Except as provided in Regulation .05 of this chapter, excess spoil shall be placed in designated disposal areas within the permit area in a controlled manner to: Minimize the adverse effects of leachate and surface water runoff from the fill on surface and ground waters; Ensure mass stability and prevent mass movement during and after construction; and Ensure that the final fill is suitable for reclamation and revegetation compatible with the natural surroundings and the approved postmining land use. The fill and appurtenant structures shall be designed using current, prudent engineering practices and shall meet any design criteria established by the Bureau. A qualified registered professional engineer experienced in the design of earth and rock fills shall certify the design of the fill and appurtenant structures. All vegetative and organic materials shall be removed from the disposal area and disposed of in an approved manner and location. All topsoil shall be removed and handled in accordance with COMAR 26.20.25.02. Slope protection shall be provided to minimize surface erosion at the site. All disturbed areas, including diversion ditches that are not riprapped, shall be vegetated upon completion of construction. The disposal areas shall be located on the most moderately sloping and naturally stable areas available as approved by the Bureau. If the 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. The spoil shall be hauled or conveyed and placed in horizontal lifts not exceeding 4 feet in thickness in a controlled manner, concurrently compacted as necessary to ensure mass stability and prevent mass movement during and after construction, covered with topsoil or substitute material, 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. The Bureau may approve a design which incorporates placement of excess spoil in horizontal lifts other than 4 feet in thickness when it is demonstrated by the operator and certified by a qualified registered professional engineer that the design will ensure the stability of the fill and will meet all other applicable requirements. The final configuration of the fill shall be suitable for postmining land uses approved in accordance with the permit, except that no depressions or impoundments shall be allowed on the completed fill. Terraces may be constructed on the outslope of the fill if required for stability, control of erosion, to conserve soil moisture, or to facilitate the approved postmining land use. The grade of the outslope between terrace benches may not be steeper than 2:1 (50 percent). If the slope in the disposal area exceeds 2.8:1 keyway cuts (excavations to stable bedrock) or rock toe buttress shall be constructed to stabilize the fill. If the toe of the spoil rests on a downslope, stability analyses shall be performed to determine the size of rock toe buttresses and keyway cuts. Excess spoil that is acid-forming or toxic-forming or combustible shall be adequately covered with nonacid, nontoxic and noncombustible material, or treated to control the impact on surface and ground water in accordance with COMAR 26.20.20, to prevent sustained combustion, and to minimize adverse effects on plant growth and the approved postmining land use. 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 shall be experienced in the construction of earth and rock fills. The inspections shall be made at least quarterly throughout construction and during critical construction periods. Critical construction periods shall include at a minimum: Foundation preparation, including the removal of all organic material and topsoil; Placement of underdrains and protective filter systems; Installation of final surface drainage systems; and The final graded and revegetated fill. Regular inspections by the engineer or specialist shall also be conducted during placement and compaction of fill materials. The qualified registered professional engineer shall provide a certified report to the Bureau promptly after each inspection stating that the fill has been constructed and maintained as designed and in accordance with the approved plan and this chapter. The report shall include: Appearances of instability; Structural weakness; and Other hazardous conditions. 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. The photographs accompanying 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. A copy of each inspection report shall be retained at or near the mine site. Coal processing wastes may not be disposed of in head-of-hollow or valley fills, and may only be disposed of in other excess spoil fills if the waste is: Placed in accordance with the construction specifications; Demonstrated to be nontoxic and non-acid-forming; and Demonstrated to be consistent with the design stability of the fill. If the disposal area contains springs, natural or man-made water courses, 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. 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 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. Excess spoil may be returned to underground mine workings, but only in accordance with a disposal program approved by the Bureau and MSHA.