Tex. Natural Resources Code § 134.108

(a) An operator of a steep slope surface coal mining operation, in addition to meeting the general performance standards of this subchapter:

(1) shall ensure that during surface coal mining on steep slopes, debris, abandoned or disabled equipment, spoil material, or waste mineral matter is not placed on the downslope below the bench or mining cut;

(2) shall backfill with spoil material to:

(A) return the site to the approximate original contour; and

(B) maintain the stability of the material after mining and reclamation; and

(3) may not disturb land above the top of the highwall.

(b) Notwithstanding Subsection (a)(1), the operator shall permanently store under Section 134.106 spoil material in excess of that required to reconstruct the approximate original contour under Section 134.092(a)(3) or Subsection (a)(2).

(c) Notwithstanding Subsection (a)(3), the operator may disturb land above the top of the highwall if the commission finds that the disturbance will facilitate compliance with the environmental protection standards of this subchapter. The amount of land disturbed above the highwall may not exceed the amount necessary to facilitate the compliance.

(d) This section does not apply to an operator who:

(1) is mining on flat or gently rolling terrain on which an occasional steep slope is encountered through which the mining operations are to proceed, leaving a plain or predominantly flat area; or

(2) meets the requirements of Section 134.107.

(e) In this section, "steep slope" means a slope:

(1) that exceeds 20 degrees; or

(2) less than or equal to 20 degrees determined by the commission to be a steep slope after considering soil, climate, or other characteristics of the region or the state.