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2. TECHNICAL APPROACH AND SCOPE <br /> EA proposes to remediate soils and groundwater at former Exxon RS 7-3942 by extracting and <br /> treating both soil vapor and groundwater concurrently Phase 1 of the remediation, an immedi- <br /> ate, interim program, includes the following: <br /> 1. Install and sample the new offsite groundwater monitoring wells to define <br /> the extent of the dissolved petroleum hydrocarbon plume. <br /> 2 Permit and carry out the disposal of treated groundwater to the sanitary <br />' sewer and injection wells, a portion of the water will be reinjected into the <br /> aquifer in onsite wells to create a hydraulic barrier. <br />' 3 Construct and operate the groundwater extraction and treatment system <br /> (GETS) extract groundwater from five wells to begin immediate capture of <br />' the plume; treat extracted groundwater on the site with a system that will <br /> include an air stripper, an activated carbon polish of the air-stripped water, <br /> and catalytic oxidation of petroleum hydrocarbon vapors. <br /> 4 Construct and operate a vapor extraction and treatment system (VETS) <br /> extract soil vapor from nine wells and treat the extracted vapors by catalytic <br /> oxidation (the GETS air stripper will be vented to the VETS so that petrole- <br /> um hydrocarbon vapors from the two systems can be oxidized together) <br />' 5. Actively monitor the operational areas of influence of the VETS and the <br /> GETS by installing and operating vapor monitoring wells and sampling for <br />' concentrations of petroleum hydrocarbons and drawdown of the water table <br /> in the onsite and offsite wells <br /> Phase 2 is a longer-term program that includes the following elements: <br /> 1 Model groundwater flow and the fate of hydrocarbon constituents again to <br /> optimize the containment of the dissolved petroleum hydrocarbon plume and <br /> the remediation of groundwater The model will be based on the operational <br /> ' areas of influence of groundwater extraction from the existing wells and <br /> definition of the petroleum hydrocarbon plume <br /> 2 Propose, and install as necessary, additional extraction wells to control <br /> plume migration and to provide the area of influence necessary to optimally <br /> contain and extract groundwater that contains petroleum hydrocarbons. <br /> ' c6ww 6n3942rjd91Ax l 1 <br />