§ 63. Maintenance by state of alteration to certain highway bridges not state owned. When in the canalization of a natural waterway to form a part of the canal system it has been or may be necessary to alter an existing highway bridge spanning the canalized portion of the waterway, the maintenance and repair of the additional or new part or parts of such bridge structure which may have been or may be necessary in altering the bridge to meet the requirements of navigation, shall be an obligation of the state. The commissioner of transportation shall have supervision and direction over such maintenance or repairs, the cost of which shall be defrayed from moneys appropriated for the improvement, maintenance and repair of the canal system.