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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 38% 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 T,R-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. ins lope on road serves as freeboard <br />Side slope = 5 to i <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 carner.of the laydown area. The design spec i- <br />fications for the ditches and sedimentation pond fallow: <br />1. A ditch will be constructed along the northern perimeter <br />of the laydown area. This ditch was designed using <br />Manninq's equation for a triangular channel as follows: <br />Design discharge = 2.6 cfs <br />• Design slope 5.5% <br />Manning's n 0.03 <br />D-3 <br />