 400 people (who live in or
near the City) and the adjacent Kerr-McGee Plant employs about 80 people.
According to the FS, properties adjacent to the Monsanto facility are owned by eleven different
owners of record. To the East is Kerr-McGee and its 40 workers. To the southeast is the City
of Soda Springs industrial park with more industrial properties and workers. Monsanto owns
most of the property due south of the plant but does not currently make active use of it. There
is one home about 0.2 miles south of the Plant. The property to the west is zoned agricultural
(which allows for residential use) and is typically used for horse grazing. The nearest home to
the west is the property owner's dwelling, approximately one half-mile away. The land to the
north includes several parcels owned by different owners. The land is zoned agricultural and is
currently in agricultural set-aside or being fanned, except one parcel which Monsanto owns.
Monsanto employee drinking water is supplied by production well PW-4 on the northern
boundary of the Plant, which is upgradient of any potential Site-related sources of constituent
releases. Kerr-McGee Plant drinking water is supplied by the City. Most local residents are
on City water; no one is known to be using downgradient wells for drinking purposes and the
City supplies are adequate for any anticipated population increase. The City obtains its drinking
water from Formation Spring (located northeast of the Plant) and Ledger Spring (located to the
southeast of the Plant). These springs are not threatened by the Site. There are no wells
located down-gradient of the Monsanto Plant currently used for drinking water purposes.
Soda Creek, which receives non-contact cooling water discharges from the Plant and which is
recharged by groundwater from beneath the Plant, is largely sodic near the Plant and
increasingly fresh as it nears Alexander Reservoir. The Creek supports a limited range of
species, apparently due to its sodic nature.
The one area of special historical interest in the vicinity of the Monsanto Plant that could
potentially be affected by Site-related contamination or remedial actions is Hooper Spring, a
soda-water spring downgradient from the Plant. Groundwater contamination could conceivably
eventually reach Hooper Spring if concentrations do not attenuate as predicted.
The Plant and surrounding region is covered by a sagebrush-grass vegetational zone.
Significant fish and wildlife habitats include the Bear River, Alexander Reservoir, and the
Formation Cave vicinity (a property owned by the Nature Conservancy). Waterfowl have been
known to use the non-contact cooling water ponds at the Plant throughout the year. The bald
eagle was the only endangered species identified near the City. According to the US Fish and
Wildlife Service, bald eagles winter in the Bear River/Alexander Reservoir area. The hoary
willow is listed as a sensitive species. The willow is found along Ledger Creek. None of the
above are known to be affected by constituent releases from the Site.
23
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Contaminant Transport
Potentially significant constituent transport pathways for the Monsanto Plant, as defined by
exceedences of preliminary risk-based screening results, are shown in Table 2.
Table 2
POTENTIALLY SIGNIFICANT CONSTITUENT TRANSPORT AND EXPOSURE
PATHWAYS IDENTIFIED IN THE Rl FOR THE MONSANTO PLANT
Air Transport
Surface Water
Transport
Direct Contact with
Soils and Source Piles
Groundwater
Transport
Inhalation of arsenic, beryllium, cadmium, fluoride, manganese,
molybdenum, silver, vanadium, zinc, lead-210, polonium-210,
radium-226, thorium-230, uranium-234, and uranium-238 derived
from fugitive dust from source piles and roads, and from stack
emissions from the Monsanto Plant.
The discharge of contaminants in non-contact cooling water and
groundwater to Soda Creek represents a potential transport
pathway. No COCs were identified, however cadmium levels are
elevated with respect to background.
Ingestion of arsenic, beryllium, cadmium, lead-210, polonium-210,
radium-226, thorium-230, and uranium-238 or external exposure to
the radionuclides in the source piles or the soils adjacent to the
Monsanto Plant.
There is no current pathway for groundwater ingestion. Drinking
water wells could be installed, although City^ water is available.
There is a potential for future discharge of contaminants of concern
(cadmium, fluoride, manganese, molybdenum, nickel, nitrate-
nitrogen, and selenium) from beneath the Monsanto Plant to Soda
Creek.
24
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6. SUMMARY OF SITE RISKS
The data from the Rl were evaluated in both a baseline human health risk assessment (HHRA)
and an ecological risk assessment (ERA). These assessments utilized conservative (i.e.,
protective), yet reasonable exposure assumptions and scenarios to predict the likelihood of
human health and environmental impacts resulting from Site-related contamination. Risk
estimates are given in more detail in Tables 2-4, and Appendix A, which includes Tables
identifying the concentrations of the contaminants of potential concern by media.
HUMAN HEALTH RISK ASSESSMENTS
EPA's Baseline Human Health Risk Assessment (HHRA)
The baseline risk assessment was prepared by EPA using information gathered by Monsanto
for the RI/FS. Risk assessment data needs were identified in the initial planning for the Rl and
were refined as additional Site characterization was performed. All environmental samples
collected and analyzed in the Rl were evaluated for the risk assessment. Sufficient data were
available to perform the baseline risk assessment, and data gaps identified were addressed
before the RI/FS was considered complete.
The scope of the assessment included all potential chemical hazards and carcinogenic risks to
human health attributable to uncontrolled releases of hazardous substances to the environment
at or from the Plant in the absence of any remedial action. Actual and potential risks to human
health in residential and industrial settings were evaluated under current and future scenarios.
The risk assessment was complicated by several factors, including:
• The fact that this is an operating industrial facility, and is likely to remain as such;
. The presence of radionuclide as well as chemical health hazards (radionuclide
hazards have traditionally been measured and evaluated differently than
chemical hazards);
• Relatively high levels of background radioactivity in the area;
• The complexity of the hydrogeology, reflecting the presence of fractured basalt
and multiple ground water sources; and,
• The proximity to the Kerr-McGee facility, across the highway from the Monsanto
Site. Kerr-McGee is also a Superfund Site. Separate RI/FS's were prepared for
each Site; information from both Sites was considered in the selection of
remedy.
APPROACH AND KEY ASSUMPTIONS
The baseline human health risk assessment was conducted using appropriate EPA and
Superfund guidance. Both current and future scenarios were developed to evaluate potentially
significant human health risks. Total hazards and risks were calculated by analyzing scenarios
25
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based on multiple exposures within localized areas. All environmental samples collected and
analyzed in the Rl were evaluated for useability in the HHRA based on the scenarios selected.
Equations to assess chemical intake and associated risks, along with appropriate default
parameters, were derived from EPA guidance documents. These exposure parameters yield
conservative (i.e. health-protective) risk estimates. Key assumptions made before completing
the risk assessment include:
• The Plant is an operating facility. Workplace exposures or risks that were not
attributable to uncontrolled releases to the environment (e.g., exposure to high
temperatures, noise or controlled emissions inside furnace buildings) were
beyond the scope of the assessment. Such exposures are the purview of the
Occupational Safety and Health Administration (OSHA);
• Chemical concentrations in environmental media and resulting exposures remain
constant over time;
• Residences could be built in the most-contaminated areas adjacent to the plant;
• Ground water could be used in a future residential scenario for drinking and
household use;
. Potential exposure associated with disposal of slag at the facility was evaluated.
However, the use of slag in the community for roads, etc., is the subject of a
separate study and was beyond the scope of this RI/FS; and,
• Except where Site-specific exposure information has been documented, EPA
default parameters are representative of the potentially exposed populations.
The HHRA followed EPA guidance and used a deterministic (i.e., point-estimate) approach to
identify those contaminants present in environmental media (e.g., off-Plant soil and
groundwater) and on-Plant source materials that could potentially pose adverse health effects
to current and future on-Plant workers and off-Plant residents.
The following exposure scenarios were developed based on local land use and EPA Region 10
risk assessment guidance (details of the exposure assumptions are provided in Appendix A):
• Current Occupational. Risks posed to individuals who currently work at the Plant
were evaluated using modified exposure assumptions to account for local
climate information (severe winter weather limits some exposure) and time-and-
location data provided by Monsanto (to better quantify exposure durations at
various locations within the plant). This evaluation focused on exposure to on-
Plant source materials via ingestion, external radiation (for radionuclides), and
inhalation of Site-related emissions (i.e., fugitive dusts and stack emissions).
• Future Occupational. Risks were calculated for individuals who were assumed
to be exposed to on-Plant source materials using EPA default industrial
26
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exposure assumptions. This approach assumed that unrestricted exposure to
on-Plant materials or groundwater could occur in the event that the Monsanto
Plant closed and the Plant was abandoned.
• Current Residential. Risks posed to individuals living beyond the Plant boundary
were evaluated using soil samples nearest current residences. Exposures to
soils surrounding the Plant via ingestion and external radiation (for radionuclides)
and inhalation of Site-related emissions (i.e., fugitive dusts and stack emissions)
were included in this scenario. No groundwater consumption was evaluated
since groundwater is not currently used for drinking purposes.
• Future Residential. The exposure assumptions for the hypothetical future
resident were similar to those for the current resident, except that local
groundwater was assumed to be used as a source of drinking water for residents
to the South. Note that future residential scenarios assume residential exposure
to the highest concentrations in soils near the Plant, where no residences
currently exist.
Site-specific Exposure Assumptions Used for Workers:
The current industrial scenario evaluated exposure based on modified exposure
assumptions, including:
• Source-Specific Estimates: For risks to workers, exposure at each source of
contamination was evaluated separately. Reasonable maximum exposures
were evaluated by choosing source areas where relatively high concentrations
occur. The areas also were selected based on the conceptual model, Site-
specific exposure information provided by Monsanto, and COPC concentrations
in the source materials. Specific sources evaluated included the underflow
solids, nodules, treater dusts, slag, baghouse dusts, as well as road dusts.
Exposure Durations: EPA assessed risk to workers using both default and
Site-specific exposure durations. Site-specific estimates were developed based
on Plant-specific worker time-and-motion information provided by Monsanto and
were used because they best represented potential exposures, which vary with
proximity to different sources. The default assumption is 8 hours per day 250
days per year, while the revised estimates ranged from 1-6 hours per day for
160-250 days/year. The modified assumptions used in the final risk assessment
are given in Table 1.
Toxicity Assessment
Quantitative estimates of toxic response developed by EPA were used to evaluate potential
cancer and non-cancer toxicity of contaminants. Generally, cancer risks were calculated using
toxicity factors known as slope factors, while noncancer hazards were estimated using
reference doses. Toxicological uncertainty factors and critical effects were obtained from the
EPA Integrated Risk Information System (IRIS), or if no IRIS values were available, from the
Health Effects Assessment Summary Tables and EPA Environmental Criteria and Assessment
27
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Office memoranda, as noted in the Risk Assessment.
Table 1 - Exposure Assumptions for Current Industrial Scenario
Source Material
Baghouse Dusts
Nodules
Slag
Road Dusts
Treater Dusts
Underflow Solids
Task
Reclaim Operator
Bin Operator
Pot Carrier Operator
Water Truck Operator
Loader Operator
Loader Operator
Hours/
Day
1.5
1.5
4
6
1
6
Days/
Year
250
250
250
160
250
180
Shielding
Factor
0
0
.45
.45
.45
.45
Shielding: EPA used revised shielding factors based on data Monsanto collected from
the cabs of the vehicles used by workers. The 95th percentile dose reduction factor was
derived from Monsanto's dosimetry data for heavy vehicles. This value (0.55) was
subtracted from 1 to yield a shielding factor of 0.45.
Risk Characterization
In summary, arsenic, beryllium, cadmium, and radionuclides (including lead-210, radium-226,
thorium-230 and uranium-238) present in soils and source piles were identified in the HHRA as
contaminants of concern at the Site because they pose carcinogenic risks greater than 1x1 O*6.
The potential for other, non-cancer health effects were evaluated, but none were found which
currently posed an HQ greater than 1 except manganese, as explained below. Risks
associated with ingestion of groundwater were evaluated for the future residential scenario.
Future residents or well-users living south of the Plant could be exposed to contaminants in
groundwater that exceed primary MCLs (i.e., cadmium, fluoride, nitrate, and selenium), or risk-
based concentrations (manganese, potentially) if wells were installed and the groundwater were
used as a source of drinking water. Manganese currently exceeds risk-based concentrations
only beneath the Plant.
Carcinogenic risks associated with external exposure to radium-226 were determined to be the
principal concern for both on-Plant source materials and soils surrounding the Plant, for most
scenarios. The exception was the current residential scenario, for which excess carcinogenic
risks from metals (1E-5) are higher than radionuclide risk (4E-6) because that scenario used
samples nearest current residences. More contaminated samples from closer to the Plant
boundary fence were not used in the current scenario, since no residences are currently located
there, or those risk estimates would have been higher. For the future residential risk scenario,
estimates were done using sample locations closer to the fence and therefore the estimated
risks are higher. Ingestion of metals (arsenic, beryllium) was also of concern in the future
residential scenarios. The results of the HHRA are summarized in Tables 2 and 3.
28
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Table 2 : Incremental Risk Over Background - Industrial Scenarios
CURRENT SCENARIO RISK
Site"
Background6
Increment over
Background
FUTURE SCENARIO RISK
Site'
BAGHOUSE DUST AREA
Metals
Radionudides
3E-5
6E-4
1E-6
3E-5
NODULES AREA
Metals .
Radionudides
1E-5
5E-4
6E-7
2E-5
" .'m&f* <-
*?l&' ^teSN^ ''-
7E-5
1E-3
Background"
Increment over
Background
2E-6
6E-5
':M^*e# :,,^
?&&SHiagf's:
*«•#>' 'sJi&jS'v^'y^ 0
1lS8«8SB^;v^
5E-5
2E-3
2E-6
6E-5
SLAG AREA
Metals
Radionudides
5E-5
2E-3
2E-6
6E-5
'•^•h^jsi^^r^ v
i^fT^jf \; "'-ȣ
ROAD DUSTS AREA
Metals
Radionudides
3E-5
8E-4
1E-6
3E-5
¥jfa>m£L *...:.*.
JPFiNF^'-'
TREATER DUST AREA
Metals
Radionudides
4E-5
1E-3
2E-6
6E-5
-$l&fc>«
v~ •<&&&&:*<,
\ %t xiBwp\rij
-«** ; "2E¥V -3?
>,' ...;'46«$r :„„
^T'5"'^^/ ^/"
* • :5"«E-a • " '
: :.«&$'
UNDERFLOW SOLIDS AREA
Metals
Radionudides
9E-5
1E-3
2E-6
5E-5
'• >*t "SE-SL,,"- "
*r* "ie~$ \ >,
1E-4
2E-3
2E-6
6E-5
1S4-' ;
«B*"-''
a = includes ingestion. external, and inhalation
b = includes ingestion and external
Table 3: Incremental Risk Over Background - Residential Scenarios
SCENARIO RISK
Site"
Background"
Increment over Background
Ingest. External
Inhalation
CURRENT SOUTHERN
RESIDENTIAL LOCATION # I*
Metals
Radionudides
6E-05
2E-O3
2E-05
3E-04
''$&$$""': ' **\
' * vaftDfr*';*- i
- ^.mm&rz
" '-' <&GS; ->"?*
CURRENT SOUTHERN LOCATION II*
Metals
Radionudides
4E-O5
2E-05
2E-05
3E-04
> '; - JE-OS^, /» i
*.!..?.:- -WB. ./-.<... '?
••>'-' ,\&® '"'*
:;..* .m**"*.:-"'
CURRENT WESTERN RESIDENCE*
Metals
Radionudides
2E-05
9E-06
2E-05
3E-04
CURRENT NORTHERN RESIDENCE*
Metals
Radionudides
1E-O5
6E-06
2E-05
3E-04
^f^^^BS M?%j$tl
'•W' *""fi'& '<£$&%$,
?*$%
'«~'<& j4%gJQ$' '•#&?£
',"''''',' '''BB ' '•'", '',,'/:
*}' £?••''''&&''"'''/, ' " ft,
* y( -'3^96;^^ ,
r f '/- '2E-06;^!5^'%
FUTURE SOUTHERN LOCATION*
Metals
Radionudides
5E-05
2E-05
2E-05
3E-04
JTr ':'$&<# '.T.\
.:*'•'•' '«&*. .-; -
??...%&»'&.... '
*,'-} '2lJ&5^ ;' ,
FUTURE NORTHERN LOCATION I*
Metals
Radionudides
1E-04
2E-03
2E-05
3E-04
' "', '"few-'-/ *
-, /;/ ,$&*$/' "-'$
'"-' imas'-,., '- :-
"-:•< ,> 38-0$ - •;' '--
FUTURE NORTHERN LOCATION II*
Metals
Radionudides
5E-05
4E-04
2E-05
3E-04
,--,{ 2E-OS'-"'" >
'"• - Y1S4«'^" '"
'' -,. ,«E-06 - '-'
s- ' ' $£^06 - "
a = includes ingestion, external, and inhalation • See Appendix A for Map of Locations Used in HHRA
b = includes Ingestion and external
BB = Risk from COCs in so I below soil background risk
-------
Table 4
Summary of RME Residential Risks in Excess
of Background Risks
Residence
Ingestion
iE-4
>E-4
External
*E-4
>E-4
Inhalation
*E-4
>E-4'
CURRENT SOUTHERN 1
Metals
Radionuclides
As. Be
Pb-210+D
Ra-226+D
U-238+D
Ra-226+D
As, Be. Cd
Th-230
U-238+D
CURRENT SOUTHERN II
Metals
Radionuclides
As, Be
As. Be. Cd
Th-230
U-238+D
CURRENT WESTERN
Metals
Radionuclides
Cd
U-238+D
•
CURRENT NORTHERN
Metals
Radionuclides
Cd
U-238+D
FUTURE SOUTHERN
Metals
Radionuclides
As, Be
(F. Se)'
As. Cd
Th-230
U-238+D
FUTURE NORTHERN 1
Metals
Radionuclides
As, Be
Pb-210+D
Ra-226+D
U-238+D
Ra-226+D
As.Cd
Pb-210+D
Th-230
U-238+D
FUTURE NORTHERN II
Metals
Radionuclides
As, Be
Pb-210+D
U-238+D
Ra-226+D
As.Cd
Th-230
U-238+D
a = Hazards from ingestion of ground water
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Uncertainties
Uncertainties associated with the risk assessment include:
• The use of conservative assumptions with regard to exposure parameters in future
scenarios and for current scenarios where Site-specific data was not available.
• Some assumptions regarding future land uses surrounding the Plant such as new
residences adjacent to the Plant, or drinking water wells in contaminated groundwater,
are highly speculative (the Plant itself was assumed to remain industrial);
• The Reasonable Maximum Exposure scenarios only represent a small subset of the
existing workforce. It was assumed that individuals working indoors are not exposed to
releases from the source areas under consideration;
• Because of the dynamic nature of the numerous job tasks at the Monsanto Plant, some
individuals may be exposed to more than one source area or may spend a longer time
at a particular source area, than what was assumed under the RME scenarios.
