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Dvq <br /> Department of Toxic Substances Control ,, <br /> a ( <br /> Terry Tamminen 8800 Cal Center Drive Arnold Schwarzenegger <br /> Agency Secretary Sacramento, California 95826-3200 Governor <br /> Cal/EPA <br /> September 13, 2004 <br /> SEP 1 6 21110a <br /> SAN JQAQf-tl,,,l 0;A)A:r,' <br /> Mr. Marshall Cloud EMARONhiENiAL0L2T, <br /> Remedial Project Manager <br /> Defense Distribution Depot—Tracy Site <br /> Post Office Box 960001 <br /> Tracy, California 93727-0525 <br /> CONCURRENCE WITH THE REVISED DRAFT FINAL REMEDIAL ACTION REPORT <br /> (RAR) FOR SOLID WASTE MANAGEMENT UNIT (SWMU) 8 LARGE EXCAVATION <br /> SITE AT DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN (DDJC) — TRACY SITE, <br /> TRACY, CALIFORNIA <br /> Dear Mr. Cloud: <br /> The Department of Toxic Substances Control (DTSC), received the Revised Draft Final <br /> SWMU 8 RAR, dated July 2004, on July 26, 2004. The RAR describes the remedy <br /> implementation including the excavation of over 17,000 cubic yards of pesticide <br /> contaminated soil with offsite disposal to Class 1 and Class 2 landfills, the results of <br /> confirmation samples collected, and the placement of clean fill between September and <br /> December 2002 at SWMU 8, the former burn pit at DDJC-Tracy. The confirmation <br /> samples collected from the base and sidewalls of the excavation show that the <br /> maximum detections of 47pg/kg and 4 pg/kg for dichlorodiphenyltrichloroethane (DDT) <br /> and dieldrin, respectively, were below the cleanup standards for SWMU 8. The cleanup <br /> standards, established in the 1998 Site-Wide Comprehensive Record of Decision <br /> (ROD) and revised in the 2004 Final Explanation of Significant Differences to the <br /> Sitewide Comprehensive Record of Decision (ESD), are 103 pg/kg for DDT and 5 pg/kg <br /> for dieldrin. <br /> Background <br /> The original cleanup standards specified in the 1998 Site-Wide Comprehensive ROD for <br /> DDT and dieldrin of 7 pg/kg and 2 pg/kg, respectively, were based on potential for <br /> impacts to groundwater using limited data. These cleanup standards were reevaluated <br /> after the excavation failed to meet the cleanup standards. The 2004 ESD revised the <br /> cleanup standards based on further Dionized Water Waste Extraction Test (DI WET) <br /> results and vadose zone modeling using SESOIL and VLEACH simulations. For <br /> 9 Printed on Recycled Paper <br />