PB97-963102
                                 EPA/541/R-97/004
                                 November 1997
EPA   Superfund
       Explanation of Significant Difference
       for the Record of Decision:
       PSC Resources,
       Palmer, MA
       11/26/1996

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           FINAL EXPLANATION OF SIGNIFICANT DIFFERENCES AND
         DESIGNATION OF CORRECTIVE ACTION MANAGEMENT UNIT

I.     INTRODUCTION
                                                                       J
      A.     Site Name and Location                                            	

      Site Name:          PSC Resources Superfund Site
      Site Location:        Hampden County, Massachusetts

      B.     Lead and Support Agencies

      Lead Agency:        United States Environmental Protection Agency (EPA)

             Contact:      Don McElroy, RPM
                          (617)223-5571

      Support Agency:     Massachusetts Department of Environmental
                          Protection (MA DEP)

             Contact:      Harish Panchal
                          (617)556-1118


      C.     Summary of Significant Differences

             The September 15, 1992 Record of Decision (ROD) called for in-situ mixing and
             stabilization of contaminated soils and sediments, consolidation of these materials
             with lagoon and wetland sediments on site property and capping with a permeable
             cap.  During the design process, studies showed that an ex-situ stabilization
             process would be more effective in the short term and less expensive than in-situ
             stabilization. These studies also showed that a low permeability cap would be more
             effective over the long term and comparable in cost to the permeable cap planned
             in the ROD

             Additionally, cleanup levels that appear in the ROD for lagoon sediment are based
             on non-promulgated Maximum Contaminant Levels (MCLs). Since the MCLs
             were only proposed and not promulgated, corrections were made, based on human
             health risk, to the cleanup values for 1,1-dichloroethane and acetone


      D.     Legal Authority for ESD

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       Section 117© of the Comprehensive Environmental Response, Compensation and
       Liability Act (CERCLA) requires that, if any remedial or enforcement action is
       taken under Section 106 of CERCLA after adoption of a final remedial action plan,
       and such action differs in any significant respects from the final plan, the EPA shall
       publish an explanation of the significant differences (ESD) and the reasons such
       changes were made  In accordance with Section 117(d) of CERCLA, the final
       ESD will become part of the Administrative Record which is available for public
       review at both the EPA Region I Record Center in Boston, Massachusetts and the
       Palmer Public Library in Palmer, Massachusetts (see Section VI for addresses and
       phone numbers)

E.     Summary of CAMU Designation

       EPA is designating a Corrective Action Management Unit (CAMU) for this site
       A CAMU designation is needed for this site to allow temporary storage,
       stabilization and placement of excavated contaminated materials without  triggering
       the Land Disposal Restrictions (LDRs) and Minimum Technology Requirements
       (MTRs) intended for hazardous process wastes  The CAMU will facilitate the
       cleanup plan which addresses contamination at the site.  The CAMU covers an
       area within the PSC Site, including excavation areas, the cap area, the processing
       area and the staging area (collectively referred to as the  Remedial Action Area)
       The CAMU is shown on Figure 1.

F.     Legal Authority for CAMU Designation

       Regulations found at 40 C.F.R. § 264.552 establish requirements for Corrective
       Action Management  Units (CAMU) for placement of "remediation wastes",  as
       defined in 40 C.F.R.  § 260.10.  Pursuant to the CAMU regulations found at  §
       264.552, certain activities which would normally constitute "placement", and thus
       trigger applicability of the land disposal restrictions (pursuant to 40 C F R Part
       268), are allowed when carried out in an Agency-approved CAMU, including that
       remediation waste can be removed from a CAMU and replaced (before or after
       treatment) in the same or a different CAMU, and remediation waste can be
       consolidated into a CAMU before  or after treatment  The CAMU regulations
       allow federal or state officials to designate an area of a facility as a CAMU, and
       specify that placement of cleanup wastes into a CAMU does not trigger land
       disposal restrictions that would otherwise apply

       The CAMU regulations have been challenged in federal  court in Environmental
       Defense Fund vs. EPA. No. 93-1316 (DC Cir, 5/14/93). In response, EPA, on
       April 29, 1996, has issued for public comment a proposed rule which, if it were to
       become final, would  change CAMU, and possibly trigger the land  disposal

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             restriction regulations in more remedial actions. ("Requirements for Management
             of Hazardous Contaminated Media [HWIR-media] Proposed Rule")  The
             proposed rule was issued for 120 days public comment, and a public hearing was
             held June 4, 1996. The proposed rule states that all CAMUs approved at the time
             of publication of any final HWIR-media rule would be retained.

             On  March 13, 1996, EPA issued the following guidance: Use of the Area of
             Contamination (AOQ Concept During RCRA Cleanups  In this guidance, EPA
             states that as long as the CAMU rule remains in effect, CAMUs may be used to
             facilitate protective remedies under CERCLA

II.     SUMMARY OF SITE HISTORY, CONTAMINATION, AND SELECTED
       REMEDY

             A.     Site History and Contamination

             The PSC Resources Site is located on Water Street in Palmer, Massachusetts  The
             record of ownership at the site, as described in the Remedial Investigation (RI)
             Report, indicates that the property was owned by various oil companies from 1898
             to 1974  In 1974, PSC Resources, Inc. purchased the property to operate a waste
             oil and solvent recovery facility.  In  1974, the Massachusetts Department of
             Environmental Protection (DEP, formerly the Massachusetts Department of
             Environmental Quality Engineering)  issued  a permit for collection and storage of
             waste oil materials  In 1976, this permit was amended to change the owner of the
             property and to allow for the collection and disposal of "solvent, lacquers, etc
             The facility reportedly operated until 1977 or 1978 when the permit was not
             renewed and removal actions were initiated

             During the period from 1974 to 1977, the DEP conducted several property
             inspections and discovered several violations including improper maintenance and
             spills of waste oil and hazardous materials.  In January of 1978,  DEP  initiated
             enforcement actions against the owners resulting in a closing of the facility m
             1978.  DEP then issued a Notice of Responsibility to the current owner requiring
             removal of approximately 1.5 million gallons of waste materials stored on the
             property.  Initial removal activities were conducted by private firms and, by mid-
             1980, an estimated one quarter to one million gallons of waste material had been
             reportedly removed from the property.

