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proposed Bleeder Shaft pad area is less than natural settleable solids concentrations for runoff from undisturbed lands,
<br />riven similar conditions.
<br />The upgradient diversion ditches will be triangular ditches designed to safely divert the peak flow from the 10 -year, 24-
<br />hour stone with a mininuun of 1 -foot of freeboard and located as shown on Figure 1, Bleeder Shaft Pad SAE. The
<br />shaft pad will be constructed such that it slopes toward the gravel filter. The check dam and grass filter efficiency was
<br />modeled using the SEDCADTM4 check dam and grass filter utility. Exhibit 5 is submitted to demonstrate that
<br />application of diversion ditches, drainage collection ditches, wattles, Curlex blankets, and the sump, rock check dam,
<br />and grass filter can effectively control and treat runoff from this area.
<br />6MN Mine Water Storage Reservoir and Ancillary Facilities — The 6MN Reservoir installation will include a water -
<br />supply inlet pipeline from the 10 -Right Mine Dewatering Transfer Pipeline (includes a pipeline crossing of Fish Creek);
<br />the reservoir itself (basin, embankment, emergency spillway, and outlet channel); a clean -water diversion ditch;
<br />discharge pump station, pad, and associated light -use road; discharge pipeline to the 6MN Million -Gallon Tank; and an
<br />associated topsoil stockpile. The reservoir, emergency spillway, discharge channel, and diversion channel are designed
<br />structures, with relevant design information provided in Exhibit BCC. Drainage and sediment control for the remaining
<br />components will be addressed through Alternative Sediment Controls (ASC's) and/or Best Management Practices
<br />(BMP's).
<br />As a limited and temporary disturbance, drainage and sediment control for the pipeline construction activities will be
<br />addressed through the application of a package of site-specific BMP's. Prior to initiation of pipeline construction, and
<br />as pipeline construction advances, sediment control materials (straw wattles or silt fence) will be placed downslope
<br />of the disturbance at any location where the pipeline corridor is within 50 feet of a drainage or stream buffer zone
<br />and available soil material will be removed and windrowed adjacent to the disturbance area.. Where the pipeline
<br />disturbance is not near drainages or stream buffer zones, existing natural vegetation will provide an effective
<br />vegetative filter to address any anticipated sediment control requirements. Progressive backfilling, soil
<br />replacement, and revegetation of the pipeline disturbance immediately following pipeline installation will serve to
<br />minimize any short- or long-term impacts. .Where the pipeline crosses under Fish Creek, BMP's at the crossing
<br />location will include placement of stream buffer zone markers at any point where the pipeline corridor is within 50
<br />feet of the stream buffer zone prior to any activity; completion of the work during low -flows; placement of silt
<br />fence or anchored straw bales at least 50 feet downstream to catch any sediment released prior to initiation of work;
<br />placement of sediment control materials (straw wattles or silt fence) around the entire side and near stream
<br />perimeters of the jacking pit disturbance areas; restrictions on storage or transfers of petroleum products within the
<br />buffer zone; and reclamation of the affected areas immediately following completion of pipeline installation.
<br />Construction and sediment control details are shown by the design drawings in Exhibit 490.
<br />Reservoir slopes and surfaces (out -slope and top of embankment), pad and road out -slopes, and topsoil pile will be
<br />stabilized and protected from erosion by seeding with the standard temporary stabilization seed mixture, on
<br />completion of construction. The upstream embankment of the Reservoir, emergency spillway, diversion channel,
<br />and outlet channel will all be riprapped, per the design specifications. Drainage and erosion control will be
<br />addressed on the pump pad surface and light -use road through placement of gravel surfacing materials.
<br />Supplemental drainage and sediment protection for the topsoil pile will be provided through placement of sediment
<br />control materials (straw wattles or silt fence) around the perimeter of the stockpile until an effective vegetative
<br />cover becomes established.
<br />Thickener Underflow Boreholes and Prelines (TR07-60, TR09-69, TR16-86, TR17-87, MR07-221, MR10-242,
<br />MR10-248, MR13-270, MR13-273, MR17-303) — TC has or will complete new thickener underfloor boreholes in
<br />both the SWMD and the EMD, and install new thickener Underflow pipelines to convey fine coal refuse, as a slurry,
<br />from the washplants to these locations. With the exception of the surface casings and any protective manhole structures
<br />For the Underflow boreholes, surface disturbance for the Thickener Underflow Pipelines and Borelloles will be
<br />temporary and surface activities will be limited to pipeline/borehole installation activities.
<br />The 1 MN Thickener Underflow Borehole is located to the west of the previous CYCC Office Building (Brown
<br />Palace) location, along the existing light -use road, and extends approximately 310 feet into the sealed and abandoned
<br />mine workings in the SWMD. The 6RT Thickener Underflow Borehole installation is located southeast of the
<br />intersection of Routt County Roads 27 (RCR27) and 33 (RCR33), on the north side of Foidel Creek and the
<br />TR 17-87 2.05-84.5 03/14/17
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