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investigation findings concluded that with the exception of low levels of TPHd, MTBE, DIPE, and TAME, the plume downgradient of well MW-35 was defined. Remedial Activities 1987 through 2006: During 1987, a separate-phase hydrocarbon recovery program was initiated and product was recovered from wells MW-1, MW-15, and MW-17. Extracted fluids were transported to Shell's Martinez refinery. Groundwater extraction(GWE) began at the site in early 1993. The pumping wells were MW-1, MW-23, and MW-24. The GWE system was shutdown after two months of operation due to limitations placed on the treatment of wastewater at the Shell refinery. PEG's March 23, 1994 Remedial Action Plan, identified soil vapor extraction (SVE) with continued GWE as the preferred methods for soil and groundwater remediation. A surface water discharge permit was obtained and the GWE system was restarted during November 1994. Two additional extraction wells, MW-11 and MW-16, were added to the system. Treated groundwater was discharged to the Stockton Deep Water Channel under a NPDES permit. During April 1995, well MW-17 was added to the GWE system. During the third quarter 2000 well MW-13 was added to the GWE system. During April 2001, the system was shut down due to more stringent NPDES permit requirements. During October 2003, the GWE system was restarted and discharge to the sanitary sewer began. The pumping wells were initially wells MW-10, MW-15, and MW-16. The system operated until December 3, 2003, when methane concentrations triggered an LEL shutdown. The system was not restarted until February 2005 and operated for a short period of time when another LEL shutdown occurred on March 8, 2005. The system was restarted and samples were collected on March 9, 2005 and the effluent contained TBA levels exceeding the permit discharge limit of 5 ug/L. The City of Stockton issued a Notice of Violation on May 9, 2005 for LEL and TBA exceedances. The GWE system has not discharged to the POTW since this time. A detailed description of GWE operations is presented in RETEC's January 30, 2004 report. SVE operations began on April 16, 1996 and operated intermittently until May 23, 2001. The SVE system consisted of a Thermtech VAC-250 thermal oxidizer unit that was connected to wells MW-1, MW-11, MW-15, MW-16, MW-17, MW-23, and MW-24. The system was shutdown due to high water levels and the lack of available vadose screen for SVE(RETEC November 1,2004). During 2004, the feasibility of performing an oxygen injection pilot test was evaluated (RETEC, November 24, 2004). During 2005 several oxygen injection wells and downgradient monitoring points were installed along the southern property boundary near wells MW-20 through MW-22. As reported in RETEC's February 6, 2006 report, the pilot testing was cancelled because the TPHg concentrations were not low enough to be sufficiently reduced by oxygen injection. Alternatively, a temporary pumping system was proposed. 1729 4