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. 24 August 2001 AGE-NC Project No 98-0448 ' Page 4of7 4 1 GROUND WATER ELEVATION AND GRADIENT ' The - r measured between depths to ground water in wells MW-1, MW-4A, MW-4B and MW-6 were ' 18 30 and 19 91 feet below the tops of the well casings Ground water elevations at the site were calculated to be between 8 78 feet and 10 50 feet below mean sea level, ground water elevations are depicted in Figure 3 Ground water elevation at the site increased an average 0 56 feet between the January 2001 and the April 2001 ground water monitoring events The general ground water gradient at the site was calculated to be approximately 0 015 ft/ft or less, ' or approximately 79 feet per mile, directed towards the south-southwest (Figure 3) 4 2 LABORATORY RESULTS OF GROUND WATER SAMPLES TPH-g was detected in water samples collected from wells MW-1, MW-2, MW-4A, MW-4B and MW-6 at concentrations as high as 69,000 micrograms per liter (,ug/l), however the laboratory reported the MW-1, MW-2, MW-4A and MW-4B samples with significant unmodified or weakly modified gasoline and the MW-6 sample with one to a few isolated peaks present in the sample chromatogram The inferred extent of dissolved TPH-g is depicted in plan view in Figure 4 Various BTEX compounds were detected in water samples collected from MW-i, MW-2, MW-4A, MW-4B and MW-6 at concentrations as high as 11,000 kzg1l, the greatest benzene concentration was detected in the sample collected from MW-4B at a concentration of 4,700 ,ug/1 None of the fuel oxygenated or lead scavenger compounds were detected by laboratory analysis Previous and current analytical results of ground water monitoring well samples are summarized in Tables 2 and 3 The laboratory reports (McCampbell Analytical Inc I D 66033 through 66037) and chain-of-custody forms are presented in Appendix C 43 RESULTS OF VAPOR EXTRACTION Between 16 April 2001 and 30 June 2001, the SVE and IAS remediation systems were operational for 1,704 hours(Table 5) During the operational period, SVE'inlet flow rates ranged from 28 to 50 cubic feet per minute(cfrn),differential pressures ranged between 0 25 and 0 85 inches of water, and induced vacuum between 50 and 72 inches of water Utilizing a photo ionization meter (PID), hydrocarbon concentrations were measured between 70 and 498 parts per million (ppm) at regular intervals at the SVE inlet, however a general concentration trend was not established from the PID field measurements Field measurements are summarized in Table 5 IAdvanced GeoEnvironmental,Inc I