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V 1 19 June 2000 AGE-NC Project No 96-0232 Page 15 of 35 water flow direction and gradient on the site Laboratory analysis of water samples from these wells indicated that ground water at the site locally has been significantly impacted by MTBE Laboratory analysis of the grab samples detected less significant concentrations of dissolved TPH-g, TPH-d, BTEX compounds, TAME, ETBE, TBA, methanol, ethanol and 1,2-DCA during the site investigation (Table 5) Substantial concentrations of ethanol were detected in the initial ground water samples collected from multi-level morutonngwells MW-8,MW-9,MW-10,MW-11,MW-12 and MW-13 However,AGE believes the substantial ethanol concentrations detected were a result of ethanol and ethanol acetate in the time-release coating on the bentonite pellets that dissolved in ground water (see Section 3 - bullet 17, Appendix D and Appendix E) The highest dissolved MTBE concentration detected in ground water monitoring well samples was detected in the sample collected from monitoring well MW-1 at a concentration of 5,500 gg/l, low and minor concentrations of dissolved MTBE were detected in shallow ground water samples from monitoring wells MW-2, MW-4, MW-5, MW-6A, MW-7, MW-12A and MW-13A, low concentrations of dissolved MTBE were detected in samples from deeper ground water monitoring wells MW-613 (43 to 48 feet), MW-9A (40 to 50 feet), MW-11B (65 to 75 feet), MWA 1D (130 to 150 feet)and MW-13B(50 to 60 feet) The inferred horizontal extent of dissolved MTBE in shallow ground water (5 to 30 feet) is depicted in Figure 36, the inferred horizontal extent of dissolved MTBE encountered in deeper groundwater monitoring wells(40 to 75 feet)is depicted in Figure 37 At depths deeper than 75 feet,dissolved MTBE was detected in samples collected between 130 feet and 150 feet bsg only in MW11D, and has been detected at concentrations as high as 10 µg/I The highest dissolved TPH-d concentrations detected in monitoring well samples were collected from the Three B's Truck Plaza shallow groundwater monitoring wells MW-1 and MW-3,in which TPH-d has been detected at concentrations of 2,300 µg/1 and 1,200 µg/l, respectively, low to moderate concentrations of dissolved TPH-d have been detected in samples from Three B's shallow wells MW-2, MW-5,MW-6 and from Flag City Chevron shallow wells MW-12A and MW-13A at concentrations between 74 and 480µg/1 Low concentrations of dissolved TPH-d have been detected in samples from Flag City Chevron deeper ground water monitoring wells MW-9A(40 to 50 feet), MW-1 IB (65 to 75 feet) and MW-13B (50 to 60 feet) The estimated extent of dissolved TPH-d for shallow ground water monitoring wells (5 to 30 feet) is depicted in Figure 39, the estimated extent of dissolved TPH-d for deeper ground water monitoring wells (40 to 75 feet) is depicted in Figure 40 TPH-d has also been detected in the deepest ground water zone sampled (130 feet to 150 feet bsg) in MW11-D, at a concentration of 580 µg/1, but was below the method detection limit in the subsequent sample The highest concentrations of dissolved TPH-g detected in monitoring well samples were collected from Three B's Truck Plaza shallow ground water monitoring wells MW-3 and MW-6 at concentrations of 26,000 µg/l and 14,000 µg11, respectively Low to moderate concentrations of dissolved TPH-g were detected in samples from Three B's shallow wells MW-2,MW-3,MW-5 and Advanced GeoEn%ironmental,Inc