16 Tex. Admin. Code § 12.333
When no longer needed for monitoring or other use approved by the Commission upon a finding of no adverse environmental or health and safety effect, or unless approved for transfer as a water well under § RSA 12.351 of this title (relating to Hydrologic Balance: Transfer of Wells), each exploration hole, other drilled hole or borehole, well, and other exposed underground opening shall be capped, sealed, backfilled, or otherwise properly managed, as required by the Commission, under § RSA 12.331 of this title (relating to Casing and Sealing of Drilled Holes: General Requirements) 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, and machinery, and to keep acid or other toxic drainage from entering ground or surface waters.
16 Tex. Admin. Code § 12.333