Notice regarding sidewalk repairs, sewer or water connections, dangerous structures, abating nuisances or any other act, the expense of which if performed by the city may be assessed against the premises under the provisions of this Code, shall be served:
(1) By delivering the notice to the owner personally or by leaving the notice at his residence, office or place of business with some person of suitable age and discretion;
(2) By mailing the notice by certified or registered mail to such owner at his last known address; or
(3) If the owner is unknown, by posting the notice in some conspicuous place on the premises at least 5 days before the act or action concerning which the notice is given is to take place. No person shall interfere with, obstruct, mutilate, conceal or tear down any official notice or placard posted by any city officer, unless permission is given by the officer.
(1993 Code, § 1-15)