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1 <br /> 20 June 2001 <br /> AGE-NC Project No 98-0432 , <br /> ' Page 3 of 4 <br /> ' diesel UST area at a gradient of 0 003 feet/feet (15 8 feet mile) Well construction details are <br /> provided in Appendix A Figure 3 Illustrates the contoured ground water elevations <br /> ' 3 2 GROUND WATER ANALYTICAL RESULTS <br /> ' TPH-g and BTEX compounds were not detected in ground water samples TPH-d was detected in <br /> the ground water samples collected from wells MW-1 and MW-2 at concentrations of 190 <br /> ' microgram per liter(E.ag/1) and 170 /.cg/l, respectively <br /> MTBE was detected in six samples utilizing EPA method 8260 The highest concentration of MTBE <br /> ' detected was in sample MW-1 at 11,000µg/1 MTBE was also detected in the samples from wells <br /> MW-2 at 660,ug/l,MW-3 at 1 7,ug/l,MW-4 at 2 0 4g/l,MW-5 at 16,ug/l and extraction well EW-1 <br /> at 2,200 1.,tg/1 Other fuel additives were detected above detection limits in the samples <br /> ' Analytical results from ground water samples are summarized in Tables 2 and 3 The laboratory <br /> reports(MAI Laboratory ID 64495 to 64501), quality assurance and quality control(QA/QC)reports <br /> Nand chain-of-custody forms are included in Appendix B <br /> ' 4.0. SUMMARY AND CONCLUSIONS <br /> The following conclusions were drawn from the results of this investigation <br /> ' • During this quarter, the prevailing ground water flow direction is towards the northwest <br /> which is consistent with flow direction determined during previous monitoring events <br /> ' • TPH-d was detected only in MW-1 and MW-2, and were present at low concentrations <br /> ' • MTBE was detected in wells MW-1, MW-2,MW-3,MW-4 and MW-5 and extraction well <br /> EW-1 during this monitoring event The concentrations of MTBE detected in well MW-1 has <br /> declined slightly since the last quarter monitoring event <br /> ' • The detected MTBE concentrations in samples from six of the monitoring wells exceed the <br /> State of California maximum contaminant level (MCL) of 13 ug/l <br /> µ <br /> 5.0. RECOMMENDATIONS <br /> ' Based on the results of this investigation, AGE recommends <br /> f° <br />,i <br /> • A quarterly monitoring event should be scheduled for late June 2001 <br /> • Initiation of ground water extraction from well EW-1 to prevent further migration of <br /> ' MTBE-impacted ground water <br /> Advanced GeoEnviraamental,Inc. <br />