PB97-9<>3123
EPA/541/R-97/067
November 1997
EPA Superfund
Record of Decision Amendment:
Clare Water Supply,
Clare, MI
5/15/1997
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Record of Decision Amendment to Change Soils Remedy and Cleanup Criteria
Clare Water Supply Superfund Site
Clare, Michigan
Introduction
Reasons for a Change in Remedy
The United States Environmental Protection Agency (USEPA) is the lead agency on this
site with the Michigan Department of Environmental Quality (MDEQ) as the support
agency for the conduct of the remedial action at the Site under the authority of the
Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), as
amended, 42 U.S.C. § 9601, eiseg. In September 1992, USEPA issued a Record of
Decision (1992 ROD) which outlined the remedy selection process and selected the
cleanup action for the soils and groundwater at the Site. The State concurred with the
selected remedy. During Remedial Design (RD), information has come to light which
necessitates modifications to aspects of the portion of the remedy related to soils cleanup.
This document provides the background information as to why the modifications are
necessary and outlines what modifications to the selected remedy are being adopted. On
April 26,1995, the Clare PRP Group submitted a petition to USEPA asking that the
Agency amend the 1992 ROD to change the remedy. This petition was later
supplemented with additional information on July 8,1996. In these documents, the Clare
Group brought to USEPA's attention new information that substantially supports the need
to significantly alter the remedy. This information is summarized below:
1) In-Situ Soil Vapor Extraction (ISVE) was demonstrated not to be a feasible remedy
for the clay and till layers which lie from 7 to 12 feet below the ground surface.
Results of In-situ vapor extraction tests conducted during the pre-design investigations
indicate that the low air conductivity (10-7 cm/sec effective air conductivity) properties of
the unsaturated clay and till encountered beneath the Ex-Cell-O and Mitchell Facilities are
not suitable for implementing the selected ISVE soil remedy in this formation due to the
inability to efficiently withdraw air as required for the ISVE technology to work effectively.
This determination was made based on the inability to induce air flow in the subsurface
even at well head vacuums as high as 20 inches of mercury at either site.
Because ISVE was demonstrated not to be a feasible remedy for addressing the
underlying clay and till layers, alternative remedial technologies for soil were proposed and
evaluated.
2) Changes in State Cleanup Standards.
The original ROD was issued to meet State Cleanup levels then in existence. At that time,
the Michigan Environmental Response Act(Act 307) provided those levels. In 1994, Act
307 was revised and incorporated into Part 201 of the Natural Resources and
Environmental Protection Act (NREPA),1994 P.A. 451, as amended. Under Part 201,
criteria for various categories of cleanup were also revised.
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Because of these revisions, the ROD cleanup standards were re-examined and are
amended through this ROD.
Procedure for Changing the Remedy
Under Section 117(c) of the Comprehensive Environmental Response, Compensation and
Liability Act (CERCLA), 42 U.S.C. § 9617(c) and Section 300.435(c)(2)(ii) of the National
Oil and Hazardous Substances Contingency Plan (NCP), if USEPA takes any remedial
action which differs in any significant respect from a final remedial action plan, the Agency
is required to publish an explanation of the significant differences and the reasons such
changes were made. The decision by USEPA to change the remedy at the Clare Water
Supply Site constituted such a significant difference. Indeed, USEPA considers this to be
a fundamental change in the remedy, necessitating the issuance of a new proposed plan
and an amended ROD.
Accordingly, a proposed plan was issued in August, 1996, and the public was invited to
comment on the alternative remediation methods proposed in the proposed plan . A 30
day public comment period was initiated and a public meeting to discuss the proposed
change in the remedy was held on August 28,1996 at 7:00 pm at the Clare City Hall in
Clare, Michigan.
This proposed plan is part of an administrative record which is available for public
inspection at the Clare Public Library, 5th & McEwan, Clare, Michigan. This amended
ROD also will become part of the administrative record for the site. The administrative
record may also be reviewed at USEPA Region 5, 77 West Jackson Boulevard, Chicago,
Illinois.
After reviewing the current status of the Site and comparing remedial alternatives, USEPA
believed that the request made by the PRP Group to amend the remedy for the
contaminated soils at the Clare Water Supply Site had merit and should be evaluated.
Consequently, USEPA proposed to amend the 1992 ROD to change the previously
selected remedy. After reviewing the public comments, USEPA has determined to change
the selected remedy for soils from ISVE to Dual-Phase vacuum extraction and
encapsulation. This amended remedy will include the following major components:
installation of a perimeter slurry cut-off wall, groundwater dewatering and treatment,
excavation and consolidation of soils, shallow soil ISVE, and construction of a multi-media
cap and groundwater monitoring. In addition, the cleanup levels for both soils and
groundwater will be amended to reflect changes in State law.
