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1 Y <br />(� 1'� NAL HEALTH,DEPARTMENT <br /> El�VIl�{)l�I��IE <br /> ap�,UJ A ,� A�Q IN COUNTY <br /> Unit Supervisors <br /> cs Carl Borgman,R.E.H.S, <br /> z Danita K.Herrn,RE.�IaS. <br /> ; 3114 East-Weber venue,' 'hirticor <br /> Director Mike Huggins,'R.E.H,S,,R.D.I. <br /> AlOlsen;x.E.x.s. Stockton,California 9520212708 Douglas W.Wilson,R:E.H.S: <br /> • , <br /> g Program ManagerT <br /> Telephone:lOrl+r: (209)4f38- {) Margaret Lagorio,k.E.H.S: l <br /> Laurie A.Cotulla,R.EH.S. Robert McClellan,R,E.H.S. j <br /> Program Manager Fax: (209)464-0138 Mark Barcellos,R.E.H:S: <br /> JOE. TosTE: TR. <br /> MAR � 8 2003 <br /> JT .OT.OAAGE <br /> 48.0. :TOS.TE: ROAD <br /> "TRACY. CA <br /> ke:. Curtiss Ponfiac-Cadillac SITE CODE 1877 <br /> 2450:Tote' oad i <br /> Tracy CA '95376 <br /> San Joaquin County Environmental Health Department(SJCIEHD)has reviewed the <br /> " Omedial Action Work:Plan Addendum" (Addendum)dated December 31,20021110t <br /> :W $1.9.UbMiftdon your;behalf by.Advanced GeoEnvironmoht.al, lnc,:(ACE)and has the <br /> following cornme.nts. <br /> The;:Addendum was submitted to address specific requests made by SJCIEHD <br /> concerning the procedures of the proposed over excavation—and.. the estimated mass of <br /> soil contamination present and remaining at the site. <br /> the original Remedial Action Work Plan (RAWP)detailed a proposed over excavation <br /> for remediation of contaminated soils and continued groundwater monitoring for natural <br /> attenuation parameters. The Addendum adds that should groundwater be encountered <br /> during the over excavation operation, AGE will contain saturated soil in a bermed <br /> containment area made with clean overburden soils and lined with plastic sheeting lf' <br /> necessary,groundwater will be pumped from the excavation with submersible pumps <br /> and stored in a temporary poly tank pending proper characterization and disposal. . <br /> AGE expects most of impacted soil to occur between 3 feet and 8 feet below surface <br /> grade(bsg). AGE has estimated the mass of contamination in this interval to be <br /> equivalent to approximately 610 gallons total petroleum hydrocarbons as gasoline <br /> (TPHg)and 123 gallons TPH as diesel. The total estimated mass between 8 feet and <br /> 10 feet bsg is equivalent to 14 gallons TPHg. Therefore, with the depth of the <br /> excavation expected to be 8 feet bsg,approximately 14 gallons of TPHg may remain at <br /> this site following the remediation. <br /> To summarize,the RAWP is approved as fellows: <br /> 1_ Monitoring wells MW-1 B', MW-4 and MW-7 will be properly destroyed, under <br /> permit and inspection, by over drilling to total depth and backfilling with neat <br /> cement grout prior to the over-excavation. SJCIEHD recommends the neat <br /> cement grout extend to 8 feet bsg, and that bentonite be used above that <br /> depth. <br /> 2 An over-excavatio of approximately 1,000 cubic yards of contaminated soil <br /> will take place. The extent of the excavation will be based on soil sample <br /> analytical results gathered during the site investigations. Soil removed will be <br />