2009-11-13_PERMIT FILE - C1982056A (7)

Home Browse Search

proposed Bleeder Shaft pad area is less than natural settleable solids concentrations for runoff from undisturbed lands, given similar conditions. The upgradient diversion ditches will be triangular ditches designed to safely divert the peak flow from the 10-year, 24- hour storm with a minimum of 1-foot of freeboard and located as shown on Figure 1, Bleeder Shaft Pad SAE. The shaft pad will be constructed such that it slopes toward the gravel filter. The check dam and grass filter efficiency was modeled using the SEDCADTM4 check dam and grass filter utility. Exhibit 5 is submitted to demonstrate that application of diversion ditches, drainage collection ditches, wattles, Curlex blankets, and the sump, rock check dam, and grass filter can effectively control and treat runoff from this area. 6MN Mine Water Storage Reservoir and Ancillary Facilifies -The 6MN Reservoir installation will include awater- supply inlet pipeline from the 10-Right Mine Dewatering Transfer Pipeline (includes a pipeline crossing of Fish Creek); the reservoir itself (basin, embankment, emergency spillway, and outlet channel); aclean-water diversion ditch; discharge pump station, pad, and associated light-use road; discharge pipeline to the 6MNMihion-Gallon Tank; and an associated topsoil stockpile. The reservoir, emergency spillway, discharge channel, and diversion channel are designed structures, with relevant design information provided in Exhibit 8CC. Drainage and sediment control for the remaining components will be addressed through Alternative Sediment Controls (ABC's) and/or Best Management Practices (BMP's). As a limited and temporary disturbance, drainage and sediment control for the pipeline construction activities will be addressed through the application of a package of site-specific BMP's. Prior to initiation of pipeline construction, and as pipeline construction advances, sediment control materials (straw wattles or silt fence) will be placed downslope of the disturbance at any location where the pipeline corridor is within 50 feet of a drainage or stream buffer zone and available soil material will be removed and windrowed adjacent to the disturbance area.. Where the pipeline disturbance is not near drainages or stream buffer zones, existing natural vegetation will provide an effective vegetative filter to address any anticipated sediment control requirements. Progressive backfilling, soil replacement, and revegetation of the pipeline disturbance immediately following pipeline installation will serve to minimize any short- or long-term impacts. .Where the pipeline crosses under Fish Creek, BMP's at the crossing location will include placement of stream buffer zone markers at any point where the pipeline corridor is within 50 feet of the stream buffer zone prior to any activity; completion of the work during low-flows; placement of silt fence or anchored straw bales at least 50 feet downstream to catch any sediment released prior to initiation of work; placement of sediment control materials (straw wattles or silt fence) around the entire side and near stream perimeters of the jacking pit disturbance areas; restrictions on storage or transfers of petroleum products within the buffer zone; and reclamation of the affected areas immediately following completion of pipeline installation. Construction and sediment control details are shown by the design drawings in Exhibit 490. Reservoir slopes and surfaces (out-slope and top of embankment), pad and road out-slopes, and topsoil pile will be stabilized and protected from erosion by seeding with the standard temporary stabilization seed mixture, on completion of construction. The upstream embankment of the Reservoir, emergency spillway, diversion channel, and outlet channel will all be riprapped, per the design specifications. Drainage and erosion control will be addressed on the pump pad surface and light-use road through placement of gravel surfacing materials. Supplemental drainage and sediment protection for the topsoil pile will be provided through placement of sediment control materials (straw wattles or silt fence) around the perimeter of the stockpile until an effective vegetative cover becomes established. Thickener Underflow Pipelines and Borehole (TR07-60. MR07-221) -With the exceptions of the surface casing for the Underflow Borehole and any intermediate access manhole(s), surface disturbance for the Thickener Underflow Pipelines and Borehole will be temporary and surface activities will be limited to pipeline/borehole installation activities. During construction, and for the minor surface structures, drainage and sediment control will be provided by Alternative Sediment Controls (ABC's) consisting of combined Best Management Practice (BMP) measures. Construction-related surface disturbance will be limited to soil removal and windrowing from the pipeline trench alignment and borehole pad area, excavation of the trench and temporary stockpiling of excavated material adjacent to the trench, and excavation of temporary pits (within existing disturbance areas) for pipeline boring or jacking operations under the Foidel Creek culvert crossing and railroad spur. Following installation of appropriate ABC's for each portion of the project disturbance, available soil materials will be bladed from any new disturbance areas and temporarily windrowed on the upgradient edge of the disturbance area. TR09-66 2.05-84.5 04/11/09