I-74 over the Mississippi River

Spanning the Mississippi River, this enormous and complex, $1.2 billion-dollar mega-project successfully increased capacity and provided structural improvements along the I-74 corridor in the Quad Cities in Illinois and Iowa.

Stretching 7.8 miles in length, this project included a new river crossing, interstate expansion, improved arterial streets, and increased access for pedestrians and bicyclists. The two signature, basket-handle, through-arch river bridge structures span 3,300 feet across the Mississippi River, with an almost 800-foot navigation span that now carries twice as much traffic and provides an aesthetically impressive gateway to and from the Quad Cities.

With joint participation by the Iowa and Illinois Departments of Transportation, Benesch was selected for two critical project roles. As Corridor-Wide Coordinator, Benesch ensured uniformity and quality of design throughout the corridor’s many sections and contracts, paying special attention to project schedules and staging schemes and managing outreach to impacted stakeholders. As Central Section Design Lead, Benesch oversaw design services for the portion of I-74 crossing over the Mississippi River, which includes the corridor’s signature true arch bridges. Benesch designed the true arch bridge substructures and provided an independent structural review of the overall true arch design.

To achieve long-term strength and durability, the team developed a new, innovative, and industry-changing steel alloy for the arch structure. This high-strength steel is truly an advancement in engineering and material technology that will benefit the industry for decades to come.

Initial construction duration estimates for this project were as long as eight years. However, the project team quickly embarked on an aggressive schedule, splitting the corridor into multiple contracts to deliver the project in just 3.5 years while minimizing mobility impacts during construction.

The I-74 corridor’s innovative, sustainable infrastructure improvements will last well into the next century, providing safer, expanded vehicular, pedestrian and cyclist mobility to the Quad Cities region.