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RULE 4 PERFORMANCE STANDARDS <br />Where necessary, the mean, variance and number of observations for the premine and reference <br />area data were used to perform t-tests on the cover and production data to insure that there were <br />no significant differences, at the 90% level of confidence, between the sets of cover data and <br />production data. <br />A copy of the transect data summaries for cover, production and woody plant density can be found <br />in Exhibit 10, Vegetation Information. <br />During the summer of 1980, when the reference areas were chosen, the final mine plan had not <br />been completed and, the sagebrush reference area was inadvertently located within the area to be <br />mined. Since the reference area is to remain undisturbed during the life of the mining- operation <br />to insure that reclamation success criteria can be measured after final reclamation, another suitable <br />sagebrush reference area was chosen. <br />Since the initial sagebrush reference area had been shown to be statistically comparable to the <br />premine sagebrush community, Colowyo located another sagebrush reference area which was <br />statistically comparable to the existing reference area. This new (1981) reference area was <br />intensively sampled for herbaceous cover and production, using the same sampling methodologies <br />and statistical tests that were used to compare the present reference area to the premine area. On <br />August 21, 1981 Colowyo submitted revised vegetative data summarizing the results of the <br />selection of an alternative sagebrush reference area. <br />Both the new (198 1) sagebrush reference area and old sagebrush reference area were intensively <br />sampled for herbaceous cover and production using the same methodologies and statistical tests <br />as used on all previous vegetative sampling programs with the following two exceptions. For the <br />purpose of sample adequacy, the 90% confidence level has been attained for cover and production, <br />whereas, in the past the 80% confidence level had been attained. For production sampling, a larger <br />60cm. x 60cm. frame was used rather than the 30cm. x 60cm. frame used to gather baseline <br />production data for the original permit application. The use of a larger frame reduced the sampling <br />variance, thus reducing the numbers of samples needed to achieve sample adequacy. <br />For the locations of the current (1981) Sagebrush Reference Area, (1980) Mountain Shrub <br />Reference Area, and (1984) Aspen Reference Area, refer to Map 3, Regional Vegetation. The <br />Sagebrush Reference Area is located north of the office / warehouse complex in the west 1/2 of <br />Section 34, T4N R93W. The Mountain Shrub Reference Area is located on the crest and both east <br />and west slopes of a ridge west of West Pit in the NE 1/4 of the NE 1/4 of Section 8 and the NW <br />1/4 of the NW 1/4 of Section 9, T4N R93W. The Aspen Reference Area is located approximately <br />4 miles to the SSW of the South Taylor Area in the SE 1/4 of Section 1, T2N R94W and the SW <br />1/4 of Section 6, T2N R93W. <br />Currently the reference areas are located in an area where grazing can be managed in accordance <br />with the approved postmining land use. <br />Comparisons of weighted averages between reference areas and revegetated areas under <br />Subsection 4.15.7(4) (b) and Subsection 4.15.11 may be utilized to determine revegetation success. <br />Similar methodologies and statistical tests used to compare premine and reference areas will be <br />Rule 4 Performance Standards 4-62 Revision Date: 5/25/18 <br />Revision No.: RN -07 <br />