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SR 520 Pontoon and Floating Bridge Updates

Latest update


April 14, 2014 – More pontoons arriving on Lake Washington

Another large concrete pontoon for the new SR 520 floating bridge arrived on Lake Washington on Sunday, April 13, and two others are scheduled to arrive later this week. Pontoon P reached the lake late Sunday afternoon following a three-day tow from Grays Harbor to Seattle.

Pontoon O, towed by the tugboat Ocean Ranger, left Grays Harbor Sunday morning and is expected to reach Shilshole Bay on Wednesday, April 16. The tugboat Nancy M will escort the pontoon from the Port Angeles area to Lake Washington. Pontoon M is slated to depart Grays Harbor on Wednesday, towed by the Ocean Ranger. Pontoon N is planned to depart Grays Harbor during the next weather window.

All four longitudinal pontoons are 360 feet long and weigh 11,000 tons.

Meanwhile, the SR 520 program is preparing to reach another major milestone this week with the planned float-out of the newest six pontoons built in Aberdeen. The first pontoon should float out of the Grays Harbor casting basin late Tuesday night, April 15, followed by the five other new pontoons early the next morning. These six pontoons represent the fourth of six cycles being built in Aberdeen. Pontoon construction there is now two-thirds complete, and 52 of the 77 total pontoons needed for the new floating bridge are complete.

Work is already beginning on the fifth cycle of pontoons in Aberdeen. All 33 pontoons built there are expected to be finished in 2015. The new floating bridge’s 44 other pontoons are being built at a casting basin along Tacoma’s waterfront.


Previous updates


March 28, 2014 - New SR 520 change order

The Washington State Department of Transportation on March 27, 2014, executed a $77.5 million change order with SR 520 floating bridge contractor Kiewit/General/Manson, A Joint Venture. The change order, announced in January by WSDOT, primarily addresses the additional construction time necessary to modify pontoons and deliver them to Lake Washington for floating bridge construction. As noted in January, the change order also established the schedule to open the new floating bridge to traffic by April 2016.

With passage of ESSB 6001, WSDOT has the authority to cover these increased costs with existing agency resources—primarily the toll bonding capacity within the existing toll rate structure. The change order can be viewed on WSDOT’s website.


Jan. 31, 2014 - Pontoon repairs successfully moving forward

Crews continue making progress on design modifications to four Cycle 1 pontoons built in Aberdeen. Design modifications on two pontoons were completed in dry docks last summer. The other two pontoons are being repaired on Lake Washington using a coffer cell to create a dry work environment.

The design modification work involves epoxy injections into pontoon cracks greater than .006 inches, crystalline waterproofing smaller cracks, transverse post-tensioning, and application of carbon-fiber wrap.

Last week crews completed repairs on the first of four ends of the remaining two massive, concrete pontoons that will help support the new SR 520 floating bridge. From inside a nearly 660-ton coffer cell attached to Pontoon V, construction workers completed crack repairs on one end of the 360-foot-long structure. After placing the coffer cell on the pontoon’s other end, crews began the next round of repairs on Thursday, Jan. 30.

While crews repair these cracks, they also take the opportunity to repair other construction anomalies previously identified during dive inspections of the pontoons. Some of these involve sections where steel rebar is exposed to water. To conduct these repairs, crews remove the concrete to expose the rebar and clean the steel with brushes and sandblasting. Workers then prepare the area for sealing by applying a special bonding agent to the cleaned rebar and surrounding concrete, followed by layers of a high-strength grout, and finally two to four layers of carbon-fiber wrap to help ensure a waterproof repair.



The procedures were developed by an outside expert and reviewed by WSDOT to ensure that the new, six-lane floating bridge lasts at least 75 years with standard maintenance along the way. We anticipate that the design modifications on these two remaining pontoons on Lake Washington will be complete this spring.


Jan. 8, 2014 - Latest pontoon change order and SR 520 Program budget updates announced


WSDOT Secretary Lynn Peterson briefs reporters on the status of the SR 520 program budget and change orders at WSDOT headquarters in Olympia.

