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<br /> <br />water bar and diversion ditch is approximately 7,3 acres. <br />Peak flows from a 10 year, 24 hour precipitation event <br />were determined using TR-55 and the following parameters: <br />10 year, 24 hour rainfall 1.8 inches <br />Curve Number 70 <br />LAG = 0.12 hours (from TR-55, <br />Figure 3.3 for a slope of 25X and length of 1200 ft.} <br />Time of Concentration (TC) = 1.667 x LAG 0.2 hrs. <br />Rvnoff Depth 0.17 inch <br />Peak Discharge 1.55 cfs (from TR-55, Figure 5-2) <br />The water bar and diversion ditch were designed using <br />Manning's equation for a triangular channel as follows: <br /> <br />Design discharge <br />Manning's n <br />Freeboard <br />Design slope <br />Design - normal depth <br />Side slope <br />Top width with freeboard <br />Depth (vfith freeboard) <br />Design velocity <br />= I.6 cfs <br />= 0.03 <br />= 0.5 ft. <br />= Average 5X/Maximum 7X <br />= 0.4 ft.. <br />= 3 to 1 <br />= 6 ft. <br />= 1.0 ft. <br />= Average 3.5 ft./sec. <br />Maximum 4.0 ft./sec. <br />2. The U.S. Steel road below the water bar will be insloped <br />with an ,ins lope ditch to divert runoff from the upslope <br />undisturbed area (Area A on Attachment B} to the Highway <br />133 drainage ditch. <br />This undisturbed area is approximately 1.1 acres. Peak <br />runoff from Area A for a 10 year, 24 hour event was <br />determined using TR-55 and the following parameters: <br /> <br />D-2 <br />