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31 January 2003 , AGE-NC Project No 96-0232 4 ' Page 7 of 17 j water,to date;the ground water treatment system has removed a total of approximately 10 56 pounds ' of MTBE from extracted ground water(Table 8) Fourth quarter 2002 mass-volume calculations of MTBE-impacted groundwater extracted from the groundwater pump-and-treat system are presented in Appendix D Plots of cumulative ground water pump and treat mass removal trends and Influent ' ground water MTBE concentrations versus time are In Appendix E 1 3.0. GROUND WATER MONITORING AND SAMPLING , On 04, 05 and 06 December 2002, ground water monitoring and sampling were performed at 35 ground water monitoring wells(MW-1 through MW-18),at ten ground water extraction wells(EW-1 through EW-10)and two San Joaquin County service area No 31 municipal water wells(CSA-1 and CSA-2) Quarterly ground water monitoring procedures for the site were outlined in the AGE- prepared Work Plan Addendum, dated 28 January 1998, and approved by,the San Joaquin County Environmental Health Department(SJCEHD)by letter dated 24 February 1998 As-built monitoring Iwell construction details are summarized in Table 9 A coordinated effort was made with Three B's Truck Plaza (14749 Thornton Road, Lodi CA) to conduct groundwater monitoring activities concurrently,the Three B's Truck Plaza tabulated ground j water elevation results are In Appendix F 3 1 WELL MONITORING AND PURGE PROCEDURES On 04 December 2002, the depth to groundwater was measured at each monitoring well from the top of each well casing to the nearest 0 01-foot,utilizing a Solinst water level meter The ground water elevation in each monitoring well was calculated by subtracting the measured depth to ground water'from the surveyed casing elevation (Table 4) Ground water elevation and vertical gradient data for wells MW-9, MW-11 and MW-13 are depicted in cross section C-C' (Figure 3), ground water elevations were plotted for the informal First Zone,Second Zone,Secondary Aquifer Zone and Primary Aquifer Zone hydrogeologic flow units as defined in AGE's Final Remediation Plan (Figures 4, 5 and 6) IOn 05 and 06 December 2002, approximately 5 to 30 gallons of ground water(a minimum of three casing-water volumes per well) were evacuated (purged) from wells MW-1 through MW-7 and MW-14 through MW-18 utilizing either disposable polyethylene bailers or submersible two-stage pumps, approximately 75 to 85 gallons of ground water were purged from wells EW-1 and EW-3 utilizing a two-stage submersible pump Temperature, pH and conductivity were measured for stabilization at regdlar purge-volume intervals from each well using an Oakton water analyzer Field data and logs are provided in Appendix G The purged ground water was transferred to the ground . water remediation system holding tank for treatment and disposal Advanced GeoEnvi ron mental,Inc E ' o ! E ' ! 5