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<br />Twentymile Mine railroad spur. The 6RT Thickener Underflow Borehole extends approximately 540 feet from the
<br />surface into the sealed EMD mine workings. An existing light -use road extends approximately 250 feet from RCR33
<br />to this location. The 7RT Thickener Underflow Borehole installation will be located east of both the intersection of
<br />ROUtt County Roads 27 (RCR27) and 33 (RCR33) and the 6RT Borehole, on the north side of Foidel Creek and the
<br />Twentymile Mine railroad spur. The 7RT Thickener Underflow Borehole will extend approximately 850 feet from
<br />the surface into the sealed EMD mine workings. The 2MN Thickener Underflow Borehole installation will be located
<br />near the north edge of the existing Mine Facilities Area, between the existing Weld Shop and the Twentymile Railroad
<br />Spur and will be accessed by a short (550 feet) access road from the existing mine road. The 2MN Thickener
<br />Underflow Borehole will extend approximately 150 feet from the surface into the existing active 21VIN No. 6 Mine
<br />Entry. From this location, the coal slurry will be piped underground approximately 2,650 feet and 3,850 feet,
<br />respectively, to horizontal boreholes into the sealed 7 -Right and 8 -Right Panels in the Eastern Mining District (EMD).
<br />An additional thickener Underflow borehole will be added in the SWMD in 2016. The SWMD Thickener Underflow
<br />Borehole will be located near the Fish Creek Borehole road where it joins RCR27. Two alternate borehole locations
<br />have been identified, only one of which wil be constructed and developed. The first location 1 (in Panel 2SW) is
<br />located on the west side of RCR27 between the west entrance and the Fish Creek Borehole road, and has been selected
<br />for construction. The second location (in Panel I SW) is located on the east side of RCR27 and would be accessed
<br />from the Fish Creek Borehole road. The additional SWMD Thickener Underflow Borehole will extend from the
<br />surface into the sealed SWMD mine workings a maximum of approximately 850 feet.
<br />At each of these locations, a drill -pad and required drainage structures have been constructed. Buried thickener
<br />Underflow pipelines have been or will be installed between the existing wasllplant facilities and the thickener
<br />underflow boreholes. The locations of both the thickener Underflow boreholes and the associated pipelines are shown
<br />on the Surface Facilities and Freshwater Systems Map, Map 24 (1/4). Design information for the thickener Underflow
<br />boreholes and pipelines is provided in Exhibits 49K and 49S.
<br />Installation of the thickener Underflow boreholes involves placement of construction erosion controls (silt fence and/or
<br />straw wattles), removal and windrowing of available soil materials from pad areas and the road margins (6RT
<br />Borehole only), minor fill placement (if required) and grading to establish level drill -pads and improve the existing
<br />light -use road (6RT Borehole only), placement of gravel as surfacing for the light -use road, excavation of temporary
<br />cuttings pits on the drill -pads, drilling and casing of the boreholes, and installation of protective access manholes. On
<br />completion of drilling and casing operations, the cuttings pits are allowed to dry -out, material excavated from the pits
<br />is replaced and graded, and the pad surface is graveled to control erosion and sediment and provide an all-weather
<br />operating surface. The completed thickener underflow borehole installations include an access road, a soil material
<br />stockpile (pad and road); the drill -pad (i MN — 25 x 180 feet, 6RT- 70 x 70 feet, 7RT — 100 x 75 feet, 2MN — 75 x 75
<br />feet, I SWMD — 250 x 170 feet max.); the 6- to 12 -inch cased boreholes, 16 to 18 -inch cemented surface casings, and
<br />a covered 8 -foot diameter CMP culvert manholes with lightning protection.
<br />With timing and weather constraints, portions of the pipeline may be temporarily installed on the surface, to be
<br />buried when ground conditions are more favorable. Pipeline installation will involve removal and windrowing of
<br />soil materials from the pipeline construction corridor (maximum - 40 -foot wide); trenching in most areas;
<br />placement of suitable bedding materials; placement, connection, and pressure testing of the pipelines; backfilling
<br />and compaction of suitable fill materials around and over the pipelines; backfilling and compaction of the trench;
<br />regrading; replacement of soil materials; and revegetation of all disturbed areas. Where the pipelines pass under
<br />RCR27, the Twentymile Mine railroad spur, and Foidel Creek, the pipeline trench will be expanded to provide
<br />room for horizontal boring equipment, and the pipelines will either be trenched or bored under these features.
<br />Because pipeline placement and construction of portions of the 6RT, 7RT, 1MN, 2MN, and SWMD pads will
<br />necessarily involve activities within the Foidel Creek buffer zone, TC is requesting a temporary variance for
<br />pipeline construction and a longer-term variance for the limited pad areas from the regulatory requirements for
<br />operations within a buffer zone. The pipelines will be a double HDPE pipe system in critical areas (note that entire
<br />6RT, 7RT, 2MN, and SWMD pipelines will be double -pipe systems), with a 6 to 8- inch carrier pipe inside a larger
<br />(maximum size - 12 -inch diameter) containment pipe, buried approximately 5 -feet deep. The i MN pipeline will
<br />extend approximately 1,800 feet, with the 6RT pipeline extending approximately 8,000 feet, and continuing another
<br />1,600 feet to 7RT. The 6RT/7RT pipeline is immediately adjacent to the 2MN Borehole, so only a short connecting
<br />pipe was necessary. The SWMD pipeline will extend approximately 7,700 feet from the SWMD Borehole,
<br />TR 16-86 2.05-84.6 12/13/16
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