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1e 7 7 77- . <br /> 5 , <br /> t <br /> 4 1 <br /> 1 ' <br /> F 1 <br /> • 08 November 1999 <br /> AGE-NC Project No 98-0448 <br />' Page 3 of 4 <br /> I4.0. . DISCUSSION AND CONCLUSIONS <br /> The following is a summary based on the findings of the September 1999 Investigation <br />' The round water surface elevation at the site Is approximately 25 feet above the slotted <br /> • g pp y bo 0 <br />' screen Interval in well MW-4B and approximately 1 to 2 feet above the slotted screen <br /> Interval of MW-1, MW-2 and MW-3 The ground water elevation at the site was within the <br /> screened interval of wells MW-4A, MW-5, MW-6, MW-7 and MW-8 <br />' • From March 1999 to June 1999, a substantial decrease in concentrations of dissolved <br /> petroleum hydrocarbons was quantified In ground water samples collected from well MW-1 <br /> (Table 2) <br /> Based upon data collected during the September 1999 monitoring, AGE concludes <br /> • A southeast groundwater flow direction in the area bound by wells MW-1, MW-2, MW-4A, <br /> MW-6, MW-7 and MW-8 ata gradient of 0 015 ft/ft, a west-northwest ground water flow <br /> lie direction in the area bound by wells MW-3, MW-5 and MW-8 at a gradient of 0 004 ft/ft <br /> o A general trend of decreasing ground water elevations has been observed at the site since <br /> March 1999 <br /> © Well MW-4B yields data representative of deeper ground water conditions <br /> I • The elevated petroleum hydrocarbon concentrations detected In water samples collected from <br /> wells MW-1/MW-2 (screened between 20 and 40 feet bsg), MW-4A (screened between 8 <br /> and 33 feet bsg) feet and MW-4B (screened between 45 and 50 feet bsg) suggest that these <br /> wells may be screened within or near the dissolved petroleum hydrocarbon "core area" of <br /> the plume _ , <br /> • The significant Increase in quantified dissolved petroleum hydrocarbons detected from well <br /> MW-4B (screened 45 to 50 feet bsg) may be related to the installation of the adjacent <br /> extraction well EW-1 (screened 15 to 45 feet bsg) ' <br /> • An air sparging pilot test performed at the site on 25 August 1999 may have contributed to <br /> the significant decrease in quantified dissolved petroleum hydrocarbons detected from wells <br /> MW-1 and MW-2 (screened 20 to 40 feet bsg) <br /> • The dissolved petroleum hydrocarbon plume appears to be sufficiently contained within the <br />' current array of ground water monitoring wells <br /> IAdvanced GeoEnvironmental,Inc <br /> t <br /> 4 <br />