The Lafayette Street Bridge is one of three bridges located in Bay City, Michigan. It carries the M-13 and M-84 over the Saginaw River and is the oldest of Bay City’s four modern lift bridges. The existing main span is a double Scherzer pivot pier that provides a 150-foot (ft) long navigable channel, and the approach spans consist of a steel multi-girder cross-section. The total length of the bridge is 451′-6″. The existing bridge has 30 feet of curb to curb clearance and has two vehicle lanes with 5-foot sidewalks on each side.
M&M provided engineering design review services for the replacement of the lift bridge structure. The new lift bridge set is a 200′-0″ diameter double leaf lift abutment. The cross-section includes 2 steel girders, floor slabs and stringers. The floor system is composite with infilled mesh. There is a sub-deck counterweight and the structure is supported by large reinforced concrete piers.
The goal of the project was to ensure that the new structure was reliable, structurally sound, and maintainable.
The rebuilt bridge will have a completely new function that will help improve non-motorized transportation across the river. The plans for the bridge include a shared bicycle and pedestrian path along the new structure.
The Lafayette Street Bridge is owned and operated by the Michigan Department of Transportation. The Lafayette Bridge is not operated by Bay City Bridge Partners, which is renovating the Liberty and Independence Bridges to become toll facilities.
MDOT also operates the Veterans Memorial Bridge, which is located downriver directly from the Lafayette Street bridges. Because they are owned by the state, the Veterans and Lafayette bridges will remain free for use.
MDOT had originally planned to replace the elevated portion of the Lafayette Street Bridge. Full replacement of the bridge deck after a feasibility study in 2014. The initial cost of the bridge replacement was estimated at $45.5 million, but according to MDOT, the estimate has risen dramatically since the final copy of the bridge design was completed.
