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Nov 22 OS 08:12a Edith Savage <br />RAINFALL FACTOR (R) <br />303 665 6808 <br />The rainfall factor addresses the interrelationship of the erosive forces of falling raindrops <br />and runoff to predict both rill and inter-rill erosion. In this demonstration, an average <br />annual value of R was computed based on a Type II stoim event (Barfield, Warner, and <br />Haan, 1981). The equation used to compute the R factor is as follows: <br />Average Annual R = 27*(PZ 6~•Z <br />where P2,~ is the 2-yeaz, 6 hour precipitation in inches from published rainfall data (e.g., <br />Miller, et al, 1973). , <br />The 2-year, 6-hour Type II storm event for the Keenesbutg, Colorado azea was <br />conservatively identified as 1.4 inches of rainfall. The annual average R factor is then <br />computed to be 56.60 for both the reclaimed and adjacent undisturbed areas. <br />SO1L ERODIBILITY FACTOR (K) <br />The soil erodibility factor K is a measure of a soil's susceptibility to erosion and was <br />determined from the USDA SCS publication, Soils of Colorado: Loss Factors and <br />Erodibilit~ydrolo,~c Groupings. Two soil series were present prior to mining, the <br />Osgood and Valent soil series. The single difference between these soils is the lack of a <br />"B" horizon in the Valent sand. The native sand sage community was presumed to have a <br />mixture of these soil series, as were the reclaimed areas. A K factor of 0.11 was used for <br />the reclaimed areas, based on K values for "A", "B", and subsoil horizons salvaged from <br />the Valent and Osgood soils. A K value of 0, IO was used for the native area, based on K <br />values for surface soil horizons from the Valent and Osgood soils. <br />LENGTH SLOPE FACTOR (LS) <br />The steepness of the slope and the length of the slope both affect the degree of soil <br />erosion on a given slope surface. The LS factor is a ratio of soil loss at any length and <br />slope to that of a standard empirical slope. In the instance of the Keenesburg Mine site, <br />the reclaimed and adjacent undisturbed slopes aze of relatively uniform slope for the azeas <br />of concern. In this case the LS factor can be calculated by the following equation: <br />LS = (~, i 72.6)n' * (430x2 +30x + 0.43)/6.613 <br />where: <br />7v is slope length <br />xis sin A (where 8 is the angle of slope) <br />m is a slope dependent exponent (0.5 in our case) <br />p.6 <br />Cooro Energy Comyany Keenesburg Mine Page S <br />Phase II Bond Release 5edimeritology Demonstration <br />