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