I’ve never seen such a proliferation of floating bridges until I came out to the Pacific Northwest. We have many of them out here, including the two connectors across Lake Washington – SR-520 and I-90. It’s cheaper to build a bridge on pontoons than a standing bridge, and that’s the method planners have chosen, including the upcoming 520 replacement bridge.
A really cool part about a floating bridge is how the bridge affects waves on the water; during a storm, one side of the bridge will be rocking, while the other side calm as if nothing is happening. During a recent trek across the bridge during a particularly windy day that took out power in West Seattle, I witnessed the following…
Note how choppy the right side is, but the left side appears unaffected. The pontoons block the wind and waves from affecting Lake Washington north of 520.
Here’s another picture of how the waves of water were actually crashing onto the road itself. It was an interesting drive.