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JAN-16-'91 WED 112: 11 I�� ,JRX TECHNOLM I ES TEL NO:438 7�ij #498 P19 <br /> SYSTEM DESIGN <br /> The vapor extraction system will extract vapor from the soil and reduce <br /> the concentration of hydrocarbons in the vapor to allow for discharge of <br /> the extracted air stream to the atmosphere, <br /> Temporary Vapor Extraction Probes and Existing Groundwater <br /> Monitoring Wells <br /> Six temporary vapor extraction probes will be driven pneumatically into <br /> the soil at the locations specified on Figure 3. The perforations in the <br /> probes will be located at a depth of 20 to 35 feet below grade. <br /> Groundwater monitoring wells MW-3 and MW-4 will be incorporated into the <br /> remediation system, <br /> The temporary vapor extraction probes and groundwater monitoring wells <br /> will serve as extraction points. A vacuum will be applied to an <br /> extraction point to volatilize hydrocarbon products in the soil . The <br /> soil gas will flow from the soil through the perforations in the probes <br /> or the slotted screening its the extraction wells. The effective capture <br /> radii expected from the temporary vapor extraction probes and groundwater <br /> monitoring wells (vapor extraction wells) are given in Figures 4 and 5, <br /> respectively. <br /> Trenching and Piping <br /> The extracted soil gases will be transported through underground piping. <br /> Soil gases will be extracted from the probes and wells to a manifold, <br /> then from the manifold to the system equipment. The system underground <br /> Piping will be installed in shallow trenches and avoid existing <br /> utilities, <br /> Manifold <br /> The manifold box consists of 10 valves and sampling ports that control <br /> individual extraction points. The valves located in the manifold box <br /> will he either open or closed, depending on whether an extraction point <br /> is to be utilized. This will ex edite the remedial effort and minimize <br /> the cost per pound of hydrocarbon a atement, <br /> Equipment <br /> The system equipment will include a pumping unit, a catalytic <br /> Incinerator, and an accumulator/water knockout. The system equipment <br /> will be located at the northeast corner of the former station building <br /> (Figure 3) . Extracted soil gas will be fed to the catalytic incinerator <br /> for abatement by an electrically driven pumping unit. The extracted air <br /> stream will first enter a pre-heat section that contains a gas burner. <br /> - 15 - <br />