Portland's Burnside Bridge is set to close in 2027 and will remain closed for five years for a seismic rebuild.
Due to the instability of the soil on which it stands and the infrastructure on either side of the Willamette River, Multnomah County engineers will build three bridges. Each one will connect to the other in a way that ensures they remain standing and functional after a major earthquake.
When the bridge was built in 1926, the two piers in the river were placed on 380 tree trunks, driven into the mud. Despite holding up throughout the decades, an earthquake could liquefy the soil below and make the trunks fail.
“We expect that it will be fully closed for five years,” said Multnomah County construction manager Emily Miletich to OPB.
“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 to OPB.
The bridge’s environmental review was recently completed, with the majority of the big structural decisions have been made.
The current estimated cost is up to $895 million. So far, the county has applied for federal grants and received some state financing to pay for it.
“We won’t be advancing to construction without that full package put together,” Miletich said to OPB.
The bridge is expected to have a moveable deck so large ships can still sail underneath. There will be bike and pedestrian lanes on either side and two lanes of traffic each way.
With demolition of the bridge currently scheduled for 2027, the bridge will be expected to open in 2031.