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<br />The ditch flow time: <br />t =length/velocity = 280 ft/[(3.3 ft/sec) (60 sec/min)] = 1.41 min <br />Total flow time = 19.6 + 1.41 = 21.01 min <br />Rainfall intensity: <br />For Region 6 <br />I = (210)/(21.01 + 26) = 4.47 in/hr <br />For Region 7 <br />I =(77)/(21.01+10) = 2.48 in/hr <br />I average = 3.48 in/hr <br />The discharge for Area 2 using the Rational Formula: <br />Q = (0.50) (3.48 in/hr) (3.08 acres) = 5.35 cfs <br />Since Ditch D-2 also collects discharge from Ditch D-1, the total flow <br />Q=5.35 cfs+1.31 cfs=6.66 cfs <br />The rated discharge for the trial ditch using Manning's Equation: <br />The properties of a trapezoidal 1.5-ft-deep, 2:1 side slope, 2-ft-wide bottom ditch: <br />A = (Sft)(lft) - (3ft)(1.5ft) = 7.5 ft' <br />P=2ft+2(3~+1.5')°'S0=871ft <br />R=A/P=7.5ftZ/8.71 ft=0.86ft <br />The slope of Ditch D-2 is 0.007% <br />Q = (1.486/n) A R Z" S "~ <br />Q = (1.486/0.025) (7.5ft')(0.86 ft)"' (0.007)"' <br />Q = 33.734 cfs <br />33.734 cfs > 6.66 cfs, Q ditch > Q drainage, trial ditch is adequate <br />Ditch D-3 <br />Trial configuration -trapezoidal ditch, 1.5-ft-deep, 2:1 side slope, 2-ft-wide bottom, <br />unlined, assumed velocity = 7 fps <br />Overland flow time for Area 3 (0.70 acre), which contributes to Ditch D-3, is 17.8 min, <br />from the Yarnell Figure H. <br />The ditch flow time: <br />t =length/velocity = 232 ft/[(7 ft/sec) (60 sec/min)] = 0.50 min <br />Total flow time = 17.8 + 0.50 = 18.35 min <br />Summary of Kvaerner Glculations <br />Piceance Site Inversion lhtch System <br />7echnial Revision Mining and Reclamation Permit <br />