30 CFR 75.1711 : Mineral Resources (§ 1.1 To Parts 1291-1299) — (§ 1.1 To Parts 105-199) — Mine Safety And Health Administration, Department Of Labor (§ 1.1 To Parts 105-199) — Coal Mine Safety And Health (§ 70.1 To § 90.301) — Mandatory Safety Standards - Underground Coal Mines (§ 75.1 To § 75.1916) — Miscellaneous (§ 75.1700 To § 75.1732) — Sealing of mines.

On or after March 30, 1970, the opening of any coal mine that is declared inactive by the operator, or is permanently closed, or abandoned for more than 90 days, shall be sealed by the operator in a manner prescribed by the Secretary. Openings of all other mines shall be adequately protected in a manner prescribed by the Secretary to prevent entrance by unauthorized persons.