Section 816.99 - Slides and other damage(a) An undisturbed natural barrier shall be provided beginning at the elevation of the lowest coal seam to be mined and extending from the outslope for such distance as may be determined by the regulatory authority as is needed to assure stability. The barrier shall be retained in place to prevent slides and erosion.(b) At any time a slide occurs which may have a potential adverse affect on public property, health, safety, or the environment, the person who conducts the surface mining activities shall notify the regulatory authority by the fastest available means and comply with any remedial measures required by the regulatory authority.44 FR 15395, Mar. 13, 1979, as amended at 81 FR 93392 , Dec. 20, 2016; 82 FR 54979 , Nov. 17, 2017