I. Site Location and Description
The Clare Water Supply Site (the Site) is in the southwestern quadrant of the City of Clare,
Michigan; in the southeast 1/4 of Section 34, Township 17 North, Range 4 West of Grant
Township, Clare County, Michigan. The site is generally bounded to the north by 5th
Street (U.S. Highway 10). The western boundary of the site roughly corresponds to the
western side of the Mitchell Property, and the well field is bounded to the east by Maple
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Street (Figure 1). The Ann Arbor railroad line traverses the site from the south to north
and the C&O Railroad line crosses the site at the northwest edge. The Little Tobacco
Drainage ditch flows across the well field entering from the southern border of the
industrial area located directly west-northwest of the municipal well field.
II. Site History and Enforcement Activities
The Clare Water Supply system withdraws groundwater from four municipal wells (MW) in
the area, each tapping an unconsolidated sand aquifer which occurs between
approximately 30 to 80 feet below the surface. Two of the wells, MW #2 and MW #5, are
located in the northeastern portion of the site. Based on sampling since 1981, these wells
have been shown to be contaminated. The contaminants in these wells consist primarily
of chlorinated hydrocarbons. Two uncontaminated wells, MW#6 and MW#7, are located
generally south and southwest of the contaminated portion of the site, respectively. The
Clare Water Supply is the Public Water Supply for the 3,300 residents of Clare, Michigan.
Groundwater at the Site has been found to be the only feasible source of drinking water for
the community.
On September 27,1985, a Consent Order was signed which allowed four Potentially
Responsible Parties (PRPs) to complete a Remedial Investigation/Feasibility Study at the
Clare Water Supply Site in Clare, Michigan under the oversight of USEPA and the State.
The Remedial Investigation (Rl) was initiated in September, 1988.
Interim Action
The sampling results obtained from the Rl field work indicated that the levels of
contaminants in the water supplied to consumers were approaching or equal to the
Maximum Contaminant Levels (MCLs) provided for under the Safe Drinking Water Act.
Consequently, USEPA prepared an Interim Action Record of Decision (ROD) in August of
1990. This Interim Action ROD provided for wellhead treatment of the water supply until
the RI/FS was completed and the overall site remedy implemented. The ROD selected air
stripping of the city water supply as the preferred remedy for the interim action. The air
strippers were installed and began operating in March of 1991 and are removing over 90%
of the volatile contaminants from the City's water supply.
Remedial Investigation / Feasibility Study
A Remedial Investigation (Rl) Report prepared by the PRPs was submitted in October of
1990. The results of this report are summarized in a subsequent ROD dated September
16,1992. A Feasibility Study (FS) prepared by the PRPs was submitted in February of
1992. The Feasibility Study (FS) submitted in February of 1992 was modified by USEPA
and it was released in May of 1992. The FS report evaluated a no action alternative, two
minimal action alternatives involving the use of institutional controls and/or containment,
two treatment alternatives for contaminated soil and two treatment alternatives for
contaminated groundwater.
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Record of Decision
A second Record of Decision was signed on September 16,1992 (1992 ROD). The ROD
memorialized the selection of a combined remedy which called for groundwater collection
and treatment using Ultraviolet Photochemical Catalytic Oxidation and for in-situ vapor
extraction and treatment for the contaminated soils. This remedy was selected to meet
the USEPA's objective of restoring the only source of groundwater for the population of
Clare to its beneficial use as a drinking water supply within a reasonable time frame.
The combined alternative chosen included use, deed and/or access restrictions as
necessary; diversion of the US10 Drainage Ditch around contaminated sediments while
the remedial action was being conducted; Soil Vapor Extraction; and ground water
extraction and treatment using ultraviolet photochemical oxidation.
Subsequent Actions
After negotiations for a Consent Decree were unsuccessful, on August 17,1992, the
USEPA issued a Unilateral Administrative Order (UAO) under Section 106 of the
Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as
amended by the Superfund amendments and Reauthorization Act of 1986 (CERCLA) for
the Clare Water Supply Site, Operable Unit #2, Clare, Michigan. The UAO required that
Potentially Responsible Parties (PRPs) complete the design and implementation of the
remedial action selected in the ROD.
