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! I <br /> 1 Department of Toxic Substances Control <br /> Maureen F. Gorsen, Director <br /> Linda S.Adams 8800 Cal Center Drive Arnold Schwarzenegger <br /> Agency secretary Sacramento, California 95826-3200 Governor <br /> Cal/EPA HECo �� ED <br /> HE IllILOCT 2 7 2008 <br /> October 24, 2008 ENVIRONMENT i'iEAL1H <br /> PERMIT/SERVICES <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 REMEDY ENHANCEMENT DECISIONS AT SVE SITES <br /> AREA 1/BUILDING 237, SVVMU VAREA 2, AND AREA 3 REPORT FOR DEFENSE <br /> DISTRIBUTION DEPOT SAN JOAQUIN COUNTY (DDJC), TRACY SITE, TRACY, <br /> CALIFORNIA <br /> Dear Mr. Benson: <br /> The Department of Toxic Substances Control (DTSC) received the above-mentioned <br /> report on September 12, 2008, submitted on behalf of Defense Enterprise Support <br /> San Joaquin California (DESJC). The report summarizes the results from a Cone <br /> Penetrometer Test (CPT) investigation performed in March 2008 to collect soil and soil <br /> vapor data from three current soil vapor extraction (SVE) Areas to estimate the volatile <br /> organic compounds (VOCs) concentrations and residual mass remaining in the vadose <br /> zone. The report also evaluates the sites' analytical data in conjunction with the SVE <br /> termination or optimization process to determine which sites still require remedial <br /> actions and those sites proposed for No Further Action. <br /> The March 2008 CPT fieldwork efforts for the three areas sampled a total of 22 <br /> locations, collected a total of 47 soil gas samples, and an additional 22 groundwater <br /> samples were collected and analyzed. A total of 10 soil samples were collected and <br /> analyzed for VOCs, metals, and physical parameters. <br /> DTSC has reviewed the report and has the following comments: <br /> Comments: <br /> 1. Figure 4-6, Area 1-1; The VLEACH modeling analysis shows that <br /> Tetrachloroethene (PCE) concentrations in Area 1-1 soil leachate will exceed the <br /> federal Maximum Contaminant Level for a period of 20 years before <br />