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RULE 4 PERFORMANCE STANDARDS <br /> <br />Rule 4 Performance Standards 4-40 Revision Date: 4/9/25 <br /> Revision No.: MR-261 <br />4.15.4 Mulching and Other Soil Stabilizing Practices <br /> <br />As addressed in Section 2.05.4, Colowyo currently does not mulch, chisel plow, or terrace, because <br />experience demonstrates sufficient surface roughness survives the topsoil laydown process to <br />maintain favorable seed-bed conditions. If conditions warrant additional topsoil manipulation, <br />Colowyo will utilize an appropriate practice specific to the circumstance. Best management <br />practices, such as minimizing topsoil handling and manipulation, ripping along the contour, <br />disking, or cross ripping will be implemented and are further discussed in Section 2.05.4. <br /> <br />4.15.5 Grazing <br /> <br />All the lands reclaimed by Colowyo will not be grazed by livestock for a period of at least three <br />years after seeding or planting and will be managed to promote the postmining land use. <br /> <br />Grazing by livestock will not commence until Colowyo has demonstrated to the satisfaction of the <br />Division that the vegetation on the reclaimed surface is adequately established and can be expected <br />to withstand grazing pressures. Any grazing studies undertaken by Colowyo will not preclude or <br />interfere with postmining vegetation sampling as required in section 4.15.8. <br /> <br />4.15.6 Field Trials <br /> <br />As a result of previous consultations with CPW and DRMS, Colowyo implemented three field <br />trials. The field trials were meant to provide information to the appropriate expectations for <br />success/failure of establishing these habitat types at Colowyo in the context of a ten-year bond <br />clock, to provide some baseline information that can be used to modify practices, and the plant <br />materials used to meet the current expectations. <br /> <br />The study was comprised of three test scenarios designed to explore different species and habitat <br />requisites necessary for tall shrub survival. The first treatment was to establish an overstory of <br />quaking aspen (Populus tremuloides) trees that are planted into deep topsoil (48 inches). The <br />second treatment was serviceberry (Amelanchier alnifolia) and chokecherry (Prunus virginiana) <br />shrubs planted into deep topsoil (48 inches). The third and final treatment was serviceberry and <br />mountain mahogany (Cercocarpus montanus) shrubs planted into shallow topsoil (4 inches). The <br />aspen trees and/or tall shrubs were planted in ten-220-foot long rows per treatment, for a total of <br />550 plants per treatment. The initial planting consisted of 550 quaking aspen tubelings in the first <br />treatment, 276 serviceberry and 274 chokecherry tubelings in the second treatment, and 276 <br />serviceberry and 274 mountain mahogany tubelings in the third treatment. <br /> <br />The status of each tree or shrub was evaluated in 2012 through 2016. Trees and shrubs that “were <br />observed to be dead” during the evaluation effort in August 2012 needed to be replaced (one-time <br />replacement). Replacement of dead plants occurred in November 2012. During the final evaluation <br />in 2016, no quaking aspen trees in Treatment 1 were observed to be alive. In Treatment 2, no <br />serviceberry and 42 individuals of the chokecherry (15%) were observed to be alive in 2016. In <br />Treatment 3, 143 individuals of the serviceberry (52%) and 147 individuals of the mountain <br />mahogany (54%) were observed to be alive in 2016. The unfavorable results of the aspen and tall