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RULE 4 PERFORMANCE STANDARDS <br />4.15.5 Grazing <br />All the lands reclaimed by Colowyo will not be grazed by livestock for a period of at least three years <br />after seeding or planting and will be managed to promote the postmining land use. <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 to <br />withstand grazing pressures. Any grazing studies undertaken by Colowyo will not preclude or interfere <br />with postmining vegetation sampling as required in section 4.15.8. <br />4.15.6 Field Trials <br />In 1975 Colowyo funded a revegetation study that was initiated on the Colowyo property by the <br />Department of Agronomy at the Colorado State University and the Colorado State University Experiment <br />Station. The study was designed and the work was monitored mostly to determine the suitability of using <br />native species at the mine site. Test plots were used to simulate the disturbance that would result from <br />surface mining. <br />The complete details of the four-year revegetation study are found in Exhibit 10, Vegetation Information. <br />Also, in 1977 an additional shrub study was initiated in conjunction with the Soil Conservation Service, <br />Upper Colorado Environmental Plant Center. Approximately 35 species of shrub seedlings from the <br />Plant Materials Center were being evaluated for potential use in mined land revegetation. <br />Field trials have been, and continue to be, an ongoing effort at Colowyo since these initial studies <br />indicated above (1975 and 1977). The most recent evaluation of efforts to establish shrubs and trees in <br />pre -2000 revegetation resulted in the following assessment by Cedar Creek Associates, Inc. (2006): <br />"Given the assumptions presented, past and present shrub counts, as well as <br />recent shrub mapping, it can be postulated that the planting of bare root shrubs <br />and containerized trees from 1979 through 2000 can be considered a failure <br />(<10% survival). Shrub populations or patches on an overwhelming majority of <br />reclaimed surfaces [prior to 2000] are well below the [old] success standard of <br />1,000 woody plants per acre (except within fenced enclosures) and a majority of <br />the surviving shrubs in open (unfenced) revegetation were not planted, but were <br />apparently included in the seed mix (i.e. Big Sagebrush - Artemisia tridentata). <br />There is no doubt that browsing by big game species, as well as competition from <br />aggressive grass species such as smooth brome (Bromus inermis) and <br />intermediate wheatgrass (Agropyron intermedium) have prevented germination <br />and growth of shrub populations on pre -2000 revegetation. Therefore, future <br />bare -root planting of shrubs on new and older reclamation is not recommended <br />based on very poor performance in the past. Any effort to increase shrub <br />densities on older (pre -2000) revegetation will prove to be very difficult and <br />expensive with little or no chance for success given the present competition from <br />established grass species and big game grazing pressures. Therefore, it is <br />recommended that Colowyo continue discussions with the state agencies to alter, <br />through technical revision, target land uses and bond release standards applicable <br />to at least pre -2000 revegetation areas." <br />Rule 4 Performance Standards 4-43 Revision Date: 1/31/18 <br />Revision No.: TR -119 <br />