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1 � <br /> Working To Restore Nature <br /> from 110 mg/ml in the sample collected at 15 minutes to 230 mg/m3 in the sample collected at <br /> 90 minutes The long term test was terminated after 120 minutes due to stabilization of vacuum <br /> and PID readings. Benzene vapor concentrations were detected only in well VW-2 at 0 075 <br /> ' mg/m3 The effluent vapor sample contained low concentrations of toluene (0 18 mg/m3) and <br /> xylenes (0 14 mg/m3) This was due to the high flowrate of vapor through the carbon vessels <br /> and was not considered to be breakthrough <br /> ' The results of laboratory analyses of collected vapor samples are presented in Table 4 and copies <br /> of the chain of custody records and laboratory reports are contained in Appendix D <br /> 8.0 CONCLUSIONS <br /> Based on the results of this and previous investigations, the conclusions are as follows <br /> o Groundwater contamination was present in well MW-3, located near the northern comer <br /> of the former tank pit, and in well MW-4, upgradient of the pump island. Dissolved <br /> contaminants were reported as a non-diesel mix and discrete peaks, not indicative of <br /> ' gasoline hydrocarbon contamination <br /> ' O Soil vapor extraction using the existing vapor wells is a feasible method of soil <br /> remediation at this site for petroleum hydrocarbons in the soil. <br /> O The effective radius of influence of each vapor extraction well is estimated to exceed 30 <br /> ' feet and the existing wells should sufficiently capture the extent of petroleum <br /> hydrocarbons in the soil <br /> O Based on laboratory analyses of vapor samples collected during the vapor test, the <br /> average TPHg concentration at vapor system startup is estimated at 230 mg/m3, which <br /> 1500471st-031594 FNL 12 <br /> 1 <br />