Washington Transportation Secretary Lynn Peterson and SR 520 Program Director Julie Meredith announced that WSDOT’s pontoon design error is consuming much of the SR 520 program’s risk reserves. Future contract change orders and other potential construction risks are expected to require approximately $170 million in additional funding. Secretary Peterson said WSDOT has identified existing funding sources to cover these costs and keep the bridge-replacement project on track.

WSDOT hosted a briefing to share these findings with local media. You can view all of the materials, which are posted below:


Nov. 26, 2013 - Coffer cell launched into the lake

The 660-ton coffer cell is launched into Lake Washington. Crews will begin repairs in early December 2013.

Coffer cell launches into Lake Washington

More coffer cell photos are on Flickr.

Nov. 22, 2013 - Coffer cell arrives on Lake Washington 

A 660-ton coffer cell arrived on Lake Washington today. The large steel structure stands 35 feet tall and measures 45 feet wide by 144 feet long.

It will be used by contractor crews to create a dry work environment for repairs to be completed on the final two Cycle 1 SR 520 bridge pontoons.

When attached to the ends of pontoons U and V, the coffer cell will serve as a portable drydock. Once in place, crews will pump water out of the coffer cell so they have a dry work environment to complete epoxy injections, crystalline waterproofing, transverse post-tensioning and application of carbon-fiber wrap.

Take a look at how it works (click to open as a PDF):

Schematic of coffer cell operations on Lake Washington

Oct. 5, 2013 - Third cycle of pontoons leave the Aberdeen casting basin

Pontoon O leaves the Aberdeen casting basin on Oct. 5, 2013

On Oct. 5, six more pontoons left the Aberdeen casting basin. This was the third of six cycles of bridge pontoons to be construction in Aberdeen.

Take a look at photos on Flickr or watch video of the process on YouTube.

Sept. 11, 2013 - Pontoon W leaves drydock, heads to Duwamish for column repairs

SR 520 pontoon W leaves the Harbor Island drydock

Repairs to Pontoon W have been completed at a drydock location on Harbor Island, ensuring that cracks are sealed, the pontoon is watertight and the new State Route 520 bridge will meet its 75-year design life.

This is the second of two pontoons repaired in drydock, while two remaining pontoons from Cycle 1 will be repaired on Lake Washington. The pontoon was floated out of the drydock on Tuesday afternoon Sept. 10. 

SR 520 Floating Bridge and Landings Project Deputy Construction Manager Greg Meadows shares an overview of repair procedures made to Pontoon W

Construction Manager Greg Meadows gives an overview of pontoon repairs on YouTube

Before returning to Lake Washington, however, contractor Kiewit/General/Mason, a Joint Venture (KGM) towed the pontoon to the Manson Construction Company facility on the Duwamish River to remove six round concrete columns built on the pontoon last fall. A total of 10 round columns and two box columns were built atop Pontoon W to support the future highway. 

In December 2012, KGM determined one column needed to be replaced because the rebar cage inside the pontoon shifted slightly during the concrete pour. Since the first column was replaced, additional tests have shown that six other columns have the same construction issue. The remaining three columns have been approved through the quality assurance process and meet all contract requirements.

Since the contractor is responsible for the column repair and all associated costs, WSDOT gave KGM an opportunity to evaluate and propose potential repairs. KGM has determined that the best way to ensure that the columns meet all contract and quality requirements is to remove and replace these six columns.

Aug. 23, 2013 - Updated weekly reports, correspondence between WSDOT Secretary and 520 project director posted

WSDOT recently provided "weekly reports" from February to August 2013 in a public records request. We wanted you to have these materials as well, so they are posted below.

What are weekly reports?

Weekly reports are construction management tools used by project managers to communicate the progress and performance of their projects. They convey cost, schedule, quality and risk performance trends. The reports contain potential cost and schedule data that is not yet finalized with project contractors and may be adjusted significantly during negotiations. It is important to note that not all of the potential change orders in the reports will ever become a change order and the final costs of those items have not yet been negotiated.

SR 520 weekly reports:

Additional context about these reports is provided in two memos between SR 520 Program Director Julie Meredith and Washington Transportation Secretary Lynn Peterson:

July 30, 2013 - Cost and schedule updates for SR 520 floating bridge and pontoons


Reporters listen to Secretary Peterson's announcement during a press conference at the drydock in Seattle, WA.

