Authority: IC 14-34-2-1

Affected: IC 14-34

Sec. 50. (a) Disturbed areas shall be backfilled and graded to include the following:

1. (1) Achieve the approximate original contour, except as provided in subsection (k).
2. (2) Eliminate all highwalls, spoil piles, and depressions, except as provided in subsections (h) and (k)(2).
3. (3) Achieve a postmining slope that does not exceed 3:1 (h:v) or the lesser slope that is needed to achieve a minimum long term static safety factor of one and three-tenths (1.3) and to prevent slides. This requirement does not apply to ditches, dams, levees, and similar constructed features.
4. (4) Minimize erosion and water pollution both on and off the site.
5. (5) Support the approved postmining land use.

(b) Spoil, except excess spoil disposed under subsection (d) or section 34 of this rule, shall be returned to the mined-out area.

(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 bonded, permitted area outside the mined-out 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. (1) All vegetative and organic material is removed from the area.
2. (2) The topsoil on the area is removed, segregated, stored, and redistributed under section 11 of this rule.
3. (3) The spoil is backfilled and graded on the area under this section.

(e) Disposal of coal processing waste and underground development waste in the mined-out area shall be under sections 36 through 38 of this rule, except that a long term static safety factor of one and three-tenths (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 noncombustible earthen material, or treated, to control the impact of surface and ground water under section 12 of this rule to prevent sustained combustion and to minimize adverse effects on plant growth and the approved postmining land use.

(g) The director may approve as a term of a permit the construction of cut-and-fill terraces if the permittee demonstrates either of the following:

1. (1) That the terraces are needed to conserve soil moisture, ensure stability, and control erosion on final-graded slopes if the terraces are compatible with the approved postmining land use.
2. (2) Specialized grading, foundation conditions, or roads are required for the approved postmining land use. Final grading under this subdivision 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 (which do not interfere with the approved postmining land use) may be constructed if needed to retain moisture, minimize erosion, create and enhance wildlife habitat, or assist revegetation.

(i) Permanent impoundments may remain if authorized by the director under section 20 of this rule.

(j) Preparation of final-graded surfaces shall be conducted to minimize erosion and to provide a surface for replacement of topsoil that will minimize slippage.

(k) The postmining slope may vary from the approximate original contour if:

1. (1) approval is obtained from the director in the approved permit application for a variance from approximate original contour requirements under 312 IAC 25-4-101;
2. (2) incomplete elimination of highwalls in previously disturbed areas is approved under subsection (l); or
3. (3) the standards for thick overburden in section 52 of this rule are met.

(l) If sufficient spoil is not otherwise available to comply with this section, the director may approve as a term of a permit a modification of the requirements of this section under section 144 of this rule for surface mining operations that affect previously mined lands that:

1. (1) contain a preexisting highwall; and
2. (2) have not been restored to the standards of this section.

(Natural Resources Commission; 312 IAC 25-6-50; filed Jun 21, 2001, 2:53 p.m.: 24 IR 3534, eff Dec 1, 2001; readopted filed May 29, 2007, 9:51 a.m.: 20070613-IR-312070146RFA; readopted filed Sep 19, 2013, 10:12 a.m.: 20131016-IR-312130125RFA; readopted filed Mar 26, 2019, 3:40 p.m.: 20190424-IR-312190011RFA; readopted filed Mar 25, 2025, 9:50 a.m.: 20250423-IR-312240574RFA)