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VAL aECaV <br /> APR 1 7 2009 —� <br /> %r? <br /> T H ALTH <br /> aer ent of Toxic Substances Control <br /> Maziar Movassaghi <br /> Linda S.Adams Acting Director <br /> Arnold Sc egger <br /> 8800 Cal Center Drive <br /> Agency Secretary Governor <br /> Cal/EPA Sacramento, California 95826-3200 <br /> April 16, 2009 <br /> Mr. Maurice Benson <br /> Defense Logistics Agency <br /> Defense Distribution Depot San Joaquin, Tracy Site <br /> Post Office Box 9600Q1 <br /> Stockton, California 95296-0250 <br /> COMMENTS ON THE GROUNDWATER MONITORING WELL INSTALLATION WORK <br /> PLAN, LM193AU, WAREHOUSE 10 FOR DEFENSE DISTRIBUTION DEPOT <br /> SAN JOAQUIN COUNTY (DDJC), TRACY SITE, TRACY, CALIFORNIA <br /> Dear Mr. Benson: <br /> The Department of Toxic Substances Control (DTSC) received the above-mentioned <br /> report on March 5, 2009, submitted on behalf of Defense Enterprise Support San <br /> Joaquin California (DESJC). The work plan summarizes the proposed installation of <br /> one-shallow groundwater well within the Warehouse 10 footprint to determine if <br /> Trichloroethene (TCE) persists at concentrations greater than the Aquifer Cleanup Level <br /> (ACL) in groundwater. <br /> Warehouse 10 is the site of a former aboveground solvent tank, otherwise known as <br /> Solid Waste Management Unit (SWMU) 20. The area around the tank contained a floor <br /> drain and a former paint spray booth, both connected to the industrial waste pipeline <br /> designated as SWMU 33. Remedial Investigations at Warehouse 10 in 1996 detected a <br /> variety of volatile organic compounds and semi-volatile organic compounds in samples <br /> of sludges from the floor drain, sumps, and soil samples resulting in three separate soil <br /> removal actions taken in September 1997, July 1998, and June 1999. <br /> The April 2008 Army Corps of Engineers Warehouse 10 Investigation performed 15 soil <br /> borings with 14 additional step-out locations at depths ranging from 4.5 to 19 feet below <br /> ground surface (bgs). Three discrete soil and soil vapor samples were taken at each <br /> boring location with groundwater samples taken at the bottom of each boring at depths <br /> ranging from 23 to 30 feet bgs. <br /> DTSC has reviewed the work plan and has the following comments: <br />