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III IIIIIIIIIIIII III <br />• EXHIBIT 2 <br />5.0 SEDIMENT CONTROL DEMONSTRATION <br />5.1 Purpose <br />According to CDMG regulation 3.03.1(3)(b), Bond liability release cannot be granted until the <br />applicant demonstrates that the existing revegetated areas will result in equivalent or lesser <br />sediment contributions to surface runoff when compared with pre-mining levels as determined <br />by baseline data. <br />5.2 Methods <br />To demonstrate that runoff from the release area will result in equivalent or lesser sediment <br />contribution as compared to baseline conditions, Colowyo presents the following evaluation of <br />four representative study blocks of approximately 20 acres in size. Three of the blocks are <br />located in the East Pit reclaim area and the fourth block is located in the Section 16 reclaim area <br />(see Exhibit 3). The Revised Universal Soil Loss Equation (RUBLE) is utilized to predict and <br />compare the gross annual erosion per acre on these four blocks in both the pre mining and post <br />mining conditions. The technique does not account for the deposition of eroded sediment within <br />the area being evaluated. Nevertheless, RUBLE provides a reasonable basis for comparing <br />sediment yield from undisturbed and revegetated lands. <br />The RUBLE equation and calculations are found below. <br />A=RKLSCP <br />Where: <br />A =Gross erosion per acre per year <br />R =Erosivity of rainfall and runoff <br />K =Soil Erodibility <br />LS = Hillslope-length and Gradient <br />C =Cover Management <br />P =Support Practice <br />Colowyo employed a combination of factors to complete the analysis. Where noted below, <br />many of the factors are previously agreed upon by the Division and found in Permit C-81-019, <br />Exhibit 7, Hydrology, Item 13, "Sedcad Modeling and Maps, 10 Existing Sediment Ponds, 1998." <br />Other factors come from RUBLE Version 1.06. <br /> <br />16 <br />