If different parts of any municipality or any two municipalities are separated by an intervening valley or ravine, and the county commissioners in which the municipality or municipalities are located decide it is necessary that a public bridge be constructed, the county may contract with the municipality or municipalities for the laying out and construction of the bridge by the municipality or municipalities, and may pay to the municipality or municipalities the portion of the cost as the county commissioners deem reasonable.
16 Pa.C.S. § 16755