43 CFR 4150.4-1: -1 Notice of intent to impound.

(a) A written notice of intent to impound shall be sent by certified mail or personally delivered to the owner or his agent, or both. The written notice shall indicate that unauthorized livestock on the specified public lands or other lands under Bureau of Land Management control, or both, may be impounded any time after 5 days from delivery of the notice.

(b) Where the owner and his agent are unknown, or where both a known owner and his agent refuses to accept delivery, a notice of intent to impound shall be published in a local newspaper and posted at the county courthouse and a post office near the public land involved. The notice shall indicate that unauthorized livestock on the specified public lands or other lands under Bureau of Land Management control, or both, may be impounded any time after 5 days from publishing and posting the notice.