2010-12-17_REVISION - C1981019 (108)

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RULE 2 PERMITS furrows, approximately 4 -6 inches deep at the deepest point and 20 -25 inches wide, which have been used on slope areas very successfully during the past several years, will be used to reduce erosion potential, conserve moisture, and maintain site stability until vegetation is sufficiently established. The size of the furrows may be increased if necessary to control erosion, and the distance between the furrows will vary, but will be approximately 10 to 75 feet along the slope. Small rock check dams may also be used where appropriate to aid in control of erosion both prior to seeding and if necessary, after an area has been seeded. Colowyo will utilize the planned post -mine topography (PMT) to help identify candidate (and prime candidate) areas for targeting Sagebrush Steppe post- mining communities. Key to this analysis will be considerations for the risk of erosion and for long -term stability. One such "threshold" value to be used for this analysis will be a slope break at 10% gradient. Slopes greater than 10% will be considered too risky to make attempts at targeting shrub communities, largely due to snowpack runoff scenarios that can often lead to serious erosion and stability failures. For example, snowmelt runoff in the early 1980s caused widespread and severe down- cutting of the natural drainages to the immediate west of Colowyo. Unless proven otherwise by hydraulic and/or erosion modeling, slopes less than 10% will be identified as candidate locations for shrub community establishment. Another "threshold" value to be used in the PMT analysis is the size of units that may exhibit slopes 10% or flatter. Areas small in aerial extent (e.g., less than about 5 acres) will not be identified to receive shrub - conducive metrics. Only those areas that are larger will be identified. The exact size cutoff will be at the discretion of the reclamation coordinator, however, a practical limitation must be defined given the complications realized by the change in revegetation targeting measures. Where Sagebrush Steppe revegetation will be targeted, Colowyo would apply shallow lifts of topsoil (< 6 inches, ideally 4 inches). Where ideal spoil conditions are encountered, special effort will be made to place very minimal topsoil layers (nearly zero). The size of these areas must be small in order to ensure the potential erosion potential created by this activity does not negatively impact areas down slope. The Division will be informed of any instances of "nearly zero" topsoil laydown areas prior to or during topsoil laydown activities to ensure that the Division has the opportunity to verify Colowyo is adequately managing erosive potential. In most cases, due to the general rockiness of Colowyo's spoil, a layer of topsoil is desirable in order to limit damage to the preferred seeding equipment that will be utilized wherever possible in these areas, as proper seed depth placement is a major factor when establishing shrubs. To help maintain topsoil replacement balances, thicker lifts of topsoil (> 6 inches, occasionally up to 2 -3 feet) can be placed along the groin of opposing slopes (drainage- ways). On long slopes steeper than 10 %, topsoil distribution using pushdown techniques may be altered to facilitate thin layers near the upper shoulders of the slope, with thicker layers near the bottoms. In this manner, the lower elevation areas that tend to catch more snow will receive and store greater quantities of moisture with the hope that some of the mountain shrub seed within the seed mix will be presented with enhanced opportunities for growth and development, especially taxa such as snowberry. The shoulders of the slope, where soil thickness has been reduced will present greater opportunity for sagebrush to develop given reduced competition from cool- season grasses. In order to facilitate proper accounting of the topsoil resource, topsoil placement on specific areas will be tracked by load counts of the equipment involved. In cases where only Sagebrush Steppe acres are reclaimed in one season, replacement volumes may be less than the available 6 -inch average. This does not cause undue harm on the resource as the "left over" material will be utilized in the development of deeper soil areas elsewhere in the reclamation progression. All activities will be accurately and fully described within the confines of the Annual Reclamation Reports that include topsoil balance tracking. Another directive with regard to topsoil distribution (at the discretion of the field supervisor) will be instruction to equipment operators to NOT engineer the final surface, but to the contrary leave it in a very roughened state, where there is the opportunity to diversify the potential plant communities within Collom — Rule 2, Page 104 Revision Date: 1/23/09 Revision No.: PR -03