Explanation of Significant Differences
On August 4,1995, USEPA issued an Explanation of Significant Differences (ESD)
which modified the remedy selected in the 1992 ROD for the groundwater portion of the
cleanup work in Clare. Basically, this ESD changed the selected treatment method for the
groundwater from ultraviolet photo-chemical oxidation to air stripping. Since both of these
alternatives were originally evaluated in the 1992 Feasibility Study and the ROD and were
available to the public to comment upon, consequently this change did not necessitate
public involvement and an ESD was signed by the USEPA with concurrence from the
Michigan Department of Natural Resources (currently known as the Michigan Department
of Environmental Quality {MDEQ}).
III. Community Relations History
The proposed ROD Amendment was issued to the public on August 20,1996. This began
a 30 day public comment period on the proposed amendments. A public meeting to
discuss and receive comments on the proposed ROD amendment was held in Clare on
August 28,1996. The comment period ended on September 19,1996. See Section III of
the 1992 ROD for the community relations history prior to this ROD Amendment.
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IV. Scope and Role of Operable Unit
USEPA has organized this project into two operable units.
The first operable unit was an interim action to address contamination of the drinking water
supply. The contaminants of concern were Trichloroethane (TCE) and TCE-degradation
products (Record of Decision date August 18,1990). The interim action provided
wellhead treatment in order to maintain a safe drinking water supply and will continue as
long as the levels of contaminants in the untreated supplied water equal or exceed any
Maximum Contaminant Level (MCL).
The second operable unit involved the final remedial action to address more completely
groundwater contamination as well as source areas of contamination in the soils. The
second ROD dated September 16,1992, set forth the original remedy selected for this
operable unit. This remedy was modified through an ESD dated August 4,1995, and is
further amended through this ROD amendment.
USEPA has identified the principal threat to human health and the environment at the
Clare Water Supply Site to be the contaminated soil areas shown in Figure 2 which are to
be addressed in this ROD Amendment. The contaminated groundwater which was also
part of the second operable unit is currently being addressed by the groundwater collection
and treatment system which the PRPs have already constructed and started to operate.
The modified remedy is anticipated to be the final remedial action with respect to the soils
areas identified in the second operable unit ROD. Other source areas may need to be
addressed as they are identified. The groundwater plume and contaminated soils will be
treated in accordance with applicable or relevant and appropriate requirements of Federal
and State law. In addition, the USEPA considers encapsulation and treatment by dual-
phase vacuum extraction of the contaminated soil, which is the source of groundwater
contamination and is a principal threat, to be the most practicable remedy at this time.
In addition, this ROD Amendment changes the selected cleanup levels for soils and
groundwater wells to the new standards promulgated by the Michigan Department of
Environmental Quality (MDEQ).
V. Site Characteristics
See 1992 ROD for complete description. The permeability to air of the site soils below a
depth of 12 or 15 feet is the only characteristic for which new information has become
available since the 1992 ROD. Additional information related to this issue can be found in
the petitions dated April 26,1995 and July 8,1996.
VI. Site Risks
See 1992 ROD for complete description.
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VII. Remedial Action Objectives
Since the 1992 ROD, changes in cleanup standards at the State level for ground water and soil
have occurred. The cleanup levels in the 1992 ROD were developed to meet requirements of
the Michigan Environmental Response Act (Act 307) and USEPA's acceptable risk range. In
1994, Act 307 was revised and incorporated as Part 201 of the Natural Resources and
Environmental Protection Act (NREPA) 1994 P.A. 451, as amended. In light of NREPA Part
201, cleanup standards will be revised to reflect current State of Michigan and Federal
regulations:
CLEANUP STANDARDS
(Based on Michigan Residential Category)
Benzene
Vinyl Chloride
Trichloroethane
Tetrachloroethene
Methylene Chloride
Trans 1 ,2-Dichloroethene
Cis 1 ,2-Dichloroethene
Total Xylenes
Toluene
Ethylbenzene
1, 1 -Dichloroethane
1,2-Dichloroethane
1 , 1 ,2-Trichloroethane
1,1.1 -Trichloroethane
Styrene
Soil Standards (a)
Act 307
(Old)
20
0.40b
60
N:;-":;: =
100
2000
1400
6000
20000
1000
14000
8,b
12
4000
20
Part 201
(New)
100
40
100
100
100
2000
1400
5600
16000
1500
18000
100
100
4000
2000
Groundwater Standards
Act 307
(Old)
1':='!: '
0.02;b
:.:3HH:P:;/:
•o&iiW;1.-:'
*\-':\^;-
100
70
300
800
70
700
0.4, b
0.6,b
200
i
Part 201
(New)
5
2
5
5
5
100
70
10000
1000
700
880
5
5
200
100
Notes:
a) State specified clean-up criteria are prepared in accordance with the Interim Environmental
Response Division Operational Memorandum #8, Revision 4: Generic Residential Clean-up
Criteria as amended June 5, 1995. Soil clean-up criteria are based on 20 times the health-
based drinking water value for the State of Michigan.
