10-Mile Project Corridor Includes a New Signature Bridge

• Cable-stayed bridge designed high above the Mobile River navigational channel
• Six-lane bridge bypassing two aging tunnels
• Design manager working with two design-build teams

Those traveling through Mobile, Alabama, have dealt for decades with a congested stretch of Interstate 10. The existing Wallace Tunnel, which carries I-10 across the Mobile River, was designed to carry 35,000 vehicles per day, but already has an average daily traffic of about 75,000 vehicles per day. A new Mobile River Bridge will increase the capacity of I-10 while new bridges crossing the Mobile Bay will raise the roadway above hurricane storm surge levels. The entire project corridor is just over 10 miles long. 

HDR has been involved in the development of this important project for the Alabama Department of Transportation for many years and is now serving as the agency’s owner’s design manager. In that role, our team provides technical reviews of design submittals from the design-build teams working on the project. Representatives from our team participate in task force meetings during design development, attend design meetings, respond to requests for information, provide over-the-shoulder reviews, lead design submittal reviews and help resolve comments that result from the design review process. We also work closely with the project’s program manager that provides scheduling, risk management and project controls services to ALDOT. 

Mobile River Bridge

The Mobile River Bridge consists of a new cable-stayed bridge over the Mobile River, east and west high-level approach bridges and associated interchange improvements. Our bridge and highway design professionals were involved in the early conceptual design and have continued to support ALDOT by leading the design and plan reviews for the cable-stayed bridge. 

The new six-lane bridge will be in addition to the existing tunnels, which each carry two lanes of traffic. To accommodate ship traffic, the new bridge will provide at least 215 feet of vertical clearance across the Mobile River navigation channel. When completed, the bridge deck will be the second highest of any bridge in the U.S. over a navigable waterway — only the Golden Gate Bridge is higher. The bridge will cross the 600-foot navigation channel with a 2,575-foot main span structure served by high level approach spans on each side. 

In addition to the increased capacity of the new bridge, the project will provide a direct interstate route for hazardous material transport that is currently prohibited from using the tunnels. This has forced hundreds of trucks each day to detour through Mobile’s central business district. 

Five interchanges along I-10 will also be modified near the bridge. 

Bayway

To the east of the new Mobile River bridge, a separate design-build team will be replacing two existing two-lane I-10 bridges across the Mobile Bay with two three-lane bridges. Most of the existing Bayway is well below the 100-year wave crest elevation, placing it within the wave impact area. On average, the new Bayway will be up to 8 feet higher than the existing elevation.

The new bridges will run approximately 7.4 miles from the Mobile River Bridge’s high level approach spans to the US 90/98 Eastern Shore interchange in Daphne. Two interchanges along the Bayway will also be reconstructed, including one at midbay, where I-10 meets US 90/98.

Both the Bayway and the Mobile River Bridge also include an all-electronic, open road toll collection system and updated intelligent transportation systems.