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18 February 2003 <br /> I AGE-NC Project No 98-0448 <br /> Page 4of8 <br /> I4 0. FINDINGS <br /> AGE determined ground water flow direction and gradient from the field data collected on <br /> I03 December 2002, the contaminant impact to ground water was assessed from the laboratory data <br /> From field data collected at the SVE remediation system between II September 2002 and <br /> 17 December 2002,AGE determined the average TPH-g concentration and the average flow rate and <br /> calculated the approximate mass and volume of hydrocarbons removed <br /> 4 1 GROUND WATER ELEVATION AND GRADIENT <br /> The depths to ground water were measured at between 19 52 and 22 38 feet below the tops of the <br /> wcll casings (Table 2) Ground water elevations at the site were calculated to be between 10 68 feet <br /> (MW-7) and 12 97 feet (MW-4B) below mean sea level (Table 2), ground water elevations are <br /> depicted in Figure 3 Ground water elevation at the site decreased an average 1 06 feet between the <br /> August 2002 and the December 2002 ground water monitoring events <br /> • The ground water flow direction at the site was inferred to be southwest, at a gradient of <br /> approximately 0 01 fl/ft,or approximately 53 feet per mile Groundwater elevation recorded at wel l <br /> MW-4A was not utilized to contour ground water elevations at the site due to the possibility that the <br /> apparent formation of a sediment plug in the well at between 11 and 20 feet below surface grade <br /> (bsg) may have affected the depth to water measurement <br /> I <br /> 42 LABORATORY RESULTS OF GROUND WATER SAMPLES <br /> I TPH- was detected in water samples collected from wells MW-2 MW-4A and MW-4B at <br /> g P <br /> concentrations as high as 8,100 micrograms per liter Cag/1), the highest TPH-g concentration in first <br /> water was detected from MW-2 The laboratory reported that the sample chromatograms all <br /> contained significant unmodified or weakly modified gasoline The inferred extent of dissolved <br /> TPH-g is depicted in plan view in Figure 4 <br /> Various BTEX compounds were detected in water samples collected from MW-1, MW-2,MW-4A <br /> and MW-4B at concentrations as high as 2,000 pg/l xylene (MW-2), the maximum benzene <br /> concentration was detected in the sample collected from MW-4B at a concentration of 30µg/1 <br /> MTBE was detected by EPA Method 8260B in water samples collected from wells MW-4B and <br /> MW-8 at concentrations of 2 7#g/l and 4 3,ug/l,respectively, DIPE was detected in water samples <br /> Advanced GeoEnvironmental,Inc <br />