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RAINFALL FACTOR (R) <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 derived from Figure 1. Rainfall and Runoff Factors "R" for use <br />with the Universal Soil Loss Equation (LISLE) contained in the U. S. Department of <br />Agriculture Technical Note #50 (revision #2) Universal Soil Loss Equation. <br />The annual average R factor was determined to be 40.0 for both the reclaimed and <br />adjacent undisturbed areas in the Durango, Colorado area. <br />SOIL 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 <br />Table 4.1 from the U. S. Department of the Interior OSM publication, Design of Sediment <br />Control Measures for Small Areas in Surface Coal Minim was used to determine the K <br />factors for the native and reclaimed areas. <br />Five soil series were present prior to mining, the Falfa clay loam, Zyme-Rock Outcrop <br />Complex, Ustic Torriorthents, Ustolic Haplargids, and Rock Outcrop. The vast majority <br />of soil salvaged for reclamation at the Carbon Junction Mine was from the Falfa clay loam <br />series, as the remaining map units were too rocky to allow salvage of suitable material. <br />A K factor of 0.28 was selected for the reclaimed and agricultural areas, based on the <br />textural class of the Falfa soil series (clay loam) present in these areas. A K value of 0.25 <br />was used for the native areas adjacent to the haul road and North Pit. These areas contain <br />thin soils and shale and siltstone rock outcrops (Zyme-Rock Outcrop Complex, Ustic <br />Torriorthents, Ustolic Haplargids, and Rock Outcrop soil map units) that decompose into <br />silty clay 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 Carbon Junction Mine <br />site, the reclaimed and adjacent undisturbed slopes vary dependent on their position at the <br />mine. For this reason, multiple cross sections were selected for the upper and lower <br />reclaimed North Pit areas, the native area adjacent to the North Pit, the reclaimed Haul <br />Road and adjacent native areas, and the Equipment Area and adjacent agricultural area. <br />The measurements for these areas are detailed below. From the information on the slope <br />angle and length, the LS factor was obtained from Table 5.5 LS Values from the Erosion <br />and Sediment Control Handbook. <br />Slope Angle and Length Data by Location <br />Oakridge Energy Carbon Junction Mine Page 3 <br />Sediment Pond Sedimentology Demonstration