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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 />Figure 0-2) <br />NRCS Runoff Curve Number 58 <br />Reference <br />Culvert Master <br />Table <br />Chief Channel Design Calculations <br />Wildcat Mining Company <br />Durango, Colorado <br />Drainage <br />Area CFS /inch <br />Return Period Rainfall Duration Rainfall Amount Runoff (acres) Runoff Peak flow <br />2 24 1.25 0.00 311 150 0.0 <br />10 24 2.5 0.13 311 150 19.5 <br />25 24 3.5 0.45 311 150 67.5 <br />100 24 3.78 0.58 311 150 87.0 <br />Sq feet Acres 311 <br />Drainage Area 311 acres <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 />Ura ban Hydrology for Small Water <br />Soil Conservation Service, Soil Conservation Naltion Engineering Handbook, Section 4- Hydrology NEH-4. <br />December 23, 2009 <br />Page 1 <br />CMP -Ditch Calculations.xlsx <br />