PB99-963107
                              EPA541-R99-033
                              1999
EPA Superfund
      Explanation of Significant Difference
      for the Record of Decision:
      Idaho Pole Co.
      Bozeman, MT
      11/3/1998

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                  UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                                      REGION 8, MONTANA OFFICE
                              FEDERAL BUILDING, 301 S. PARK, DRAWER 10096
                                     HELENA, MONTANA 59626-0096
  Ref: 8MO

  November 23, 1998

  MEMORANDTTM

  SUBJECT:   Explanation of Significant Differences for the Idaho Pole Company Superfund
               oite
  FROM:       Jim Harris, 81       .
               Remedial Projfec/Manager

  TO:          Max H. Dodson, ARA
               Office of Ecosystems Protection and Remediation


        Attached is an Explanation of Significant Differences (ESD) for the Idaho Pole Company
 Superfund Site located in Bozeman, Montana for your signature. The purpose of the ESD is to
 modify the scope of the site cleanup to include areas that were excluded in the 1992 Record of
 Decision (ROD).

        The 1992 ROD  excluded excavation of contaminated soils associated with structures on
 the site so that the company could continue operations. Idaho Pole Company announced the
 closing of the facility last fall and EPA believes that the remaining contaminated soils identified
 during the Remedial Investigation must be remediated. Access to the contaminated soils will
 require the demolition of several structures on the site including buildings, tanks, vaults, slabs
 and associated utilities.
Concurrence List: B. Fox, 8MO
                 J. Wardell, 8M
                 S. Bohan, 8E
                 C. Rushin,
Attachments:
                                                                      Printed on Recycled Paper

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               EXPLANATION OF SIGNIFICANT DIFFERENCES

                           Idaho Pole Company Superfund Site
                                   Bozeman, Montana

                      United States Environmental Protection Agency
                                    November  1998
  I. INTRODUCTION
  «        l Ex*!l™alion of Significant Differences (ESD) for the Idaho Pole Company
  Superfund Site (Site) is being issued by the U.S. Environmental Protection Agency (EPA) in
  consultation with the Montana Department of Environmental Quality (MDEQ) to explain
  modifications to the remedy at the Site contained in the Record of Decision (ROD) issued on
  September 28 1992. Specifically, the purpose of this ESD is to document changes to the ROD
      A pen     f 6 n1ecessitated ^ ** closure °f the Idaho Pole Company plant.  This is the
  second ESD issued at the Site by EPA. The first ESD was issued on May 15, 1996.

        In accordance with Sections 1 17(c) and 121 of the Comprehensive Environmental
 Response, Compensation, and Liability Act of 1980 (Superfund), as amended, 42 U.S.C. Section
 wui, st sssu (CERCLA), and the regulations at 40 C.F.R. Section 300.435(c)(2)(I), the National
 Oil and Hazardous Substances Pollution Contingency Plan (NCP), this ESD has been prepared
 for the following reasons:

              to provide the public with an explanation of the nature of the changes to the
              remedy;

              to summarize the circumstances that led to the changes to the remedy; and

             to affirm that the revised remedy complies with all statutory requirements.

      This document presents only a summary of the changes to the selected remedy and a
synopsis of information on the Site. The Administrative Record, which contains this ESD and its
supporting documentation, is available for public review at the locations indicated at the end of
this report.

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  H. SITE HISTORY AND BACKGROUND

        The Idaho Pole Company (IPC) wood treating facility began operation in 1945 using
  creosote to preserve wood. In 1952, the company switched to pentachlorophenol in carrier oil
  (similar to fuel oil) for the wood treating solution. IPC's wood treating operations ceased in
  1997.

        Throughout the course of wood treating operations, there were various releases of oily
  wood treating fluid from the plant. IPC conducted certain investigation and cleanup activities
  after contamination was identified, and in 1986, the facility was added to the National Priorities
  List of Superfund sites.

       In 1989, MDEQ assumed the lead agency role through a cooperative agreement with EPA
 and began the remedial investigation and feasibility study (RI/FS) following the EPA approved
 Work Plan and EPA guidance. The RI defined the nature and extent of contamination and
 provided data to complete the baseline health and ecological risk assessments.  The FS included
 the development,  screening and evaluation of potential site remedies. The ROD was issued by
 EPA on September 28, 1992.

