SECTION 63  MODIFICATION OF CONTRACTS.
   When it becomes necessary in the opinion of the City Manager, in the prosecution of any work or improvement under contract, to make alterations or modifications in such contract, such alterations or modifications, if made, shall be of no effect 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 by the City Manager and approved by the Council.