Therefore risks may be underestimated;
• The residential scenarios are default factors that assume that the individuals stay at
home for 24 hours/day, 350 days/year, for 30 years. This is likely an overestimation of
the amount of time that people are actually at their residences;
• Agricultural exposures were not evaluated in detail. It was assumed that an incremental
risk will occur from working in contaminated agricultural soils, but no measurements or
Site-specific estimates were prepared. However, the individual is not expected to
receive risks greater than under the industrial scenario, and in any event should be less
than the conservative residential scenario.
Uncertainties Related to Radionuclide Risks
There were several uncertainties related to radionuclide risk identified in the Risk Assessment
and subsequent to it that have been considered in this remedy. These include the following:
• The calculation of risk from external exposure assumed that any gamma-emitting
radionuclide in soil is uniformly distributed in that soil within a finite soil depth and
density, and dispersed in an infinite plane geometry. The depositional pattern of
radionuclides in soils outside the Plant boundary forms a steep concentration gradient
outward from the perimeter. In addition, most of the radionuclides were deposited in a
surficial layer (0 to 1 inch depth), resulting in irregular vertical distributions. These non-
uniform distributions result in uncertainties that tend to overestimate risks.
4 In 1995, subsequent to completion of the HHRA, EPA revised the slope factors for
radionuclides in HEAST. The revised factors increased the risk associated with
radionuclides by almost 100% for the population from ages 0-30 and by about 20% for
the general population. Given the revised slope factors, the risk assessment likely
31
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underestimated the associated risks. However, EPA determined that the estimates in
the HHRA were representative and adequate for risk management decision-making at
this Site.
In order to maintain comparability with other risk assessments, for radionuclide risks
EPA used the default slope factors for the general population, which conservatively
address all populations. Consequently, the slope factors used in the risk assessment
may have overestimated risks posed to adult workers.
Monsanto's Stochastic Risk Assessment
Subsequent to the release of EPA's HHRA, Monsanto released its own probabilistic, or
stochastic risk assessment (SRA). The aim of this document was to refine the exposure
assumptions, toxicity values, and risks presented in EPA's HHRA. The SRA focussed solely on
risks associated with external exposure to radium-226 and ingestion of arsenic. Due to
numerous inconsistencies between the SRA and EPA guidance (and CERCLA requirements),
the SRA was of limited utility in the risk-based decision-making process.
ECOLOGICAL RISK ASSESSMENTS
EPA's Ecological Risk Assessment
EPA's Baseline Ecological Risk Assessment (ERA) results were considered in the development
of remedial action objectives (RAOs) in the FS. The baseline ERA indicated that the potential
for terrestrial ecological risks or effects to sensitive/threatened species appeared to be minimal
outside the Monsanto Plant boundaries; however, potential aquatic effects were noted. Neither
EPA nor the State of Idaho had sediment quality criteria for the elevated contaminants of
potential concern. For comparison purposes, surrogate values from Wisconsin and Ontario
were used to identify the following contaminants of potential concern: arsenic, cadmium,
copper, nickel, and selenium.
Subsequent to completion of the baseline ERA, Monsanto examined the potential risks
associated with contaminants in Soda Creek. While elevated concentrations of several
contaminants were indicated and some effects were identified, the contaminants were not
statistically correlated with ecological effects. The final ecological assessment concluded that
ecological impacts were unlikely, and that ecological risk-based target cleanup levels (TCLs)
should not be used to set remediation goals.
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NEED FOR ACTION
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.
Where the baseline risk assessment indicates that cumulative site human health risk using
reasonable maximum exposure assumptions for either current or future land use exceeds the
10"4 lifetime excess cancer risk end of the risk range, or if MCLs or non-zero MCLGs are
exceeded, action under CERCLA is generally warranted at the site. Assuming no further
action is taken to reduce risk, risks at the Monsanto Site exceed 10"4 for radionuclides and
background for metals under the future residential and industrial scenarios. In addition,
contaminant concentrations in groundwater exceed MCLs beneath and to the south of the
Plant. Action is therefore warranted at this Site.
REMEDIAL ACTION OBJECTIVES
This section addresses the NCP requirements to establish remedial action objectives specifying
the contaminants and media of concern, potential exposure pathways, and final remediation
goals when the remedy is selected.
Background on Remedial Action Objectives
The NCP requires that remediation goals establish acceptable exposure levels that are
protective of human health and the environment, taking into consideration ARARs, if available.
For known or systemic carcinogens, the NCP says that "acceptable exposure levels are
generally concentration levels that represent an excess upper bound lifetime cancer risk to an
individual of between 10"* and 1 Dousing information on the relationship between dose and
response. The 1O"6 risk level shall be used as the point of departure when ARARs are not
available or are not sufficiently protective because of the presence of multiple contaminants at
the site or multiple pathways pf exposure."
OSWER Directive 9355.0-30, dated 4/22/91, further clarifies the role of the baseline risk
assessment in Superfund risk management decisions as follows:
"EPA uses the general 10"4 to lO^risk range as a "target range", within which the Agency strives
to manage risks as part of a Superfund cleanup. Once a decision has been made to take an
action, the Agency has expressed a preference for cleanups achieving the more protective end of
the range (i.e.,), although waste management strategies achieving reductions in site risks
anywhere within the risk range may be deemed acceptable by the EPA risk manager.
Furthermore, the upper boundary of the risk range is not a discrete line at 1 x 1CT4, although EPA
generally uses 1 x 10"4 in making risk management decisions. A specific risk estimate around 1O"4
may be considered acceptable if justified based on site-specific conditions, including any
remaining uncertainties on the nature and extent of contamination and associated risks.
Therefore, in certain cases EPA may consider risk estimates slightly greater than 1 x 10"4 to be
protective. When an ARAR for a specific chemical (or in some cases a group of chemicals)
defines an acceptable level of exposure, compliance with the ARAR will generally be considered
protective even if it is outside the risk range (unless there are extenuating circumstances such as
33
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exposure to multiple contaminants or pathways of exposure). Conversely, in certain situations
EPA may determine that risks less than 1x10"* are not sufficiently protective and warrant
remedial action.
Where current conditions have not resulted in a release posing risks that warrant action but there
is a significant possibility that a release will occur that is likely to result in an unacceptable risk,
remedial action may also be taken. The significance of the potential future release may be
evaluated in part based on the quantities of material at the site and the environmental setting.*
Preliminary Remediation Goals and FS Target Cleanup Levels
After EPA determined that action is necessary at this Site under CERCLA, remedial action
objectives, including preliminary remediation goals (PRGs), were established for three
environmental media: groundwater, soils surrounding the Plant, and on-Plant source materials
(as past and potential future sources of releases to surrounding soils).
A range of preliminary remediation goals and target cleanup levels (TCLs) was developed in the
FS. Monsanto evaluated remedial alternatives for the Site with respect to target cleanup levels
based on a 1 x 10"* human health risk, a 1 x 10"4 human health risk, a 5 x 10*4 human health
risk, the Uranium Mill Tailings Radiation Control Act (UMTRCA) regulations, and on potential
ecological risks only.
TCLs for radionuclides were derived by comparing the preliminary remediation goals to the
upper tolerance limit of background concentration (based on the 95th percentile of the
distribution of all background data) for a particular constituent, and using the greater of the two
values. For example, the "TCL"*" for radium-226 was determined by comparing the PRO
associated with a 1 x 10"* excess cancer risk (2.5 picocuries per gram of soil [pCi/g]) to the
upper tolerance limit background concentration (3.3 pCi/g). Because the upper tolerance limit
was greater than the PRG, the upper tolerance limit was assigned as the TCL. Because the
HHRA identified risks due to radium-226 exposure in soils surrounding the Plant as contributing
the vast majority of total risk, and background radionuclide concentrations pose potential risks
of about 10~* even in the absence of Site related contamination, the FS focused on that TCL as
the basis for evaluating the alternatives.
Since EPA has cited the UMTRCA regulations as the principal radiation-specific federal
requirements at other NPL sites, those regulations were given consideration. However, they
are not ARARs because they are intended for the clean up of uranium and thorium mill tailing
sites, and appropriate for industrial land uses, not mixed agricultural and residential use.
Before it was determined that no final remedial action objectives are necessary for protection of
the environment, ecological PRGs were developed for use in evaluating FS alternatives for off-
Plant soils. The PRGs were developed for protection of plants and mice.
Final remediation goals in this ROD were selected after reviewing the nine criteria analyses for
all alternatives.
34
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Remedial Action Objectives for Groundwater
The Contaminants of Concern (COCs) in groundwater are fluoride, cadmium, selenium, and
nitrate, all of which exceed primary MCLs, and manganese, which exceeds risk-based
concentrations (HQ > 1). No one is currently drinking the affected groundwater. The exposure
pathway of concern for human health is potential consumption of contaminated groundwater
beneath or south of the Plant. The groundwater RAOs for the selected remedy are:
Prevent human ingestion of, inhalation of, or direct contact with ground water at levels
exceeding MCLs for F, Cd, Se, and NO-3, or risk-based concentrations for manganese.
The ultimate goal of the remedy is to ensure that groundwater contamination sources have
been eliminated and that natural attenuation will eventually restore the groundwater aquifers
affected by past releases from the Site.
Remedial Action Objectives for Contaminated Soils Outside the Plant Boundaries
The COCs in soils outside the Plant boundaries are radionuclides and metals (arsenic and
beryllium). The exposure pathways of concern for humans include external exposure to
radionuclides, ingestion of radionuclides and metals, and inhalation of radionuclides and metals
at levels that exceed background and pose an unacceptable cumulative estimated risk. The
final RAOs and remediation goals for this media are:
For Human Health
Prevent external exposure to radionuclides in soils at levels that pose cumulative
estimated risks above 3x1 CT*. Such risks correspond to a radiation effective dose
equivalent of approximately 15 mrem/year for the radionuclides of concern at this Site.
Prevent ingestion or inhalation of soils containing radionuclides at levels that pose
cumulative estimated excess risks above 3 x 10"*, or metals (arsenic, beryllium) at levels
that pose cumulative estimated excess carcinogenic risks that exceed 1 x 10*5, a non-
cancer risk HQ of 1, or Site-specific background levels where that is not practicable.
Rationale for Soil Remediation Goals
ARARs are not available for radionuclides in residential soils, therefore acceptable exposure
levels were developed. The selected remedy for this Site includes soil cleanup of radionuclides
to concentrations which pose a risk of 3x10~* or less above background, assuming residential
land use, using EPA's slope factors and risk assessment methodology. At this Site, the 3x10~*
risk goal corresponds to a radium-226 concentration in soils of 3.7pCi/g and a radiation
effective dose equivalent of approximately 15 mrem/year for the radionuclides of concern.
This goal corresponds to the upper end of the range for cancer risks considered protective at
most CERCLA sites. EPA may consider risk estimates slightly greater than 1x10"* to be
protective based on site-specific conditions, including any remaining uncertainties on the nature
and extent of contamination and associated risks. For this Site, these conditions include the
naturally-occurring background concentrations of the radionuclides of concern, which exceed
35
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1x1 Or* risk and thus make lesser concentrations unattainable, the lack of a uniform distribution
of contaminants in soils, current land use, and associated uncertainties.
The 3x10"4 risk goal for radionuclides js also consistent with levels considered protective in
other governmental actions including regulations and guidance developed by EPA in other
radiation control programs including: (1) EPA's Environmental Radiation Protection Standards
for Management and Disposal of Spent Nuclear Fuel, High-Level and f ransuranic Radioactive
Wastes (40 C.F.R 191) which sets a dose limit of 15 mrem/year (equivalent to a risk of 3x1 Q/4
over 30 years) and (2) EPA's National Emission Standards for Hazardous Air Pollutants (40
C.F.R 61) which sets a standard for radionuclide emissions from operating elemental
phosphorus production facilities such as this one equivalent to a risk of approximately 3x10"*.
To further reduce cumulative excess risk in areas where radionuclides exceed cleanup goals,
the selected remedy will also address metals which exceed background and pose an excess
carcinogenic risk above 1x10"* (arsenic, beryllium), or a non-cancer risk with an HQ of 1 or
more (none identified). This remediation goal was established after first considering the 10"6
point of departure. However, since local background for some of these metals poses > 10"6
risk, the 10s level is the most protective risk level which is measurable and above background.
RAO for Sources of Soil Contamination (Solid Waste Piles)
Solid waste piles on-Plant have in the past been sources of contaminant migration to off-Plant
soils. If workers were frequently exposed to uncontrolled emissions from such piles, risks
would be unacceptable. Preliminary RAOs were developed for source piles for use in the FS.
However, under current conditions, migration to off-Plant soils has been significantly reduced
and effective worker protection programs are in place, so RAOs are not necessary for source
piles as long as these controls remain in place and off-Plant soil concentrations do not increase.
Future On-Plant
Despite potential risks in excess of the risk range (>10*3), cleanup alternatives were not
developed for alternative future industrial scenarios within the Plant because Monsanto is
considered highly likely to continue to operate the Plant for the foreseeable future. Monsanto
has just increased production and maintains it has the reserves to profitably operate the Plant
for over 30 more years.
OSHA-EPA Jurisdiction and Worker Risk Issues
As part of the HHRA, EPA evaluated risks to workers within the operating portion of the Plant
from exposure to uncontrolled releases of hazardous substances. This is necessary at all
CERCLA sites to identify risks which may require remediation and to help guide the study of
feasible alternatives to address such risks. Since EPA and OSHA have complementary
jurisdiction at operating facility sites, EPA determined that OSHA should be consulted and
informed if potential risks to workers were identified, and as appropriate, OSHA standards
should be part of the FS and risk management decision-making at the Site. At the conclusion
of the HHRA and FS, OSHA was informed that the RI/FS identified no uncontrolled releases
which pose unacceptable threats to workers health or safety under current conditions.
36
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7. DESCRIPTION OF ALTERNATIVES
In the FS, eight basic remedial alternatives were developed and then evaluated according to a
range of target risk levels that were considered in the decision process. The remedial
alternatives were developed, evaluated and compared on the basis of effectiveness,
implementability, and cost for their ability to achieve the RAOs at multiple cleanup levels. This
resulted in 44 alternatives being described and compared in the FS . Those remedial
alternatives that were no more effective at achieving the RAOs but cost significantly more were
eliminated. Five alternatives were retained for consideration for the final remedy. Table 5
presents a summary of these alternatives.
The following discussion addresses each alternative in terms of its treatment, containment/
storage and groundwater component and provides an estimation of the implementation time
frame and cost. A discussion of applicable, relevant, and appropriate requirements (ARARs),
risk based levels, or requirements "to be considered" (TBCs) also is provided.
A common element for each of the alternatives discussed is the inclusion of five-year reviews.
In order to facilitate the evaluation of alternatives, the FS discussion focussed on a preliminary
remediation goal based on TCL4, after which additional information was provided on how
different cleanup goals might affect the remedy in terms of protectiveness, implementability
and/or cost. The final remediation goal selected, the rationale for it, and the estimated cost of
the selected remedy are discussed in Section 9, the "Description of the Selected Remedy".
Note on Development of Groundwater Alternatives
While the exceedence of MCLs is sufficient reason to consider remedial action for groundwater,
based on the success of past remedial actions, the characteristics of the groundwater, modeling
which showed that groundwater is expected to recover and achieve MCLs at the southern Plant
boundary in 5-30 years, and knowledge of the expected cost effectiveness of groundwater
treatment at low concentrations, Monsanto proposed and EPA agreed to evaluate only a limited
range of groundwater alternatives, none of which included treatment.
As part of the Rl, Monsanto and its contractors performed groundwater fate and transport
modeling and submitted a report to EPA in 1993. Based on the modeling, without further action
concentrations of constituents in groundwater at the southern Plant boundary will be restored to
background levels within 5 to 30 years, depending on the constituent and its retardation in
groundwater.
Groundwater monitoring data over several years has shown that concentrations of
contaminants of concern are generally decreasing, and that current plant operations essentially
capture the plume (pumping of production wells for non-contact cooling water creates a cone of
depression which is retarding the spread of contaminants and also pumps contamination out.
That groundwater is discharged through the NPDES-permitted discharge to Soda Creek; the
NPDES permit only addresses pH and temperature. The discharged water was found to
contain Site-related constituents at levels below action levels.) To ensure protectiveness the
groundwater monitoring alternatives include monitoring of or below the discharge outfall.
37
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ALTERNATIVE 1: NO FURTHER ACTION
No remedial action would be taken under this alternative. It has been included to provide a
basis for comparison of the other alternatives.
Treatment Components
Alternative 1 does not entail any further treatment for on-Ptant source materials or off-Plant
soils.
Containment/Storage Components
No further action will be conducted to address on-Plant source materials or soils surrounding
the Plant.
Groundwater
Groundwater predictions indicated that past remedial actions, ongoing groundwater pumping,
and natural attenuation processes will eventually result in concentrations decreasing to
background levels throughout the aquifer. Fate and transport modeling conducted during the Rl
concluded that groundwater at the southern Plant boundary (1996 fence line) will be restored to
background levels by natural processes within 5 to 30 years.
General Components
No further action will be taken to address on-Plant sources, off-Plant soil, or groundwater.
There are no treatability studies, implementation requirements, or institutional controls
associated with this alternative. As no groundwater monitoring would be included, there are
uncertainties associated with evaluating whether groundwater concentrations are decreasing
over time. Furthermore, there is no mechanism to prevent the ingestion of groundwater with
contaminants including MCLs or risk based criteria.
There are no costs associated with implementing this alternative.
ARARs
Alternative 1 includes No Action and has no ARARs.
38
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ALTERNATIVE 2: GROUNDWATER MONITORING
Under Alternative 2, no remedial action would be implemented for on-Plant materials and soils
surrounding the Plant. However, a groundwater monitoring program would be implemented
and continued until groundwater achieves MCLs, which is projected to take from 5-30 years. A
thirty year monitoring program is assumed for cost estimation purposes.
Treatment Components
Same as Alternative 1.
Containment/Storage Components
Same as Alternative 1.
Groundwater
In addition to the natural attenuation descried under Alternative 1, this alternative also includes
a 30-year groundwater monitoring program and monitoring of the Plant discharge outfall to
evaluate the trend for contaminant concentrations. Five-year Site reviews would be conducted
until groundwater achieves MCLs and risk-based concentrations at the Point(s) of Compliance.
