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Channel Designs <br />The surface water diversion dimensions were determined using Mannings Equation for open channel flow. All <br />channels will be either gravel- or vegetated-lined channels. If flow velocities exceed 6 feet per second, the channels <br />will be lined with riprap or erosion will be controlled with the use of rock check dams. Channels will be designed <br />with a 0.3 foot freeboard. For channels where rock check dams or straw bales are installed, a 1 foot freeboard was <br />added to the design depth. A 1 foot freeboard will also be added to the Elk Creek postmine channel and Bear <br />Creek Main postmine channel. 12iprap sizes were determined using Pader, OSM or limiting velocity methods. <br />Given the uncertainty in determining riprap sizes for steep grades, a factor of safety of 3 inches was added to the <br />riprap DS„ designed using the Pader method. The limiting velocities were determined from the "Erosion and <br />Sediment Pollution Control Program Manual", Bureau of Land and VG'ater Conservation, Pennsylvania. The <br />limiting velocities are shown in the channel design section. The Elk Creek channel was designed using the <br />Simons/OSM method, which includes abuilt-in factor-of-safety. Riprap will consist of durable rock resistant to <br />weathering with a uniform gradation. <br />This section contains design calculations for the following ditches: <br />Elk Creek Mine and D-Seam Portal Ditches <br />Yard Ditches 1 and 2 <br />Berm Ditch <br />Refuse Ditches <br />Haul Road Ditch <br />Conveyor 1A Ditch <br />East Clean Water Ditch <br />West Refuse Pile Diversion <br />West Refuse Ditch <br />East Refuse Ditch <br />Elk Creek Mine Ditches D1, D2, D3 Upper, D3 Lower, D4, D5 Upper, D5 Middle, <br />DS Lower, D6, D7, D8 Upper & DS Lower, D9 and D10. <br />Topsoil Pile Downdrain <br />Hubbard Creek Fansite Ditches HCD-1, HCD-2, HCD-4 <br />Bear Creek Fansite Main Ditch BCCD-1 <br />Bear Creek Fansite Steep Ditch BCCD-2 <br />In addition, this section contains the design calculation for the following postmine temporary and permanent <br />ditches and channels: <br />