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29 May 2000 <br /> AGE-NC Project No 99-0624 <br /> Page 3 of 4 <br /> approximately S 4° E with a gradient of 0 002 ft/ft Figure 3 depicts the ground water elevation <br />' contours for 16 November 1999 <br />' 3 2 LABORATORY RESULTS OF GROUND WATER SAMPLES <br /> Petroleum hydrocarbons quantified as TPH-g were detected in ground water samples collected from <br /> all four monitoring wells MTBE was detected in ground water samples collected from monitoring <br /> wells MW-2 and MW-3 <br /> TPH-g was detected at concentrations as high as 1,800 micrograms per liter (µg/1) in samples <br /> collected from MW-2 and MW-3 Xylene and benzene compounds were detected at concentrations <br /> as high as 130 gg/1 and 190 µg/1 from MW-3, and 110 µg/1 and 62 µg/1 from MW-2, respectively <br /> MTBE was detected in monitoring wells MW-2 and MW-3 at concentrations of 130µg/1 and 4 1 g/l, <br /> respectively <br /> Analytical results of the ground water samples for the fourth quarter - 1999 monitoring event are <br /> summarized on Table 2 The laboratory report (MAI Laboratory ID 25687-25690), QA/QC and <br /> chain-of-custody are included in Appendix B <br /> 4 0 SUMMARY/CONCLUSIONS <br /> The following conclusions were drawn from the results of the site investigation <br /> • The average ground water elevation on 16 November 1999 from monrtonng wells on-site <br /> was approximately 50 feet below surface grade <br /> • The inferred ground water gradient on 16 November 1999 was calculated to be 0 002 ft/ft <br /> toward the south <br /> • TPH-g was detected in ground water samples from all four monitoring wells on-site with the <br /> highest concentrations from samples collected from MW-2 and MW-3 The data suggests <br /> that the UST system, possibly the former dispenser island, was the area of the petroleum <br /> hydrocarbon release The data also suggests that the TPH-g impact to ground water extends <br /> laterally to the north and west as far as MW-4 and MW-1, respectively <br /> • BTEX compounds were detected In the water samples collected from all four monitoring <br /> wells, the MW-3 and MW-2 samples had the highest concentrations <br /> • Utilizing EPA Method 8260M, MTBE was detected at concentrations of 130 µg/1 and <br /> Advanced GeoEnviron mental,Inc <br />