2013-04-10_GENERAL DOCUMENTS - C1981019

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areas will be no less than 90 percent as productive as the associated reference area with a 90 percent statistical confidence level. Herbaceous cover and production success for the "original" permit area disturbances and for the relatively limited acreage of disturbance projected for the Lower Wilson disturbance (120 acres approximate) will be based on acreage weighted comparisons, using the sagebrush and mountain shrub reference areas, in accordance with Rule 4.15.7(4)(b), as previously approved. The originally approved sagebrush reference area, established in 1981 within the original Colowyo permit area, will be utilized for a "targeted reference area" rather than a separate sagebrush reference area established in association with 1984 vegetation studies and located to the south of the South Taylor expansion area. Reasons for use of the original sagebrush reference area in preference to the 1984 reference area are set forth under Justification for Reference Area Selection - Sagebrush Reference Area, in Section 2.04. 10 of Volume 12, and discussed in Section 4.15 of the PAP. Three new reference areas have been established for reclamation success comparisons for the Collom expansion area. These are shown on Map 4C -Sheet 1, and discussed in Section 4.15 of Volume 15. The three new reference areas are a Mountain Shrub reference area, a Sagebrush reference area, and a Grassland reference area. CCC will use a weighted average of the three Collom reference areas for revegetation success comparison. Based upon pre- mining vegetation mapping of the proposed disturbance area, re- established grassland communities in the Collom expansion area will be compared to the weighted average comparison and will consist of 39% Mountain Shrub reference area, 47% Sagebrush reference area, and 14% Grassland reference area. Reclaimed areas in the Collom expansion area that evolve into a Sagebrush steppe community will be directly compared with the Sagebrush reference area. Targeted Grassland areas and targeted Sagebrush steppe areas reestablished on the reclaimed parcels of the Collom expansion area are determined by the variable topsoil replacement depth as described in Section XIII, part B of this findings document. Slopes steeper than 10% will be targeted as Grassland, using the approved Reclamation Seed Mixture (Table 2.05 -7). Reclaimed parcels with slopes equal to or less than 10% will be targeted as Sagebrush steppe and seeded with the approved Reclamation Seed Mixture (Table 2.05 -9). Diversity success criteria for areas at the East Pit, West Pit, Section 16 Pit, and South Taylor area were arrived at by utilizing herbaceous cover data from the pre- mining inventory. Four species were found to comprise 43.4 percent of the diversity: Poa pratensis, AgrQPyron smithii, Achillea lanulosa, and StiPa viridula, which represent three perennial, cool season grasses and one perennial forb. The revegetation objective for diversity is to establish a community on the reclaimed areas that contains the following: a) At least four principal species including a minimum of three cool season perennial grasses and a minimum of 1 perennial forb. b) Each principal species shall contribute no less than 3% relative cover. c) No single species shall contribute in excess of 50% relative cover Colowyo Coal Mine C1981 -019 PR -03 63 April 10, 2013