Portland is laying the groundwork for a rebuild of the Burnside Bridge, which will probably begin in 2027, and is estimated to take 5 years to complete.
Multnomah County engineers will have to rebuild the bridge due to the instability of the soil and the infrastructure on both sides of the Willamette River. Engineers will essentially be building 3 bridges, with each one having to connect top the other in a way that ensures a major earthquake won't destroy them.
“We expect that it will be fully closed for five years,” said Multnomah County construction manager Emily Miletich.
The long closure is due to the Endangered Species Act, which means work in the river is constraioned to times when endangered salmon are not running, and the bridge's complex downtown location and complicated design.
The bridge’s environmental review has just been completed, so most of the big structural decisions have been made. But the soil on the east side of the river could potentially liquefy during a large earthquake, so the county is still deciding what type of bridge to use.
“We’ve just selected a contractor to help us make a decision between a cable stay bridge and a tied arch bridge on the east side of the river,” said Miletich.
The area of the bridge is delicate because it goes over key transportation corridors, such as Interstate 6, Interstate 85, and a north-south railroad line.
There are a limited number of bridge designs that can stretch such a distance, so the county wants to consult the contractor.
On the west side, the decision has been made to build a traditional girder bridge, which is a similar structure to the current bridge. But modern technology means there will be fewer beams, which should open up the space.
The current cost of the bridge is up to $895 million. So far, the county has applied for some federal grants and received some state finances to pay for it. There’s also $300 million in vehicle registration fees available from Multnomah County.
Demolition is scheduled to start in 2027, with a potential opening in 2031.
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Source: OPB.org
