Laserfiche WebLink
Annual Rainfall 19.9 inches <br />Snowfall 68.8 inches <br />Average Temp High 62.7 inches <br />Average Temp Low 29.9 inches <br />Rain fall low May <br />Rain fall high August <br />Pan Evaporation 37.8 inches <br />Peak Flow (Type II Storm -Steep Slope >16% slope <br />NRCS Runoff Curve Number 58 <br />Reference <br />Table U -9 <br />Culvert # 2- May Day #2 Portal <br />Stormwater Hydraulics Analysis <br />May Day Idaho Mine Complex <br />Wildcat Mining Company <br />Durango, Colorado <br />Drainage Flow <br />Area CFS /inch Velocity <br />Return Period Rainfall Duration Rainfall Amount Runoff (acres) Runoff Peak flow (fps) <br />2 24 1.25 0.00 388 270 0.0 <br />10 24 2.7 0.18 388 270 48.6 6.9 * 2 -18 inch CMP (use 2 -24 inch CMPs) <br />25 24 3.5 0.45 388 270 121.5 <br />100 24 3.78 0.58 388 270 156.6 <br />U.S. Department of Commerce, 1961, Technical Paper 40- Rainfall Frequency Atlas of the United States for Durations from 30 minutes to 24 hours <br />and Return Periods fromm 1 to 100 years. Washington , D.C. <br />Wilkes, S. Glade and Erke C. King, 1975, Procedures forDetermining Peak Flows in Colorado, Incorporateds and Supplements Technica Release No. 55 <br />Uraban Hydrology for Small Water <br />Soil Conservation Service, Soil Conservation Naltion Engineering Handbook, Section 4- Hydrology NEH -4. <br />*Handb000k of Steet Drainage and Highway Construction Products, Second Edition, 1971 <br />7/21/2011 <br />• <br />Wildcat Min rporation <br />112(d) Permit— May Day and Mine and Mill Application <br />Exhibit F Culvert #2 May Day #2 <br />• <br />Page 1 <br />