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b 1 ' 06 April 2005 . AGE-NC Project No 98-0448 ' Page 7 of 9 Between 23 September and 22 December2004,the SVE unit operated for approximately 2,160 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 imass 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 131 pounds, or equivalent to an approximate volume of 21 gallons of gasoline extracted A plot of cumulative volume (gallons)of hydrocarbons extracted to date is in Appendix E Added to the estimated 281 41 gallons of hydrocarbons extracted from the ' SVE system since 16 April 2001,the total volume of hydrocarbons extracted to date is estimated at 302 42`gallons The mass/volume calculations for extracted hydrocarbons are included with Appendix F y i 5.0. DISCUSSION AND CONCLUSIONS i The implications from the December 2004 round water monitoring events are as follows p g g • The December 2004 ground water elevations at the site ranged between 1123 feet(MW-3) and 14 18 feet(MW-4B)below MSL The ground water elevation at the site was within the screened intervals of wells MW-1 through MW-8 should be representative of shallow ground water conditions,however well MW-4B is"drowned"with water approximately 22 feet over the screen and yields a sample more representative of deeper ground water conditions (Table 2) • Ground water elevation data collected on 07 December 2004 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 0 010 ft/ft (Figure 3) ' The December 2004 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 wells MW-1 through MW-8 and suggests the margins of the plume are within the perimeter of the well network ' Generally, an overall apparent trend of decreasing dissolved petroleum concentrations is evident in water samples collected from wells MW-1, MW-2, MW-4A and MW-4B, the trend of decreasing concentrations may be attributed to the air sparge activities being ' performed at wells AW-1 through AW-5 and MW-4B (Table 3) ' Advanced GeoEnvironmental,Inc r