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Future operation of the AS/SVE system will be continuous until the soil vapor concentration <br /> has consistently dropped below 500 parts per million volume (ppmv). At that point, the <br /> j engine will be replaced by granular activated carbon (GAC), and the AS/SVE blowers will AV , <br /> begin cycled operation. Blower cycling will improve groundwater mixing, improve treatment <br /> effectiveness, and reduce operating cost. Cycling will begin with a 4-hours-on/4-hours-off <br /> period. This period of system cycling will be adjusted quarterly as the equilibrium soil vapor <br /> concentration drops off by extending the off cycle. <br /> AS/SVE System Monitoring Results <br /> Average Operating Conditions <br /> Since start-up, the AS/SVE system has experienced a rapid decline in soil vapor <br /> concentration from more than 10,000.ppmv VOC to an average concentration of 2,800 ppmv <br /> during the fourth week .of continuous operation. With the decline in gasoline vapor <br /> concentration, the soil vapor oxygen concentration has consequently risen from an initial <br /> level of 8 percent to an average of 20.5 percent (20.9 percent is the ambient air oxygen level) <br /> in the fourth week of operation. Valve adjustments have been blade (1) to regulate dilution <br /> air to keep the engine running, (2) to balance air flow between wells, and (3) to maintain a <br /> 2:1 SVE to AS flow ratio to ensure that more soil vapor is removed from the ground than the <br /> volume of air sparged into the groundwater. The objective of this target ratio is to prevent the <br /> outward migration of contamination that could occur if air sparging were not accompanied by <br /> SVE. <br /> The results of weekly monitoring through March 15, 1995, indicate that the AS/SVE system <br /> has been operating under the following conditions: <br /> Operation Parameter Measured Value <br /> Average Vapor Extraction Flow 79 standard cubic feet per <br /> minute (scfm) <br /> Average Vacuum Pressure -48 inches of water <br /> Average Temperature (engine intake 86 degrees F <br /> temperature) <br /> E Cumulative Operating Time 1,157 hours <br /> i Average VOC Concentration 3,830.ppmv <br /> This remediation system is still being debugged, and steady state operation is just.be innin <br /> g <br /> at this writing. <br /> f <br /> 1 SF010030981.doc 2-3 <br />