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APPENDIX 2.05.3-108 <br />• NORTHWEST SEDIMENT TRAP - OUTLET DESIGN <br />100-YEAR STORM EYENT <br />SUN COAL COMPANY - MEADOWS N0. 1 <br />ROUTT COUNTY, COLORADO <br />(Map 19) <br />Area E1 + E2 - Sediment Trap Design <br />Area E1 11.8 acres <br />Area E2 2.1 acres <br />Total Area E1 + E2 13.9 acres <br />Channel length 1800 feet <br />CN* (Curve Number) 75 <br />Precipitation* - 25-yr/24-hr 2.0 inches <br /> 10-yr/24-hr 1.6 inches <br />Runoff* - 25-yr/24-hr 0.38 inches <br /> 10-yr/24-hr .20 inches <br />Slope Adjustment Factor* <br />slope 15x <br />slope adjustment .99 <br />Equivalent drainage area* 40 acres <br />• Equivalent peak flow* 45 cfs for 40 acres <br />in <br />Drainage E1 + E2 <br />Q 25 yr = (45 cfs/in)(.38 inches) = 17.10 cfs 1~0 (.99) = 4.5 cfs <br />Drainage E1 + E2 <br />Q 10 yr = (45 cfs/in)(.20 inches) = 9.0 cfs 11.8 (,99) = 2.6 cfs <br />40.0 <br />Area E1 + E2 -Sediment Trap Volume Calculations <br />Area 13.9 acres <br />CN* 75 <br />Precipitation* - 25-yr/24-hr 2.0 inches <br />10-yr/24-hr 1.6 inches <br />Runoff* - 25-yr/24-hr .38 <br />10-yr/24-hr .20 <br />E1 + E2 Drainage Area <br />Q Total 25-year 13.9 acres x .38 inches = .44/ac/ft <br />inches foot <br />Q Total 10-year 13.9 acres x •20 inches .23 ac/ft <br />1 inches oot <br />. * Source: USDA-SCS Technical Release No. 55 and Procedures for Determining Peak <br />Flows in Colorado, March 1980. <br />- 303 - (Rev. 5/86) <br />