Council Bluffs Interstate System Dual, Divided Freeway

Council Bluffs, Iowa

Award of Merit

Submitted By: HDR

Owner: Iowa Dept. of Transportation

Lead Designer: HDR

General Contractor: Hawkins, United, Cramer Joint Venture

Consultants: Benesch; HGM; HNTB; Iteris; Jacobs; Stanley; Terracon; WHKS

Built as part of the $1.5-billion Council Bluffs Interstate System Improvement Program, the project team delivered the area’s first dual, divided freeway. Building the three-mile section required relocating multiple railroads, managing flood events, designing complex bridge structures, traversing waterways and maintaining traffic on a vital corridor.

The team’s biggest challenge was keeping two lanes of traffic flowing with minimal disruptions while crews worked in tight confines. Intelligent work zone devices were implemented to improve safety and traffic flow. Electronic signs alerted drivers of trucks entering the interstate, providing time to merge and continue at highway speeds. Other devices alerted the Iowa DOT of queues on interstate ramps so it could adjust signals.

Facing large bridge skews and long spans along the east system interchange, the team studied use of staggered cross-frame layouts versus contiguous layouts. The team concluded that contiguous cross-frame layouts reduced structural steel weight, costs, fatigue stress, flange bending moments in the girders and future maintenance costs. The design resulted in 2% cost savings and extended the bridge’s expected lifespan.

The program also provided an opportunity to streamline rail lines. The team consolidated four main lines into a common corridor and eliminated nine at-grade crossings. The four-year project was completed under budget and ahead of schedule in July 2021.