b) The old MDEQ acceptable Method Detection Limit (MDL) for this constituent was 10 ug/L
for soil. The cleanup level was lower than the current acceptable MDL so the cleanup level
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that was to be enforced for this action is the MDL.
c) Under Part 201, an evaluation of potential impacts to human health (e.g. utility workers) by
direct contact with contaminated groundwater is required. Concentrations in groundwater
were evaluated and found to be below the groundwater contact criteria, thus this potential
exposure route will not be further addressed. Likewise, an evaluation of potential indoor-air
impacts due to underlying soils and/or groundwater was also done, and it was determined
that levels were below the preliminary screening limits, thus this potential route also does
not need to be addressed further at this time.
The change in these State of Michigan cleanup standards essentially changes the
groundwater cleanup values to be equivalent to the Federal Maximum Contaminant Levels
(MCLs).
VIII. Development of Remedial Action Alternatives
Two general alternative cleanup methods were evaluated. Alternative 1 provided for
containment of the contaminated soil and ongoing extraction of contaminants. Alternative 2
provided for excavation and treatment of the soils above-ground. This section describes these
alternative cleanup strategies. The petitions dated April 26,1995, and July 8,1996, describe in
much more detail the variations on the alternatives.
Alternative 1 - Dual-Phase Vacuum Extraction and Encapsulation
Dual-phase vacuum extraction and encapsulation involves containment of contaminated soils
within a treatment cell and vacuum extraction of contaminated water and vapors from those
soils. Contaminated soil would be excavated and consolidated in the treatment cell. The
treatment cell would be surrounded by a vertical barrier or slurry cutoff wall extending down to
the impermeable till located 10 to 20 feet below the ground.
A cap which is equivalent to those required for a Michigan solid waste landfill, and acceptable tc
EPA and MDEQ, would be installed over top of the treatment cell. The components of a cap
generally will include an infiltration layer consisting of a minimum of 18 inches of earthen
material, and an erosion layer immediately above the composite liner which is not less than 2
feet thick, which provides for lateral drainage off the cover by use of permeable soil or
geosynthetic drainage material, or a combination of both; and 6 inches minimum of earthen
material which will sustain plant growth, to protect the flexible membrane liner.
A ground water monitoring system would be installed. Deed restrictions would be placed on the
Ex-Cell-O facility that would provide for the control of any future construction, excavation or well
installation activities within the encapsulated area. Access restrictions may also be required to
minimize and restrict future admittance to the encapsulated area. The property would be
maintained by the PRP group for as long as necessary.
Capital Cost: $ 1,361,200
30 yrs. Operation & Maintenance $ 987,500
Total Present Worth: $ 2.348.700
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Alternative 2 - Soil Excavation and On-Site Treatment
Under this alternative, the contaminated soil would be excavated to a maximum depth of 25 feet
The excavated soil would be preprocessed to break the soil into treatable sized particles.
Preprocessed soil would be treated using one of 3 treatment processes on site:
Alternative 2A - Low Temperature Thermal Desorption (LTTD): The temperature in and around
the soil is raised to a temperature greater than the boiling point of the contaminants. This
changes the phase of the constituents adsorbed on the soil from liquid to vapor and the vapors
are carried out of the soil treatment unit under a vacuum for further treatment.
Alternative 2B - Ex situ Soil Vapor Extraction: This option would require that a bulking agent
such as gypsum, fly ash, or sand be mixed with the soil to increase the pore space and
permeability. The soil would then be placed on a pad and air would be drawn through the soil to
remove the VOCs.
Alternative 2C - Chemical Oxidation: VOCs would be completely destroyed through a chemical
reaction.
Each of the above treatment options may require air quality controls for VOC emissions during
the cleanup. The excavated areas would be backfilled and revegetated following laboratory
confirmation that the cleanup levels have been reached.
2A 2B 2C
Capital Costs: $3,191,000 $3,371,000 $4,009,000
O&M: 25,300 117,800 25,300
Total Present Worth: $4.179,000 $3.903,000 $4,248,000
IX. Evaluation of Alternatives
A. Evaluation Criteria
EPA's evaluation of remedial alternatives is based on the nine criteria set forth in the
National Contingency Plan (NCP), 40 CFR Part 300. These criteria are described below.