The program may be discontinued or extended based on concentration trends. It is assumed
that the RI/FS monitoring program of semiannual sampling of approximately 60 monitoring wells
and springs will be reduced after the ROD to about 25-30 wells and springs, including wells in
both the UBZ and LBZ zones and the Plant discharge outfall. Groundwater modeling done for
the RI/FS indicates that the concentrations of contaminants of concern in groundwater at the
Monsanto Plant's southern boundary should return to background levels in 5 to 30 years.
The analytes in groundwater will include cadmium, fluoride, manganese, nitrate, and selenium.
General Components
No further action would be taken to address on-Plant sources, soils surrounding the Plant, or
groundwater. No reduction in risk is associated with this alternative. The groundwater
monitoring program would be conducted for 30 years.
Costs are summarized as follows:
Capital Cost $ 0
Annual Operations and Maintenance (O & M) Cost $ 79,300
Present Worth $1,010,000
ARARs
There are no ARARs which pertain to implementatiQn of this alternative, which is intended to
supply the information necessary to determine when groundwater achieves ARARs (i.e.,
MCLs). It would not in itself satisfy the groundwater MCLs, which are ARARs.
39
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Alternative 4: LAND USE AND ACCESS RESTRICTIONS, AND GROUNDWATER
MONITORING
Alternative 4 includes use and access restrictions for soils surrounding the Plant, and use and
access restrictions and a groundwater monitoring program for groundwater. Note that when
this alternative was evaluated in the FS, dust controls had not been applied yet and so were
considered part of the alternative. Since such controls have since been established and fugitive
emissions are regulated under the State of the Idaho Air Pollution Control regulations and the
Clean Air Act as implemented by the State of Idaho, dust emission control was not considered
part of this alternative by EPA during the selection of remedy.
For soils surrounding the Plant, land-use restrictions include the use of environmental
easements or similar enforceable deed restrictions on the property to limit future land use,
including potential residential development where appropriate, and crop restrictions to prevent
affected property owners from growing food crops for human consumption. Access restrictions
would include establishing a property buffer around the Plant.
Treatment and Containment/Storage Components Components
This alternative does not include any treatment, containment or storage.
Groundwater
Groundwater monitoring provisions are the same as Alternative 2. In addition, land-use
restrictions for groundwater include the use of environmental easements and similar deed
restrictions to prevent affected land owners from installing wells for potable water use. Access
restrictions could include establishing a property buffer around the Site to allow Monsanto to
effectively control water use.
»•
General Components
Risk reduction associated with this alternative comes from institutional controls that would
prevent human exposure to contaminated soils and groundwater and monitoring to ensure that
groundwater recovers and soils are not re-contaminated. Costs for Alternative 4 are estimated
for a period of 30 years, but may need to be in place for a longer or shorter period of time.
Costs are summarized as follows:
Capital Cost $ 570,105
Annual O & M Cost $ 159,820
Present Worth $ 2,570,000
ARARs
Key ARARs for this alternative are summarized in Table 5. There are no chemical specific
ARARs for soils surrounding the Plant. In addition, while they are not ARARs, on-Plant source
controls will comply with state and federal clean air act monitoring and reporting requirements.
40
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Alternative 5: IN SITU BIOLOGICAL TREATMENT, LAND USE AND ACCESS
RESTRICTIONS, AND GROUNDWATER MONITORING
Alternative 5 includes in-situ biological treatment for soils surrounding the Plant, and land use
and access restrictions and a groundwater monitoring program for groundwater. In-situ
bioremediation was identified in the FS as the most promising treatment alternative available for
the soil contaminants and conditions at this Site.
Treatment Components
Oust control measures are the same as for Alternative 4.
For soils surrounding the Plant, in-situ biological treatment would be used to reduce constituent
concentrations. The process would consist of growing crops capable of accumulating the
contaminants of concern in plant tissue, and then disposing of the contaminated crops in a
hazardous waste landfill if needed. Over time (estimated 7 years) the remaining soil would be
rendered non-hazardous and available for unrestricted use.
Containment/Storage Components
This alternative does not include any containment or storage components.
Groundwater
Same as Alternative 4.
General Components
Risk reduction would result from biological treatment of soils surrounding the Plant to reduce
the toxicity, mobility, and volume of contaminated material. Original excess risk levels,
estimated in the HHRA, were as high as 2 x 10"3 from ingestion and external radiation risks from
radium-226 exposure.
Alternative 5 would be in effect for a period of 30 years. Operating costs are summarized as
follows:
Capital Cost $ 305,006
Annual O & M Cost (Years 1-5) $ 660,487
(Years 6-10) $ 157,200
Present Worth $ 4,400,000
ARARs
Same as Alternative 4. In addition, disposal of material from the biological treatment of soil will
comply with hazardous waste requirements and land disposal restrictions. Key ARARs for this
alternative are summarized in Table 5.
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Alternative 8: SOIL EXCAVATION/ REPLACEMENT/CONTAINMENT ON-PLANT, PLUS
GROUNDWATER MONITORING
Alternative 8 includes contaminated soil removal, replacement, and disposal of contaminated
soils by containment within the Plant; and for groundwater, land use and access restrictions and
a groundwater monitoring program.
Treatment Components
For soils surrounding the Plant, the upper six inches of affected soil will be removed and used
as cover material for the on-Plant source material piles. The estimated volume of surrounding
soils with constituent concentrations greater than the remediation goal of 3x1 O*4 is estimated to
be as much as 200,000 cubic yards (equivalent to an area of about 250 acres, of which
Monsanto owns about 1/5th). The remediated off-Plant areas would be restored by placing
clean fill material within the excavated area and re-vegetating the area. There are no chemical
specific ARARs for soils surrounding the Plant.
Containment/Storage Components
Excavated soils brought onto the Plant could be used as cover but would have to be contained
sufficiently to ensure they would not migrate to soils or groundwater.
Groundwater
Same as Alternative 4.
General Components
Risk reduction would result from the removal of soils surrounding the Plant to reduce the
toxicity, mobility, and volume of contaminated material. Risk levels estimated in the HHRA
were as high as 2 x 10"3 from ingestion and external radiation risks from radium-226 exposure.
Alternative 8 would be in effect for a period of 30 years.
Operating costs are summarized as follows:
Capital Cost $ 13,854,274
Annual O & M Cost $ 159,820
Present Worth $ 15.860,000
ARARs
Same as Alternative 5. In addition, removal and disposal of off-Plant soil will be done in a
manner which complies with Idaho solid waste management regulations. Key ARARs for this
alternative are summarized in Table 5.
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TABLE 5
SUMMARY OF ALTERNATIVES RETAINED FOR ANALYSIS
AND POTENTIAL ARARs
Media
On-Plant Sources
Off-Plant Soils
Groundwater
Potential ARARs
requiring compliance:
29CFR1910and29CFR
1926 (Regulate Worker
Health/Safety)
40 CFR 50 (Primary and
Secondary Air Quality
Standards)
40 CFR 141 (National
Drinking Water Standards)
40 CFR 261 (Identification
and Listing of RCRA
Hazardous Wastes)
40 CFR 264 (Standards for
Owners & Operators of
Hazardous Waste Treatment,
Storage. Disposal Facilities)
40 CFR 268 (Land Disposal
Restrictions)
40 CFR 302 (Designation.
Reportable Quantities and
Notification)
IDAPA16.01.01.01.651.2
(Idaho Air Pollution Control
Regulations)
IDAPA, Sections 16.01.2000
et.seq. (ID Water Quality and
Wastewater Treatment
Requirements)
IDHW, Title 1, Chapter 6.
Sec. 01.6001 et. seq.
IDHW, Title 1, Ch 6, Sections
01.6001 (Idaho Solid Waste
Management Regulations)
Alternatives
i
No Action
No Action
No Further
Action
2
No Action
No Action
Monitoring
X
X
X
X
X
X
4
Dust Control
Land-Use Restrictions*
Access Restrictions
Monitoring.
Access/Land Use
Restrictions
X
X
X
X
X
X
X
X
X
5
Dust Control
In-Situ Biological
Treatment
Monitoring,
Access/Land
Use Restrictions
X
X
X
X
X
X"
X
X
X
X
X
8
Dust Control
Excavate/Contain
On-Plant
Monitoring,
Access/Land Use
Restrictions
X
X
X
X
X
X"
X
X
X
X
X
• Includes property buffer
** If material must be disposed of off-site
ARAR = Applicable or relevant and appropriate requirements
CFR = Code of Federal Regulations
IDAPA = Idaho Administrative Procedures Act
IDHW = Idaho Department of Health and Welfare
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8. SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The comparative analyses assess the relative performance of each alternative evaluated in
detail in the FS with respect to the nine NCR evaluation criteria. The objective of this
comparison is to assess relative advantages and disadvantages of alternatives and identify the
key trade-offs that must be balanced in selecting a preferred alternative.
THRESHOLD CRITERIA
1. Overall Protection of Human Health and the Environment
a) On-Plant Source Materials. Alternatives 4, 5, and 8 provide adequate
protection of human health and the environment by monitoring of soils
surrounding the Plant (to ensure that the Source Material piles, which have been
the sources of releases, have in fact been adequately controlled) and periodic
review of Plant compliance with applicable environmental requirements.
Alternatives 1 and 2 do not eliminate, reduce, or control affected on-Plant
source materials and do not provide for monitoring of soils to ensure that
increased releases would be detected; therefore, they may not be adequately
protective of human health and the environment for these media.
b) Soils surrounding the Plant Alternative 8 protects human health by
permanently removing soils surrounding the Plant with constituent
concentrations that exceed human health risk-based cleanup goals. Alternative
4 protects human health by implementing land use and access restrictions to
prevent residential exposure to soils with constituent concentrations that exceed
human health cleanup goals, and to prevent adjacent property owners from
growing food crops for human consumption that are sensitive to cadmium and
zinc; therefore, Alternative 4 is fully protective of human health and the
environment. Alternative 5 protects human health by using in-situ biological
treatment (accumulating contaminants in crop biomass) to permanently reduce
constituent concentrations to below cleanup goals. Reducing constituent
concentrations would prevent ingestion of and exposure to (for radionuclides
only) solids with constituent concentrations above cleanup goals. Therefore,
Alternative 5 is protective of human health and the environment. Alternatives 1
and 2 do not eliminate, reduce, or control affected soils surrounding the Plant;
therefore, they may not be adequately protective of human health and the
environment for these media.
c) Groundwater. Alternatives 4, 5, and 8 assume that past remedial actions,
ongoing groundwater pumping, and natural attenuation processes will eventually
reduce constituent concentrations to acceptable levels within 30 years. In
addition, Alternatives 4, 5, and 8 include land use restrictions to prevent
landowners from installing wells for potable use. These provisions would prevent
ingestion of affected groundwater until MCLs are achieved, and therefore those
alternatives are considered protective. Alternatives 1 and 2 are not considered
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protective because they do not include controls to ensure that humans are not
exposed to contaminated groundwater, and Alternative 1 does not even include
a groundwater monitoring program to confirm that constituent concentrations
have been reduced to acceptable levels.
2. Compliance with ARARs
a) Soils, all alternatives: There are no chemical-specific or location-specific
ARARs identified for the off-Plant soils. In the event Alternatives 5 or 8 were
selected, there would be action-specific ARARs (i.e., IDAPA 16.01.01.650,
Rules for Control of Fugitive Dust) which would have to be (and could be) met by
the alternatives.
b) Groundwater. Under all alternatives, the groundwater is expected to achieve
ARARs, i.e. MCLs, in the long term as past remedial actions, ongoing
groundwater pumping, and natural attenuation processes reduce constituent
levels below MCLs.
As Alternatives 1 and 2 did not satisfy the threshold criteria, they were not considered further in
this evaluation by EPA.
BALANCING CRITERIA:
3. Long-Term Effectiveness and Permanence
a) On-Plant Source Materials. Alternatives 4, 5, and 8 include monitoring of
soils surrounding the Plant and periodic review of Plant compliance with
applicable environmental requirements. These alternatives are moderately
protective of human health and the environment after the RAOs are achieved.
b) Soils Surrounding the Plant Alternative 8 includes excavation and removal
of all off-Plant soil with constituent concentrations that exceed human health risk-
based TCL-4. Since the reduction in concentrations is permanent, Alternative 8
ranks high in achieving long-term effectiveness and permanence after the RAOs
are achieved. Alternative 5 includes in-situ biological treatment to accumulate
contaminants in crop biomass and permanently reduce constituent
concentrations to TCL-4 and achieve the human-risk based RAOs for off-Plant
soils. The reduction to TCL-4 is estimated to be achieved within 5 years. Since
the reduction in concentrations is permanent, Alternative 5 ranks high in
achieving long term effectiveness and permanence after the RAOs are achieved.
Alternative 4 includes land use and access restrictions to prevent the ingestion
of and/or exposure to soil with constituent concentrations that exceed cleanup
goals and to prevent landowners from growing food crops for human
consumption that are sensitive to cadmium and zinc; therefore, since human
health risks are adequately addressed, Alternative 4 ranks high at providing long
45
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term effectiveness and permanence after the RAOs are achieved.
c) Groundwater. Alternatives 4, 5, and 8 assume that past remedial actions,
ongoing groundwater pumping, and natural attenuation processes will eventually
reduce constituent concentrations to acceptable levels. The degree of
effectiveness and permanence of these alternatives will be dependent on the
successful decrease in constituent concentrations. These alternatives include
institutional controls to prevent the ingestion of groundwater until the MCLs are
achieved. After the concentrations of contaminants are reduced to below MCLs,
the residual risk to human health and the environment would be minimal.
Consequently, these alternatives rank high in providing long-term effectiveness
and permanence after MCLs are achieved.
4. Reduction in Toxicrty. Mobility, or Volume (TMV) Through Treatment
a) Off-Plant Soils. Alternative 5 would reduce the toxicity, mobility and volume of
contaminants in off-Plant Soils by accumulating contaminants in plant biomass
(considered a treatment process); therefore, Alternative 5 ranks high in reducing
TMV of contaminants through a treatment process. Alternative 8 was ranked
highly in the FS because it would reduce the mobility of contaminants in off-Plant
soils by removing all soil with constituent concentrations exceeding human
health risk-based TCL-4; however, this is not considered treatment. Alternative
4 does not include provisions to reduce the TMV of contaminants in soils
surrounding the Plant and consequently, they were ranked the lowest.
b) Groundwater. None of the alternatives considered include provisions to
actively reduce TMV through treatment, since treatment was not considered
cost-effective given the contaminant concentrations, aquifer characteristics and
success of past remedial actions. Natural attenuation processes are expected to
eventually reduce constituent concentrations to below MCLs.
5. Short-Term Effectiveness
a) Soils Surrounding the Plant Alternative 8 does not include provisions to
protect human health until the soil removal process is complete. Human
exposure to contaminants could occur during excavation and material handling.
Alternative 8 was ranked low for short-term effectiveness in the FS. Alternative
5 does not include provisions to protect human health until the in-situ biological
treatment process reduces constituent concentrations to acceptable levels and
achieves the health-risk based RAOs. Human exposure to contaminants could
occur during planting and harvesting activities. Overall, Alternative 5 was ranked
low for short-term effectiveness in the FS. Alternative 4 does not include
provisions to protect human health until the institutional controls are in place, but
there is unlikely to be short-term risk during construction of residences since the
area is agricultural and no residences are likely to be built there in the near
future. Risks to the surrounding community are low, since Alternative 4 would
not result in mobilizing contaminants during construction. Overall, Alternative 4
46
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ranks moderate to high in providing short-term effectiveness.
b) Groundwater. Alternatives 4, 5, and 8: These alternatives would not be
protective of human health until the restrictions are in place, if groundwater were
used for drinking. Further, they would not be protective of the environment (i.e.,
groundwater) until the concentrations of contaminants are reduced to
concentrations below MCLs. However, since there is no current exposure nor
any reason to expect short-term installation of potable wells in the affected area,
this approach should be acceptable. No risks are associated with Site workers
since construction activities are not required. In summary, these alternatives
rank moderate in providing short-term effectiveness for groundwater.
6. Implementabilitv
a) Soils surrounding the Plant Alternative 8: There are no significant technical
barriers associated with removing the upper six inches of soils surrounding the
Plant, although short-term future crop yield from substituted topsoil could be
affected. For this and other reasons, there may be administrative barriers
associated with getting the cooperation of off-Plant property owners in allowing
excavation of soil on their property. If Monsanto is able to achieve a property
buffer around the Site (included in the groundwater remedy), Monsanto could
easily control the soil removal process and the administrative barriers would be
significantly reduced. Consequently, Alternative 8 is considered moderately
difficult to implement. Alternative 5: There are no significant technical or
administrative barriers associated with the actual planting, harvesting, or
disposal of the crops. There may be administrative barriers associated with
getting the cooperation of off-Plant property owners in growing appropriate
crops. Conducting pilot studies would be moderately difficult to perform and may
require a significant amount of time to complete. Consequently, Alternative 5 is
considered comparatively difficult to implement. Alternative 4: There are no
technical barriers that would limit the implementability of Alternative 4, however
there could be local landowner resistance to land use and access restrictions.
Protracted negotiations could result in a lengthy process, making this alternative
moderately difficult to implement.
b) Groundwater. Alternatives 4, 5, and 8: A groundwater monitoring program is
currently in place at the Site, and modifying the existing program would be easily
implemented. Implementing land use and access restrictions would require the
cooperation of off-Plant land owners and could be moderately difficult to
implement as described above. The implementability of these alternatives for
groundwater is considered moderate.
7. Cost
a) Alternatives: 30-year present-value cost to implement is $15,860,000. The
total costs of implementing Alternative 8 are considered to be high.
47
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b) Alternative 5: 30-year present-value cost to implement is $4,400,000. The total
costs of implementing Alternative 5 are considered to be moderate.
c) Alternative 4: 30-year present-value cost to implement is $2,570,000. The total
costs of implementing Alternative 4 are considered to be moderate.
MODIFYING CRITERIA
8. State Acceptance
The State of Idaho DEQ has participated throughout oversight of this RI/FS and assisted with the
development of the proposed plan. The state concurs that Alternatives 1 and 2 would not be protective
for this Site. The State's preferred alternative is Alternative 4, Institutional Controls, where such
controls can be reliably established. Where such controls cannot reliably be established, as may be
the case with some of the off-Plant contaminated soils, the State prefers Alternative 8, active cleanup
via excavation. A concurrence letter from the State of Idaho is included with this Record of Decision.
9. Community Acceptance
About 40 people attended the public meeting and/or provided comments during the 60-day public
comment period. Most commenters said they viewed residential development in the contaminated soil
areas as unlikely, but supported taking some action to prevent unacceptable human exposure. Several
adjacent property owners commented that they viewed their property as having been impacted, their
property values as having been affected, and supported cleanup over land-use restrictions. Some
commenters preferred immediate cleanup, with most of those favoring Alternative 8 rather than
Alternative 5, which was viewed as unproven. Some commenters suggested a modified approach to
soil cleanup, combining institutional controls with a provision to clean up property if/when land use
changes (to residential) were planned.