                                                                *  . .
 III.  SUMMARY OF THE 1992 RECORD OF DECISION

       The contaminants of concern at the Site are pentachlorophenol (PCP), polynuclear
 aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins and polychlorinated
 dibenzofurans. The Record of Decision established cleanup levels for those contaminants of
 concern at the Site. The major components of the selected remedy, as modified by the May 1996
 ESD include:

Soils Component

      o      Excavation and surface land biological treatment of contaminated soils from the
             pasture area, the area between Cedar Street and U.S. Interstate Highway 90 (1-90),
             the plant area and the former roundhouse area;

      o      Ambient temperature water flushing of soils underlying the pole plant facility and
             1-90 in order to recover hazardous substances;

      o      Construction of a land treatment unit (LTU) to treat excavated soils. The total soil
            depth on the LTU is less than two feet. The LTU will be operated to treat the
            surface soils to approximately one foot in depth and the soils will be removed
            when the cleanup levels for PCP and PAHs are met.

      o     Use  of the treated soils for fill material on the plant site. If the soil contains other

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                 contaminants that exceed the ROD levels, the soil will be isolated from ground
                 water, will be covered at the surface to prevent direct contact and institutional
                 controls on future land use will be required.  A detailed closure plan for the LTU
                 will be developed when soil monitoring results indicate that the cleanup levels for
                 PCP and PAHs have been achieved.  The closure plan will identify the areas to be
                 backfilled with the treated soil and will specify the distance above the ground
                water that the treated soil must be placed and the depth of cover required. The
                plan will also identify the specific institutional controls to be implemented on the
                pole plant facility.

  Ground Water Component

         o      Ground water cleanup using extraction and a granulated activated carbon (GAC)
                system and return of water to the ground water aquifer to enhance in situ
                biological degradation and to control potential migration of contaminants;

         o      Treatment of contaminated residential wells exceeding maximum contaminant
                levels (MCLs) or risk based concentrations of the contaminants of concern at the
               distribution point in addition to institutional controls preventing new access to
               contaminated ground water; and

         o     Continued residential and ground water monitoring to determine movement of
               contaminants and compliance with remedial action requirements.


 IV. DESCRIPTION OF SIGNIFICANT DIFFERENCES TO THE REMEDY

        The significant difference between the remedy described in the 1992 ROD and in this
 BSD is that the plant structures including concrete pads, piping, vaults, etc., preventing access to
 contaminated soil will be demolished and disposed of in accordance with State of Montana and
 EPA requirements and that contaminated soils underlying these areas will be excavated and
 treated like the accessible plant soils have been to date.

       Idaho Pole Company discontinued active wood treating operations at the Site in 1997
 and has indicated to EPA that it has no intention of restarting operations at this location Since
 1997, Idaho Pole Company has transferred some of its equipment off-site and is continuing to
 decommission the pole plant.

       EPA's selection of the remedy for the contaminated soils at the Site  was influenced in
 large part, by the fact that an active wood treating operation existed on the Site above
contaminated soils. In the Feasibility  Study, EPA and the State of Montana evaluated cleanup
options including the destruction of the buildings and excavation of underlying soils  The fact
that soils immediately surrounding and perhaps underneath many of the existing structures are

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   contaminated is supported by Site operational history which includes boil overs of wood treating
   fluids m 1981 and 1987. The known spills were associated with the retort building and the butt
   vat  Soil sampling during the RI adjacent to and underneath the plant structures confirmed that
   soil contamination is present.

          When selecting the soils remedy, EPA determined that the direct and indirect costs of
   requiring the demolition of the active wood treating operation and excavation of underlying soils
   made this option impracticable. EPA understood from IPC that the closing of the facility would
   severely compromise IPC's financial viability, and could potentially result in IPC's bankruptcy
   EPA sought a comparable remedy which would allow IPC to continue in business and continue
   earning money which could be dedicated to the cleanup of the facility.  At the time of the ROD
   IPC had no plans to close the facility, thus the plant structures were viewed as a de facto cap over
   the underlying contaminated soils which, for the foreseeable future, mitigated risks of exposure.
   The sekcted remedy called for excavation and treatment of contaminated soils that were
  accessible and identified soil flushing/in situ biological treatment as the appropriate remedy to
  address soils beneath the plant and the nearby interstate highway (1-90). The ROD contemplated
  that institutional controls would be used in conjunction with this remedy to ensure its
  protectiveness since soil flushing/in situ biological treatment as a stand alone alternative would
  possibly not achieve the 1 x 10 ^ risk level. Soil flushing/in situ biological treatment was
  estimated to have a range of removal of contamination of from 40% to 80% - in other words the
  selected remedy under the pole plant would not completely clean up all of the soil contamination.

