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1 <br /> 22 February 2002 <br /> . AGE-NC Project No. 95-0100 <br /> 1 Page 3 of 4 <br /> Ground water elevation at the site decreased an average 0.7 feet between the November 2001 and <br />' January 2002 ground water monitoring events. The ground water flow direction for the sampling <br /> event was inferred to be toward the north or northwest at an average gradient of 0.002 feet/feet.Data <br /> from MW-4 was not used to determine ground water gradient, as this well is screened at a deeper <br />' interval than the 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 8260 at <br />' 56 micrograms per liter(µg/1) and 79 µg/1, respectively. <br /> Analytical results of ground water samples are summarized in Table 2. Copies of the laboratory <br />' reports (McCampbell Analytical Laboratory ID 89330 to 89335), quality assurance and quality <br /> control (QA/QC) data and chain-of-custody forms are in Appendix B. <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 /> • MTBE was detected in samples from monitoring wells MW-1 and MW-3 at concentrations <br /> as high as 79 µg/l. <br />' 0 The MTBE concentrations exceeded the State of California maximum contaminant level <br /> (MCL) of 13 µg/l in the water samples collected from wells MW-1 and MW-3. <br />' 0 The down-gradient extent of MTBE-impacted ground water has been defined. <br />' 5.0. RECOMMENDATIONS <br />' A workplan to abandon domestic well DW-1 has recently been approved by San Joaquin County <br /> PHS-EHD. AGE anticipates the work will be performed by March 2002. <br /> Advanced GeoEnvironmental,Inc. <br /> 1 <br />