Why is WSDOT replacing the SR 520 bridge?
SR 520 is a vital link across Lake Washington, carrying more than 115,000 vehicles and 155,000 people east and west each day. Since its construction in the early 1960s, the Portage Bay Bridge and the floating Evergreen Point Bridge and approach structures have aged. They are susceptible to catastrophic failure in the event of an earthquake or windstorm. Improvements have kept the bridges safe and functional, but the bridges won’t last forever.
The hollow bridge columns are as vulnerable to earthquakes as the Alaskan Way Viaduct. The floating bridge is vulnerable to wind and waves. The drawspan, anchor cables and pontoons could break or crack during windstorms, and the bridge could sink.
Where is the program site?
The program area extends along the SR 520 corridor from I-5 in Seattle to SR 202 in Redmond.
View a map of the program area.
What will replace the SR 520 bridge?
WSDOT will replace the existing four-lane bridge with a new six-lane bridge that includes two high-occupancy vehicle (HOV) lanes. It also will include a bicycle/pedestrian path and five lidded areas covering the highway to reconnect neighborhoods.
How was the plan selected?
In 2006 Gov. Chris Gregoire issued the Path Forward to Action: Findings on the Alaskan Way Viaduct and SR 520 programs, in which she endorsed the “4+2” replacement, four general-purpose lanes and two HOV lanes, as the most viable alternative for the SR 520 corridor.
Her endorsement came after an expert review panel extensively reviewed the program’s draft environmental impact statement, recalculated cost information and weighed public comments. During the 2007 legislative session, the state Legislature passed into law engrossed substitute Senate Bill (ESSB) 6099, which also endorsed the 4+2 replacement as the best choice for building a new bridge. WSDOT is completing a supplemental draft EIS, which will include more information about construction effects and mitigation, pontoon construction and west-side design.
What other alternatives were considered?
A four-lane bridge replacement was analyzed in the August 2006 draft EIS. This alternative is not being pursued further because it would not improve mobility in the corridor. More information about the four-lane alternative can be found in the draft EIS.
Early analysis of other alternatives found that the volume of traffic flowing across an 8-lane bridge replacement would create additional backups on an already congested I-5. To accommodate the additional traffic, significant improvements to I-5 would be necessary. An additional study in 2003 found that, even with tolls, expensive improvements to I-5 would still be necessary in order to reduce the expected backups onto I-5.
What is the No-Build Alternative?
All environmental impact statements include a "no-build alternative" as a comparison to the proposed build alternatives evaluated in the document. Typically, the no-build alternative assumes that the highway would remain the same as it is today. However, because the fixed spans of the Portage Bay and Evergreen Point bridges are aging and are vulnerable to earthquakes, and the floating portion of the Evergreen Point Bridge may sink in a windstorm, there is a reasonable probability that these bridges will not be usable in 2030 (the analysis year for the EIS). Two no-build scenarios were evaluated in the draft EIS: the continued operation scenario, and the catastrophic failure scenario.
How will the plan save time for commuters?
The new HOV lanes will improve traffic flow and save commuters time by reducing congestion for carpools, vanpools and buses. Wide shoulders will allow a safe place for disabled vehicles to safely pull off the highway. With disabled vehicles moved out of traffic, emergency vehicles can arrive sooner, and traffic is less interrupted.
Will the new bridge have a bike path?
Yes, the replacement program will include a bicycle/pedestrian path along the SR 520 corridor, safely separated from the highway.
Will the 4+2 replacement include light rail or other high capacity transit?
Planned initial high capacity transit on the new SR 520 corridor will be bus rapid transit. Bus rapid transit Transit agencies are responsible for determining transit service in the SR 520 corridor.
See the SR 520 High Capacity Transit Plan (pdf 3 mb) for more information.
How much does the program cost?
In November 2008 WSDOT announced update cost estimates for the SR 520 Bridge Replacement and HOV Program, including three west side options developed through a mediation process, as well as costs for the Eastside Transit and HOV Project, the floating bridge and the pontoon construction site.
The latest cost estimate ranges between $4.56 billion and $6.67 billion, depending on which west side design option is chosen. Updated cost estimates have been adjusted for risk and inflation and are shown in year of expenditure dollars.
top
What is the SR 520 Bridge Replacement and HOV Program timeline?
What is the program timeline?
- 2009 - Begin innovative pontoon construction testing effort.
- 2010 - Begin pontoon construction at existing facility in Tacoma.
- 2010 - Begin new pontoon site construction in Grays Harbor.
