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4 i t , ` Y I 15 December'2003 AGE-NCP o - Project N 9$ 0448 _ Page 7 of 9 , ' Between 23 June 2003 and 09 October 2003, the SVE unit continuously operated approximately' 2,592 hours The average of analytical results between SVE air flow sampling events (Table 5), average SVE air flow rates, (Table 6) and the operational period were used to calculate the ' approximate volume and mass of extracted gasoline during these penods During the above air monitoring events, the mass of hydrocarbons extracted from the SVE system was calculated to be approximately 22 10 pounds, or equivalent to an approximate volume of 3 53 gallons of gasoline extracted A plot of the cumulative volume (gallons) of hydrocarbons extracted to date is in Appendix E Added to the estimated 235 61�gallons of hydrocarbons extracted from the SVE system since 16 April 2001, the total volume of hydrocarbons extracted to date is estimated at 239 15 gallons The mass/volume calculations for extracted hydrocarbons are included with Appendix F u' 5.0. DISCUSSION AND CONCLUSIONS i The implications from the June 2003 ground water monitoring event are as follows . • Ground water elevations ranged between 9 90 feet(MW-4A) and 13 16 feet(MW-4B) feet 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 I , • Ground water elevation data collected on 18 September 2003 is not,conclusive to suggest ground water mounding is occurring due to air sparging at the site • Ground water flow direction at the site was toward the southwest,the gradient was estimated to be approximately 0 011 ft/ft ' •' The concentrations of petroleum hydrocarbons detected in the sample collected from well MW-2 indicates that this well is within the dissolved petroleum hydrocarbon"core area"of the plume (Figure 4) • Petroleum hydrocarbon and MTBE concentrations have decreased to below laboratory reporting limits in the sample collected from well MW-4B(screened 45 to 50 feet bsg) This is the second time in the past three sampling events that TPH-g has not been detected and the first time in the past five sampling events that MTBE has not been detected An 'over-all trend of decreasing concentrations from MW-4B is evident for ten consecutive quarters Between the June 2003 and the September 2003 ground water monitoring events, a Isignificant decrease was observed in the dissolved TPH-g/BTEX concentrations at well IAdvanced GeoEnvironmental,Inc r i