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' 24 May 2005 AGE-NC Project No 98-0448 ' Page 7 of 9 ' Between 22 December2004 and 08 March 2005, the SVE unit operated for approximately 1,824 hours The average of analytical results between SVE air flow sampling events (Table 6), average SVE air flow rates, (Table 7) and the operational period were used to calculate the approximate volume and mass of extracted gasoline during these periods During the above air monitoring events, ' the mass of hydrocarbons extracted from the SVE system was calculated to be approximately 53 pounds, or equivalent to an approximate volume of 8'/2 gallons'of gasoline extracted A plot of ' the cumulative volume (gallons)of hydrocarbons extracted to date is in Appendix E Added to the estimated 302 42 gallons of hydrocarbons extracted from the SVE system since 16 April 2001, the total volume of hydrocarbons extracted to date is estimated at 310 93 gallons The mass/volume ' calculations for extracted hydrocarbons are included with Appendix F ' 5.0. DISCUSSION AND CONCLUSIONS The implications from the March 2005 ground water monitoring events are as follows ' • The March 2005 ground water elevations at the site ranged approximately between 8 85 feet '. (MW-4A)and 10 84 feet(MW-4B)below MSL The ground water elevation at the site were slightly above the screen intervals at wells MW-1, MW-2 and were within the screened intervals of wells MW-3 through MW-8, and should be representative of shallow ground ' water conditions,however well MW-4B is"drowned"with water approximately 25 feet over the screen and yields a sample more representative of deeper ground water conditions (Table 2) ' • Ground water elevation data collected on 24 March 2005 did not suggest that ground water mounding was occurring due to air sparging at the site (Figure 3) ' • Ground water flow direction at the site was toward the southwest,the ground water gradient was estimated to be approximately 0 050 ft/ft (Figure 3) ' • The March 2005 concentrations of petroleum hydrocarbons detected in the sample collected from well MW-2 indicates that this well is still within the dissolved petroleum hydrocarbon "core,area"- of the plume (Figure 4), no other-petroleum hydrocarbons were detected from Y . . ' wells MW-1 through MW-8 and suggests the margins of the plume are within the perimeter of the well network • Between the December 2004 and March 2005 monitoring events, increasing TPH-g ' concentrations were reported from samples collected at well MW-2(from 1,300µg/1 to 6,400 µg/1), the elevated TPH-g concentrations may be attributed to increasing ground water elevations ,Conversely,benzene levels were not detected from MW-2 for the 7'consecutive ' monitoring event, with a trend of decreasing toluene and total xylenes levels still evident from MW-2 samples The trend of decreasing concentrations may be attributed to the air ' Advanced GeoEnrironmental,Inc I '