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w 4J� <br /> ?y rq <br /> • A S S O C I A T E S I N C <br /> J <br /> S <br />' Based on the dye tracer test, the application of DDC at the site produces an approximate radius of <br /> influence of approximately 20 feet As shown 2n Section 6 5, approximately 0 28 pounds of <br /> ' TPHg and benzene were removed during one day of the air sparge pilot test and this yields a <br /> removal of 8 68 pounds of TPHg and benzene during the 31-day pilot test The in-well stripping <br /> ' efficiency of approximately 45% was a little Iower than anticipated This is likely due to the <br /> high concentrations of petroleum hydrocarbons in soil in the vicinity of the sparge well Over <br /> the short period of time of the air sparge test, the petroleum hydrocarbons in the soil provided a <br /> ' source of material that skewed the stripping efficiency downward Once the vapor extraction and <br /> air sparge systems are operational full-time, the amount of source material will be quickly <br /> decreased and the in-well stripping efficiency should go up to approximately 80% Air sparge <br /> ' appears to be a viable method for remediating TPHg and BTEX impacted groundwater at the <br /> site <br /> 9.0 RECOMMENDATIONS <br /> ATC recommends installing a soil vapor extraction and DDC air sparge remediation system at <br /> the site Upon regulatory concurrence of the preferred remedial action method and client <br /> approval, ATC Associates will prepare and submit a final remediation plan, which wiII include a <br /> conceptual design of the remediation system ATC will continue to monitor wells MW1 through <br /> MW 10 and DW quarterly ATC will also continue to monitor the passive skimmer system in <br /> well MW2 monthly <br /> 1 <br /> w 1163931reports\nfs doc 17 <br /> 1 <br />