A remedial alternative is first judged in terms of the threshold criteria of protecting human
health and the environment and complying with Applicable or Relevant and Appropriate
Requirements (ARARs). If a proposed remedy meets these two criteria, it is then
evaluated against the balancing and modifying criteria in order to arrive at a final
recommended alternative.
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Threshold Criteria
1. Overall protection of human health and the environment: USEPA determines whether
an alternative adequately protects human health and the environment from unacceptable
risks posed by hazardous substances, pollutants, or contaminants present at the site.
2. Compliance with ARARs: USEPA evaluates whether an alternative attains applicable
or relevant and appropriate requirements under federal environmental laws and state
environmental or facility siting laws or provides grounds for invoking a waiver.
Balancing Criteria
3. Long-term effectiveness and permanence: USEPA considers the ability of an
alternative to maintain protection of human health and the environment over time, and the
reliability of such protection.
4. Reduction of contaminant toxicity. mobility, or volume through treatment: USEPA
evaluates the degree to which an alternative uses treatment to address the principal
threats posed by the site.
5. Short-term effectiveness: USEPA considers the length of time needed to implement
an alternative and the risks the alternative poses to workers, residents, and the
environment during implementation.
6. Implementability: USEPA considers the technical and administrative feasibility of
implementing the alternative, such as relative availability of goods and services.
7. Cost: USEPA estimates an alternative's capital and O&M costs and calculates the
present worth cost. Present worth cost is the total cost of an alternative over time in terms
of today's dollars.
Modifying Criteria
8. State acceptance: USEPA considers any concerns the state has raised with respect to
the preferred alternative, other alternatives or with ARARs or ARAR waivers.
9. Community Acceptance: USEPA considers which components of the alternatives
interested persons in the community support, have reservations about, or oppose.
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B. Application of the Evaluation Criteria to the two
Cleanup Alternatives
1. Overall Protection of Human Health and the Environment
All the alternatives evaluated here would reduce the amount of volatile organic
compounds (VOCs) that are available to leach into groundwater. If not addressed, these
VOCs will continue to leach into groundwater threatening the City of Clare's water supply.
Given the proper implementation of monitoring programs for these alternatives, they will
be protective of human health and the environment.
Alternative #1 - Consolidation and on-site containment of VOC impacted soil within a low
permeability cell on the western portion of the Ex-Cell- facility would isolate these soils
from the surrounding environment. Until such time as the encapsulated soil has been
treated by both natural and physical means to the soil performance standards, the
isolation of the soils would be insured by a maintenance and monitoring program and
institutional controls.
Alternative #2 - Excavation and treatment of contaminated soils would remove the
contaminants from the soils more completely than under alternative #1. Under this
alternative, excavated areas could be backfilled with clean soils without a containment cell
being necessary.
Both alternatives are protective of human health and the environment.
2. Compliance with ARARs
Part 201 of the Natural Resources and Environmental Protection Act (NREPA) 1994 P.A.
451 as amended (formerly known as Michigan Environment Response Act) contains
promulgated cleanup standards for both soil and groundwater. Part 201 also allows for
institutional controls to prevent exposure to contaminated materials in the event that
cleanup standards may not be attained or in lieu of treatment. Part 201 also requires that
potential groundwater impacts via direct contact be addressed, as well as an evaluation of
indoor-air impacts due to contaminated groundwater and soils beneath a facility. As noted
in a footnote to the Cleanup Standards table in this ROD Amendment, these potential
routes were evaluated and levels were found to be within acceptable limits.
Alternative #1 - This alternative would meet ARARs.
It would meet the soil and groundwater standards under Part 201. Groundwater would
meet chemical specific ARARs because groundwater from the perched zone within the
encapsulated area would be extracted and treated and an inward hydraulic gradient would
be maintained such that any contaminated groundwater could not migrate beyond the
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encapsulated area. The selected remedy will comply with Part 201 either by meeting the
cleanup standards or by maintaining institutional controls at the site which will prevent
exposure.
Emissions from the treatment system will be required to meet the substantive provisions of
Part 55 of Michigan's Act 451, as amended. USEPA will require monitoring of off-gas
emissions to ensure this alternative will achieve this requirement.
Some contaminants at this Site may be RCRA listed wastes. Trichloroethylene (TCE) and
tetrachloroethylene (PCE) may be RCRA listed wastes F001 and F002. For listed wastes
that were in place prior to November, 1980, excavated soils containing these wastes which
are moved from the area of contamination would trigger RCRA requirements, including
treatment and disposal requirements provided in the Land Disposal Restrictions (LDRs).
