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Peabody does not anticipate any other inflow to the pond at this time. The principal spillway will be noncloggin9 and will automatically deuater the ponding area to maintain the design capacity for the runoff volume for a 10-year, 24-hour storm event. Any additional dewatering required will be done by transporting the water to another pond for treatment, or discharging the water according to the approved Colorado NPDES permit. Spillways This sediment pond will have two separate spillways; a principal and an emergency. Please see Exhibit 13-5 for location of spillways. The principal spillway will consist of a 24-inch diameter drop inlet corrugated metal pipe ((.MP) with a trash rack at the inlet. This pipe will keep the pond level a[ the 6872.1 elevation. Maximum estimated elevation (peak stage) above the principal spillway with [he passage at the 10-year, 24-hour even[ will be 6873.0, [his leaves 1.0 feet to the emergency spillway. The embankment portion of the emergency spillway will consist of a trapezoidal channel as shown on Exhibit 13-5. Assuming the principal spillway was plugged, the trapezoidal channel could safely pass the runoff volume from the 25-year and 100-year, 24-hour storm. The emergency spillway outflow channel will consist of a vegetated, trapezoidal channel. In order to prof ec[ the channel, in the unlikely event of a discharge prior to vegetation establishment, the channel will be mechanically stabilized. This will be conducted in the following manner. The channel wilt be shaped to the design geometry (see Table 13-3-72). The channel will then be seeded with a combination of intermediate wheatgrass, tall fescue and basin wildry e. This seed mix will provide the long term erosion control. In order [o provide erosional stability prior to vegetation establishment, a product called Landstrand will be applied to the seeded area. Landstrand roving fibers are continuous fibrilated polypropylene strands applied with the aid of an air compressor and applicator gun at a rate of 0.25 to 0.35 l6s/sy. These fibers are then tacked together and to the surface by spraying pine tar (Road Oyl) on the fibers. Tests conducted on Landstrand/Road Oyl indicate that the application, prior to vegetation establishment, can withstand velocities up to 9 FPS. The channel was designed with the aid of the SEDCADa computer program. The outflow channel from Pond 005 was designed [o safely pass the flow from a 100-year, 24-hour precipitation event, plus the floe from the same storm in the 131.20-acre watershed above the pond. This combination diversion ditch and spillway is designated Diversion No. 7 and O can be found in Attachment 13-2. The closest vegetation type listed in SEDCAD+ resembling 13-3-12 Revised 03/13/92