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Practice Factor "P" <br />This factor is only applicable when such practices as contouring perpendicular to the slope <br />are used. None of these items are applicable to the pre-mining case and are excluded in <br />post-mine to keep the calculations conservative. Therefore, the "P" factor for both the pre- <br />mine and post-mine cases is 1.0. This is true for all reclaimed areas at the New Horizon #2 <br />Mine. <br />Calculations <br />Case R K LS C P A- Sediment Comments <br /> Loss in Tons <br /> per acre/year <br />Pre-Mine Condition- 26 .32 1.02 0.003 1.0 0.025 Data from Year <br />Irrigated Pasture 1987 <br />Post-Mine Condition- 26 .32 0.57 0.007 1.0 0.033 Data from Year <br />Irrigated Pasture 2007 <br />Areas <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 and <br />litter values. In speaking with Jim Sharkoff, who is the NRCS expert on RUSLE in the State <br />of Colorado, he stated that RUSLE 11 or any of the predecessor versions simply were never <br />meant to determine differences in erosion to the nearest tenth of a ton per acre. He stated <br />that, with all the variables involved, the best that RUSLE can do is estimate to the nearest <br />ton per acre. Given the above predictions of 0.025 and 0.033 tons per acre erosion per year, <br />he stated that the erosion from both cases is basically nothing and that certainly a difference <br />of 0.007 tons per acre is no difference at all, given the 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 true <br />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 is <br />counted the same as grass cover for the purposes of the erosion calculations, therefore the <br />pre-mine gets a better benefit for this item. Since this post-mine data is from midway through <br />the bond release process, the litter can be expected to improve over time as compared to the <br />pre-mine condition, which was not disturbed for decades. <br />SL-12 29MARIl.wpd 25