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Wildcat <br />112(d) Permit— May Day and Mir poration ine and Mill Application • <br />Peak Flow (Type II Storm- Moderate) <br />(Wilkes and King, 1975 Figure D - -2) <br />NRCS -Runoff Curve Number 80 <br />Drainage Area 40000 ft <br />Annual Rainfall 19.9 inches <br />Snowfall 68.8 inches <br />Pan Evaporation 37.8 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 />Table U -5 <br />May Day Mill and Mine Site -Bench Pond Sizing including Spillway <br />Mayday No. 1 <br />Wildcat Mining Company <br />May Day Mine -Bench Drainage /Pond Sizing <br />Durango, Colorado <br />Disturbed <br />Drainage Area CFS /inch Peak flow Area Total <br />Return Period Rainfall Duration Rainfall Amount Runoff (acres) Runoff (cfs) Velocity Volume <br />(fps) (Cubic Feet) <br />2 24 1.25 0.17 1.15 2 0.3 567 <br />10 24 2.5 0.89 1.15 2 1.8 2967 <br />25 24 3.5 1.64 1.15 2 3.3 5467 <br />100 24 3.78 1.90 1.15 2 3.8 6333 <br />Annual Rainfall 19.9 inches <br />Snowfall 68.8 inches <br />Pan Evaporation 37.8 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 />Reference <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 Technical Release No. 55 <br />Uraban Hydrology for Small Water <br />Soil Conservation Service, Soil Conservation Naltion Engineering Handbook, Section 4- Hydrology NEH -4. <br />7/21/2011 Table U -5 U -5 - Bench -Pond sizing No.1.xlsx 1CMP -Ditch Calculations.xlsx <br />