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ENVIRONMENTAL HEALTH DEPARTMENT <br /> SAN JOAQUIN- COUNTV <br /> Unit Su erdisors <br /> Donna K.Heran,R.E.H.S. <br /> N ' ` 304 East Weber Avenue, Third Floor Cart ©orgman, R.E.H.S. <br /> Direuar Mike Huggins, R.E.H.S.,R.D.I. <br /> AI Olsen,R.EALS, Stockton, California 95202-2708 <br /> Douglas W. Wilson, R.E.H.S. <br /> Program Manager <br /> Laurie A.Cotulla.R.E.H.S. Telephone: (209) 468-3470 Margaret Lagorio, R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Robert McCtellon. R.E.H.S, <br /> Mark Barccllos, R.E.H.S. <br /> ROBERT COCHRAN O P V <br /> OCT 1 6 2003 <br /> CHEVRON PRODUCTS COMPANY <br /> P O BOX 6004 <br /> SAN RAMON CA 94583-0804 <br /> RE: Chevron Service Station 9-1.452 <br /> 334 East Maim Street <br /> Ripon,California <br /> San Joaquin County Environmental Health Department(EHD) has reviewed Aquifer Test Report <br /> and Work Plan for Interim Remedial Measure, dated 26 dune 2003, prepared by Secor <br /> International Incorporated(Secor)on your behalf. The above referenced work plan for an interim <br /> remediation measure to reduce dissolved methyl tertiary-butyl ether(MTBE)by extracting <br /> approximately 8,000 gallons of groundwater from monitoring well (MW-8)by a single vacuum <br /> truck each month for six months,is approved as written. However, it has not been shown that <br /> short-term,periodic groundwater extraction will provide hydraulic control on the plume of <br /> impacted groundwater. As the plume appears to be migrating offsite toward the southwest, <br /> where the plume is not readily accessible, it would seem that hydrological control of the plume <br /> would be a primary objective;therefore, EHD believes that a continuous pumping program would <br /> better control the MTBE plume. <br /> During this investigation,please provide the following information,monthly, in a brief report: <br /> 0 Gallonage of water extracted <br /> 0 Average MTBE concentrations <br /> 0 MTBE mass removed,and <br /> • Total MTBE mass removed to date. <br /> Quarterly groundwater monitoring reports should provide an analysis and discussion of the <br /> hydraulic control exerted by the monthly extraction events on plume migration. Please include a <br /> brief narrative that addresses this issue. <br /> If you have any questions regarding this letter,please contact Vicki McCartney,REHS, at <br /> (209)468-3456. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> Vicki McCartney, REHS Nuel C..-Hnc K§9;4,Jr.,,RG <br /> Unit W-Site Mitigation Uni(•IV-Site Mitigation <br /> cc: David Evans -Secor U <br /> James L.L. Barton-CVRWQCB i✓ t__ -_ <br />