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1 ' 16 September 2003 AGE-NC Project No 96-0229 Page 4 of 5 ' • Ground water flow direction at the site was inferred to be towards the northeast at an approximate gradient of 0 004 ft/ft This appears to be the prevailing flow direction for the area(Figure 3) ' • Due to the low hydraulic gradient at the site, slight variations in ground water recharge/discharge could greatly modify the inferred ground water flow direction ' • The elevated concentrations of petroleum hydrocarbons detected in samples collected from wells MWA, 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) • TPH-g,BTEX and MTBE were reported for the eighth consecutive quarter in water samples collected from MW-9, suggesting that the plume of petroleum-impacted ground water may ' have shifted towards MW-9 (Table 3) • The highest concentrations of on-site dissolved MTBE were detected from deeper screened well MW-1 (screened 48 to 53 feet bsg), lesser on-site MTBE concentrations were detected from shallow screened wells MW-2 (screened between 25 and 45 feet bsg) and MW-3 (screened between 291/Z and 49%2 feet bsg(Figure 5) ' • • The highest concentrations of off-site dissolved MTBE were detected northeast of the site from well MW-6(screened 25 to 45 feet bsg),additional off-site MTBE concentrations were observed at wells MW-9 (screened 20 to 40 feet bsg) and from well MW-IOB (screened 50 ' to 55 feet bsg) C Due to the significant MTBE concentrations detected near the UST tank pit area from well I MW-1 and from down-gradient well MW-10B, the dissolved MTBE plume is vertically undelineated on-site and down-gradient from the site (Figure 5) • Between March 2001 and August 2002, significant increasing MTBE concentrations were Iobserved from MW-IOA (screened 23 to 43 feet bsg), however, between August 2002 and June 2003 (three consecutive quarterly monitoring events), significant decreasing MTBE concentrations have been observed from MW-1 OA (Table 3) • Since monitoring wells MW-1 and MW-IOB are "drowned", these wells should yield samples representative of deeper ground water conditions Deeper ground water in the area of MW-1 (48 to 53 feet bsg) is impacted by significant TPH-g,BTEX, 1,2-DCA, DIPE and MTBE,deeper ground water in the area of downgradient well MW-I OB is impacted by TPH- g and MTBE • Significant 1,2-DCA was detected in the sample collected from well MW-1 (screened 48 to 53 feet bsg), which implies that dissolved 1,2-DCA is vertically undelineated at the site i Advanced GeoEnvironmental,Inc