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Department of Toxic Substances Control <br /> A <br /> Maureen F. Gorsen, Director <br /> Alan C.Lloyd, Ph.D. 8800 Cal Center Drive Arnold Schwarzenegger <br /> Agency secretary Sacramento, California 95826-3200 Governor <br /> CaVEPA <br /> April 18, 2006 APR `L zVU6 <br /> ENVIRONMENT HEALTH <br /> PERMIT/SERVICES <br /> Mr. Marshall Cloud <br /> Remedial Project Manager <br /> Defense Distribution Depot—Tracy Site <br /> Post .Office. Box 960001 <br /> Stockton, California 95296-0250 <br /> COMMENTS ON THE DRAFT DIELDRIN NATURAL ATTENUATION INVESTIGATION <br /> WORK PLAN DATED MARCH 13, 2006, FOR DEFENSE DISTRIBUTION DEPOT <br /> SAN JOAQUIN CALIFORNIA (DDJC), TRACY SITE, SAN JOAQUIN COUNTY, <br /> TRACY, CALIFORNIA <br /> Dear Mr. Cloud: <br /> The Department of Toxic Substances Control (DTSC) received the above-mentioned <br /> work plan on March 14, 2006, submitted by the URS Corporation on behalf of <br /> DDJC-Tracy. The work plan proposes a soil and ground water cone penetrometer test <br /> (CPT) investigation to collect the necessary data to evaluate the hypothesis that natural <br /> attenuation of dieldrin is occurring in ground water beneath two areas of DDJC-Tracy. <br /> The work plan proposes a total of thirty-six co-located soil and ground water samples <br /> collected from seven locations within the Northwest Corner (NWC) dieldrin plume and <br /> two locations within the Sanitary Sewage Lagoon. The soil and ground water samples <br /> will be collected from four depth intervals within the Above Upper to Upper <br /> hydrogeologic horizons at the nine locations. Sampling depths and locations were <br /> selected from within and outside of current estimated plume extents in an effort to <br /> associate soil characteristics in both areas to dieldrin concentrations detected during <br /> previous sampling events. <br /> DTSC has reviewed the work plan and has the following comments: <br /> ® Printed on Recycled Paper <br />