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Installation of the thickener underflow boreholes generally involves placement of construction erosion controls (silt
<br />fence and/or straw wattles), removal and windrowing of available soil materials from pad areas and the road margins,
<br />construction of designed drainage structures (ditches and rock sumps), grading to establish level drill -pads and construct
<br />or improve roads, placement of gravel as surfacing for the light -use road, excavation of temporary cuttings pits on the
<br />drill -pads, drilling and casing of the boreholes, and installation of protective access manholes. On completion of drilling
<br />and casing operations, the cuttings pits are allowed to dry -out, material excavated from the pits is replaced and graded,
<br />and the pad surface is graveled to control erosion and sediment and provide an all-weather operating surface. The
<br />completed thickener underflow borehole installations include light -use road access, one or more soil material stockpiles
<br />(pad and road); the drill -pad (1 MN — 25 x 180 feet, 6RT- 70 x 70 feet, 7RT —100 x 75 feet, 2MN — 75 x 75 feet, 2SW
<br />— 250 x 170 feet max., 1 SW — 175 x 175 feet max, Sandstone Sub — 75 x 75 feet, 12, 14, 15, 16, 17 -Left — 200 x 200
<br />feet max); the 6- to 12 -inch cased boreholes, 16 to 18 -inch cemented surface casings, and covered 8 -foot diameter CMP
<br />culvert manholes with lightning protection. The Sandstone Sub Borehole, because it will be completed on the existing
<br />substation pad, will not require soil handling, an access road, pad construction, or surface casing or a manhole, and
<br />drainage will be contained on the pad by a constructed berm.
<br />With timing and weather constraints, portions of the pipeline may be temporarily installed on the surface, to be buried
<br />when ground conditions are more favorable. Pipeline installation will involve removal and windrowing of soil
<br />materials from the pipeline construction corridor (maximum - 40 -foot wide); trenching in most areas; placement of
<br />suitable bedding materials; placement, connection, and pressure testing of the pipelines; backfilling and compaction
<br />of suitable fill materials around and over the pipelines; backfilling and compaction of the trench; regrading;
<br />replacement of soil materials; and revegetation of all disturbed areas. Where the pipelines pass under RCR27, the
<br />Twentymile Mine railroad spur, Fish Creek, and Foidel Creek, the pipeline trench will be expanded to provide room
<br />for horizontal boring or jacking equipment, and the pipelines will be trenched, bored, or jacked under these features.
<br />Because pipeline placement and/or construction of portions of the 6RT, 7RT, 1MN, 2MN, 2SW, and 12, 14, 15, 16,
<br />&17 -Left pads necessarily involved activities within the Fish Creek and Foidel Creek buffer zones, TC is requesting
<br />a temporary variance for pipeline construction and a longer-term variance for the limited pad areas from the regulatory
<br />requirements for operations within a buffer zone. The pipelines are a double HDPE pipe system in critical areas
<br />(essentially all of the more recent pipeline construction), with a 6 to 8 -inch carrier pipe inside a larger (maximum size
<br />- 12 -inch diameter) containment pipe, buried approximately 5 -feet deep. The 1MN pipeline extends approximately
<br />1,800 feet, with the 6RT pipeline extending approximately 8,000 feet and continuing another 1,600 feet to 7RT. The
<br />6RT/7RT pipeline is immediately adjacent to the 2MN Borehole, so only a short connecting pipe was necessary. The
<br />SWMD pipeline will extend approximately 6,700 feet from the 1MN TUF pipeline to the 2SW SWMD Borehole.
<br />The Sandstone Sub pipeline will extend approximately 1,200 feet from the 1MN Borehole location.
<br />A pump boost station was added at the 2SW borehole to provide sufficient pumping capacity to efficiently move the
<br />coal fines slurry through the pipeline network to all of the designated locations. In 2019 a 10' X 18' pre -fabricated
<br />master control building, an additional transformer, and an 18' X 32' addition to the pump building to house an
<br />additional pump system will be added to the pump station to assist in the pumping operations of the larger additional
<br />pipeline network. The pipeline will extend approximately 2,930 feet beyond the 2SW borehole to reach the 1 SW
<br />Borehole location. An additional pipeline (12 -Left pipeline) will tee off of the pipeline running from the 2SW
<br />borehole to the 1 SW borehole on the east side of RCR27. The pipeline will parallel RCR27 for an additional 5,800
<br />feet, extending to the northwest, crossing under Fish Creek, and then a tee will be installed to route the thickener
<br />either 1,940 feet to the 12 -Left borehole or 7,245 feet through 14, 15, andl6-Left boreholes onto the 17 -Left borehole.
<br />Electronic moisture sensors, along with pump controls, and shut-off valves provide for timely detection, shut-off, and
<br />isolation of the pipelines in the event of pipeline leakage. Access/inspection manholes and pipe -tees for the moisture
<br />detection system are located at key points along the pipeline routes.
<br />When the new Washplant and Thickener were installed, a new Thickener Overflow Sump was constructed to contain
<br />minor amounts of washdown water and to serve as a temporary catch basin for the contents of the Thickener, if
<br />required for maintenance or under upset conditions. The Thickener Overflow Sump is located between the Refuse
<br />Conveyor and Sedimentation Pond D. The Thickener Sump is partially incised, incorporates a compacted clay liner
<br />to minimize seepage, and is sized to fully contain the contents of the Washplant II Thickener (150,000 gallons) plus
<br />minor amounts of washdown water and incident precipitation for the design event. Impoundment design, operation,
<br />and maintenance information for the Thickener is provided in Exhibit 8X. Given that the potential for both the
<br />Washplant I and Washplant 11 Thickeners to experience an upset or require maintenance at the same time is negligible,
<br />with completion of the Washplant II Thickener Overflow Sump, the
<br />MR19-312 2.05-32.6 03/11/19
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