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r California Figional Water Quality Co�rol Board <br /> Central Valley Region a a <br /> Katherine Hart, Chair <br /> Linda S.Adams 11020 Sun Center Drive#200,Rancho Cordova,California 95670-6114 Arnold <br /> Secretary for Phone(916)464-3291 •FAX(916)464-4645 Schwarzenegger <br /> Environmental http://www.waterboards.ca.gov/centralvalley Governor <br /> Protection <br /> GRE E7F[0 <br /> 4 October 2010 <br /> OCT n 6 2010 <br /> ENVIROMMEN T HEALTH <br /> DESJC, M.BENSON PE i�IT/StPViCA <br /> Defense Distribution Depot San Joaquin <br /> ES <br /> P.O. Box 960001 <br /> Stockton, CA 95296 <br /> DRAFT AREA 11BUILDING 237 REMEDIAL INVESTIGATION WORKPLAN <br /> DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN— TRACY SITE <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br /> Board) staff has reviewed the draft Defense Distribution Depot San Joaquin — Tracy Site, <br /> Area 1 /Building 237 Remedial Investigation Work Plan, (Work Plan) dated August 2010, and <br /> received 1 September 2010. HDR I e 2 prepared the Work Plan, on behalf of Defense <br /> Logistics Agency Enterprise Support San Joaquin, California (DLA) for its Tracy depot. <br /> Background <br /> In 2009, DLA installed vapor monitoring and vapor extraction wells to enhance soil vapor <br /> extraction of volatile organic compounds at Area 1 / Building 237 (site) on the Tracy depot. <br /> Waste characterization analyses of soil cuttings from these wells detected pesticides at <br /> concentrations that exceeded hazardous disposal criteria. In October 2009, DLA hand <br /> augured soil borings at six site locations and collected soil samples for chemical analyses from <br /> depths of 1, 3 and 5 feet below ground surface (bgs). At one of the locations, several <br /> pesticides exceeded screening levels for soil, with concentrations generally increasing with <br /> depth. At two other locations, concentrations above screening levels were detected in the <br /> 1-foot bgs sample. At both of these locations the concentrations decreased to below screening <br /> levels in the 3 and 5 foot bgs samples. The following pesticides were detected at <br /> concentrations above screening levels: heptachlor, dieldrin, dichlorodiphenyldichloroethylene <br /> (DDE), dichlorodiphenyldichloroethane (DDD), dichlorodiphenyltrichloroethane (DDT), <br /> a-chlordane, and g-chlordane. <br /> In May and July 2010, DLA collected groundwater samples from four shallow monitoring wells <br /> at the site and analyzed them for pesticides. Laboratory chemical analysis detected the <br /> following pesticides in monitoring well LM192AU: DDD, DDE, DDT, and dieldrin; pesticides <br /> were not detected in the other three wells. LM192AU is the only well located within the area of <br /> soil known to be contaminated with pesticides at the site; the others are located approximately <br /> 80 to 120 feet side- or down-gradient and beyond the contaminated areas. The concentrations <br /> in LM192AU have been less than the Aquifer Cleanup Levels established in the April 1998 final <br /> Site-Wide Comprehensive Record of Decision for the Tracy depot. <br /> California Environmental Protection Agency <br /> CFecycled Paper <br />