             As  a result of the limited progress made in cleanup and removal of wastes
             following DEP's initial request in  1978, the state requested assistance from the
             federal government through the Superfund  Program in 1982  At that time, an
             estimated 500,000 gallons of waste materials remained on the property  State MIC

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      inspections revealed evidence of oil discharges to the adjoining wetlands, as well as
      leakage of waste materials from the dikes on the property into the wetlands
      Subsequent sampling programs performed by various investigators indicated
      elevated levels of polychlorinated biphenyls (PCBs), trichloroethylene (TCE), lead,
      and other hazardous materials primarily in soils and surface waters on the site
      Based on this information, state enforcement actions were initiated against  the
      Potentially Responsible Parties (PRPs) requiring the removal of wastes and
      cleanup of the site

      In September, 1983, the site was listed on EPA's National Priorities List (NPL)
      making it eligible for Superfund funding.  Between 1988 and  1992, the Remedial
      Investigation and Feasibility Study (RI/FS) were conducted for the site   EPA
      issued a Record of Decision (ROD) on September 15,  1992 selecting the Source
      Control and Management of Migration remedies for the site (see Section II B  for
      a description of the selected remedy).

      Contaminants of concern (COCs) in the groundwater include: bis(2-
      ethylhexyl)phthalate, vinyl chloride, methylene chloride, trichloroethene,
      tetrachloroethene, benzene, lead, acetone, 2-butanone (MEK), and 1,1,1-
      trichloroethene  Contaminants of concern in soils and sediments include: PCBs,
      lead,  arsenic, and polynuclear aromatic hydrocarbons (PAHs)

      In September, 1993, EPA and DEP initiated negotiations with the PRPs at the site
      resulting in signing of a Consent Decree (CD) in September,  1994  Under this
      CD, the Settling Defendants agreed to perform the selected remedy.

      During 1995, O'Brien & Gere, Inc  under contract to the Settling Defendants
      initiated a quarterly groundwater, surface water and sediment monitoring program
      In addition, further sampling to "fine tune" the limits of the impacted areas was
      performed.  Wetland and lagoon sediment, surface soil, and subsurface soil were
      sampled and analyzed as part of investigations for the 30% Remedial Design   As
      part of remediation activities, on-site buildings and structures were
      decontaminated, demolished, and removed from the site

B.    Summary of the Selected Remedy

      The major components of the source control remedy selected in the ROD include
             Decontamination, demolition, and off-site disposal of property structures.
             Treatment and discharge of lagoon surface water
             Consolidation of contaminated property soils with lagoon and wetland
             sediments on site property;

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             •      In-situ mixing and stabilization of property soils/sediments with treatment
                    agents to bind contaminants into a stable matrix;
             •      Construction of a permeable cap over stabilized property soils and
                    sediments, and grading and planting of the cap's surface,
             •      Restoration of wetlands;
             •      Implementation of institutional controls on groundwater use and land
                    development, and
             •      Long-term monitoring of groundwater, wetland sediments, and Quaboag
                    River water and sediments

             The major components of the management of migration remedy selected in the
             ROD include:
             •      Use of natural attenuation to achieve groundwater cleanup levels,
             •      Groundwater monitoring of existing wells on the PSC Resources, Inc
                    property and of monitoring wells adjacent to the property,
             •      Sediment sampling of portions of the wetland and the Quaboag River,
                    where groundwater discharges to the wetland and the Quaboag River,
             •      Surface water sampling in areas adjacent to the wetland and in the
                    Quaboag River; and
             •      Five-year site reviews to assess site conditions, contaminant distributions,
                    and any associated site hazards.

ffl.    DESCRIPTION OF CAMU AND SIGNIFICANT DIFFERENCES AND THE
       BASIS FOR THESE DIFFERENCES

       A.    Significant Differences

             1.     Ex-Situ Stabilization/Solidification

                    Ex situ stabilization of the contaminated soils and sediments is more
                    effective over the short term than in situ stabilization due to the following
                    factors:

                           - Unique stabilization mix designs are required for the soil, lagoon
                           sediment and wetland sediment;

                           - Greater chemical addition quality control is provided with ex situ
                           stabilization;

                           - Homogenization of the raw soil, lagoon sediment and wetland
                           sediment is possible;

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       - Verification sampling in the excavations to ensure that materials
       above cleanup levels are excavated;

       - Effective conditioning of the lagoon sediment is possible,

       - Use of conventional construction equipment is possible,

       - The presence of subsurface barriers throughout the areas to be
       stabilized, and

       - The likelihood that groundwater dewatering will not be needed
       during ex situ  stabilization.

Each of these factors is discussed in more detail below.

