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Underground grit screen. Mid-Continent proposes the <br /> addition of a grit screen, to be located underground in <br /> the tunnel , which separates larger coarse solids prior <br /> to the flow leaving the tunnel. <br /> We estimate that the screen will remove approximately one <br /> fourth to one third of the solids from the flow. These <br /> solids will be carried or conveyed to the raw coal <br /> stockpile. <br /> The addition of the grit screen will reduce the volume <br /> of solids in the flow which reports either to the 016 <br /> ponds or the water treatment plant. <br /> - Water treatment plant system. Mine drainage, on leaving <br /> the mine, flows through a concrete basin which contains <br /> diverter valves (valve box) to allow switching of flow <br /> to either the 016 ponds or to the new treatment facility <br /> in the Preparation Plant. <br /> - A 6,000' long polyethelene pipe carries water from the <br /> valve box to the preparation plant, a descent in <br /> elevation of approximately 5251 . The water gravity flows <br /> through the pipe and into the plant. <br /> The mine drainage flows from the pipe into a recycle <br /> sump, from which underflow reports to the hydroclone. <br /> The 36-inch diameter hydroclone system separates <br /> middlings coal solids. The middling solids removed by <br /> the hydroclone ( i .e. the underf low) go into the coal wash <br /> plant cycle, in which coal is separated from non-coal <br /> refuse. The coal is sold, the refuse is conveyed to the <br /> refuse disposal area. <br /> The variable flow of the mine drainage is leveled out in <br /> a recycle sump, which consists of a tank and pump, to <br /> provide a constant flow of about 600 gpm to the <br /> hydroclone inlet. <br /> The overflow (vortex) from the hydroclone discharges back <br /> to the recycle sump. Surplus water (i .e. , not required <br /> to maintain the constant rate of flow to the hydroclone) <br /> which contains very fine ( -200 mesh) solids overflows <br /> the sump and then goes to another tank for flocculation. <br /> Flocculant is added to the flow in a dosage of 10 ppm or <br /> less, metered automatically according to flow. MRL-100 <br /> (guar gum) will be used as the flocculant. <br /> The flocculant is stored in a 1,000 gal. tank, then <br /> 3 <br />