Project overview
In winter 2023, construction began on a project to strengthen multiple highway overpasses along the I-405 corridor to better withstand a major earthquake. Crews placed steel "jackets" around columns at each location, reducing the chance that an overpass could collapse.
What to expect
Construction is complete for this project. No additional traffic control is planned.
At the I-405 and SR 520 interchange in Bellevue, columns that support seven bridges will be retrofit with steel jackets. These will reduce the possibility the pillars could collapse in a major earthquake.
We will retrofit bridges that carry I-405 over:
- Longacres Drive
- SR 520
- Northup Way
- 115th Avenue and BN railroad
- Cross Kirkland Pedestrian Trail
- The ramp from northbound I-405 to westbound SR 520
This work is part of our seismic retrofit program, designed to help our critical infrastructure survive a major earthquake. Being able to quickly move supplies to affected areas is vital to earthquake recovery and our highways play an important role in that.
The columns that support overpasses have rebar inside them to provide structural strength, but in a major earthquake the concrete can still crack; if enough becomes dislodged the columns could collapse. Adding steel jackets will help keep the concrete in place, reducing the chance of a collapse and keeping the highways open to deliver supplies to aid recovery.
