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. 09 March 2001 AGE-NC Project No 96-0254 ' Page 3 of 4 ' 3 2 LABORATORY RESULTS OF GROUND WATER SAMPLES TPH-g was detected in samples collected from wells MW-1B, MW-4 and MW-7 at concentrations of 1,800 micrograms per liter(/.zg/1), 980,ug/l, and 150,ug/l, respectively TPH-d was detected in the samples collected from wells MW-lA, MW-1B, MW-4 and MW-7 at concentrations of 52,ug/l, 140 yg/l, 120 ,ug/l and 130 µg11, respectively TPH-g and TPH-d were not detected in the remaining ' samples BTEX compounds were detected In samples collected from wells MW-lA, MW-1B, MW-4 and MW-7 Benzene ranged from 12 µg/1 in sample MW-lA to 710 ,ug/l in sample MW-1B Toluene, ethylbenzene and xylenes were detected in these same wells at concentrations ranging from 0 56,ug/1 of toluene in MW-IA to 48 µg/1 of ethylbenzene in MW-1B MTBE was detected in samples MW-1B and MW-4 at concentrations of 20 4g/l and 4 1 /.Zg/l, respectively No other fuel oxygenates were detected in the ground water samples The analytical results are summarized in Table 2 The laboratory reports (MAI Laboratory ID 59146 � . to 59155), QA/QC reports and chain-of-custody forms are included in Appendix B 4.0. SUMMARY AND CONCLUSIONS Based on the data collected during this monitoring period, AGE concludes • The depth to ground water at the site was encountered between 6 92 to 7 78 feet bsg, excluding MW-7 The average ground water elevation was 0 34 feet higher than the average ground water elevation last quarter The prevailing ground water flow direction at the site is generally northward which is consistent with the previously determined flow directions • Petroleum hydrocarbon-impacted ground water was encountered in samples from monitoring wells MW-1B, MW-4, and MW-7 with benzene concentrations exceeding the State of California maximum contaminant level(MCL)of 1 ppb in samples MW-1B and MW-4 Low concentrations of MTBE were detected in samples MW-1B and MW-4 In general, overall hydrocarbon concentrations have dropped this quarter The current TPH-g, TPH-d, benzene and MTBE Isocontours in the shallow screened wells is depicted on Figures 4, 5, 6, 7 • Elevated concentrations of hydrocarbons are present in the MW-7 which is screened between 37 and 42 feet bsg The extent of the hydrocarbon Impact at thus deeper interval is unknown I Advanced GeoEnvironmentai Inc