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Case <br />R <br />K <br />LS <br />C <br />P <br />A - Sediment <br />Loss in Tons <br />per acre /year <br />Comments <br />Pre -Mine Condition- <br />Irrigated Pasture <br />26 <br />.32 <br />1.02 <br />0.003 <br />1.0 <br />0.025 <br />Data from Year <br />1987 <br />Post -Mine Condition- <br />Irrigated Pasture <br />Areas <br />26 <br />.32 <br />0.57 <br />0.007 <br />1.0 <br />0.033 <br />Data from Year <br />2007 <br />Practice Factor "P" <br />This factor is only applicable when such practices as contouring perpendicular to the <br />slope are used. None of these items are applicable to the pre- mining case and are <br />excluded in post -mine to keep the calculations conservative. Therefore, the "P" factor <br />for both the pre -mine and post -mine cases is 1.0. This is true for all reclaimed areas at <br />the New Horizon #2 Mine. <br />Calculations <br />Conclusions <br />As shown by the above calculations, the erosion in tons per acre per year for both the pre - <br />mine and the post -mine cases are essentially zero. Both cases have tremendous live cover <br />and litter values. In speaking with Jim Sharkoff, who is the NRCS expert on RUSLE in <br />the State of Colorado, he stated that RUSLE II or any of the predecessor versions simply <br />were never meant to determine differences in erosion to the nearest tenth of a ton per <br />acre. He stated that, with all the variables involved, the best that RUSLE can do is <br />estimate to the nearest ton per acre. Given the above predictions of 0.025 and 0.033 tons <br />per acre erosion per year, he stated that the erosion from both cases is basically nothing <br />and that certainly a difference of 0.007 tons per acre is no difference at all, given the <br />assumptions inherent in the inputs. <br />Other data that help support the above conclusion are as follows: <br />1) The primary forb in the post -mine case is medicago sativa (44.6 %), which has a better <br />true ground cover than the 2 principal forbs in the pre -mine condition, which are platago <br />lanceolata (14.0 %) and trifolium repens (8.5 %). <br />2) The litter in the pre -mine case is 22.7% and the post mine case, litter is 15.9 %. Litter <br />is counted the same as grass cover for the purposes of the erosion calculations, therefore <br />SL -14 03DEC12.wpd 38 <br />