48
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9. THE SELECTED REMEDY AND RATIONALE
EPA's selected remedy is a combination of elements from 3 alternatives from the FS, as described
below. Along with each component of the remedy is the rationale for its selection:
o The selected remedy for contaminated groundwater is Monitored Natural
Attenuation with Institutional Controls (such as legally enforceable prohibitions on
drinking water wells in the affected area) to prevent human exposure to groundwater
until it recovers. No further action appears necessary, except monitoring of the
groundwater and the Plant discharge outfall, because no one is currently using the
contaminated groundwater for drinking and because the combination of past actions and
natural attenuation is projected to restore groundwater to levels which allow for
unrestricted use and exposure within 30 years. Because groundwater exceeds MCLs,
and risk-based concentrations, reviews will be necessary no less often than every five
years to ensure that the remedy remains protective, confirm that constituent
concentration trends in groundwater and sediments are declining as predicted and
eventually to confirm the achievement of MCLs.
o The selected remedy for source piles and materials within the Plant is No Further
Action, because Monsanto's past cleanup actions, ongoing engineering and Institutional
Controls and compliance with federal and state (environmental and worker health and
safety) regulations have reduced potential sources of worker exposure and contaminant
migration to surrounding soils to acceptable levels under current industrial land use.
Five-year reviews will be necessary to evaluate land use, compliance status,
engineering and institutional controls (including worker health and safety programs and
dust control efforts) to ensure the remedy remains protective, since hazardous
substances remain on-Site above levels that allow for unrestricted use.
o The selected remedy for contaminated soils has multiple components:
For contaminated soils surrounding the Plant which are owned by a named
responsible party (to date, only Monsanto has been named), the selected
remedy is Institutional Controls in the form of land use restrictions placed in
deeds, and enforceable under an anticipated consent decree.
For contaminated soils on non-industrial property owned by individuals who have
not caused or contributed to the contamination at the Site (agricultural or
residential property owners) the selected remedy is an election by each such
property owner to have their property either: a) cleaned up via excavation,
containment and replacement of contaminated soils, or b) rendered protective of
human health and the environment via land use restrictions in the form of an
environmental easement to be held by a named responsible party. If
contaminated soils are excavated, they will be replaced with clean soil and the
contaminated soils will be contained within the Plant and covered with at least 12
inches of clean soil and vegetation (or some other protective cover) to minimize
potential human exposure to, or migration of, the contaminated soil.
Until the remedy is completed, unrestricted contaminated areas will be monitored to ensure that
49
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residential development does not occur without appropriate action being taken.
No action is necessary for the City Industrial Park property to the southeast of the Plant, which
has historically been and continues to be zoned and used by a cooperating government agency
(City of Soda Springs) for industrial purposes, and is expected to remain that way for the
foreseeable future.
To ensure that the Selected Remedy can be implemented fairly and in a reasonable timeframe,
if residential property owners elect (b) Institutional Controls, they must either:
1) Agree to self impose deed restriction Institutional Controls prohibiting residential use of
the affected property until EPA determines such use may be permissible, and enter into
a consent decree with EPA to make the Controls enforceable; or
2) Sell either their property or an environmental easement restricting residential
development rights for their property to a responsible party (Monsanto), thereby allowing
EPA to establish enforceable ICs in its anticipated consent decree with Monsanto. To
ensure fair terms for all concerned, such sales will be governed by an independent
arbitration process, to be paid for by Monsanto, at which the arbitrator would set a fair
selling price which could not be less than the fair market value of the property or
easement had the property not been contaminated by Monsanto operations. The
arbitration process and arbitrators selected pursuant to the RCRA AOC for SE Idaho
slag matters and issued to Monsanto and FMC Corporation in 1996, as described
above, will be used. i
If for any reason, any residential property owner(s) were to fail or refuse to make any election,
i.e., fail to elect either to have their property cleaned up, or to sell it or an environmental
easement over it, EPA will evaluate whether alternate cleanup or enforcement actions are
necessary.
o EPA's selected remedy for Air, Surface Water, and Soda Creek sediments is No
Further Action. No action is necessary in these areas because no significant human
health concerns or environmental impacts were found related to these media.
While not part of the selected remedy, the selected remedy was developed with the Plant in
compliance with pertinent environmental requirements and the assumption that such compliance would
continue. If air emissions were to exceed permitted levels, they could pose additional risks to human
health or the environment or allow unacceptable levels of contaminants to migrate to surrounding soils
at or near the Site which could require CERCLA action.
Future Plant Use
Despite potential risks in excess of the acceptable risk range for future industrial use (assuming EPA
default values and no ongoing institutional controls or worker health and safety programs), cleanup
alternatives were not developed for alternative future industrial scenarios within the Plant and no
remedy has been selected based on such scenarios because Monsanto is considered highly likely to
continue to operate the Plant for the foreseeable future. Monsanto has just increased production and
50
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maintains it has the reserves to profitably operate the Plant for over 30 more years.
Cost of the Selected Remedy
The estimated cost of the selected remedy over 30 years is between $2,500,000, if all contaminated
soils are addressed through institutional controls at the price estimated in the FS, to as much as
$9,500,000, if the full extent of contaminated soils above the remediation goal in potential residential
areas is remediated through excavation, soil replacement, and containment within the Plant. The
estimated cost of the Soil Institutional Control/ Groundwater Monitoring alternative in the FS was
$400,000 for initial capital costs of establishing institutional controls and up to $150,000/year for
groundwater monitoring, source/soil monitoring, and dust control, for a 30-year total of up to
$2,500,000. Since dust control is required pursuant to the Plant's IDAPA permit and is not part of the
selected remedy, that cost is not part of the cost of the remedy. However, the cost estimate still seems
reasonable, given that the cost of the arbitration which may be needed was not estimated in the FS.
The FS cost estimate for the active soil cleanup alternative was $16 million dollars, based on cleanup
of 435 acres to meet a 1x10"4 cleanup level. Current estimates of the total area to be addressed at the
selected 3x10"* cleanup level is 250 acres, of which some 25% are already owned by Monsanto. Thus
the maximum cost estimate for the soil remedy over 30 years if all soils outside Monsanto's control
require active remediation is an additional $7,000,000, for a total cost estimate of $9,500,000.
Remediation Goals and Points of Compliance:
GROUNDWATER
The selected remediation goals for groundwater are Maximum Contaminant Levels under the Safe
Drinking Water Act for cadmium, fluoride, nitrate, and selenium, and risk-based concentrations for
manganese (shown below). The points of compliance will include Soda Creek, monitoring wells TW-
19, 34, 35, 29, 53, 54, 55, the Harris well, and the three Plant production wells.
Table 6 - MCLs
Max Conc.ln Cone, at Southern Primary
Constituent Groundwater Plant Boundary (mg/L) MCL(mg/L)
Cd 7.92 0.005 0.005
F 19.93 5.0 4
NO, 45.0 45.0 44
Se 0.93 0.2 0.05
Mn 1.55 0.015 RBC = 0.18
SOILS
The selected remedy addresses all soils in off-Plant areas containing radionuclides that pose
cumulative estimated risks in excess of 3 x 10"* from residential exposure. At this Site, the 3x10"4 risk
goal corresponds to a radium-226 concentration in soils of 3.7pCi/g and a radiation effective dose
equivalent of approximately 15 mrem/year for the radionuclides of concern. To further reduce
51
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cumulative excess risk, in areas where the radionuclide soil cleanup goal is exceeded, the remedy also
requires that metals which exceed background and pose an excess carcinogenic risk greater than 10~5
(arsenic = 21 ug/l, beryllium = 8 ug/l) or a non-cancer HQ=1 or more (none found) be addressed.
As explained earlier in the RAO section, the FS evaluated a range of potential soil cleanup goals,
including 5x10"*, 1x10~* to 1x10*, and background. The selected remedy for this Site includes cleanup
of soils containing radionuclide concentrations which pose a risk of 3x1 Or* above background for
residential land use, including exposure from all potential pathways and media (using EPA's slope
factors and risk assessment methodology). The 3x1 Ou risk goal corresponds to a radium-226 soil
concentration of 3.7 pCi/g and a radiation effective dose equivalent of approximately 15 mrem/year for
the radionuclides of concern at this Site. This goal corresponds to the upper end of the range for
cancer risks considered protective at most Superfund sites. EPA may consider risk estimates slightly
greater than 1x10"* to be protective based on Site-specific conditions, including any remaining
uncertainties on the nature and extent of contamination and associated risks. For this Site, these Site-
specific conditions include the high naturally-occurring background concentrations of the radionuclides
of concern, the lack of a uniform distribution of the contaminants in soils, current land use, and
associated uncertainties.
The 3x1 O*4 risk goal for radionuclides is also consistent with levels considered protective in other
governmental actions including regulations and guidance developed by EPA in other radiation control
programs including: (1) EPA's Environmental Radiation Protection Standards for Management and
Disposal of Spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes (40 CFR 191) which
sets a dose limit of 15 mrem/year (equivalent to a risk of 3x10"4 over 30 years) and (2) EPA's National
Emission Standards for Hazardous Air Pollutants (40 CFR 61) which sets a standard for radionuclide
emissions from operating elemental phosphorus production facilities, including Monsanto Soda
Springs, equivalent to a risk of approximately 3x10**.
If owners of contaminated property elect cleanup via excavation, the area to be excavated shall be
determined based on the selected remediation goals, using RI/FS results supplemented by additional
sampling during remedial design. Excavations shall be perfomed to a minimum depth of 6 inches,
followed by confirmation sampling and if necessary additional excavation until cleanup goals are met.
Institutional controls must be established and maintained for all off-plant soil areas in excess of cleanup
goals which remain unrestricted and therefore could be developed for residential use (see Figure 7).
CERCLA Five-Year Review Requirements
Because this remedy will result in hazardous substances remaining on Site above health-based levels,
a review will be conducted within five years after commencement of remedial action to ensure that the
remedy continues to provide adequate protection of human health and the environment. The following
is a partial description of the reviews that will be required by media/area of the Site:
Groundwater.
• Review and assess groundwater and outfall monitoring data (which should be collected and
evaluated at least annually);
52
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• Compare groundwater and outfall quality and extent of contamination (plume(s)) to regulatory
levels, remediation goals and groundwater modeling projections. Determine if/when
remediation goals have been achieved, and if not, that Institutional Controls are still in place
and effectively preventing human exposure.
• If groundwater recovery appears to significantly differ from model projections, the model and
the need for additional groundwater remedial actions should be re-evaluated.
Soils Surrounding the Plant:
• Soil sampling should be done no less often than every five years to a) determine the
concentrations of COCs in soils, and b) verify that source control is effectively preventing
further spread of Site contaminants and/or recontamination of soils. Soil sampling should be
done from the current fence line out to the phase 2 soil sampling locations, until such time as
the Agencies determine that further sampling is not necessary.
• Review that Institutional Controls are in place for all soil grids surrounding the plant which
contain radium concentrations greater than the remediation goal of 3.7 pC/g, based on a
statistically valid sampling program.
Plant:
Verify that operations continue to be in compliance with environmental (CAA, IDAPA, CWA,
RCRA) and worker health and safety requirements so that potential releases and exposures
remain adequately controlled and the remedy remains effective;
Determine if closure has occurred or is planned, and if so, verify that any required/planned
closure procedures are protective;
Sediments:
Sediment samples should be collected to support the five year review assessment of whether
contaminant concentrations are remaining stable or declining as predicted. If sediment
concentrations instead are shown to be increasing or evidence of health impacts are identified,
the protectiveness of the remedy should be re-evaluated.
53
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.*f?:
•isn^v
^
V^
<3 < ^ jj Monsanto Superfund Site
AREAS THAT EXCEED
^ S3 SOIL REMEDIATION GOALS
Monsanto Plant Bound
Monsanto Chemical
Company
Jhll \ ":\W / Wv^y M. />Bn> f-S K !j » VC*^a!
l;\ M^9.17 I ! " MCO 1rt "~ -••-*—^' -A i'«/~~
•iI i¥io«-i^f ._ ', | x-^- M9£*lv K [ jffi\; ;• ^; ny / &
Area where Radium-226 concentrations
exceed the 3x10"4 target cleanup level of 3.7 pCi/g
Area boundary is inferred due to inadequate bounding data
or uncertainty of constituent(s) source(s)
The areas shown are based on analytical data
from soil samples collected from the 0-1" depth
interval.
Monsanto Site
AREAS THAT EXCEED
SOIL REMEDIATION GOALS
Figure 7
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10. STATUTORY DETERMINATIONS
Under CERCLA, EPA's primary responsibility is to ensure remedial actions are undertaken which
protect human health, welfare and the environment. In addition, Section 121 of CERCLA, 42 USC
9621, establishes cleanup standards which require that the selected remedial action complies with all
ARARs established under Federal and state environmental and facility siting law, unless such
requirements are waived by EPA in accordance with established criteria. The selected remedy must
also be cost-effective and must utilize permanent solutions, alternative treatment technologies, or
resource recovery technologies to the maximum extent practicable. Finally, CERCLA regulations
include a preference for remedies that employ treatment that permanently and significantly reduces the
volume, toxicity or mobility of hazardous waste. The following sections discuss how the selected
remedy for the Monsanto Site meets these CERCLA requirements.
Protection of Human Health and the Environment
The selected remedy is protective of human health and the environment, complies with Federal and
State requirements that are legally applicable or relevant and appropriate to the remedial action, and is
cost-effective. The remedy is protective of exposure to soils through the implementation of either
Institutional Controls or Excavation, replacement and disposal, in combination with soil sampling to
verify that sources have been controlled and soils are not further contaminated. The remedy is
protective of exposure to groundwater through implementation of Institutional Controls to ensure no
human exposure to contaminated groundwater plus a monitoring program to ensure that constituent
concentrations decline as predicted.
Compliance with Applicable or Relevant or Appropriate Requirements
The selected remedy will comply with all chemical-specific, action-specific, and location-specific
Federal and State requirements that have been identified and which are legally applicable or relevant
and appropriate to the remedial action. In addition, other regulations and guidance were considered in
the selection of remedy. No waiver of any ARAR is being sought or invoked for any part of the
selected remedy.
The ARARs identified for the Monsanto Site include the following:
For Groundwater, National Primary Drinking Water Standards (40 C.F.R. Part 141) are
relevant and appropriate to the selected remedy. These ARARs will be met by Natural
Attenuation and Institutional Controls. The Maximum Contaminant Levels that pertain to the
COCs at the Monsanto Site (there are no non-zero MCLGs that pertain) are as follows:
Primary
Constituent MCL(ma/Ll
Cd 0.005
F 4.0
NO3 44.0
Se 0.05
55
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Idaho Ground Water Standards (IDAPA Sec 16.01.02.299). Protects groundwater for
beneficial uses, along with Idaho Antldegradation Policy (IDAPA Sec. 16.01.02.051) which
requires that existing water uses and water quality be maintained and protected. These ARARs
will be met by Natural Attenuation (plus Institutional Controls until cleanup goals are met).
The following ARARs pertain in the event active soil remediation is elected or necessary:
Clean Air Act, 42 U.S.C. 7401 et seq.. (CAA), National Primary and Secondary Ambient
Air Quality Standards, 40 C.F.R. Part 50; CAA National Emissions Standards for
Hazardous Air Pollutants, 40 C.F.R. Part 60; CAA New Source Performance Standards, 40
C.F.R. Part 61. The CAA regulations are applicable for control of dust particles emitted into
the air during remedial excavation activities. In that event, fugitive dust control measures will be
required during any excavation and related remedial activities.
Amendment to the NCP, procedures for Planning and Implementing Off-Site Response
Actions, 40 C.F.R. 300.440. These rules and requirements are applicable to off-site
management of CERCLA hazardous substances, pollutants or contaminants resulting from the
ROD, in the event active soil remediation is performed and excavated material is taken off-Site
(which is not currently planned, but conceivably could occur). In that event, this ARAR will be
met by following the Off-site Rules.
Rules for Control of Fugitive Dust, IDAPA 16.01.01.650. This ARAR is relevant and
appropriate for the management of fugitive dust in the event active soil remediation is
performed. In that event, fugitive dust control measures will be required during excavation and
related remedial activities.
Environmental Protection and Health Act, Idaho Code 39-101 to 129. Authorizes rules to
protect the environment and human health and safety through state oversight of solid waste
disposal and state approval of disposal locations and design. This requirement is relevant and
appropriate for the disposal within the Plant of soils excavated from surrounding properties in
the event active soil remediation is performed. In that event, the substantive portion of these
rules will be addressed in the design of the soil containment area.
The policy, guidance, and regulations which are not ARARs but were nevertheless considered in the
selection of the remedy, or which impact the remedy include the following:
Occupational Safety and Health Act(OSHA), 29 U.S.C. 651; the implementing regulations
under OSHA, 20 C.F.R. Parts 1910 and 1926. These regulations must be complied with during
all remedial activities.
Cost-Effectiveness
EPA has determined that the combination of remedial actions identified in the selected remedy will
reduce or eliminate the risks to human health in a cost-effective manner. The costs associated with
the selected remedy and cleanup level are significantly less than the cost of active cleanup of all areas.
The selected remedy is cost-effective because it provides overall effectiveness proportional to its costs
56
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Utilization of Permanent Solutions and Resource Recovery Technologies to the Maximum
Extent Practicable
The selected remedy utilizes permanent solutions and alternative treatment (or resource recovery)
technologies to the maximum extent practicable for this Site.
Preference for Treatment as a Principal Element
The selected remedy utilizes alternative treatment (or resource recovery) technologies to the maximum
extent practicable for this Site. However, because no principal threats remain and treatment of the
remaining threats of the Site was not found to be practicable, the selected remedy does not satisfy the
statutory preference for treatment as a principal element.
Because this remedy will result in hazardous substances remaining on-Site above health-based levels,
a review will be conducted within five years after commencement of remedial action to ensure that the
remedy continues to provide adequate protection of human health and the environment.
11. DOCUMENTATION OF SIGNIFICANT CHANGES
The selected remedy is a logical outgrowth of the preferred alternative in the proposed plan, and it
includes the same basic components. In response to comments, however, for soils surrounding the
Plant, EPA has elevated excavation and disposal of soils to parity with Institutional Controls, making
excavation and disposal an option for affected agricultural and residential landowners who expressed a
desire for cleanup, rather than merely a contingency following an effort to establish such Controls. The
types of enforceable Institutional Controls that could be used have been developed further than they
had been in the FS. The process for implementing purchase of property or easements to establish
Institutional Controls has been modified by the addition of the arbitration process to make sure that a
fair transaction will occur.
