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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-year, 24-hour and 100-year, 24-hour <br />precipitation events and provides for maintenance of adequate freeboard to prevent <br />overtopping of the embankment. <br />SCS Curve Number and "k" Factor. The curve numbers area based pn information presented in <br />' ~ - ~. <br />Attachment 13-1. The "k" factors were determined with the ai d"'of~the USDA-ARS's revised <br />USLE software package and ere shown in Attachment 13-1. The curve numbers and "k" factors <br />were then "weighted" for each subwatershed es shown on Tables 13-3C-2 to 13-3C-4 and 13-3C-5 <br />to 13-3C-7, respectively. <br />TABLE 13 -3C-2 <br />Weighted CN Calculations for <br />Pond 005 - SWS-1 <br />Vegetation Hydrologic Vegetation <br />Lover Type Soil Grouo Cover (X) CN Area (AC) CN x Aree <br /> <br />Aspen B 30-70 48 3.2 153.6 <br />Aspen C 30-70 57 4.0 228.0 <br /> <br />Aspen <br />D <br />30.70 <br />63 <br />0.2 . <br />12.6 <br />Mixed Brush B 30-70 48 14.6 700.8 <br />Nixed 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 - BS 2.3 195.5 <br /> <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 08/11/92 <br />