30 C.F.R. § 550.121
What must I do to protect health, safety, property, and the environment?
The Director may require additional measures to ensure the use of Best Available and Safest Technology (BAST) as identified by BSEE:
(a) To avoid the failure of equipment that would have a significant effect on safety, health, or the environment;
(b) If it is economically feasible; and
(c) If the incremental benefits justify the incremental costs.