Start of SR 520 pile driving this week
After last weekend’s traffic shift, crews are now able to begin constructing the new eastbound SR 520 bridge between Montlake and the SR 520 floating bridge. As part of this bridge’s construction, crews will begin pile driving and bridge removal activities as early as this week and continue into spring 2020.
What is pile driving and why is it necessary?
Pile driving is a construction method that uses vibratory and impact hammers to drive large steel piles into the ground to build support structures. As early as Thursday, Nov. 14, crews will begin to vibrate steel piles into the bottom of the lake and then hit them with an impact hammer to ensure that they are firmly installed.
The steel piles are necessary to construct a work platform or temporary “bridge” that will be used to remove the old, structurally vulnerable eastbound bridge and build a stronger replacement. Work bridges are commonly used in shallower waters like these areas of Lake Washington and the Arboretum. To limit the number of piles needed, crews will also use the old bridge as a temporary work platform.
What will I notice?
Pile driving is loud and causes vibrations. As early as this week, you may hear a repeated pinging sound, which is the sound of a large hammer hitting a steel pile. Pile driving is planned to take place between 8 a.m. and 5 p.m. on weekdays and 9 a.m. to 5 p.m. on weekends, as per the terms of the project’s Major Public Project Construction Noise Variance. When pile driving begins, crews plan to work six days a week – Monday through Saturday.
As crews begin removing the old bridge, saw-cutting and other removal activities will also produce noise. The noisiest part of the work — pile driving, saw cutting and removal — will occur during the daytime. During the nighttime, you may also hear noise and see light from trucks loading and hauling materials to and from the worksite.
Where will this work be?
Crews will first start at the west end of the old bridge and work east. After we close the Arboretum on-ramp later this year, we also will begin working near Foster Island and continue east as we remove the old bridge.
How will crews monitor noise and vibration?
Electronic noise and vibration meters record levels throughout the project area. Vibration monitors will collect data in the field and immediately alert the project team when readings are outside the set tolerances. Our 24-hour hotline, 206-775-8885, is the best way to report noise and vibration concerns and have questions addressed in the moment.
Go here for compete and most up-to-date construction information.
For questions, send email to sr520bridge@wsdot.wa.gov or call the 24-hour construction hotline (206-775-8885). The Montlake Project Information Center (2209 East North Street is open Mondays and Wednesdays noon to 6 p.m., Tuesdays and Thursdays 8 a.m. to noon, and the third Saturday of the month, 9 a.m. to noon.
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