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First Quarter 2004, Quarterly Progress Report April 14, 2004 Page 2 3.0 EVALUATION OF GROUNDWATER EXTRACTION GWET and Soil Vapor Extraction (SVE) systems were activated on July 3, 2000. A brief description and performance evaluation of the remedial systems during 1Q04 are presented below. Certified laboratory analytical reports and chain -of -custody documentation and remedial system operation and maintenance field data sheets are included in Appendices D and E, respectively. On August 20, 2003, SVE was discontinued as approved by the Regional Water Quality Control Board (RWQCB) in their letter dated August 18, 2003. A copy of this letter is included in Appendix F. 3.1 Groundwater Extraction System The GWET system includes groundwater extraction wells EX -1, EX -2 and EX -3 (Figure 5). These wells are equipped with submersible pumps connected through mechanical piping to a series of granular activated carbon (GAC) vessels prior to an industrial sewer discharge point. Chevron discharges treated groundwater at the subject site under City of Lodi (City) wastewater discharge permit #328. To assess effectiveness of the GWET system, process samples were collected monthly during this reporting period. Sample locations include a influent port (INFL) prior to the first GAC vessel, between the first and second GAC vessels (MID -1), between the second and third GAC vessels (MID -2), and before discharge (EFFL) to the industrial sewer. During these sampling events, INFL, MID -1, MID -2 and EFFL samples were analyzed for TPHg, BTEX, MtBE, TSA, DIPE, EtBE, TAME, ethanol, methanol, EDB and 1,2 -DCA. Maximum concentrations of detected constituents are presented below. Current and historical analytical information is presented as Table 3. Zone Maximum Constituent Concentrations (µg/l) MtBE TBA EtBE TAME Ethanol Methanol INFL 9 <10. <2. <2. <100. <400. MID -1 <2. <10. <2. <2. <100. <400. MID -2 <2. <10. <2, <2. <100. <400. EFFL_ <2. <10. <2. <2. <100. <400. Explanations: < Indicates the constituent was not present at or above the method detection limit shown Between December 12, 2003 and March 09, 2004, the GWET system discharged a total of 765,216 gallons of treated groundwater (Table 4). As of March 09, 2004, the GWET system had treated a total of 9,428,621 gallons. Calculated discharge rates during the 1004 monitoring period ranged from 5.58 to 6.77 gallons per minute (gpm). During 1Q04, the system extracted an estimated 0.2 pounds of TPHg. To date, the system has extracted approximately 9.7 pounds of TPHg, 0.2 pound of benzene, and 85.0 pounds of MtBE. Plots of GWET system mass removal trends and influent groundwater TPHg, benzene, and MtBE concentrations versus time are shown on Figure 6 and 7, respectively. L\Chevron1957751Periodic Monitoring\Q P R1200411st Quarter -2004 QPR,doc