The "Contingency Plan" concept described in the Proposed Plan has been eliminated in favor of the
selected remedy because the "Contingency Plan" was seen as too uncertain and likely to encourage
property speculation rather than the CERCLA goal of elimination of exposure pathways.
Based on comments and concerns about the feasibility and implementability of in-situ bioremediation at
this Site, the selected remedy calls for excavation as the preferred means of soil cleanup, if any such
cleanup is required. The Plan had identified bioremediation as the most favorable treatment option. If
soil cleanup is required and the responsible parties can demonstrate an effective treatment method
that will satisfy the ROD requirements and the affected landowners, this remedy may be reconsidered.
The selected remedy for groundwater is described in this ROD as "Monitored Natural Attenuation with
Institutional Controls", rather than "Institutional Controls with No Further Action because past actions
plus natural attenuation appears effective" as stated in the Proposed Plan. This modified description
does not pose any additional requirements beyond those contemplated in the FS/Proposed Plan, but is
more accurate and more consistent with national guidance and other Superfund site decisions.
57
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Page deliberately left blank
58
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RESPONSIVENESS SUMMARY
Section 3 of the
RECORD OF DECISION
Monsanto Chemical Company Superfund Site
Caribou County, Idaho
April 1997
59
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page deliberately left blank
60
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RESPONSIVENESS SUMMARY
At the Monsanto Site, EPA has met all requirements of CERCLA Section 117 and the NCP for public
participation at NPL sites.
In accordance with CERCLA Section 117 requirements, once the RI/FS was complete EPA issued a
Proposed Plan, which provided information on the alternatives considered and identified the preferred
remedial alternative, for a 30-day public comment period. The start of the comment period was
announced in a Public Notice placed in the Caribou County Sun and a fact sheet which was mailed out
to the entire mailing list along with the Proposed Plan. Both the Caribou County Sun and the Idaho
Statesman ran articles describing the proposed plan and announcing the public comment period.
Owners of property adjacent to the Monsanto Plant were sent the Proposed Plan with a cover letter
which pointed out that they or their property could be affected by the Proposed Plan, and which urged
them to review the plan and to provide comments.
On August 13, 1996, EPA held a Public Meeting to describe the Proposed Plan and take formal public
comments. The meeting was transcribed by a court reporter and all comments received are addressed
in the Responsiveness Summary.
On August 21,1996, EPA received a letter from the Mayor of Soda Springs requesting a 30-day
extension of the public comment period in order to give the Mayor, local officials and residents more
time to review the plan and provide comments. In response, EPA extended the public comment period
by 30 days, until September 30, 1996. The Mayor and the City of Soda Springs did not provide further
comments.
All comments/questions received at the public meeting and during the 60-day public comment period
have been summarized and addressed below.
Monsanto Proposed Plan Public Meeting -Soda Springs Idaho, 8/13/96
Approximately 35-40 people attended the meeting, including about 10 local property owners, reporters
from Caribou County Sun & Idaho State journal, Monsanto representatives (Robert Geddes, Kent Lott,
Gordon Allend, Pat Hyland, Dale Wilson, Dean Pahl (Montgomery Watson), Wright (MW)), 2 FMC
representatives, Gordon Brown of DEQ, and Steve Haness of ATSDR.
Misha Vakoc of EPA moderated the meeting; Bob Geddes and Dean Pahl presented the Rl and FS
findings & an invitation from Monsanto to give local residents additional information; Tim Brincefield,
EPA Project Manager, summarized the results of the Risk Assessment, the preliminary decisions made
in scoping the FS, and the Proposed Plan for remedial action. EPA then invited comments and
questions from the audience.
Summary of Written Comments/Questions Received and EPA Responses:
Q. One commenter wrote and supported the proposed plan, but suggested that EPA should
give consideration to the suggestion that cleanup only be done if land use changes.
A. EPA evaluated that option but was unable to identify a reliable, enforceable means of
implementing it. That suggestion also would have delayed completion of the remedial action
61
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indefinitely, which is contrary to Agency and public desire to resolve Site issues as expeditiously
as possible.
Q. The City of Soda Springs wrote and asked for an extension of the comment period from
30 to 60 days.
A. That request was granted, and the comment period lasted until September 30, 1996..
Q. Several comments were received from local property owners. Those who commented
supported action to address the contamination surrounding the Plant, but did not
support any future restrictions on use of the surrounding property. Therefore, these
commenters recommended implementation of the excavation and on-Plant disposal
option.
A. These comments were considered and the Agency believes the selected remedy addresses
those concerns.
Q. One of the local property owners also suggested that EPA had underestimated risks to
farmers farming affected areas, and that risks to farmers would be higher than risks to
workers.
A. EPA did not initially quantitatively estimate risks from farming, rather EPA assumed that farming
exposures would be of such an intermittent nature that industrial exposures would be similar or
higher, and therefore if the soils are safe for industrial use, they should be safe for farming as
well. Subsequently, EPA further evaluated potential carcinogenic and non-cancer risks to
agricultural workers laboring near the Monsanto Plant. The conclusion of that evaluation was
that excess lifetime cancer risks associated with exposure to radionuclides are similar to the
industrial risk estimates and about one third as high in the agricultural worker scenario as in the
residential scenario; risks associated with ingestion and inhalation of metals are also similar to
the industrial risk estimates and about one fifth as high in the agricultural worker scenario as in
the residential scenario. Therefore, EPA believes the selected remedy and remediation goals
are protective of agricultural workers.
Q. One commenter suggested that institutional controls were adequately protective and
that there is no need for a contingency remedy. If necessary, cleanup could be
undertaken if land use around the Plant ever changed to residential.
A. See first response on this page.
Q. One commenter suggested that the contingency remedy for soils should be any form of
treatment that would work, not just bioremediation.
A. EPA would accept substitution of a more-promising treatment alternative for bioremediation if
one can be identified. Ultimately, however, treatment was not selected due to the technical
uncertainties and community concerns.
Q: What risks are residents facing? What is the magnitude of the risk and how does it
compare to other risks?
A: EPA assessed potential risks to human health and the environment posed by radionuclides and
62
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metals found at the Site. Risks were evaluated for several possible exposures including, for
example, ingestion and inhalation of contaminated soil, ingestion of contaminated ground water,
and impacts to Plants and animals. There are no significant risks to workers or residents under
current conditions. However, if residences were built in the most contaminated areas near the
Plant fence, the potential excess lifetime cancer risks would be unacceptably high (>1 x 10'3); if
contaminated groundwater south of (or beneath) the Plant were used for drinking water, risks
would also be unaceptably high (no one is currently known to drink the contaminated
groundwater).
Superfund law defines an acceptable range of human health risk from hazardous contamination
as a 1-in-10,000 to 1-in-1,000,000 lifetime risk of cancer. This means that if a group of 10,000
to 1,000,000 people were exposed to a potential cancer causing situation over a 70 year
lifetime, just one additional person would be expected to develop cancer beyond those
expected from other causes. Risk above this range from contamination at a Site (i.e., more
than a 1 in 10,000 risk of cancer) typically requires some type of cleanup or preventative action.
Note that soils around the Plant are not more contaminated than soils and sources within the
Plant; rather, the assumption of residential use (people spend more time there on a given day)
results in a higher risk estimate.
Q: Several commenters asked whether EPA evaluated County zoning/land use ordinances
to see if such ordinances were sufficient restrictions on soils to protect against potential
exposure.
A: EPA considered those, however they are subject to change without State or EPA input, and are
not enforceable by either. Therefore, EPA guidance recommends the use of enforceable
easements or covenants as Institutional Controls. At many sites deed restrictions or other
means have typically been used. Local ordinances are being relied on at the Bunker Hill Site in
Northern Idaho, but the costs and administrative burden of the process established there to
deal with the many affected properties in the Silver Valley appear high relative to the
circumstances at the Monsanto Site.
»'
Q: EPA was asked whether EPA considered only taking/requiring action if development
actually were to take place, instead of doing so immediately.
A: EPA considered that, and it would be possible, but as discussed above, it could delay
completion of the remedial action indefinitely and otherwise be difficult to enforce, thus it was
not selected. At most sites where cleanup has been put off until or unless the land is
disturbed/developed (other than Bunker Hill), EPA has still required that there be some form of
deed restriction in addition to the local ordinance. In this case, such a notice might describe or
show the affected area(s) and state that they must be remediated if/when developed for
residential purposes. To make this work, we would need to identify someone (at Bunker Hill,
the local Health Department) to be responsible for overseeing the process and someone (likely
Monsanto) to pay for the work.
Q: Some asked whether EPA could or would compel landowners to clean up their land.
A: That question does not have a single, simple answer. Under the law, owners of contaminated
property may be potentially responsible for the cost of investigation and cleanup of Superfund
sites. That provision was designed to "make polluters pay"; therefore, under the law, adjacent
63
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property owners could be potentially responsible parties. However, EPA has some discretion
and looks at the facts in each and every case. In this case EPA has only named one potentially
responsible party (Monsanto) to date, since they are apparently the sole source of the
contamination. EPA has no information at this time to support naming additional potentially
responsible parties. EPA does hope that property owners will do what they can to help make
the selected action happen, such as providing access for cleanup to occur or agreeing to sell
the property development rights to Monsanto, who in turn would preclude any residential
development of the affected area(s).
Q: One questioner asked whether EPA could condemn affected property or compel owners
to restrict/clean up their property.
A: Under certain circumstances, EPA could issue a unilateral Administrative Order to compel a
landowner to allow EPA access to perform actions necessary to protect human health or the
environment. At this Site, since owners have been given a choice between Institutional
Controls and excavation, EPA does not anticipate having to compel anyone to comply.
Q. EPA was asked what it thought was "reasonable time frame" it was considering for the
soils contingency described in the Proposed Plan.
A: EPA had been thinking in terms of about 1 year from the date the ROD is completed, however
EPA deliberately left the time frame out of the proposed remedy in order to retain some
discretion to adjust to changing circumstances that might affect the time to complete
Institutional Controls. Ultimately, EPA's selected remedy gives property owners six months to
elect excavation or Institutional Controls.
64
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Appendix A
Additional Figures and Tables
RECORD OF DECISION
for the
Monsanto Chemical Company Super-fund Site
Caribou County, Idaho
April 1997
-------
Table A-1
Identification of Chemicals of Potential Concern in Ground Water
Analyte
Aluminum'
Arsenic
Beryllium
iJiafaiBM M~i •'<
Calcium
Chloride
Chromium (total)
Copper
Bfuorfdef '-' ";
Iron
Lead
Magnesium
Manganese
Mc&Ixtenum
Nickel
Nitrate as N
Potassium
i&teB&HB '*-*>'<''''*,
Silver
Sulfate Ion
Vanadium
Zinc
RADIONUCLIDES
Radium-226+D
Radium-228+D
Radon-222
Uranium-238+D
Maximum
Concentration'
0.1S8
0.0016
ND
0.0042
235
166
NE
NE
5.5
0.594
NE
133
0.05
0.126
0.01
12.2
16
0:472
NE
478
0.018
0.216
NE
NE
ME
NE
Maximum
Background
Concentration1"
MCL
MCLG
Human Health
RBC*
(mg/L)
;!^&t£-^i
0.002
ND
*"•&»%*&
, „»:-'; =
/ :\^25-^T;
W3&>.^^
K-«*: v*
:..- ii$&te>>$*\
^g&o""^?}
'^ fciDx-",,-^
:\~j&&$^
•.*"&$&£&*$' 'ti
•..rs^ws^
'"£' J(£8&:4}%
t'M§8&i%
0.05
0.004
0.005
—
250"
?" >^, w
f ef
—
— '
'
,r/,v*&' ^^v
—
^'""\250?;- *-
—
5°
^^^Ef^5b,
0.004
0.005
—
—
-. •. M •••:•. Jlfrt *• .. .
<.' tTv
—
' —
. _ .
—
- "x'A'W) ,"',
tfff fSffJ_
~
2.6E-02
7.3E-01
Shading indicates maximum detected concentration exceeds column values; shading in the Analyte column indicates a COPC.
a = Ground water wells evaluated include: Harris. Lewis. TW -53, 54,55. These wells would represent ground water potentially
available in a future residential scenario.
b = Based on Wells TW-57, TW-29, TW-15 from November 1992 and May 1993 sampling records.
c = RBC based on residential default exposure parameters.
d = Secondary MCL
e = Aluminum is not retained because SMCL is below background, and max is less dun RBC
f = Proposed
ND = Not detected
NE = Not evaluated; dropped as a COPC during Phase I or early Phase n risk screening analysis.
A-1
-------
Table A-2
Identification of Chemicals of Potential Concern in Soil
Analyte
Maximum
Concentrations
Background
Maximum I UTL*
Noncancer RBCsb
HQ=0.1
Carcinogenic
RBCsb
RiskslF-07
(mg/kg)
Aluminum
30200"
34.0
8.2
4.0
168
Chromium Total
325
27.000°
Copper
42
1,000
Fluoride0
136.0
1.600
Iron
55,500
Lead
68
81
NC
Manganese
1380
3.800
Molybdenum
2.9
140
Nickel
87.3
550
Nitrate as N
47
44.000
Seleniumd
109
140
Silver
13.0
140
Uranium6
5.3
90
Vaflaft'uro
467
Zinc
2.670
8.200
RADIONUCLIDES
(pCi/g)
65
Polonium-210
77
Potassium-40
19
20
NC
7.7E-03
17
Radium-228-t-D
1.4
1.7
NC
1.4E-03
Thorium-228+D
1.6
1.7
7.4E-04
18
Thorium-232
1.6
1.7
NC
6.4E+00
16
Shading indicates maximum detected concentration exceeds column values; shading in the Analyte column indicates a
COPC.
a = Log normal conversion before UTL calculation.
b = Based on residential default exposure parameters.
c = Site Fluoride concentrations based on soluble fraction only.
d = Limited data set.
e = Uranium concentration converted from measured activity of U-238 by multiplying by 0.331.
f = Polonium-210 not retained because it is considered in tead-210+D chain.
g = Chromium III RBC
h = Outlier thrown out before treatment of data set
NC = Not calculated.
A-2
-------
Table A-3
Identification of Chemicals of Potential Concern in Source Materials
Analyte
Aluminum
Arse01c> J <
Seryifium ' " -^
Cadmium'^ " "C •'
Chromium (Total)
Copper
Fluoridec * -
Iron
Lead
Manganese
Molybdenum
Nickel
Nitrate as N
Selenium*1
Silver
Uranium6
Vanadium
Zinc
RADIONUCLIDES
Lead-21Q*D
Polonium-210f
Potassium-40
JRaaiun>22fefD "^
Radium-228+D
Thorium-228+D
3$0fr&iiv2|fev';;/./
Thorium-232
Uraniun>238+Q -,
Maximum
Concentrations
Background
Concentration
Maximum
UTL8
Noncancer RBCs9
HQ=0.1
Carcinogenic
RBCs9
Risk=1E-07
(mg/kg)
27,700
500
60.1
2,070
30.500
86.9
14.500
12,200
200
899
893
170
79
231
94
15.6
65,100
54.200
V,i&30G<
ft^&4^
t^T&X,
^ajr-rss
-'2W'O
me ' -
,, 66,1 *
23.000
81
690 -
/"l<7 '
fl 53 '; '
", , 13 /
"'="' 0,4
,d
; o:§ -
' -42 ,
'*";"i3&.,-<
*&&&?<
f^€H^;
-M&JB r-
&&& '2*
'• ';&£'<-'
23,1'
n.e -
NC
NC
607
1.6 '
NC
NC
NC
NC
NC
,36.D ,
' 112.6
200,000
,!'/ '8^'K^
1.000
^^''IPO'L' '1
200,000"
7,600
.'12,000
—
—
29,000
1.000
4.100
330.000
1.000
1,000
6700
4,400 ;.
61,000
—
j^i;3.3£4tt
|ll||;iM.3£-#1
—
—
—
—
-
.—
-
—
• —
-
—
-
—
-
(pCi/g)
390
260
11
54
1.0
0.9
430
4.8
48
:*,j&2-'/-
•;;'*#'•'•*
20
^^StlTs ''
1.7
1.6
¥•$&*- '•
'"''"'* *
"',;',',',*&„/
, .v40 ;
'-*$»?
(NC)
"? '^9 "
(NC)
1.7
/ff* ** v*ifef£ &' -5- 'A
(NC)
'-...:~M'.,. '.-..
—
—
—
. —
—
— •
—
—
-
X'/'4*&01
- & a,ie+oo'
4.0E-02
*-, r,%jB&
-------
o 1000
SCALE IN FEET
/ O
MS2-U
WEST
11
•
O MSM •
\ MS2-2
x o .
1
J
NORTH >• ........... V
MS228O
, / Ore ;
/ Siockpae .-•<
: X
'•---'" Quartils
..--"" MS2-9 • \
'• MS2-16 'O/^I ITU
\ O •«« MSMOO /SOUTH
MS2-2*.
