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I-5: Willamette River Bridges

(Whilamut Passage)

After cracks developed in the concrete of the original Willamette River Bridge, which carried an average daily traffic count of more than 70,000, OBEC and partners stepped up to design an emergency detour that would carry busy Interstate 5 traffic while the team designed and constructed a permanent replacement.

Getting there was a complex task. For starters, the massive project had to stay within the existing right-of-way, which resulted in the reconstruction of the I-5 freeway and connector ramps within their current footprints. This required complex construction sequencing, resulting in nine traffic control stages. To keep traffic moving safely, OBEC roadway engineers modeled in 3D to resolve all potential construction conflicts before they could lead to construction delays in the field.

Because of the high-profile nature of the project and the desire of area residents to be involved in the process, OBEC facilitated design workshops to develop aesthetic enhancements all around the project area, which ultimately led to public art installments visible from the traffic lanes and significant path improvements beneath the bridges.

The result: a set of parallel landmark concrete arch bridges, officially named the Whilamut Passage (in honor of the area’s native population), that serves as a graceful addition to the essential I-5 corridor.

Willamette River Bridge Time Lapse

  • This was ODOT’s first use of Construction Manager/General Contractor (CM/GC) contracting which allowed the costly, protracted construction issues to be eliminated by the immediate resolution of questions raised by field staff during the design phase of the project.
  • The bridges span the Willamette River, an urban arterial, railroad tracks, an interstate highway off-ramp, and two multi-use paths in a natural area and park on opposite sides of the river.
  • This $204 million bridge replacement was the largest and final project of the $1.3 billion OTIA III State Bridge Delivery Program.
  • Represents a modern take on the legacy of sweeping arch bridge designs established by Oregon State Bridge Engineer Conde McCullough in the 1920s and 1930s.
  • The project was one of just two winners for the Slag Cement Association’s “High Performance” concrete project of the year award. The other was One World Trade Center in New York City.
  • At lengths of 1985 feet northbound and 1759 feet southbound, these twin bridges are relatively as long as the One World Trade Center is tall (1776 feet).
  • 2013 Project of the Year, Slag Cement Association, High Performance Category
  • 2014 Excellence in Concrete, Bridges – Cast in Place, Oregon Concrete and Aggregate Producers Association (OCAPA)
  • 2014 Top Projects First Place, Transportation Category, Daily Journal of Commerce, Oregon
  • 2014 Best of the Best Highways/Bridges (National), Engineering News Record
  • 2014 Best Project Pacific Northwest, Engineering News Record
  • 2014 Excellence in Safety (National), Engineering News Record
  • 2015 Engineering Excellence Grand Award, American Council of Engineering Companies, Oregon (ACEC)
  • 2015 Second Place, Infrastructure Category, Excellent in Concrete, American Concrete Institute


At lengths of 1985 feet northbound and 1759 feet southbound, these twin bridges are relatively as long as the One World Trade Center is tall (1776 feet).