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shrubs would be most adversely affected. Higher levels of herbaceous. cover <br />would adversely compete against woody vegetation and hinder its successful <br />establishment. <br />2. In mined -land reclamation it is important to have adequate herbaceous cover to <br />provide for erosion control. The reference areas at Colowyo indicate herbaceous <br />cover values of 41.8% and 30.17% for the mountain shrub and sage reference <br />areas, respectively. <br />Colowyo is located at approximately- 7,300 feet in elevation. The period of <br />highest potential erosion occurs in the springtime during snowmelt. At this time <br />of year, erosion control is provided almost exclusively by herbaceous vegetation. <br />Erosion control by shrub cover is virtually insignificant since the potential erosion <br />occurs from snowmelt rather than raindrop impact. Therefore, if pre- mining levels <br />of herbaceous vegetative cover can be re- established, logically a comparable level <br />of erosion control will be achieved. <br />3. The ability to achieve adequate levels of herbaceous cover at Colowyo is, without <br />question, quite possible. The vegetative monitoring completed at Colowyo during <br />the last three decades, and summarized in Annual Reports, indicates that the <br />premining levels of herbaceous cover are easily achieved. <br />In fact, the vegetative data as summarized in the Various Annual Reports indicate <br />that the levels of herbaceous cover on the reclaimed areas may have exceeded the <br />premine condition by 30% 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 <br />meets or exceeds the premining condition and is undoubtedly providing <br />significant competition with the woody specie seedlings. There is certainly no <br />evidence that herbaceous cover values on the reclaimed areas should be set higher <br />than the herbaceous cover of the premine areas in order to achieve bond release. <br />Herbaceous Production <br />For both Pre -2008 and Post -2008 revegetation (targeting (and achieving) the rangeland <br />land use subcomponent of rg azin lg and), herbaceous production of the revegetated area <br />will be considered adequate for final bond release if it is not less than 90% of the <br />herbaceous production, as determined from the reference areas with a 90% statistical <br />confidence utilizing a standard students statistical t -test comparison of the means. As <br />allowed under the rules promulgated on 9/14/05, these comparisons may utilize one of <br />three methods detailed under Rule 4.15.11 (2) [(a), (b) or (c)]. As allowed by Rule 4.15.7 <br />(4),, either weighted- average or individual protocols will be followed. For grassland <br />testing the weighted average approach (Rule 4.15.7 (4) (b)) will be utilized where <br />reference area data and reveg(Aated'area data are "weighted" (each combined into single <br />values for comparison) based on the proportional acreage of pre -mine communities <br />4.15 -24 Revision Date: 6/21/11 <br />Revision No.: TR -84 <br />