MS2-29
LESffiD
• Oisade Air Receptor
' 'Locations
O SoJ Samples
ENVIRONMENTAL SAMPLES USED IN CURRENT RESIDENTIAL SCENARIOS
-------
NORTH II
NORTH I
0 1000
SCALE IN FEET
SOUTH
"iSOUTHI
IfSBffl
O Sod Samples
A Wal»Sampte
• Air-Modeled Valua
ENV1RONME^^•AL SAMPLES USED IN FUTURE RESIDENTIAL SCENARIOS
-------
Appendix B
Administrative Record Index
RECORD OF DECISION
for the
Monsanto Chemical Company Superfund Site
Caribou County, Idaho
April 1997
-------
TABLE OF CONTENTS
MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD (MONAR)
May 2,1997
0. 0 TABLE OF CONTENTS / INDEX
1. 0 SITE IDENTIFICATION
1. 1 Correspondence
1. 2 Background
1. 2. 1 Summary of Activities and Remedial Efforts
1. 3 Notification / Site Discovery / CERCLIS
1. 4 Preliminary Assessment Data / Report
1. 5 Work Plans
1 6 Site Inspection Reports / Documents
1. 7 Sampling and Analysis Data
1. 8 Hydrogeological Investigation - Colder Report, Volume 1 (2 Volumes)
2. 0 REMEDIAL INVESTIGATION / FEASIBILITY STUDY (RI/FS)
2. 1 Correspondence
2. 2 Statement of Work / Work Plan
2. 3 Sampling Data
»•
2. 4 QA/QC Plans
2. 5 RI/FS Reports (8 Volumes)
2. 6 Risk Assessments
2. 7 Proposed Plan
3. 0 RECORD OF DECISION
3. 1 Memo to File
4. 0 STATE COORDINATION
4. 1 Correspondence
5. 0 ENFORCEMENT
5. 1 Correspondence
Page 1
-------
TABLE OF CONTENTS
MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD (MONAR)
May 2,1997
5. 2 Notice Letters and Responses
5. 3 Good Faith Proposals
5. 4 Administrative Orders
6. 0 HEALTH ASSESSMENTS
6. 1 Correspondence / Comments
6. 2 Health Assessments
7. 0 NATURAL RESOURCE TRUSTEES
7. 1 Correspondence
8. 0 CONGRESSIONAL INQUIRIES
8. 1 Correspondence
9. 0 PUBLIC PARTICIPATION
9. 1 Correspondence
9. 2 Newspaper / Journal Articles
9. 3 Community Relations Plan
9. 4 Fact Sheets / Press Releases
9. 5 Meeting Transcripts
10. 0 TECHNICAL SOURCES AND GUIDANCE DOCUMENTS
10. 1 EPA Guidance
10. 2 Technical Sources
Page 2
-------
(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
HEADING: 0. 0. . . TABLE OF CONTENTS / INDEX
5/2/97 US Fnvlrnnmontal Protection Ananr-w Oanlnn
-------
(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
HEADING: 1. 0. . . SITE IDENTIFICATION
SUB-HEAD: 1. 1. . . Vol.1 - Correspondence
1. 1. . . Vol. 1 - 000001 DOC ID: 6235
DATE: 12/13/79 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Daryl F. Koch/IDHW Howard L Burkhardt/SolkJ Waste Management
DESCRIPTION: Future Monsanto Hazardous Waste Visit
1.1... Vol.1- 000002 DOC ID: 6236
DATE: 9/3/80 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Tobias A. Hegdahl/EPA Gordon A. Aland/Monsanto
DESCRIPTION: Applicability of the EPA Hazardous Waste Regulations.
1.1... Vol.1- 000003 DOC ID: 6237
DATE: 6/4/81 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Michael R. Foresman/Monsanto EPA
DESCRIPTION: Transmits Notification of Hazardous Waste Site.
1. 1. . . Vol.1 - 000004 DOC ID: 6238
DATE: 6/4/81 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Kenneth D. Feigner/EPA D. W. Haines/Monsanto
DESCRIPTION: Facility #IDDO81830994; clarification of mining wastes excluded by statute.
1. 1. . . Vol.1 - 000005 DOC ID: 6239
DATE: 9/10/81 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
D. W. Haines/Monsanto Kenneth D. Feigner/EPA
DESCRIPTION: EPA ID # IDDO81820994, Withdrawal of RCRA Interim Status.
1. 1. . . Vol.1 - 000006 DOC ID: 6240
DATE: 9/21/81 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Kenneth D. Feigner/EPA D. W. Haines/Monsanto
DESCRIPTION: Returning Notification form and Part A permit application.
1.1... Vol.1- 000007 D6CID: 6241** &
DATE: 8/12/83 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Al Murrey/Idaho Dept of Health & Welfare Unknown Re/Unknown
DESCRIPTION: Fluoride Contamination Near Monsanto.
1.1. . . Vol.1- 000008 DOC ID: 6242
DATE: 12/20/83 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Michael A. Pierte/Monsanto Julie Sears/EPA
DESCRIPTION: Letter requests that EPA provide information from the FIT program pertaining to Monsanto
locations.
1. 1. . . Vol.1 - 000009 DOC ID: 6243
DATE: 2/10/84 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Deborah Flood/EPA Michael A. Piehe/Monsanto
5/ 2/97 U.S. Environmental Protection Agency, Region 10 Page
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(MDNAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
DESCRIPTION: Status of three Monsanto sites on the Region 10 ERRIS list
1. 1. . . Vol.1 - 000010 DOC ID: 6244
DATE: 3/4/87 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
David A. Buecker/Ecology & Environment. Inc. Kent V. Lott/Monsanto
DESCRIPTION: Notification of impending site inspection of Monsanto Co., Soda Springs.
1. 1. . . Vol.1 - 000011 DOC ID: 6245
DATE: 3/23/87 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
T. S. Oliver/Monsanto Jeff Whidden/Ecology & Environment, Inc.
DESCRIPTION: Transmits preliminary information regarding a site inspection on 3/23/87 and asserts a claim of
confidentiality on all aspects of the inspection.
1. 1. . . Vol.1 - 000012 DOC ID: 6246
DATE: 4/10/87 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Jeff Whidden/Ecology & Environment, Inc. John E. Osborn/EPA
DESCRIPTION: Trip Report, Monsanto Chemical Co., Soda Springs, Idaho.
1. 1. . . Vol.1 - 000013 DOC ID: 6247
DATE: 7/23/87 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
William J. Glasser/EPA J. P. Hyland/Monsanto
DESCRIPTION: Arrangement for meeting on July 20,1987.
1. 1. . . Vol.1 - 000014 DOC ID: 6248
DATE: 7/29/87 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
William J. Glasser/EPA Lee Godfree/Soda Springs Water DepL
DESCRIPTION: Transmits list of substances found in a water sample from Ledge Creek Springs taken 7/29/87.
1. 1. . . Vol.1 - 000015 DOC ID: 6249
DATE: 8/4/87 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
William J. Glasser/EPA Richard Torgesen/Unknown
DESCRIPTION: Transmits list of substances found in a sample from Torgesen's drinking water well taken 8/4/87.
1. 1. . . Vol.1 - 000016 DOC ID: 6250
DATE: 8/15/87 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
William J. Glasser/EPA Mr. A. Van Degriff/Unknbwn
DESCRIPTION: Transmits list of substances found in a sample of water from the Van Degriff s drinking water well
taken 8/4/87.
1. 1. . . Vol.1 - 000017 DOC ID: 6251
DATE: 8/15/87 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
William J. Glasser/EPA Ray Nelson/Unknown
DESCRIPTION: Transmits list of substances found in a sample of water from the Nelson drinking water well taken
8/4/87.
1. 1. . . Vol.1 - 000018 DOC ID: 6252
DATE: 9/9/87 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Jeff Whidden/Ecology & Environment, Inc. John E. Osborn/EPA
5/P/Q7 'IS Fn\Amnmantat Ornt
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
DESCRIPTION: Proposed Reid Operations, Work Plan Elements, Monsanto Chemical Co., Soda Springs, Idaho.
1. 1. . . Vol.1 - 000019 DOC ID: 6253
DATE: 9/25/87 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
William J. Glasser/EPA Robert L Geddes/Monsanto
DESCRIPTION: Transmits a copy of the Reid Operations Work Plan for the Monsanto facility in Soda Springs,
Idaho.
1. 1. . . Vol.1 - 000020 DOC ID: 6254
DATE: 10/16/87 PAGES: 6
AUTHOR(S): ADDRESSEE(S):
R. L. Geddes/Monsanto William J. Glasser/EPA
DESCRIPTION: Discussion of Reid Operations Workplan visit.
1. 1. . . Vol.1 - 000021 DOC ID: 6255
DATE: 1/22/88 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Robert L. Geddes/Monsanto Henry Elsen/EPA
DESCRIPTION: Requests the opportunity to comment on the drafting of the report which will be submitted by
Ecology and Environment, Inc. as a result of the CERCLA inspection at the Soda Springs plant
1.1. . . Vol.1 - 000022 DOC ID: 6256
DATE: 2/5/88 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
William J. Glasser/EPA Robert L Geddes/Monsanto
DESCRIPTION: Response to 1/22/88 letter states that draft reports are not required to be released under FOIA.
Welcomes comments on the completed site inspection report
1. 1. . . Vol.1 - 000023 DOC ID: 6257
DATE: 6/15/88 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
William J. Glasser/EPA Robert L. Geddes/Monsanto
DESCRIPTION: Transmits a copy of the site inspection report prepared by Ecology and Environment, Inc.
1. 1. . . Vol.1 - 000024 DOC ID: 6258
DATE: 6/20/88 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Stephan Krchma/Monsanto Theodore R. Rogowski/EPA
DESCRIPTION: Requests pages 26 and 27 of the Site Inspection Report for Monsanto Chemical Co., Soda
Springs, Idaho. ;^.gg
- "•*»{•
1. 1. . . Vol.1 - 000025 1^6 ID: 6259
DATE: 11/18/88 PAGES: 1
AUTHOR(S): :$ ADDRESSEE(S):
William J. Glasser/EPA $ Robert L. Geddes/Monsanto
DESCRIPTION: Transmits final draft of the* site inspection report and thanks Monsanto for their comments.
1. 1. . . Vol.1 - 000026 DOC ID: 6260
DATE: 11/30/88 PAGES: 2
AirTHOR(S): ;i ADDRESSEE(S):
William J. Glasser/EPA ^. Sharon Harris/Unknown
DESCRIPTION: Transmits list of substances detected in a sample of the Harris drinking water well taken 11/3/88.
1. 1. . . Vol.1 - 000027 DOC ID: 6261
DATE: 7/10/89 PAGES: 1
AUTHOR(S): ,-* ADDRESSEE(S):
'
5/ 2/97 U.S. Environmental Protection Agency, Region 1 0 Page
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
David M. Bennett/EPA Bill Smith/State of Idaho
DESCRIPTION: Requests a copy of all groundwater analyses, sampling protocol chaln-of-custody forms, method of
analysis and QA documents from groundwater sampled In the vicinity of Monsanto and
Kerr-McGee.
1. 1. . . Vol.1 - 000028 DOC ID: 6262
DATE: 10/20/89 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Kent V. Lott/Monsanto Robie G. Russell/EPA
DESCRIPTION: Requests a meeting to discuss the proposed NPL listing.
1. 1. . . Vol.1 - 000029 DOC ID: 6263
DATE: 11/15/89 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Robie G. Russell/EPA Kent V. Lott/Monsanto
DESCRIPTION: Sets up a meeting for 11/30/89 and provides some guidelines to be followed in the conduct of the
meeting.
1. 1. . . Vol.1 - 000035 DOC ID: 6269
DATE: 1/10/90 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
David M. Bennett/EPA Bob Myers/EPA
DESCRIPTION: Transmits transcript of a meeting held 11/30/89 between EPA and Monsanto.
1.1. . . Vol.1 - 000030 DOC ID: 6264
DATE: 1/23/90 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Robert L. Geddes/Monsanto Hank Habicht/EPA
DESCRIPTION: Response to proposal of Soda Springs site for NPL listing.
1. 1. . . Vol.1 - 000031 DOC ID: 6265
DATE: 2/26/90 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Don R. Clay/EPA Robert L. Geddes/Monsanto
DESCRIPTION: Response to Geddes 1/23/90 letter regarding concern over proposed listing of the site.
1.1. . . Vol.1 - 000032 DOC ID: 6266 .
DATE: 3/21/90 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
H. J. Corbett/Monsanto Don R. Clay/EPA
DESCRIPTION: Response to proposed listing of the Soda Springs plant on the NPL.
1. 1. . . Vol.1 - 000033 DOC ID: 6267
DATE: 6/11/90 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Don R. Clay/EPA H. J. Corbett/Monsanto
DESCRIPTION: Response to 3/21/90 letter regarding proposed listing of the Soda Springs plant on the NPL.
1. 1. . . Vol.1 - 000034 DOC ID: 6268
DATE: 6/25/90 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Walter W. Kovalick/EPA Larry G. Reed/EPA
DESCRIPTION: Record of 6/19/90 meeting with Mort Mullins and Mike Pierle of Monsanto for HRS/NPL Dockets.
SUB-HEAD: 1. 2. . . Vol.1 - Background
5/2/97 1'S Fnwirnnrnpntal Prntortinn Anonrv Ron Inn in
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
1.2. . . Vol.1 - 000001 DOC ID: 6270
DATE: 1/1/86 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Idaho Central Tumor Registry Unknown
DESCRIPTION: Cancer in Idaho by County, Age-Adjusted Incidence per 100,000 (AAI), 10 Year Average, 1977-66
In Rank Order.
1. 2. . . Vol.1 - 000002 DOC ID: 6271
DATE: 6/11/88 PAGES: 50
AUTHOR(S): ADDRESSEE(S):
D. R. Wind/Monsanto John Davis/EPA
DESCRIPTION: Transmits a set of thirteen EPA Form R's comprising the 1987 SARA Tide III, Sect 313 report
package for Soda Springs.
SUB-HEAD: 1. 2. 1. . Vol.1 - Summary of Activities and Remedial Efforts
1. 2. 1. . Vol.1- 000001 DOC ID: 6272
DATE: 1/1/89 PAGES: 10
AUTHOR(S): ADDRESSEE(S):
Monsanto Unknown
DESCRIPTION: Summary of Activities and Remedial Efforts, Monsanto Chemical Co., Soda Springs, Idaho.
SUB-HEAD: 1. 3. . . Vol.1 - Notification / Site Discovery / CERCLIS
1. 3. . . Vol.1 - 000001 DOC ID: 6273
DATE: 3/26/80 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Rogelio C. Fuentes/EPA Unknown
DESCRIPTION: Potential Hazardous Waste Site, Final Strategy Determination, Monsanto Phosphate Plant, Soda
Springs.
1. 3. . . Vol.1 - 000002 DOC ID: 6274
DATE: 4/3/80 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Judith Fey/EPA Unknown
DESCRIPTION: Potential Hazardous Waste Site Log, Monsanto Co.
1. 3. . . Vol.1 - 000003 DOC ID: 6275
DATE: 5/20/81 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
D. W. Haines/EPA Unknown
DESCRIPTION: Notification of Hazardous Waste Site, Federal Register, 4/15/81.
1. 3. . . Vol.1- 000004 DOC ID: 6276
DATE: 1/9/86 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
William H. Freutel/EPA Unknown
DESCRIPTION: Potential Hazardous Waste Site Disposition, Monsanto Soda Springs.
1. 3. . . Vol.1- 000005 DOC ID: 6277
DATE: 6/16/88 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
William J. Glasser/EPA Unknown
DESCRIPTION: Potential Hazardous Waste Site Disposition, Monsanto.
SUB-HEAD: 1.4. . . Vol. 1 - Preliminary Assessment Data / Report
5/ 2/97 U.S. Environmental Protection Agency, Region 10 Page 6
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
1.4... Vol. 1 - 000001 DOC ID: 6278
DATE: 12/19/79 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Daryl F. Koch/EPA Unknown
DESCRIPTION: Potential Hazardous Waste Site, Identification and Preliminary Assessment, Monsanto Soda
Springs.
1. 4. . . Vol.1- 000002 DOC ID: 6279
DATE: 12/23/85 PAGES: 9
AUTHOR(S): ADDRESSEE(S):
Bradley Hair/State of Idaho Deborah Flood/EPA
DESCRIPTION: Potential Hazardous Waste Site Preliminary Assessment, Monsanto Soda Springs.
1. 4. . . Vol.1 - 000003 DOC ID: 6280
DATE: 4/12/90 PAGES: 12
AUTHOR(S): ADDRESSEE(S):
William H. Longston/EPA Unknown
DESCRIPTION: Emergency Response Team, Final Site Review/Determination Form, Monsanto Soda Springs.
SUB-HEAD: 1. 5. . . Vol.1 - Work Plans
1. 5. . . Vol.1- 000001 DOC ID: 6281
DATE: 9/24/87 PAGES: 35
AUTHOR(S): ADDRESSEE(S):
Ecology & Environment, Inc. John E. Osborn/EPA
DESCRIPTION: Field Operations Work Plan for Monsanto Chemical Co., Soda Springs, Idaho, TDD No.:
F10-8702-06.
SUB-HEAD: 1. 6. . . Vol.1 - Site Inspection Reports / Documents
1. 6. . . Vol.1- 000001 DOC ID: 6282
DATE: 3/6/80 PAGES: 13
AUTHOR(S): ADDRESSEE(S):
Daryl F. Koch/EPA Unknown
DESCRIPTION: Potential Hazardous Waste Site, Site Inspection Report, Monsanto, Soda Springs Plant
1. 6. . . Vol.1 - 000002 DOC ID: =6283 -
DATE: 4/3/87 PAGES: 86
AUTHOR(S): ADDRESSEE(S):
Robert L. Geddes/Monsanto Jeff Whidden/Ecology & Environment, Inc.
DESCRIPTION: Various information to assist in the completion of the CERCLA site inspection.
1. 6. . . Vol.1- 000004 DOC ID: '6285
DATE: 1/1/88 PAGES: 5
AUTHOR(S): ADDRESSEE(S):
EPA Unknown
DESCRIPTION: Landfills Site Inspection Report (Supplemental Report); Storage Facilities Site Inspection Report
(Supplemental Report); Surface Impoundments Site Inspection Report (Supplemental Report);
Incinerators Site Inspection Report (Supplemental).
1.6. . . Vol.1 - 000003 DOC ID: 6284
DATE: 4/1/88 PAGES: 126
AUTHOR(S): ADDRESSEE(S):
Ecology & Environment, Inc. John E. Osborn/EPA
DESCRIPTION: Site Inspection Report for Monsanto Chemical Co., Soda Springs, Idaho.
IIC
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
1. 6. . . Vol. 1 - 000005 DOC ID: 6760
DATE: 10/5/88 PAGES: 8
AirTVIOR(S): ADDRESSEE(S):
Jeff Villnow/Ecology & Environment, Inc. John E. Osbom/EPA
DESCRIPTION: Response to Monsanto Chemical Co. Comments regarding the FIT Site Inspection Report.
SUB-HEAD: 1. 7.
. Vol.1 -
000010
Sampling and Analysis Data
1. 7. . . Vol.1 - 000010 DOC ID: 6295
DATE: 1/1/87 PAGES: 61
AUTHOR(S):
Unknown
DESCRIPTION: Well sampling data, Monsanto.
1.7. . . Vol.1- 000009 DOC ID: 6294
DATE: 11/9/87 PAGES: 28
AUTHOR(S):
Data Chem
DESCRIPTION: Appendix F. Organic Analysis Data Sheets.
1.7. . . Vol.1- 000001 DOC ID: 6286
DATE: 12/9/87 PAGES: 1
AUTHOR(S):
Ecology & Environment. Inc.
DESCRIPTION: Time sequence for Monsanto data.
ADDRESSEE(S):
Unknown
ADDRESSEE(S):
Unknown
ADDRESSEE(S):
David Bennett/EPA
1. 7. . . Vol.1 - 000002 DOC ID:
DATE: 1/15/88 PAGES:
AUTHOR(S):
Ula Accra/Ecology & Environment, Inc.
6287
7
ADDRESSEE(S):
John E. Osbom/EPA
DESCRIPTION: QA of two soil samples, case 8383 (Inorganics), Monsanto.
