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ARCO Service Station No. 2186 Page 2 <br /> 3212 North California Street August 22,2008 <br /> Stockton, California 94570 <br /> Therefore, the EHD concurs with the recommendation presented by SECOR to destroy <br /> MW-I and MW-3 and replace MW-1 with two monitoring wells screened appropriately. <br /> Based on non-detect analytical results for groundwater samples collected from up- <br /> gradient monitoring well MW-3, the EHD believes MW-3 should be replaced with one <br /> monitoring well screened across the first groundwater bearing zone. Please submit a <br /> work plan for the destruction ofMW-I and MW-3, and a work plan for the installation of <br /> three new monitoring wells to the EHD by October 17, 2008, and complete the fieldwork <br /> by November 7, 2008. <br /> Results from the first quarter 2008 sampling event indicate that groundwater samples <br /> collected frons monitoring well MW-1 continue to be impacted with high concentrations <br /> of GRO, benzene, and MTBE. To address the impacted groundwater found in MW-1, the <br /> EHD recommends that you consider implementing groundwater batch extraction, using <br /> replacement wells for MW-I to remove additional petroleum hydrocarbon mass from the <br /> groundwater. Please respond to the above recommendation by October 17, 2008, and if <br /> you concur, please submit a work plan to the EHD by November 21, 2008, for the <br /> implementation of batch extraction. <br /> By letter dated June 7, 2007, the EHD approved terminating the operation of the soil <br /> vapor extraction (SVE) system for three months after which SECOR would perform a <br /> rebound test. In Quarterly Groun(lwater Monitoring and Remediation Progress Report— <br /> First Quarter 2008 dated May 20, 2008, it is stated that the SVE system would be shut <br /> down on January 29, 2008, for a rebound test. Based on data submitted in the first <br /> quarter 2008 report, the EHD believes operation of the SVE system should be <br /> discontinued due to asymptotic recovery levels and is awaiting results from the rebound <br /> test to determine whether operation of the SVE system may be permanently terminated. <br /> If you have any questions regarding this letter, please contact Vicki McCartney, Senior <br /> Registered Environmental Health Specialist, at (209) 468-9852, or by email at <br /> vmccartney@sjcehd.com. <br /> Sincerely, <br /> 71 <br /> Victoria L. McCartney, Senior HS Nuel C. Henderson, Jr., PG <br /> Senior Registered Environmental Healthpecialist Engineering Geologist <br /> c: Mr. Rusty Benkosky, PE, SECOR International Incorporated, 3017 Kilgore Road, <br /> Suite 100, Rancho Cordova, California 95670 <br /> Mr. James L.L. Barton, PG, California Regional Water Quality Control Board Central <br /> Valley Region, 11020 Sun Center- Drive, Suite 200, Rancho Cordova, California <br /> 95670 <br />