312 IAC 25-6-98 Underground mining; disposal of underground development waste and excess spoil

Sec. 98. All excess underground development waste and spoil material resulting from coal mining and reclamation activities must be placed as follows: (1) Spoil shall be transported and placed in a controlled manner in position for concurrent compaction and to: (A) assure mass stability; (B) prevent mass movement; and (C) ensure a long term static safety factor of one and five-tenths (1.5). (2) The areas of disposal shall be within the bonded permit areas, and all organic matter shall be removed immediately before spoil placement. (3) Sufficient surface and internal drainage systems and diversion ditches shall be used to prevent spoil erosion and movement. (4) The disposal area shall not contain springs, natural water courses, or wet weather seeps unless lateral drains are constructed from the wet areas to the main underdrains to prevent infiltration of the water into the spoil pile. (5) If placed on a slope, the spoil shall be placed upon the most moderate slope available that the director determines will ensure compliance with IC 14-34. If possible, the spoil shall be placed upon or above a natural terrace, bench, or berm if this placement will provide additional stability and prevent mass movement. (6) Where the toe of the spoil rests on a downslope, a rock toe buttress of sufficient size to prevent mass movement shall be constructed. (7) The final configuration shall be compatible with the natural drainage pattern and surroundings and suitable for intended uses. Terraces may be constructed on the outslope of the bank or banks if required for stability, control of erosion, conservation of soil moisture, or facilitation of the approved postmining land use. The grade of the outslope between terrace benches shall not be steeper than fifty percent (50%), 2h:1v. (8) The spoil disposal area shall be designed under the supervision of, and certified after construction by, a qualified registered professional engineer as follows: (A) A qualified registered professional engineer, or other qualified professional specialist under the direction of the professional engineer, shall periodically inspect the fill during construction. The professional engineer or specialist must be experienced in the construction of earth and rock fills. (B) The inspections described in clause (A) must be made at least quarterly throughout construction and during critical construction periods. Examples of critical construction periods include the following: (i) Foundation preparation, including the removal of organic material and topsoil. (ii) The placement of underdrains and protective filter systems. (iii) The installation of final surface drainage systems. (iv) The placement and compaction of fill materials. (v) The establishment of the final graded and revegetated fill. (C) The registered professional engineer shall provide a report to the director promptly after each inspection performed under clause (B) that the fill has been constructed and maintained as designed and under the approved plan and this article. The report shall include appearances of instability, structural weakness, and other hazardous conditions. A report on any drainage system or protective filter shall include color photographs taken during and after construction (but before an underdrain is covered with excess spoil). The photographs must be taken in adequate size and number with enough terrain or other physical features of the site shown to provide a relative scale to the photographs and to specifically and clearly identify the site. If an underdrain system is constructed in phases, each phase shall be certified separately. (D) A copy of each inspection report shall be retained at or near the mine site. (9) The foundation and abutments of the fill shall be stable under all conditions of construction and operation. Sufficient foundation investigation and laboratory testing of foundation materials shall be performed to determine the design requirements for stability of the foundation. Analyses of foundation conditions shall include the effect of underground mine workings upon the stability of the structure. (10) Spoil shall be placed in horizontal lifts not exceeding four (4) feet thick, except where the director approves a greater thickness based upon a demonstration by the operator, and certification by a qualified registered professional engineer, that the design will ensure the stability of the fill and will meet all other applicable requirements. (11) No permanent impoundments shall be allowed on the completed fill. Small depressions may be allowed by the director if they are needed to retain moisture, minimize erosion, create and enhance wildlife habitat, or assist revegetation, and if they are not incompatible with the stability of the fill.