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08 July 2003 <br /> AGE-NC Project No 96-0229 <br /> Page 4 of 5 <br />' 4.0. SUMMARY AND CONCLUSIONS <br /> The implications from the findings of the February 2003 ground water monitoring event are <br />' - Ground water flow direction at the site was Inferred to be towards the northeast at an <br /> approximate gradient of 0 004 ft/ft This appears to be the prevailing flow direction for the <br /> Iarea(Figure 3) <br /> - Due to the low hydraulic gradient at the site, slight variations in ground water <br /> I recharge/discharge could greatly modify the Inferred ground water flow direction <br /> The elevated concentrations of petroleum hydrocarbons detected in samples collected from <br /> wells MW-1, MW-2, MW-3 and MW-6 Indicate that these wells are within or near the <br /> dissolved petroleum hydrocarbon "core area" of the plume (Figure 4) <br /> TPH-g, BTEX and MTBE were reported for the seventh consecutive quarter in water <br /> samples collected from MW-9, suggesting that the plume of petroleum-Impacted ground <br /> water may have shifted towards MW-9 (Table 3) <br /> - The highest concentrations of off-site dissolved MTBE were detected in down-gradient well <br /> MW-6, elevated off-site MTBE concentrations has generally been observed at MW-6 since <br /> March 2001 (Figure 5) <br /> - Generally,increasing MTBE concentrations have been reported from MW-1 OA since at least <br /> March 2001, suggesting that the plume of MTBE-impacted ground water is migrating <br /> towards the northeast and beyond well MW-10A (Table 3) <br /> - Since monitoring wells MW-1 and MW-10B are "drowned", these wells should yield <br /> samples representative of deeper ground water conditions Deeper ground water in the area <br /> I of MW-1 (48 to 53 feet bsg)is impacted by significant TPH-g,BTEX, 1,2-DCA and MTBE, <br /> deeper ground water in the area of downgradient well MW-IOB is impacted by MTBE <br /> I - Significant MTBE concentrations were detected near the UST tank pit area In the sample <br /> collected from well MW-1 (screened 48 to 53 feet bsg)and In the sample collected from the <br /> down-gradient well MW-10B (screened 50 to 55 feet bsg), implying that dissolved MTBE <br /> is vertically undelineated on-site and down-gradient from the site (Figure 5) <br /> Significant 1,2-DCA was detected In the sample collected from well MW-1 (screened 48 to <br /> 53 feet bsg), which implies that dissolved 1,2-DCA is vertically undelmeated at the site, <br /> additionally, a low concentration of 1,2-DCA was detected from well MW-11 which could <br /> Imply an undelineated 1,2-DCA plume north of the site <br /> • <br /> Advanced GeoEnvironmental,Inc <br /> I <br />