Tex. Natural Resources Code § 131.033: DIFFERING TERMS AND PROVISIONS OF RULES.

A rule or an amendment of a rule adopted by the commission may differ in its terms and provisions between particular conditions, particular mining techniques, particular areas of the state, or any other conditions that appear relevant and necessary so long as the action taken is consistent with attainment of the general intent and purposes of this chapter.

Acts 1977, 65th Leg., p. 2612, ch. 871, art. I, Sec. 1, eff. Sept. 1, 1977. Amended by Acts 1979, 66th Leg., p. 305, ch. 141, Sec. 39, eff. May 9, 1979; Acts 1979, 66th Leg., p. 849, ch. 379, Sec. 1, eff. June 6, 1979.