In-situ stabilization entails combining the contaminated material and the
stabilization mix in-place or without excavation.  Ex-situ stabilization
entails excavation of the contaminated material prior to combining with the
stabilization mix. The Treatability Study conducted as part of the Remedial
Design indicated that, due to the variability of the chemical and physical
properties of the various media at the site, a unique mix design should be
used to solidify and stabilize each medium.  Excavation of a particular site
medium with subsequent processing by ex situ stabilization allows the
utilization of different mix designs for each site medium.

The use of ex-situ stabilization processing techniques also provides greater
quality control for the stabilization process  Chemical addition rates and
mixing efficiency can be monitored more closely using ex-situ stabilization
processing techniques such as mobile mixing plants and area mixing and
layering. Ex situ stabilization also allows for verification sampling in the
excavations to ensure that the soil, and lagoon and wetland sediments with
concentrations above  cleanup levels are stabilized

In addition,  although the effectiveness of ex situ stabilization  could be
adversely affected by  heterogeneous feed material, excavation of site
media prior to ex situ stabilization allows for additional processing steps
prior to the  stabilization to improve the  homogeneity of the feed material at
the stabilization plant  For example, excavation of site media will allow
removal of oversize material and debris  via screening and homogenizing of
influent feed size via a hammermill.  The difficulty of accounting for the
variability in the feed material could also be minimized during ex situ
stabilization because the feed material would be readily visible and perhaps

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even pre-characterized for pertinent parameters such as moisture content
and organic contaminants

Ex situ processing techniques such as mobile mixing plants and area mixing
and layering can also be operated as closed systems to allow the capture
and treatment of fugitive emissions, if necessary

Ex situ stabilization also allows for more effective conditioning of the
lagoon sediments through the addition of lime kiln  dust to improve the
workability of the sediments  This would result in  lower required dosages
of solidify agent and lower volumes of stabilized material.

In addition, the greatest depth to which media must be remediated at the
site is estimated to be no greater than six feet  This depth is well within the
limits of common excavation techniques which would be used to excavate
the material for the ex situ stabilization  The mobilization and use of in
situ stabilization would be more practical for media which extended to
greater depths and could not be readily removed by common excavation
techniques

A geophysical survey was also conducted to evaluate the presence of
subsurface barriers in the areas  to be stabilized.  This survey indicated that
subsurface barriers are pervasive and widespread throughout these areas
Since the locations of the subsurface barriers correspond to the soil  areas
to be excavated, it is not practicable to excavate the soil for purposes of
removing  subsurface barriers, and then to backfill the soil for in situ
stabilization.  Rather, it is preferable to use ex situ  stabilization techniques
after excavation of the materials

In addition, groundwater dewatering may be necessary during the
stabilization process if in situ stabilization activities are performed while the
groundwater table is above its seasonal low elevation  If the ex situ
stabilization methods are used,  dewatering  will likely not  be  necessary

Finally,  the estimated cost for ex situ stabilization is approximately
$1,000,000 less than in situ stabilization. This cost decrease is due to the
fact that in situ stabilization  requires the use of highly specialized
equipment and  specially trained personnel which is not  necessary for ex situ
stabilization

Based on  the rationale presented in the preceding paragraphs, EPA
concludes that ex situ stabilization of site soil, lagoon sediment, and

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       wetland sediments is preferable to the in situ stabilization techniques
       included in the ROD

2.     CAMU Designation

       A CAMU designation is needed to allow ex situ stabilization without
       triggering Land Disposal Restrictions (LDRs) and Minimum Technology
       Requirements (MTRs) intended for hazardous process wastes. The
       CAMU designation will facilitate the cleanup plan as proposed   The
       CAMU encompasses the area within the boundaries of the site which
       contain the excavation areas, the cap area, the  processing area and the
       staging area (see Figure 1).  In designating a CAMU, EPA is required to
       evaluate the application against the following seven criteria
              1) The CAMU shall facilitate the implementation of reliable.
              effective, protective, and cost effective remedies,
              2) Waste management activities associated with the CAMU shall
              not create unacceptable risks to humans or to the environment
              resulting from exposure to hazardous wastes or hazardous
              constituents,
              3) The CAMU shall include uncontaminated areas of the facility
              only if including such areas for purpose of managing remediation
              waste is more protective than management of such wastes at
              contaminated areas of the facility,
              4) Areas within the CAMU, where wastes remain in place after
              closure of the CAMU, shall be managed and contained so as to
              minimize future releases, to the extent practicable,
              5) The CAMU shall expedite the timing of remedial  activity
              implementation, when appropriate and practicable,
              6) The CAMU shall enable the use, when appropriate, of treatment
              technologies (including innovative technologies) to enhance the
              long-term effectiveness of remedial actions by reducing to\icit\
              mobility, or volume of wastes that will remain in place after closure
              of the CAMU, and
              7) The CAMU shall, to the extent practicable, minimize the land
              area of the facility upon which wastes will remain in place after
              closure of the CAMU.

       Each of these criteria is addressed below

       1.      The CAMU shall facilitate the implementation of reliable, effects c
              protective, and  cost-effective  remedies.

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              The use of ex situ stabilization, which is the reason for a
              CAMU designation, is as protective and reliable as the in
              situ stabilization selected in the ROD. In addition, based on
              the reasons discussed in  III. A. 1. above, ex situ stabilization
              is more effective over the short term and more cost effective
              than in situ stabilization.  Therefore, the designation of a
              CAMU, which is necessary to perform ex situ stabilization,
              will result in the implementation of a reliable, effective,
              protective and cost-effective remedy.

