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<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 D.2 hrs. <br />Runoff Depth = 0.11 inch <br />Peak Discharge = 1.55 cfs (from TR-55, Figure 5-2) <br />The water bar and diversion ditch were designed using <br />N. . <br />Manning's equation for a triangular channel as. follows: <br /> <br />Design discharge <br />Manntng's n <br />Freeboard <br />Design slope <br />Design - normal depth <br />Side slope <br />Top width with freeboard <br />Depth (with freeboard) <br />Design velocity <br />= 1.6 cfs <br />= 0.03 <br />= 0.5 ft. <br />= Average 5X/Maximum 7X <br />= 0.4 ft. <br />= 3. to 1 <br />=6ft. <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 .inslope 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 7.1 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 />