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

Updated: May 24, 2016  

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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

Construction activities

Habitat Log Restoration

Beginning as soon as this week, crews will begin landscaping on Foster Island. Crews will transport habitat logs from the Old Canal Reserve area using the temporary work bridge and place the logs on Foster Island, near the Arboretum Waterfront Trail (see map below).

What you can expect:

  • Multiple truck deliveries during the day over the next few weeks.
  • Crews preparing soil for landscaping features on Foster Island.
  • Crews monitoring and controlling dust using water trucks near the Old Canal Reserve, as needed.

Click image for larger, printable version. (pdf 2 mb)

Casing installation work continues

Crews have been installing casings near the MOHAI staging area since April of this year and continue to extend casings for the WABN structure (see picture to the right). Nearby residents may feel and experience vibrations. This work is expected to continue for the next few weeks so nearby neighbors may continue to feel vibrations intermittently during the day as work continues.

Prior to the start of WABN construction, monitors were installed around the project area to measure vibration levels and ensure construction activities are within the limits set by the Federal Transit Authority. This ongoing casing installation work has been within the allowable limits and crews will continue to monitor this work.

If you’re concerned your property has experienced any damage, please contact us to schedule an inspection of your home. Project engineers can evaluate any potential damages that may have been caused by construction activities and provide information on next steps if you choose to submit a claim to cover costs of repairs if needed.

Arboretum Waterfront Trail Closure

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

The Arboretum Waterfront Trail on Foster Island re-opened yesterday evening, Tuesday, May 17. The trail was closed while crews drilled soil from bridge casings, placed metal rebar cages for column strength, and poured concrete to create shafts and columns for the new WABN.

The trail is set to close again Monday, May 23, for the safety of trail users as crews complete further work on the new bridge being constructed overhead. The trail is scheduled to reopen for users in time for Memorial Day weekend.

Upcoming nighttime work

    Crews will continue to work at night east of Foster Island and near the westbound SR 520 off-ramp to Lake Washington Boulevard. Here’s what to expect in the coming weeks:

    • Westbound SR 520 right-lane closures from floating bridge to Montlake Boulevard: Crews will pour concrete into the casings to make bridge shafts. In order to access the pour locations, crews must close the right lane of westbound SR 520 from the floating bridge to Montlake Boulevard, and then pump concrete from atop the West Connection Bridge. These closures are anticipated to continue for the next few months from 9 p.m. to 6 a.m. on Monday through Thursday and Saturday nights. Nearby neighbors may see light plants and hear activities from concrete trucks near the West Connection Bridge.
    • Isolation bearings: Beginning the week of Feb. 29, crews will begin to install isolation bearings on top of the columns. Isolation bearings are a key safety component of the WABN structure that allow the bridge’s deck and support columns to move independently during an earthquake, reducing the chance of structural damage or collapse.
    • Installing supports: Crews are currently installing temporary falsework supports, to hold bridge girders in place while crews construct the bridge deck for the permanent bridge. In order to install the supports at night, crews must use lights to illuminate the work zone.
    • Pouring columns east of the temporary work bridge: Beginning as early as this month, crews will pour columns at night, east of the temporary work bridge. Crews will continue to use right lane closures of westbound SR 520 (noted above) between the floating bridge and Montlake Boulevard, nightly from 9 p.m. to 6 a.m. Monday through Thursday nights and occasional Saturdays, in order to access the columns from the West Connection Bridge. Crews will also continue to illuminate the work zone in order to safely pour columns.
    • Ramp removal: Crews are continuing to remove the former westbound SR 520 off-ramp to Lake Washington Boulevard with non-impact construction equipment. At night, crews will continue hauling out debris from the site to prepare for further demolition activities the following day.

    Pile removal and installation

    Starting the week of Feb. 22, steel pile removal and installation activities resume on Lake Washington.

    • Pile installation: Now that portions of the former westbound off-ramp to Montlake Boulevard have been removed, crews will construct platform extensions from the work bridge to install casings and pour columns for the new WABN structure west of Foster Island.
    • Pile removal and installation: With the permanent bridge columns now poured east of Foster Island, crews will begin to remove the work-platform extensions in that area to make room for placing permanent bridge girders in March. At other key locations in this area, crews will install piles to provide additional support for placement of girders.
    • Note: Crews will use both vibratory and impact hammers to remove and install piles. Impact hammer work is restricted to 8 a.m. to 5 p.m. weekdays and 9 a.m. to 5 p.m. on weekends. This work will continue on Lake Washington through spring 2016.

    Continued bicycle/pedestrian detour on Montlake Boulevard

    The 24th Avenue East bridge over SR 520, closed for construction since September, is planned to reopen Jan. 6, 2016. The overpass will be part of a new off-ramp to East Lake Washington Boulevard – via 24th Avenue East. The new off-ramp will replace the function of the existing westbound off-ramp to Lake Washington Boulevard, scheduled to be removed later in 2016.

    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 WSDOT 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 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 10 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

    Click image for larger, printable version.
    (pdf 262 kb)

    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.