Code of Federal Regulations Title 43. Public Lands:  Interior § 43.3595.1 Surface openings

(a) The operator/lessee shall substantially fill in, fence, protect or close all surface openings, subsidence holes, surface excavations or workings which are a hazard to people or animals. Such protective measures shall be maintained in a secure condition during the term of the lease, license or permit. Before abandonment of operations, all openings, including water discharge points, shall be closed to the satisfaction of the authorized officer.

(b) Reclamation or protection of surface areas no longer needed for operations will commence without delay. The authorized officer shall designate such areas where restoration or protective measures, or both shall be taken.

(c) Wells utilized for operations involving solution mining or brine extraction shall be abandoned in accordance with the approved mine plan.