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15 February 1999 AGE-NC Project No 96-0229 Page 7 of 9 MW-6, MW-7, MW-8, MW-10A and MW-1013 at concentrations ranging between 160 ,ug/l (micrograms per liter) and 110,000 µg/l Laboratory data indicates that the greatest concentrations of dissolved TPH-g are located near wells MW-1, MW-2, MW-3 and MW-6 (Figure 12) BTEX compounds were detected in ground water samples collected from wells MW-1 through MW- 4,MW-6,MW-7,MW-l0A and MW-1 OB at concentrations ranging as high as 17,000µg/1 (toluene, MW-6) The greatest benzene concentrations were detected in samples collected from wells MW-1 and MW-6 at concentrations between 5,500 µg/1 and 5,700 µg/l MTBE was detected from wells MW-1, MW-4, MW-6, MW-7, MW-8, MW-1 OA and MW-10B at concentrations ranging as high 860 ppb (MW-1) TAME was detected from MW-4 and MW-8 at concentrations of 12 µg/1 and 2 9 µg/l,respectively TBA was detected at MW-7 at a concentration of 40 µg/l, no other fuel oxygenates were detected above laboratory reporting limits The analytical results of quarterly ground water samples are summarized in Table 3 The laboratory reports (Castle Analytical Laboratory Reference No 1808 and McCampbell Analytical Inc Lab I D No 97364 through 97397371) and chain-of-custody forms are included in Appendix E 4.0 SUMMARY AND CONCLUSIONS ' Based on the results of ground water monitoring and sampling activities performed in October 1998, AGE concludes I a TPH-g and BTEX were not detected in selected soil samples collected from soil borings/monitoring wells MW-7, MW-8, MW-9 or MW-10 MTBE was detected at a concentration of 0 0053 mg/kg in the 40-foot bsg soil sample collected from MW-8 • The estimated extent of petroleum hydrocarbon-Impacted soil is illustrated in cross sectional view in Figures 13, 14, 15 and 16 • The site gradient was calculated at 0 004 ft/ft, or approximately 21 feet per mile(Figure 10) • Ground water flow direction at the site (the area containing wells MW-1 through MW-10) was estimated to be toward the northeast(Figure 10) • Due to Increasing ground water elevations at the site, the ground water surface elevation]at the site is above the slotted screened intervals in wells MW-1, MW-3, MW-4 and MW-10 Therefore, samples collected from these wells may not be representative of dissolved petroleum hydrocarbon concentrations in shallow ground water C TBA was detected for the first time in a water sample collected from well MW-7 • TAME was detected for the first time in water samples collected from MW-4 and MW-8 Advanced GeoEmiron mental,Inc E