However, this is not the case if the contaminated soils are only moved within the area of
contiguous contamination. In this action, the soils from the southeastern portion of the
Mitchell facility and those from the southeastern portion of the Ex-Cell-O property will be
moved to the western edge of the Ex-Cell-O property. The soils and groundwater
underlying both the Ex-Cell-O and Mitchell facilities and all areas in between are
contaminated with varying levels of chlorinated hydrocarbons even though not all these
areas exceed the cleanup standards. Consequently, this action will result in soil
contaminated with RCRA wastes prior to 1980 being moved around within the area of
contiguous contamination and RCRA ARARs and LDR treatment standards are not
triggered.
If activated carbon is used in the soil vapor extraction system, the spent carbon is
considered to be a RCRA listed waste and must be disposed of at a Subtitle C landfill
subject to LDR treatment standards; or alternatively, if it is regenerated, this must be done
at a RCRA permitted unit in compliance with RCRA Subpart X.
Alternative #2 - This alternative would meet ARARs.
It would meet the soil and groundwater standards under Part 201. Soils would be treated
under one of three methods and the excavated areas would be backfilled with the treated
soils. Treatment of the soils will facilitate the groundwater cleanup as source areas of soil
contamination would be dealt with.
Emissions from the treatment system will be required to meet the substantive provisions of
Part 55 of Michigan's Act 451. USEPA will require monitoring of off-gas emissions to
ensure this alternative will achieve this requirement.
Some contaminants at this Site may be RCRA listed wastes. Trichloroethylene (TCE) and
tetrachloroethylene (PCE) may be RCRA listed wastes F001 and F002. Because of this,
excavated soils moved from the area of contamination would trigger RCRA requirements,
including treatment and disposal requirements provided in the Land Disposal Restrictions
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(LDRs).
3. Long term effectiveness
Both alternatives would be effective in the long term. Potential risks due to direct
contact/ingestion of soil is substantially reduced. Potential risks from impacted soil
erosion and migration and affected surface water runoff is removed. Potential risks from
chemicals in the ambient air are reduced in the long run through the containment system
and mass removal of chemicals by the dual-phase vacuum extraction system in alternative
#1 and through treatment in alternative #2. In addition, infiltration of precipitation into the
contained soil would be minimized by the cap in alternative #1.
Potential groundwater impacts would be significantly minimized in alternative #1 because
movement of any groundwater within the contained area would be prevented by the low
permeability slurry cut-off wall and the underlying low permeability till layer. Long term
monitoring of the groundwater and a cap would be required due to the continued presence
of impacted soil. The inward hydraulic gradient would be effective at ensuring that no
contaminated groundwater escapes the containment area. In alternative #2, contaminated
soil source areas would be eliminated through treatment thereby facilitating the
groundwater cleanup activities.
4. Reduction of Toxicity, Mobility or Volume through Treatment
Alternative #1 would provide for reduction of toxicity and mobility, and some reduction of
volume through treatment through dual-phase vacuum extraction of the perched aquifer
and shallow soil. Alternative #2 would provide for reduction of toxicity, mobility and
volume through treatment.
5. Short-term effectiveness
Alternative #1 would minimize potential short term exposure risk to site workers and the
community because excavation will be limited to soil at the Mitchell Facility and in the
eastern portion of the Ex-Cell-O Facility. Also, potential risk of exposure due to
preprocessing and treatment of impacted soil would be eliminated under this alternative.
Potential short term risks due to the brief (one or two months) excavation of soil at the
eastern portion of the Ex-Cell-O and Mitchell Facilities and placement of this soil at the
western portion of the Ex-Cell-O Facility could be minimized by the timing and control of
the excavation.
Worker exposure to VOCs during excavation operations would be minimized by
implementing an appropriate health and safety plan. Short term risks of exposure would
be greater with Alternative #2 as excavation and treatment activities would be more
involved and excavation activities would continue over a period of time.
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6. Implementability
Both alternatives are implementable. Alternative #1 maximizes the use of the established
physical conditions of the subject area relative to the nature and extent of VOCs and to the
soil medium in which it is present. No difficulties or uncertainties are expected during
implementation of the dual-phase vacuum extraction and encapsulation alternative.
