2020-05-13_REVISION - C1981010 (41)

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1.4 DETERMINATION OF BOND Trapper Mining Inc. presently maintains a reclamation performance bond for the Trapper Mine payable to the State of Colorado and the United States Office of Surface Mining Reclamation and Enforcement. Upon approval of this permit application, a performance bond or equivalent, acceptable surety will be secured in an amount equal to the estimated costs for returning the affected area to a satisfactory condition as defined by applicable regulations and this permit application. The equipment productivity estimates used in regrade time calculations were derived from the Caterpillar Performance Handbook, edition 47. Topsoil fleet hours were derived using TALPAC haulage simulation software. DRMS database ownership and operating costs were used where available; otherwise, these costs were extracted from Trapper Mining Inc. historical data and information obtained from Wagner Equipment Rentals. All reclamation costs were calculated according to the worst-case condition of reclamation requirements. The costs that were calculated in this manner realistically represent those the Division could incur at any time during the permit period, and not just for the conditions that may exist at the end of the five years. Appendix A Tables A-1 through A-14 summarize regrade, topsoil replacement, revegetation areas & costs, demolition, and miscellaneous costs associated with mine closure. The driving factor in determining the worst case year was the extent to which Nighthawk (N)-pit has been opened. This is a truck/Excavator, dozer, and dragline pit. During the proposed worst case year, which is estimated to be 2022, the depth and resulting volume of material required to backfill both N and L pits is at its maximum, with respect to the permit term. The projected volume of overburden replacement, which includes the dragline, dozer stripping, and truck/Excavator operations, is greatest in the year 2022 (see Table 1.4-2). The primary contributing factor to the increase in the projected Performance Bond for the worst case bond year of 2022 is the development of N Pit. This pit will be opened in 2020 with topsoil stripping operations and development of the initial boxcut at the west end of the pit(see "Trapper Worst Case Bond Year" narrative for a description of mining operations for the permit term). By 2022, N pit will have advanced to the point that the entire box-cut is open, with some additional pre-strip open, thus resulting in a substantial area of pit being open. In addition, highwall mining in the initial boxcut is in progress, which requires the delay of reclamation activities in this pit during this process. The Ash Pit is anticipated to still be receiving ash from Craig Station. There will be some reclamation done in the ash pit by 2022, but a significant portion of the pit will remain open beyond the permit term. Derringer/Enfield Pit, previously anticipated to receive ash, will be reclaimed in 2021 and 2022 and will not be included as part of the bond closure costs given in Table 1.4-1. As L pit advances eastward, the cuts tie into the cuts of the former East A (AE) pit. AE pit will be incorporated into L pit and will, therefore, no longer be referred to as a separate pit. Due to the pre-stripping operations with the Truck/Excavator fleet, combined with the dozer stripping and dragline operations, L pit's overall length and width, with respect to the five year permit term, is greatest in 2022 (see Table 1.4-2 and "Trapper Worst Case Bond Year' narrative for a description of mining operations for the permit term). revision- P2-Cri 1-31 Approved: