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c ` t 08 Decemfber 2000 AGE-NC Project No 95-0103 k , Page 4 of 5 , s ' each monitoring event A minimum pressure of 2 psi was maintained for the air sparging system The SVE unit operated at an extraction flow rate of 185 scfrn An induced vacuum(negative pressure) of 32 inches of water was measured in the'piping between the blower and extraction wells ' TPH-g and BTEX compounds were not detected in the extracted soil gas sample collected during the quarter The laboratory report (MAI Lab ID No 48341),QA/QC reports and chain-of-custody ' forms are included in Appendix D ' 4 0. DISCUSSION/CONCLUSIONS Based on the analytical results from this investigation, AGE concludes the following • The relative ground water elevation at the site decreased 1 42 feet over the last quarter The ' map of ground water contours mdicates a divergent ground water flow direction toward the east • Ground water levels in monitoring wells MW-1, MW-2, MW-3 and MW-4 were ' approximately three to four`feet above the top of the screened interval, potentially reducing A the effectiveness of these ground water monitoring wells to characterize the dissolved-phase hydrocarbon plume in the shallowest groundwater • TPH-g'was detected this quarter in MW-1, MW-3, MW-4,_MW-5, VE-1 and VE-6 In general, the TPH-g concentrations have remained fairly stable when compared to the results from.the July 2000 sampling event, with concentrations decreasing slightly in MW-3, VE-1 < ' and VE-6 and increasing slightly In MW-1 A significant decrease of TPH-g concentrations dad occur in sample MW-4, with concentrations dropping from 3,900 µg11 in July 2000,to 480 µg11 during this quarter BTEX compounds show similar trends in these wells • Fuel oxygenates, including MTBE, DIPE or TBA, were detected in samples MW-1, MW-3, MW-5, VE-1 and VE-6 The highest oxygenate concentration detected was 69 µg/l of TBA ' ^ in sample MW-1 • An overall reduction of the dissolved-phase hydrocarbon plume concentrations on the site ' I has occurred since ground water monitoring began in 1994 However, the dissolved hydrocarbon concentrations, and specifically benzene, have fluctuated over the past four quarters The detection of petroleum hydrocarbons in monitoring wells MW-4 and MW-5' ' indicates that the hydrocarbon plume has not been delineated to the west, south and southeast i i Advanced GeoEoviromuental,Inc ` I I