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25 August 1999 <br /> AGE-NC Protect No 98-0448 <br /> Page 9 of 10 <br /> I Various BTEX compounds were detected in ground water samples collected from wells <br /> MWA through MW-8 at concentrations between 0 82 µg/l and 16,000 µg/1, the greatest <br /> benzene concentration was detected in the ground water sample collected from MW-4B at <br /> Ia concentration of 4,900 µg/l <br /> • MTBE was detected in ground water samples collected from wells MW-1, MW-4B and <br /> MW-8 at concentrations ranging as high as 41 µg/l <br /> • DIPE was detected in ground water samples collected from MW-1 and MW-4B at <br /> concentrations as high as 10 µg/1 <br /> • TBA was detected in ground water samples collected from MW-1, MW-6 and MW- <br /> 8 at <br /> concentrations as high as 7 µg/l <br /> IFrom March 1999 to June 1999, increases in dissolved petroleum hydrocarbon <br /> concentrations were observed from wells MW-1 and MW-4B (Table 2) Conversely, a <br /> Isignificant decrease was observed from well MW-4A <br /> • From the June 1998 sampling event to the March 1999 sampling event, no dissolved <br /> I • petroleum hydrocarbons were detected in ground water samples collected from wells MW-3, <br /> MW-5 and MW-7, however, residual BTEX compounds were detected in samples collected <br /> from these wells in the June 1999 sampling event <br /> • The elevated concentrations of petroleum hydrocarbons detected In samples collected from <br /> wells MW-1, MW-2 and MW-4 indicate that these wells are within or near the dissolved <br /> Ipetroleum hydrocarbon "core area" of the plume (Figure 4) <br /> 5.0. RECOMMENDATIONS <br /> Based upon the results of this investigation, AGE recommends <br /> Continued quarterlyground water monitoring The next quarterly monitoring and sampling <br /> g <br /> is tentatively scheduled for September 1999 <br /> Completion of all regulatory pre-approved feasibility pilot tests (ground water pump test, a <br /> soil vapor extraction pilot test and an in-situ air sparge pilot test) Upon completion of all <br /> Ipilot test, a corrective action plan report should be prepared to evaluate several remedial <br /> alternatives for the site <br /> Advanced GeoEmiron mental,Inc <br />