PERMFILE110122 - Laserfiche WebLink

Home Browse Search

The highwall reduction area and spoil will be worked together to shape and blend the material into the • natural topography, creating a transition that prevents drainage from creating knidcpoints, propagating natural undisturbed slopes, and enhancing the post mining land use. The postmining topography in the North Valore Pit has been modified to accommodate both ongoing backfilling and grading in this area and establishment of the alternate haul road necessary to replace the lower portion of Haul Road D, which has been impacted by the stability problems above Pond 012. By shifting a portion of Postmining Channel YPM•7 to the north (above the haul road corridor) backf lling, grading, and drainage channel wnstruction in the upper portions of the North Valora Pit can proceed without further delay. The final slope configuration in the lower portion of the North Valore Pit cannot be completed unti12007 when the haul road is removed and lower end of Channel YPM~ is constructed (the material removed from the haul road and channel area will need to be placed against the norfhem side slope to achieve PMT). See F~rhibit 19-1A, Backfilling and Grading Plan, for location of this variance area and reclamation schedule. The localized change in postmining topography results in steepening (from approximately 4.9:1 to 3.5:1) of an 600' section of the slope along the north highwall, but generally maintains the overall gradient of Postmining Channel YPM-7. The new 3.5:1 slope is well below the natural angle of repose for spoil materials, is compatible with the objective of long-tens slope stability and existing natural slopes in the area, and meets the applicable general grading requirements of Rule 4.14.2(1)(b). • SCC recognizes that post-reclamation natural settlement has the potential to result in limited exposure of portions of the North Valora Pit highwall. SCC will address the settlement and highwall exposure concern by monitoring this area for settlement, surface cracks, and any highwall exposures. It is anticipated that any surface cracks or highwall exposures that may occur will be localized and of limited extent and can be repaired by minor regrading and reseeding. Thin or thick overburden as defined by Section 4.14.4 and 4.14.5 does not exist at the Yoast Mine. The final volume is greater than 0.8 of the initial volume, therefore the thin overburden criteria is not applicable. The thick overburden rule does not apply because the final volume is not greater than 12 of the initial volume. Please refer to the volume calculations on Table 20-1, Post Mining Landfonn Mass Balance. Box cut spoil will initially be placed onto unmined land as described in Tab 12, Coal Resource Recovery Plan. This material will be rehandled when the dragline returns to the box cut area(s). Portions of box cut spoil will be temporarily stored in approved locations above the highwall for badcfill into portions of the final pits. All vegetative and organic material and topsoil will be removed from the area where box cut spoil is placed, and the spoil graded both into the mined area and blended into the surrounding terrain. No material shortages or excessive disturbed areas are anticipated in the area of the final highwall or major spoil excesses in the box cut area. This can be determined by reviewing Exhibit 12-1, Operations Plan, and the pre- and post mining topography slopes as shown on Exhibit 20-2A, Pre-Mining and Post Mining Cross- sections. • TR-25 2 Revised 6/04