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NOV 2 1 2008 <br /> `- Department of Toxic SubW" ift01 <br /> vMaureen F. Gorsen, Director <br /> Linda S.Adams 8800 Cal Center Drive <br /> Agency Secretary Sacramento, California 95826-3200 Arnold Schwarzenegger <br /> Cal/EPA Governor <br /> November 19, 2008 <br /> Mr. Maurice Benson <br /> Defense Logistics Agency <br /> Defense Distribution Depot San Joaquin, Tracy Site <br /> Post Office Box 960001 <br /> Stockton, California 95296-0250 <br /> COMMENTS ON THE OPERABLE UNIT 1 REBOUND TEST AND REMEDIAL ACTION <br /> OPTIMIZATION WORK PLAN FOR DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN <br /> COUNTY (DDJC), TRACY SITE, TRACY, CALIFORNIA <br /> Dear Mr. Benson: <br /> The Department of Toxic Substances Control (DTSC) received the above-mentioned <br /> report on October 14, 2008, submitted on behalf of Defense Enterprise Support <br /> San Joaquin California (DESJC). The work plan describes the proposed field activities <br /> to conduct a rebound test with the groundwater treatment and extraction system known <br /> as Operable Unit 1(OU1) at DDJC-Tracy. DESJC wants to perform the rebound test to <br /> evaluate to what extent groundwater contaminant concentrations change throughout the <br /> existing plume areas in the absence of active pumping. <br /> The proposed rebound test would commence on December 1, 2008, and would result in <br /> the shutdown of all 20 currently operating extraction wells at DDJC-Tracy site for a <br /> period of eighteen months. The results of the rebound test will be evaluated and used <br /> to determine whether to continue with optimization of the pump and treat remedy or <br /> perform an extended shut down test with an evaluation of monitored natural attenuation <br /> as a remedial option. <br /> DTSC has reviewed the work plan and considers the proposal to shutdown the OU1 <br /> groundwater extraction and treatment system premature considering the ongoing <br /> remedial efforts and current data gaps with plume delineation. DESJC should focused <br /> fieldwork efforts to vertically and horizontally delineate the NE Banta Road <br /> Tricholorethene (TCE) plume, remediate the remaining Volatile Organic Compounds <br /> (VOC) sources at the Soil Vapor Extraction (SVE) Area 1/Area 3, Warehouse 10, and <br /> await the results from the Focused Feasibility Study for dieldrin mass removal in the <br /> saturated zone prior to proposal of an OU1 Rebound Test. <br />