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I I02 December 2002 • AGE-NC Project No 98-0534 Page 3 of 4 3 2 ANALYTICAL RESULTS OF GROUND WATER SAMPLES TPH-d was detected in the ground water samples collected from wells MW-4,MW-6 and MW-7 at concentrations of 140 micrograms per liter(µg/1)and 130 µg/1 and 60µg/1,respectively TPH-g and BTEX compounds were not detected in the ground water samples analyzed I MTBE was detected by EPA Method 8260 in the samples from wells MW-3,MW-4,MW-6,MW-7 and MW-8 at concentrations of 10 µg/1, 16 µg/1, 140 µg/l,0 77 µg/1 and 1 2 µg/1,respectively TBA was detected in sample MW-4 at 16 µg/1 No other fuel oxygenates were detected in the samples analyzed The current and historical ground water analytical results are summarized on Table 2 The laboratory Ireport (MAI laboratory ID No 0210068-1 to-7), chain-of-custody form and the laboratory QA/QC report are Included in Appendix B 4.0. SUMMARY AND CONCLUSIONS I • The implications from the October 2002 ground water monitoring event are as follows I • The water table was inferred to be relatively flat in the area of the former UST area, but formed a northwest-trending water-table depression north of the UST area • The ground water elevations at the site were within the screened intervals of the wells, which I should yield samples fully representative of shallow ground water conditions m • MTBE was detected n tle ground water frnples by EPA 8260,the MTBE concentrations in samples MW-4 (1.9µg/1) and MW-6 (Mµg/1)were above the DHS' primary Maximum Contaminant Level of 13 4g/1 in drinking water • MTBE in shallow ground water has generally been delineated to the north,east and west, low MTBE concentrations are still present in the southernmost well 5.0. RECOMMENDATIONS Based upon the results of the fourth quarter 2002 investigation, AGE recommends • Continued quarterly ground water monitoring utilizing wells MW-1 and MW-3 through IMW-8 for characterization of ground water conditions on the site The next ground water monitoring event is tentatively scheduled for January 2003 IAdvanced GeoEnviron mental,Inc I