Maple Street Bridge Receives Enhancements to Extend Its Service Life
CITY OF MANISTEE – Originally built in 1964, the Maple Street moveable bridge in Manistee, Michigan serves as a primary route of transportation over the Manistee River.
The structure has an overall length of 286 feet and is 37 feet wide, supporting two lanes of two-way traffic. Sidewalks line both sides of the bridge and provide a popular spot for pedestrians to stop and view the river and boats.
The Maple Street Bridge has an average daily traffic count of 6,000 cars per day and is an important route to keep open since it is only one of two river crossings in downtown Manistee. The other is the MDOT-owned Memorial Bridge, or US-31 bridge. If both bridges were to be closed at the same time, the only other detour route across the Manistee River would be to travel 12.1 miles around the entire Manistee Lake. Additionally, this moveable bridge must be opened periodically to allow freighters and pleasure craft to traverse the channel and access marinas and commercial ports.
The Manistee River is a unique marine transportation route overseen by the U.S. Coast Guard. This high-traffic channel serves as a direct throughway into and out of Lake Michigan, which is located to the west. Large freighters use the channel approximately 35 times a season to deliver coal, aggregate, rock salt, bituminous asphalt, and other items.
The Maple Street Bridge is a bascule bridge, meaning that each side (or leaf) is able to be lifted. This type of moveable bridge has been around for centuries and is commonly referred to as a drawbridge. The bridge operates via large rolling girders supporting the bridge deck, and a gear that rolls on a horizontal rack to drag the girder and cause the bridge to open when electric controls are activated. This allows the many cargo ships and boats to pass through the channel.
Federal law requires routine bridge inspections to check for quality and safety at least every two years. Because of the structure’s complex nature, specific inspection procedures must be documented and completed. The City of Manistee is responsible for ensuring these inspections are completed, and the bridge has performed very well as a result of the City’s regular maintenance to the bridge.
For the past 10 years, Spicer Group has performed these required routine, mechanical/electrical, fracture critical, and underwater inspections for the City of Manistee. These inspections provide condition assessments to supplement the City’s management and preservation of this structure.
“These inspections are especially important for this bridge because they’re nonredundant steel tension members,” Richard Kathrens, P.E., a Project Manager from Spicer Group said. “This means there are two main girders holding up the whole bridge and if one of those members were to fail, the bridge would collapse.”
The girders, along with the bridge’s many other features, were carefully checked during the 2021 inspection. The City of Manistee takes great care in maintaining their structures, so the bridge was already in good shape. However, during this inspection, several areas of the structure were identified for general maintenance, and repair recommendations were made to the City by Spicer Group.
The identified preventative maintenance repairs included structural steel paint, minor structural steel repairs, concrete deck and sidewalk patching, epoxy overlay on the deck surface, healer sealer on the sidewalk, and miscellaneous electrical repairs.
Spicer Group worked with the City of Manistee to prepare and apply for Local Agency Program funding from MDOT and the Federal Highway Administration. The funding was awarded and went towards covering 95% of the construction costs of nearly $1 million.
The construction documents and specifications for the bridge repairs were all developed by Spicer Group, who also provided construction oversight and inspection during the renovations— this included steel inspection, paint inspection, and bridge balancing, along with daily reports, LAP, and office technician work.
Federal law states the Maple Street Bascule bridge must be opened to vessels on demand from May 1 to October 31 of each year. If the bridge is not operational, it must be left in the open position as the navigation of vessels takes precedence over vehicle traffic. This was accounted for during the planning phase of the project when the team noted the bridge would need to be tarped to contain the sand blast material from the painting process. The bridge would not be able to be opened or closed during construction. Maintenance activities were scheduled to be completed in the winter months which also meant heating the tarped area to provide the proposed painting environment.
The project was completed a year before the $14 million renovations of the Memorial Bridge began taking place and is used as part of the local detour.