- 2010 - Begin construction on the Eastside.
- 2012 - Begin construction of new floating bridge.
- 2014 - Open four-lane bridge to drivers.
- 2016 - Open six-lane bridge to drivers.
What has been accomplished so far?
2006 - Released the draft environmental impact statement and held two public meetings to gather public comments; an Expert Review Panel reviewed program cost estimates and implementation plan; Gov. Gregoire selected the six-lane bridge in a 4+2 configuration.
2007 - Mediation process begins; independent review of alternative project options begins; continued working with Eastside communities to develop designs that would improve community connections; draft high-capacity transit plan released.
2008 - New project finance plan released; project team continues to develop floating bridge and Eastside design; mediation group identifies three west side design options to be further evaluated in the supplemental draft environmental impact statement; Gov. Gregoire announces accelerated program schedule; Gov. Gregoire signs bills authorizing tolls statewide (House Bill 1773) and establishing a tolling implementation committee for SR 520 (House Bill 3096).
top
How will WSDOT fund the SR 520 Bridge Replacement and HOV Program?
The Washington State Legislature has secured a variety of state and federal funding sources, including tolling the existing floating bridge beginning in 2010, to help pay for the SR 520 program:
| Funding source |
Amount |
| State gas tax |
$552 million |
| Federal funds |
$242 million |
| SR 520 Account (tolling and future federal funding) |
$1,200 million |
| Total funded |
$1,994 million |
| Unfunded |
$2,656 million |
| Total program |
$4,650 million |
*In the May 2009 SR 520 tolling bill,
ESHB 2211, Gov. Gregoire and the Washington State Legislature identified a target SR 520 program cost of $4.65 billion.
WSDOT has also received an
Urban Partnership grant from the United States Department of Transportation to improve traffic through
tolling,
technology and traffic management,
transit, and
telecommuting.
This grant provides the following:
- Up to $41 million to purchase 45 new buses and other transit improvements along the SR 520 corridor.
- $86 million to develop new traffic management technology, including and traveler information systems to support tolling operations on the SR 520 Bridge.
- Up to $11.6 million to improve state and county ferry service.
top
Will WSDOT toll the SR 520 floating bridge?
In May 2009, Gov. Gregoire signed ESHB 2211, which authorizes tolling on the SR 520 bridge beginning in 2010. Tolling the SR 520 bridge next year allows WSDOT to secure revenue in order to begin pontoon construction in 2010, which is critical to replacing the SR 520 bridge by 2014.
Previous tolling legislation includes House Bill 1773, which set statewide guidelines for the implementation and use of tolls on state highways, and House Bill 3096, which authorized tolls on SR 520. House Bill 3096 also created a Tolling Implementation Committee to work with the public to evaluate a variety of tolling scenarios.
The Tolling Implementation Committee evaluated tolling for financing the SR 520 Bridge Replacement and HOV Program, engaged citizens and regional leadership in the evaluation, and enhanced understanding of tolling alternatives. The committee hosted a series of public outreach events and input opportunities related to tolling in the SR 520 corridor during summer 2008, and reported to the Governor and Legislature in January 2009.
How will you use tolls on SR 520?
Modern toll-collection technology has made tollbooths a thing of the past. Drivers will pay tolls without stopping, using a vehicle-mounted transponder and electronic overhead readers mounted in roadway structures over each lane. The readers will recognize individual transponders and deduct the toll from the driver’s prepaid account. Cameras equipped with license-plate reading technology could be used to collect tolls from vehicles that are not equipped with transponders.
Transponder technology and license-plate recognizing cameras are currently being used as part of WSDOT’s Good to Go! program to toll the new Tacoma Narrows Bridge.
What if a driver doesn’t have a transponder?
Cameras equipped with license-plate reading technology will be used to collect tolls from vehicles that are not equipped with transponders.
When do you plan to implement tolling?
We plan activate tolling on the SR 520 floating bridge in fall 2010.
What will the SR 520 tolls pay for?
Tolls are collected to cover bond payments associated with construction as well as for ongoing operations and maintenance costs.
How much will I pay in tolls?
It is up to the Washington State Transportation Commission to set the rates, and the Legislature to approve them.
Was the original SR 520 bridge tolled?
Yes, the SR 520 bridge was tolled from the time it was completed in August 1963, until it was paid off in June 1979. The tolls generated approximately $60 million.
top
How will the SR 520 Bridge Replacement and HOV Program protect the environment?
Will the SR 520 program improve the environment?
