2019-11-22_REVISION - C1981019 (2)

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RULE 4 PERFORMANCE STANDARDS 3. The ability to achieve adequate levels of herbaceous cover at Colowyo is,without question, quite possible. The vegetative monitoring completed at Colowyo during the last three decades, and summarized in annual reports, indicates that the premining levels of herbaceous cover are easily achieved. In fact, the vegetative data as summarized in the annual reports indicate that the levels of herbaceous cover on the reclaimed areas may have exceeded the premine condition by 30% to 50%. The vegetative sampling serves to confirm what can be observed in the field. The revegetation at Colowyo is excellent and there is virtually no evidence of erosion attributable to a lack of cover. In fact,the herbaceous cover existing at Colowyo meets or exceeds the premining condition and is undoubtedly providing significant competition with the woody specie seedlings. There is certainly no evidence that herbaceous cover values on the reclaimed areas should be set higher than the herbaceous cover of the premine areas in order to achieve bond release. Herbaceous Production For both Pre-2008 and Post-2008 revegetation (targeting (and achieving) the rangeland land use subcomponent of grazing land), herbaceous production of the revegetated area will be considered adequate for final bond release if it is not less than 90% of the herbaceous production, as determined from the reference areas with a 90%statistical confidence utilizing a standard students statistical t-test comparison of the means. As allowed under the rules promulgated on 9/14/05, these comparisons may utilize one of three methods detailed under Rule 4.15.11 (2) [(a), (b) or (c)]. As allowed by Rule 4.15.7 (4), either weighted-average or individual protocols will be followed. For grassland testing the weighted average approach(Rule 4.15.7(4)(b))will be utilized where reference area data and revegetated area data are "weighted" (each combined into single values for comparison) based on the proportional acreage of pre-mine communities within the disturbance area footprint. Testing will then follow procedures detailed under Rule 4.15.11 (2) with preference being given first to subsection (a) [direct comparison], second to subsection (c) [reverse-null testing], and third subsection(b) [classic t-test]. For areas designated as Post-2008 sagebrush steppe revegetation (rangeland land use subcomponent of wildlife habitat), herbaceous production success criteria will be eliminated as a requirement should CDRMS rules change as expected in the near future. In the meantime, for Post-2008 sagebrush steppe revegetation, herbaceous production of the revegetated area will be considered adequate for final bond release if it is not less than 70% of the herbaceous production as determined from the reference areas with a 90% statistical confidence utilizing a standard student's statistical t-test comparison of the means. If necessary, a reverse-null hypothesis testing procedure may be utilized in accordance with procedures detailed in Rule 4.15.11 (2) (c). As inferred under Rule 4.15.8 (3) (ii), relaxation of the herbaceous production standard for areas targeting wildlife habitat post-mining land uses is designed to compensate for revegetation techniques (prescribed ecological reclamation approach) that must discourage grasses to encourage shrubs in the post-revegetated community. Justifications for reduction to 70% are identical to those presented for cover in the previous section. Rule 4 Performance Standards 4-66 Revision Date: 11/18/19 Revision No.: MR-211