Tuesday, October 27, 2015

State’s newest floating bridge now all decked out

 By Haylee Morse-Miller

We haven’t waved a green flag yet over the new SR 520 floating bridge.  But with last week’s final concrete pour for the bridge’s roadway, it’s only a matter of months before drivers are cruising across Lake Washington on the new, six-lane span.

We’ve completed tons of work – many tons of work – since project construction began four years ago. Hundreds of thousands of tons of concrete have gone into building the bridge’s pontoons, anchors, roadway deck, high-rise piers, and support columns. Just one of the 21 longitudinal pontoons for the new bridge weighs 11,000 tons, or as much as 23 Boeing 747s.

The final deck pour in progress on Oct. 22.

So pouring the last of this concrete to finish the nearly 2-mile-long roadway surface is a big milestone for the SR 520 Floating Bridge and Landings Project. It’s now physically possible for vehicles to cross the entire length of the floating bridge, from Medina all the way to the existing west approach bridge in Seattle. A lot more work remains, however, before traffic actually switches over from old bridge to new. Here are some of the key tasks we’ll be tackling before we open the new bridge next spring.

Crews lower the foundation for a noise wall on
the bridge’s east approach near Medina.
Bridge barrier and noise wall installation: More than 26,000 feet of traffic barrier will be placed along the entire length of the bridge. Also, concrete noise walls will be installed along the bridge’s east approach to reduce the traffic noise heard by nearby residents in Medina.

A barge deposits rock ballast into a pontoon.

Pontoon ballasting: Ballast rock is being placed inside the pontoons to ensure that the pontoons all sit at the same height in the water. In all, some 70,000 tons of the ballast rock, hauled in by barge, will be added to the pontoons.


Stormwater drainage pipes are part of the stormwater treatment
system to capture roadway runoff from the bridge. 

Stormwater drainage system installation: Catch basins along the roadway and piping that runs along the underside of the roadway deck will capture roadway runoff, lessening the environmental impact of the bridge on Lake Washington.

Outside view of the LEED Silver certified bridge
maintenance facility.
Some of the 300 miles of electrical wire that will
be used on the bridge – enough wire to stretch
from Seattle to Idaho.

Bridge maintenance facility construction:
A new bridge-maintenance facility is under construction below the East Approach of the bridge, on the Medina shoreline. This facility will house maintenance and repair equipment for the bridge and allow crews to quickly respond to any bridge-maintenance needs that arise.


Connecting bridge safety and management systems: These are the invisible hands that keep traffic flowing, including fire-safety systems, bridge sensors, and electronic traffic signs, like those showing variable speed limits.  


A rendering of the bicycle/pedestrian path on the bridge,
including one of the decorative sentinels that mark the
ends of the bridge.


Completion of architectural elements: Crews will install bridge lighting and decorative “sentinels” that mark the east and west ends of the longest floating bridge in the world. On the bridge’s 14-foot-wide bicycle and pedestrian path, we’ll finish installing rest areas/viewpoints, or “belvederes,” as well as nearly 8,500 feet of railing.

You can follow the progress of our final bridge-building activities as we count down to project completion. View this bridge-commissioning graphic on our website – and start to get excited about crossing the world’s longest floating highway in spring 2016!


Curt Nichols said...

How long until the bike/ped path is connected to surface streets on both ends?

WSDOT said...

The bicycle and pedestrian path will open in spring 2016 when the rest of the floating bridge opens, and will reach Seattle in summer 2017. In spring 2016, it will connect to surface streets on the Eastside only, providing an out and back path on the floating bridge. When the West Approach Bridge North is completed in summer 2017, the bike/pedestrian path will provide access to 24th Avenue East in Montlake.

Dan said...

Why will it take a whole extra year to connect the bike/pedestrian path? Seems like we could use that functionality a bit earlier.

WSDOT said...

The 14-foot-wide regional shared-use bicycle/pedestrian path is opening in phases as the new sections of the SR 520 bridge are complete. The path on the floating bridge, which will extend from the current eastside path to the end of the floating bridge, is scheduled to open in spring 2016 when the floating bridge opens to traffic. The West Approach Bridge North will connect the path to Montlake and WABN is not scheduled to open to traffic until summer 2017. Our bicycle/pedestrian folio on our website illustrates how the new path will open in phases and connect to existing paths on both sides of the lake.

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