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2.0 METHODS <br />2.1 SEDIMENTOLOGY DEMONSTRATION <br />In order to satisfy one of the CDRMS requirements for Phase II bond release, <br />reclaimed areas must be shown to contribute equal or less sediment to the receiving <br />waters downstream than equivalent native adjacent areas. There are several <br />methods by which to compare sediment generation from a disturbed site and that <br />from an adjacent undisturbed site. Historically, CDRMS has used a model <br />(SEDCAD+) to evaluate similar or identical watershed sections within the <br />reclaimed area and adjacent undisturbed area. There are limitations to this <br />approach, as there are rarely identical adjacent watersheds. Further, exact <br />knowledge of all of the parameter values for the areas to be compared is often not <br />available. Given the relatively small size of the individual reclaimed disturbances <br />at the Elk Creek Mine, we elected to compare sediment generation from the <br />reclaimed sites and the adjacent undisturbed native areas through the use of the <br />Universal Soil Loss Equation (LISLE) (Wishmeier and Smith, 1978). <br />The USLE uses readily available information on the rainfall, topography, soil <br />particle size characteristics, vegetation, and cultivation practices to generate the <br />amount of soil loss in tons/acre/year. The USLE accounts for rill and inter -rill <br />erosion, the types of erosion commonly found on reclaimed areas. <br />The USLE takes the form: <br />A=R*K*LS*C*P <br />where: <br />A = soil loss in tons/acre/year <br />R = rainfall factor accounting for the interrelationship between the erosive <br />force of rainfall and runoff <br />K = soil erodibility factor addressing a given soil's susceptibility to erosion <br />LS = length slope factor providing the ratio of soil loss at any length and <br />slope to a standard slope and length <br />C = cover factor accounting for plant and litter cover on the ground surface <br />P = control practice factor addressing the erosion reduction effectiveness of <br />soil conservation practices <br />Each of the above factors will be briefly addressed relative to the existing <br />conditions at the Elk Creek Mine reclaimed areas and extended reference area <br />(representing native adjacent areas). <br />............................................................................. <br />............................................................................. <br />Oxbow Mining, LLC Elk Creek Mine Page 2 <br />Phase 11 Bond Release Sedimentology Evaluation 2020 <br />