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sump is being install between the new tank and Pond D. This will allow the TC staff to control the sediment
<br />on a more manageable level and reduce the amount of sediment that enters into Pond D.
<br />As part of the design process, four soil borings were completed for design of the foundation structures for the major
<br />Washplant facilities (refer to Washplant II Foundation Design Report in Exhibit 25). Site backfill and grading
<br />work for Washplant II involved removal of potentially unsuitable soil materials, ripping and scarification of the
<br />entire washplant pad area, cut and fill grading, and controlled placement and compaction. Cut volumes were
<br />approximately 24,000 cy, and approximately 12,000 cy of suitable fill and 10,000 cy of graded rock material were
<br />placed and compacted, consistent with the foundation design recommendations. Backfilled and compacted pad
<br />areas were then graded to direct surface runoff flows to the designed drainage and sediment control structures, and
<br />(except for building foundation areas) graveled to control erosion, dust, and surface drainage. Graveled areas will
<br />be utilized as yard -area driveways for equipment and operations/maintenance access to the Crushing/Screening
<br />Building, Washplant, thickener, and Refuse Bin. Based on the foundation design recommendations, reinforced
<br />concrete caissons were poured to support building foundations and conveyor supports. Reinforced concrete floor
<br />slabs and grade walls were then formed and poured to connect to the concrete caisson support system.
<br />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 upwards of 1000 gpm of make-up water, to address losses to the coal product, coarse refuse,
<br />and fine refuse streams (note that most of the water from the fine refuse stream is recovered and recycled to the
<br />Mine water supply system, which include the washplant feed water). The coal preparation circuit also includes the
<br />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 Tanks, which are used to partially dewater the fine coal refuse, are reinforced concrete
<br />tanks approximately 50 feet in diameter, and 12 feet high (older tank) and 90 feet in diameter, and 14 feet high
<br />(new tank).. A flocculating agent is introduced into the tanks, and a high -efficiency underflow system mixes the
<br />flocculant with the fine refuse stream, causing the refuse particles to agglomerate and settle from suspension. The
<br />decant water discharges through a filter and is recycled to the Washplant. The fine coal refuse slurry discharges
<br />through a HDPE double walled pipeline network where it is then dropped down boreholes which carry the slurry to
<br />areas of sealed underground mine workings. Underground, water decants from the fine refuse slurry and flows
<br />downgradient to sumps where a pumping system is used to recover and recycle the water. In order to address
<br />emergency mine dewatering requirements, slurry may be temporarily diverted to an incised basin within the Area 1
<br />Pit permitted mine refuse disposal area, with decant of clarified water to the Area 1 Pit Mine Water Storage
<br />Reservoir. Coal fines that accumulate in this temporary basin will be allowed to dry -out and will then be
<br />transferred to the permanent Coal Refuse Disposal area.
<br />TC has completed or will complete thickener underflow boreholes in the SWMD, WMD, and the EMD, and thickener
<br />underflow pipelines to convey fine coal refuse, as a slurry, from the washplants to these locations. The 1MN Thickener
<br />Underflow Borehole is located to the west of the previous CYCC Office Building (Brown Palace) location, along the
<br />existing light -use road, and extends approximately 310 feet into the sealed and abandoned mine workings in the
<br />TRIS -91 2.05-32.4 08/20/18
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