Necessary materials, equipment, and services are readily available. Dual-phase vacuum
extraction and treatment is a proven technology for remediating VOC impacted soil and
groundwater. Slurry cut-off wall and capping technologies are proven technologies for
containing impacted soil and preventing possible migration of these impacts. Services
and materials are readily available, the selected technology is proven, reliable and can
easily be monitored, and implementation of remediation activities is administratively
feasible. In addition, this alternative is augmented by the proven technology of
groundwater pumping and treatment. Because of the depth to which contaminated soils
extend, it will be difficult to excavate all soils contaminated at levels over the cleanup level
from the Mitchell property due to practicability, however, as much soil as can be excavated
will be. Any impacted soils left in place above cleanup criteria will necessitate the use of
institutional controls to eliminate potential exposure and to comply with state law.
Implementation of Alternative #2 would be somewhat complicated because of the need to
dewater groundwater from the excavation and control dust and VOCs emitted during
excavation, handling, and preprocessing of the soil. The nature of the soil may extend the
anticipated treatment period for the soil. The maintenance of a small particle size would
be crucial to the performance of soil treatment. The soil would have to be amended with
soil additives which will enhance porosity and maintain an acceptable particle size. This
would facilitate the achievement of this alternative to meet the estimated time frame and
required cleanup standards. Maintenance of low soil moisture content would also be
important due to the relatively high solubility of the VOCs. The consequent penetration of
VOCs into the soil pore volume in fine fraction soil would impact the treatment period.
7. Cost
The capital cost for construction of alternative #1 is $ 1,361,200 with an annual O&M cost
of $75,000 which yields a Total Present Worth of $ 2,348,700. The capital cost of
construction of alternative #2 ranges from $ 3,191,000 to $ 4,009,000 with annual O&M
costs ranging from $25,300 to $117,000 which yields a Total Present Worth ranging from
$ 3,903,000 to $ 4,248,000.
8. State Acceptance
State concurrence with the ROD Amendment is anticipated.
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9. Community Acceptance
A few comments were received orally and in writing. These comments are addressed in
the attached response summary.
Results of Comparison Using the Nine Criteria
Both alternatives meet the two basic, threshold criteria: they both would provide for
protection of human health and the environment; and they would meet state and federal
ARARs.
Considering the balancing criteria, Alternative #2 is superior in terms of reduction of
toxicity, mobility and volume through treatment since it would destroy most of the
contaminants found at the site. Alternative #1 would transfer the VOCs to a different place
and, to a lesser degree, treat the contaminants in the consolidated soil. Alternative #1 is
clearly superior in terms of cost - it could be as much as $2 million cheaper than
Alternative #2 and nearly $4 million cheaper than the previously selected alternative in the
September 16,1992 ROD. Alternative #1 is preferable in terms of short-term
effectiveness since it would take less time. The kinds of nuisance problems associated
with both remedies - dust, noise, etc. - would not last as long under Alternative #1 as they
would under the on-site treatment remedy. Alternative #2 is preferable in terms of long-
term effectiveness because it eliminates the need for an on-site treatment cell. In terms of
Implementability, the two alternatives appear equally implementable.
USEPA is mindful that the balancing criteria should not be assigned equal weights. Since
CERCLA contains a preference for treatment over land disposal of contamination, the
reduction of toxicity, mobility and volume criterion must be given more weight than the
other balancing criteria. Even so, USEPA believes that, in this case, the scales tip toward
Alternative #1. USEPA has concluded that the differences in effectiveness provided in
Alternative #2 is not proportional to the great increase in cost over Alternative #1. The
final step in the comparison is to consider the two modifying criteria: state and community
acceptance. Based on comments received from the Michigan Department of
Environmental Quality and the public, USEPA has concluded that the state and community
support the change in the remedy. USEPA has therefore decided to change the soil
component of the remedy by amending the 1992 ROD and selecting Alternative #1.
X. The Selected Remedy
The new soil component of the remedy for the Clare Water Supply Site is Alternative #1
dual-phase vacuum extraction and encapsulation of VOC-contaminated material in a
treatment cell on the western portion of the Ex-Cell-O facility. The main elements of the
selected remedy are as follows:
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o Excavation of contaminated soil from the Mitchell facility and the eastern portion of the
Ex-Cell-O facility.
o Consolidation of excavated materials on the western portion of the Ex-Cell-O facility.
o Construction of a vertical barrier or slurry cutoff wall extending down to the
impermeable till located 10 to 20 feet below the ground around the area on the
western portion of the Ex-Cell-O facility which is to be the "treatment cell".
o Construction of a cap which is equivalent to that required for a solid waste landfill in
Michigan over top of the treatment cell. The components of an acceptable cap are
specified in the detailed description of the alternative (see note above). Further, as
long as material above the established cleanup standards remains in place
(regardless of whether or not the dual-phase system is operating), the containment
cell will be required to be properly operated and maintained in a manner acceptable to
the USEPA. in consultation with MDEQ.
