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lie 06 October 2005 AGE-NC Project No 99-0657 Page 5 of 6 4.0. SUMMARY AND CONCLUSIONS The following conclusions were drawn from the results of this investigation • The ground water elevation averaged approximately 6 23 feet above MSL Ground water is Inferred to be flowing toward the southwest under an average ground water gradient of I0 004 ft/ft which is consistent with previous monitoring events • The highest concentrations of dissolved hydrocarbons occurred in monitoring wells MW-1, and MW-4, which are located at or down-gradient of the UST area Concentration maps depicting the approximate distribution of dissolved TPH-g, benzene, MTBE and 1,2-DCA are presented as Figures 4 through 7, respectively • Concentrations of dissolved TPH-g decreased this quarter in monitoring wells MW-1, MW-2 and MW-6 and decreased to non detect in MW-3 TPH-g increased in MW-4 and perimeter well MW-5 Concentrations of benzene decreased to non detect in samples from wells MW-2 and MW-3 since the previous monitoring event • MTBE concentrations decreased in wells MW-1, MW-2 and MW-6, and decreased to non I . detect in well MW-3 1,2-DCA concentrations decreased in wells MW-1,MW-2 and MW-6, and decreased to non detect in well MW-9 • No target analytes were detected at or above laboratory reporting limits in the ground water isamples analyzed from wells MW-10 and MW-11 The lateral extent of petroleum hydrocarbon contamination in ground water has been defined i to the east, south and north(CPT-1) of the UST area The lateral extent in not fully defined to the west of the UST area beyond wells MW-5 and MW-6 (Figures 4 through 7) i The vertical extent of petroleum hydrocarbon-impacted ground water is defined off-site in the area of soil boring CPT-1 The vertical extent of petroleum hydrocarbon-impacted ground water is defined on-site by wells MW-10 and MW-11 i i5.0. RECOMMENDATIONS Based on the findings of this investigation, AGE recommends iContinuation of the quarterly ground water monitoring program, as required by the EHD • Preparation of a remediation feasibility report for soil and ground water i • iAdvanced GeoEnvnronmental,Inc i