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• <br />Selection of Ditch Size <br />V= (~ = 23 cfs = 5.75 ft/sec <br />4 sq. ft. 345 ft/min <br />S1/2 = Vn <br />~9 (R) 2/3 <br />_ (5.75) (.032) <br />1.44 (.444)2/3 <br />r 1 <br />~J <br />S1/2 = .212 <br />S = .045 ft/ft or 4.5% <br />Given: Q= 23 cfs <br />Ditch = 8' wide x 1' deep <br />R = A 4 = .444 <br />WP 9 <br />n = .032 <br />Ditches = 8' wide x 1.3" deep <br />installed on 4.5% <br />grade or steeper will <br />be sufficient <br />Selection of Culverts <br />All culverts placed under the highway to carry diverted water off the <br />property, or to carry sediment-laden water to the ponds, will be sized <br />conservatively at 24" with the exception of a culvert placed under lay- <br />down area N2 at the East Mine which carries less than 1 cfs. It is <br />sized 18" -- considerably larger than necessary. <br /> <br />