The following special requirements apply whenever the affected area includes steep slopes: The permittee shall prevent the following materials from being placed or allowed to remain on the downslope: Spoil; Waste materials, including waste mineral matter; Debris, including that from clearing and grubbing of haul road construction; and Abandoned or disabled equipment. Nothing in §A of this regulation shall prohibit the placement of material in road embankments located on the downslope, so long as the material used and embankment design comply with the requirements of the Regulatory Program, and the material is moved and placed in a controlled manner. The permittee shall demonstrate to the Bureau, using standard geotechnical analysis, that the minimum static factor of safety for the stability of all portions of the reclaimed land is at least 1.5. Land above the highwall may not be disturbed, unless the Bureau finds that the disturbance assists compliance with the requirements of this regulation. Material in excess of that required by the grading and backfilling provisions shall be disposed of in accordance with the requirements of the Regulatory Program. Woody materials may not be buried in the backfilled area unless the Bureau determines that the proposed method for placing woody material beneath the highwall will not deteriorate the stable condition of the backfilled area. Woody materials may be chipped and distributed over the surface of the backfill as mulch, if special provision is made for their use and approved by the Bureau. Unlined or unprotected drainage channels may not be constructed on backfills unless approved by the Bureau as stable and not subject to erosion. In multiple-seam, steep slope affected areas, spoil not required to reclaim and restore the permit area may be placed on a preexisting bench, if approved by the Bureau and if the following requirements are met: All excess spoil shall be hauled, placed, and retained on the solid bench; The spoil shall be graded to a moderate slope, so as to eliminate the existing highwall to the extent possible with the available material; The fill shall comply with the Regulatory Program.