43 CFR §3809.431

1. (a)Before making any changes to the operations described in your approved plan of operations;
2. (b)When BLM requires you to do so to prevent unnecessary or undue degradation; and
3. (c)Before final closure, to address impacts from unanticipated events or conditions or newly discovered circumstances or information, including the following:
   1. (1)Development of acid or toxic drainage;
   2. (2)Loss of surface springs or water supplies;
   3. (3)The need for long-term water treatment and site maintenance;
   4. (4)Repair of reclamation failures;
   5. (5)Plans for assuring the adequacy of containment structures and the integrity of closed waste units;
   6. (6)Providing for post-closure management; and (7) Eliminating hazards to public safety.