2.      Waste management activities associated with the CAMU shall not
       create unacceptable risks to humans or to the environment resulting
       from exposure to hazardous wastes or hazardous constituents

              The purpose of designating a CAMU is to allow
              performance of a cleanup plan to decrease existing risks to
              humans and the environment. The remediation will be
              conducted in such a way that it does not create additional
              risks to humans or the environment.  Air monitoring, both in
              the vicinity of the work and at the downwind perimeter
              fence,  will be conducted during all remediation activities to
              evaluate whether controls are necessary.  If it is determined
              that controls are necessary, they will be implemented

3.      The CAMU shall include uncontaminated areas of the facility, only
       if including such areas for the purpose of managing remediation
       waste is more protective than management of such wastes at
       contaminated areas of the facility.

              A small amount of uncontaminated land is included in the
              area of the CAMU  The use of these uncontaminated areas
              is necessary to perform the remedial action, which will
              decrease existing risks to humans and the environment
              Therefore, inclusion of these uncontaminated areas is more
              protective than the management of wastes only at
              contaminated areas of the facility

4.      Areas within the CAMU, where wastes remain in place after
       closure of the CAMU, shall be managed and contained so as to
       minimize future releases, to the  extent practicable.

              The stabilized soil and sediments will be consolidated wuhm

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                    the CAMU and will be protected by a cap to minimize
                    future releases.

       5.     The CAMU shall expedite the timing of remedial activity
             implementation, when appropriate and practicable.

                    The purpose of designating a CAMU is to permit the
                    implementation of the remedy as designed to date
                    Designation of this CAMU will expedite the timing of
                    remedial action implementation.

       6     The CAMU shall enable the use, when appropriate, of treatment
             technologies to enhance the long-term effectiveness of remedial
             actions by reducing toxicity, mobility, or volume of wastes that will
             remain in place after closure of the CAMU.

                    The CAMU designation will permit the use of ex-situ
                    stabilization which will reduce the toxicity and mobility of
                    wastes that will remain within the capped area of the
                    CAMU after completion of the remedial activity Ex-situ
                    stabilization, when compared to the in situ stabilization
                    selected in the ROD, also reduces the volume of wastes
                    that will remain in the capped area since it provides better
                    control of the volume of material to be stabilized

       7     The CAMU shall, to the extent  practicable, minimize the land area
             of the facility upon which wastes will remain in place after closure
             of the CAMU.

                    Soils and sediments will be stabilized and consolidated
                    within the capped area of the CAMU  at the completion of
                    the Remedial Action, thus reducing the land area upon
                    which wastes remain in place
3.     Low-permeability Cap

       As part of the 30% design, three cap systems were evaluated for the site
       one permeable cap system (as described in the ROD) and two low-
       permeability cap systems.

       The ROD selected a permeable cap as the cover for the stabilized materials

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       based on the ability of the permeable cap to reduce potential for erosion
       due to weathering of the stabilized material and for flood storage capacity
       These functions would also be provided by a low permeability cap

       One concern with using a low permeability cap is whether this type of cap
       would result in decreased flood storage capacity.  However, design studies
       indicated that the flood storage capacity is minimally affected by the type of
       cap constructed  The component that makes the low-permeability cap less
       permeable is the geomembrane liner, not the soil layers above the liner
       The cap volume available for flood storage in both the permeable and low-
       permeability designs is in the soil layers above the relatively impermeable
       stabilized material.  The storage capacity of these soils is primarily based on
       the porosity of soil. Typically, the porosity of a silty sand and gravel
       ranges between 12% and 46%, the porosity of a barrier protection layer,
       which is generally silty sand, ranges between 23% and 47% (Holtz and
       Kovacs, 1981)  Based on these ranges of porosity, the storage capacity of
       the permeable and low-permeability cap configurations is similar, with the
       low-permeability cap storage capacity being slightly higher. Therefore,
       both the permeable and low-permeability caps discussed provide similar
       storage capacity for flood water.

       During the 30% Remedial Design, performance of the cap system
       alternatives was evaluated based on infiltration rates through the stabilized
       material as predicted by the USEPA HELP model version  301  The
       HELP model is based on climatological and soil data as well as specific
       characteristics of the site. Based on the results of this model, the low-
       permeability cap configurations would reduce the potential for erosion of
       the stabilized materials. A low-permeability cap would, therefore, enhance
       the long-term effectiveness of the stabilization system  In addition, there
       are no drawbacks to using a low-permeability  cap at the site

       The cost difference between a low permeability cap and a permeable cap is
       insignificant.

       Based on the above information, EPA concludes that a low permeability
       cap will be more effective in the long-term and is therefore preferable to
       the permeable cap described in the ROD.
4.     Cleanup Levels for Lagoon Sediments

       Lagoon sediment cleanup levels for 1,1-dichloroethane and acetone have

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             been recalculated based on appropriate ground water maximum
             contaminant levels (MCLs),  3,600 ppb and 3,500 ppb respectively  As part
             of the Feasibility Study, Summer's leaching model was used to determine
             the concentration of a contaminant in soils or soil cleanup level which
             corresponds to a concentration in ground water at or below MCLs,
             MCLGs, or risk based concentrations for contaminants of
             concern(appendix F of the FS). However, proposed Massachusetts MCLs,
             rather than promulgated MCLs, were used to calculate 1,1-dichloroethane
             and acetone cleanup levels for property soils and lagoon sediments   The
             recalculated lagoon sediment cleanup levels, based on promulgated MCLs,
             for  1,1- dichloroethane and acetone are 711 ppm and 50 ppm, respectively
             These modified cleanup levels for 1,1-dichloroethane and acetone in lagoon
             sediments have been included in Table I of the Remedial Design/Remedial
             Action Statement of Work.

