(1) In addition to all appropriate requirements of subchapters 4 through 8, and 10 through 13, except ARM 17.24.519 and as provided in ARM 17.24.905, the following requirements apply to underground mining operations:

(a) Each prospecting hole, other drill hole or borehole, shaft, well, or other exposed underground opening must be cased, lined, or otherwise managed as approved by the department to prevent acid or other toxic drainage from entering ground and surface waters, to minimize disturbance to the prevailing hydrologic balance and to ensure the safety of people, livestock, fish and wildlife, and machinery in the mine plan and adjacent area, and the safety and integrity of underground mines in the area, present and future. Each prospecting hole, drill hole, borehole, or well that is uncovered or exposed by mining operations must be permanently sealed, in compliance with ARM 17.24.1005, unless approved for water monitoring or otherwise managed in a manner approved by the department. Use of a drilled hole or monitoring well as a water well must meet the provisions of ARM 17.24.647. This rule does not apply to holes drilled and used for blasting in the area affected by surface operations.

(b) Each mine entry, open to the surface, that is temporarily inactive, but has a further projected useful service under the approved permit application, must be protected by barricades or other covering devices, fenced, and posted with signs to prevent access into the entry and to identify the hazardous nature of the opening. These devices must be periodically inspected and maintained in good operating condition by the operator.

(c) Each prospecting hole, other drill hole or borehole, shaft, well, and other exposed underground opening that has been identified in the approved permit application for use to return underground development waste, coal processing waste, water to underground workings, or to be used to monitor ground water conditions, must be temporarily sealed until actual use.

(d) When no longer needed for monitoring or other use approved by the department and upon a finding of no adverse environmental or health and safety effects, each shaft, drift, adit, tunnel, prospecting hole, entry way or other opening to the surface from underground must be capped, sealed, backfilled, or otherwise properly managed, as required by the department in accordance with (1)(a), (g), (h), and (i). Permanent closure measures must be designed to prevent access to the mine workings by people, livestock, fish, wildlife, and machinery and to keep acid or other toxic drainage from entering ground or surface waters.

(e) In addition to the measures identified in ARM 17.24.631 through 17.24.646, the following practices are acceptable for minimizing water pollution in underground mines:

(i) designing mines to prevent gravity drainage of acid waters;

(ii) sealing;

(iii) controlling subsidence; and

(iv) preventing acid mine drainage;

(f) In addition to the requirements of ARM 17.24.633(1), any discharge of water from underground workings to surface waters that does not meet the effluent limitations of ARM 17.24.633 must also be passed through a sedimentation pond, a series of sedimentation ponds, or a treatment facility before leaving the permit area.

(g) In addition to the requirements of ARM 17.24.633(2), sedimentation ponds and treatment facilities that receive discharges from underground workings must be maintained until the discharge continuously meets the effluent limitations of ARM 17.24.633 without treatment or until the discharge has permanently ceased.

(h) Surface entries and accesses to underground workings, including adits and slopes, must be located, designed, constructed, and utilized to prevent or control gravity discharge of water from the mine.

(i) Gravity discharge of water from an underground mine, other than a drift mine in an acid-producing or iron-producing coal seam, may be allowed by the department, if it is demonstrated that:

(i)(A) the discharge, without treatment, satisfies the water effluent limitations of ARM 17.24.633 and all applicable state and federal water quality standards; and

(B) any changes in the prevailing hydrologic balance are minimal and the approved postmining land uses will not be adversely affected; or,

(ii)(A) the discharge is conveyed to a treatment facility in the permit area in accordance with ARM 17.24.633 through 17.24.640;

(B) all water from the underground mine discharged from the treatment facility meets the effluent limitations of ARM 17.24.633 and all other applicable state and federal statutes and regulations; and

(C) consistent maintenance of the treatment facility will occur throughout the anticipated period of gravity discharge;

(j) For a drift mine located in acid-producing or iron-producing coal seams, surface entries and accesses must be located in such a manner as to prevent any gravity discharge from the mine.

(2) Adversely affected water supplies must be replaced in accordance with 82-4-243 and 82-4-253, MCA, and ARM 17.24.648.


History: 82-4-205, 82-4-207, MCA; IMP, 82-4-227, 82-4-231, 82-4-232, 82-4-233, 82-4-243, 82-4-253, MCA; NEW, 1980 MAR p. 725, Eff. 4/1/80; AMD, 1989 MAR p. 30, Eff. 1/13/89; TRANS, from DSL, 1996 MAR p. 2852; AMD, 1999 MAR p. 811, Eff. 4/23/99; AMD, 2004 MAR p. 2548, Eff. 10/22/04; AMD, 2012 MAR p. 1617, Eff. 8/10/12; AMD, 2024 MAR p. 258, Eff. 2/10/24.