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r • <br />Revised Ditch Design <br />1. Ditch: 22-D3 <br />2. Description: Diversion ditch around active mining pit. <br />3. Grade of Ditch: .014 or 1.47 <br />4. Area Drained: 107 acres <br />5. Peak Discharge: 154 cfs w/1.25 correction factor <br />6. Ditch Design: <br />* The peak discharge was assumed to be correct for the purposes <br />of the revised ditch design. <br />n = .030 <br />Use ditch w/"V" walls 2:1 slope See chart 1031.2-2 fi <br />Calculations below <br />From chart: 2' FB DT D = 2.70 A = 2D + 2D2 V = 7.7 fps <br />= 5.4 + 14.58 <br />C = 19.98 <br />* Depth for "V" DT w/2:1 S1 D = ~- <br />2 <br />-~8 <br />2 <br />= 3.16 <br />* D = 3.16 feet deep <br />Add 0.5 freeboard <br />Use 3.66 feet deep <br />