1.7. . . Vol.1 - 000003 DOC ID: 6288
DATE: 1/27/88 PAGES: 29
AUTHOR(S): ADDRESSEE(S):
James Hemdon/Ecology & Environment Inc. John E. Osbom/EPA
DESCRIPTION: Resubmittal of QA package for case 8383 (organics), Monsanto Chemical.
1.7. . .. Vol.1- 000004 DOC ID: 6289
DATE: 1/28/88 PAGES: 24
AUTHOR(S): ADDRESSEE(S):
James Hemdon/Ecology & Environment Inc. John E. Osbom/EPA
DESCRIPTION: QA of Case SAS 3453J (Sulfate, Phosphates/Phosphorus, Fluoride), Monsanto Chemical Co.
1.7. . . Vol.1 - 000005 DOC ID: 6290
DATE: 2/10/88 PAGES: 39
AUTHOR(S): ADDRESSEE(S):
James Hemdon/Ecology & Environment Inc. John E. Osbom/EPA
DESCRIPTION: QA of 31 Water Samples. Case 8383 (Inorganics), Monsanto Chemical Co.
1. 7. . . Vol.1 - 000006 DOC ID: 6291
DATE: 3/25/88 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Tom Colligan/Ecology & Environment Inc. John E. Osbom/EPA
DESCRIPTION: Domestic Well Table for Monsanto Chemical Co., Soda Springs, Idaho.
5/2/97
U.S. Environmental Protection Agency, Region 10
Page 8
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
1. 7. . . Vol.1- 000007 DOC ID: 6292
DATE: 5/4/88 PAGES: 8
AUTHOR(S): ADDRESSEE(S):
EPA Unknown
DESCRIPTION: EPA Region 10 lab management system, sample/project analysis results, Monsanto Chemical Co.,
Soda Springs, Idaho.
1. 7. . . Vol.1- 000008 DOC ID: 6293
DATE: 5/17/88 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
James Herndon/Ecology & Environment, Inc. John E. Osborn/EPA
DESCRIPTION: Review of CLP lab results, samples MJB-580 and MJB-581 (Inorganics), Monsanto.
1. 7. . . Vol.1- 000011 DOC ID: 6296
DATE: 5/24/89 PAGES: 14
AUTHOR(S): ADDRESSEE(S):
IDHW Bill Smith/DEQ
DESCRIPTION: Water Quality Report, radiological contaminants, drinking water system.
SUB-HEAD: 1. 8. . . Vol. 1 - Hydrogeological Investigation - Colder Report, Volume 1
1. 8. . . Vol.1- 000001 DOC ID: 6297
DATE: 11/1/85 PAGES: 375
AUTHOR(S): ADDRESSEE(S):
Colder Associates Monsanto
DESCRIPTION: Report of Hydrogeological Investigation, Soda Springs Plant Site, Volume 1, Main Text
SUB-HEAD: 1.8. . . Vol.2- Hydrogeological Investigation - Colder Report, Volume 2 and 3
1. 8. . . Vol.2- 000002 DOC ID: 6298
DATE: 9/1/85 PAGES: 185
AUTHOR(S): ADDRESSEE(S):
Colder Associates Monsanto
DESCRIPTION: Report of Hydrogeological Investigation, Soda Springs Plant Site, Volume 2, Appendices D - G.
1. 8. . . Vol.2- 000003 DOC ID: 6299
DATE: 9/1/85 PAGES: 150
AUTHOR(S): ADDRESSEE(S):
Colder Associates . Monsanto
DESCRIPTION: Report of Hydrogeological Investigation, Soda Springs Plant Site, Volume 3, Appendices H - K.
«i/?/Q7 IIS Ptiutrrtnmontal OrntorKnn A/ianr-i/ Buninn -in
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
HEADING: 2. 0. . . REMEDIAL INVESTIGATION / FEASIBILITY STUDY (RI/FS)
SUB-HEAD: 2. 1. . . Vol. 1 - Correspondence
2. 1. . . Vol.1 - 000001 DOC ID: 6300
DATE: 10/15/91 PAGES: 19
AUTHOR(S): ADDRESSEE(S):
David Banton/Golder Associates Timothy H. Brincefield/EPA
DESCRIPTION: Response to EPA comments, received 9/18/91, on the dispositions to Initial comments on the Draft
Phase I RI/FS Work Plan for the Monsanto Co. Soda Springs Elemental Phosphorus Plant
2. 1. . . Vol.1 - 000002 DOC ID: 6301
DATE: 11/21/91 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L Geddes/Monsanto
DESCRIPTION: Phase 1 Remedial Investigation / Feasibility Study Work Plan for the Monsanto Soda Springs
Facility.
2. 1. . . Vol.1 - 000003 DOC ID: 6302
DATE: 12/12/91 PAGES: 12
AUTHOR(S): ADDRESSEE(S):
Robert L. Geddes/Monsanto Timothy H. Brincefield/EPA
DESCRIPTION: Response to letter of 11/21/91 regarding RI/FS Work Plan for Monsanto Soda Springs Facility.
2. 1. . . Vol.1 - 000004 DOC ID: 6303
DATE: 3/13/92 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: Phase 1 Remedial Investigation / Feasibility Study for the Monsanto Soda Springs Facility.
2. 1. . . Vol.1 - 000005 DOC ID: 8675
DATE: 5/5/92 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L Geddes/Monsanto
DESCRIPTION: RE: Proposed Changes to Sampling Plans in the Remedial Investigation/Feasibility Study Work
Plan for the Soda Springs Elemental Phosphorus Plant with attached letter to Mr. Tim Brincefield
regarding Proposed Exposure Scenarios.
2. 1. . . Vol.1 - 000006 DOC ID: 8676
DATE: 6/15/92 PAGES: 7
Al/THOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: RE: Phase I Remedial Investigation/Feasibility Study Preliminary Site Characterization Report for
the Monsanto Soda Springs Facility; attached "EPA Comments on the Monsanto Chemical
Company Preliminary Site Characterization Summary Report"
2. 1. . . Vol.1 - 000007 DOC ID: 8677
DATE: 6/26/92 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: RE: Phase I Remedial Investigation/Feasibility Study (RI/FS) Remedial Alternatives Development
and Preliminary Screening of Candidate Technologies Memorandum wtth attached preliminary
EPA comments on this report
2. 1. . . Vol.1 - 000008 DOC ID: 8678
DATE: 8/20/92 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
5/2/97 U.S. Environmental Protection Agency, Region 10 Page 10
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
. Timothy H. Brincefield/EPA Robert L Geddes/Monsanto
DESCRIPTION: RE: Phase II Remedial Investigation/Feasibility Study Work Plan for the Soda Springs Elemental
Phosphorus Plant and attached preliminary hydrogeological comments on this report
2. 1. . . Vol.1 - 000009 DOC ID: 8679
DATE: 9/18/92 PAGES: 22
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: RE: Phase II Remedial Investigation/Feasibility Study Work Plan for the Soda Springs Elemental
Phosphorus Plant with attached comments. Also attached letter/report regarding Draft Preliminary
Identification of Contaminants of Concern (9/3/92).
2. 1. . . Vol.1 - 000010 DOC ID: 8680
DATE: 10/22/92 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: RE: Phase II Remedial Investigation/Feasibility Study (Rl/FS) Work Plan for the Soda Springs
Elemental Phosphorus Plant.
2.1. . . Vol.1- 1039499 DOC ID: 41162
DATE: 8/4/93 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Kent M. Angelos/Golder Associates Timothy H. Brincefield/EPA
DESCRIPTION: Letter regarding explanation and corrective action plan, fluoride and uranium results, Monsanto
Chemical Company.
2. 1. . . Vol.1 - 1039500 DOC ID: 41163
DATE: 5/11/94 PAGES: 16
AUTHOR(S): ADDRESSEES):
Robert L. Geddes/Monsanto Timothy H. Brincefield/EPA
DESCRIPTION: Comments on Monsanto draft Human Health and Ecological Risk Assessment.
2. 1. . . Vol.1 - 1039501 DOC ID: 41164
DATE: 10/4/94 PAGES: 3
AUTHOR(S): ,. ADDRESSEE(S):
Carol A. Rushin/EPA Pat Hyland/Monsanto
DESCRIPTION: Letter regarding Risk Assessment and jurisdictional issue.
2. 1. . . Vol.1 - 1039502 DOC ID: 41165
DATE: 10/26/94 PAGES: 10
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: Letter with comments of various interim Rl/FS deliverables: Air Dispersion Modelling Memo,
Groundwater Fate and Transport Modelling, Groundwater Quality Memo and Revised Soil and
Sediment Investigation Memo.
2. 1. . . Vol.1 - 1039503 DOC ID: 41166
DATE: 6/6/95 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: Letter regarding approval of revised RAO Memorandum for Soda Springs Elemental Phosphorus
Plant dated June 2,1995.
2. 1. . . Vol.1 - 1039504 DOC ID: 41167
DATE: 8/3/95 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
DESCRIPTION: Comments on responses to Phase II R.I. Comments.
2. 1. . . Vol.1- 1039505 DOC ID: 41168
DATE: 8/3/95 PAGES: 7
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: Comments on the draft Phase II Feasibility Study Development and Screening of Remedial
Alternatives.
2. 1. . . Vol.1 - 1039506 DOC ID: 41169
DATE: 9/8/95 PAGES: 5
AUTHOR(S): ADDRESSEE(S):
David Banton/Golder Associates Timothy H. Brincefield/EPA
DESCRIPTION: Monsanto responses to EPA comments on Phase II Remedial Investigation Report
2. 1. . . Vol.1 - 1039507 DOC ID: 41170
DATE: 9/29/95 PAGES: 7
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: Comments on revised draft Phase II Feasibility Study Development and Screening of Remedial
Alternatives.
2. 1. . . Vol.1- 1039508 DOC ID: 41171
DATE: 10/13/95 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: Letter regarding conference call to discuss comments on the Revised Draft Phase II Feasibility
Study Development and Screening of Remedial Alternatives.
2.1. . . Vol.1- 1039509 DOC ID: 41172
DATE: 10/23/95 PAGES: 12
AUTHOR(S): ADDRESSEE(S):
David Banton/Golder Associates Timothy H. Brincefield/EPA
DESCRIPTION: Response to EPA comments on Soda Creek Sediment Report.
2. 1. . . Vol.1 - 1039510 DOC ID: 41173
DATE: 10/24/95 PAGES: 10
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: Letter regarding Monsanto Remedial Investigation/Feasibility Study and requested change hi the
groundwater sampling program.
2. 1. . . Vol.1 - 1039511 DOC ID: 41174
DATE: 3/1/96 PAGES: 12
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L. Geddes/Monsanto
DESCRIPTION: Letter regarding Phase III Feasibility Study and response to EPA's earlier comments on Phase II
FS.
2. 1. . . Vol.1- 1039579 DOC ID: 42034
DATE: 3/7/96 PAGES: 4
AUTHOR(S): ADDRESSEE(S):
J. P. Hyland/Monsanto Randall F. Smith/EPA
DESCRIPTION: Follow-up letter to December 13,1995 presentation, to respond to question about appropriate risk
management criteria to be used to select a remedy for the Soda Springs Plant
5/2/97 U.S. Environmental Protection Agency, Region 10 Paae 12
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
2. 1. . . Vol.1- 1039580 DOC ID: 42035
DATE: 3/15/96 PAGES: 9
AUTHOR(S): ADDRESSEE(S):
Carl Stineman/Ecology and Environment, Inc. Timothy H. Brincefield/EPA
DESCRIPTION: Review of Stochastic Human Health Baseline Risk Assessment, Monsanto Superfund Site, Rl/FS
Oversight
2. 1. . . Vol.1 - 1039586 DOC ID: 42046
DATE: 7/23/96 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA Robert L Geddes/Monsanto
DESCRIPTION: Letter approving Remedial Investigation and Feasibility Study reports.
2. 1. . . Vol.1 - 1055986 DOC ID: 70481
DATE: 8/29/96 PAGES: 6
AUTHOR(S): ADDRESSEES):
Dean Pahl/Montgomery Watson Timothy H. Brincefield/EPA
DESCRIPTION: Memo transmitting a revised cost estimate (attached with cover memo) for the Monsanto Soda
Springs Plant Alternative 8.
SUB-HEAD: 2. 2. . . Vol.1- Statement of Work / Work Plan
2. 2. . . Vol. 1 - 000001 DOC ID: 6304
DATE: PAGES: 19
AUTHOR(S): ADDRESSEE(S):
Unknown Unknown
DESCRIPTION: Statement of Work for Monsanto Chemical Co. Remedial Investigation and Feasibility Study.
SUB-HEAD: 2. 3. . . Vol.1 - Sampling Data
2. 3. . . Vol. 1 - 000001 DOC ID: 6320
DATE: 5/10/91 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Matthew Gubitosa/EPA Christine Psyk/EPA
DESCRIPTION: Monitoring Well Primary Station Codes, Kerr-McGee and Monsanto, Soda Springs Sites, Idaho.
2. 3. . . Vol. 1 - 000002 DOC ID: 6321
DATE: 2/27/92 PAGES: 22
AUTHOR(S): ADDRESSEE(S):
David Banton/Golder Associates Robert L. Geddes/Monsanto
DESCRIPTION: Rl/FS Schedule and Preliminary Results of Groundwater Sampling.
SUB-HEAD: 2. 4. . . Vol.1 - QA/QC Plans
2. 4. . . Vol. 1 - 000001 DOC ID: 6322
DATE: 9/27/91 PAGES: 46
AUTHOR(S): ADDRESSEE(S):
David Banton/Golder Associates Timothy H. Brincefield/EPA
DESCRIPTION: QA/QC Plans from Krueger Lab, Chen Northern, and Accu-Lab.
SUB-HEAD: 2. 5. . . Vol. 1 - Rl/FS Reports
2. 5. . . Vol. 1 - 000001 DOC ID: 8672
DATE: 4/23/92 PAGES: 550
AUTHOR(S): ADDRESSEE(S):
Golder Associates EPA
5/2/97 IIS Fm/lronmontal Prr»tor*inr< Ananro Oowior. in
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
DESCRIPTION: Phase I Remedial Investigation/Feasibility Study, Preliminary Site Characterization Summary
Report for the Soda Springs Elemental Phosphorous Plant
SUB-HEAD: 2. 5. . . Vol. 2 - RI/FS Reports-Vol. 2
2. 5. . . Vol. 2 - 000002 DOC ID: 8673
DATE: 4/23/92 PAGES: 626
AUTHOR(S): ADDRESSEE(S):
Golder Associates EPA
DESCRIPTION: Appendices of Phase I Remedial Investigation/Feasibility Study, Preliminary Site Characterization
Summary Report for the Soda Springs Elemental Phosphorous Plant
SUB-HEAD: 2. 5. . . Vol. 3 - RI/FS Reports-Vol. 3
2. 5. . . Vol. 3 - 000003 DOC ID: 8681
DATE: 6/5/92 PAGES: 132
AUTHOR(S): ADDRESSEE(S):
Golder Associates Monsanto
DESCRIPTION: Phase I Remedial Investigation/Feasibility, Remedial Alternatives Development and Preliminary
Screening of Candidate Technologies Memorandum for the Soda Springs Elemental Phosphorus
Plant.
2. 5. . . Vol.3- 1039589 DOC ID: 42049
DATE: 9/23/92 PAGES: 331
AUTHOR(S): ADDRESSEE(S):
Golder Associates EPA
DESCRIPTION: Appendix S, Data Validation Summary, of Phase I RI/FS Preliminary Site Characterization
Summary Report.
SUB-HEAD: 2. 5. . . Vol. 4 - RI/FS Reports-Vol. 4
2. 5. . . Vol.4- 1039512 DOC ID: 41175
DATE: 5/24/95 PAGES: 84
AUTHOR(S): ADDRESSEE(S):
Golder Associates Monsanto
DESCRIPTION: Evaluation of Sediment Chemistry. Toxicity, and Benthic Invertebrate Community Structure In Soda
Creek and Alexander Reservoir.
2. 5. . . Vol.4- 1039513 DOC ID: 41176
DATE: 11/21/95 PAGES: 424
AUTHOR(S): ADDRESSEE(S):
Golder Associates Monsanto
DESCRIPTION: Phase II Remedial Investigation Report - Volume I.
SUB-HEAD: 2. 6. . . Vol. 5 - RI/FS Reports-Vol. 5
2. 5. . . Vol.5- 1039514 DOC ID: 41182
DATE: 11/21/95 PAGES: 1,060
AUTHOR(S): ADDRESSEE(S):
Golder Associates Monsanto
DESCRIPTION: Phase II Remedial Investigation Report - Volume II, Appendices A-H.
SUB-HEAD: 2. 5. . . Vol. 6 - RI/FS Reports-Vol. 6
2. 5. . . Vol.6- 1039515 DOC ID: 41185
DATE: 11/21/95 PAGES: 1,110
AUTHOR(S): ADDRESSEE(S):
5/2/97 U.S. Environmental Protection Agency. Region 10 Paoe 14
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
Colder Associates Monsanto
DESCRIPTION: Phase II Remedial Investigation Report - Volume III, Appendices H-7 through L.
SUB-HEAD: 2. 5. . . Vol. 7 • RI/FS Reports-Vol. 7
2. 5. . . Vol. 7- 1039516 DOC ID: 41188
DATE: 11/21/95 PAGES: 998
AUTHOR(S): ADDRESSEE(S):
Colder Associates Monsanto
DESCRIPTION: Phase II Remedial Investigation Report - Volume IV, Appendix L-2 through Appendix O.
SUB-HEAD: 2. 5. . . Vol. 8 - RI/FS Reports-Vol. 8
2. 5. . . Vol.8- 1055987 DOC ID: 70482
DATE: 1/1/95 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Colder Associates Unknown
DESCRIPTION: Monsanto Plant Distribution of Constituents that Exceed MCLs In Groundwater or a 3x10-4 Target
Cleanup Level In Offsite Soils (map).
2. 5. . . Vol.8- 1039581 DOC ID: 42036
DATE: 5/30/96 PAGES: 486
AUTHOR(S): ADDRESSEE(S):
Montgomery Watson EPA
DESCRIPTION: Feasibility Study, The Monsanto Company, Elemental Phosphorus Plant, Soda Springs, Idaho, with
replacement pages dated May 30,1996 (bulk of report is version dated April 1996).
SUB-HEAD: 2. 6. . . Vol.1 - Risk Assessments
2. 6. . . Vol.1- 1039523 DOC ID: 41204
DATE: 3/1/96 PAGES: 308
AUTHOR(S): ADDRESSEE(S):
Montgomery Watson Timothy H. Brincefield/EPA
DESCRIPTION: Stochastic Human Health Baseline Risk Assessment, March 1996.
