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' 09 October 2003 <br /> AGE-NC Project No 99-0637 <br />' Page 3 of 4 <br />' was detected in the sample collected from well MW9 at a concentration of 10 µg/1 An <br /> Iso-concentration map depicting the approximate distribution of dissolved MTBE is presented in <br /> Figure 4 <br />' No other analytes were detected at or above laboratory reporting limits In the ground water samples <br /> The analytical results of ground water samples are summarized on Tables 2 and 3 The laboratory <br />' report(MAI Lab Work Order No 0308193), QA/QC report and chain-of-custody form are included <br /> in Appendix B <br />' 4.0. SUMMARY AND CONCLUSIONS <br />' The following conclusions were drawn from the results of this investigation <br /> • The ground water elevations ranged from 1156 feet to 12 54 feet above MSL Ground water <br />' flow was inferred to be flowing toward the west, away from the former UST area at an <br /> average gradient of 0 005 feet/feet <br />�� • TPH-g, TPH-d,BTEX and fuel additives excluding MTBE,were not detected in any of the <br /> ground water samples collected from the site <br /> • MTBE was detected In the ground water samples collected from wells MW1, MW4, MW5 <br /> MW6 and MW9 at concentrations ranging from 14 pg/l in well MW6 to 1,100 µg/1 in well <br /> MW4 Overall, concentrations of MTBE decreased in wells MW4, MW5, MW6 and MW9 <br /> and increased in well MW1 since the last monitoring event in May 2003 <br /> • The lateral extent of impacted ground water has been defined in all directions, except <br /> towards the northwest beyond well MW9 <br /> r <br /> 5.0. RECOMMENDATIONS <br /> Based on the findings of this investigation, AGE recommends <br /> • Continuation of the quarterly ground water monitoring program The next monitoring event <br /> should be performed in November 2003 <br /> I Since the extent of the MTBE impact to soil and ground water have generally been defined, <br /> AGE believes that a Corrective Action Plan(CAP) should be prepared to determine and test <br /> the best methods of remediation A CAP will be submitted to San Joaquin EHD during the <br /> fourth quarter 2003 <br /> • <br /> i <br /> Advanced GeoEnvironmental,Inc <br />