(a) Underground development waste and spoil not required to achieve the approximate original contour and which is not used as backfill shall be hauled or conveyed to and placed in designated disposal areas within a permit area if the disposal areas are authorized for such purposes in the approved permit application in accordance with this section and §§12.532-12.534 of this title (relating to Disposal of Underground Development Waste and Excess Spoil: Valley Fills, to Disposal of Underground Development Waste and Excess Spoil: Head-of-Hollow fills, and to Disposal of Underground Development Waste and Excess Spoil: Durable Rock Fills). The material shall be placed in a controlled manner to ensure:
  (1) that leachate and surface runoff from the fill will not degrade surface or ground waters or exceed the effluent limitations referenced in §12.510 of this title (relating to Hydrologic Balance: Water-Quality Standards and Effluent Limitations);
  (2) stability of the fill; and
  (3) that the land mass designated as the disposal area is suitable for reclamation and revegetation compatible with the natural surroundings.
(b) The fill shall be designed using recognized professional standards, certified by a qualified professional engineer, and approved by the Commission.
(c) All vegetative and organic materials shall be removed from the disposal area and the topsoil shall be removed, segregated and stored or replaced in accordance with §§12.504-12.508 of this title (relating to Topsoil: General Requirements, to Topsoil: Removal, to Topsoil: Storage, to Topsoil: Redistribution, and to Topsoil: Nutrients and Soil Amendments). If approved by the Commission, organic material may be used as mulch or may be included in the topsoil to control erosion, promote growth of vegetation, or increase the moisture retention of the soil.
(d) Slope protection shall be provided to minimize surface erosion at the site. Diversion design shall conform with the requirements of §12.511 of this title (relating to Hydrologic Balance: Diversions). All disturbed areas, including diversion ditches that are not riprapped, shall be vegetated upon completion of construction.
(e) The disposal areas shall be located on the most moderately sloping and naturally stable areas available as approved by the Commission. If such placement provides additional stability and prevents mass movement, fill materials suitable for disposal shall be placed upon or above a natural terrace, bench, or berm.
(f) The fill materials shall be hauled or conveyed and placed in horizontal lifts in a controlled manner, concurrently compacted as necessary to ensure mass stability and prevent mass movement, covered, 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.
(g) The final configuration of the fill must be suitable for postmining land uses approved in accordance with §12.568 of this title (relating to Postmining Land Use), except that no depressions or impoundments shall be allowed on the completed fill.
(h) Terraces may be utilized to control erosion and enhance stability if approved by the Commission and consistent with §12.552(b) of this title (relating to Backfilling and Grading: General Grading Requirements).
(i) Where the slope in the disposal area exceeds 2.8h:1v (36%), or such lesser slope as may be designated by the Commission based on local conditions, keyway cuts (excavations to stable bedrock) or rock toe-buttresses shall be constructed to stabilize the fill. Where the toe of the spoil rests on a downslope, stability analyses shall be performed in accordance with §12.183 of this title (relating to Cross Sections, Maps, and Plans) to determine the size of the rock toe-buttresses or keyway cuts.
(j) The fill shall be inspected for stability by a qualified professional engineer experienced in the construction of earth and rockfill embankments at least quarterly throughout construction, and during the following critical construction periods:
  (1) removal of all organic material and topsoil;
  (2) placement of underdrainage systems and protective filter systems;
  (3) installation of surface drainage systems;
  (4) placement and compaction of fill materials; and
  (5) revegetation.
(k) The qualified professional engineer shall provide to the Commission a certified report, within two weeks after each inspection that the fill has been constructed as specified in the design approved by the Commission. The certified report on the drainage system and protective filters shall include color photographs taken during and after construction, but before underdrains are covered with excess spoil. If the underdrain system is constructed in phases, each phase shall be certified separately. A copy of the report shall be retained at the minesite.
(l) Coal mine waste shall not be disposed of in valley or head-of-hollow fills and may only be disposed of with underground development waste, or in other excess spoil fills, if such waste is:
  (1) placed in accordance with §12.538 of this title (relating to Coal Mine Waste Banks: Construction Requirements);
  (2) demonstrated to be non-toxic and non-acid forming; and
  (3) demonstrated to be consistent with the design stability of the fill.
(m) If the disposal area contains springs, natural or manmade watercourses, or wet-weather seeps, an underdrain system consisting of durable rock shall be constructed from the wet areas in a manner that prevents infiltration of the water into the spoil material. The underdrain system shall be protected by an adequate filter and shall be designed and constructed using standard geotechnical engineering methods. Where excess durable rock spoil is placed in single or multiple lifts such that the underdrain system is constructed simultaneously with excess spoil placement by the natural segregation of dumped materials, color photographs shall be taken of the underdrain as the underdrain system is being formed.
(n) The foundation and abutments of the fill shall be stable under all conditions of construction and operation. Sufficient foundation investigations and laboratory testing of foundation materials shall be performed in order to determine the design requirements for stability of the foundation. Analyses of foundation conditions shall include the effect of underground mine workings, if any, upon the stability of the structure.
(o) Underground development waste and excess spoil may be returned to underground workings only in accordance with the disposal plans submitted under §12.193 of this title (relating to Underground Development Waste/Return of Coal Processing Waste to Abandoned Underground Workings) and approved by the Commission and MSHA.
(p) Excess spoil that is acid-forming or toxic-forming or combustible shall be adequately covered with non-acid, non-toxic and noncombustible material, or treated, to control the impact on surface and ground water in accordance with this chapter (relating to Coal Mining Regulations), to prevent sustained combustion, and to minimize adverse effects on plant growth and the approved postmining land use.
(q) The photographs required by this section to accompany each certified report shall 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.

Source Note: The provisions of this §12.531 adopted to be effective April 7, 1997, 22 TexReg 3093; amended to be effective November 4, 1997, 22 TexReg 10640; amended to be effective December 28, 2020, 45 TexReg 9503