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f • 01 October 2004 ' AGE-NC Project No 97-0333 Page 9 of 11 ' 4.0. SUMMARY AND CONCLUSIONS Previous soil characteristics data obtained by a CPT Investigation enabled AGE to define four ' Informal hydrologic units(CPT Site Investigation -Fourth Quarter 2000,dated 07 February 2001) The informal hydrogeologic units were defined as First Zone(15-47 feet bsg), Second Zone(58-92 feet bsg, Third Zone (102-120 feet bsg) and Primary Aquifer Zone (128-150 feet bsg) ' The results of pump and treat ground water remediation between 26 December 2003 and 10 March 2004 are as follows • Approximately 280,576 gallons of hydrocarbon-impacted ground water were extracted from well EW-1,which was completed in the First Zone aquifer A total volume of approximately 2,152,204 gallons of hydrocarbon-impacted ground water has been treated at the site since the start-up period in January 2002 (Table 5) ' • Dissolved MTBE was detected from grab samples collected at the influent-end of the treatment system at concentrations between 5,300 µg/1 and 6,300 µg11, laboratory analysis of grab water samples collected at the effluent-end did not detect any constituents of concern lieduring the first quarter 2004 (Table 1) • Between 26 December 2003 and 10 March 2004, an estimated 13 56 pounds of MTBE was ' extracted from ground water(Table 5,Appendix B),a total mass of 233 90 pounds of MTBE has been removed since Initiation of the pump and treat system on 21 January 2002 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 C, although a slight increase was reported during the first quarter 2004 monitoring events, the overall general trend of decreasing MTBE concentrations is evident ' ' The results from the ground water monitoring and sampling events performed on 31 March 2004 are as follows • Generally,depth to ground water at the site vaned between 20 and 23 feet bsg,ground water t elevations ranged between 9 97 feet (MW-11C) and 11 81 feet (MW-1) above mean sea level The ground water elevation Increased approximately 3 53 feet between November 2003 and the March 2004 ground water monitoring events, the average increase in may be ' due to seasonal fluctuation • First Zone ground water flow was inferred to be towards a ground water depression in the area of wells EW-1,MW-6 and MW-7A at an approximate of gradient 0 004 ft/ft(Figure 4) ' Advanced GeoEnviron mental,Inc I