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, <br /> CLEARWATER <br /> G R d U P, I N C. <br /> Eavi rouvocn tal Servires <br /> .Based on the flow rates, vacuums, well screens, and radius of influence data, the soil <br /> air permeabilities were approximated according to Johnson, et al., (1990) using the i <br /> software guidance system HyperVentilate c0. The results indicate that the <br /> permeability of the vadose zone soil around VW-2 and VW-3 are similar, and are <br /> approximately 3 to 4 darcies. Vacuum, flow rate and permeability data is presented <br /> in Appendix E. <br /> Soil vapors were tested from wells VW-1, VW-2, and VW-3 to evaluate volatile soil <br /> gas concentrations. These samples were analyzed for TPHg and BTEX by Trace <br /> Y Y <br /> Analysis Laboratory, Inc: The sample results from VW-1 revealed 27,000 mg/m3 <br /> TPHg and 6,840 mg/m3 total BTEX with the vapor extraction system operating. The <br /> sample results from VW-2 revealed 150,000 mg/m3 TPHg and 35,900 mg/m3 total <br /> BTEX with the vapor extraction system operating. The sample results from VW-3 <br /> revealed 130,000. mg/m3 TPHg and 29,200 mg/m3 total BTEX with the vapor <br /> extraction system operating. Air sample analytical results are summarized on Table <br /> 5. Certified analytical reports are presented in Appendix B. <br /> r The sample results indicate that volatilization from the groundwater/air interface is <br /> significant, particularly in the vicinity of VW-2 and VW-3. At the flow rates <br /> induced during the test (12 cfm), hydrocarbon recovery rates from VW-2 and VW-3 <br /> were approximately 150 lbs/day (25 gal/day) each. Although hydrocarbon <br /> concentrations were less :in the sample from VW-1, the higher flowrates achieved <br />� from that well (60 cfm) produced hydrocarbon recovery rates of approximately 145 <br /> lbs/day (24 gal/day), comparable to wells VW-2 and VW-3. Again, it is worth noting <br /> that approximately a tenth of the contaminated soil pore volume was extracted <br /> when the air samples were collected. Hydrocarbon recovery rates over a moderate <br /> period of time (several months) would likely be lower than those presented here. <br /> rates an order of magnitude lower. <br /> term hydrocarbon recover g <br /> However, if long y. Y . <br /> than those presented here, they are still great enough to consider soil vapor <br /> rextraction as a remedial alternative. <br />' 5.3.4 Air Sparge Test Results <br /> Following the soil vapor extraction test on VW-3, an air sparge test was conducted <br /> using sparge welhSW 1 Vapor continued to be extracted from VW-3 during the <br /> sparge test. An initially -high pressure (15 psi) was required to overcome capillary <br /> pressures and induce flow into the sparge well. Once flow was induced, pressures <br /> i. <br /> dropped to 7 psi and the flow stabilized around 13 cfm. At the. same time, a vacuum <br /> of 46 in. w.c. column was .applied to VW-3, which produced a flowrate of 8 cfm. <br /> Pressures were ,observed-in all observation wells, indicating that vapor extraction <br /> from VW-3 was unable to'capture -all sparge vapors. In an attempt to control sparge <br /> vapors, flow into the sparge well was reduced to 10 cfm at 3 psi, and vacuum at VW- <br /> 3 was increased to 60 in. w.c., which produced a flowrate of 11 cfm (the limit-of the <br /> { test blower package). At these vacuums/pressures and flowrates, observation wells <br /> D-107,PAR/RAP 13 June 11, 1996 <br />