2018-01-29_PERMIT FILE - C1982056A

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well as possible future system expansion. The Refuse Conveyor is supported by two steel support bents, and utilizes the typical conveyor construction. The conveyor bents set on reinforced concrete caissons, as previously described. The Refuse Bin is a steel frame building (30 x 30 x 50 feet high) with steel siding and roof which supports a 200-ton pre-fabricated steel surge bin and contains minor chute-work and a dust collection system. The Refuse Bin sets on a reinforced concrete slab floor. The Washplant II Thickener, which is used to partially dewater the fine coal refuse, is a reinforced concrete tank approximately 50 feet in diameter, and 12 feet high. A flocculating agent is introduced into the tank, and a high- efficiency underflow system mixes the flocculant with the fine refuse stream, causing the refuse particles to agglomerate and settle from suspension. The decant water discharges through a filter and is recycled to the Washplant. The fine coal refuse slurry normally discharges through double walled discharge lines connecting to drop-boreholes and underground piping system in the SWMD, WMD or the EMD, and carry the slurry to areas of sealed underground mine workings. Underground, water decants from the fine refuse slurry, and flows downgradient to sumps where a pumping system is used to recover and recycle the water. In order to address emergency mine dewatering requirements, slurry may be temporarily diverted to an incised basin within the Area 1 Pit permitted mine refuse disposal area, with decant of clarified water to the Area 1 Pit Mine Water Storage Reservoir. Coal fines that accumulate in this temporary basin will be allowed to dry-out and will then be transferred to the permanent Coal Refuse Disposal area. TC has completed or will complete thickener underflow boreholes in the SWMD, WMD, and the EMD, and thickener underflow pipelines to convey fine coal refuse,as a slurry,from the washplants to these locations. The 1MN Thickener Underflow Borehole is located to the west of the previous CYCC Office Building (Brown Palace) location, along the existing light-use road, and extends approximately 310 feet into the sealed and abandoned mine workings in the SWMD. The 6RT Thickener Underflow Borehole installation is located southeast of the intersection of Routt County Roads 27 (RCR27) and 33 (RCR33), on the north side of Foidel Creek and the Twentymile Mine railroad spur. The Thickener Underflow Borehole extends approximately 540 from the surface into the sealed EMD mine workings. An existing light-use road extends approximately 250 feet from RCR33 to this location. The 7RT Thickener Underflow Borehole installation is located east of both the intersection of Routt County Roads 27 (RCR27) and 33 (RCR33) and the 6RT Borehole, on the north side of Foidel Creek and the Twentymile Mine railroad spur. The 7RT Thickener Underflow Borehole will extend approximately 850 feet from the surface into the sealed EMD mine workings. The 2MN Thickener Underflow Borehole installation is located near the north edge of the existing Mine Facilities Area, between the existing Weld Shop and the Twentymile Railroad Spur and is accessed by a short (550 feet) access road from the existing mine road. The 2MN Thickener Underflow Borehole extends approximately 150 feet from the surface into the existing active 2MN No. 6 Mine Entry. From this location, the coal slurry is piped underground approximately 2,650 feet and 3,850 feet, respectively, to horizontal boreholes into the sealed 7-Right and 8-Right Panels in the Eastern Mining District(EMD). An additional thickener underflow borehole will be added in the WMD in 2017. The 12-Left Thickener Underflow Borehole will be located off RCR27 just east of the intersection with County Road 37 on the north side of the road. The borehole will extend into the WMD mine workings approximately 1,260 feet in the 12 Left Inby Panel. Three additional thickener underflow boreholes will be added in the SWMD in 2016 and 2017. The first SWMD Thickener Underflow Borehole will be located near the Fish Creek Borehole road where it joins RCR27. Two alternate borehole locations have been identified, only one of which will be initially constructed and developed. The first location 1 (in Panel 2SW) is located on the west side of RCR27 between the west entrance and the Fish Creek Borehole road, and has been selected for construction through TR16-86. The second location (in Panel 1SW) is located on the east side of RCR27 and will be accessed from the Fish Creek Borehole road this location was an alternative and will not be constructed at this time but may be a potential site in the future. The SWMD Thickener Underflow Borehole in 2SW will extend from the surface into the sealed SWMD mine workings a maximum of approximately 750 feet. TC also plans a test borehole (Sandstone Sub Test Borehole) to evaluate conditions in the 3SW Gateroad (WMD) for a future thickener underflow borehole. The test hole will be located on the existing Sandstone Substation pad, and will be directionally drilled to intersect the 3SW Gateroad at a depth of approximately 420-feet. If conditions in this area are favorable, TC will convert the test borehole to a thickener underflow borehole, which will involve boring the test hole out to 22 to 24 inches for the surface casing and 12 to 15 inches for the finished borehole, setting and cementing a 16 to 18 inch surface casing to a depth of approximately 60 feet, setting and cementing a 8 to 11 inch borehole casing to a depth of approximately 420 feet, and setting an 8-foot covered TR17-88 2.05-32.4 06/10/17