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19 April 1999 AGE-NC Project No 96-0229 Page 4 of 5 to the low gradient at the site, slight variations in ground water measurements or changes of ' recharge/discharge of the local ground water could greatly modify ground water flow direction • Ground water elevation at the site increased an average 3 68 feet between the January 1999 and the April 1999 ground water monitoring events • Ground water was approximately 5 to 7 feet above the screened intervals in monitoring wells MW-3 and MW-4, ground water was approximately 24 to 26 feet above the screen intervals at MW-1 and MW 10-13 Therefore these wells are "drowned", and do not yield samples representative of shallow ground water • TPH-g was detected in water samples collected from wells MW-1 through MW-4, MW-6, MW-7, MW-8 and MW-9 at concentrations ranging up to 88,000 µg11 • MTBE was detected utilizing EPA Method 8020 in ground water sazmples collected from wells MW-1, MW-7 and MW-8 at concentrations ranging as high as 350 µg/l, MTBE was confirmed utilizing EPA Method 8260 in the samples collected from wells MW-1, MW-6, MW-7 and MW-8 at concentrations ranging as high as 310µg11 • TAME was detected in ground water samples collected fiom well MW-7 at a coneentiatlon of 1 2 µg/l • TBA was detected from ground water samples collected fiom wells MW-7 and MW-9 at concentrations ranging as high as 36 µg/l • The highest MTBE concentration was encountered in the ground water sample from the deeply di owned MW-1, but was not detected in the properly screened "clustered" well MW- 2 • BTEX compounds were detected to ground water samples collected from wells MW-1 through MW-8 and MW--1013 at concentrations ranging as high as 12,000 µg/l The greatest benzene concentration was detected fiom well MW-1 (screened from 48 to 53 feet bsg) at a concentration of 2,800 ,ug/1 • From October 1998 to January 1999, a general decrease in dissolved petroleum hydrocarbon concentrations was observed in samples collected fiom wells MW-i, MW-2, MW-3, MW-6 and MW-7 (Table 2) Conveisely, general increases were observed in samples collected fiom wells MW-4, MW-5 and MW-1 OB rhe increases/decreases could be related to a slight northwest shift in the dissolved petroleum hydrocarbon plume • The elevated concentrations of petroleum hydrocarbons detected in samples collected fiom wells MW-1, MW-2, MW-3 and MW-6 indicate that these wells are within or neat the dissolved petroleum hydiocaibon "core area" of the plume (Figure 4) Adivnud CLuEn11[onment el,Inc