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SR 520 - West Approach Bridge North Project Construction Plans

Construction for the SR 520 West Approach Bridge North began in September 2014.

What can I expect during construction?

As the West Approach Bridge North project moves forward, WSDOT is committed to construction management practices that avoid, minimize, and mitigate the effects of WABN construction activities on neighbors, communities and the traveling public.

WSDOT will employ construction techniques that minimize construction effects, for example:

  • Keep SR 520 open to traffic during construction with limited weekend and evening closures in coordination with other projects
  • Build the west approach structure using work bridges and limited barge work in order to limit truck traffic on local streets
  • Restrict nighttime construction work to reduce noise effects
  • Evaluate ways to buffer and screen adjacent communities from construction activities

How will WSDOT build the West Approach Bridge North project?

See the image below for an overview of the steps needed to construct the new West Approach Bridge North.

Click image for larger, printable version. (pdf 390 kb)

September 2014 - Began construction

  • Installed construction fencing and performed environmental protection measures around project boundaries.
  • Marked restrictions to shoreline and trails.
  • Began to set up field trailers and equipment in staging areas.

October 2014

  • Remove trees and vegetation as necessary and mark trees to be protected, including on Foster Island.
  • Weekend highway closures to begin demolition of a segment of the unused R.H. Thomson ramps and establish work bridge access at Foster Island.
  • Begin installing piles to establish work bridge access from the former MOHAI area.
  • Begin abatement and demolition of former MOHAI building.

November 2014

  • Begin construction of local street and capacity improvements on Montlake Blvd and Lake Washington Blvd.


  • Continue building temporary work bridge and begin building permanent West Approach Bridge North bridge structure.
  • Continue building improvements to Montlake Blvd, Lake Washington Blvd and new off-ramp to 24th Ave E.
  • Complete demolition of the westbound Lake Washington Boulevard off-ramp and unused R.H. Thomson ramps (after new ramp to 24th Avenue E is open).
  • Close 24th Ave E, extend existing bridge north to accommodate new off-ramps.


  • Continue building the West Approach Bridge North bridge structure and new off-ramps.


  • Remove temporary work bridges.
  • Connect new West Approach Bridge North bridge to the new floating bridge.
  • Complete new stormwater facility in Montlake.
  • Open new bridge and regional shared-use path.

How can I get involved and find out more?

WSDOT has developed a WABN Community Construction Management Plan (CCMP) with local communities that outlines best practices and communication tools to minimize construction effects. For example, the CCMP helps to identify opportunities to implement measures such as noise buffers and screening, where appropriate, for the duration of construction.

We encourage you to check out the document to learn more!