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Department of Toxic Substances Control <br /> a Maziar Movassaghi <br /> Linda S.Adams Acting Director Arnold Schwarzenegger <br /> Secretary for 8800 Cal Center Drive Governor <br /> Environmental Protection Sacramento, California 95826-3200 <br /> January 13, 2010 <br /> Mr. Maurice Benson <br /> Defense Logistics Agency <br /> Defense Distribution Depot San Joaquin, Sharpe Site <br /> Post Office Box 960001 <br /> Stockton, California 95296-0250 <br /> COMMENTS ON THE DRAFT REMEDIAL DESIGN/REMEDIAL ACTION WORK PLAN <br /> (RD/RAW) FOR SOIL VAPOR EXTRACTION (SVE) AT SITE P-5A FOR DEFENSE <br /> DISTRIBUTION DEPOT SAN JOAQUIN CALIFORNIA (DDJC), SHARPE SITE, <br /> LATHROP, CALIFORNIA <br /> Dear Mr. Benson: <br /> The Department of Toxic Substances Control (DTSC) received the above-mentioned <br /> RD/RAW on October 31, 2009, submitted by URS Corporation on behalf of the <br /> Defense Environmental Support San Joaquin California (DESJC). <br /> The P-5A RD/RAW provides the design and subsequent field work activities to support <br /> the installation of a SVE system designed to remediate volatile organic compounds <br /> (VOCs) in the vadose zone soils in the Central Area of DDJC-Sharpe. Specifically, <br /> tricholoroethene (TCE) and its breakdown products remain in Site P-5A unsaturated <br /> zone soils at concentrations that act as a persistent source of VOC groundwater <br /> contamination. DESJC implemented EHC with hydraulic fracturing on August 19, 2008 <br /> to remediate the existing contamination in the saturated zone soils and localized <br /> groundwater. EHC with hydraulic fracturing was somewhat successful in reducing <br /> contaminant concentrations in the source area but did not achieve the aquifer cleanup <br /> level of 5 pg/L for TCE. The reduction in TCE mass in the saturated soil due to the EHC <br /> pilot study will allow DESJC to concentrate remedial efforts in removing the remaining <br /> TCE mass in unsaturated soil to eliminate one of the persistent sources of groundwater <br /> contamination at DDJC-Sharpe. <br /> DESJC plans to install, startup and operate five soil vapor extraction wells (VEWs) and <br /> three soil vapor monitoring (SVM) wells in the vadose zone within the source area <br /> ® Printed on Recycled Paper <br />