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<br />~' <br />to other northwest Colorado coal mines. The Trapper permit acknowledges <br />that one of the factors that should be considered in assessing cover success <br />standards is the rate of soil genesis. The USLE assumptions that the <br />Trapper standards are derived from allow for annual loss of 4 tons/acre/year <br />of topsoil. This would be equivalent to loss of one foot of topsoil in 464 <br />years. In northwest Colorado, it takes thousands of years for a foot of <br />topsoil to form. Finally, the 1980 baseline information in the Trapper <br />permit indicates that the live vegetative cover in the mountain shrub and <br />sageJgrass reference areas was 37.7% and 33.0%, respectively. <br />2. The permit contains production success standards for range sites A, B and C based <br />on historical records collected from pre-mine sites from 1979 through 1985. The <br />Division has two concerns with these standards. <br />A. The production standards are equivalent [o the lower 90% confidence limit <br />of the mean production estimated on the range sites rather than the mean <br />itself. In order to demonstrate successful revegetation for bond release, an <br />operator must show that 90% of the standard has been achieved with 90% <br />statistical confidence. So, Trapper only needs to achieve 90% of a standard <br />which is only 90% of the mean production measured- and that production <br />was measured by clipping only grasses and fortis in communities dominated <br />by shrubs. There was more herbaceous production in these predominantly <br />shrub pre-mine communities than is required in the predominantly grassy <br />reclamation. <br />B. The Trapper production standards appear very low when considering the <br />potential of the soils and the mine site. For instance, the success standards <br />for range sites A, B, and C are 676, 461, and 515 pounds/acre, respectively <br />(herbaceous production only). NRCS range site descriptions for three <br />range sites occurring in the permit area vary from 1200-3000 pounds/acre in <br />favorable years, and from 600-1500 pounds/acre in unfavorable years. <br />3. Table 4.4-12 explains an inverse relationship between the density of sheep manure <br />pellets and stem density at the pre-mine site. This information was presumably <br />used in deriving a shrub density success standard, although the Division could not <br />determine how that was done by reviewing the permit. When the numbers in the <br />table are inserted into the regression equation, the results are not correct. <br />2 <br />