16 Tex. Admin. Code § 12.503
When no longer needed for monitoring or other use approved by the Commission upon a finding of no adverse environmental or health and safety effects, or unless approved for transfer as a water well under § RSA 12.520 of this title (relating to Hydrologic Balance: Transfer of Wells), each shaft, drift, adit, tunnel, exploratory hole, entryway or other opening to the surface from underground shall be capped, sealed, backfilled, or otherwise properly managed, as required by the Commission in accordance with §§ RSA 12.501 and RSA 12.518 of this title (relating to Casing and Sealing of Underground Openings: General Requirements, and to Hydrologic Balance: Underground Mine Entry and Access Discharges) and consistent with RSA 75.1711. Permanent closure measures shall be designed to prevent access to the mine workings by people, livestock, fish and wildlife, machinery and to keep acid or other toxic drainage from entering ground or surface waters.
16 Tex. Admin. Code § 12.503