I-405 - BN RR Br to Ped Trail Br & I-90/E Fork Issaquah Creek - Seismic

Project news

  • This project will advertise for bidders in June 2021.
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Needs & benefits

In summer 2021, our contractors will begin a project in the I-405 corridor that will strengthen several overpasses to help them withstand a major earthquake. These include structures that carry I-405 over:

  • Longacres Way
  • SR 520
  • Northup Way
  • 115th Avenue and BN railroad
  • Cross Kirkland Pedestrian Trail
  • The ramp from northbound I-405 to westbound SR 520

To strengthen these overpasses, our contractor crews will place steel “jackets” around the columns. While these columns already have steel rebar inside, the jackets will help keep the concrete together in case of a major earthquake, reducing the chances that an overpass could collapse.

What travelers can expect
Most of this work will take place below I-405 and will not affect traffic on the interstate, but people using the roads beneath I-405 should expect lane reductions, shoulder closures and some nighttime ramp closures. The work also may require sidewalk restrictions, but our crews will be sure there are alternatives.


  • June 2021: Advertise project for competitive bidding.
  • Summer 2021: Contract will be awarded.
  • Summer 2021: Work will begin.
  • Fall 2022: Work to be complete.


The total estimated cost of this project is $23.2 million, from state and federal funding sources.


Tom Pearce
WSDOT communications

A small map showing the locations on I-405 that will receive seismic reinforcement.