WSDOT Transportation Secretary Lynn Peterson announced that WSDOT and its contractors have reached agreement on the cost of repairing four pontoons from the first construction cycle and modifying another four pontoons from the second cycle for the new SR 520 floating bridge. 32 of the 77 pontoons needed for the new floating bridge are now complete.

WSDOT hosted a briefing to share these findings with local media. You can view all of the materials, which are posted below:

At the briefing, WSDOT also shared an updated schedule. The new floating bridge is now estimated to open to traffic in late 2015 or early 2016. Previously, the contract required the floating bridge to open to traffic by July 2015. A final date will be determined as part of the schedule negotiated with contractors.

July 16, 2013 - Pontoon W to Harbor Island

Pontoon W en route to Harbor Island

Pontoon W -- one of four SR 520 bridge pontoons requiring repairs -- frames an interesting view of the Space Needle as it travels to Harbor Island.

More photos of Pontoon W and other repair work are in our Flickr set.

June 24, 2013 - Cycle 3 pontoons underway

Cycle 3 pontoon construction underway

Cycle 3 pontoon construction is underway in Aberdeen, WA. Check out more photos on Flickr.

June 7, 2013 - Pontoon movements, repairs in June and July



Crews are launching the summer construction season with pontoon movements on Lake Washington. One pontoon arrived to Lake Washington via the Ballard Locks on Friday, June 7, while four pontoons from Cycle 1 are being prepared for repairs. Track all pontoon movements.

Read our news release for more information and check out the graphic that explains the repair plan (pdf 598 kb).

April 29, 2013 - Second cycle of pontoons float from Aberdeen casting basin

SR 520 pontoon "S" leaves the casting basinon April 28, 2013 

Six new SR 520 bridge pontoons floated out of the Aberdeen casting basin during a blustery rainstorm overnight April 28-29.

This is the second cycle of pontoons built in Aberdeen and includes three 360-foot-long longitudinal pontoons, one cross pontoons, and two smaller supplemental pontoons that provide stability and flotation for the new SR 520 floating bridge.

View photos on Flickr and a time-lapse video on YouTube.


March 15, 2013 - Crews place final anchors for new SR 520 floating bridge on Lake Washington

Crews reached a major milestone today as they set the 58th of 58 total anchors for the new floating bridge.


A fluke anchor lowered into Lake Washington. Photo taken March 12, 2013

Check out these graphics to learn more about the different anchor types, what they look like, and how they were installed on Lake Washington.

Read more about the milestone on the WSDOT blog, or check out some great photos on Flickr.


Feb. 26, 2013 - WSDOT announces SR 520 pontoon design changes and repairs, results of internal review

Washington Transportation Secretary Paula Hammond announced that WSDOT is making repairs and design modifications to the SR 520 pontoons to ensure a 75-year life of the floating bridge. These changes are the result of findings by an expert review panel. Read our news release for additional information.

WSDOT hosted a briefing to share these findings with local media. You can view all of the materials, posted below:

Watch the entire press conference on YouTube

Watch the Feb. 26, 2013 SR 520 Press Conference

Feb. 21, 2013 - Unredacted weekly reports and additional correspondence with KOMO posted

On Feb. 7, a King County Superior Court judge ruled in favor of Fisher Broadcasting Seattle/KOMO 4, which filed a complaint against WSDOT regarding a public disclosure request. WSDOT, in consultation with the Attorney General’s Office, previously redacted information from some documents submitted to KOMO in response to a public disclosure request.

In response to the court’s decision, today WSDOT provided unredacted versions of files to KOMO 4. These files are internal management documents used to track project progress and proactively manage potential risk items, and are posted below:

We are posted the files online today because the court determined these documents should be made public, even though WSDOT has not yet completed cost negotiations with our pontoon construction contractor.

Please note that:

  • The costs of potential risks identified in these reports reflect only rough estimates.
  • Reported risks may or may not be realized and may or may not result in actual additional costs to the SR 520 Program.
  • If reported risks are realized, they will be resolved through negotiations with the project contractor and modifications to the design-build contracts, or a dispute adjudication process.

