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I ' 13 AP nl 2001 AGE-NC Project No 96-0232 ' Page 12 of 14 ' • Due to the tow ground water gradient at the site, small variations in ground water measurements or changes of recharge/discharge of the local ground water could greatly modify the Inferred ground water flow direction ' • Increasing ground water elevations have been reported at the site since the August 2000 - monitoring event (third quarter 2000), hydrographs depicting recorded ground water ' elevations at wells MW-2, MW-6A and MW-6B vs time are included with Appendix J • The greatest concentration of dissolved MTBE in on-site First Zone monitoring wells was ' detected in MW-1 at a concentration of 120,ug/1 (Figure 7), lesser concentrations of MTBE were detected from MW-7 and MW-12A Dissolved MTBE was also detected in Second Zone monitoring wells MW-6B, MW-9A and MW-11A (Figure 8) • The greatest concentrations of dissolved MTBE detected in on-site First Zone extraction wells were in samples collected from EW-4 at concentrations as high as 540,ug/l (Figure 9), lesser concentrations of MTBE were detected in samples from extraction wells EW-2,EW-5, ' EW-8, EW-9 and EW-10 • The greatest concentration of off-site dissolved MTBE was detected near the Rocky's • Restaurant domestic water well in MW-11A (screened 40 to 50 feet bsg) and MW-11B (screened 65 to 75 feet bsg) at concentrations of 210 and 240 4g/l, respectively, low concentrations of MTBE were detected off-site from MW-6B (screened 43 to 48 feet bsg), MW-7 (screened 4%2 to 24%2 feet bsg), MW-11D (screened 130 to 150 feet bsg), MW-12A and MW-13A(screened 10 to 20 feet bsg) at concentrations as high as 6 7,ug/l (MW-7) CP Low concentrations of dissolved TPH-d were encountered in MW-6A(screened 7 to 27 feet bsg), MW-10A (screened 15 to 20 feet bsg), MW-11B (screened 65 to 75 feet bsg) and MW-12A(screened 10 to 20 feet bsg) I 5.0. CONCLUSIONS ' AGE interprets the results of all work completed to indicate a Fla CI Chevron release of rP P g City hydrocarbons and MTBE occurred in the areas of the fuel dispensers, UST pit and/or storm drain, migrated through the First Zone and upper Second Zone to the Rocky's Restaurant domestic well, at which point It apparently migrated vertically to the Rocky's Upper, Secondary Aquifer and Primary Aquifer Zones Substantial decreases of dissolved MTBE were detected in samples collected from monitoring well MW-1, extraction wells EW-2, EW-5, EW-6, EW-7, EW-8, EW-9, EW-10 and Influent ground water pump and treat samples collected between the December 2000 and the March 2001 sampling events, this data implies that the reported decreases maybe due to the overall MTBE mass reduction Advanced GcoEnvsronmental,Inc. I