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10 June 1998 <br /> AGE-NC Project No. 96-0229 <br /> r+�r <br /> Page 3 of 5 <br /> 1.0 <br /> contouring ground water elevations in Figure 3 due to anomalous measurements, which may be <br /> caused by the well being completed in a different hydrological portion of the aquifer. MW-1 is <br /> screened at 48 to 53 feet below surface grade (bsg) while ground water lies approximately 24 feet <br /> (-24 feet over the screen), while the other wells are screened very close to the current ground water <br /> elevation. <br /> 3.2. DISSOLVED OXYGEN MEASUREMENTS <br /> During the May 1998 ground water monitoring event, dissolved oxygen measurements were <br /> +,• recorded while purging the monitoring wells. Dissolved oxygen measurements ranged from 0.13 <br /> parts per million(MW-6)to 1.28 parts per million (MW-5). Results of dissolved oxygen in ground <br /> water samples are summarized in Table No. 2. <br /> 4. <br /> 3.3. ANALYTICAL RESULTS OF GROUND WATER SAMPLES <br /> Utilizing EPA method 8015M. TPH-g was detected in ground water samples collected from wells <br /> MW-1 through MW-3 and MW-6 at concentrations ranging as high as 91,000 parts per billion(ppb, <br /> reported as micrograms per liter). <br /> Utilizing EPA method 8020, BTE&X compounds were detected in samples collected from each well <br /> at concentrations ranging up to 25,000 ppb (xylene, MW-2). Benzene concentrations were detected <br /> in ground water samples collected from wells MW-1 through MW-3 and MW-6 at concentrations <br /> �. ranging as high as 5,600 ppb. MTBE was detected from wells MW-1 and MW-4 at concentrations <br /> ranging as high as 780 ppb. <br /> Utilizing EPA method 8260, MTBE was confirmed in ground water samples collected from MW-1 <br /> and MW-4 at concentrations ranging as high as 620 ppb. TBA was detected for the first time in a <br /> ground water sample collected from MW-4 at a concentration of 6.1 ppb. TAME, DIPS and ETBE <br /> " were not detected in the laboratory analysis of any ground water samples. The analytical results for <br /> ground water samples are summarized in Table 3. <br /> V <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> V <br /> Based on the results of ground water monitoring and sampling activities performed in May 1998, <br /> AGE concludes: <br /> • The site gradient was calculated at 0.003 ft/ft, or approximately 17 feet per mile (Figure 3). <br /> �+ Advanced GeoEnviranmentoi,Inc. <br />