A. In letting all contracts for public improvements, the city council may provide therein that at least ten percent of the amount due the contractor on estimates shall be retained to secure the payment of laborers who have performed work thereon, and material men who have furnished material therefor, and such laborers and material men shall, for thirty days after their work has been completed, have a lien on the ten percent so reserved for labor done and materials furnished, which lien shall be senior to all other liens, whether by judgment, attachment, or contract, and no improvement shall be deemed completed until a majority of the city council shall have signed and filed with the clerk-treasurer a declaration to that effect.

B. During the time allowed in the contract, the city clerk-treasurer shall on the last day of each month issue an estimate of the amount of work completed during the month by the contractor, but shall after the date set for completion of the contract, furnish no estimates other than the final estimate issued after the completion of the work.

C. The final estimate issued by the city clerk-treasurer shall include, in addition to a statement of the amount of money expended for abstracts, advertising and engineering prior to the date set for the completion of the contract.

D. All engineering expense incurred after the time fixed in the contract for its completion shall be borne by the contractor as a penalty for failure to complete the work within the specified time. (Ord. 1337, §6, 1980; Ord. 1561, §4, 1980).