The project will include a number of features that will improve conditions over the current SR 520 facility:
- There will be stormwater treatment facilities to ensure stormwater from the highway meets the latest water quality regulations.
- New sound walls will substantially reduce noise levels for neighboring communities.
- The new bridge will have fewer columns (250 feet apart compared to today’s 100 feet).
- The R.H. Thomson Freeway “ramps to nowhere” near the Washington Park Arboretum will be removed.
- There will be a new bicycle/pedestrian path across Lake Washington.
- Sections of the road will be covered by a grassy lid at 10th Avenue E. and Delmar Ave E., and Montlake Boulevard in Seattle, and at Evergreen Point Road, 84th Avenue N.E. and 92nd Avenue N.E. on the Eastside to improve connections between neighborhoods.
How can I learn more about how the project will affect the surrounding natural and manmade environment?
The project proposes a wider bridge than what exists today. It is wider because it includes HOV lanes, shoulders and a new bicycle/pedestrian path. Some environmental effects linked to construction of a wider bridge will be temporary, while other effects could be longer lasting.
You can learn more about the temporary and permanent environmental effects in our draft environmental impact statement (EIS). Topics covered in the draft EIS include how construction of a wider SR 520 bridge could affect wetlands, parks, fish and wildlife, highway noise, air quality, neighborhoods, navigation channels in Lake Washington, and cultural and historic resources.
Will the project restore, enhance or preserve the areas of the environment that are disrupted by the project?
Yes, restoring the environment is integral to and inseparable from the project. That means the project team is working with tribal nations and state and federal regulatory agencies to make sure the project obtains necessary permits and complies with national and state environmental requirements such as the National Environmental Protection Act (NEPA) and State Environmental Protection Act (SEPA) requirements.
How will this project affect traffic noise in the neighborhoods near SR 520?
To reduce future traffic noise throughout the SR 520 corridor, proposed noise walls, ranging from 8- to 18-feet tall, would extend along the reconstructed SR 520 in Seattle and on the Eastside. Nearly all neighborhoods adjacent to SR 520 will experience less traffic noise. View planned noise wall heights and locations: Seattle, Eastside.
Will highway noise be reduced in nearby SR 520 neighborhoods when the project is complete?
Residents in most neighborhoods along the corridor east and west of Lake Washington will hear less noise once the project is built; however, some neighborhoods will not notice a reduction in highway noise. Noise levels in Laurelhurst/Webster Point and North Capitol Hill will remain virtually the same.
Are there any neighborhoods that will experience increased highway noise once the project is built?
Yes, one section of Bellevue, east of I-405 along NE 24th Street, might experience noticeable increases in highway noise.
Because this part of NE 24th Street is located on a hillside above SR 520, traffic engineers are unable to reduce noise levels with sound walls.
Will the project use "quieter" pavement?
WSDOT is currently studying different forms of quieter pavement to determine whether they would be effective in the Pugest Sound's driving and weather conditions. We installed a quieter pavement test section on the east side of Lake Washington in July 2007. Track the results alongside WSDOT.
How will traffic and transportation operate on the new SR 520 corridor?
The 4+2 bridge replacement will benefit bicyclists, pedestrians, HOV users, and transit riders in the following ways:
- A new bicycle/pedestrian path will run along the north side of the bridge, connecting Montlake and the University District to the Eastside near Bellevue.
- New HOV lanes from the I-5/SR 520 interchange to the existing HOV lanes east of I-405 will reduce traffic congestion.
- Improved transit stops will help make travel faster and more reliable.
Will SR 520 remain open to traffic when the new bridge is under construction?
Yes. The existing floating bridge will remain open while the new floating bridge is under construction.
The new bridge will be built to the north of the existing bridge. WSDOT currently recommends that the west approach of the Evergreen Point Bridge be constructed using a separate detour bridge. The detour bridge could be built to the south of the existing structure. Once completed, both directions of traffic would be shifted to the detour bridge, allowing the existing west approach to be used as a work bridge for the new facility. After the new structures are complete, traffic will move to them, and the detour bridge and old SR 520 floating bridge will be removed. The Lake Washington Boulevard ramps will likely be closed during construction.
Will traffic be able to cross Portage Bay when the new bridge is under construction?
Yes. WSDOT is considering the use of temporary work bridges to the north and south of the existing facility over Portage Bay. A work bridge would be built to the north in order to build the north half of the new facility. Then, the existing bridge would be removed and the south half of the new bridge would be constructed. Once the south half is completed, traffic would be shifted from the new north half to the new, fully constructed bridge and the work trestle will be removed.
