Whether you’re planning a visit or you’re a resident looking to learn more, this blog post will provide you with essential information about the Washington State Floating Bridges, how they work, and what makes them so notable.
Floating bridges can be separated into two different types – permanent floating bridges and non-permanent floating bridges. The basic idea behind their construction is the same, to allow people or vehicles to cross bodies of water, but it’s their more precise purpose that differs.
Non-permanent floating bridges have their origins in wartime, dating back to the days of the Mongol Empire and ancient Greek, Roman, and Chinese civilizations. Armies needed a way to be able to get soldiers from one bank to the other without sending boats back and forth. The first floating bridge was simply a series of different boats that were lined up and had planks laid across them, allowing soldiers to pass over the boats to the other side of the water. Eventually, they transformed into what we would think of as pontoons today.
But what about permanent floating bridges? Permanent floating bridges are uncommon – so much so, in fact, that there are only about 20 of them in the world. And there are good reasons for that.
First, they’re only really necessary in very specific scenarios, essentially where traditional bridges aren’t feasible.
Second, a long list of environmental factors needs to be taken into account, including, among other things, wind direction and strength, water depth and currents, the type of bottom soil, and the nature of the land on each bank.
The fact that four of these unusual floating bridges are located in Washington State is fairly surprising. And, not only are there four floating bridges in Washington State, they are also some of the longest floating bridges in the world.
Three of the bridges span Lake Washington, the other connects to Hood Canal. Residents here probably take them all for granted, complaining about traffic and congestion, but visitors usually find them fascinating.
Let’s take a closer look at our local floating bridges.
What is a Floating Bridge and How Do Floating Bridges Work?
Floating bridges are normally used in situations in which engineers are working with bodies of water that are both very deep and very wide – this paired with soft bottom soil (whether of a lake or the ocean) makes ordinary bridges an impossibility. A floating bridge becomes the best alternative.
Floating bridges are made with wood, concrete, or steel – or a combination thereof – and the actual roadway part of the bridge rests upon the pontoon below. The pontoons are where the floating comes in. Pontoons are buoyant, water-tight vessels that are able to support a lot of weight.
There are two primary types of permanent floating bridges, and the main difference is in the pontoon design. A continuous pontoon bridge is made with a pontoon underneath the road that has been overlayed on top, and it is a single pontoon that stretches the entire length of the bridge. A separate pontoon bridge, on the other hand, is made up of many different pontoons that are attached, and the roadway is overlayed on top of all of them.
The complicated part of how floating bridges work is the way in which they are connected to the land. Engineers need to analyze the water, the banks, as well as the traffic on the waterways to be able to ensure that the bridge is secure and stable. The bridge needs to float after all, and that is no mean engineering feat.
Now that you know what floating bridges are and a little bit about how they work, it’s time to delve into the specifics of Washington State’s four floating bridges. Currently there is no toll.
Four Floating Bridges in Washington State
Four of the world’s 20-odd floating bridges are found in Washington State, and three in the Seattle area. The conditions here are perfect. for building a floating bridge when a conventional suspension bridge isn’t an option. Three bridges are in the Seattle Metropolitan area and one connects the mainland to the Olympic Peninsula.
Evergreen Point Floating Bridge
Lake Washington is too deep for a traditional bridge and the curved nature of the route means that a suspension bridge or fixed bridge isn’t feasible. A floating bridge is the best option for crossing the water, rather than driving around the lake.
The Evergreen Point Floating Bridge is officially named the Governor Albert D. Rosellini Bridge. It’s rarely called that and is usually referred to as the 520 Bridge, or SR 520 (SR = State Route). The bridge crosses Lake Washington from Seattle to the suburbs east of the lake (including Bellevue, Kirkland, and Redmond, and is approximately 7,500 feet long. It is the longest floating bridge in the world.
The original bridge was opened in 1963. As population growth continued to spread, it became obvious that a larger bridge would be in order. Planning for the replacement bridge began in 1997, and was opened in 2016. The new bridge, with the same name, has all the new construction safety standards incorporated, including wind and earthquake protections. The bridge is 7,710 feet in length, and at its midpoint is 116 feet, making it both the world’s longest and widest floating bridge.
The Evergreen Point Bridge is a toll bridge, with variable pricing. Currently, the range is $1.25-6.50. Check the Washington State Department of Transportation website for toll fees and payment options (here).
Lacey V. Murrow Memorial Bridge
Enabling traffic to flow from Seattle to Mercer Island, the Lacey V. Murrow Memorial Bridge isn’t quite as long as the Evergreen Point Floating Bridge. It comes in at a well-earned second place in the world’s longest floating bridges at 6,620 feet long (see photo top).
The bridge is an official landmark of the city of Seattle, as well as a National Historic Civil Engineering Landmark. The bridge’s namesake, Lacey V. Murrow was the second director of the Washington State Highway Department as well as a renowned US Air Force pilot.
The bridge was opened in 1940, and reconstructed and re-opened in 1993. There is currently no toll for crossing.
Homer M. Hadley Memorial Bridge
Homer M. Hadley Memorial Bridge was opened in 1989 after its plans were first proposed in the 1950s. The bridge is named after one of the designers of the Lacey V. Murrow Memorial Bridge, Homer M. Hadley.
The bridge runs parallel to the Lacey V. Murrow Memorial Bridge and was built to absorb traffic during the renovations of the latter. An incident connecting the two bridges occurred during the renovations of the Murrow Bridge when it sank – the disaster resulted in the severing of 17 of the 58 anchoring cables of the Hadley Bridge, causing major changes in plans.
Today, the Homer M. Hadley Floating Bridge is the fifth longest in the world, spanning 5,811 feet over Lake Washington and carrying traffic from Seattle to Mercer Island, just like the
Lacey V. Murrow Memorial Bridge.
Most residents don’t distinguish between the Homer Hadley and the Lacey Murrow Bridge, referring to both of them collectively with the broad reference of Mercer Island or I-90 floating bridge. There is no toll for either of these bridges.
Hood Canal Bridge
At 7.869 feet in length, the Hood Canal floating bridge is the third longest in the world. It connected the Olympic and Kitsap Peninsulas. This bridge has an additional feature not often seen – it opens at the center to allow vessels to pass through.
A major windstorm in 1979 caused a few of the concrete pontoons to break loose and a portion of the bridge sank. It was rebuilt and opened in 1982.
The bridge is the gateway to the Olympic Peninsula, and the cities of Port Townsend, Sequim, and Port Angeles. It also provides access to Olympic National Park and the state parks in Jefferson County.
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