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State Route 520 Bridge Pontoons to Float From Aberdeen Next Weekend

Pontoon towing update

  • 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 V-NW
Aug. 19, 2012:  Pontoon V-SW
Aug. 22, 2012:  Pontoon U
Sep. 22, 2012:  Pontoon V-NE and Pontoon V-SE
Sep. 30, 2012:  Pontoon U-NE and Pontoon U-SE
Feb. 2, 2013:    Pontoon U-NW and Pontoon U-SW


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.

  • Constructed in Aberdeen facility (10) and Tacoma facility (44)
  • Weight: 2,500 – 2,820 tons

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