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CLEARWATER <br /> G R O U P I N C <br /> ® Install remediation system - obtain electric power drop, construct compound, <br /> install utility trench, install recovery well RW-2, reconfigure wellheads, install <br /> pumps in RW-1 and RW-2, plumb wells as appropriate for either dual-phase soil <br /> and groundwater extraction or soil vapor extraction, <br /> 0 Start-up system pumping from RW-1 and RW-2 at approximately 5 gpm each, <br /> extract soil vapor from RW-1, RW-2, VW-1, VW-2, and VW-3 with a vacuum of <br /> approximately 60 in w c , treat vapors with rental IC engine, monitor <br /> groundwater and soil vapor extraction and discharge as required by permits, <br /> 0 Switch out rental IC engine for regenerative blower and vapor-phase GAC once <br />' influent TPHg concentrations in soil vapor drop below approximately 1,000 <br /> ppmv, <br /> 0 Turn on air sparge well after SPH is not measurable in any wells, and is no <br /> longer being recovered by pumps in RW-1 and RW-2, <br /> 1 0 Although soil will likely be remediated before groundwater, continue to operate <br /> groundwater extraction to mitigate plume migration, and continue air sparging <br /> and soil vapor extraction to recover sparged air, <br /> have reached clean-up Once hydrocarbon levels in groundwaterp levels mandated <br /> by PHS/EHD, shut down system and drill confirmation borings and monitor <br />' groundwater quarterly for one year, <br /> If dissolved hydrocarbon concentrations remain acceptable after one year and <br />' confirmation borings are free of detectable concentrations of gasoline <br /> compounds, petition for regulatory closure, <br />' o Decommission all wells and system components upon receipt of regulatory <br /> closure <br /> 8.0 CONCLUSIONS <br /> ' Based on the results of cumulative subsurface investigations and recent feasibility <br /> testing, Clearwater recommends a remedial approach consisting of dual-phase <br /> groundwater and soil vapor extraction from two recovery wells (RW-1 and <br /> ' proposed RW-2) and soil vapor extraction from three vapor wells (VW-1, VW-2, <br /> and VW-3) Groundwater extraction from RW-1 and proposed RW-2 at flowrates <br /> greater than 5 gpm each should create a zone of capture large enough to mitigate the <br /> migration of the dissolved plume and recover SPH in the vicinity of MW-1 The <br /> water should be passed through an oil/water separator prior to treatment by <br /> aqueous-phase GAC Air sparging can be initiated to enhance groundwater <br /> ' D-107,PAR/RAP 26 February 21, 1996 <br />