The existing bridge provides a vital connection between Iowa and Wisconsin, spanning Lower Pool 9 of the Upper Mississippi National Wildlife Refuge.
The new continuous truss bridge will emulate the look and feel of the original cantilever truss bridge, however the main navigation clear span length will be increased from 640 feet to 750 feet, and roadway width increased from 21 feet to 40 feet. The steel through-truss structure will have a length of 1,352 feet, with the total bridge length reaching 1,724 feet.
The project team brought extensive experience in the National Environmental Policy Act (NEPA) process, wetlands, endangered species, 2D modeling of river hydraulics, and design and constructability of major river bridges to address these key issues and opportunities:
- Designing for constructability. The project required special consideration of constructability based on river geometry and limited staging areas. The team leveraged its experience on more than 30 major river bridges, including specific design experience with float-in construction.
- Mitigating impacts to the environment. Our environmental team worked closely with agencies and local stakeholders to define the Purpose and Need and evaluate alternatives that considered the historic nature of the bridge, wetlands and wildlife habitat, local cultural sites, and impacts to the local economy. The design team also proposed an alignment alternative that minimized the structure length and avoided the most sensitive wetlands near the project.
- Preserving the historic nature of the bridge. Developed structural design concepts to emulate shape of existing bridge. Presented aesthetic study and developed architectural concepts for incorporation into new piers and retaining walls.