Such notice hereinabove mentioned may be served personally or by leaving the same at the residence or place of business of such owner, or any known agent of such owner. If no owner or agent is known to the street commissioner, then such notice may be served by posting it upon the property where such improvement is to be made. After serving such notice, the street commissioner shall make a certificate of such service, showing the manner and date of such service and shall file the same with the director of finance. (1983 Code § 12.02.060)