Whenever a contract has been entered into for the construction of street improvement as provided by article VI of the City Charter and the completion of the same has been delayed by litigation or act of God, the City may, with the written consent of the contractor, appoint appraisers for the completed part of the work, and cause assessments to be levied and improvement bonds to be issued therefor in the manner provided by the statutes of Oklahoma in force at the time, as modified by the City Charter and by ordinance passed pursuant thereto. The uncompleted part of the improvement may be abandoned by the contractor by serving written notice to that effect upon the City. (1980 Code § 30-43)