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CLEARWATER G R O U P Envi3On OMal Services Periodically throughout the GWE/SVE/AS testing, pressure was measured in wells MW-1, MW-513, MW-6, and MW-7 Throughout testing the pressure in MW-SB, the nearest well to DPW-1, was measured between 0 1 and 0 8 r in w c Pressures in MW-1, which is approximately 50 feet from AS-1, were measured between 0 50 and 0 60 in w c No pressures were measured in MW-6 and MW-7 After two hours of testing the sparge compressor no longer operated and the induced pressure in MW-513 and MW-1 dropped off For over one hour after sparging, SVE and GWE continued Pressures in surrounding wells (MW-1, MW-513, MW-6, and MW-7) were still measured periodically A constant vacuum of 0 04 in w c was measured in MW-513 No pressure was detected to wells MW- 1, MW-6, and MW-7 after sparging stopped Since MW-1 showed some significant change in pressure during sparge testing,these results suggest that sparging has an effective radius of approximately 60 feet at the site 1 An air sample, labeled INF-SP, was collected from DPW-1 once sparging was complete The contaminant concentrations detected in this sample were significantly greater than air samples collected during SVE testing without air sparging In this sample TPHg was detected at a concentration of 1000 mg/m3 and benzene at 3 7 mg/m3 ' Complete laboratory analytical results are included in Appendix C Conclusions and Recommendations '* Clearwater installed a dual-phase test well (DPW-1) and an air sparge test well (AS-1) These wells were used in conjunction with existing monitoring wells to perform 1) GWE step drawdown tests, 2) dual-phase GWE/SVE tests, 3) and combined GWE/SVE/AS testing ' Results of testing indicated that the subsurface was of relatively low to moderate permeability, as evidenced by the extraction rates of both groundwater and soil vapor DPW-1 could only sustain a pumping rate of 1 75 gpm without SVE and 2 1 to 2 5 during SVE, to sustain drawdown of approximately 15 feet A vacuum of 50 in w c applied to ' DPW-1 resulted in an air flow of 10 4 to 11 cfm If SVE were used for remediation at DPW-1, initial TPHg recovery rates from well DPW-1 would be approximately 0 022 lbs/day [calculated Yield = influent concentration ' (mg/m ) x flow (cfm) x (m3/35 31 ft') x 1440 nun/day x (lb/453,592 mg)] If SVE alone were contemplated as a remedial strategy, up to 60 extraction wells would be required, at a mimmum,to cover the aerial extent of the known sorbed-phase plume based on an effective radius of influence of 6 to 8 feet for one extraction well The SVE/AS results demonstrate that air is more easily pumped into the ground by AS than can be recovered from ' SVE, since positive pressure was measured in surrounding wells during GWE/SVE/IAS rather than a vacuum This positive pressure during SVE/AS in surrounding wells was much greater than the vacuum observed during ' GWE/SVE testing ' ZB178C Feas Test Report 8 May 9, 2002