Administrative Rules of Montana
Department 17 - ENVIRONMENTAL QUALITY
Chapter 17.24 - RECLAMATION
Subchapter 17.24.9 - Strip and Underground Mine Reclamation Act: Underground Coal and Uranium Mining
Rule 17.24.924 - DISPOSAL OF UNDERGROUND DEVELOPMENT WASTE: GENERAL REQUIREMENTS
Current through Register Vol. 6, March 22, 2024
(1) To the extent that underground development waste is not proposed for backstowing, it must be demonstrated, to the satisfaction of the department, that valid physical, economic, safety, environmental or other reasons exist for not doing so. Underground development waste to be returned to underground mine workings must be disposed of in accordance with a program approved by the department and the mine safety and health administration.
(2) Underground development waste materials from activities located outside the permit area may be disposed of in the permit area only with approval of the department. Approval must be based upon a showing that disposal will be in accordance with this rule and all applicable rules.
(3) Underground development waste must be hauled or conveyed to and placed in designated disposal areas within a permit area. Underground development waste may not be placed in an impoundment or an embankment. The waste must be placed in a controlled manner to ensure:
(4)
(5) All vegetation and other organic materials must be removed from the disposal site and the soil must be removed, segregated, and stored or replaced pursuant to ARM 17.24.701 through 17.24.703. If approved by the department, organic material may be used as mulch or may be included in the soil to control erosion, promote growth of vegetation, or increase moisture retention of the soil.
(6) Slope protection must be provided to minimize surface erosion at the site. Diversions necessary to control erosion, prevent water infiltration, and ensure stability must be installed. Diversion design must conform with the requirements of ARM 17.24.635 through 17.24.637. All disturbed areas, including diversion ditches that are not riprapped, must be vegetated upon completion of construction.
(7) Except for head-of-hollow and valley fills, disposal structures must be located on the most moderately sloping and naturally stable areas available, except that the department may approve disposal in another area upon determining that disposal in that area would be more environmentally protective. Materials suitable for disposal must be placed upon or above a natural terrace, bench, or berm, if such placement provides additional stability and prevents mass movement.
(8) The waste must be hauled or conveyed and placed in horizontal lifts of not greater than four feet in thickness in a controlled manner, concurrently compacted as necessary to ensure mass stability and prevent mass movement, and graded to allow surface and subsurface drainage to be compatible with the natural surroundings and ensure a long-term static safety factor of 1.5.
(9) Following final grading of the waste disposal structure, the waste must be covered with a minimum of four feet of the best available non-toxic and non-combustible material, in a manner that does not impede drainage from the underdrains, unless the applicant demonstrates and the department finds that a lesser depth will provide for revegetation consistent with ARM 17.24.711, 17.24.713, 17.24.714, 17.24.716 through 17.24.718, 17.24.721, 17.24.723 through 17.24.726, and 17.24.731. Toxic, acid-forming, and other deleterious waste must be handled and covered in accordance with ARM 17.24.501(2) and 17.24.505(2).
(10) The final configuration of a structure must be suitable for postmining land uses approved in accordance with ARM 17.24.762, except that no depressions or impoundments may be placed on the completed structure.
(11) The final configuration of the structure must be designed to minimize erosion. Terraces may be utilized to control erosion and enhance stability if approved by the department. The outslope of the fill must not exceed 1v:3h, unless otherwise approved in writing by the department, but in no case may the outslope exceed 1v:2h.
(12) Where the natural slope of the disposal site exceeds 1v:3h, or such lesser slope as may be designated by the department based on local conditions, keyway cuts (excavations to stabilized bedrock) or rock toe buttresses must be constructed to stabilize the fill. Where the toe of the underground development waste rests on a downslope, stability analyses must be performed in accordance with ARM 17.24.320 to determine the size of the rock toe buttresses and keyway cuts.
(13) If the disposal site contains springs, natural or manmade watercourses, or wet-weather seeps, an underdrain system consisting of durable rock must be constructed in a manner that prevents infiltration of the water into the underground development waste material and to ensure stability of the disposal structure.
(14) The underdrain system for a structure must be constructed in accordance with the following:
Total amount of fill material | Predominant type of fill material | Minimum size of drain, in feet | |
Width | Height | ||
Less than 1,000,000 | |||
yd\ | sandstone | 10 | 4 |
yd\ | shale | 16 | 8 |
More than 1,000,000 | |||
yd\ | sandstone | 16 | 8 |
yd\ | shale | 16 | 16 |
(15) Drainage must not be directed over the outslope of the fill.
(16) Surface water runoff from the area above a structure must be diverted away from the structure and into stabilized diversion channels designed to pass safely the runoff from a 100-year, six-hour precipitation event or larger event specified by the department. Surface runoff from the structure surface must be diverted to stabilized channels off the fill that will safely pass the runoff from a 100-year, six-hour precipitation event. Diversion design must comply with the requirements of ARM 17.24.637.
(17) The foundation and abutments of a structure must be stable under all conditions of construction and operation. Sufficient foundation investigation and laboratory testing of foundation materials must be performed in order to determine the design requirements for stability of the foundation. Analyses of foundation conditions must include the effect of underground mine workings, if any, upon the stability of the structure.
(18)
(19) If any inspection discloses that a potential hazard exists, the department must be informed promptly of the finding and of the emergency procedures formulated for public protection and remedial action. If adequate procedures cannot be formulated or implemented, the department must be notified immediately. The department shall then notify the appropriate emergency agencies that other emergency procedures are required to protect the public. The department shall also notify the owner of land upon which the disposal structure is located (if that owner is different from the mining company), adjacent landowners, residences, and businesses that could be adversely affected, including those at least one mile down gradient from the disposal site, of the potential hazard and of the actions being taken.
(20) Disposal of underground waste by incorporation into spoils backfill of excavation areas must be in accordance with (3) and (19).
AUTH: 82-4-205, 82-4-231, MCA; IMP: 82-4-227, 82-4-231, 82-4-232, 82-4-233, MCA