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At best, establishment of new plants at very high elevation is slow because of the <br /> above-cited factors, but, given time to slowly accumulate carbon reserves and develop <br /> root systems, experience has shown that planted vegetation can eventually mature <br /> over a period of years. Expectations for establishment that are based on experience at <br /> low elevation will be too high at these upper elevations. <br /> As previously alluded, the Coal Basin sites are subject to all of the constraints <br /> described above but have in addition at many locations the constraints imposed at any <br /> elevation by extremely steep slope angles. The natural slope angles were steep (up to <br /> xxx:1 (h:v)), but benching associated with mine construction and operation has created <br /> cut and fill slopes even steeper. Steep slope angle affects plant growth potential in <br /> two main ways. First, the steep angle tends to allow incident moisture the opportunity to <br /> runoff before penetrating the soil and becoming available for uptake by plant roots. <br /> Second, as moisture runs off these steep angles, it has a very high capacity for <br /> carrying suspended sediment and, hence, as sediments are suspended and removed <br /> downslope, erosion can proceed at high rates. Beyond the potential impacts to aquatic <br /> and terrestrial ecosystems below, the loss of surface materials may expose <br /> ungerminated seeds or carry them away, or uproot seedlings with minimal root <br /> development. Lowered surface elevation will also leave surviving plants "pedestalled" <br /> and with reduced access to a wetted soil zone. The oversteepened slopes left by the <br /> former operators at Coal Basin make an already difficult revegetation task that much <br /> more difficult. <br /> Despite the difficulty, the abandonment of oversteepened slopes by the former operator <br /> demands that the consequent exaggeration of erosional danger be addressed through <br /> revegetation. <br /> ASSESSMENT OF EROSION HAZARD AT COAL BASIN <br /> Although the presence of slopes nearing and even exceeding 1:1 (h:v) intuitively <br /> suggests a high erosion hazard, the quantitative potential for sediment yield is not eaily >� <br /> 3 <br />