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1.INTRODUCTION <br /> response to the positive results after the initial year of the 3-year bioremediation pilot <br /> study. <br /> • Soil Vapor Extraction and Treatment System(SVETS). A SVETS was constructed <br /> beginning in 1999 and was operated from 2000 to 2001. A pilot test was performed for <br /> one soil vapor extraction (SVE)well (VEW-1) in 1998. During operations, soil vapor was <br /> extracted from nine extraction wells (VEW-2 through VEW-10), treated with three <br /> internal combustion (IC) engines, and discharged under a permit with the San Joaquin <br /> Valley Unified Air Pollution Control District. <br /> • Multiphase Extraction (MPX). Pilot testing of the SVETS to conduct MPX of soil vapor <br /> and shallow groundwater was performed from 2002 through 2004, at which time it was <br /> shut down for the 3-year bioremediation pilot study. MPX was conducted to enhance <br /> removal of hydrocarbon within the smear zone at the water table. During MPX pilot <br /> testing, soil vapor, groundwater, and NAPH were extracted using a single IC engine <br /> from four extraction wells (SVE-2 through SVE-5). Soil vapor was treated with the <br /> IC engine and discharged under a permit issued by the San Joaquin Valley Unified Air <br /> ' Pollution Control District. Water and NAPH were treated by the groundwater treatment <br /> 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 /> rThree-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 evaluation of the pilot study also concluded that <br /> monitored natural attenuation(NINA) is effective at the Site (CH2M HILL,2007a). The <br /> RWQCB agreed with the conclusions that MNA is occurring in a letter to SFPP dated <br /> November 14, 2007. The hydrocarbon plume and groundwater concentrations are <br /> monitored under current MRP No. R5-2007-0831 to document that the hydrocarbon plume <br /> and groundwater concentrations are stable and decreasing under NINA conditions. SFPP <br /> removed the GWETS after the initial year of the pilot study, and in a letter dated July 7, <br /> 2005, the RWQCB rescinded the NPDES permit under which the GWETS operated. SFPP <br /> removed the aboveground portions of the groundwater treatment system in October 2005. <br /> Trees were planted in the footprint of the former groundwater treatment system as part of <br /> the 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 for the Source Area (CH2M HILL, <br /> 2004). 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 /> WBG101513183707SC0/HOLT_2SA13_REPORT_FINAL 1-3 <br />