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• 10 January 2001 <br /> AGE-NC Project No 96-0263 <br /> Page 3 of 4 <br /> Benzene was detected in the water samples collected from all of the monitoring wells with the <br /> exception of MW-1 and MW-3 Benzene concentrations ranged from 5 1 µg/l in MW-6 to 5,000µg/1 <br /> in MW-7 Toluene, ethylbenzene and xylenes were also detected in all the wells, with the exception <br /> of MW-1 and ethylbenzene in MW-3 at concentrations ranging from 0 58 ,ug/l of xylene in MW-3 <br /> to 1,600,ug/l of xylene in MW-7 <br /> IMTBE was detected by EPA method 8020 in monitoring wells MW-2, MW-4, MW-5, MW-7 and <br /> MW-8 at concentrations ranging from 46 µg11 in MW-8 to 120,000 µg/1 in MW-7 MTBE was <br /> confirmed by EPA method 8260m and was detected in wells MW-2, MW-4 through MW-8 at <br /> concentrations ranging from 5 2 µg/1 in MW-6 to 130,000µg/1 in MW-7 TBA was detected in the <br /> ground water sample collected from MW-5 at a concentration of 350 1,ig/1 No other oxygenates were <br /> detected in the ground water samples <br /> The current and past ground water sample analytical results are summarized on Table 2 The <br /> I laboratory report (MAI Sample ID Nos 55739-55746), QA/QC report and chain-of-custody form <br /> are included in Appendix B <br /> I • 4.0. SUMMARY AND CONCLUSIONS <br /> The following conclusions were drawn from the results of this investigation <br /> • Depth to ground water ranged from 6 93 feet to 7 98 feet below the well casing tops The <br /> I prevailing ground water flow direction in December 2000 is towards the north The hydraulic <br /> gradient (0 004 feet/feet) indicates that the ground water table is nearly flat <br /> I0 The dissolved hydrocarbon plume extends northward from the former UST and dispenser <br /> areas beyond the two down-gradient monitoring wells (MW-5 and MW-8) The plume is <br /> defined to the south and west by monitoring wells MW-1 and MW-3, respectively <br /> l0 The hydrocarbon and MTBE concentrations in MW-5, MW-7 and MW-8 have increased, <br /> concentrations in MW-2 have decreased and concentrations in MW-4 have remained <br /> relatively stable since the last monitoring event in September 2000 <br /> I5.0. RECOMMENDATIONS <br /> Based On the findings of the this investigation, AGE recommends continued quarterly monitoring <br /> Iof the ground water monitoring wells The next monitoring event should be performed in March <br /> 2000 <br /> Advanced GeoEnvironmental,inc <br />