If any assessment is not paid within five days after its confirmation by the Council, the amount of the assessment shall become a lien upon the property against which the assessment is made by the City Engineer, and the City Engineer is directed to turn over to the Assessor and Tax Collector a notice of lien on each of the properties on which the assessment has not been paid, and the Assessor and Tax Collector shall add the amount of the assessment to the next regular bill for taxes levied against the premises upon which the assessment was not paid. The assessment shall be due and payable at the same time as the property taxes are due and payable, and if not paid when due and payable, shall bear interest at the rate of 6% per year.
(`78 Code, § 13.20.160.)