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POND9.WK1 <br />APPENDIX 4-B. VOLUME III <br />SEDIMENT POND 9 CAPACITY <br />Sediment Pond 9 (P-91 is located in the central portion <br />of the reclaimed No. 1 Mine area. The pond has an <br />18" CMP combination primary and emergency spillway <br />which no longer satisfies the Rules for sediment ponds. <br />This calculation sheet will check the pond size and also <br />provide the design for the revised spillway system. <br />STORM EVENTS <br />10 YEAR 24 HOUR EVENT 1.8 INCHES <br />25 YEAR 24 HOUR EVENT 2.2 INCHES <br />100 YEAR 24 HOUR EVENT 2.4 INCHES <br />The run-off calculations presented below are calculated based <br />on the manual - Procedures for Determining Peak Floras in <br />Colorado - published by the Soil Conservation Service March <br />1984. <br />The soil type for the area is Dollard, soil type C. A <br />CN of 74 is selected on the basis of soil type C and <br />• pasture or range in good condition from figure S-4. <br />RUN-OFF VOLUME - - POND 9 <br />PRECIP DIRECT <br />CURVE AMOUNT RUN-OFF <br />15.90 74 1.8 0.26 <br />TOTAL REQUIRED WATER VOLUME <br />SEDIMENT VOLUME <br />USING THE UNIVERSAL SOIL LOSS EQUATION <br />A= R K L S C P <br />R = rainfall factor <br />K = soil erodibility factor <br />LS = combined length slope factor 9.5% - 1330' <br /> H = 126 L = 1330 S = 126/1330 = 9.5% <br />C = cropping management factor <br /> 30% Ground Cover, 25% Canopy <br /> Average of 0.17 & 0.09 <br />P = erosion control practice factor <br />• Contour Farming 9.5% Slope <br />A = sediment,tons/acre/,year <br />P-9-1 <br />RUN-OFF <br />VOLUME AF <br />0.35 <br />0.35 <br />30.00 <br />0.21 <br />5.00 <br />0.13 <br />0.60 <br />2.46 <br />New 7-11-91 <br />