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RULE 4 PERFORMANCE STANDARDS <br /> <br />Rule 4 Performance Standards 4-41 Revision Date: 2/13/20 <br /> Revision No.: TR-135 <br />areas targeted for the grazingland land use will generally be on slopes greater than 10% and <br />depending on the size of each reclamation unit will need to be chisel plowed (or ripped with a <br />dozer) at a minimum if topsoil laydown activities do not produce sufficient surface roughness to <br />limit the excessive formation of rills on first and second year reclamation blocks by “normal” <br />seasonal runoff events. Contour furrows will be created with regular frequency on slopes greater <br />than 20% and less frequently on areas between 10% and 20% slopes depending on the length of <br />the slope and the size of individual reclamation blocks as determined by topsoil laydown <br />progression in any given year or series of years. Past reclamation efforts undertaken in the East Pit <br />provide a general context to the likely construction frequency of contour furrows in the West Pit <br />and Section 16 reclamation areas. The steeper slopes in the South Taylor area will likely require <br />the construction of contour furrows at a greater frequency than previously mined areas. As <br />indicated under “Mulching Techniques” in Section 2.05.4, use of mulch would be considered a <br />last resort, but is certainly an erosion control metric that may be utilized (where deemed necessary) <br />for long south-facing slopes such as in South Taylor. Spoil will be graded to minimize long, <br />uninterrupted slopes. Replacement of topsoil will be followed by chisel plowing and contour <br />furrowing (when necessary). <br /> <br />The use of these soil stabilizing practices on areas currently undergoing reclamation at Colowyo <br />has been very effective in controlling surface runoff, thereby preventing surface erosion and <br />gullies. The efficacy of these mechanical techniques will continue to be closely monitored as <br />changes to the reclamation program are initiated. <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 />Aspen and Tall Shrub Establishment Areas <br />As a result of negotiations with CPW and DRMS, Colowyo has committed to implementing three <br />field trials. Based upon initial estimates of disturbance to aspen and tall shrub habitats in the South <br />Taylor area, a determination was made that the establishment of 20 acres of aspen habitat and 20 <br />acres of tall shrub habitat (combination of thin and thick topsoil locations) be established in the <br />South Taylor reclamation area (mining disturbance area). As a result of subsequent changes to the <br />mine plan, approximately (7% or 14 acres) of the aspen and (41% or 347 acres) of the tall shrub <br />habitat previously targeted for disturbance will no longer be affected. A reduced area of (18.5) <br />acres of aspen and (12.0) acres of tall shrubs will now be pursued at Colowyo. The field trials are <br />meant to provide information to Colowyo, DRMS and the CPW about the appropriate expectations <br />for success/failure of establishing these habitat types at Colowyo in the context of a ten year bond <br />clock and also to provide some baseline information that can be used to modify practices and the