Each notice or order to be given or made under this chapter shall be served upon the person occupying the premises upon which the public nuisance exists, or if no person occupies the premises, the notice or order shall be posted upon the premises in a conspicuous place, and in addition, a copy of the notice or order shall be served on the property owner of the premises. Service of each notice or order shall be made upon all persons entitled thereto either personally or by mailing a copy of notice or order by certified mail, postage prepaid, return receipt requested, to each such person at his address as it appears on the last equalized assessment roll of the County or as known to the District Engineer. If no address of any such person so appears or is known to the District Engineer, then a copy of the notice or order shall be so mailed, addressed to such person at the address of the premises. The failure of any such person to receive such notice or order shall not affect the validity of any proceeding taken under this section. Service by certified mail in the manner herein provided shall be effective on the date of the mailing. (Ord. 72 §1, 1991; Ord. 45 §3.5, 1984; Ord. 39 §3.5, 1983)