Cal. PRC § 3336

The supervisor upon his own motion may, or shall upon the application of any interested person, hold a public hearing for the purpose of determining and establishing the exterior boundaries encompassing the lands referred to in Section 3317. If, after a public hearing and from the evidence adduced therefrom, the supervisor determines that the lands, or a portion thereof, come within the category of those lands referred to in Section 3317, he shall adopt an order fixing and establishing the exterior boundaries thereof. The supervisor shall retain jurisdiction in this regard, and shall, if it be made to appear necessary, hold further hearings for the purpose of determining whether the boundaries previously established should be enlarged or otherwise altered. Any such change or alteration in said boundaries shall be made by order of the supervisor.