Will the navigation channels be in the same locations as today, allowing most types and sizes of pleasure boats to cross on both the east and west side of Lake Washington?
The new bridge will reduce clearance for boat traffic from 44 feet to 25 feet on the west side of Lake Washington. The east side clearance will be increased from 57 feet to 70 feet, matching the clearance of the I-90 bridge. There will be no mid-span opening as there is today. Sailboats and very large motorboats and yachts will be unable to cross under the west end of the bridge but will be diverted to the east navigation channel. Most motorboats will continue to pass under the bridge on the west side. View a diagram of existing and future boat clearances.
top
Quick facts about the existing SR 520 bridge
What is the official name of the floating bridge?
The official name of the SR 520 floating bridge is the Governor Albert D. Rosellini Bridge.
How wide is the current bridge?
The current bridge is 60 feet wide.
How long is the floating section of the bridge?
The floating section of the SR 520 bridge is 1.42 miles (2,285 meters) long, making it the longest floating bridge in the world.
How many pontoons support the current bridge?
The current bridge is supported by 33 bridge pontoons. Each pontoon is about as long as a football field (360 feet) and 16 feet tall.
How many anchors hold the pontoons in place?
The bridge pontoons are held in place by 62 anchors attached with 2-3/16 cables. (Anchors on the pontoons that connect with the east and west approaches require thicker cables. Those cables are 2-3/4" inches thick.)
How much do the anchors weigh?
A standard achor for the SR 520 bridge pontoons weighs 77 tons, which is more than 10 male African elephants.
How deep is Lake Washington?
Lake Washington is 200 feet deep under the drawspan of the current floating bridge. The deepest point in Lake Washington is 214 feet deep.
When did the existing bridge open?
We opened the existing bridge to traffic on Aug. 28, 1963.
How long did the tolls last when the bridge opened in 1963?
We ended tolling on the existing bridge on June 22, 1979, less than 16 years after the bridge opened.
How many vehicles use the current bridge each day?
Every day, approximately 115,000 vehicles use the SR 520 bridge to cross Lake Washington.
How many vehicles did we expect to cross the existing bridge each day when we designed it?
The current bridge was designed to carry 65,000 vehicles per day.
What windspeed was the existing bridge designed to withstand?
The existing bridge was designed to withstand 50-70 mph winds.
Why do you close the bridge to traffic during severe windstorms?
We close the bridge to traffic in order to open the drawspan, which relieves pressure on the bridge from wind and wave action during windstorms.
The criteria for closing the bridge to traffic and opening the drawspan is 50 mph gusts sustained for 15 minutes. When a 40 mph gust is sustained for one minute, a warning alarm alerts crews to come to the bridge for inspection and monitoring.
As with all WSDOT bridges, our experienced crews can close the bridge anytime they deem it unsafe, or when there is a potential for damage.
You can check current conditions at the SR 520 bridge on the Web.
What repairs and retrofits have been made on the current bridge?
2006 - Replaced drawspan anchor bolts sheared off during storms earlier in the year. The anchor bolts hold the drawspan closed.
2000 - Emergency repairs to column damage.
1998 - Seismic retrofit, cable post tensioning, wave deflectors.
1997 - Pontoon bolts and crack seal.
1993 - Storm damage repair of pontoon cracks.
How many cracks in the bridge pontoons have been repaired?
Crews have repaired more than 30,000 linear feet of cracks since the 1993 Inaugural Day storm.
Floating bridge facts
How do floating bridges float?
Floating bridges are made of large water-tight concrete pontoons connected rigidly end-to-end, upon which the roadway is built. Despite their heavy concrete composition, the weight of the water displaced by the pontoons is equal to the weight of the structure (including all traffic), which allows the bridge to float.
How are floating bridges constructed?
Individual bridge pontoons are usually built on dry land next to a waterway, then floated and towed like barges to the bridge site. They are connected to grounded approach structures on each end, starting at the edge of the floating structure and then pieced together toward the eventual bridge’s center. The pontoons are held in place by enormous steel cables generally hundreds of feet long that are connected to anchors buried deep in the lakebed. For more information and to view an example of a floating bridge under construction, visit the Hood Canal Bridge Project Web site.
Why is WSDOT building a floating bridge over Lake Washington as opposed to a conventional suspension bridge?
A conventional suspension bridge over Lake Washington would not work for several reasons:
- Suspension bridges need to travel in a fairly straight line. Because SR 520 is a curved corridor, a suspension bridge would not be possible.
