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24-hour precipitation event. Finally, the design conservatively assumed the pond is 100 <br />percent full to the emergency spillway during the 25-yea r, 24-hour and 100-year, 24-hour <br />precipitation events and provides for maintenance of adequate freeboard [o prevent <br />overtopping of the embankment. <br />SCS Curve Number and "k" Factor. The curve numbers area based on information presented in <br />Attachment 13-1. The "k" factors were determined with the aid of the USDA-ARS's revised <br />USLE software package and are shown in Attachment 13-1. The curve numbers and ~'k" factors <br />were then "weighted" for each subwatershed as shown on Tables 13-3-2 to 13-3-4 and 13-3-5 <br />to 13-3-7, respectively. <br />TABLE 13-3-2 <br />weighted CN Calculations for <br />Pond 005 - Sw5-1 <br />Vegetation Hydrologic Vegetation <br />Cover TYee___________ _____Soi l _Groue_ _____COVer_i%L__ _CN __ Area_jACj___ _CN x Area <br />Aspen B 30-70 48 3.2 153.6 <br />Aspen C 30-70 57 4.0 228.0 <br />Aspen D 30-70 63 0.2 12.6 <br />Mixed Brush B 30-70 48 14.6 700.8 <br />Mixed Brush C 30-70 57 12.2 695.4 <br />Mixed Brush D 30-70 63 0.8 50.4 <br />Sagebrush B 30-70 51 4.5 229.5 <br />Sagebrush C 30-70 63 2.9 182.7 <br />Sagebrush D 30-70 70 0.1 7.0 <br />Topsoil Stockpile B - 76 5.5 418.0 <br />Disturbed/Spoil/Graded Spoil B - 86 118.4 10,182.4 <br />Haul Road B - 85 2.3 195.5 <br /> Total 168.7 13,055.9 <br />weighted Average CN 13 .055.9 = 77.4 Use: 78 <br /> 168.7 <br /> <br />13-3-4 Revised 03/13/92 <br />