It may be the shortest interstate highway in Oregon – and one of the shortest in the United States – but Interstate 405 in Portland is one of the state's heaviest traveled interstates. Also known as the Stadium Freeway, the 4.2 mile-long I-405 runs through the western side of downtown Portland. Located on one side of the Willamette River (with Interstate 5 on the other side), I-405 is part of a major route for commercial and commuter traffic around the downtown center and serves as an alternate to I-5, even though its posted speed limit is 50 miles per hour due to short distances between exchanges and a high volume of merging traffic.

As Don Hamilton, Oregon Department of Transportation (ODOT) Region 1 Public Information Officer, explains, “On the east side of the Willamette River we have the intersection of I-405 and I-5. On the west side of the river we have the intersection of I-405 and U.S. 30. These travel corridors have high average daily traffic (ADT) as this is a key freeway connection to the City of Portland and critical freight routes. It's a major metro area route providing access north-south as well as east-west, and for commuters and freight from the northwest. I-405 also provides key access to the downtown street connections while also being an alternate route for I-5.”

The ADT was 104,600 vehicles average per day in 2020, Hamilton reports.

The freeway serves as a gradual ramp up to the Fremont Bridge, a steel tied-arch, double decker bridge over the Willamette which carries southbound traffic on its upper deck and northbound traffic on the lower deck. Thus the elevated sections of I-405 leading to the bridge require a large number of bridge joints, which must be inspected and repaired at regular intervals.

ODOT has recently completed a three-year project to repair – and in some cases, replace – over 40 of the bridge joints on the freeway; the I-405 Ramps Project began in 2019 and was finished at the end of 2021. In 2019 and 2020, crews successfully repaired and replaced a number of freeway joints on the elevated sections of the route on either side of the Fremont Bridge and from I-405 north to U.S. 26 West, and installed new concrete surfaces on three freeway ramps.

Hamilton relates, “When crews began repairing two bridge joints on U.S. 30 approaching I-405 north and south in the fall of 2020, they discovered the joints needed full replacements based on their condition, not just repairs. After delays in steel production, these final joint replacements were completed in November 2021.

“This is a key entry point to the City of Portland across the freeway system, with connections to both I-5 and U.S. 30,” he continues. “This is also a key freight route with direct access points to the Port along U.S. 30. The expansion joints are key mechanical systems within a bridge that allow the bridge to move with temperature variations. When these systems fail, it can cause extensive damage to key elements of the bridge. ODOT Bridge Maintenance recognized the importance of these elements and made fixing these items a priority.”

Wildish Standard Paving Co. was the primary contractor for the $16.8 million ODOT project; the primary consultant was DOWL. Other project partners included:

• Subcontractors/Suppliers – ACC West Coast, Certified Personnel Services Agency, Aaken Electric, KT Contracting, ACS Testing, Brothers Concrete Cutting, Columbia West Engineering, Accurate Concrete Cutting, Spartan Environmental, Hicks Striping, Nation’s Mini Mix, River City Environmental, Superior Sweeping, Hatch Western, American Concrete Company, Roger Langeliers, Jonnic Construction, Knife River Corporation.
• Subconsultants – JLA, APEX, DKS, Michael Minor & Associates, David Place, Akana.

Repair and replacement of such a large number of joints along a very busy route necessitated a carefully coordinated schedule of lane closures and detours. Traffic was impacted on multiple freeways, including I-405, U.S. 30, I-5 and U.S. 26. The closures were needed to maintain a safe work zone for the traveling public and construction staff, Hamilton reports. “The DOWL/ODOT team designed this project with traffic restrictions in mind. The work zones were designed in stages where traffic would be restricted to certain travel lanes while construction work activities took place on the remaining sections of the bridge. This allowed for the freeway to remain open at all times while the work was performed.

“Given the very high average daily traffic the project need to be constructed in phases and any closures required accelerated construction techniques including rapid set concrete, around-the-clock work shifts and a large public involvement effort to minimize impacts to the traveling public and the freight community. Closures had to be timed to not coincide with major metro area events including events held at the Moda Center, parades, racing, air shows, marathons and other high traffic-generating times. Work also had to be coordinated with other local agencies and lease holders under the bridges.”

Among the traffic restrictions were nighttime single and double lane closures and weekend daytime single lane closures throughout the project area, as well as nighttime and around-the-clock weekend closures, lasting until 10 a.m. Mondays, of on- and off-ramps.

There were 24/7 closures of U.S. 30 east to I-405 north (18 days) and U.S. 30 east to I-405 south (11 days). Twenty-five weekend closures of on- and off-ramps and lanes occurred, along with frequent nighttime closures of each ramp – the night work helped to minimize traffic impacts during the day. Closures of sidewalks, lanes and parking on local roads under I-405 were also part of the construction process.

As with most construction projects across the country in the last two years, the I-405 Joints Project had to address challenges related to COVID-19. Says Hamilton, “This project was completed while the region faced the pandemic, fires, and supply chain challenges. These included having work slowed or stopped because of outbreaks within the project team, and stop-work orders because of unhealthy air conditions. The COVID-19 pandemic did affect the production rates. The contractor had to adapt by having crews wear masks, social distancing, disinfecting tools, and even supplying warm water hand washing stations on the project. However due to reduced traffic volumes ODOT allowed the contractor to perform some of the closures during weekdays. This enabled the contractor to maintain schedule.

“The team also had to react very quickly during closures to overcome deviations in the conditions found versus the as-built plans. Concrete depths, steel dimensions, welding details and connections were all found to be different than anticipated, requiring the designer and contractor to react quickly in order to get the bridge open on time, which they did.”

The very short interstate highway, which nevertheless serves a major role in the flow of downtown Portland traffic, has now seen its condition vastly upgraded. With the completion of the I-405 Ramps Project, the route's long-term reliability and heavy use capability have been enhanced.

As Hamilton states, “It is critical that the Stadium Freeway is kept in good working order. This is a crucial part of our transportation system, and this project was intended to keep the route functioning and in good working order. This I-405 project protects a billion-dollar piece of public infrastructure for years to come and improves safety for the traveling public.”

Photos courtesy of the Oregon Department of Transportation