B.     Rationale for Changes

       The Settling Parties have proposed to modify the selected remedy in order to
       improve the overall short-term and long-term effectiveness and to decrease the
       overall costs of the remedy. They have also requested the CAMU designation in
       order to facilitate implementation of the proposed changes to the remedy

       The adjustment of cleanup levels based on the MCLs is a correction of a previous
       calculation based on non-promulgated MCLs

       EPA Interim Final Guidance on Preparing Superfund Documents (OSWER
       Directive 9355 3-02) states that changes to a component of a remedy are generalK
       incremental changes to the hazardous waste approach selected for the site (i e . a
       change in timing, cost, or implementability)   An explanation of significant
       differences should be published when the differences in the remedial action
       significantly change but do not  fundamentally alter the remedy selected in the ROD
       with respect to scope, performance, or cost (40 C.F.R. Part 300)  EPA has
       determined that the revisions to the remedy described in this ESD do not
       fundamentally alter the overall approach of this remedy but, rather, are incremental
       changes to a component, of the  remedy.  Thus, consistent with the above-
       referenced guidance, it is appropriate to make these types of changes to the ROD
       through an ESD

       Furthermore, the Settling Parties  have requested the designation of a CAMU to
       allow for temporary storage, stabilization and placement of excavated
       contaminated materials without triggering the Land Disposal Restrictions (LDRs)
       and Minimum Technology Requirements (MTRs) intended for hazardous process

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       wastes. EPA has determined that the CAMU will facilitate the cleanup plan which
       addresses contamination at the site and is therefore making this CAMU
       designation

C.     ARARs analysis

       The ex situ stabilization/solidification modification referenced above in Section
       III.A.I., presents as an applicable or relevant and appropriate requirement (ARAR)
       the Resource Conservation and Recovery Act (RCRA) Corrective Action
       Management Unit requirements In the September 1992 ROD, EPA states that in
       in situ stabilization, "placement" under the land disposal restrictions of 40 C F R
       Part 268 would not occur because the wastes remain in the same area of
       contamination (AOC), and are treated in place  However, while the ex situ
       stabilization/solidification option calls for treatment  in the same AOC, the
       treatment will not be done in place but in a separate unit  By removing the soils
       for stabilization, the ex situ remedy may thus constitute "placement" under the land
       disposal restrictions.

       Therefore, an ARAR for the modified remedy is the set of regulations under
       RCRA regarding Corrective Action Management Units (CAMUs)  Under the
       CAMU regulations found at 40 C.F.R. § 264 552, certain activities which would
       normally constitute "placement", and thus trigger applicability of the land disposal
       restrictions, are allowed when carried out in an Agency-approved CAMU,
       including that remediation waste can be removed from a CAMU and replaced
       (before or after treatment) in the same or a different CAMU, and remediation
       waste can be consolidated into a CAMU before or after treatment  The CAMl
       regulations allow federal or state officials to designate an area of a facility as a
       CAMU, and specify that placement of cleanup wastes into a CAMU does not
       trigger land disposal restrictions that would otherwise apply

       Contemporaneous with this Final Explanation of Significant Differences. EPA is
       designating an area of the PSC Resources Site (which includes the site propcru
       and adjacent wetland spill area, and was  delineated based on the areal extent of
       contiguous contamination) as a Corrective Action Management Unit Pursuant M
       a CAMU designation, the ex situ stabilization/solidification can take place for the
       Site without triggering the land disposal  restriction requirements found at 40
       C.F.R. Part 268  To the extent that ex situ stabilization/solidification presents
       unit-specific ARARs not already addressed in the ROD or this ESD, the remedial
       action will comply with such requirements

       The ex situ stabilization/solidification also raises one other factor which EPA has
       considered.  Specifically, the CAMU regulations have been challenged in federal

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             court in Environmental Defense Fund v  EPA. No  93-1316 (DC Cir., 5/14/93)
             In response, EPA, on April 29, 1996, has issued for public comment a proposed
             rule which, if it were to become final, would change CAMU, and possibly trigger
             the land disposal restriction regulations in more remedial actions. ("Requirements
             for Management of Hazardous Contaminated Media [HWIR-media]: Proposed
             Rule"). The proposed rule was issued for 120 days public comment, and a public
             hearing was held June 4, 1996.

             The Region has considered this proposed rule in developing this ESD While the
             potential for a change in the CAMU regulations is significant, the Region believes,
             on balance, it is appropriate to proceed with the PSC Resources Site remedial
             action based on the current CAMU regulations. We do not know when, or if,  the
             proposed rule will be approved as a final rule.  Also, we do not know if any final
             rule will eliminate or modify the CAMU regulations in a manner which would
             affect the Site remedial action. Moreover, the Region has a strong interest in
             proceeding with cleanup progress at the Site, such interest would not be served by
             awaiting final action on the proposed rule. Furthermore, the March 13, 1996 EPA
             guidance, Use of the Area of Contamination (AOC) Concept During RCRA
             Cleanups, states that as long as the CAMU rule remains in effect, CAMUs may be
             used to facilitate protective remedies under CERCLA.