o Dual-phase vacuum extraction of contaminated soils within the treatment cell.
o Installation of a ground water monitoring system.
o Maintenance of an inward hydraulic gradient within the treatment cell.
o Placement of Deed restrictions on the western portion of the Ex-Cell-O facility that
would provide for the control of any future activities within the encapsulated area.
o Access restrictions may also be required to minimize and restrict future admittance to
the encapsulated area.
o Air monitoring and dust suppression during remedial activities.
o Continuous operation of the vacuum extraction system until asymptotic conditions are
achieved in the extracted soil vapors; or until operation of the system provides limited
or no effect on the degradation or removal of the constituents of concern remaining
within the encapsulated area. After this period, pulsed operation of the system shall
be performed until it can be shown that the system will not provide any further removal
of contaminants from the encapsulated area.
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XI. Statutory Findings
Section 121 of CERCLA requires the Agency to select remedies that:
1. Protect human health and the environment;
2. Comply with ARARs (or meet the conditions necessary to justify a waiver);
3. Are cost effective;
4. Utilize permanent solutions and alternative treatment technologies to the maximum
extent practicable; and
5. Satisfy a preference for treatment as a principal element of the remedy.
The implementation of the amended remedy at the Clare Water Supply Site satisfies these
requirements as follows:
1. Protection of Human Health and the Environment
Removal of contaminated soil and debris and encapsulation in an on-site treatment cell
will significantly reduce these risks. No unacceptable short-term risks will be caused by
implementation of the remedy. Measures will be taken to minimize the noise and dust
caused by remedial activities. The selected amendment will be protective of human health
and the environment.
2. Attainment of Applicable or Relevant and Appropriate Requirements
The selected remedy will meet all applicable or relevant and appropriate requirements
(ARARs).
a. Chemical-specific ARARs
NREPA. - Cleanup Criteria established pursuant to Part 201 of Michigan's Natural
Resources and Environmental Protection Act (NREPA) 1994 P.A. 451, as amended
(formerly known as the Michigan Environmental Response Act), are applicable to the
Clare Water Supply Site. The cleanup levels established for groundwater in this ROD for
specific chemicals are consistent with these criteria which, in turn, are consistent with the
federal Safe Drinking Water Act.
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b. Action-specific ARARs
Air Emissions
Part 55 of Act 451 - Michigan air pollution standards pursuant to Part 55 of Act 451 are
applicable to activities at the Clare Water Supply Site which will have air discharges.
RCRA
The consolidation of waste, as long as it is within the area of contiguous contamination,
meets the requirements of the Resource Conservation and Recovery Act, as amended.
3. Cost Effectiveness
The on-site encapsulation alternative is approximately $2 million less to construct than
alternative #2 and it provides for treatment of contaminated soil in that the dual-phase
vacuum extraction system can be operated whenever necessary to reduce the levels of
VOCs in the treatment cell. The on-site treatment alternative #2 does provide for a greater
level of treatment but it is uncertain whether this alternative could effectively address the
soils located at 25 feet depth (15 feet below the water table) whereas the alternative #1
may extract these contaminants through time.
4. Utilization of Permanent Solutions and Alternative Treatment Technologies or
Resource Recovery Technologies to the Maximum Extent Practicable
The preamble to the current version of the NCP discusses how to evaluate the
practicability of treatment:
Cost differences must also be considered in the context of all other differences
between alternatives to reach a conclusion as to which alternative, all things
considered, provides the most appropriate solutions for the site or site problem. It
is this judgement that determines the maximum extent to which permanent
solutions and treatment are practicable for the site or site problem being
addressed. (54 FR 8729)
In this case, the combination of the lower cost of on-site encapsulation and treatment
together with the advantage of eliminating on-site treatment facilities made on-site
encapsulation and treatment the most appropriate solution for the site. Treatment and
permanent solutions in excess of those called for in the amended remedy are not
practicable.
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5. Preference for Treatment as a Principal Element of the Remedy
In comparing alternatives, USEPA did give preference to treatment. That is, USEPA
assigned greater weight to the treatment criterion than to the other balancing criteria.
However, because of the magnitude of the difference in cost, the on-site encapsulation
and treatment alternative overcame the preference for treatment offered by the other
alternative. Because this remedy will result in hazardous substances remaining on-site
during treatment, a review of the status of the remedy will be conducted within five years
of commencement of the remedial action to ensure that the remedy continues to provide
adequate protection of human health and the environment.
William E. Muno, Director Date
Superfund Division
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