When any contract shall have been completed, and on the filing in the office of the city clerk of the certificate of the city engineer or other officer under whose supervision the work was done, stating that he has inspected said work, and that it is done according to the contract and specifications, the mayor and clerk may issue their warrants on the treasurer for the amount due such contractor or contractors; and they may, when so stipulated in the contract, or with the consent of the council, from time to time during the prosecution of the work (upon the filing of the certificate of the proper officer, stating that he has examined and computed or measured such work, and that he believes that there is enough done to cover the estimate, and that it is done in accordance with the contract), advance to the contractor and draw their warrant upon the treasurer for such advance, reserving, in all cases, at least five percent (5%) of the estimate or contract price, to be paid when the contract is completed. (Ord. 871, 2-17-1981)