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• 1.4.1 Regrading <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 Table 1.4 -2. <br />Supporting calculations are shown in Tables 1.4 -3 to 1.4 -7. <br />1.4.1.1 Pit Regrading <br />The pit regrading costs for Trapper Mine include the current ash disposal area, active <br />pits, and the final cut where Derringer and Enfield pits come together. The final cut in D <br />and E pits has been permitted as an ash disposal area. For reclamation .liability <br />purposes, it is assumed that there is no ash in the D/E ash disposal area. <br />Conceptually, the backf€lling of the open pits would be accomplished by blasting and <br />reducing highwalls, and by using spoils from previous cuts. 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 <br />Mincom software, and are a relatively accurate depiction of pit geometry before regrade. <br />The cross sectional areas were applied to incremental pit lengths for the worst case year <br />of 2012. The number of cross sections constructed for each pit depended upon the total <br />pit length, and the variability of overburden and interburden depths to a linear change in <br />depth. <br />• Dozers would do the backfilling and grading as this is the most cost efficient equipment <br />other than draglines, given the average distances calculated. Caterpillar D11R dozers <br />were selected as the most efficient equipment to complete the regrading task. Backfllling <br />in K pit will be accomplished mostly with a truck/excavator fleet. No scraper work was <br />required to backfill the pits, or to insure drainage. <br />Pits will generally be backfllled using spoil material currently available within existing <br />spoil rows associated with each pit. Appendix A provides appropriate cross sections of <br />existing and regraded post -mine topography. <br />• <br />Rev €s€ow - �- <br />1 -33 App roved '-_._ <br />