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SR 520 - West Approach Bridge North Project: What's Happening Now?

Updated: May 19, 2017

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Project photos

See more photos of SR 520 construction
on our Flickr site .

Project overview

The West Approach Bridge North (WABN) project is underway in the Montlake area and on Lake Washington. Work hours may vary depending on the construction activity. Construction crews will continue to employ best management practices throughout construction to minimize impacts on the community and environment. Due to the dynamic nature of construction activities, construction plans are subject to change. WSDOT will provide the public with ample notice before construction activities or closures occur.

In the next few weeks, crews will begin the following activities within project boundaries:


Construction activities under a city of Seattle temporary noise variance

  • No activities currently under a city of Seattle TNV

Construction activities

SR 520 closures 

No closures scheduled at this time.

Arboretum Waterfront Trail closure

The Arboretum Waterfront Trail is now open.

Arb trail is open
Click image for larger, printable version. (pdf 5 mb)  

Construction activities near the MOHAI and Old Canal Reserve staging areas

Activities in the next few weeks

Roadway deck: Roadway deck pours are complete.

You may also feel vibrations during the day as crews:

  • Make final elevation adjustments in the MOHAI area: Crews are constructing the new off-ramps to 24th Avenue and Montlake Boulevard from Thursday, April 20, through the evening of Friday, April 21. The last step before placing asphalt is to create a firm base at the proper elevation by stabilizing and compacting the soil in the MOHAI site. To complete the work, crews are taking advantage of the dry weather forecasted for today and tomorrow and will be actively working in the MOHAI area into the evening. All work is scheduled to end before 10 p.m. both tonight and tomorrow night. Work will resume at approximately 7 a.m. each morning.
  • Remove steel piles from the temporary work bridge: Crews will continue to use vibratory hammers to remove steel piles from the extension piers of the temporary work bridge. Crews have also started removing the steel piles from the main trunk of the temporary work bridge. They are starting near the new floating bridge and making their way west. As crews move further west towards the MOHAI staging area, you may feel vibrations. Crews plan to continue use of the vibratory hammer between the hours of 7 a.m. and 10 p.m. on weekdays, and 9 a.m. and 10 p.m. on weekends.  

Activities in the next month

  • Utility installation: Installation of drainage will continue in the Old Canal Reserve and MOHAI staging areas over the next few months as weather permits. This work may cause vibrations during the day due to the compaction of soil. 

Ongoing activities over the next few months

Ramp removal work near Lake Washington Boulevard

The only sections remaining of the old westbound SR 520 off-ramp to Lake Washington Boulevard and the R.H. Thomson “Ramps to Nowhere” are those that stand over water. In the next two weeks, crews will prepare the work site so that active removal work of the barrier can begin on Monday, March 13.

What to expect:

  • Hoe ram and muncherConstruction hours: Ramp-removal crews plan to work 10-hour days, seven days a week. All impact activity, such as jackhammering or hoe ramming, will be completed between 7 a.m. and 10 p.m. during the weekdays and 9 a.m. and 10 p.m. on the weekends. All nonimpact construction activities, such as processing ramp rubble, munching concrete or moving equipment around the site, may take place before 7 a.m. and after 10 p.m. Inspectors on site will ensure that nighttime crews stay under the decibel levels permitted by the city of Seattle noise ordinance.
  • Noise: As crews complete this removal activity, nearby neighbors may hear hoe rams or munchers (both pictured to the right).
  • Vibrations: Neighbors may feel vibrations from the ramp-removal work.
  • Lights: Neighbors may see lights used during nighttime work to keep the site illuminated and safe for crewmembers. Crews will make every effort to keep lights pointed away from homes, where feasible.

The removal work is expected to continue for the next three to four months. We will keep you updated through these emails as the work progresses. If you have any questions or concerns regarding the ramp-removal work, please feel free to call the SR 520 24-hour hotline at 206-708-4657 or email us at

Old ramps over water

Continued bicycle/pedestrian detour on Montlake Boulevard

Since the 24th Avenue overpass closed last fall, bicyclists and pedestrians have been detoured from 24th Avenue to the Montlake Boulevard sidewalk, via East North Street. For your safety, please continue to use the signed detour route along Montlake Boulevard, as shown in the map below. To avoid potential conflicts between bicyclists and pedestrians with construction vehicles and off-ramp drivers, the bicycle-pedestrian path across 24th Avenue East bridge will remain closed during this temporary configuration. For more information on this topic, check out our "Frequently Asked Questions" document.

Stay tuned for updates on bicycle-pedestrian access through this area as the WABN project is completed in 2017. WSDOT secured full funding in 2015 to build the remaining west side portions of SR 520 and is currently evaluating how to phase the remaining portions of the SR 520 Bridge Replacement and HOV Program. There may be additional changes as we identify how the next phase of construction interfaces with the WABN project.

Detour route

Click image for larger, printable version. (pdf 5 mb)

City of Seattle temporary noise variances

When needed, a temporary noise variance can be granted to Flatiron by the city of Seattle to allow the contractor to conduct noisier work outside the typical hours of construction.

  • The city's noise ordinance allows for variances for louder nighttime work between 10 p.m. and 7 a.m. on weekdays and 10 p.m. to 9 a.m. on weekends.
  • Use of noisy impact equipment, like jackhammers, will occur before 5 p.m. as required by the temporary noise variance.
  • WSDOT inspectors will monitor nighttime activities to be sure work complies with city of Seattle requirements.

Watercraft restrictions

Crews will continue on-lake construction activities near the Montlake shoreline and the Arboretum. Cranes and other waterborne construction equipment limit water access under SR 520 near the Arboretum. Canoers and kayakers should use caution when navigating near the construction zone and stay at least 150 feet away from all construction equipment.

During construction, many of the canoe/kayak landings in the area will remain open but we recommend using the launches in the Arboretum or the University of Washington's Waterfront Activities Center. If you are unsure which boat launch to use, take a look at the map below and/or contact our construction hotline at 206-708-4657

Boater map
Click image for larger, printable version. (pdf 7mb)


Tree protection and removal

To make way for the temporary bridge and staging areas, crews removed trees as necessary on Foster Island and in the Montlake area. WSDOT worked with the city of Seattle to remove as few trees as possible, and will continue to mark trees for protection with orange fencing and will coordinate on replacement plantings.