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from the five plume margin wells will also be introduced to the Treatment <br /> System at this subsystem. <br /> A 1,100 gallon cone bottom tank constructed of high density cross-linked <br /> polyethylene will be used as an oil/water separation vessel. This vessel <br /> will provide a residence time of approximately 50 minutes, thus allowing <br /> the gravity separation of floating product and settleable solids from <br /> ground water. Following separation, floating product will be transferred <br /> to a 55-gallon steel product storage tank. The product storage tank will be <br /> installed within a secondary containment basin. Ground water effluent <br /> will be gravity drained to the ground water treatment subsystem at a rate <br /> of approximately 30 gpm. <br /> Vapor effluent from the oil/water separator vessel resulting from liquid <br /> level changes will be transferred to an off-gas carbon treatment bed. The <br /> carbon treatment bed will include 180 pounds of granular activated <br /> carbon. Any VOCs in the vapor effluent stream will be removed from the <br /> vapor stream at the carbon bed prior to atmospheric discharge of the <br /> vapor. <br /> Ground Water Treatment Subsystem <br /> The ground water treatment subsystem includes: <br /> • A multi-stage diffuser for the removal of VOCs from ground water, <br /> and an associated forced draft blower; <br /> • A 90 gallon sump pump tank, constructed of high density cross- <br /> linked polyethylene and an associated transfer pump; and <br /> • Two liquid phase carbon beds, each containing 1,800 pounds of <br /> granular activated carbon. <br /> Ground water effluent from the oil/water separator subsystem is <br /> introduced at the top of the multistage diffuser. Air enters through the <br /> bottom of the diffuser, and passes through the ground water. As air <br /> passes through the ground water, VOCs are stripped from the ground <br /> water and transferred to the vapor phase. VOC-laden vapor exits at the <br /> top of the multi-stage diffuser, and flows to the vapor treatment <br /> subsystem for treatment and discharge. <br /> Ground water flows by gravity to the sump pump tank at a design <br /> flowrate of 30 gpm. This tank provides level control to allow for pumping <br /> 5-6 <br />