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r <br /> ENVIROThIENTAL HEALTH'bEPARTMENT <br /> Donna IC.Haran,RE.H.S. SAN JOAQUIN COUNTY <br /> .o Unit Supervisors <br /> i a <br /> Director 304 East Weber Avenue, Third Floor Carl Borgman,R.E.H.S.. <br /> Al Olsen,RE.H.S. Stockton, California 95202-2708 Mike Huggins, S.,R.D.I. <br /> Program Manager <br /> Douglas W.Willsonson,,R.E.H.S. <br /> q�46*"' Laurie Cotulla,RE.H.S. Telephone: (209)468-3420 Margaret Lagorio,R.E.H.S. <br /> Program Manager Fax: (209)464-0138 Robert McClellon,R.E.H.S. <br /> Mark Barcellos,R.E.H.S. <br /> DAVID BUCCOLO, SUPERINTENDENT JUN 0 2 2005 <br /> CENTRAL CALIFORNIA TRACTON COMPANY <br /> 2201 W WASHINGSTTO14 STREET #12 <br /> STOCKTON CA 95203-2942 <br /> RE: Central California Traction Company SITE CODE: 1536 <br /> 1645 Cherokee Lane <br /> Stockton CA 95205 <br /> San Joaquin County Environmental Health Department(SJC/EHD)has reviewed "Remedial Action <br /> and Health &Safety Plan"(work plan)dated April 16,2005, prepared on your behalf by Bohm <br /> Environmental Solutions(BES), submitted to this agency May 20,2005, and has the following <br /> comments. <br /> The work plan proposes destruction of four onsite groundwater monitoring wells, interim <br /> remediation by overexcavation of contaminated soil,and reinstallation of the four destroyed <br /> monitoring wells. The current onsite monitoring wells have been dry for over two years. <br /> Monitoring wells MW-1 thru MW-4 will be properly destroyed under permit and inspection by <br /> overdrilling the wells to total depth with hollow stem auger and filling the boreholes with neat <br /> cement grout from the bottom up. Following completion of the proposed interim remediation and <br /> site construction activities,four replacement monitoring wells will be installed by hollow stem auger <br /> to total depth 60 feet below surface grade(bsg). The new wells will have a screen interval from 40- <br /> 60 feet bsg to intercept the current groundwater elevation. However,the work plan states that the <br /> wells will have a filter pack extending from 8 feet bsg to 55 feet bsg. SJC/EHD approves the wells <br /> to be built with a filter pack extending from no more than two feet above the top of the screen <br /> interval to total depth of the borehole,or from 38/39-60 feet bsg. Above the filter pack will be a <br /> one-foot transition seal of bentonite chips;following hydration of the bentonite chips the annular <br /> space will be filled with neat cement grout mixed with no more than 5% bentonite gel, applied <br /> through a tremmie pipe. <br /> BES has proposed to conduct an interim remediation by excavation of impacted soil based on their <br /> evaluation of both site and contaminant conditions. Boring logs indicate soil beneath the site is <br /> predominately fine grained, consisting of silty sand to silty clay. The contaminant of concern is <br /> diesel,which is less amenable to remediation by volatilization, especially in fine-grained materials. <br /> The area of impacted soil at this site has been defined by a series of geoprobe soil borings;the <br /> proposed excavation area targets soil contamination documented to exceed 2,000 milligrams per 3 <br /> kilogram(mg/kg)total petroleum hydrocarbons as diesel (TPHd). At the deepest point, near <br /> Woodward Clyde boring B-1,the proposed maximum depth of the excavation will be approximately N <br /> 40 feet bsg;the average depth will be approximately 26 feet bsg. Maximum aerial extent of the <br /> excavation is approximately 10 feet by 50 feet. Clean over-burden soil will be separated and used <br /> as backfill; impacted soil has been approved for disposal at Forward Landfill. <br /> U�� f <br />