1993-11-26_GENERAL DOCUMENTS - C1981025

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Proposed Decision -North Thompson Creek/Phase II Bond Release November 26, 1993 Page 3 MINREC prepared a sediment analysis using the Universal Soil Loss Equation (USLE-. Vegetative cover information was derived from a vegetation survey conducted in July 1992, which is located in Appendix 3-W of the permit application package. Implementa- tion of the USLE showed that the reclaimed mine site is expected to lose approximately 0.31 tons of sediment per year due to erosion as compared with approximately 0.33 tons per year for the undisturbed extended reference area adjacent to the mine site. The Division's review of the calculations verified their accuracy. However, as vegetative cover is a parameter of the USLE, and no vegetative samples were collected in the area directly in front of the No. 1 Mine portal, the conclusions of the USLE calculations cannot be applied to this area. The Division has required straw bale treatment along the bank of North Thompson Creek to prevent excessive loading of sediment from the portal area to the creek. This treatment will remain in place until the operator demonstrates that vegetative cover in the No. 1 Mine portal area is sufficient to prevent excessive sediment loading to North Thompson Creek, thereby eliminating the need for the straw bale treat- ment. Because of deficiency of cover data in the No. 1 Mine portal area, the first condition for Phase II Bond Release has not been met for that portion of the mine. The second condition which must be met for Phase II Bond Release regards the successful establishment of vegetation. The North Thompson Creek mine permit requires that revegetated disturbed areas of the mine be compared to an extended reference area in the adjacent mountain shrubland vegetation community as a means of determining successful establishment of vegetation. The permit also includes a diversity standard which requires a minimum of three cool season grasses, two fortis and three shrubs or trees, each comprising between 3% and 40% of the relative cover of the reestablished vegetative community. Rule 3.03.1(2)(b) states that up to 85°,6 of applicable bond may be released upon the successful establishment of vegetation in accordance with the approved reclamation plan. Successful establishment of vegetation at this site is accomplished when vegetative cover of the reclaimed area is at least 90% of the vegetative cover in the reference area and when reasonable progress toward meeting the approved diversity standard has occurred. Because the unit train loadout has been excluded from this bond release, only revegetation at the mine site was evaluated in terms of successful establishment. The mine site consists of four disturbed areas, which are:' No. 1 Mine 20 acres No. 3 Mine 4 acres Refuse Disposal Area 10 acres Fan Portal 1 acre All four of these areas were reseeded during 1986 and 1987. The post-mining land use of all of the areas is rangeland/wildlife habitat. All of the disturbed surface area is owned by the Korth Thompson-Four Mile Land and Mineral Corporation. The refuse area and the No. 1 Mine are contiguous parcels of land. The No. 3 Mine disturbance is approximately