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Evergreen Point Floating Bridge
The Evergreen Point Floating Bridge, also known as the 520 Bridge and officially the Governor Albert D. Rosellini Bridge, is a floating bridge that carries Washington State Route 520 across Lake Washington from Seattle to its eastern suburbs. The 7,710-foot-long (2,350 m) floating span is the longest floating bridge in the world, as well as the world's widest measuring 116 feet (35 m) at its midpoint. It is a toll bridge and uses electronic collection.
The bridge opened in April 2016 and replaced the original Evergreen Point Floating Bridge at the site, which was 130 feet (40 m) shorter and four lanes wide. The original bridge was vulnerable to earthquakes and strong wind events, which would frequently shut down traffic. Planning for a replacement began in 1997 and was approved in 2011; the $4.65 billion budget was derived from state gas taxes and federal sources, as well as toll revenue. Construction of the 77 concrete pontoons began in 2011 and on-site assembly began in 2014.
The Evergreen Point Floating Bridge carries six lanes of traffic—including two lanes for high-occupancy vehicles—and has a multi-use trail for cyclists and pedestrians on its north side. It also carries bus traffic and is designed for a future retrofit that would add light rail service.
The original Evergreen Point Floating Bridge, also named for state governor Albert D. Rosellini, opened on August 28, 1963, carrying the four-lane State Route 520 (at the time designated temporarily as the Evergreen Point branch of Primary State Highway 1 until the 1964 state highway renumbering). The 7,578-foot-long (2,310 m) floating span consisted of 33 pontoons and cost $24.7 million to construct (equivalent to $254 million in 2024); the bridge carried four lanes of traffic, separated by a curb that was later replaced with a simple Jersey barrier; at the center was a drawspan that opened for large vessels traversing the lake. The original bridge would also close to traffic during sustained wind gusts of 50 miles per hour (80 km/h) or higher for more than 15 minutes.
Due to increased traffic generated by rapid growth of the Eastside area, bridge replacement was explored as early as 1969, when building a parallel span was explored and rejected. The Eastside is also served by the Interstate 90 floating bridges completed in 1940 and 1989, carrying traffic across Mercer Island to and from Bellevue.
The original Evergreen Point Floating Bridge was designed before the implementation of modern earthquake engineering standards, with vulnerabilities in its hollow support structures that could have failed in a major earthquake. Additionally, near the end of its lifetime, vibrations induced by storm surges and strong winds were able to compromise the aging drawspan, anchor cables, and pontoons, leading to structural failure in a major storm. Even if the storms were below the maximum threshold for failure to occur, Washington State Department of Transportation (WSDOT) would still close the floating bridge to traffic. Although the original bridge carried two lanes of traffic in each direction, it did not include shoulders or pedestrian and bicycle infrastructure. The lack of a shoulder led to traffic congestion in the event of an accident, which would block one or two lanes in a given direction and block emergency services from accessing the bridge.
Planning of the replacement bridge started in 1997 with a cross-lake study conducted by the state Department of Transportation. The study followed several others in the late 20th century to find solutions to traffic on the SR 520 floating bridge, with most proposals rejected after heavy opposition from communities on both ends of the bridge.
The preferred alternative for the bridge's design, with four general-purpose lanes and two HOV lanes, was announced by WSDOT in April 2010. Alternative options included the construction of a southbound onramp from the I-5 express lanes, the addition of light rail to the project, and an eight-lane bridge. The final environmental impact statement for the project was issued in 2011, allowing for construction of the pontoons to begin the following year.
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Evergreen Point Floating Bridge
The Evergreen Point Floating Bridge, also known as the 520 Bridge and officially the Governor Albert D. Rosellini Bridge, is a floating bridge that carries Washington State Route 520 across Lake Washington from Seattle to its eastern suburbs. The 7,710-foot-long (2,350 m) floating span is the longest floating bridge in the world, as well as the world's widest measuring 116 feet (35 m) at its midpoint. It is a toll bridge and uses electronic collection.
The bridge opened in April 2016 and replaced the original Evergreen Point Floating Bridge at the site, which was 130 feet (40 m) shorter and four lanes wide. The original bridge was vulnerable to earthquakes and strong wind events, which would frequently shut down traffic. Planning for a replacement began in 1997 and was approved in 2011; the $4.65 billion budget was derived from state gas taxes and federal sources, as well as toll revenue. Construction of the 77 concrete pontoons began in 2011 and on-site assembly began in 2014.
The Evergreen Point Floating Bridge carries six lanes of traffic—including two lanes for high-occupancy vehicles—and has a multi-use trail for cyclists and pedestrians on its north side. It also carries bus traffic and is designed for a future retrofit that would add light rail service.
The original Evergreen Point Floating Bridge, also named for state governor Albert D. Rosellini, opened on August 28, 1963, carrying the four-lane State Route 520 (at the time designated temporarily as the Evergreen Point branch of Primary State Highway 1 until the 1964 state highway renumbering). The 7,578-foot-long (2,310 m) floating span consisted of 33 pontoons and cost $24.7 million to construct (equivalent to $254 million in 2024); the bridge carried four lanes of traffic, separated by a curb that was later replaced with a simple Jersey barrier; at the center was a drawspan that opened for large vessels traversing the lake. The original bridge would also close to traffic during sustained wind gusts of 50 miles per hour (80 km/h) or higher for more than 15 minutes.
Due to increased traffic generated by rapid growth of the Eastside area, bridge replacement was explored as early as 1969, when building a parallel span was explored and rejected. The Eastside is also served by the Interstate 90 floating bridges completed in 1940 and 1989, carrying traffic across Mercer Island to and from Bellevue.
The original Evergreen Point Floating Bridge was designed before the implementation of modern earthquake engineering standards, with vulnerabilities in its hollow support structures that could have failed in a major earthquake. Additionally, near the end of its lifetime, vibrations induced by storm surges and strong winds were able to compromise the aging drawspan, anchor cables, and pontoons, leading to structural failure in a major storm. Even if the storms were below the maximum threshold for failure to occur, Washington State Department of Transportation (WSDOT) would still close the floating bridge to traffic. Although the original bridge carried two lanes of traffic in each direction, it did not include shoulders or pedestrian and bicycle infrastructure. The lack of a shoulder led to traffic congestion in the event of an accident, which would block one or two lanes in a given direction and block emergency services from accessing the bridge.
Planning of the replacement bridge started in 1997 with a cross-lake study conducted by the state Department of Transportation. The study followed several others in the late 20th century to find solutions to traffic on the SR 520 floating bridge, with most proposals rejected after heavy opposition from communities on both ends of the bridge.
The preferred alternative for the bridge's design, with four general-purpose lanes and two HOV lanes, was announced by WSDOT in April 2010. Alternative options included the construction of a southbound onramp from the I-5 express lanes, the addition of light rail to the project, and an eight-lane bridge. The final environmental impact statement for the project was issued in 2011, allowing for construction of the pontoons to begin the following year.