Whenever the cost and expense of any improvement is payable by the mode of “payment by bonds” as provided by ordinance ordering improvement, the whole or any portion of any assessment levied on account of such improvement may be paid without penalty or interest during the first 30 days following the date of the first publication of the notice by the Director of Finance that the assessment roll for said improvement is in his hands for collection, and the unpaid balance, if any, may be paid in equal annual installments, the number of which shall equal the number of years which the bonds to pay for the improvement may run; or the lien of any such assessment may be discharged at any time after the 30 days by paying the entire unpaid portion of the installment with all penalty, and costs attaching, together with all interest thereon to the date of the delinquency of the installment thereof next falling due. The first installment shall become due and payable during the 30-day period succeeding a date one year after the date of the first publication of such notice aforesaid of the treasurer, and annually thereafter each succeeding installment shall become due and payable in like manner. If the whole or any portion of any installment remain unpaid after the first 30-day period aforesaid, interest upon the whole unpaid sum shall be charged at the rate fixed in the ordinance providing for the improvement, and such interest upon the whole amount shall be payable each year upon the payment of the installments. Any installment not paid prior to the expiration of the 30-day period during which such installment is due and payable shall thereupon become delinquent. All delinquent installments shall be subject to a charge of interest thereon at eight percent per year, and to an additional charge of five percent penalty levied upon both principal and interest due on such installment or installments. [Code 1970 § 14.04.050; Code 1954 § 2-12.20.]