Second cycle of SR 520 pontoons leave the Aberdeen casting basin on April 28-29
- Crews successfully floated out six new pontoons from the casting basin in Aberdeen, WA.
- Check out photos of the float-out.
- Watch our video on YouTube.
SR 520 open houses
- Thanks for joining us in at open houses in Seattle and Bellevue!
- Open house materials are posted in our Project Library.
New pontoon update page
Why is WSDOT
building new pontoons?
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
WSDOT is moving forward with pontoon construction as part of the replacement of the SR 520 bridge. Pontoons will be built in six cycles in the casting basin in Aberdeen. After each cycle is completed, the pontoons will be inspected, outfitted, and towed to Lake Washington, where they will be connected together to form the floating foundation for the new SR 520 bridge.
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.
Project signage will reflect the cost of construction engineering, project bid award and sales tax.
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?
For comments and questions about the project, or to be added to the mailing list or e-mail list, please e-mail email@example.com.
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
999 3rd Avenue, Suite 900
Seattle, WA 98104
back to top