Hi. I’m Mike Pullen with Multnomah County.
As you may know, Portland’s aging downtown bridges are not expected to withstand a major earthquake. Experts say there is a 1 in 3 chance that a magnitude 8 or higher earthquake will happen in the lifetime of most Oregon residents.
That is why Multnomah County is taking the lead on ensuring we have one downtown bridge ready for the big one.
Located in the heart of downtown and on a regionally established lifeline route, the Burnside Bridge will play a critical role in helping our community respond and recover following such an event.
So where are we now? In late 2020 and early 2021, we heard strong support for the Replacement Long Span bridge option as the Preferred Alternative – it’s the least cost and best for seismic resiliency of the alternatives studied.
However, recognizing rising costs and competition for funds, County leaders asked the project team to look for ways to reduce the cost, to make it more likely the project will be funded and built.
To ensure an affordable and permittable project, we are recommending three primary refinements: reducing the overall width of the bridge, selecting a ‘girder’ structure type for the west portion, and a ‘bascule’ structure for the movable span.
Reducing the overall width of the bridge compared to the Preferred Alternative could save the project up to $150 million.
This cost-saving measure means that the new bridge would be roughly the same width as the current bridge – not narrower.
The reduction in width will be shared between vehicle lanes and bike and pedestrian space, without compromising safety.
To accomplish the width reduction, the project team is proposing reducing vehicle lanes from five to four lanes.
This is one of the biggest ways we can save money. This would result in some traffic delays compared to today.
There are four different options for how to allocate the four vehicle lanes.
Option 1 would have two lanes in each direction. One of the two lanes toward east Portland would be a bus-only lane.
Option 2 would have three lanes towards east Portland and one lane towards downtown. One of the lanes towards east Portland would be a bus-only lane.
Option 3 includes a reversible lane that would allow for traffic to move in either direction depending on the time of day. This option would have two lanes towards east Portland, a reversible lane in the middle, and one lane towards downtown. One of the dedicated lanes towards east Portland would be a bus-only lane.
Option 4 would feature a priority lane and signal for buses to jump ahead of traffic at each end of the bridge. This is another way to prioritize bus travel. The bridge itself would have two general purpose lanes in each direction.
The updated recommendation for bike and pedestrians is to have 14 to 17-foot-wide shared spaces on either side of the bridge compared to today’s width of 12.8 feet. The exact width will be determined in Final Design.
This updated width would still include space for crash-worthy barriers between traffic lanes and the areas for pedestrians and cyclists.
This is a reduction from the Preferred Alternative plans for 20-foot-wide facilities.
The other big change to the Preferred Alternative is a recommendation to go with an open, girder structure for the west approach near downtown. This could save the project $20-40 million. Even more importantly, it is the most likely option to receive required federal permits because it would not have adverse effects on the Skidmore and Oldtown Historic Districts.
For the movable part of the bridge in the middle, the team has been studying two options: a bascule type, like the current bridge, or a vertical lift type, like the Steel Bridge.
Cost analysis over the summer showed that the bascule option would cost about $25-$35 million less than the vertical lift.
Aesthetically, the bascule has been the more popular option due to its open look and feel - and similar to the girder option on the west side, it also avoids obstructing views of the historic districts near downtown.
For these reasons, the bascule-style movable span is recommended to move forward into final design.
The decision for the east portion of the bridge between a tied-arch and cable supported structure will be deferred until the Final Design Phase. This will allow the project team to work with the contractor on the technical challenges of building over the freeway, railroad, and unstable soils on the east side to see if meaningful cost savings can be realized.
Help ensure an earthquake resilient Burnside Bridge can be funded and built! Your input on the current recommendations is important. Learn more and share your feedback at www.burnsidebridge.org.