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ENVIRONMENTAL HEALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> A Donna K Heran,R E H S304 East Weber Avenue, Third Floor Carl Borgman,R E H S <br /> _ Direclor Mike Huggins,R E H S.R D I <br /> Al Olsen,R E H S Stockton, California 95202-2708 Douglas W Wilson, R E H S <br /> - oq a�P • Program Manager Telephone (209) 468-3420 Margaret Lagono R E H S <br /> /FOR Laurie A Cotulla,R E H S Robert McClellon, R E H S <br /> Program Manager Fax (209} 464-0138 Mark Barcellos R E H S <br /> ROBERT COCHRAN COPY 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 /> 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 wntten 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 /> Dunng 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 Hnciori,Jr,,RG <br /> Unit IV-Site Mitigation U i IV-Site Mitigation <br /> cc David Evans-Secor <br /> James L L Barton-CVRWQCB t✓ r._ __ <br />