             For these reasons, the Region will not be following the proposed rule on
             Requirements for Management of Hazardous Contaminated Media, but rather will
             follow substantively the current regulations on Corrective Action Management
             Units.

IV.    SUPPORTING AGENCY COMMENTS

       In an August 16, 1996 letter to EPA, MA DEP expressed its agreement with the ESD and
       CAMU designation
V.     STATUTORY DETERMINATIONS

       This Final ESD documents the EPA's modification of the ROD to use ex situ stabilization
       techniques rather than in situ techniques, to construct a low-permeability cap over the
       stabilized materials rather than a permeable cap, and to revise cleanup levels based on
       promulgated MCLs

       EPA believes that the remedy as modified herein remains protective of human health and
       the environment, complies with all Federal and State requirements that are applicable or
       relevant and appropriate to this remedial action, and is cost effective

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       Furthermore, this CAMU designation facilitates the cleanup plan which addresses
       contamination at the site EPA believes that this CAMU will expedite the implementation
       of a reliable, effective, protective and cost-effective remedy and will not create
       unacceptable human health or environmental risk.

VI.    PUBLIC RECORD

       In accordance with Section 117(d) of CERCLA, this Final ESD and CAMU designation
       are part of the Administrative Record File, which is available for public review at the two
       locations listed below at the given times:

             EPA Region I Records Center
             90 Canal Street
             Boston, Massachusetts 02114
             (617)573-5729
             Monday - Friday: 10:00 a.m. - 1:00 p.m.
                              2:00 p.m. - 5:00 p.m.

             Palmer Public Library
             455 N. Main Street
             Palmer, MA 01069
             (413)283-3330
             Monday-Thursday:  10:00 a.m. - 8:00 p.m.
             Friday            10:00 a.m. - 5:00 p.m.

VII.   PUBLIC PARTICIPATION ACTIVITIES

       Notice and information regarding these proposed changes to the ROD and the proposed
       CAMU designation were disseminated by (1) a mailing to all parties on the Community
       Relations Mailing List and to all Potentially Responsible Parties and (2)  publishing a notice
       of availability and a brief description of the Draft ESD and proposed CAMU designation
       in the local newspaper,  The Springfield Union News.  In addition, the draft ESD and
       CAMU proposal was made available as part of the Administrative Record for this matter.
       which is available for public review at the locations and times stated in Section VI  of this
       document.  EPA conducted a public comment period on these proposals from September
       9, 1996 to October 9, 1996 During this public comment period, EPA received one
       comment letter.  The comments contained in this letter as well as responses to the
       comments, are included in this document as Appendix I. A public meeting was requested
       and held on November  19,  1996 at the Palmer Town Hall, as part of the agenda of the
       Palmer Conservation Commission.

       After review of all  comments received during the public comment period, EPA has

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       determined that no significant new information was presented that would necessitate
       modification of the proposed changes in the ESD or the CAMU designation

VIII.   REFERENCES

Holtz, R.D., and Kovacs, W.D., 1991. An Introduction to Geotechnical Engineering, Prentice-
Hall, Inc. Englewood Cliffs, New Jersey, pp. 104-105
Emda M. Murphy, Director '                           Date
Office of Site Remediation & Restoration
EPA-New England
                                         16

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IX. DESIGNATION OF CORRECTIVE ACTION MANAGEMENT UNIT

Based on information presented in this Final Explanation of Significant Differences and
Designation of Corrective Action Management Unit, in the September 1992 Record of Decision
for the Site, and in remedial design documents in the Site Administrative Record, I make the
following findings:

       1.  In accordance with 40 C.F.R. § 264.552(b)(l),  the Site remedial action will comply
       with state and federal requirements for closure and post-closure under 40 C.F.R. Part 264,
       Subpart G, and that inclusion of the regulated unit  will enhance implementation of
       effective, protective and reliable remedial actions for the Site,

       2.  The Corrective Action Management Unit (CAMU) proposed for this Site, as described
       more fully in Section III of this document, is in accordance with the criteria for
       designation of a CAMU found at 40 C.F.R.  § 264  552(c), and

       3.  This Final Explanation of Significant Differences and Designation of Corrective Action
       Management Unit, the September 1992 Record of Decision, and the remedial design
       documents found in the Administrative Record for the Site, provide specification of Site
       remedial action requirements in accordance  with 40 C.F R. § 264.552(e).

Based on these findings, and on the rationale provided for designating a CAMU found in this
Final Explanation of Significant Differences and Designation of Corrective Action Management
Unit and elsewhere in the Site Administrative Record, I  hereby designate as a Corrective Action
Management Unit the area of the PSC Resources Superfund Site in Palmer, Massachusetts
described in the attached Figure  1, which includes excavation areas, the cap area, the processing
area, and the staging area.
                                                           f  n
John P. DeVillars                                       Date
Regional Administrator
                                           17

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         FIGURE 1
	B 	
         LEGENQ
         CIIAINiMK ftNCC
         PSC Rtsoumxs
         PROPCRIT aOUMOMT
             or CAMU
                   \.

     PSC RESOURCES  '
     SUPERFUNO SITE
 PALMER. MASSACHUSETTS
 AREAL CONFIGURATION
        OF CAMU
       NO I  ID SCAU
    (III NO bttl'J 003-068

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APPENDIX I

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           FINAL EXPLANATION OF SIGNIFICANT DIFFERENCES AND
         DESIGNATION OF CORRECTIVE ACTION MANAGEMENT UNIT
                          RESPONSIVENESS SUMMARY

A. COMMENTS AND EPA RESPONSES
 ESD, Section III, A
 1. Ex-situ stabilization/solidification
 a. Are more chemicals being added to the waste in order to excavate it?

