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ENVIRONMENTAL HEALTH DEPARTMENT <br /> *° SAN JOAQUIN COUNTY <br /> 10 L eaG Unit Supervisors <br /> Donna K Heran,R E H S 304 East Weber Avenue, Third Floor Carl Borgman,R E H S <br /> �+ k i Director Mike Huggins R E H S , R D I <br /> Al Olsen,R E H S Stockton, Caltfomta 95202-2708 Douglas W Wilson, R E H S <br /> • p o-• Program Manager Telephone {209} 458-3420 Margaret Lagono R E H S <br /> °t'a oRr'` Laurie A Cotulla R E H S 09 464-01 38 Robert McClellon,R E H S <br /> Program Manager Fax (2 ) Mark Barcellos,R L H S <br /> ROBERT COCHRAN c (OF)v PCT 1 6 ZOOS <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 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 /> 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 /> Nuel C Hrenc�rson,Jr.,1ZG_ <br /> Vicki McCartney,REHS Unita N-Site Mitigation <br /> Unit IV-Site Mitigation <br /> cc David Evans -Secor <br /> James L L Barton-CVRWQCB L r <br />