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The Washplant Feed Conveyor discharges to a surge bin, with water added at the transfer point. Feeders draw from
<br />the surge bin to feed the coal to a series of screens, heavy -media cyclones (using a slurry of magnetite and water to
<br />separate the coal from the heavier refuse material), classifying cyclones, wash screens, and centrifuges, producing
<br />both a coarse and fine coal product, which are combined and discharge to the Overland Conveyor. Coal refuse is
<br />separated from the coal stream in the cyclones, with the coarse refuse passing over screens to drain and then to the
<br />Coal Refuse Conveyor, and the fine refuse being transferred to the Thickener to reduce water content. The
<br />Washplant will require approximately 600 gpm of make -up water, to address losses to the coal product, coarse
<br />refuse, and fine refuse streams (note that most of the water from the fine refuse stream is recovered and recycled to
<br />the Mine water supply system, which include the washplant feed water). The coal preparation circuit also includes
<br />the magnetite recovery and recycling system, and a water filtration and recycle system, to minimize water use
<br />requirements. The coal preparation equipment, along with associated chute -work, and control and monitoring
<br />systems, are housed in the Washplant Building, a steel frame building with steel siding and roof (55 x 125 x 80 feet
<br />high), which sets directly over the Overland Conveyor. The building sets on a reinforced concrete slab (58 x 128 x
<br />1 foot thick).
<br />The Coal Refuse Conveyor (48 -inch belt w /500 tph capacity), transfers coarse coal refuse from the Washplant to a
<br />Refuse Bin. The Refuse Bin is used to load trucks, which haul the coal refuse material to the existing permitted
<br />Coal Refuse Disposal area. The Coal Refuse Conveyor is designed to handle current requirements of 500 tph, as
<br />well as possible future system expansion. The Refuse Conveyor is supported by two steel support bents, and
<br />utilizes the typical conveyor construction. The conveyor bents set on reinforced concrete caissons, as previously
<br />described. The Refuse Bin is a steel frame building (30 x 30 x 50 feet high) with steel siding and roof which
<br />supports a 200 -ton pre- fabricated steel surge bin and contains minor chute -work and a dust collection system. The
<br />Refuse Bin sets on a reinforced concrete slab floor.
<br />The Washplant II Thickener, which is used to partially dewater the fine coal refuse, is a reinforced concrete tank
<br />approximately 50 feet in diameter, and 12 feet high. A flocculating agent is introduced into the tank, and a high -
<br />efficiency underflow system mixes the flocculant with the fine refuse stream, causing the refuse particles to
<br />• agglomerate and settle from suspension. The decant water discharges through a filter and is recycled to the
<br />Washplant. The fine coal refuse slurry normally discharges through either an 1,800 -foot, 6 -inch diameter discharge
<br />line (SWMD), or an 8,000 foot 6 -inch pipeline (EMD) connecting to 8 -inch drop- boreholes and associated
<br />underground piping systems, which carries the slurry to areas of sealed underground mine workings. Underground,
<br />water decants from the fine refuse slurry and flows downgradient to sumps where a pumping system is used to
<br />recover and recycle the water. In order to address emergency mine dewatering requirements, slurry may be
<br />temporarily diverted to an incised basin within the Area 1 Pit permitted mine refuse disposal area, with decant of
<br />clarified water to the Area 1 Pit Mine Water Storage Reservoir. Coal fines that accumulate in this temporary basin
<br />will be allowed to dry -out and will then be transferred to the permanent Coal Refuse Disposal area.
<br />When the new Washplant and Thickener were installed, a new Thickener Overflow Sump was constructed to
<br />contain minor amounts of washdown water and to serve as a temporary catch basin for the contents of the
<br />Thickener, if required for maintenance or under upset conditions. The Thickener Overflow Sump is located
<br />between the Refuse Conveyor and Sedimentation Pond D. The Thickener Sump is partially incised, incorporates a
<br />compacted clay liner to minimize seepage, and is sized to fully contain the contents of the Washplant II Thickener
<br />(150,000 gallons) plus minor amounts of washdown water and incident precipitation for the design event.
<br />Impoundment design, operation, and maintenance information for the Thickener is provided in Exhibit 8X. Given
<br />that the potential for both the Washplant I and Washplant II Thickeners to experience an upset or require
<br />maintenance at the same time is negligible, with completion of the Washplant II Thickener Overflow Sump, the
<br />Washplant I Thickener Overflow Sump was decommissioned, filled -in and replaced by a discharge pipe from the
<br />Washplant I Thickener to the new Washplant II Thickener Overflow Sump. As an incised and closed basin (ie: no
<br />outlet) the only potential inputs to the Sump are thickener overflow, washdown water, or minor incident
<br />precipitation, which are subsequently pumped back into the system by a portable floating pump installation. The 4-
<br />inch thickener overflow line has been extended to the new Thickener Overflow Sump (4,800 feet), allowing
<br />overflow from either thickener to be controlled by valves and routed to the Sump. Water level in the Sump is
<br />• monitored and managed as part of the ongoing Washplant operations.
<br />Given the power and system control requirements for the Washplant, an associated Motor Control Center
<br />(MCC) /Office Building was constructed immediately adjacent to the Washplant. The MCC /Office Building houses
<br />electrical, control, and monitoring equipment for the Washplant and includes office space.
<br />MR 10 -243 2.05 -32.3 05/31/10
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