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30 January 2004 AGE-NC Project No 96-0232 Page 11 of 15 4.0 SUMMARY OF FINDINGS FROM QUARTERLY ACTIVITIES Previous soil characteristics data obtained by a CPT Investigation enabled AGE to define five informal hydrogeologic units (Final Remediation Plan, dated 31 August 2000) The informal hydrogeologic units were defined as First Zone (10-35 feet bsg), Second Zone (40-60 feet bsg), Rocky's Upper Zone (65-75 feet bsg), Secondary Aquifer Zone (85-105 feet bsg), and Primary Aquifer Zone (130-150 feet bsg) The Rocky's Upper Zone was the shallowest ground water zone screened in the destroyed Rocky's domestic drinking water well The results of pump and treat ground water remediation between 15 September 2003 and 09 December 2003 is as follows • Approximately 1,109,431 gallons of MTBE-impacted ground water were extracted from wells EW-4, EW-5, EW-7 and EW-8, which were completed in the First Zone aquifer (Appendix A, Table 8) A total volume of approximately 23,535,076 of MTBE-impacted water has been treated at the site since the start-up period in November 2000 (Table 8) • Steady, but low MTBE concentrations were detected from water samples collected at the influent end of the treatment system at concentrations of 31 µg/1, 27 gg/l and 20 µg/1 • Laboratory analysis of pump-treat effluent samples and did not detect any MTBE during the fourth quarter 2003 Between 15 September 2003 and 09 December 2003,the mass of MTBE removed from the extracted ground water was calculated to be 0 24 pounds (Table 8, Appendix D) A plot of cumulative ground water pump and treat mass removal versus time and a plot of influent ground water MTBE concentrations versus time are Included in Appendix E The results from the ground water monitoring and sampling events performed in December 2003 are as follows • Generally,depth to ground water at the site vaned between 12 and 16 feet bsg, ground water elevations ranged between 3 86 feet (MW-13A) and 4 55 feet (MW-8C) below MSL (Table 4) • First Zone ground water was inferred to be radially inward towards a ground water depression in the area of Flag City Chevron wells MW-1, MW-2 and MW-4 at hydraulic gradients of 0 004 ft/ft or less Second Zone ground water was inferred to flow radially- inward in the areas of Flag City Chevron wells MW-6B at hydraulic gradient of 0 002 fl/ft or less Secondary Zone ground water was inferred to be towards the east at hydraulic gradients of 0 001 ft/ft or less Primary Aquifer Zone ground water gradient at the site was essentially flat Due to the low ground water gradient at the site, small variations in ground Advanced GeoEnvironmental,Inc.