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10 year, 24 hour rainfall = 1.8 inches <br />Curve Number = 70 <br />LAG = 0.066 hours (from TR-55, Figure 3.3 for a slope <br />of 38X and length of 900 ft.) <br />TC = 1.6667 LAG = 0.11 hours <br />Runoff depth (Q) _ .17 inch <br />Peak discharge (Qp) 1.81 cfs (from TR-55, Fig. 5.2) <br />The insloped diversion ditch is designed using Manning's <br />equation. for a triangular channel as follows: <br />. Design discharge 1.9 cfs <br />Manning's. n = 0.03 <br />Design slope = Road slope = 7`: <br />Design normal depth = 0.32 ft. <br />Top. width = 5 ft. <br />•Depth = 0.5 ft. <br />• A minimum 0.5 ft. inslope on road serves as freeboard <br />Side scope 5 to 1 <br />Design velocity = 3.5 ft./sec. <br />B. Sediment Control for Laydown Area <br />Two ditches are designed to collect -drainage from the laydown <br />area. These ditches are routed to a sedimentation pond at <br />the northwest corner of the laydown area. The design speci- <br />fications for the ditches and sedimentation pond follow: <br />1. A ditch will be constructed along the northern perimeter <br />of the laydown area. This ditch was designed using <br />Manning's equation for a triangular channel as follows: <br />Design discharge <br />Design slope <br />• Manning's n <br />= 2.6 c•fs <br />= S.Sx <br />= 0.03 <br />D-3 <br /> <br />