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Groundwater from the extraction wells may be conveyed to an equalization tank located <br /> near the site entrance. Pumping from the influent equalization tank to the passive air- <br /> stripper will be controlled by high/low float controls. The influent transfer pump will thus <br /> maintain influent flow at a pre-set rate. <br /> Water in the equalization tank will then be pumped into a 24-inch diameter corrugated <br /> HDPE pipe that will serve as a passive air stripper. Since the air stripper's efficiency is <br /> controlled by the "air-to-water" ratio parameter, typically of between 25 to 1 and 75 to 1, <br /> the amount of air flowing though the passive air stripper unit pipeline controls the volume of <br /> groundwater that can be treated. The proposed passive air stripper would include a 500- <br /> foot long corrugated HDPE pipe extending from the water supply well to the bottom of the <br /> stormwater retention pond where the treated water would be discharged. Groundwater <br /> will enter the top of the pipe and will be agitated and stripped of VOCs by air mixing with <br /> water as it cascades down the pipe before it is discharged to the basin. The CHSL air stripper <br /> may also utilize vapor phase GAC to meet air quality standards (Table 12A). <br /> The cost to construct this system would be approximately $605,340 (Table 1213), and annual <br /> 0&M costs are expected to be $120,530 (Table 12C). <br /> 4.5.3 Alternative No. 6B-Groundwater Extraction -GAC <br /> The GAC treatment alternative includes the following components: <br /> Influent equalization tank <br /> • Influent transfer pumps <br /> • Pre-Filtration system <br /> • GAC vessels <br /> • Effluent surge tank <br /> Influent equalization is necessary to maintain a steady flow through the GAC vessels and to <br /> achieve effective adsorption efficiency throughout the carbon bed. The influent transfer <br /> pump will be controlled by high/low level switches in the influent tank and, when operating, <br /> will maintain a constant flow rate to the treatment system. Standby transfer pumps will be <br /> provided for redundancy. Considering the small volumes of water that are expected for <br /> treatment, two vessels with a combined capacity of 20 gpm should be adequate for the <br /> project. Since the vessels are modular, if necessary, the system could be expanded at a later <br /> time. <br /> Engineering Feasibility Study Geo-I.og�c Page ■ 27 <br /> Corral Hollow Sanitary Landfill w s s o c I Ar c s <br /> January 25,2013 <br />