43 CFR § 3809.21 - When do I have to submit a notice?
(a) You must submit a complete notice of your operations 15 calendar days before you commence exploration causing surface disturbance of 5 acres or less of public lands on which reclamation has not been completed. See § 3809.301 for information on what you must include in your notice.
(b) You must not segment a project area by filing a series of notices for the purpose of avoiding filing a plan of operations. See §§ 3809.300 through 3809.336 for regulations applicable to notice-level operations.