2010-11-01_REVISION - C1981019 (2)

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RULE 4 PERFORMANCE STANDARDS 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 difference, 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. As shown on Table 4.15-1, Herbaceous Cover of the Mountain Shrub Type - Premine and Reference Area; Table 4.15-2, Herbaceous Production of the Mountain Shrub Type - Premine and Reference Area; Table 4.15-3, Herbaceous Cover of the Sagebrush Type - Premine and Reference Area; and Table 4.15-4, Herbaceous Production of the Sagebrush Type - Premine and Reference Area, the reference area is statistically comparable to the premine areas for the parameters of cover and production. 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. For demonstration of revegetation success, vegetation cover, herbaceous production, and woody plant density will be sampled to statistical adequacy, and compared to the approved standard. The Division has completed a comprehensive bond release guideline that provides a good overview of recommended sampling approaches, statistical adequacy formulas and statistical tests. Colowyo will follow the procedures recommended in the guideline or utilize other procedures that are as affective as the Division's recommendations. Before Colowyo begins a vegetation sampling program for bond release, we will meet with the Division to discuss and confirm sampling approaches and statistical testing. 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. For demonstration of revegetation success, vegetation cover, herbaceous production, and woody plant density will be sampled to statistical adequacy, and compared to the approved standard. The Division has completed a comprehensive bond release guideline that provides a good overview of recommended sampling approaches, statistical adequacy formulas and statistical tests. Colowyo will follow the procedures recommended in the guideline or utilize other procedures that are as affective as the Division's recommendations. Before Colowyo begins a vegetation sampling program for bond release, we will meet with the Division to discuss and confirm sampling approaches and statistical testing. 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 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 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 Rule 4 Performance Standards 4.15-8 Revision Date: 10/27/10 Revision No.: MR-103