The bridge is 4750 meters.
Floating bridge of concrete and steel may seem very unusual and sometimes even impossible, but there are twenty such bridges in the world, five are located in Washington state.
Four of them are the longest pontoon bridge in the world.
Pontoon bridges, also known as pontoon are usually temporary structures. They were built of wood during emergencies, including war. Wooden rafts, and sometimes boats were tied with string and covered with flat boards, allowing you to cross rivers and ponds. Pontoon bridges were used in many battles throughout history, including the Second world war and even the Iran-Iraq war.
The longest permanent floating bridge — evergreen point SR 520 crossing Lake Washington in Seattle. On a pontoon bridge with a length of 4750 meters in the moving state Route 520. The second longest bridge in the world is a bridge-a memorial to Lacey V. Murrow length 2020 meters. It crosses the same lake just a few miles to the South.
But why was it built pontoon bridges? The answer is tricky geographical position of lake Washington. The lake bottom is too soft for ordinary bridge piers and for the construction of a suspension bridge would require a tower of enormous height, that would be too expensive and inappropriate.
The idea of a floating bridge across Lake Washington was first proposed by the engineer Homer Hadley in the 1930s. During the First world war, Hadley worked for the company who has developed a sustainable concrete barges. Well all having considered, he suggested the idea to connect the hollow concrete barges both shores of the lake. Floating bridge Hadley was a great success, and the state of Washington to use the project for future bridges. The second bridge evergreen point opened in 1963 and became the longest in the world. The third pontoon bridge decided to name in honor of the designer of Homer Hadley. As a result, today lake Washington, is home to three of the five longest floating bridges in the world.
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