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~q "foY~ I G ---_.-~ <br />79.8 __~z~~__-_ -- <br />5b _o~ <br />,o ~ . O~ a. <br />A- ~ ~ .oi ~ <br />I <br />Postmine Condition: Specfic to each pit area (dependent on ground <br />cover) <br />CP factors represent permanent rangeland with grass and no appreciable <br />canopy cover. <br />Rainfall Factor, R. An average annual R value and an average storm R value a~J~ <br />is needed to compute long-term erosion, in order to calculate the annual <br />sediment yield. Values were calculated using procedures set forth in Barfieldotl-~ <br />et. al., (1981) as follows: <br />R~,~„„ = 27P~ for a Type II Storm <br />Where: Pz, = 2-year, 6-hour precipitation in inches <br />= 0.9 inches <br />Therefore, <br />R,~~,W = 27(0.9) = 21.4 <br />Do..en <br />Where: Pis the 10-year, 24-hour preapitation in inches and D is the <br />storm duration in hours <br /> <br />Therefore, <br />R„,,,,, = 19.25 1. " = 15.9 <br />(24)a"'= <br />Sediment Specific Weight, SW. The Specfic weight of loose sandy-loam is <br />approximately 85 Ibs/ft'. <br />12 <br />