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1 ' <br />' 29 January 2001 <br /> AGE-NC Project No 00-0725 <br />' Page 10 of 11 <br /> Y <br />' 5.0. SUMMARY AND CONCLUSIONS <br /> Based on the data collected from the site, AGE finds <br /> - The highest concentrations of petroleum hydrocarbons as gasoline in soil were detected in <br /> samples collected from the north wall of the former gasoline UST area during removal of soil <br />' underlying the former dispenser area and in the soil sample collected from the bottom of the <br /> soil boring (15 feet bsg) for the installation of well MW-2, near the dispenser excavation <br /> Lower concentrations of petroleum hydrocarbons as gasoline were detected In soil samples <br />' recovered from other portions of the former UST area <br /> AGE calculates that approximately 13 gallons of gasoline were removed In the soil excavated <br />' during the Interim remediation on the site In March 2000 Appendix E presents the <br /> calculations for the hydrocarbon-mass removed, based on analytical results from soil <br /> samples <br /> - Concentrations of petroleum hydrocarbons were detected in two composite soil samples <br /> recovered from soil stockpiles at the site <br /> - The ground water surface was Inferred to be flowing north and south, divergent from the <br /> excavation area with an average gradient of 0 001 feet/feet <br /> - Monitoring wells have been Impacted by detectable concentrations of petroleum <br /> hydrocarbons and various BTEX compounds <br /> - The horizontal extent of TPH-Impacted ground water is fairly well delineated, except to the <br /> west of the site The current ground water monitoring well system appears to enclose the <br /> benzene-Impacted ground water plume margins on the east, south and north Figure 2 depicts <br />' the extent of dissolved benzene above 0 5 µg/1 <br /> 6.0. RECOMMENDATIONS <br /> Based on the findings of the environmental activities recounted in this report, AGE recommends <br /> A quarterly ground water monitoring program should be Initiated at the site and sampling <br /> should be scheduled for February 2001 <br /> The lateral extant of the dissolved hydrocarbon-impact to the ground water should be <br /> assessed with the Installation of a well west of the site <br /> Advanced GeoEnvironmental,Inc <br />