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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 employing best management practices throughout construction to minimize impacts on the community and traveling public, including:

  • Providing advance notice of noisy work and complying with city of Seattle noise permits.
  • Using noise shields on generators, compressors, jackhammers and other loud equipment.
  • Conducting pre-construction inspections of front-line properties.
  • Marking protected trees with high-visibility fencing.
  • Installing tire washes to prevent tracking of dirt and gravel on local streets.
  • Keeping spill-response kits and containment booms on all barges and marine vessels.
  • Using directional lights and shielding.
  • Applying water to dust-generating work areas and activities.
  • Following a no idling policy for construction vehicles.

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

Fall 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
  • Begin construction of local street and capacity improvements on Montlake Boulevard and Lake Washington Boulevard


  • Continue building temporary work bridge and begin building permanent West Approach Bridge North bridge structure
  • Continue building improvements to Montlake Boulevard, Lake Washington Boulevard and new off-ramp to 24th Avenue East
  • Complete demolition of the westbound Lake Washington Boulevard off-ramp and unused R.H. Thomson ramps (after new ramp to 24th Avenue East is open)
  • Close 24th Avenue East, 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 to the new floating bridge
  • Complete new stormwater facility in Montlake
  • Open new bridge and regional shared-use path

How can I learn about upcoming construction activities?

You can learn more about upcoming construction activities by visiting our What’s Happening Now webpage or by signing up for our WABN email updates. To sign up for email updates, enter your email and sign up for the alert called “SR 520 West Approach Bridge North Project” located under the “Construction Reports” section.