- The deepest point in Lake Washington is 214 feet deep, and the bridge’s support towers would have to be approximately 630 feet in height, nearly the height of the Space Needle, to support the bridge. These massive towers would be out of character with the surroundings because it would create more noise and block views.
- Conventional fixed bridges, such as the new bridge over the Tacoma Narrows, are expensive to build in deeper waters with soft beds, such as Lake Washington.
Where are other floating bridges?
Washington State is the floating bridge capitol of the world with the four longest and heaviest floating bridges. They are the SR 520 Evergreen Point Bridge, the I-90 Lacey V. Murrow Bridge, the I-90 Homer M. Hadley Bridge, and the SR 104 Hood Canal Bridge.
In 1957, a concrete floating bridge was built across Lake Okanagan at Kelowna in south central British Columbia, Canada. Its floating length is 2,100 feet (640 meters) and its design is very similar to the Lacey V. Murrow Bridge.
The Demerara Harbor Bridge in Georgetown, Guyana, is another floating bridge. It is made of steel pontoon units and extends 6,074 feet (1,851 meters). Norway has two large floating bridges – the Bergsoeysund Floating Bridge in Kristiansund, More og Romsdal and the Nordhordland Floating Bridge. Another long-time floating bridge site is the Galata Floating Bridge in Istanbul, Turkey.
How do earthquakes affect the floating section of the SR 520 bridge?
The floating section of the SR 520 bridge is not affected directly by ground shaking from earthquakes because is built on pontoons that are anchored to the bottom of Lake Washington. Some very deep low-frequency earthquakes can cause a seiche, or a surface wave similar to a tsunami. A seiche in Lake Washington could cause the floating bridge to bend and heave at the lake surface, adding large loads of pressure to the pontoons and anchor systems. A seiche in Lake Washington could also create an underwater landslide that could cause the pontoon anchors to slip or break.
Typically the waves from a seiche create less stress in the pontoons than wind-induced waves from a storm that occurs once every 100 years.
How do windstorms and waves affect floating bridges?
Wind and wave forces are typically the controlling forces in the design of floating bridges. A major factor in wind and wave effects on floating bridges is called the fetch. The fetch is the unobstructed clear distance over the water that wind can travel to the bridge. The longer the fetch, the higher the wind and wave forces will be. In Lake Washington the critical fetch is to the southwest of the bridge, since the largest storms historically come from the southwest. Wind and wave forces cause the pontoons to bend, heave and twist, creating large stresses in the pontoons and anchor system. If a 100-year storm event were to occur, the pontoons are designed to prevent large cracks from developing that would allow water to leak in and sink the bridge.
top
How can I get involved?
How has the public been involved in the SR 520 Bridge Replacement and HOV Program?
Public involvement in the SR 520 Bridge Bridge Replacement and HOV Program has been and continues to be an essential element of the program. We regularly provide project progress information to the public on our Web site and at public events. To date, our activities have included project-area tours; public meetings and open houses; jurisdictional, community and organizational briefings; committee meetings; community workshops; and neighborhood roundtables.
Public opinion is important to WSDOT. Project planners depend on input from people who live and work near the project site. Comments and feedback from community members, residents, businesses, organizations and jurisdiction leaders help us to design a facility that works for the people who live nearby and/or use the corridor.
How does the project team reach out to minority populations and people with limited English proficiency?
WSDOT uses an array of public outreach methods to identify and inform all people who use the roadway and/or live along the corridor including minority, low-income and limited-English-speaking populations. In addition to working with local community centers, we provide project fact sheets in several languages including Spanish, Russian, Chinese and Vietnamese at all of our outreach events and on our Web site.
WSDOT advertises public outreach events in newspapers published for minority audiences, and project information tables at a variety of locations and community events throughout Seattle and the Eastside. Some of these locations and events include Seattle’s Lunar New Year celebration in the International District, Crossroads Mall, farmers markets on the Eastside and the Central Area Community Festival. In addition, the project team provides American Sign Language interpretation and translation services at all public events upon request. Learn more about the project's core public involvement and agency coordination outreach efforts in Appendix B (pdf 629 kb) of the draft EIS.
Are there still opportunities for the public to get involved?
Yes, the thoughts and opinions of all community members, whether they use the bridge every day or simply work or live near it, are very important to WSDOT. Opportunities to get involved will continue throughout the life of the project. For information on how to contact the project team, visit the Contact Us page. Also visit the Project Calendar for information on upcoming events and to view material from past events.