(b) The highwall elimination requirements of § 816.102(a) of this part do not apply to remining operations for which you demonstrate in writing, to the regulatory authority's satisfaction, that the volume of all reasonably available spoil is insufficient to completely backfill the reaffected or enlarged highwall. Instead, for those operations, you must eliminate the highwall to the maximum extent technically practical in accordance with the following criteria:

1. (1) You must use all spoil generated by the remining operation and any other reasonably available spoil to backfill the area. You must include reasonably available spoil in the immediate vicinity of the remining operation within the permit area.
2. (2) You must grade the backfilled area to a slope that is compatible with the approved postmining land use and that provides adequate drainage and long-term stability.
3. (3) Any highwall remnant must be stable and not pose a hazard to the public health and safety or to the environment. You must demonstrate, to the satisfaction of the regulatory authority, that the highwall remnant is stable.
4. (4) You must not disturb spoil placed on the outslope during previous mining operations if disturbance would cause instability of the remaining spoil or otherwise increase the hazard to the public health and safety or to the environment.