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_ _ Vis._. ____ - `.�.,.<<,- • - ' - i <br /> ENVIRONMENTAL. HEALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> PpUIN " <br /> Unit Supervisors I <br /> Donna K.He ,R.E.H.S. Carl Borgman,R.E.H.S. <br /> Kran <br /> 304 East Weber Avenue, Third Floor Mike Huggins,R.E.H.S.,R.D.I. <br /> Director <br /> Al Olsen,R.E.H.S. Stockton, California 95202-2708 Douglas W.Wilson,R.E.H.S. <br /> • �.• 'P• Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> Laurie A.Cotulla,R.E.H.S. Robert McClellon,R.E.H.S. <br /> Program Manager Fax: (209) 464-01.38 Mark Barcellos,.R.E.H.S. <br /> ROBERT COCHRAN PPT 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 /> 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 /> 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 a continuous pumping programam 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 /> 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.Henderson,Jr.,RG <br /> Unit W-Site Mitigation Unit W-Site Mitigation <br /> I <br /> cc: David Evans -Secor <br /> James L.L.Barton-CVRWQCB <br />