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San Joaquin Cour ty DIRECTOR <br /> Environmental Health Department DonnaHeran, REHS <br /> Y 3; . F' ASSISTANT DIRECTOR <br /> r 600 East Main Street Laurie Cotulla, REHS <br /> Stockton, California 95202 <br /> PROGRAM COORDINATORS <br /> • Mike Huggins,RENS,RDI <br /> ' Margaret Lagorio, REHS <br /> Website: www.sjgov.org1 hd Robert McClellon,REHS <br /> C�FORa <br /> Phone: (209) 468-3420 Jeff Carruesco, REHS, RDI <br /> F=ax: (209) 464-0138 Kasey Foley,REHS <br /> June 26, 2009 <br /> Mr. Denis L. Brown Mr. Ali Awnallah <br /> Shell Oil Products US 211 East Century Boulevard <br /> HSE— Environmental Services Lodi, California 95240 <br /> 20945 South Wilmington Avenue <br /> Carson, California 90810-1039 <br /> Subject: Former Shell Service Station <br /> 1313 East Charter Way <br /> Stockton, California 95205 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed Interim <br /> Remedial System Shutdown Request and Case CI sure Request dated April 9, 2009, and <br /> Groundwater Monitoring and Remediation Report — First Quarter 2009 dated April 28, <br /> 2009, submitted by Conestoga-Rovers & Associates (CRA) for the above-referenced site <br /> on your behalf. During the approximately two-an -a-half years the interim groundwater <br /> extraction system (GWE) has been in operation at t iis site, approximately 429,000 gallons <br /> of water have been extracted from the ground while removing approximately 0.08 pounds <br /> of 1,2-dichloroethane (1,2-DCA). Although the concentrations of 1,2-DCA have decreased <br /> significantly in groundwater collected from impacted monitoring wells MW-1, MW-2, MW-5, <br /> and MW-6, the mass removal rate of the 1,2-DCA, is very low compared to the cost of <br /> operating the GWE system; however, the total petroleum hydrocarbons quantified as <br /> gasoline (TPH-g) and benzene, toluene, ethyl benzene, and total xylenes (BTEX) masses <br /> removed were not estimated. The EHD concurs that the GWE system is not cost effective <br /> to operate and approves the shut down of the interim-GWE system, effective immediately. <br /> Although 1,2-DCA has been the main contaminant of concern at this site, high <br /> concentrations of TPH-g and benzene continue to be detected in groundwater collected <br /> from MW-1. Once the interim-GWE system has been shut down, it is uncertain what <br /> affect this will have on the dissolved petroleurn hydrocarbon plume. To monitor <br /> groundwater conditions following the cessation of the GWE system operation, continue to <br /> collect groundwater quarterly from MW-1 and analyze the samples for TPH-g, BTEX, and <br /> 1,2-DCA. <br /> CRA has recommended this site for closure consideration; however, the EHD cannot <br /> concur with a closure recommendation until the plume response to cessation of the <br /> interim-GWE has been evaluated. <br /> 9. <br />