Updated: May 21, 2013
Follow along with WSDOT as we continue to build, tow, and assemble pontoons for the new SR 520 floating bridge.
Diagram showing the approximate configuration of all 77 pontoons for the new floating bridge. Last updated May 21, 2013.
Pontoon towing update
- On Monday, May 20, supplemental Pontoon QSW completed its journey from Aberdeen to Tacoma. This pontoon will be outfitted and prepared for final assembly on Lake Washington.
- Between April 28-29, a total of six pontoons were towed out of the casting basin in Aberdeen. Watch video and check out photos of float-out.
- Longitudinal Pontoon S and supplemental Pontoon QNW were towed to Tacoma earlier this month. These pontoons are being outfitted and prepared for final assembly on Lake Washington.
- The remaining cycle 2 pontoons in Grays Harbor will be towed to Tacoma or Lake Washington as construction progresses for the new floating bridge.
- On May 15, longitudinal Pontoon T (completed during the first pontoon construction cycle in Aberdeen during summer 2012) was towed to Lake Washington from Tacoma for modification work later this summer.
- Between Jan. 29-31, a total of six pontoons were towed out of the casting basin in Tacoma. Watch the time-lapse video on YouTube.
- Two of these pontoons were towed to Lake Washington on Saturday, Feb. 2.
- The four remaining pontoons will stay in Tacoma until additional longitudinal pontoons arrive on the lake.
- Check out photos of the float-out on our Tacoma Flickr page.
Pontoon transit route
Pontoons for the new floating bridge are being constructed in two different sites in Washington state: Aberdeen and Tacoma. When pontoon construction is complete and they are ready for assembly, they will be brought to Lake Washington through the Hiram M. Chittenden Locks in Ballard.
If you are interested in viewing the pontoons as they make their way to Lake Washington, see our map of suggested viewing locations (pdf 2.5 mb).
Build your own pontoons for the floating bridge
The floating bridge pontoons represent a key milestone in a critical safety project. Using the printable pontoon templates linked below, you can build your own bridge that follows our progress with the construction, transport and final positioning of floating bridge pontoons.
- As we complete the construction of each pontoon and bring them to Lake Washington, we will post new templates here. Each pontoon is labeled according to its location within the final bridge structure.
- For each pontoon, download and print the template file (each pdf is approximately 400 kb), cut along the indicated lines, and then fold your pontoon for final construction.
- We will maintain the links for each pontoon template, so that you can catch up with any you might miss.
Aug. 11, 2012: Pontoon V
Aug. 14, 2012: Pontoon W
Aug. 18, 2012: Pontoon VNW
Aug. 19, 2012: Pontoon VSW
Aug. 22, 2012: Pontoon U
Sep. 22, 2012: Pontoon VNE and Pontoon VSE
Sep. 30, 2012: Pontoon UNE and Pontoon USE
Feb. 2, 2013: Pontoon UNW and Pontoon USW
Types of pontoons
The new SR 520 floating bridge will be supported by three types of concrete pontoons:
Longitudinal pontoons (21)
These are the largest pontoons at approximately 360 feet long. They form the backbone of the bridge and support the roadway superstructure.
- Constructed in Aberdeen facility
- Weight: 11,100 tons
Cross pontoons (2)
These mark the ends of the floating bridge section and the transition to the East and West Approach structures.
- Constructed in Aberdeen facility
- Weight: 10,100 - 10,550 tons
Supplemental stability pontoons (54)
These smaller pontoons help stabilize and support the weight of the new floating bridge by joining to larger longitudinal pontoons.
- Constructed in Aberdeen facility (10) and Tacoma facility (44)
- Weight: 2,500 - 2,820 tons