      No. Excavation of contaminated soils and sediments will be accomplished via standard
      construction equipment; i.e. backhoe and dump truck.

 b. How are the lagoon sediments going to be conditioned?

      A treatability study (30% Remedial Design, Sec. 3) recommends conditioning the Lagoon
      sediments with lime kiln dust. The reason for conditioning is to improve the workability
      of  the sediments.  Essentially, this conditioning will reduce water content, help eliminate
      clumping and will ensure full mixing of the "stabilization mix" with the sediments.

 c. What are the stabilization mix designs?

      The contaminated  soils, the wetland sediments and the lagoon sediments (the
      contaminated media) exhibit different physical and chemical characteristics. The
      treatability study (30% Remedial Design, Sec 3) examined these characteristics in detail
      and came up with a suite of possible "mixes" (combinations of cement and other
      additives) which would potentially meet the performance and cleanup standards for this
      remedy. The intent of the treatability study was to find one or more mixes for each
      media, which would meet the performance standards for structural integrity, and
      contaminant mobility.

 d. Is the toxic waste leaching into the Quaboag River?

      The significant findings of the Remedial Investigation are summarized in the Record of
      Decision (ROD) pages 8-24. Discussion of findings related to the Quaboag River and
      area groundwater can be found on pages 16-18 of the ROD.  In general,  it appears (based
      on  flow patterns) that contaminated groundwater is discharging to both the wetlands
      adjacent to the Quaboag River and to the River itself. However, no contaminants were
      detected in the Quaboag River surface water samples.

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 e. Will the contaminated plume continue to be monitored?

       Yes. Groundwater surrounding the site is currently being monitored. Following
       completion of the Remedial Action, groundwater will continue to be monitored. In all
       probability, monitoring will continue for at least 30 years.

 f. How will residents and businesses be affected during the cleanup?

       Local effect of the Remedial Action should be minimal, similar to a construction project
       of equal magnitude. Aside from the transport of materials, all activities will take place
       within the Site boundaries. Materials (equipment, concrete and related material for the
       stabilization process, soils and geomembrane for the cap) will be brought in by truck at
       various stages of the Remedial Action. Noise and operating hours will be similar to other
       construction projects.

 g. What is heterogeneous feed material?

       Feed material is the contaminated soils and sediments which are to be stabilized under
       this remedy.  Feed material could also be thought of as the "raw product" in a
       manufacturing context. Heterogeneous feed material refers to size inconsistencies in
       these same soils and sediments, i.e. boulders and sand mixed together, or a lot of
       clumping.  The issue here is that the more inconsistent (heterogeneous) the feed material,
       the more difficult it is to fully mix (i.e. add the stabilization mix).

 h. How long will the cleanup take?

       O'Brien & Gere, the Remedial Design contractor, is planning on a 22 week period to
       complete the construction (stabilization and cap) and wetland restoration work. The plan
       is for the work to be completed between the Spring and Fall of 1997.

 2. CAMU designation
 a. Does the entire Superfund site become a CAMU, or just specific areas, and if so which
areas?

       Under the CAMU designation, the entire Site will be a CAMU (see Figure 1 at the end of
       the Draft ESD). On a small site like PSC Resources, this will allow some limited
       flexibility for the Construction Contractor to determine how to best handle the logistics of
       excavation, staging and materials handling with regard to the stabilization process.

 b. Will the areas within the CAMU which remain in place after the closure be managed?
By who?

       After the closure, the contaminated media (i.e. the soils, lagoon sediments and wetland

                                           2

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      sediments) will have been stabilized and capped (as discussed in the ESD and the
      Remedial Design). The Settling Defendants are performing the Remedial Action and will
      also be managing the Site after closure. This will entail groundwater and surface water
      monitoring, monitoring of sediments in wetlands and in the Quaboag River, monitoring
      of the wetlands restoration and operation and maintenance of the capped stabilized soils
      and sediments.

c. How will the soil and sediments be consolidated?

      Consolidation of soil and sediments simply means placing of the soil, lagoon sediments
      and wetland sediments together, in the same location.

d. Where will the waste be located after it is transferred?

      The waste will be located within the designated CAMU. The construction/remediation
      contractor would indicate in their work plans, the temporary storage location and the
      location where mixing of contaminated media will take place.  Following stabilization the
      treated material will be located under a cap as discussed in the response to Question tf 3b.

e. How long is " temporary storage" ?

      The period of temporary storage is planned for a maximum of 9 weeks. As the soils,
      wetland sediments and lagoon sediments will be handled separately with respect to
      stabilization, the storage period for each media prior to treatment (stabilization) will be
      less than 9 weeks.

f. Will the site still have Superfund designation?

      PSC Resources will remain a Superfund Site at least until the Interim Cleanup Levels for
      groundwater have been met.  A CAMU designation has no impact with regard to
      Superfund status.

g. If the site is designated a CAMU, will federal funding be affected?

      A CAMU designation would have no impact on federal funding.  The remedy for the
      PSC Resources is being paid for by the Settling Defendants with oversight by EPA and
      the State (which the Settling  Defendants are also paying for).

3. Low permeability cap
a. What is a geomembrane liner?

      The geomembrane liner is constructed of 60 mil (1.5mm) HOPE (high density
      polyethylene).  Typically, the geomembrane portion of a cap consists of many HOPE

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       panels or sheets with the seams between panels welded together to prevent leakage..

 b. Where will the cap systems be located?

