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June 10, 2004 <br /> Michael Lozano <br /> Department of Toxic Substances Control <br /> School Property Evaluation and Cleanup Division <br /> 8800 Cal Center Drive <br /> Sacramento, CA 95826-3200 <br /> Subject: Supplemental Site Investigation Soil Gas Survey and Additional Soil Sampling for the <br /> Proposed Pittman Elementary School, Stockton, California <br /> Dear Mr. Lozano: <br /> Please find enclosed a copy of the analytical results from the initial Supplemental Site Investigation(SSI) <br /> soil and soil gas sampling that occurred at the proposed Pittman Elementary School in downtown <br /> Stockton, California, on April 9 and 13 through 15,2004. <br /> The soil gas results confirmed the presence of constituents of concern identified in the Preliminary <br /> Environmental Assessment (PEA) conducted last year at the site. Based on these results and <br /> recommendations from the Department of Toxic Substances Control, Condor Earth Technologies, Inc. <br /> (Condor)proposes advancing an additional two borings for evaluation of the lithology and 15 borings for <br /> soil gas sample collection at two depths. The soil gas sampling depths will be determined based on <br /> evaluation of the lithology for the depths of highest permeabilities. The lithology borings will be <br /> advanced to a depth of approximately 25 feet below ground surface (bgs). The proposed locations of the <br /> additional borings are indicated on the attached figure. The 15 borings for soil gas sample collection are <br /> spaced approximately 200 feet from each other in a grid-like manner. <br /> In addition to the 30 soil gas samples to be collected from the borings,two duplicate soil gas samples and <br /> two equipment blank samples will be collected for quality assurance/quality control purposes. The <br /> duplicate samples will be collected immediately following the collection of the primary samples and will <br /> not be identifiable as a duplicate sample to the laboratories. The equipment blank samples will be <br /> collected by running purified nitrogen gas through the sampling equipment and into the 1-liter Summa <br /> canisters. The duplicate samples, their primary counterparts, and the equipment blank samples will be <br /> collected in certified clean 1-liter Summa canisters. The remaining soil gas samples will be collected in <br /> standard 1-liter Summa canisters, 10 percent of each batch of containers being certified clean by the <br /> laboratory. The samples will be analyzed for volatile organic compounds by EPA Method TO-15. Soil <br /> gas sampling will be conducted in accordance with the DTSC Advisory—Active Soil Gas Investigations <br /> dated January 28, 2003. <br />