2009-06-24_PERMIT FILE - C1981019A (3)

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Statistical tests were performed on the vegetative data from the reference areas to prove that they were comparable to the premined area. The parameters compared were herbaceous cover and herbaceous production. Sample size adequacy tests were performed on both the premine and reference area data to insure that representative cover and production data had been obtained at the 80% level of confidence. Where necessary, the mean, variance and number of observations for the premine and reference area data were used to perform t-tests on the cover and production data to insure that there were no significant differences, at the 90% level of confidence, between the sets of cover data and production data. A copy of the transect data summaries for cover, production and woody plant density can be found in Exhibit 10, Vegetation Information. During the summer of 1980, when the reference areas were chosen, the final mine plan had not been completed and, the sagebrush reference area was inadvertently located within the area to be mined. Since the reference area is to remain undisturbed during the life of the mining- operation to insure that reclamation success criteria can be measured after final reclamation, another suitable sagebrush reference area was chosen. Since the initial sagebrush reference area had been shown to be statistically comparable to the premine sagebrush community, Colowyo located another sagebrush reference area which was statistically comparable to the existing reference area. This new (1981) reference area was intensively sampled for herbaceous cover and production, using the same sampling methodologies and statistical tests that were used to compare the present reference area to the premine area. On August 21, 1981 Colowyo submitted revised vegetative data summarizing the results of the selection of an alternative sagebrush reference area. Both the new (1981) sagebrush reference area and old sagebrush reference area were intensively sampled for herbaceous cover and production using the same methodologies and statistical tests as used on all previous vegetative sampling programs with the following two exceptions. For the purpose of sample adequacy, the 90% confidence level has been attained for cover and production, whereas, in the past the 80% confidence level had been attained. For production sampling, a larger 60cm. x 60cm. frame was used rather than the 30cm. x 60cm. frame used to gather baseline production data for the original permit application. The use of a larger frame reduced the sampling variance, thus reducing the numbers of samples needed to achieve sample adequacy. For the locations of the current (1981) Sagebrush Reference Area, (1980) Mountain Shrub Reference Area, and (1984) Aspen Reference Area, refer to Map 3, Regional Vegetation. The Sagebrush Reference Area is located north of the office / warehouse complex in the west 1/2 of Section 34, T4N R93W. The Mountain Shrub Reference Area is located on the crest and both east and west slopes of a ridge west of West Pit in the NE 4.15-13 Revision Date: 3/14/08 Revision No.: TR-72