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Former Unocal #0187 • • Page 2 <br /> 437 E. Miner Avenue August 22, 2008 <br /> Stockton, CA <br /> recent soil sample analytical results to those collected in July 1994 it does not appear that the <br /> contamination has degraded much since July 1994. <br /> In the 'Proposal for Site Assessment and Remedial Alternative Evaluation" dated December 3, <br /> 2007, prepared by ENSR it recommended conducting a pilot test using the existing microsparge <br /> points to evaluate the integrity of the sparge points and collect design parameters for a <br /> biosparge system. On December 18, 2007, the EHD had a telephone conversation with <br /> Barbara Jakub of ENSR who clarified that the information from the MIP/CPT investigation would <br /> be used to determine where biosparge wells should be located and screened to conduct the <br /> pilot test and if the microsparge wells were located and screened appropriately then they would <br /> be used in the pilot test. The report on the proposed MIP/CPT work was to include a detailed <br /> proposal for conducting a pilot test for a biosparge system and it does not contain any <br /> recommendations or proposals. <br /> In November 2006 a soil vapor study was conducted at this site. The concentration of TPH-g in <br /> the samples collected exceeded the San Francisco Bay Regional Water Quality Control Board <br /> Environmental Screening Levels. There was discussion that the tracer gas may have caused <br /> false positives so further evaluation of the soil vapor issues was to be conducted. To date there <br /> has been no other proposals submitted to evaluate the soil vapor concerns. <br /> The Assessment states that a sampling bailer and sediment were found in U-17 and that the <br /> bailer was removed but the sediment remains. There is no recommendation for removal of the <br /> sediment such as redeveloping the wells. <br /> A plan for conducting a soil vapor study, testing other remedial alternatives and <br /> restoring U-17 to its original condition is to be submitted to the EHD by October 13, 2008. <br /> If you have any questions contact me at (209) 468-3449. <br /> Margaret Lagorio, REHS <br /> Program Coordinator <br /> cc: Jim Barton, CVRWQC13 <br /> David Irey, San Joaquin County District Attorney's Office <br /> Kent Baugh, ENSR, 300 Lakeside Drive, Suite 220, Oakland, CA, 94612 <br /> David Evans, ARCADIS, 950 Glen Drive, Suite 125, Folsom, CA 95630 <br />