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' The system uses a Ford Motors 300 cu. in. 6-cylinder internal combustion engine to drive <br /> a vacuum blower and withdraw pore vapor from the subsurface in the vicinity of the <br /> extraction well bore. Propane was used as a supplemental fuel source to start and operate <br /> the engine. A 55-gallon drum between the well and the engine is used to separate and <br /> collect liquids before they enter the blower and engine. Combusted gasses pass through a <br />' catalytic converter before being vented to the atmosphere. <br /> Air flow was monitored throughout the 8-hour test. Magnehelic vacuum gauges tapped into <br />' the PVC piping measured the vacuum at the wellhead and between the drum and blower. <br /> A sample port was tapped into the PVC near the wellhead, and a portable photo-ionization <br /> detector (Microtip model 1000 calibrated to isobutylene)was used to measure organic vapor <br />' concentrations at half-hour intervals. The port was also used to collect vapor samples in <br /> tedlar bags. Three samples were collected during the test and transmitted to WEST <br />' Laboratories in Davis, California for analysis of TPH and BTE&X. <br /> A magnehelic was also connected alternately to groundwater monitoring wells MW-1 and <br />' MW-3 to measure the vacuum in these wells. The purpose of this monitoring was to <br /> estimate the radius of influence exerted by vapor extraction from RW-1. <br />' For most of the test, vacuum readings ranged between 1.5 and 2.0 inches of water at the <br /> wellhead. Readings were lower at the 55-gallon drum, ranging from 1.0 to 2.0 inches. At <br /> MW-1, 15 feet from RW-1, the initial vacuum was between 0.5 and 1.0 inch of water, but <br /> gradually decreased to 0.21 inches after four hours and remained constant thereafter. At <br /> MW-3, 55 feet from RW-1, the initial vacuum was 0.15 inches, but decreased to 0.04 inches <br /> after three hours and fluctuated between 0.04 and 0.06 inches thereafter. These results <br />' indicate that RW-1 exerted a strong vacuum at MW-1, and vapor extraction should have an <br /> effective radius of 25 to 35 feet at this site. The radius of the vadose zone contaminant <br /> plume is inferred to be 20 to 25 feet. <br />' During the test, PID readings consistently exceeded the upper limit of the instrument (2,500 <br /> ppm). Vapor samples confirm the high concentrations of extracted hydrocarbons (Table 5 <br />' and Appendix F). PID and laboratory data thus confirm that soil conditions at this site are <br /> conducive to rapid removal of high concentrations of hydrocarbons. <br />' 6.1.2.2.6 Duration <br /> Because RW-1 is optimally located and soil permeability is high, vapor extraction systems <br /> iare likely to reach peak efficiency within the first few days of operation. Based on the <br /> concentrations of hydrocarbons recovered during the pilot test, we estimate that an internal <br />' combustion system would reach the limits of efficient operation within 3 to 6 months. At <br /> these concentrations, a thermal oxidation system would be effective for 6 to 18 months, at <br /> t <br /> 6eole�n]Audo,S.­1— <br /> ° ARA A.gWl.2g-yy/k.J7 <br />