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DRAINAGE CALCULATIONS <br />FOR <br />CALVARY MEMORIAL CHURCH <br />ORONO, MINNESOTA <br />Land Use <br />Existing <br />School. Open Area <br />Proposed <br />Church, Parking <br />470' <br />0 <br />10% <br />1.93 <br />0.79 <br />Overland Flow Length <br />Channel Flow Length <br />Average Slope <br />Permeable Surface Area <br />Impermeable Surface Area <br />Allowable Outflow After Development (Q^ is assumed to be the <br />undeveloped peak = 100 year rate) <br />470' <br />0 <br />4% <br />1.07 <br />1.65 <br />Cu - undeveloped runoff coefficient =0.30 <br />Flow velocity overland — see below fps <br />tcu (undev) tc ^ • <br />= 470/ ft/sec = see below mins <br />For Small Areas , <br />Set d (duration) = tc^ *= 15 minutes <br />From MnDOT Rainfall Intensity - Return Frequency Graph: <br />i =7.2 in/hr for d = 15 min. <br />On = CIA <br />C =.3(1.93) + 0.90(0.79) = .474 <br />' rrT2 <br />= .474 (7.2 in/hr) (2.72) = 9.28 use 9.3 cfs <br />Developed time of concentration (^cd^ <br />For small areas, let t^^j = 10 min. _ _ . <br />MnDOT: i for (d = t^d " min.) = 8.3 in/hr <br />Developed peak flow rate from the drainage area assuming no flow <br />controls for 10(tcd>. 2°, 30, 40, 50, 60 minute duration storms <br />Cd ” developed runoff coefficient <br />CA = .30(1.07) + .9(1.65) = 0.66 <br />rr72 <br />V ; ;V.: <br />- :v.-'v, <br />Event Nc <br />1 <br />2 <br />3 <br />4 <br />5 <br />6 <br />Inflow • <br />duratioi <br />In <br />Ou <br />n <br />Ql <br />I <br />t^ <br />] <br />Event I <br />intens: <br />and wh< <br />Pond si <br />to dis< <br />v: