May 2012
Pontoon project update – repairs on new pontoons to delay float-out
- Float-out of the first six concrete pontoons for the new SR 520 floating bridge will be delayed to allow crews time to make repairs and modifications after damaged concrete was found in one of the pontoons.
- Read more.
Progress at the site:
- Crews are constructing the first cycle of pontoons at the casting basin.
- Crews completed construction of the casting basin when the gate was installed in November 2011. The gate is 110 feet long, 30 feet tall and 10 feet thick, and weighs about 150 tons.
- Crews completed placing approximately 11,200 cubic yards of concrete to construct the pontoon casting basin floor.
- Crews completed excavating approximately 280,000 cubic yards of material that had to be removed to construct the basin.
- Crews completed driving the 874 piles needed to construct the pontoon casting basin's foundation, crane beams and bulkhead wall.
- View photos of the construction.
- Watch the work via the construction web camera.
Why is WSDOT
building new pontoons?
Overview
The aging SR 520 floating bridge on Lake Washington is vulnerable to windstorms and needs to be replaced. Moving forward with pontoon construction is a critical step towards construction of the new SR 520 bridge. The $367.3 million Pontoon Construction Project broke ground in February 2011 at a 55-acre site in Aberdeen. Since the groundbreaking, WSDOT and contractor Kiewit-General (K-G) have built a casting basin facility featuring a concrete batch plant, on-site water treatment, and a 4-acre casting basin, where pontoon construction is under way.
By the Pontoon Construction Project’s completion date in 2014, crews will have constructed 33 pontoons, 21 of which will be 360 feet long, 75 feet wide, and nearly 30 feet tall. These pontoons are the largest ever built in Washington. Once complete, each batch of pontoons will be floated out of the casting basin, inspected, and towed into place on Lake Washington where they will serve as the floating foundation for the new SR 520 bridge.
The End Result
If the SR 520 bridge were to fail, we would be prepared with pontoons to replace the floating section of the SR 520 bridge in a timely manner. If the SR 520 bridge does not fail, we would store the pontoons until they are needed for the planned replacement of the SR 520 bridge in 2014.
Project Benefits
The pontoons for the SR 520 bridge will improve safety and reliability. They will be designed and built to:
- Withstand a 1,000-year earthquake event.
- Withstand windstorms up to 89 mph.
Once complete, the new pontoons will support a wider, six lane roadway with dedicated transit/HOV lanes, wider, safer shoulders, and a 14-foot-wide bicycle/pedestrian path.
What is the project timeline?
- 2009 - Innovative pontoon construction testing.
- 2010 - Publish draft environmental impact statement.
- 2010 - Issue final environmental impact statement.
- 2011 - Receive Record of Decision from FHWA.
- 2011 - Begin and complete casting basin facility construction.
- 2012 - Begin pontoon construction.
- 2014 - Complete pontoon construction.
Financial Information
The project is funded through the following sources:
With the passage of ESHB 2211 in the 2009 legislative session, WSDOT has been authorized to collect tolls on the SR 520 floating bridge since 2011. This will expedite the replacement of the SR 520 floating bridge and has allowed us to move forward with construction.
How can I get more information?
Contact:
For comments and questions about the project, or to be added to the mailing list or e-mail list, please e-mail pontoons@wsdot.wa.gov.
To listen to a recording of the latest project information and leave a verbal comment or question, please call the project hotline at 1-360-591-8012.
To contact the project office by mail:
Pontoon Construction Project
600 Stewart Street, Suite 520
Seattle, WA 98101
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