If, upon the completion of the project, it is found that any sum theretofore assessed 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 or her 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. (Prior code § 2.028)