30 CFR § 817.102 - Backfilling and grading: General requirements.
(a) Disturbed areas shall be backfilled and graded to -
(2) Eliminate all highwalls, spoil piles, and depressions, except as provided in paragraph (h) (small depressions) and in paragraph (k)(2) (previously mined highwalls) of this section;
(4) Minimize erosion and water pollution both on and off the site; and
(5) Support the approved postmining land use.
(c) Spoil and waste materials shall be compacted where advisable to ensure stability or to prevent leaching of toxic materials.
(d) Spoil may be placed on the area outside the mined-out surface area in nonsteep slope areas to restore the approximate original contour by blending the spoil into the surrounding terrain if the following requirements are met:
(1) All vegetative and organic material shall be removed from the area.
(3) The spoil shall be backfilled and graded on the area in accordance with the requirements of this section.
(e) Disposal of coal processing waste and underground development waste in the mined-out surface area shall be in accordance with §§ 817.81 and 817.83, except that a long-term static safety factor of 1.3 shall be achieved.
(f) Exposed coal seams, acid- and toxic-forming materials, and combustible materials exposed, used, or produced during mining shall be adequately covered with nontoxic and non combustible materials, or treated, to control the impact on surface and ground water in accordance with § 817.41, to prevent sustained combustion, and to minimize adverse effects on plant growth and the approved postmining land use.
(g) Cut-and-fill terraces may be allowed by the regulatory authority where -
(2) Specialized grading, foundation conditions, or roads are required for the approved postmining land use, in which case the final grading may include a terrace of adequate width to ensure the safety, stability, and erosion control necessary to implement the postmining land-use plan.
(h) Small depressions may be constructed if they are needed to retain moisture, minimize erosion, create and enhance wildlife habitat, or assist revegetation.
(j) Preparation of final-graded surfaces shall be conducted in a manner that minimizes erosion and provides a surface for replacement of topsoil that will minimize slippage.
(l) Regrading of settled and revegetated fills to achieve approximate original contour at the conclusion of underground mining activities shall not be required if the conditions of paragraph (l)(1) or (l)(2) of this section are met.
(iii) Stability of the spoil or underground development waste shall be demonstrated through standard geotechnical analysis to be consistent with backfilling and grading requirements for material on the solid bench (1.3 static safety factor) or excess spoil requirements for material not placed on a solid bench (1.5 static safety factor).
(2) If it is determined by the regulatory authority that disturbance of the existing spoil or underground development waste would increase environmental harm or adversely affect the health and safety of the public, the regulatory authority may allow the existing spoil or underground development waste pile to remain in place. The regulatory authority may require stabilization of such spoil or underground development waste in accordance with the requirements of paragraphs (l)(1)(i) through (l)(1)(iv) of this section.