2. 6. . . Vol.1 - 1055988 DOC ID: 70484
DATE: 1/20/97 PAGES: 13
AUTHOR(S): ADDRESSEE(S):
Gordon Randall/Ecology & Environment, Inc. Timothy H. Brincefield/EPA
DESCRIPTION: Technical Memorandum: Risk Calculations for Agricultural Workers at Monsanto.
SUB-HEAD: 2. 7. . . Vol.1 - Proposed Plan
2. 7. . . Vol.1 - 1039587 DOC ID: 42048
DATE: 7/29/96 PAGES: 16
AUTHOR(S): ADDRESSEE(S):
EPA Unknown
DESCRIPTION: Proposed Plan to clean up Monsanto Superfund Site. Announces public comment period on
proposed plan through August 30 and a public meeting scheduled for August 13.
5/2/97 U.S. Environmental Protection Anpnrv RAninn m
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
HEADING: 3. 0. . . RECORD OF DECISION
3. 0. . . Vol.1- 1019940 DOC ID: 70579
DATE: 4/30/97 PAGES: 97
AUTHOR(S): ADDRESSEE(S):
Chuck Clarke/EPA Unknown
DESCRIPTION: Record of Decision (Cleanup Plan) for Monsanto site, with attachments including administrative
record index.
SUB-HEAD: 3. 1. . . Vol.1 • Memo to File
3. 1. . . Vol.1- 1019943 DOC ID: 70642
DATE: 4/30/97 PAGES: 54
AUTHOR(S): ADDRESSEE(S):
Timothy H. Brincefield/EPA File
DESCRIPTION: Memo to file describing documents added to administrative record and how they were considered
in the Record of Decision, with attachments.
5/2/97 U.S. Environmental Protection Agency, Region 10 Page 16
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
HEADING: 4. 0. . . STATE COORDINATION
SUB-HEAD: 4. 1. . . Vol.1 - Correspondence
4. 1. . . Vol.1- 1039524 DOC ID: 41205
DATE: 7/7/95 PAGES: 6
AUTHOR(S): ADDRESSEE(S):
Gordon Brown/Idaho Division of Environmental Quality Timothy H. Brincefield/EPA
DESCRIPTION: State of Idaho comments on Monsanto Development and Screening of Remedial Alternatives
Memorandum.
4. 1. . . Vol.1 - 1039525 DOC ID: 41206
DATE: 9/18/95 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Gordon Brown/Idaho Division of Environmental Quality Timothy H. Brincefield/EPA
DESCRIPTION: State of Idaho comments on Monsanto 2nd Draft of the Development and Screening of Remedial
Alternatives Memorandum.
4. 1. . . Vol.1 - 1039582 DOC ID: 42038
DATE: 12/21/95 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Gordon Brown/Idaho Dept. of Health & Welfare Timothy H. Brincefield/EPA
DESCRIPTION: State of Idaho comments on Monsanto Phase III Feasibility Study.
4. 1. . . Vol.1 - 1039584 DOC ID: 42039
DATE: 5/7/96 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Gordon Brown/Idaho Dept. of Health & Welfare Timothy H. Brincefield/EPA
DESCRIPTION: State of Idaho comments to the 4th Draft of the Monsanto Feasibility Study and Stochastic Risk
Assessment
4. 1. . . Vol.1 - 1039585 DOC ID: 42040
DATE: 6/24/96 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Idaho Department of Environmental Quality Timothy H. Brincefield/EPA
DESCRIPTION: State of Idaho comments on the Monsanto Draft Proposed Plan.
5/7/B7
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
HEADING: 5. 0. . . ENFORCEMENT
SUB-HEAD: 6. 1. . . Vol. 1 - Correspondence
5. 1. . . Vol.1 - 000001 DOC ID: 6323
DATE: 7/24/90 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Donald R. Wind/Monsanto EPA
DESCRIPTION: Annual Notification of a Continuous Release.
5. 1. . . Vol.1 - 000002 DOC ID: 6324
DATE: 10/17/90 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
John Meyer/EPA Dean Nygard/IDHW
DESCRIPTION: Transmits Monsanto Soda Springs Rl/FS Administrative Order.
SUB-HEAD: 5. 2. . . Vol. 1 - Notice Letters and Responses
5. 2. . . Vol. 1 - 000001 DOC ID: 6325
DATE: 10/17/90 PAGES: 85
AUTHOR(S): ADDRESSEE(S):
Charles E. Findley/EPA J. P. Hyiand/Monsanto
DESCRIPTION: Transmits Draft Administrative Order on Consent for Remedial Investigation / Feasibility Study.
5. 2. . . Vol. 1 - 000002 DOC ID: 6326
DATE: 10/31/90 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Kent V. Lott/Monsanto John Meyer/EPA
DESCRIPTION: Requests meetings to discuss Rl/FS requirements.
SUB-HEAD: 5. 3. . . Vol.1 - Good Faith Proposals
5. 3. . . Vol. 1 - 000001 DOC ID: 6327
DATE: 12/7/90 PAGES: 91
AUTHOR(S): ^ ADDRESSEE(S):
Stephan Krchma/Monsanto ' Charles Ordine/EPA
DESCRIPTION: Monsanto Soda Springs Plant, good faith offer to perform remedial investigation/feasibility study.
SUB-HEAD: 5. 4. . . Vol. 1 - Administrative Orders
5. 4. . . Vol. 1 - 000001 DOC ID: 6328
DATE: 4/19/91 PAGES: 81
AUTHOR(S): ADDRESSEE(S):
Philip G. Millam/EPA C. M. McCullough/Monsanto
DESCRIPTION: Administrative Order on Consent issued to the Monsanto Co. for the Monsanto (Soda Springs)
Superfund Site.
5/2/97 U.S. Environmental Protection Agency, Region 10 Page 18
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
HEADING: 6. 0. . . HEALTH ASSESSMENTS
SUB-HEAD: 6. 1. . . Vol.1 - Correspondence / Comments
6. 1. . . Vol.1 - 000001 DOC ID: 6329
DATE: 6/6/91 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Harvey W. Rogers/U. S. Department of Health & Human John Meyer/EPA
Services
DESCRIPTION: Monsanto preliminary hearth assessment
6. 1. . . Vol.1 - 000002 DOC ID: 6330
DATE: 6/6/91 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Max M. Howie/DepL of Health & Human Services John Meyer/EPA
DESCRIPTION: Transmits a copy of the Preliminary Health Assessment Public Commment Release for the
Monsanto, Soda Springs Plant Site.
6. 1. . . Vol.1 - 000003 DOC ID: 6331
DATE: 7/17/91 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Christine Psyk/EPA Lydia O. Askew/Agency for Toxic Substances and
Disease Registry
DESCRIPTION: Transmits comments regarding Preliminary Health Assessment for Monsanto, Soda Springs Plant
SUB-HEAD: 6. 2. . . Vol.1 - Health Assessments
6. 2. . . Vol. 1 - 000001 DOC ID: 6332
DATE: PAGES: 11
AUTHOR(S): ADDRESSEE(S):
Harvey W. Rogers/U. S. Department of Health & Human Unknown
Services
DESCRIPTION: Preliminary Health Assessment for Monsanto Chemicals, Soda Springs, Idaho.
6. 2. . . Vol. 1 - 000002 DOC ID: 6333
DATE: 10/17/90 PAGES: 4
AUTHOR(S): ADDRESSEE(S):
Charles E. Findley/EPA J. P. Hyland/Monsanto
DESCRIPTION: Informing recipient that EPA is preparing to initiate a RI/FS to determine the nature and extent of
release of hazardous substances from the Monsanto Soda Springs site.
6. 2. . . Vol.1 - 000003 DOC ID: 6334
DATE: 6/3/91 PAGES: 5
AUTHOR(S): ADDRESSEE(S):
Department of Health & Human Services Unknown
DESCRIPTION: Public comment announcement for the Monsanto site.
6. 2. . . Vol. 1 - 000004 DOC ID: 6335
DATE: 6/6/91 PAGES: 19
AUTHOR(S): ADDRESSEE(S):
Harvey W. Rogers/U. S. Department of Health & Human Unknown
Services
DESCRIPTION: Preliminary Health Assessment for Monsanto, Soda Springs Plant.
S/ 7JS7
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
HEADING: 7. 0. . . NATURAL RESOURCE TRUSTEES
SUB-HEAD: 7. 1. . . Vol. 1 - Correspondence
7. 1. . . Vol. 1 - 000001 DOC ID: 6336
DATE: 7/27/90 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
David M. Bennett/EPA . Michael Slater/EPA
DESCRIPTION: Request that U.S. Department of Interior conduct Preliminary Natural Resource Surveys at
Monsanto Soda Springs and Kerr-McGee Soda Springs.
7. 1. . . Vol.1 - 000002 DOC ID: 6337
DATE: 10/17/90 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
John Meyer/EPA Charles S. Polityka/U. S. Dept of the Interior
DESCRIPTION: Transmits a copy of the Monsanto Special Notice package for the initiation of negotiations for a
RI/FS on the Soda Springs plant.
7. 1. . . Vol.1 - 000003 DOC ID: 6338
DATE: 6/12/91 PAGES: 6
AUTHOR(S): ADDRESSEE(S):
Jonathan P. Deason/U. S. Department of Interior Charles E. Findley/EPA
DESCRIPTION: Preliminary natural resources survey on the Monsanto Soda Springs site.
7. 1. . . Vol.1- 1055989 DOC ID: 70485
DATE: 10/4/96 PAGES: 4
AUTHOR(S): ADDRESSEE(S):
Preston Sleeger/USDOl Timothy H. Brincefield/EPA
DESCRIPTION: Department of Interior comments following review of the proposed remedial action plan for the
Monsanto Soda Springs Plant (a list of endangered and threatened species that may occur In Bear
Lake County is attached).
5/2/97 U.S. Environmental Protection Agency, Region 10 Page 20
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
HEADING: 8. 0. . . CONGRESSIONAL INQUIRIES
SUB-HEAD: 8. 1. . . Vol.1 - Correspondence.
8. 1. . . Vol.1 - 000001 DOC ID: 6339
DATE: 1/24/92 PAGES: 9
AUTHOR(S): ADDRESSEE(S):
Dana A. Rasmussen/EPA Larry Craig/U. S. Senate
DESCRIPTION: Transmittal of results of the Science Advisory Board review of the Idaho Radionuclide Study.
5/2/97 US* Pni«rftnm«ntfll Prnfprfinn flnonrv Ronir>n in
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
HEADING: 9. 0. . . PUBLIC PARTICIPATION
SUB-HEAD: 9. 1. . . Vol.1 - Correspondence
9. 1. . . Vol.1 - 1055990 DOC ID: 70487
DATE: 8/19/96 PAGES: 2
AUTHOR(S): ADDRESSEES):
Mark Steele/Unknown Timothy H. Brincefield/EPA
DESCRIPTION: Response to request for public comments voicing support for the EPA's preferred alternative for
the Monsanto site.
9. 1. . . Vol.1 - 1055991 DOC ID: 70488
DATE: 8/21/96 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Kirk L. Hansen/City of Soda Springs Timothy H. Brincefield/EPA
DESCRIPTION: Letter requesting a transcript of the public meeting on the Monsanto Soda Springs site and a 30
day extension of the comment period.
9. 1. . . Vol.1 - 1055992 DOC ID: 70489
DATE: 9/3/96 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Robert D. Gunnell/Eari Gunnel! & Sons, Inc. Timothy H. Brincefield/EPA
DESCRIPTION: Letter voicing strong opposition to the rezoning proposal entailed in the proposed Monsanto
clean-up plan.
9. 1. . . Vol.1 - 1055993 DOC ID: 70490
DATE: 9/8/96 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Charlotte Gunnell/Unknown Timothy H. Brincefield/EPA
DESCRIPTION: Comments on the restrictive zoning alternative for the Monsanto Soda Springs Plant cleanup.
9. 1. . . Vol.1 - 1055994 DOC ID: 70491
DATE: 9/9/96 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
E. Leroy Gunnell/Unknown Timothy H. Brincefield/EPA
DESCRIPTION: Comments on restricting use of private property and cleaning up contaminated property.
9. 1. . . Vol.1 - 1055995 DOC ID: 70492
DATE: 9/26/96 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Ron Lau/Unknown Timothy H. Brincefield/EPA
Carolyn Lau/Unknown Timothy H. Brincefield/EPA
DESCRIPTION: Comments on the restrictive zoning alternative for the Monsanto Soda Springs Plant cleanup.
9. 1. . . Vol.1 - 1055996 DOC ID: 70493
DATE: 9/30/96 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Robert L. Geddes/Monsanto Timothy H. Brincefield/EPA
DESCRIPTION: Letter providing Monsanto comments on the 7/96 proposed plan for the Monsanto Elemental
Phosphorous Plant
9. 1. . . Vol.1 - 1055997 DOC ID: 70494
DATE: 11/22/96 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
Kirk L. Hansen/City of Soda Springs Catherine Krueger/EPA
5/2/97 U.S. Environmental Protection Agency, Region 10 Page 22
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
DESCRIPTION: Letter listing City of Soda Springs principles that apply to implementation of the Monsanto Soda
Springs Superfund plan of action.
SUB-HEAD: 9. 2. . . Vol.1 - Newspaper / Journal Articles
9. 2. . . Vol. 1 - 000002 DOC ID: 6341
DATE: 11/8/09 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Caribou County Sun Unknown
DESCRIPTION: Monsanto Meets New EPA Standards; FMC Note High Cost of Compliance.
9. 2. . . Vol. 1 - 000001 DOC ID: 6340
DATE: 6/22/89 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Ellen Carney/Caribou County Sun Unknown
DESCRIPTION: Republican State Senators Tour Plants.
9. 2. . . Vol. 1 - 000003 DOC ID: 6342
DATE: 12/5/91 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Caribou County Sun Unknown
DESCRIPTION: Citizens Committee Gives Slag Update.
9. 2. . . Vol. 1 - 000004 DOC ID: 6343
DATE: 12/26/91 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
Caribou County Sun Unknown
DESCRIPTION: Monsanto Recognized by BLM for Their Public Land Efforts.
SUB-HEAD: 9. 3. . . Vol. 1 - Community Relations Plan
9. 3. . . Vol. 1 - 000001 DOC ID: 6344
DATE: 12/17/91 PAGES: 12
AUTHOR(S): ADDRESSEE(S):
EPA r Unknown
DESCRIPTION: Community Relations Plan, Monsanto Chemical Co., Caribou County, Idaho.
SUB-HEAD: 9. 4. . . Vol.1 - Fact Sheets / Press Releases
9. 4. . . Vol. 1 - 000001 DOC ID: 6345
DATE: 12/1/91 PAGES: 1
AUTHOR(S): ADDRESSEE(S):
EPA Unknown
DESCRIPTION: EPA Fact Sheet, Monsanto Elemental Phosphorus Plant, Caribou County, Idaho.
9. 4. . . Vol. 1 - 000002 DOC ID: 6346
DATE: 1/22/92 PAGES: 4
AUTHOR(S): ADDRESSEE(S):
EPA Unknown
DESCRIPTION: Transmits a copy of the letter report to EPA from the Science Advisory Board regarding Idaho
Radionuclide Study/Phosphate Slag Issue.
9. 4. . . Vol. 1 - 000003 DOC ID: 6776
DATE: 5/8/92 PAGES: 2
AUTHOR(S): ADDRESSEE(S):
EPA Unknown
5/2/97 U-S.EnwirniuniMrtal PrnteHi/wi Anonrw Deoinr. in
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
DESCRIPTION: Supefund Fact Sheet Monsanto Elemental Phosphorous Plant. Caribou County - Monsanto to
conduct additional testing this Spring and Summer.
9. 4. . . Vol.1 - 1039661 DOC ID: 42328
DATE: 7/29/96 PAGES: 4
AUTHOR(S): ADDRESSEE(S):
EPA Unknown
DESCRIPTION: Superfund Fact Sheet inviting citizens to comment on Proposed Plan and announcing public
meeting to be held August 13.
SUB-HEAD: 9. 5. . . Vol.1 - Meeting Transcripts
9. 5. . . Vol.1- 1019941 DOC ID: 70580
DATE: 8/13/96 PAGES: 22
AUTHOR(S): ADDRESSEE(S):
Lance D. Oviatt/Unknown Unknown
DESCRIPTION: Public Meeting transcript for meeting held August 13,1996.
5/2/97 U.S. Environmental Protection Agency, Region 10 Page 24
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(MONAR) MONSANTO SODA SPRINGS PLANT - ADMINISTRATIVE RECORD INDEX
HEADING: 10. 0. . . TECHNICAL SOURCES AND GUIDANCE DOCUMENTS
SUB-HEAD: 10.1. . . Vol.1 - EPA Guidance
10.1. . . Vol.1- 1055998 DOC ID: 70495
DATE: PAGES: 7
AUTHOR(S): ADDRESSEE(S):
Elliott P. Laws/EPA EPA
DESCRIPTION: OWSER Directive No. 9355.7-04 - Memorandum: Land Use in the CERCLA Remedy Selection
Process.
•
10.1. . . Vol.1- 000001 DOC ID: 6347
DATE: 1/18/84 PAGES: 3
AUTHOR(S): ADDRESSEE(S):
Lee M. Thomas/EPA Unknown
DESCRIPTION: Definition of procedures and regional responsibilities for the final rulemaking on the first NPL
update.
10. 1. . . Vol.1 - 000002 DOC ID: 6348
DATE: 3/10/87 PAGES: 24
AUTHOR(S): ADDRESSEE(S):
Henry L. Longest/EPA EPA
DESCRIPTION: RCRA Special Study waste definitions: sites that require additional consideration prior to NPL
proposal under the Superfund Amendments and Reauthorization Act.
10. 1. . . Vol.1 - 000003 DOC ID: 6349
DATE: 5/29/87 PAGES: 15
AUTHOR(S): ADDRESSEE(S):
Henry L. Longest/EPA EPA
DESCRIPTION: Interim guidance for consideration of sections 105(g) and 145 of the Superfund Amendments and
Reauthorization Act of 1986 prior to NPL proposal of special study waste sites.
SUB-HEAD: 10. 2. . . Vol.1 - Technical Sources
10.2. . . Vol.1 - 000001 DOC ID: 6777
DATE: 5/1/83 PAGES: 337
AUTHOR(S): ADDRESSEE(S):
Dale R. Ralston/Department of Geology, University of Unknown
Idaho
DESCRIPTION: Thermal Ground Water Flow Systems in the thrust Zone in Southeastern Idaho.
5/2/97 U.S. Environmental Prnt«rHnn An«nrv Roninn m Dona •>«;
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