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1.INTRODUCTION <br /> 1998. During operations, soil vapor was extracted from nine extraction wells (VEW-2 <br /> through VEW-10), treated with three internal combustion(IC) engines,and discharged <br /> under a permit with the San Joaquin Valley Unified Air Pollution Control District <br /> (SJVUAPCD). <br /> • Multiphase Extraction. Pilot testing of the SVETS to conduct multiphase extraction <br /> (MPX) of soil vapor and shallow groundwater was performed from 2002 through 2004, <br /> at which time it was shut down for the 3-year bioremediation pilot study. MPX was <br /> conducted to enhance removal of hydrocarbon within the smear zone at the water table. <br /> During MPX pilot testing, soil vapor, groundwater, and NAPH were extracted using a <br /> single IC engine from four extraction wells (SVE-2 through SVE-5). Soil vapor was <br /> 1 treated with the IC engine and discharged under a permit with the SJVUAPCD. Water <br /> and NAPH were treated through the groundwater treatment system described above. <br /> 1.2.3 Current Site Remediation Activities <br /> The following remediation activities are currently being implemented to contain and <br /> remove hydrocarbons from the subsurface. <br /> Three-Year Bioremediation Pilot Study and Monitored Natural Attenuation <br /> The 3-year bioremediation pilot test was implemented from 2004 to 2007 in accordance with <br /> the Bioremediation Pilot Study work plan(CH2M HILL, 2003). The 3-year final evaluation <br /> report for the pilot study concluded that natural processes were sufficient to contain the <br /> hydrocarbon plume and maintain the stable-to-decreasing trend in hydrocarbon <br /> concentrations in groundwater. The pilot study evaluation also concluded that monitored <br /> natural attenuation(MNA) is effective at the Site (CH2M HILL, 2007a). In a letter to SFPP <br /> dated November 14, 2007, the RWQCB concurred with the conclusions that MNA is <br /> occurring. The hydrocarbon plume and groundwater concentrations are monitored under <br /> current MRP No. R5-2007-0831 to document that the hydrocarbon plume and groundwater <br /> concentrations are stable and decreasing under MNA conditions. SFPP removed the GWETS <br /> after the initial year of the pilot study, and the RWQCB subsequently rescinded the NPDES <br /> permit in a letter dated July 7, 2005,under which the GWETS operated. SFPP removed the <br /> aboveground portions of the groundwater treatment system in October 2005. Trees were <br /> planted in the footprint of the former groundwater treatment system as part of the <br /> phytoremediation system. <br /> Phytoremediation System <br /> Phytoremediation is being implemented as the final remedial measure in the source area in <br /> accordance with the Cleanup Plan Using Phytoremediation (CH2M HILL, 2004). <br /> Construction of the phytoremediation system was conducted in two phases: <br /> • Phase 1 (Areas A, AA, and B) was constructed in January/February 2005. <br /> • Phase 2 (Areas C and D) was constructed in March/April 2006. <br /> Construction of Phases 1 and 2 is documented in two respective as-built reports <br /> (CH2M HILL, 2005 and 2007b). <br /> ES041514081714SCO/HOLT_1SA14_TEXT_FINAL 1-3 <br />