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1 ' 29 January 2004 AGE-NC Project No 96-0263 Page 3 of 4 3 2 ANALYTICAL RESULTS OF GROUND WATER SAMPLES ' TPH-g was detected in water samples MW-2, MW-4, MW-5 and MW-7 at concentrations ranging from 260 micrograms per liter(µg/1) in MW-4 to 24,000 µg/1 in MW-7 IBenzene was detected in water samples MW-2 and MW-7 at concentrations of 6 4µg/1 and 320 µg/l, respectively Toluene was detected in sample MW-7 at a concentration of 27µg/1 Ethylbenzene was ' detected in samples MW-2 and MW-7 at concentrations of 8 1 µg/1 and 70µg/1, respectively Total xylenes were detected in samples MW-2, MW-4, MW-5, MW-7 and MW-8 at concentrations ranging from 3 0 µg/1 (MW-4) to 65 µg/l (MW-7) ' MTBE was detected in samples MW-2, MW-4 MW-5 and MW-7 at concentrations ranging from p � g g 230 µg/l(MW-4)to 33,000 µg/1 (MW-7) TAME was detected in sample MW-7 at a concentration ' of 35 µg/1 No other fuel additives were detected in the ground water samples collected from the site ' The current and past ground water sample analytical results are summarized on Tables 2 and 3 Copies of the laboratory report(CTEL Laboratory IDs 0312-119-1 through 0312-119-11), QAIQC report and chain-of-custody form are in Appendix B 4.0. SUMMARY AND CONCLUSIONS Based on the results of this investigation, AGE concludes that I • Depth to ground water ranged from 7 07 feet to 8 25 feet below the tops of the well casings Ground water elevations at the site ranged from 28 65 feet above mean sea level (MSL) in well MW9 to 29 48 feet above MSL in well MW1I The ground water at the site was inferred to be flowing to the northwest at an average gradient of 0 005 feet/feet • Target analytes, including TPH-g, BTEX compounds, MTBE and/or TAME were detected in ground water samples collected from wells MW-2, MW-4, MW-5, MW-7 and MW-8 Detected concentrations of target analytes were generally consistent with previous results from ground water analyses The current concentrations of benzene to TPH-g, when compared, for a ratio of approximately 1 3 %, which indicates a natural attenuation of the dissolved benzene at the site However,the MTBE concentrations have remained stable over the monitoring period,therefore,no evidence of natural attenuation for the dissolved MTBE can be documented • The dissolved hydrocarbon plume extends northward from the former UST and dispenser areas, but not beyond the down-gradient monitoring wells (MW8, MW9 and MW10) The dissolved phase plume has been defined laterally in all directions Isoconcentration maps illustrating the approximate extent of TPH-g, benzene and MTBE-impacted ground water I are depicted on Figures 4, 5 and 6 Advanced GeoEnvironmental,Inc I