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SR 520 Bridge Program - Pontoon Tracking and Bridge Assembly Activities

Updated: April 16, 2014

Follow along with WSDOT as we continue to build, tow and assemble pontoons and make progress on the new SR 520 floating bridge on Lake Washington. 

Click on the below links to find the content you're interested in:

Pontoon tracker
Diagram showing the construction status and approximate configuration of all 77 pontoons for the new floating bridge. Last updated April 16, 2014. View a printable version  (pdf 200 kb).

Pontoon count:
    -Current number of pontoons on Lake Washington: 34.
    -Total number of pontoons constructed to date: 52.
    -Pontoons currently under construction: 14.

Pontoon towing update

  • Longitudinal Pontoon P arrived on Lake Washington in the evening on Sunday, April 13, following its multi-day journey from Grays Harbor.
  • Longitudinal Pontoon O arrived on Lake Washington on Wednesday, April 16. 
  • Crews also plan to tow two more longitudinal pontoons M and N, to Lake Washington in the near future, depending on marine weather conditions.

Note: While we strive to provide the most up-to-date information possible, pontoon towing details are always subject to change.

West Connection Bridge column construction progress

Diagram showing the current status of West Connection Bridge column construction on Lake Washington. Last updated: April 10, 2014. View a printable version (pdf 749 kb).

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 are 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. Templates will be added as pontoons arrive on the lake.

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
May 15, 2013: Pontoon T
Jun. 7, 2013: Pontoon A
Jul. 22, 2013: Pontoon TNW
Jul. 23, 2013: Pontoon TSW
Aug. 27, 2013: Pontoon TNE and Pontoon TSE
Aug. 30, 2013: Pontoon S
Oct. 17, 2013: Pontoon BSE
Oct. 20, 2013: Pontoon Q
Oct. 23, 2013: Pontoon R
Oct. 29, 2013: Pontoon BSW
Dec. 9, 2013: Pontoon SNE
Dec. 10, 2013: Pontoon SSE
Dec. 11, 2013: Pontoon SNW
Dec. 12, 2013: Pontoon SSW and Pontoon RSW
Dec. 13, 2013: Pontoon RNW and Pontoon RNE
Dec. 14, 2013: Pontoon RSE
March 13, 2014: Pontoon PSW
March 13, 2014: Pontoon PNW
April 13, 2014: Pontoon P
April 16, 2014: Pontoon O

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