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Californiagegional Water Quality C.trol Board <br /> Central Valley Region (� <br /> Katherine Hart, Chair <br /> 11020 Sun Center Drive,#200,Rancho Cordova,California 95670-6114 <br /> Linda S.Adams (916)464-3291 •FAX(916)464-4645 Edmund G.Brown Jr. <br /> Acting Secretary for http://www,waterboards.ca.gov/centralvalley Governor <br /> =nvironmenta/Protection RECEIVED <br /> 21 January 2011 JAN 2 5 2011 <br /> ERTERETM <br /> DESJC, M.BENSON <br /> ENVIRONMENTAL <br /> Defense Distribution Depot San Joaquin <br /> P.O. Box 960001 <br /> Stockton, CA 95296 <br /> DRAFT 2010 ESD TO THE SITE-WIDE COMPREHENSIVE ROD— DEFENSE <br /> DISTRIBUTION DEPOT SAN JOA QUIN TRACY SITE, SAN JOA QUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br /> Board) staff has reviewed the 2010 Draft 2010 Explanation of Significant Differences to the <br /> Site-Wide Comprehensive Record of Decision (Draft ESD), dated 22 November 2010. <br /> HDR prepared the Draft ESD on behalf of Defense Logistics Agency Enterprise Support San <br /> Joaquin, California (DLA) for the Defense Distribution Depot San Joaquin facility located in <br /> Tracy, California. <br /> The Draft ESD proposes changes to the 1998 DDJC-Tracy Site-Wide Comprehensive Record <br /> of Decision (Comprehensive ROD). The proposed changes include soil vapor extraction <br /> (SVE), enhanced with pneumatic fracturing as a remedy for soil cleanup beneath <br /> Warehouse 10 within Solid Waste Management Unit 20 (SWMU 20). Central Valley Water <br /> Board staff agrees with this proposal and approved the remedy change in our 12 August 2009 <br /> review of the Draft Solid Waste Management Unit 20 Feasibility Study (SWMU 20 FS). The <br /> Draft ESD also proposes changes to the Comprehensive ROD vadose zone cleanup <br /> standards for Area 1/Building 237, SWMU 1/Areas 2 and 3, and SWMU 20. Central Valley <br /> Water Board staff does not agree with these proposed changes. <br /> SWMU 20 Warehouse 10 Soil Cleanup Remedy <br /> Historically, this building contained an aboveground solvent tank and associated piping and <br /> sumps, and a paint spray booth. The remedial investigations conducted in 1993 and 1995 <br /> designated the contamination from these structures as SWMU 20. Also, the investigations <br /> included a contaminated soil area adjacent to the east side of Warehouse 10 in SWMU 20. <br /> The remedy selected for SWMU 20 in the Comprehensive ROD was excavation and off-site <br /> disposal, SVE, and natural attenuation. However, after excavations were completed in 1997 <br /> and 1999 at the north side of Warehouse 10, DLA suspected that additional contamination <br /> remained under the building, as well as the adjacent area to the east. DLA did not expect SVE <br /> to be effective for the remaining contamination. The DDJC-Tracy 2004.Explanation of <br /> Significant Differences to the Site-wide Comprehensive Record of Decision deleted SVE from <br /> the remedy for SWMU 20 and added institutional controls (ICs) for the remaining <br /> contamination. However, the ESD indicated that additional actions or continued ICs would be <br /> evaluated if Warehouse 10 were to be scheduled for demolition in the future. <br /> California Environmental Protection Agency <br /> �aRecycled Paper <br />