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ATTACHMENT A <br /> SITE INVESTIGATION HISTORY (Continued) <br /> l <br /> from all 20 borings were reported as non-detect for TPHd, TPHg, benzene and toluene <br /> (G&M 1994) <br /> A groundwater remediation system was installed at the site in January 1994 for product <br /> recovery and hydraulic containment Extraction of groundwater from five wells on site was <br /> initiated in February 1994, and continued until February 1996 Two wells, MW-18 and MW- <br /> 19, were used for hydraulic containment of the groundwater plume and three wells, MW-14, <br /> MW-15, and MW-16, were utilized for product recovery <br /> A dual extraction system (DE) began continuous operation on March 25, 1996 The DE <br /> system was comprised of 14 DE wells (MW-1, MW-2, MW-7, MW-8, MW-14, MW-15, <br /> MW-16, and DE-1 through DE-7), a water knockout tank, an oil/water separator, four <br /> granular activated carbon vessels arranged in series for groundwater treatment, and a thermal <br /> oxidizer for vapor treatment In May 1997, Chevron determined that the SPH plume on site <br /> had been removed by the DE system In addition, influent water concentrations had declined <br /> significantly and influent vapor concentrations had declined to near non-detect levels since <br /> system startup The DE system was shut down in June 1997 Temporary shutdown of the <br /> DE system was approved by Ms Gail Wiggett of the RWQCB in a meeting on June 2, 1997 <br /> SECOR has since been working on a six month ISO-GEN pilot test This pilot test includes <br /> the installation of six four-inch test wells (TW-1 through TW-6) and nine two-inch ISO-GEN <br /> monitoring wells (MW-24A through MW-32A) Most recently, SECOR has been <br /> performing fieldwork associated with planned changes to the existing groundwater <br /> monitoring and reporting program <br />