If, upon the completion of the project it is found that any sum theretofore assessed therefor upon any property is more than sufficient to pay the cost thereof, the Council must ascertain and declare the same by ordinance, and when so declared, it must be entered in the docket of city liens as a credit upon the appropriate assessment. If any such assessment has been paid, the person who paid the same or his legal representative, shall be entitled to the payment of any portion of the rebate credit which exceeds the assessment, by a warrant on the city treasury. (Ord. 2-1961 § 16, 1961.)