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Floating Bridges


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WA has three floating bridges.   Two across Lake Washington from the east side into Seattle, or from Seattle to the east side if you prefer.   These are freshwater bridges.

There is another called the Hood Canal Bridge that spans a part of Puget Sound (salt water).  This happens to be the longest salt water floating bridge in the world, perhaps the universe!!  

The floating bridge is a unique structure with pontoons underneath filled with air to keep the bridge floating on the water.   Concrete is the main material used.  

There have been a few instances of the bridges sinking due to high winds and waves.   The I-90 bridge was under maintenance during a rough storm and someone left the access to the pontoon open.   It filled with water and took a section or two down.  There used to be just one bridge there but another was built to take care of one way traffic.   It wasn't too long after the second bridge became operational that the the other sank.   So we still had a working bridge, just half the capacity as before but the same as some time before that.   Apparently something similar happened to the Hood Canal Bridge.  

The WA Highway 520 bridge is pictured below going across Lake Washington from Bellevue to UW.  Husky Stadium is at the end of the bridge on the upper right.   Puget Sound is seen at the top of the photo. 

SR 520 Floating Bridge and Landings Project - Complete Summer 2017 | WSDOT 

I just thought this might be interesting to the folks on the board.   The bridges are a unique feature in the PNW.  They are kind of fun to drive across.   They used to have a section in the middle (I think Hood Canal still does) that would open to boat traffic.   The bridges on Lake Washington no longer have that feature, I guess they just go around.   You can take a boat to Puget Sound through the Ballard Locks from Lake Washington but I don't think there is any real big boat traffic that does this.   So they probably head towards shore to go under the bridge as shown. 

The lake is blue in this picture.   It does not often look like that.  This must have been taken on one of the rare non overcast days.  


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