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I 13 October 2000 ' AGE-NC Protect No 96-0263 Page 3 of 4 exception of xylenes in MW-8 at concentrations ranging from 0 88µg11 of toluene in MW-8 to 4,500 µg/1 of toluene in MW-2 MTBE was detected by EPA method 8020 in monitoring wells MW-2, MW-4, MW-5, MW-7 and MW-8 at concentrations ranging from 43 4g11 in MW-8 to 9,700µg11 in MW-2 and MW-7 MTBE I was reconfirmed by EPA method 8260m and was detected in the same wells at concentrations ranging from 45 ,ug/l in MW-8 to 9,900 µg/l in MW-2 No other oxygenates were detected in the ground water samples The current and past ground water sample analytical results are summarized on Table 2 The laboratory report (MAI Sample ID Nos 47359-47366), QA/QC report and chain-of-custody form I are included in Appendix B Figures 4 and 5 depicts the approximate areal distribution of Impacted ground water containing benzene and MTBE, respectively, for the September 2000 ground water monitoring event I 4.0. SUMMARY AND CONCLUSIONS The following conclusions were drawn from the results of this investigation 1 Depth to ground water ranged from 6 76 feet to 7 77 feet below the well casing tops The 1 prevailing ground water flow direction In September 2000 Is towards the north The f hydraulic gradient (0 004 feetifeet) indicates that the ground water table Is nearly flat • The dissolved hydrocarbon plume extends northward from the former UST and dispenser areas and beyond the two down-gradient monitoring wells (MW-5 and MW-8) The plume Iis defined to the south and west by momtonng wells MW-1 and MW-3, respectively • The hydrocarbon and MTBE concentrations in MW-7 and MW-8 have decreased and r concentrations in MW4 and MW-5 have remained relatively stable since the last monitoring event in April 2000 Significant increases of TPH-g and toluene concentrations occurred in MW-2 between the April 2000 and September 2000 monitoring events 5.0. RECOMMENDATIONS Based on the findings of the this investigation, AGE recommends • Installation of additional ground water monitoring wells north, east and northwest of the estimated limits of the hydrocarbon plume to further assess the lateral extent of dissolved Advanced GeoEnvironmental,Inc