        With the closing of the pole plant, the relative certainty about the continued
  inaccessibility of soils underlying the plant has diminished markedly. It is unlikely that another
  wood treating operation would move onto the property and continue operations. A more likely
  scenano isi that the property will be sold and ultimately used for another purpose. Some, if not
 all  of the buildings will be demolished under this scenario, and the underlying contamination
 wi 1 need to be addressed. By leaving contamination under the closed pole plant until some point
 in the future when new construction is planned, the cleanup is prolonged, issues involving the
 control of access to the property under new ownership arise, and the prospect arises that a new
 LTU would have to be constructed at significant cost. In light of these considerations, EPA has
 reevaluated the soils remedy at the Site and determined that it is more appropriate to demolish
 and dismantle the pole plant structures now and excavate and treat the underlying contaminated
 soils Additional soil sampling, excavation and treatment would proceed in accordance with the
 procedures established in the selected remedy for accessible soils (Soil Alternative 4) as
 amended by the May 15,1996 ESD.

        There is no change in the remedy selected for soils underlying 1-90; soil flushing will
continue in this area.

       Community members and City of Bozeman representatives requested, prior to the
issuance of the ROD, that the cleanup be expedited.  This change to the ROD will expedite the
completion of the remedy.  Buildings can be demolished and the underlying soils accessed

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   SSV!"1* 6XCTtd " neC6SSary in relativdy Short order> M ^P^ to ^e continuous soil
   flushmg process which is estimated to achieve the necessary results in a 5 to 10 year time frame

          This change will also reduce the reliance that will be placed on institutional controls such
   as and use restnctions  At present, there is negligible risk toon-site workers associated ^th
   soils underlying the pole plant. However, any future disturbance of the contaminated soilT
   ±cec±!l   tTH" ^rf^ t0 recontaminate *« -eas of the site^d to cr ±an
   unacceptable nsk to human health and the environment.  This potential threat would remain
   whilethe contamination remains beneath the structures.  To  provide more certainty, E*TL
   modifying the remedy to require the demolition of these vacant buildings and theTemovd of
   underlying soils that exceed the action levels set forth in the  ROD.
                                                                 OF
         natio?±h°Ve' ^ ^ ^^^ She devel°P^ts that serve as the basis for this
                                          EPA °n "* — MDE^ — have been
  Comn^r6^ ^f d t0 thiS ESD "* Part °f ^ Admi™trative ^cord for the Idaho Pole
  Company Site  The Administrative Record will also contain any written public comments that

                ^^^
 U.S. EPA Montana Office               Bozeman Public Library
 Federal Building, Room 192             220 East Lamme Street
 30  South Park, Box 10096              Bozeman, Montana 59717
 Helena, Montana 59626-0096            (4061 58? 240n
             °                        (Library hours vary.)
             a.m.to 5:00 p.m.
 VI. AFFIRMATION OF STATUTORY REQUIREMENTS

       Considering the new situation with respect to the closure of the pole plant and the
 changes that have been made to the selected remedy, EPA, in consultation with MDEQ believes
 Aat Ae remedy remains protective of human health and the environment, complies wS Federal
Tr tvot reqUirementS Aat m both *PPIicable or relevant and appropriate to this remedial act?on
or involves appropriate waivers of these requirements, and is cost-effective. In addition the
reused remedy utilizes permanent solutions and alternative treatment technologies to the
maximu
maximum extent practicable for the Site.

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  VII. APPROVAL
     j	5^	-y-T.
 Mafk A. Simonich, Director                            Date

 Montana Department of Environmental Quality
< - 	    i  • • ••!• -—MI»-I»I •-» 1.,^, *., n,. n  ^ i n f irjaa_jr                y j ...™.. 1 ^
Max H. godson, ARA                ^                 Date

Office of Ecosystems Protection and Remediation

U.S. Environmental Protection Agency

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