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ENVIRONMENTAL HEALTH DEPARTMENT <br /> 'Quik <br /> SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> rr :a Donna K.Heran,R.E.H.S' Carl 8or <br /> Director 304 East Weber Avenue, Third Floor Mike Hu Borg <br /> man, R.E.H.S. <br /> Al Olsen, R.E.H.S. Stockton, California 95202-2708 Huggins, R.E.H.S., R.D.I. <br /> �,. Douglas W. Wilson, R.E.H.S. <br /> Laurie A.Cotulla,R.E.H.S.Program Manager Telephone: (209) 468-3420 Margaret Lagorio, R.E.H.S. <br /> c,FOR <br /> Fax: (209) 464-0138 Robert McClellon, R.E.H.S. <br /> Program Manager Mark Barecllos, R.E.H.S. <br /> ROBERT COCHRAN O F V <br /> �.. ,OCT 16 2003 <br /> CHEVRON PRODUCTS COMPANY <br /> P O BOX 6004 <br /> SAN RAMON CA 94583-0804 <br /> RE: Chevron Service Station 9-1452 <br /> 334 East Main Street <br /> `" Ripon,California <br /> San Joaquin County Environmental Health Department(EHD) has reviewed Aquifer Test Report <br /> 6— and Work Plan for Interim Remedial Measure, dated 26'June 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 /> 6, 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 off site 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 /> Gallonage of water extracted <br /> +- Average MTBE concentrations <br /> MTBE mass removed,and <br /> * Total MTBE mass removed to date. <br /> v <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:-H�ndarson, <br /> +— Unit IV-Site Mitigation Unif•N-Site Mitigation <br /> cc: David Evans -Secor [J <br /> �, James L.L. Barton-CVRWQCB L r ----- <br />