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SG1 THE <br /> environmental 1SOURCE GROUP, INC. <br /> October 24, 2012 <br /> Mr. James L. L. Barton, P.G. <br /> Region 5 Regional Water Quality Control Board <br /> 11020 Sun Center Drive, Suite 200 <br /> Rancho Cordova, CA 95670 <br /> Well Head Treatment Evaluation, DGS EAR Account Program, Countryside Market, <br /> Stockton, California, EAR Site No. R10-129 <br /> Dear Mr. Barton: <br /> The Source Group Inc. (SGI) has prepared this Well Head Treatment Activities Letter (Letter) for <br /> the Department of General Services (DGS).Emergency, Abandoned, & Recalcitrant (EAR) <br /> Program Account project site located at 10848 Copperopolis Road, Stockton, California, <br /> referred to as EAR Site No. R10-129 (Site). Based on analytical detections the California Water <br /> Quality Control Board (RWQCB) directed SGI to prepare this well head treatment evaluation. <br /> This Letter details activities to install a well head treatment system at a domestic well located <br /> hydraulically down gradient of the Site. <br /> Domestic Well Sampling <br /> A total of five groundwater samples have been collected from the domestic well (10967 <br /> Copperopolis Road) between March and September 2012. 1,2-dichloroethane (1,2-DCA) was <br /> reported at a maximum concentration of 25 micrograms per liter (ug/L) in the pre-treatment <br /> sample and at a maximum concentration of 7.8 ug/L in the post-treatment sample. California <br /> Environmental Protection Agency (CEPA) Maximum Contaminant Level (MCL) for 1,2-DCA is <br /> 0.5 ug/L. The existing treatment system consists of a resign based water softening system that <br /> is not effectively reducing 1,2-DCA concentrations below the MCL. <br /> Well Head Treatment Activities <br /> United States Environmental Protection Agency (USEPA) calculates the average water <br /> consumption for a family of four is approximately 400 gallons per day. During the preparation of <br /> this well head treatment evaluation, SGI conservatively assumed 1,000 gallons per day (safety <br /> factor of 2.5) will be used at the Site. Based on an assumed daily flow rate of 1,000 gallons and <br /> a maximum influent concentration of 25 ug/L, it is estimated 0.06 lbs of carbon will be used per <br /> day. SGI will install two 2001b carbon vessels design to operate in series. A sampling manifold <br /> will be constructed to allow sample collection at influent, mid-, and effluent sampling ports. Well <br /> 944 McCourtney Road,Suite H Telephone:(530)272-4200 <br /> Grass Valley,California 95949 Facsimile:(530)272-4211 <br />