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Chapter IV <br /> • <br /> 9. Mine Drainage Treatment System <br /> Water drains from the mine through a pipe in one bore of the <br /> adit/rock tunnel. The mine drainage water is treated to ensure <br /> water quality standards are met when the water discharges into <br /> surface receiving streams. Water treatment is done by mechanical <br /> means, settling and flocculation, as follows. <br /> Underground Sizing Screen <br /> The mine drainage is routed through a sizing screen which is <br /> located underground, in the tunnel. The function of the screen is <br /> to remove coarse solids from the water, which then continues to <br /> drain through the pipe and out the tunnel. <br /> Mine Water Treatment Plant <br /> The mine water flows through a valve box which is situated in the <br /> tunnel portal yard area, near the lamphouse. Flows are routed at <br /> the valve box between the ditch leading to the 016 pond(s) , and the <br /> pipeline leading to the water treatment plant which is located in <br /> the coal preparation plant structure. <br /> • The pipeline extends from the portal yard valve box down to the <br /> preparation plant. Water is conveyed through the pipe into the <br /> plant to the recycle sump/hydroclone of the mine water treatment <br /> plant. <br /> The function of the recycle sump/hydroclone is to separate middling <br /> solids from the flow. The solids, contained in the underflow, <br /> report to the coal preparation plant, or to the 001 sediment ponds <br /> Overflow from the recycle sump/hydroclone proceeds to the mixing <br /> tank for flocculation, and then flows out of the plant, through a <br /> pipeline to the 020 pond for "finishing" prior to discharge into <br /> Coal Creek. In the alternative, some or all of the overflow may be <br /> routed to the 001 ponds for "finishing. " <br /> Settling Ponds <br /> As an alternative to, or in combination with the water treatment <br /> plant, flows are routed at the valve box to the 016 pond series for <br /> settling of solids prior to discharge to Dutch Creek. <br /> A total of eight ponds, at three outfalls, can be utilized for <br /> settling of solids from the mine drainage water. These include the <br /> three pond series at Outfall 016, known as the "tunnel ponds"; the <br /> • pond at Outfall 020, known as the "picnic pond" ; and the four pond <br /> 25(a) <br />