When the I-74 Mississippi River Bridge could no longer adequately serve growing traffic volumes, an improved crossing between Bettendorf, Iowa, and Moline, Illinois, became a regional priority. In planning sessions to replace the twin bridge structures, Quad Cities residents made their preferences clear. They wanted a signature gateway for the region and a true-arch design. Their vision evolved into twin inclined basket-handle true arch bridges providing the essential mobility the communities needed and the structural beauty they wanted.

The new structures were a key component of an ambitious design-bid-build program to improve 5 miles of the I-74 corridor, a major east-west link in the nation’s transportation system. To ensure delivery of the river bridges, lead agency Iowa DOT tapped HNTB’s construction engineering and inspection expertise.

Serving as an extension of Iowa DOT, HNTB provided CEI services for the eastbound and westbound river bridges, Iowa-side viaduct and roadway approaches, as well as local road connections. Services included engineering, inspection, document control, quality assurance and, as the complex project unfolded, much more.

“HNTB provided a full range of expertise and support as needs arose,” said Jim Schnoebelen, Iowa DOT District 6 engineer.

A team approach

HNTB facilitated coordination and collaboration between the DOT, the design team, the contractor and the contractor’s engineer to identify workable solutions to issues with foundations, rebar, thermal control, mass concrete, steel fabrication, geometry and vortex-induced movement due to wind.

“Strong communication and partnership amongst the project team and Iowa DOT was essential for the successful delivery of the project,” said Bernie Hopfinger, HNTB project manager. “Being in lock step with each other allowed us to address situations quickly and efficiently to minimize the effect on delivery of the project.”

The team overcame challenges during arch erection, including high water that prevented barge movement in the river, high winds and extremely cold winters. Further, the channel remained open to commercial and recreational boats during construction with brief planned closures.

“The combination of the structure, its location over the Mississippi River and the true-arch design made the project unique,” said Travis Konda, HNTB construction engineering and inspection task lead. “There weren’t textbook answers for the challenges this project presented. An understanding of the engineering behind the design was necessary to complete the construction.”

And, HNTB did. The firm brought more than 100 years of site experience and bridge engineering best practices to the project.

“We tapped into HNTB’s expertise in drilled shafts, geotechnical engineering, electrical engineering and post-tensioning,” Schnoebelen said.

Expertise in action

HNTB’s extensive history of successful bridge design facilitated understanding the engineering and work to achieve fit-up and closure of the arch ribs standing 245 feet above the river.

“Given the complexity of the arch erection and subsequent tolerances to establish closure, there was a need to develop a technical understanding across the team,” Konda said. “So, we worked with the contractor, designer and Iowa DOT to develop a quality assurance survey plan to ensure the two connected arch segments joined at the apex.”

Tracking the as-built geometry as the arch erection advanced was a joint effort among the contractor, the erection engineer, the designer, Iowa DOT and the field staff.

“Consistent coordination between all parties was key in understanding the current as-build geometry during erection and making adjustments as the work progressed,” Konda said.

Work on the steel portion of the westbound arch began in March 2019 and finished 14 months later in May 2020. Work on the eastbound arch began in July 2020 and was completed 10 months later in May 2021.

As work progressed on the bridges, HNTB’s document controls team worked behind the scenes, ensuring change orders were handled promptly, federal audits went smoothly, the contractor was compensated properly and closeouts were timely and efficient.

When the westbound bridge opened to traffic in November 2020, motorists saw for the first time what they had envisioned for nearly 20 years: a stunning crossing with four lanes, wide shoulders and dramatically reduced congestion. The eastbound bridge opened Dec. 1, 2021. The project included several aesthetic elements such as:

• A 14-foot-wide multiuse path connecting trail systems in Bettendorf and Moline
• Glass oculus embedded in the scenic overlook’s multiuse path
• Dramatic LED lighting
• ADA accommodations

The combined bridges delivered on the overall theme of ‘Reflections,’ making the region’s vision of a signature gateway, improved mobility and greater safety a reality.