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17 August 1998 <br /> AGE-NC Project No 95-0103 <br /> 1 Page 6 of 7 <br /> • Monitoring wells MW-1,MW-2,MW-3,MW-4 and MW-5 had groundwater approximately <br /> four to seven-feet above the top of the screened interval Ground water monitoring wells <br /> have a reduced effectiveness to characterize the dissolved-phase hydrocarbon plume <br /> • The greatest concentrations of petroleum hydrocarbons were detected in samples collected <br /> from well MW-4 east of the former gasoline USTs location Hydrocarbons were detected at <br /> lesser concentrations in wells MW-1, MW-3 and MW-5 Detectable concentrations of <br /> hydrocarbons were not present in the samples collected from the off-site wells MW-2 and <br /> MW-6 and MW-7 <br /> ' • A reduction of the dissolved-phase hydrocarbon plume concentrations in the central and <br /> eastern portion of the site has occurred A minor increase of the dissolved hydrocarbon <br /> ' concentrations has occurred at the location of wells MW-3 and MW-5 <br /> • DIPE was detected in water Samples collected from MW-3 and MW-5, with a maximum <br /> concentration of 46 ppb in MW-5 MTBE was detected in samples collected from MW-I at <br /> a concentration of 38 ppb TBA was detected in the sample from well MW-1 at a <br /> concentration of 29 ppb <br /> • Between April and June of 1998, the SVE system extracted an estimated 13 gallons of <br /> gasoline from the site Since initiation of the SVE system an estimated total of 394 gallons <br /> of gasoline have been removed <br /> ' The SVE system has removed most of the hydrocarbons from the vadose soil zone in the <br /> SVE system's area of influence It is likely'that soil contamination remains in saturated soil <br /> ' in the core portion of the dissolved hydrocarbon plume <br /> • BTE&X concentrations in the extracted soil vapor has been reduced to below the detection <br /> ' limits of the soil vapor analytical method 8020 (Table 4) <br /> ' 5.0. RECOMMENDATIONS <br /> Based upon data collected over the quarter at the site, AGE recommends the following <br /> • Operation of the SVE/IAS system from the central and western portions of the site, areas <br /> t with residual hydrocarbon-impacted soil vapor and ground water <br /> • Continue monthly and quarterly ground water monitoring The next ground water monitoring <br /> event is scheduled for September 1998 <br /> rtdvanced GeoEnvaronmental,Inc <br /> 1 <br />