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1 <br /> . 26 July 2002 <br />' AGE-NC Project No. 95-0100 <br /> Page 3 of 4 <br />' Ground water elevation at the site decreased an average 0.5 feet between the January 2002 and.lune <br /> .2002 ground water monitoring events. The ground water flow direction for the sampling event was <br /> inferred to be toward the northwest at an average gradient of 0.0026 feet/feet. Data from MW-4 was <br /> not used to determine ground water gradient, as this well is screened at a deeper interval than the <br /> other wells. Figure 3 illustrates the contoured ground water elevations. <br /> 3.2. GROUND WATER ANALYTICAL RESULTS <br /> During the sampling event MTBE was detected in MW-1 and MW-3 by EPA method 8260B at <br /> 0.73 micrograms per liter(µg/1) and 41 µg/l, respectively. No other target analytes were detected in <br /> ' the samples analyzed. <br /> Analytical results of ground water samples are summarized in Table 2. Copies of the laboratory <br /> ' reports(McCampbell Analytical Laboratoryll)0206273-001 B to 0206273-006B),quality assurance <br /> and quality control (QA/QC) data and chain-of-custody forms are in Appendix B. <br /> 1• <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> ' Based on the findings of this and previous investigations, AGE concludes the following: <br /> ' The ground water flow direction was toward the northwest during the sampling event. <br /> • Since February 2001,TPH-g,-BTEX compounds and fuel oxygenates except MTBE have not <br /> been detected in analyzed well samples. <br /> ' MTBE was detected in samples from monitoring wells MW-1 and MW-3 at concentrations <br /> as high as 41 ug/1(MW-3).However,MTBE concentrations generally appear to be declining <br /> ' since the February 2001 monitoring event. <br /> • The MTBE concentration in sample MW-3 exceeded the State of California maximum <br /> contaminant level (MCL) of 13 µg/l in drinking water. <br /> ' 0 The down-gradient extent of MTBE-impacted ground water has been defined. <br /> 5.0. RECOMMENDATIONS <br /> ' Based on the findings of investigations to elate,AGE recommends preparation of a Closure Summary <br /> • Report for this site. <br /> Advanced GeoEnvironmental,Inc. <br /> 1 <br />