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beneath the retort pit. Components of the selected remediation <br /> alternative include: <br /> • Replace the synthetic liner in the bottom of the retort pit with <br /> an upgraded liner,, retort fluid capture system, and a leak <br /> detection system if wood treating continues beyond July 1, 1991. <br /> • Install and operate a system to flush deep soils with water to <br /> enhance the removal of hexavalent chromium in the pore water. <br /> • Monitor the deep soils for wood treating chemicals. <br /> • Upon cessation of deep soil flushing (projected to take <br /> approximately 5 years) , a closure plan for the retort pit will be <br /> developed in accordance with all statuatory requirements, includin <br /> the federal Resource Conservation and Recovery Act (RCRA� <br /> standards. <br /> This document has been prepared to supplement the Subsurface Soil Flushing <br /> System construction plans and specifications (MCTC Contract No. 13). The <br /> following sections describe the subsurface soil flushing system and the <br /> scope of sampling and monitoring activities associated with the subsurface <br /> soil flushing system. <br /> 1.2 DESCRIPTION OF SUBSURFACE SOIL FLUSHING SYSTEM <br /> The subsurface soil flushing system will consist of the following <br /> components as shown on Figure 1-2: <br /> • Eleven injection wells. <br /> • Two extraction wells (MW-206 is an existing monitoring well that <br /> will be used for ground water extraction). <br /> • An injection water supply tank and injection water supply piping. <br /> • An extracted water holding tank and extracted water collection <br /> piping. <br /> • Twelve neutron probe monitoring tubes. <br /> • Four lysimeter nests (L-246,247,248 and L-242,243,244 are existing <br /> lysimeters). <br /> • Two piezometers (P-231 and P-235 are existing peizometers) . <br /> The primary injection water supply source will be the effluent from <br /> existing water treatment systems at MCTC's facility. The secondary source <br /> of water for injection will be water from public drinking water sources. <br /> Potable water will be used to refill the injection water holding tank when <br /> effluent flow from the existing water treatment systems is not adequate to <br /> replenish the injection water supply tank. The injection water supply <br /> piping system will be a gravity system that will be full at all times. <br /> 11654.652 1-2 <br />