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iDuring the months of July and August 1990, the groundwater contaminant <br /> concentrations were not decreasing at a rate satisfactory to our expectations This was <br /> probably a result of using the monitoring wells as an extraction wells Therefore, in <br /> early August, monitoring wells RW-1 and MW-3 were taken off the VES and switched <br /> to vapor inlet wells in order to monitor the true rate of remediation in the groundwater <br /> surrounding these wells The VES operated with two blowers, one for MW-4 and one <br /> for MW-1 As the system operated through the months of October through December, <br /> the vapor concentrations were consistently low (below 20 ppm as methane) and <br /> groundwater concentrations decreased to less than detectable levels in these wells <br /> i <br />' On January 29, 1991, the VES was monitored for the last time and then shut off <br /> Weekly Monitoring of the Vapor Extraction System <br /> The concentration of the extracted well vapors were monitored on a weekly bass <br />' using an OVA 128-GC and intermittently using a SKC Sampling Pump with SKC carbon <br /> tubes The OVA 128-GC analyzes the extracted vapors by flame ionization for total <br /> petroleum hydrocarbons as methane The OVA 128-GC is calibrated to 96 5 ppm <br />' methane in zero gas air <br /> The SKC Sampling Pump and SKC carbon tubes are used to provide laboratory <br /> verification of the individual gasoline constituents in the extracted well vapors The <br />' SKC Pump is a calibrated industrial hygiene air sampling pump with digital flow and <br /> timing instrumentation A volumetric vapor sample is obtained by inducing the flow of <br />' the undiluted vapors from each of the individual vapor extraction wells across granular <br />' activated carbon which is contained in a pencil shaped glass tube The activated <br />' VAPOR EXTRACTION TECHNOLOGY, INC <br />