The Replacement Long Span Bridge was recommended as the preferred bridge alternative to move forward into design after it is approved by Multnomah County and the Federal Highway Administration. The alternative will replace the existing Burnside Bridge with a new movable bridge in the same location and length as the existing bridge with support structure above the roadway surface resulting in fewer columns below. This means there are longer spans, or distances, between columns. It was recommended because it is the most seismically resilient with the lowest cost and fewest impacts to natural resources.
An important next step in the process is to select the type of long span bridge to build. This also includes the type of movable span. Learn more about the Bridge Type Selection phase and what bridge types are being considered.
Other Alternatives Considered
While the Replacement Long Span was identified as the Preferred Alternative, the Draft Environmental Impact Statement is wrapping up its study and documentation of the four alternatives and the no-build alternative. The other alternatives considered and evaluated include:
1. Enhanced Seismic Retrofit - This alternative would upgrade the existing bridge. While this option allows for the preservation of portions of the historic Burnside Bridge, it requires replacement of some elements, extensive retrofitting of others, and retains many columns in unstable soil near the river. The cost of the retrofit is greater than building a new Long Span bridge.
2. Replacement Short Span - This would be a new movable bridge at about the same surface height and location as the current bridge. It would have few columns than the current bridge, but more than the Replacement Long Span. This option is more expensive, has greater natural resource impacts and presents more seismic risk than the Replacement Long Span because it requires more columns in unstable soil near the river.
3. Replacement Northeast Couch Extension - This alternative would be a new movable bridge featuring a new westbound extension of Couch Street over NE 3rd and NE 2nd Avenues that would connect to the bridge over the river. While this option would smooth out the current S-curve on Couch Street, it requires many more columns in unstable soil near the river, increasing seismic risks and making it the most expensive alternative studied. It would also have the greatest impacts to natural resources, businesses, and bicycle access on the east side.
The project is still in the Environmental Review phase and the DEIS will be published and available for public input in early 2021.
Traffic Management During Construction
The project team and Community Task Force considered two ways to manage traffic during bridge construction, which is expected to last four to five years starting in 2024.
The recommended Preferred Alternative for managing traffic during construction is to fully close the bridge and detour all vehicles, bikes and pedestrians to neighboring bridges. This alternative was recommended because it reduces construction time and cost and reduces impacts to natural resources and parks.
The other alternative considered was to build a temporary movable bridge to maintain some level of traffic over the Willamette River at Burnside Street. The temporary bridge was not recommended because it would add $90 million to the project cost, add another 1.5 to 2 years to the overall construction duration and have additional impacts to natural resources.
The alternatives for managing traffic during construction are part of the Environmental Review Phase. Findings from the analysis are being documented as part of the Draft Environmental Impact Statement.