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RULE 4 PERFORMANCE STANDARDS <br />3. The ability to achieve adequate levels of herbaceous cover at Colowyo is, without question, <br />quite possible. The vegetative monitoring completed at Colowyo during the last three <br />decades, and summarized in annual reports, indicates that the premining levels of <br />herbaceous cover are easily achieved. <br />In fact, the vegetative data as summarized in the annual reports indicate that the levels of <br />herbaceous cover on the reclaimed areas may have exceeded the premine condition by 30% <br />to 50%. <br />The vegetative sampling serves to confirm what can be observed in the field. The <br />revegetation at Colowyo is excellent and there is virtually no evidence of erosion <br />attributable to a lack of cover. In fact, the herbaceous cover existing at Colowyo meets or <br />exceeds the premining condition and is undoubtedly providing significant competition with <br />the woody specie seedlings. There is certainly no evidence that herbaceous cover values <br />on the reclaimed areas should be set higher than the herbaceous cover of the premine areas <br />in order to achieve bond release. <br />Herbaceous Production <br />For both Pre -2008 and Post -2008 revegetation (targeting (and achieving) the rangeland land use <br />subcomponent of grazing land), herbaceous production of the revegetated area will be considered <br />adequate for final bond release if it is not less than 90% of the herbaceous production, as <br />determined from the reference areas with a 90% statistical confidence utilizing a standard students <br />statistical t-test comparison of the means. As allowed under the rules promulgated on 9/14/05, <br />these comparisons may utilize one of three methods detailed under Rule 4.15.11 (2) [(a), (b) or <br />(c)]. As allowed by Rule 4.15.7 (4), either weighted -average or individual protocols will be <br />followed. For grassland testing the weighted average approach (Rule 4.15.7 (4) (b)) will be utilized <br />where reference area data and revegetated area data are "weighted" (each combined into single <br />values for comparison) based on the proportional acreage of pre -mine communities within the <br />disturbance area footprint. Testing will then follow procedures detailed under Rule 4.15.11 (2) <br />with preference being given first to subsection (a) [direct comparison], second to subsection (c) <br />[reverse -null testing], and third subsection (b) [classic t-test]. <br />For areas designated as Post -2008 sagebrush steppe revegetation (rangeland land use <br />subcomponent of wildlife habitat), herbaceous production success criteria will be eliminated as a <br />requirement should CDRMS rules change as expected in the near future. In the meantime, for <br />Post -2008 sagebrush steppe revegetation, herbaceous production of the revegetated area will be <br />considered adequate for final bond release if it is not less than 70% of the herbaceous production <br />as determined from the reference areas with a 90% statistical confidence utilizing a standard <br />student's statistical t-test comparison of the means. If necessary, a reverse -null hypothesis testing <br />procedure may be utilized in accordance with procedures detailed in Rule 4.15.11 (2) (c). As <br />inferred under Rule 4.15.8 (3) (ii), relaxation of the herbaceous production standard for areas <br />targeting wildlife habitat post -mining land uses is designed to compensate for revegetation <br />techniques (prescribed ecological reclamation approach) that must discourage grasses to <br />encourage shrubs in the post-revegetated community. Justifications for reduction to 70% are <br />identical to those presented for cover in the previous section. <br />Rule 4 Performance Standards 4-65 Revision Date: 11/27/18 <br />Revision No.: TR -129 <br />