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26 March 2001 . AGE-NC Project No 95-0130 Page 4 of 5 a ground water flow direction generally toward the northeast at a gradient of 0 005 fl/ft Due ' to the low hydraulic 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 • The ground water elevation at the site was only withm the screened interval of well VW-1B and is representative of shallow ground water conditions, monitoring wells MW-1 through MW-5, VW-1C, VW-2A and VW-3A are "drowned" with water 4 feet to 21 feet over the screens, and yield samples representative of deeper ground water conditions (Figures 6 and 7) tThe decrease of ground water elevation of approximately 2 22 feet between the June 2000 and October 2000 monitoring events is probably due to seasonal fluctuation ' Based on ground water levels measured at approximately 39 feet bsg, the dissolved TPH-g, BTEX and MTBE plume is at least 41 feet thick in the area of MW-3, MW-4, MW-5, VW-1B,VW-1C, VW-2A and VW-3A (screened intervals between 28 and 80 feet bsg) The estimated extent of dissolved hydrocarbon-Impact is depicted in cross sectional views C-C' and D-D' ' . 1,2-DCA-Impact was detected at wells MW-2 and MW-3 (screened 60 to 80 feet bsg), VW-1B (screened 48 to 63 feet bsg) and wells VW-1C, VW-2A and VW-3A (screened 43 to 63 feet bsg) Implying the 1,2-DCA plume Is at least 41 feet thick in the area of wells MW-2, MW-3, VW-1, VW-2 and VW-3 • The only detection of off-site dissolved TBA was in samples collected from crossgradient wells MW-5 at a concentration of 100 µg/1 Based on data collected from the Intervening well VW-1, the TBA-impact detected in well MW-5 may not be related to the Top Filling Station • The elevated concentrations of petroleum hydrocarbons detected in samples collected from wells VW-1, VW-2 and VW-3 indicate that these wells are within or near the dissolved petroleum hydrocarbon"core area" of the plume (Figures 4, 5, 6 and 7) • The lateral extent of the dissolved petroleum hydrocarbon plume is not known toward the north, northeast and east of the area bound by wells MW-1 through MW-5, VW-1, VW-2 and VW-3, the vertical extent is not known (Figures 4, 5, 6 and 7) • The greatest concentrations of dissolved TPH-g and BTEX were detected in samples collected from wells VW-1 and VW-2 located near the northern-most former UST pit(Figure 4), the greatest concentrations of dissolved MTBE were detected in samples collected from well VW-3 located near the southern-most former UST pit (Figure 5)which suggests at least two separate releases IAdvanced GcoEnvironmental,Inc I