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4 <br /> solids will be removed from the flow. These solids <br /> will then go to the raw coal storage area. <br /> Mine drainage then flows through a concrete basin <br /> which contains diverter valves (valve box) to allow <br /> switching of flow to either the 016 ponds or to the <br /> new treatment facility in the Preparation Plant. <br /> A 6,000' long polyethelene pipe carries water from <br /> the valve box to the preparation plant, a descent <br /> of approximately 5251 . The water gravity flows <br /> through the pipe and into the plant. <br /> The mine drainage flows into a 20-inch diameter <br /> hydroclone system which separates middlings coal <br /> solids (-35 to +200 mesh) . The variable flow from <br /> the mine drainage is leveled out in a recycle tank <br /> and pump to provide a constant flow of about 600 gpm <br /> to the hydroclone inlet. <br /> The overflow (hydroclone vortex) discharges to the <br /> recycle sump. Surplus water (i.e. , not required to <br /> maintain the constant rate of flow to the <br /> hydroclone) which contains very fine ( -200 mesh) <br /> solids reports to the flocculation tank. <br /> Flocculant is added to the flow in a flocculation <br /> tank in a dosage of 10 ppm or less. Bench scale <br /> flocculation and clarification tests have been <br /> performed to evaluate the treatment efficiency of <br /> several flocculants. <br /> - The tank is located in an upper story of the <br /> preparation plant. A pipe extends from the tank, <br /> out of the plant, to convey the flow (by gravity) <br /> to the existing 020 sediment pond, about 650 feet <br /> west of the wash plant. The pond is used as a <br /> "finishing" or clarification pond for the -200 mesh <br /> solids. <br /> Pond effluent containing less than 35 ppm flows out <br /> of the pond, at the opposite end of the infeed, <br /> through a pipe to Coal Creek. In the pond, settled <br /> solids accumulate at a pulp density of about 20%. <br /> Based on flow and solids data from a recent 12-month <br /> period, settled solids would rise about 6 feet every <br /> two years. <br /> A sludge pump installed in the pond is used to pump <br /> the 20% pulp to the wash plant (or directly to the <br /> refuse conveyor) . This can be accomplished without <br /> 3 <br />