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I ' 31 August 2004 AGE-NC Project No 95-0173 ' Page 9 of 10 I December 2003 and January, February and March 2004 However, previous analytical ground water data has indicted this concentration reduction may later rebound • An over-all decreasing trend in hydrocarbon concentrations observed at well AW-1B may be attributed to the September, October and November 2003 1AS activities performed at AW-1B, furthermore, the rapid, upward movement of volatilized hydrocarbons was substantiated with the observed `spike' in the September, October and November 2003 ' influent air flow samples • Generally, an overall apparent trend of decreasing dissolved petroleum concentrations is evident in water samples collected from wells MW-1, MW-2, MW-3 and MW-6, the trend of decreasing concentrations may be attributed to the air sparge activities being performed at well AW-2B (Table 3) I • A moderate increase in dissolved hydrocarbons was observed from well AW-1 (A and B), the increase in hydrocarbon concentrations may be attributed to a `rebound' effect from the fourth quarter 2003 IAS activities previously conducted from well AW-1B • Previous and current laboratory results of ground water samples suggest that there is a minor MTBE- and 1,2-DCA-impact to ground water in the areas of wells MW-2 through MW-5, MW-9, MW-11, AW-1B and AW-2A (Tables 3 and 4) • AGE suspects that the MW-13C water re-sample collected on 09 April 2004 was more representative than that of the MW-13C sample collected on 19 March 2004, furthermore, AGE suspects that one of the unused multi-level chambers was inadvertently monitored and sampled instead of the MW-13C chamber During 19 March 2004,the well had been purged `dry' after only 1 gallon of water had been evacuated,however,MW-13C had previously had very little ground water draw-down during the five previous ground water monitoring events Additionally,the March 2004 concentration of 2,900µg/1 was well above the previous range of TPH-g concentrations between non-detect (less than 50 µg/l) and 270 gg/l Based on SVE remediation data collected between 30 December 2003 and 24 March 2004, AGE concludes • The average SVE inlet vapor concentration was approximately 340 µg/1, the average SVE inlet flow rate was approximately 71 cubic feet per minute (Table 6) • The volume of hydrocarbons extracted by the SVE system was calculated to be approximately 30 gallons of petroleum hydrocarbons (Appendix F) during the first quarter 2004 monitoring periods (Table 7) • Since-initiation of the SVE system,the total volume of petroleum hydrocarbons extracted is _I estimated to be approximately 1,929 gallons (Table 7) Advanced GeoEnvi ron mental,Inc