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RULE 4 PERFORMANCE STANDARDS <br />used rather than the 30cm. x 60 cm. frame used to gather baseline production data for the original permit <br />application. The use of a larger frame reduced the sampling variance, thus reducing the numbers of <br />samples needed to achieve sample adequacy. <br />The vegetative data is summarized on Table 4.15-5, Herbaceous Cover of the Sagebrush Type, Old <br />(1980) and New (1981) Reference Areas-and Table 4.15-6, Herbaceous Production of the Sagebrush <br />Type, Old (1980) and New (1981) Reference Areas. <br />For the location of the current sagebrush reference area, refer to Map 3, Regional Vegetation. <br />Currently the mountain shrub reference area is located in an area where grazing can be managed in <br />accordance with the approved postmining land use. <br />The reference areas will be fenced, as necessary, to insure that the proper grazing management can be <br />implemented. <br />Comparisons of weighted averages between reference areas and revegetated areas under Subsection <br />4.15.7(4) (b) will be utilized to determine revegetation success. The same methodologies and statistical <br />tests used to compare premine and reference areas will be used to compare reference areas and <br />revegetated areas. <br />4.15.8 Revegetation Success Criteria <br />Colowyo will meet the requirements of this Subsection to insure that the postmining vegetation will be <br />adequate for final bond release. <br />As delineated under Subsections 4.15.7 and 2.05.4, Colowyo will establish reference areas for the purpose <br />of comparing vegetation information between the reclaimed area and the undisturbed area. <br />Herbaceous Cover <br />Herbaceous cover of the revegetated area will be considered adequate for final bond release if it is not less <br />than 90% of the cover as determined from the reference areas with a 90% statistical confidence. <br />A higher percentage of herbaceous cover is not practical or desirable for the following reasons: <br />1. It is well documented that in the mountain shrub zone the establishment of shrubs to reach bond <br />release levels has proven to be very difficult. Perhaps the most detrimental condition effecting <br />shrub establishment is the competition from herbaceous vegetation. At a minimum herbaceous <br />cover levels should approximate the premining condition. If the herbaceous levels to be obtained <br />were set higher than the premining condition, the ability to achieve bond release levels for shrubs <br />would be most adversely effected. Higher levels of herbaceous cover would out compete the <br />woody vegetation and hinder its successful establishment. <br />2. In the mountain shrub zone it is important to have adequate herbaceous cover to provide for <br />erosion control. The reference areas at Colowyo indicate herbaceous cover values of 41.8% and <br />30.17% for the mountain shrub and sage reference areas, respectively. <br />Colowyo is located at approximately- 7,300 feet in elevation. The period of highest potential <br />erosion occurs in the springtime during snowmelt. At this time of year, erosion control is <br />provided almost exclusively by the herbaceous vegetation. Erosion control by the shrub cover is <br />Rule 4 Performance Standards 4.15-9 Revision Date: 6/23/08 <br />Revision No.: MR-91