43 CFR § 3809.580
What happens if I modify my notice or approved plan of operations?
June 11, 2020
(a) If you modify a notice or an approved plan of operations under §3809.331 or §3809.431 respectively, and your estimated reclamation cost increases, you must increase the amount of the financial guarantee to cover any estimated additional cost of reclamation and long-term treatment in compliance with §3809.552.
(b) If you modify a notice or an approved plan of operations under §3809.331 or §3809.431 respectively, and your estimated reclamation cost decreases, you may request BLM decrease the amount of the financial guarantee for your operations.