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The levels of total suspended solids (TSS) contributed by the reclaimed area to runoff <br />or streamflow outside the permit area must be less than or comparable to the pre - <br />mining condition or levels documented for comparable adjacent areas. This condition <br />can be demonstrated: <br />where: <br />c. If sufficient data are available, a comparison using an appropriate predictive <br />model of the suspended solids generated off the pre- mining land or comparable <br />adjacent area, and the reclaimed area during a similar intensity storm event. <br />Response: The land requested for this bond release is irrigated pasture, which was <br />originally irrigated before mine disturbance. Since a comparison must be made of the <br />sediment loss from the reclaimed area to that of the original mine community, the best <br />manner to accomplish this is to use the vegetation statistics from the reclaimed areas <br />and the same areas prior to mining in 1987. <br />The Universal Soil Loss Equation was developed in 1965 by Wischmeier and Smith <br />using earlier equations by Musgrave in 1947. The equation was modified in 1993 to <br />account for steeper slope areas, change in erosion over time among other improvements. <br />The revised equation (RUSLE) does account for rill and inter -rill erosion. Its complete <br />form is listed below: <br />A= RxKx(Lx5)xCxP <br />A = annual soil loss in tons /acre <br />R = rainfall factor (from standard chart of area) <br />K = soil erodibility factor (function of site specific soil) <br />LS = length slope factor (from contour map & chart) <br />C = management factor dependent upon vegetation & mulch <br />P = erosion control practice factor (constant) <br />Rainfall Factor "R" <br />The rainfall factor is the product of rainfall energy times the maximum 30- minute <br />intensity for a given rainstorm. It is considered as the erosive power of the rain for that <br />particular area. A chart of "R" values for Colorado developed by the Transportation <br />Research Board in 1980 shows that the "R" value for the entire Nucla area is 26. This <br />can be seen in Appendix 5. <br />Since the reclaimed land slope is similar to the pre -mine slopes, the same rainfall factor <br />SL -14 03DEC12.wpd 30 <br />