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0 ganHydrninnic consultants, Inc. soil vapor extraction wells VW-1, VW-2 (A,B), VW-3, VW-4 (A,B,C), VW-5 (A,B,C), and VW-6(A,B,C). The system operated until November 26,2007,when it was shut down and kept offline through the first quarter 2008 due to the UST removal and well abandonment/reinstallation activities described later in the report. As of November 26, 2007, a total of 191,127 pounds of hydrocarbons have been removed by the soil vapor extraction (SVE) unit, as documented in the Fourth Quarter 2007 Status Report. 2.6 Groundwater Treatment System The groundwater treatment system was started in conjunction with the vapor treatment system on April 26,2001, and the flow meter started at zero. During its operation,the remediation system extracted groundwater from well MW-11, with groundwater routed into a 150-gallon polyvinyl tank, which then transfers the water through two (2) one thousand-pound granular activated carbon canisters in series. On September 27,2005, the groundwater treatment system was shut down and remained off due to the strict City of Stockton discharge permit requirements imposed in November 2005, which require very low TBA discharge concentrations. A total of 582,804 gallons has been treated and discharged since the commencement of groundwater treatment through September 27, 2005. Based on a March 9, 2006 status update letter to the SJCEHD,Thrifty noted that the current configuration of the groundwater treatment system was not designed to remove all oxygenates to the levels now required by the new discharge permit issued by the City of Stockton. On behalf of Thrifty, GHC has prepared and submitted to the SJCEHD on April 14, 2008 a Workplan for Remediation System Modification, which detailed upgrades to the existing MPE system. The proposed upgrades to the existing MPE system are to remove onsite petroleum hydrocarbons in soil and dissolved phase in groundwater, and meet current City of Stockton groundwater discharge permit requirements. Drawings of the proposed MPE system upgrade are included in Appendix F. Because of the MTBE/TBA discharge requirements, as of the beginning of the second quarter 2008, the groundwater system has remained offline,but the vapor system continues to operate. 2.7 Contaminants of Concern The contaminants of concern in both soil and groundwater at the Site include fuel hydrocarbons(which include BTEX),and oxygenates (MTBE and TBA). The most recent soil sample data of hydrocarbon concentrations in soil were located from 20 to 65 feet below the surface at MW-12, from 20 to 40 feet below the surface at VW-2, from 40 to 45 feet below the surface at VW-4,and from 25 to 45 feet below the surface at VW-6(Thrifty, 1999). GHC estimates that the original hydrocarbon mass in soil at the Site, before the soil vapor and groundwater extraction and treatment system was installed, TOC 172 UST Removal Report Final Page 6