Any bridge or passageway over any artificial watercourse, located on a highway which it is the duty of the commissioner to maintain, constructed before May 10, 1957, shall be maintained by the person owning or controlling such watercourse. If any highway which it is the duty of the commissioner to maintain is to be constructed, reconstructed or relocated, and a bridge or passageway over any artificial watercourse on such highway requires expansion, relocation or reconstruction, the cost of such expansion, relocation or reconstruction shall be borne by the state and thereafter such structure shall be maintained by the commissioner.