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Y ' • 10 December 1998 I AGE-NC Project No 95-0111 Page 3 of 4 ' concentrations of 120 micrograms per liter (µg11), 64 µg/l and 290 µg/l, respectively These concentrations are at the middle to low end of the range of TPH-g concentrations previously detected ' in ground water samples collected from these`wells The sample collected'from monitoring well MW-2 did not contain a detectable concentration of TPH-g this quarter, but has sporadically during previous monitoring events TPH-d was detected in samples from wells MW-4 and MW-5 at concentrations of 34,000 µg/l and 63,000 µg11, respectively These concentrations are at the high end of the range of TPH-d ' concentrations detected in ground water samples collected from these wells during previous ground water monitoring events Laboratory notations for the ground water sample collected from wells MW-4 and MW-5 indicated the presence of an immiscible sheen 1 Benzene was detected in samples collected from wells MW-1, MW-2, MW-3, MW-4, MW-5 and MW-6 at concentrations of 32 µg11, 1 3 ag/l, 2 7 µg/l, 3 0µg11, 1 1 µg/1 and 3 3µg11, respectively ' Ethylbenzene was detected in MW-1, MW-2 and MW-3 at concentrations as high as 3 2 µg/l Xylenes were detected in samples from MW-1, MW-2 and MW-4 at concentrations as high as 4 7 µgr MTBE was detected by EPA Method 8260m m samples collected from wells MW-1, MW-2, MW- 4, MW-5 and MW-6 at concentrations of 1,500 µgll, 3 0 ug/l, 79 µg11, 57 µg11 and 1 8 ug/l, respectively ' Analytical results of ground water samples are summarized in Table 2 and Table 3 The laboratory report(MAI Laboratory No 96075 to 96080),quality assurance and quality control report and chain- of-custody are included in Appendix B ' 4.0. SUMMARY AND CONCLUSIONS 3 Based upon data collected from the site during the current and preceding ground water monitoring ' events, AGE concludes • During the September 1998 monitoring event,the inferred ground water flow direction at the ' site was generally toward the northeast, consistent with the inferred ground water flow direction determined from the 10 previous ground water monitoring events The gradient was approximately 0 005 ft/ft or 26 feet per mile ' • In general, the concentrations of TPH-g and BTEX detected in the ground water samples are at or near the low end of the range of concentrations previously detected, indicating that the 1 Advanced GeoEnvzronmental Inc 1