43 CFR § 3602.29
How will BLM verify my production?
June 11, 2020
(a) You must submit at least one report per contract year of the amount of mineral materials you have mined or removed under your sales contract so BLM can verify that you have made the required payments. BLM will specify the timing of the reports in your contract or permit.
(b) BLM may require more frequent reporting if we find it necessary.
(c) BLM may require you to conduct pre-operation, annual, and post-operation volumetric surveys of the mine site.