When it becomes necessary, in the opinion of the Mayor or in the prosecution of any work or improvement under contract, to make alterations or modifications in such contract, such alterations or modifications shall be made only upon the order of said Mayor in writing. Provided, however, that such alterations or modifications must be approved by the Council in case such involves an additional expenditure exceeding five thousand dollars ($5,000.00). No such order shall be effective until the price to be paid for the work and material, or both, under the altered or modified contract, has been agreed upon in writing and signed by the contractor and the Mayor in behalf of the City. (Approved by voters 11-4-14)