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• Channel Designs The surface water diversion dimensions were determined using Mannings Equation for open channel flow. All channels will be either gravel- or vegetated-lined channels. If flow velocities exceed 6 feet per second, the channels will be lined wixh riprap or erosion will be controlled with the use of rock check dams. Channels will be designed with a 0.3 foot freeboard. For channels where rock check dams or straw bales are installed, a 1 foot freeboazd was added to the design depth. The Elk Creek postmine channel will also be designed with a 7 foot freeboard. Riprap sizes were determined using Pader, OSM or limiting velocity methods. Given the uncertainty in determining riprap sizes for steep grades, a factor of safety of 3 inches was added to the riprap Dsn designed using the Pader method. The limiting velocities were determined from the "Erosion and Sediment Pollution Control Program Manual", Bureau of Land and Water Conservation, Pennsylvania. The limiting velocities aze shown in the channel design section. The Elk Creek channel was designed using the Simons/OSM method which includes abuilt-in factor-of-safety. Rpprap will consist of durable rock, resistant to weathering, with a uniform gradation. This section contains design calculations for the following ditches: Elk Creek Mine D-Seam Portal and Coal Refuse Facility Ditches Yard Ditches 1 and 2 Berm Ditch Refuse Ditches Haul Road Ditch Conveyor IA Ditch East Clean Water Ditch West Refuse Pile Diversion West Refuse Ditch East Refuse Ditch Elk Creek Mine Ditches Dl, D2, D3 Upper, D3 Lower, D4, DS Upper, DS Middle, DS Lower, DG, D7, DS Upper & D8 Lower. IIW-2, I1W HR Upper, lIW HR Lower, IIW Clean Water Diversion, Bench Channel In addition, this section contains the design calculation for the following postmine temporary and permanent ditches and channels: . Substation 3 Channels SS-1, SS-2, SS-3, & SS-4 TR-43 Revised September 2003