       The cap which covers the stabilized soil and sediments will be located over the area
       where most of the lagoon sediments and soils were excavated from. This can be seen on
       drawing G-3 of the 60% Remedial Design.

 c. How "low" is the low permeability of the cap?

       Geomembrane liners are essentially impermeable.  One normally does not even see
       permeability specifications associated with them in construction specifications. In
       industry literature, permeability rates associated with geomembrane liners of 10(-12)
       cm/sec have been observed.

 4. Cleanup Levels for Lagoon Sediments
 a. Why is there such a huge range between the proposed and promulgated
MCL's for 1,1-dichloroethane and acetone?

       The referenced proposed MCL's never were promulgated. If EPA were setting cleanup
       levels for groundwater today, the 3,600 ppb and 3,500 ppb for 1,1-dichloroethane and
       acetone respectively, would still be appropriate. To clarify the use of MCL's in this case,
       MCL's (cleanup levels for groundwater) have been used to calculate cleanup levels in
       sediments. The intent of this is to determine what cleanup level in sediments must be
       achieved in order to ensure that groundwater does not become contaminated above MC'I.s
       due to leaching from those same sediments.

       It should be stated again that EPA is not seeking to set new groundwater cleanup levels
       via this ESD. The groundwater cleanup levels of 3,600 ppb and 3,500 ppb for  1.1-
       dichloroethane and acetone respectively, were set at these levels in the Record of
       Decision (ROD) (see Table I, page 54). The error that EPA is documenting  correction ot
       in this ESD, is that these cleanup levels were mistakenly not used (as they should ha\ e
       been) in calculating the cleanup levels for these contaminants for lagoon sediments in ihc
       ROD.

 b. Why are the units inconsistent (ppb versus ppm)?

       1,000 ppb is equal to 1  ppm.  The units are used for convenience, i.e. 711 ppm  versus
       711,000 ppb.

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 c. Why was Summer's Leaching model used as a determinant for the concentration of soil
contaminants?

       Summer's leaching model is the model which EPA normally approves the use of unless it
       is shown to be inappropriate for a particular application. A discussion of the inputs and
       the assumptions of the model can be found in the Appendix F of the Feasibility Study for
       PSC Resources.

 d. If the cleanup levels are changed, will we lose federal funding?

       A cleanup level change would not affect funding.

 In addition to comments regarding the ESD, we have questions about the 60%
Remedial Design, July 1996, Table 7-3, Predicted species.
 1. How come vertebrates are the only organisms listed?

       Relatively speaking, invertebrates are very adaptable and therefore are not as useful an
       indicator of the effect of an ecological change. Vertebrates in general, are viewed as
       being much more sensitive to changes.

 2. Why is the Southern bog lemming on this list (our research shows it to be out of our
geographic range)?

       Our literature search shows New England as being in the range of the Southern bog
       lemming.

 3. Are any of the organisms classified as threatened or endangered?

       The Blue-spotted salamander, Southern bog lemming and Spotted turtle are listed as
       "species of concern".

       The Eastern spade foot toad is listed as "threatened species"

       None of the species hi Table 7-3 are classified as "endangered".

B. PUBLIC MEETING

The November 19,1996 public meeting was attended by representatives of; EPA, MADEP, the
Performing Settling Defendants and O'Brien & Gere (the engineer performing the Remedial
Design). In addition, the Palmer Conservation Commission and interested members of the  public
were also present.

The majority of the discussion at this meeting was in two areas. The first area was questions

                                          5

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relating to the Remedial Investigation/Feasibility Study and the Record of Decision (the period
up to September, 1992 when the Site was characterized and the remedy chosen). The second
area was questions relating to the ESD and CAMU designation. The ESD and CAMU questions
were either similar to the written questions which are responded to above, or sought further
technical or regulatory clarification to the issues raised by the original questions.

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     I.
    FINAL EXPLANATION OF SIGNIFICANT DIFFERENCES AND
   DESIGNATION OF CORRECTIVE ACTION MANAGEMENT UNIT

INTRODUCTION

A.    Site Name and Location
            Site Name:
            Site Location:
                   PSC Resources Superfund Site
                   Hampden County, Massachusetts
            B.     Lead and Support Agencies

            Lead Agency:       United States Environmental Protection Agency (EPA)
                  Contact:


           Support Agency:


                  Contact:
                   Don McElroy, RPM
                   (617)223-5571

                   Massachusetts Department of Environmental
                   Protection (MA DEP)

                   Harish Panchal
                   (617)556-1118
           C.     Summary of Significant Differences

                  The September 15,1992 Record of Decision (ROD) called for in-situ mixing and
                  stabilization of contaminated soils and sediments, consolidation of these materials
                  with lagoon and wetland sediments on site property and capping with a
                  permeable cap. During the design process, studies showed that an ex-situ
                  stabilization process would be more effective in the short term and less expensive
                  than in-situ stabilization. These studies also showed that a low permeability cap
                  would be more effective over the long term and comparable in cost to the
                  permeable cap planned in the ROD.

                  Additionally, cleanup levels that appear in the ROD for lagoon sediment are based
                  on non-promulgated Maximum Contaminant Levels (MCLs).  Since the MCLs
                  were only proposed and not promulgated, corrections were made, based on human
                  health risk, to the cleanup values for 1,1-dichloroethane and acetone.
                                          CONCUMINCIS
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