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<br />A summary of the estimated mine closure cost is presented in Table 1.4-1. Please refer to
<br />Map M6 for the post mining topography of the worst-case bond year (2023) and to
<br />subsequent tables and sections in Appendix A of the permit application as indicated in Table
<br />1.4-1 for more detailed analysis and discussion.
<br />
<br />The bond amount of $44,979,268 will be applied to our permit revision (PR11). This cost
<br />represents the worst-case year, with respect to final reclamation, for the period 2023-2027.
<br />Trapper estimates that during the worst-case year of 2023, the total disturbance within the
<br />approved permit area will be 2,307.8 acres, which includes miscellaneous areas such as
<br />light use roads and silo locations.
<br />
<br />The increase in the bond amount is due mainly to the development of C, I, and J pits in the
<br />west panel of Trapper’s permit area. However, the bond estimate also includes the more
<br />expansive nature of Trapper’s current mining methods, regarding the combined dragline,
<br />dozer stripping, and pre-stripping by the Truck/Excavator operations. These operations
<br />contribute significantly, as well as the re-introduction of D/E Pit reclamation costs into the
<br />Bond estimate. The 2022 reclamation of D/E Pit will not be completed as forecasted in the
<br />PR9, and PR10 revisions, therefore, this cost has been added back into the Performance
<br />Bond estimate to account for this activity in the next permit term.
<br />
<br />1.4.1 Regrading
<br />
<br />Regrading would be the initial reclamation activity conducted at a mine if the operator
<br />permanently ceased operations. The areas requiring regrade at Trapper Mine, if this
<br />improbable event occurred, would be the open pits and associated spoil piles, roadways,
<br />impoundments, and ash disposal area. Regrade costs are summarized in Appendix A, Table
<br />A-3. Supporting calculations are shown in Tables A-4.1 through A-4.8.
<br />
<br />1.4.1.1 Pit Regrading
<br />
<br />The pit regrading costs for Trapper Mine include the Ash, Colt (C), Derringer (D), Ithaca (I),
<br />Jennings (J), Lancaster (L), and Nighthawk (N) pit areas.
<br />
<br />Conceptually, the backfilling of the open pits would be accomplished mainly through grading
<br />of highwalls and spoils with dozers. Colt, Jennings, Ithaca, Lancaster, and Nighthawk pits
<br />would also include truck//excavator backfilling. The Ash Pit, Jennings West, and Lancaster
<br />pits would require some blasting and highwall reduction. The cross sections used to
<br />calculate the volumes shown for all pits in the regrade tables are included in Appendix A.
<br />The spoil diagrams that are the basis of the regrade sections were developed using Mincom
<br />software, and are a relatively accurate depiction of pit geometry before regrade. The cross-
<br />sectional areas were applied to incremental pit lengths for the worst-case year of 2023. The
<br />number of cross sections constructed for each pit depended upon the total pit length, and
<br />the variability of overburden and interburden depths. Dozers would do the backfilling and
<br />grading as this is the most cost-efficient equipment, other than draglines, given the average
<br />distances calculated. Caterpillar D11T dozers were selected as the most efficient
<br />equipment to complete the regrading task. Additional truck/excavator work was required to
<br />backfill the Ash, Colt, Ithaca, Lancaster, and Nighthawk pits, and to insure positive drainage.
<br />
<br />Pits will generally be backfilled using spoil material currently available within existing spoil
<br />rows associated with each pit. In C, I, J, and N pits, a temporary spoil pile will be utilized for
<br />final backfill placement. Appendix A provides appropriate cross sections of existing and
<br />regraded post-mine topography.
<br />
<br />1-34
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