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• /•' _ EomeND G. Bnown JP, <br /> ..........�0 <br /> MnTTHew RoNRlouez <br /> Water Boards <br /> Central Valley Regional Water Quality Control Board <br /> TO: Duncan Austin, P.E. <br /> Supervising Water Resources Control Engineer <br /> Site Cleanup Section <br /> FROM: James Brownell, R.G. <br /> Engineering Geologist <br /> Federal Cleanup Unit <br /> DATE: 20 September 2012 <br /> SUBJECT: RATIONALE FOR CLOSURE CONCURRENCE— UST SITE 13, DEFENSE <br /> LOGISTICS AGENCY, DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN, <br /> TRACY SITE <br /> The Defense Logistics Agency Enterprise Support (DLA) has submitted a document to Central <br /> Valley Water Board staff titled: Final— UST Site 13 Request for Closure. Underground Storage <br /> Tank (UST) Site 13 is located within the DLA's active supply Depot in Tracy, California. <br /> Background <br /> On 27 June 1991, DLA signed a Federal Facility Agreement under the Comprehensive <br /> Environmental Response, Compensation, and Liability Act (CERCLA) to clean up hazardous <br /> substance spills into soil and groundwater at multiple locations within their 448-acre Tracy <br /> Depot. However, UST Site 13 and sixteen other petroleum hydrocarbon release UST sites at <br /> the depot are exempt from the requirements of CERCLA. The Water Board regulates these <br /> sites under its UST cleanup program. <br /> UST 13 was a 2,000 gallon metal tank containing No. 2 diesel fuel. DLA installed the tank <br /> in 1982 and used it for supplying fuel to a steam boiler inside Warehouse 10. In 1987, DLA <br /> removed the UST and filled the excavation with pea gravel. In 2009, DLA demolished the <br /> warehouse'and paved the site with asphalt. The groundwater table beneath UST Site 13 is <br /> approximately 21 feet below ground surface and fluctuates seasonally by about 1 to 2 feet. <br /> UST Site 13 is within Solid Waste Management Unit (SWMU) 20, a CERCLA unit which is the <br /> location of a former sump. The sump was associated with and received waste from three <br /> sources: a trichloroethene (TICE) tank (part of SWMU 20) in Warehouse 10, a paint booth floor <br /> drain (part of SWMU 33) in Warehouse 10, and a petroleum products repackaging facility (part <br /> of SWMU 23) in Building 26. The attached U.S. Army Corps of Engineers (USAGE) map shows <br /> the locations of UST Site 13, SWMU 20, and SWMU 33. <br /> Characterization <br /> DLA completed several soil investigations and excavations at and in the vicinity of UST Site 13 <br /> as part of remedial and characterization activities associated with portions of SWMU 20 and <br /> SWMU 33. In addition to petroleum hydrocarbons, the SWMU site investigations detected <br /> several non-petroleum constituents including volatile organic compounds, semi-volatile organic <br /> KARL E. LONGLET SOD, P.E., CHAIN I PAMELA C. CREEDON P.E.. BCEE, E%EOUTNE OFFICER <br /> 11020 Son Center Drive 4200,Rancho Cordova,CA 95670 I www.waterbowdsca.gov/centcalvanay <br /> ZO ncnrciC.r.rcn <br />