17.24.516 ADJACENT STRIP AND UNDERGROUND MINING OPERATIONS
(1) An operator who conducts a strip or underground mining operation adjacent to any active or abandoned underground mining operation, must comply with the following:
(a) A 500-foot barrier pillar of coal must be maintained between the strip and underground mining operations in any one seam. The department, the mine safety and health administration, and the Montana division of worker's compensation of the department of labor and industry, however, may approve a lesser distance after a finding by the department that mining at a lesser distance will result in:
(i) improved coal resources recovery;
(ii) abatement of water pollution; or
(iii) elimination of hazards to the health and safety of the public.
(b) The vertical distance between strip and underground mining operations working separate seams must be sufficient to provide for the health and safety of the workers and to prevent surface water from entering the underground workings.
(2) The operator must also comply with ARM 17.24.632.