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1 ' 19 January 2004 i AGE-NC Project No 95-0173 ' Page 8of10 ' • Ground water flow direction was Inferred to be east-northeast, at an approximate hydraulic gradient of 0 006 ft/ft Due to the generally low gradient at the site, slight variations in ground water measurements or changes ofrecharge/discharge of the local ground water could greatly modify ground water flow direction 0 Ground water elevation at the site decreased approximately 2 73 feet between the July and October 2004 ground water monitoring events, since March 2004, ground water elevations have steadily decreased approximately 4-5 feet • Ground water at the site was significantly above the screened intervals of wells AW-1 (A and ' B), AW-2 (A and B), and MW-13 (A-C), and slightly above the screened intervals of wells MW-1 and MW-2 The ground water elevation appeared to be within or near the screened Intervals of all other wells at the site and should be representative of shallow ground water ' conditions • Ground water elevation data collected on 06 October 2004 Implies that ground water ' mounding did not occur at the site due to the on-going IAS activities • The elevated concentrations of petroleum hydrocarbons detected in samples collected from wells MW-2 (screened 30 feet to 50 feet), MW-4 (screened 30 feet to 50 feet), and AW-2A ' (screened 40 feet to 45 feet) indicate that these wells are within the remaining dissolved petroleum hydrocarbon "core area" of the plume (Figure 4) ' • The rapid decrease in dissolved petroleum hydrocarbon concentrations at AW-1 (A and B) can be attributed to the ongoing air sparging activities at well AW-I B during July through September 2004 However, previous analytical ground water data has indicated this concentration reduction may later rebound • The rapid,upward movement of volatilized hydrocarbons at AW-1B was substantiated with ' the observed `spike' in the August and September influent air flow samples • Generally, an overall apparent trend of decreasing dissolved petroleum hydrocarbon ' concentrations is evident in water samples collected from wells MW-3, MW-4, MW-6, AW-1 (A and B), and AW-2B, the trend of decreasing concentrations may be attributed to the air sparge activities being performed at well AW-1B (Table 3) • A moderate increase in dissolved hydrocarbons was observed in wells MW-I and AW-2A, the increase In hydrocarbon concentrations may be attributed to a `rebound' effect from the second quarter 2004 IAS activities previously conducted from well AW-2B • A significant increase is dissolved hydrocarbons was observed at well MW-2,the significant increase is representative of a southward shift of the ground water plume probably caused by reconfiguration of air sparging from well AW-2B (60-70 feet) to AW-1B (50-60 feet) i ' Advanced GeoEnvironmental,Inc I