Foreclosure of delinquent local improvement assessments or the final installments thereof shall be commenced annually on or before July 1st, but not before the city clerk-treasurer has mailed to the persons whose names appear on the assessment roll as owners of the property charged with the assessments or installments which are delinquent, at the address last known to the clerk-treasurer, a notice thirty days before the commencement of the proceedings. (Ord. 1568 § 1, 1972)