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Ms Vicki McCartney Project No 8800401A 0201 <br /> October 26, 2004 <br />' Page 10 <br /> DPE <br /> DPE involves removing; soil vapor and groundwater from beneath the site via an <br /> extraction well utilizing a high vacuum liquid ring blower The extracted groundwater <br /> would be disposed of utilizing existing sewer facilities, and the extracted soil vapor is �. <br /> treated before release to the atmosphere using a thermal oxidizer Based on the extent of <br /> groundwater and possible soil impact on-site, and the high vacuum applied by the DPE <br /> system, a majority of the subsurface impact could be removed in a reasonable period of <br /> time Groundwater monitoring would continue for up to one year following completion <br /> of DPE activities to confirm mass reduction <br /> Cost $408,00000 <br /> Time Frame 4 years <br /> Advantages ➢ Removal of sod vapor can reduce residual and potential source <br /> hydrocarbon concentrations <br /> ➢ Removal of hydrocarbon impacted groundwater can reduce dissolved <br /> hydrocarbon concentrations <br />' ➢ Groundwater extraction can provide hydraulic control inhibiting further <br /> downgradient migration hydrocarbon plume <br />' Disadvantages ➢ Initial installation and operation costs for the DPE system could be high <br /> ➢ Some disruption of station activities in order to install and Operate the <br /> extraction system <br />' ➢ This method is slightly less protective of the environmental as <br /> hydrocarbon impacted groundwater is transported above ground, <br /> increasing risk of release to the environment <br /> ■ The rationale for selecting the preferred remedial alternative for restoring and <br /> protecting impacted or threatened waters <br />' Shaw recommends ozone micros arge as the remedial alternative for its effectiveness <br /> P <br />' and relatively rapid remedial action against the constituents of concern at the site This <br /> option is preferred because it has the possibility to expedite site closure, and is lower in <br /> cost compared to long-term groundwater monitoring or DPE <br /> 1 <br /> N 1sacDPQ00410g188048800401A 4ad doc Shaw Environmental,Inc <br />