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1 . <br /> I20 November 2002 <br /> • AGE-NC Project No 99-0637 <br />' Page 3 of 4 <br /> The analytical results of ground water samples are summarized on Tables 2 and 3 The laboratory <br />' reports (MAI Lab IDs 0210391-001 through 0210391-007), QA/QC report and chain-of-custody <br /> form are included in Appendix B <br />' 4.0. SUMMARY AND CONCLUSIONS <br />' Based on the data collected from the site, AGE concludes <br /> • Ground water flow at the site on 18 October 2002 was inferred to be toward the northwest <br />' at an average gradient of 0 003 feet/feet <br /> • MTBE was detected in the ground water samples collected from MW 1, MW4, MW5 and <br />' MW6 at concentrations as high as 2,000 µg/l(MW4) No other analytes were detected in the <br /> ground water samples collected at the site <br /> • MTBE concentrations remained relatively stable in wells MW 1, MW4 and MW6 and <br />' decreased from 3,600 µg/1 to 89 µg/1 in well MW5 compared to the July 2002 sampling <br /> event However, the MTBE concentration in well MW6 exceeded the DHS' Secondary <br /> Maximum Contaminant Level(MCL) of 5 µg/1 in drinking water, and the concentrations in <br />'. wells MW4 and MW5 exceeded the Primary MCL of 13 µg/1 In dnnking water <br /> • The lateral extent of MTBE-impacted ground water has been defined toward the south and <br />' east The current MTBE isoconcentration map is depicted on Figure 4 <br />' 5.0. RECOMMENDATIONS <br />' Based on the findings of the environmental activities recounted in this report, AGE recommends <br /> continued quarterly monitoring of the ground water monitoring wells on-site The next monitoring <br /> event should be performed in February 2003 <br />' A work plan to assess the lateral extent of MTBE-impacted ground water has recently been <br /> submitted to San Joaquin County EHD AGE anticipates the work plan will be approved before the <br />' end of the year and field work will be performed during the first quarter 2003 <br />' 6.0. LIMITATIONS <br /> Our professional services were performed using that degree of care and skill ordinarily exercised by <br />' environmental consultants practicing in this or similar localities The findings were based upon <br /> analytical results provided by an independent laboratory Evaluation of the hydrogeologlc conditions <br /> at the site for the purpose of this investigation was made from a limited number of available data <br />' Advanced GeoEnvironmental,Inc <br />