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and the Twentymile Mine railroad spur. The Thickener Underflow Borehole will extend approximately 540 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. At both locations, a drill -pad and required drainage structures will be constructed. Buried thickener
<br />underflow pipelines will be installed between the existing washplant facilities and the two thickener underflow
<br />boreholes. The locations of both the thickener underflow boreholes and the associated pipelines are shown on the
<br />Surface Facilities and Freshwater Systems Map, Map 24 (1/4).
<br />Installation of the thickener underflow boreholes will involve placement of construction erosion controls (silt fence
<br />and/or straw wattles), removal and windrowing of available soil materials from pad areas and the road margins (6RT
<br />Borehole only), grading to establish level drill -pads and improve the existing light -use road (6Rt Borehole only),
<br />placement of gravel as surfacing for the light -use road, excavation of temporary cuttings pits on the drill -pads, drilling
<br />and casing of the boreholes, and installation of protective access manholes. On completion of drilling and casing
<br />operations, the cuttings pits will be allowed to dry -out, material excavated from the pits will be replaced and graded,
<br />and the pad surface will be graveled to control erosion and sediment and provide an all- weather operating surface.
<br />The completed thickener underflow borehole installations will include the light -use road (6RT only), a soil material
<br />stockpile (pad and road); the drill -pad (1MN — 25 x 180 feet, 6RT- 70 x 70 feet); the 6 -inch cased boreholes, 14 -inch
<br />cemented surface casings, a covered 8 -foot diameter CMP culvert manholes with lightening protection, and a
<br />downgradient containment berm.
<br />Pipeline installation will involve removal and windrowing of soil materials from the pipeline construction corridor
<br />(maximum - 40 -foot wide); trenching in most areas; placement of suitable bedding materials; placement,
<br />connection, and pressure testing of the pipelines; backfilling and compaction of suitable fill materials around and
<br />over the pipelines; backfilling and compaction of the trench; regrading; replacement of soil materials; and
<br />revegetation of all disturbed areas. Where the pipelines pass under RCR27, the Twentymile Mine railroad spur,
<br />and Foidel Creek, the pipeline trench will be expanded to provide room for horizontal boring equipment, and the
<br />pipelines will be bored under these features. Because pipeline placement will necessarily involve activities within
<br />the Foidel Creek buffer zone, TCC is requesting a temporary variance from the regulatory requirements for
<br />operations within a buffer zone. The pipelines will be a double HDPE pipe system in critical areas, with a 6 to fl-
<br />inch carrier pipe inside a larger (maximum size — 12.75 -inch diameter) containment pipe, buried approximately 5-
<br />feet deep.
<br />In order to address a temporary emergency situation, the 6RT Pipeline may initially be placed on the surface, with a
<br />temporary culvert crossing (between railroad ties) of the UP Rail Spur. The UP will remove a single tie, excavate
<br />the ballast material, and TC's contractor will place the culvert, and dual pipeline at the crossing location. The UP
<br />will then replace the ballast and any additional fill material required. All work will occur within the existing UP
<br />right -of -way, under UP's supervision. Generally, the temporary surface location of the pipeline will follow the
<br />previously approval pipeline alignment, with the exception of a short segment from the rail crossing location, which
<br />will run parallel to the track under the RCR27 overpass and then follow the RCR27 road embankment to a location
<br />just west of the 6RT Borehole, where it will turn back to connect to the borehole. The surface pipeline will be the
<br />same pipeline previously permitted, with an inner slurry pipe of welded HDPE, and a larger containment pipeline.
<br />As an additional protective measure, TC will walk the pipeline once a shift to verify pipeline integrity, and will
<br />continuously monitor flow discharge at the 6RT Borehole location. Once UPRR approvals are received for boring
<br />the pipeline under the rail spur, and this work is completed, the temporary pipeline connection will be eliminated,
<br />and the previously permitted pipeline will be completed and buried.
<br />The 1MN pipeline will extend approximately 1,800 feet, with the 6RT pipeline extending approximately 8,000 feet.
<br />Electronic moisture sensors, along with pump controls, and shut -off valves will provide for timely detection, shut -off,
<br />and isolation of the pipeline in the event of pipeline leakage. Access /inspection manholes and pipe -tees for the
<br />moisture detection system will be located at key points along the pipeline routes.
<br />During construction, and for the minor surface structures that will remain during mining, drainage and sediment control
<br />will be provided by Alternative Sediment Controls (ASC's) consisting of combined Best Management Practice (BMP)
<br />measures. BMP's for the construction activities include:
<br />Minimizing the area of surface disturbance
<br />Scheduling of construction activities during the dry summer or early winter periods
<br />TR09 -69 2.05 -84.6 10/23/09
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