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' 23 April 1999 <br /> • AGE-NC Project No. 95-0100 <br /> 1 Page 5 of 6 <br /> 1 The analytical results of the `grab' ground water sample are summarized in Tables 3 and 4. The <br /> laboratory report (MAI Lab ID 03472),QA/QC report and chain-of-custody form are included in <br /> Appendix B. <br /> 1 <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> Based on the data collected from the site, AGE finds: <br />' Petroleum hydrocarbons were detected in the soil sample analyzed from the boring advanced <br /> at the site. The highest concentrations of petroleum hydrocarbons in soil remain at depths of <br /> 10 feet and 15 feet bsg below the former fuel dispenser area. The reduction of hydrocarbon <br /> 1 concentrations in soil ranged between 46 % and 77 % at a depth of 15 feet bsg and <br /> approximately 60 % in the soil above 10 feet bsg. <br /> 1 • Benzene was not detected in the samples collected near former sampling points of benzene <br /> detection. The reduction of benzene concentrations at adept of 10 feet to 15 feet is virtually <br /> 100%, while the estimated reduction of benzene at a depth of 25 feet to 30 feet bsg is <br /> 1 approximately 95 %. <br /> MTBE was detected at a significant concentration(22 mg/kg) in a soil sample at a depth of <br /> 1 15 feet bsg, and at Iower concentrations (0.65 and 0.097 mg/kg) in soil above or near the <br /> ground water table. <br /> • Toluene,ethylbenzene and xylene were detected in the `grab' ground water sample collected <br /> from the site. MTBE was detected in the water sample collected. The MTBE concentration <br /> exceeded the DHS action level for drinking water. <br /> 1 5.0. RECOMMENDATIONS <br /> Based on the findings of the post remedial sampling and the detection of MTBE in ground water, <br /> AGE recommends: <br /> • Preparation of a work plan for installation of four ground water wells at the site to delineate <br /> _the extent.of_.the,MTBE impact to-the.ground water.,- <br /> • A quarterly ground water monitoring program should be initiated at the site following <br />' installation of ground water monitoring wells. Sampling analysis of the ground water should <br /> include EPA Methods 8015 Modified, 8020 and 8260 Modified. <br /> i <br /> AdrancedGeoEnvironmental,Inc. <br />