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I A r l S Y ' ' 26 February 2004 `. AGE-NC Project No 98-0448 ' Page 8of10 gallons of gasoline extracted A plot of the cumulative volume(gallons) of hydrocarbons extracted ' to date is in Appendix G Added to the estimated 239 15 gallons of hydrocarbons extracted from the SVE system since 16 April 2001,the total volume of hydrocarbons extracted to date is estimated at ' 253 36 gallons The mass/volume calculations for extracted hydrocarbons are included with Appendix H ' b 0 DISCUSSION AND CONCLUSIONS The implications from the December 2003/January 2004 ground water monitoring events are as follows ' • December 2003 ground water elevations ranged between 8 99 feet (MW-7) and 12 05 feet (MW-4B) feet below MSL,January 2004 ground water elevations ranged between 9 95 feet (MW-7) and 11 81 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 23 feet over the screen and yields a sample more representative of deeper ground water conditions (Table 1) • Ground water elevation data collected during the 29 December 2003 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 December 2003 gradient was estimated to be approximately 0 017 ft/ft, the January 2004 gradient was estimated to be approximately 0 011 ft/ft (Figures 3 and 4) • The December 2003 and January 2004 concentrations of petroleum hydrocarbons detected ' in the sample collected from wells MW-2 and MW-4A indicate that these well is within the dissolved petroleum hydrocarbon"core area" of the plume(Figures 5 and 6) • Prior to December 2003, petroleum hydrocarbon and MTBE concentrations had decreased ' to below laboratory reporting limits in the samples collected from wells MW-4A (screened 8 to 33 feet bsg) and MW-4B (screened 45 to 50 feet bsg) However, at the conclusion of the I rebound test, a significant, increase (spike) of dissolved concentrations of TPH-g, ethylbenzene and xylenes were reported from both MW-4A and MW-4B • Between the December 2003 and the January2004 monitoring events,significant TPH-g and I BTEX increases were also observed from MW-2 1t is unclear if the increases were related to a rebound effect because the January 2004 increases observed at MW-2 were still within the normal fluctuation observed at MW-2 since initiation of the SVEAAS remediation system in April 2001 Advanced GeoEnvironmental,Inc I r