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' 09 April 1999 AGE-NC Project No 96-0229 Page 4 of 5 ' direction Between the October 1998 and the January 1999 ground water monitoring events, ground water elevation at the site decreased an average 0 18 feet ' • Ground water was approximately 2 to 3 feet above the screened intervals in monitoring wells MW-3 and MW-4, ground water was approximately 20 to 22 feet above the screen Intervals ' at MW-1 and MW10-B, therefore, these wells are "drowned", and may not yield samples fully representative of ground water conditions near the top of the saturated zone, where fuel hydrocarbons would be expected to have the greatest Impact ' • TPH-g was detected in water samples collected from wells MW-1 through MW-3, MW-6, MW-7, and MW-8 at concentrations ranging as high as 120,000 µg11 ' a MTBE was detected from wells MW-1, MW-4, MW-5, MW-7 and MW-8 utilizing EPA Method 8020 at concentrations as high as 910 ,ug/l, MTBE was confirmed utilizing EPA Method 8260 from wells MW-1, MW-4, MW-6, MW-7 and MW-8 at concentrations ranging as high as 600 µg/l • The highest MTBE concentration was encountered in the ground water sample from the deeply drowned MW-1, but was not detected in the properly screened twin well MW-2 C BTEX compounds were detected in ground water samples collected from wells MW-1 through MW-4, MW-6 and MW-7 at concentrations ranging as high as 17,000 mg/l (toluene, MW-6) The greatest benzene concentration was detected from well MW-6 at a concentration of 5,700 Mcg/l The second highest benzene concentration was encountered in the deeply screened MW-1 at a concentration of 4,800 µg/l • From October 1998 to January 1999, a general decrease in dissolved petroleum hydrocarbon ' concentrations was observed from well MW-1, MW-10A and MW-10B (Table 2) Conversely, general increases were observed from wells MW-2, and MW-7 None of the Increases or decreases appears to be related to a significant trend ' • The elevated concentrations of petroleum hydrocarbons detected in samples collected from wells MW-1, MW-2, MW-3 and MW-6 Indicate that these wells are within or near the dissolved petroleum hydrocarbon"core area" of the plume (Figure 4) • The dissolved petroleum hydrocarbon plume appears to be sufficiently contained within the current array of ground water monitoring wells, however the Increased hydrocarbon concentrations reported in well MW-7 and decrease in concentrations from wells MW-i0A and MW-10B may indicate a shift of migration of the plume from northeastward to a slightly more northward direction Advanced GcoEnwonmcntal,Inc 1