At this time, the SR 520 program includes a $200 million risk reserve and contingency fund that is available to address issues like these. Given that we are currently in negotiations with the pontoon contractor about costs and responsibilities, and there may be opportunities for schedule recovery, among other factors, WSDOT does not yet know what costs may be incurred due to pontoon design and construction issues.

In addition, we are also posted recent correspondence with KOMO (pdf 1.2 mb) about Pontoon Construction Project contract details regarding federal Buy America provisions, contractor insurance requirements and concrete mix information.

Feb. 7, 2013 - King County Superior Court judge rules in favor of KOMO TV

A King County Superior Court judge ruled in favor of Fisher Broadcasting Seattle/KOMO 4, which filed a complaint regarding redacted information included in a WSDOT response to a KOMO public disclosure request.

Read WSDOT's legal brief, declarations and sample redacted document (pdf 8.3 mb)

Read KOMO's court documents (pdf 8.8 mb)

Read WSDOT's statement to members of the Washington State Legislature and Washington Transportation Commission (pdf 16 kb).

Read the court order (pdf 554 kb).

WSDOT is committed to transparency and keeping the public informed about the SR 520 Program. WSDOT redacted parts of 90 documents out of the more than 16,000 documents that we have released to media outlets. The information was redacted because it will serve as the foundation of WSDOT’s position in upcoming negotiations with the contractor regarding first cycle of pontoons built in Aberdeen. We are committed to serving as responsible stewards of public dollars and we hope to minimize the impact this ruling will have on our upcoming negotiations.

The Attorney General’s Office is working with WSDOT to determine whether an appeal will be filed. The judge held the production of records for two weeks while an appeal decision is made.


Jan. 31, 2013 - Read our latest message to the Washington State Legislature and KOMO TV

WSDOT recently received several questions from KOMO TV and conducted a site tour at the Aberdeen casting facility. We want you to have all of the information we've shared with KOMO, so we posted our latest response (pdf 52 kb).

We've also posted our email to members of the Washington State Legislature (pdf 1.13 mb) alerting them to this latest round of correspondence.

Finally, we've posted an overview of the SR 520 budget (pdf 328 kb), including a detailed explanation of SR 520 program funding sources and their uses.

New photos on Flickr: continued progress in Aberdeen



WSDOT crews continue to make progress on the second cycle of pontoons under way in Aberdeen.

Check out our Flickr album to see the latest photos both inside and outside of the latest pontoons.

Jan. 28, 2013 - Second Tacoma pontoon float-out under way





On Jan. 28, 2013, crews began activites to prepare the second float-out of supplemental pontoons built in the Tacoma casting basin.

U.S. Rep. Derek Kilmer joined Paula Hammond and other regional leaders to celebrate the continued construction and the positive effect SR 520 work has on Tacoma, Pierce County and Washington state.

Floating out all six pontoons from this cycle will take multiple days. Check out our Pontoon Tracking page for the latest float-out details and how you can pontoon towing progress to Seattle in real-time.

View more photos on our Flickr gallery or read more about the Monday event.


Dec. 21, 2012 - Experts confirm rebar provides pontoon structural capacity
Expert Review Panel adds new members with additional expertise

An analysis using computer modeling, onsite inspections and engineering calculations has determined that rebar in the corner joints in three completed pontoons for the SR 520 bridge provides the required structural capacity. WSDOT also announced the addition of two new members to the Expert Review Panel. More...

Dec. 14, 2012 - Continued progress on SR 520 east approach bridge piers
Quality assurance update: One column to be replaced at contractor direction

Upcoming work on piers and columns for the new State Route 520 bridge will involve excavation in the lakebed inside a protective steel curtain known as a cofferdam. Crews are also removing and replacing one of 10 concrete columns atop a pontoon where the concrete pour failed to meet quality specifications. More...


Dec. 4, 2012 - View photos of underwater diver inspections

An SR 520 underwater diver



As the new SR 520 floating bridge takes shape, crews continue thorough inspections of the concrete pontoons that will serve as the floating foundation. View recent underwater inspection photos on our Flickr set.

Nov. 19, 2012 - Pontoon RFP quality requirements, additional correspondence between WSDOT and KOMO posted

WSDOT recently received questions from KOMO regarding quality assurance and other topics.

View our response to KOMO (pdf 305 kb), which included the pontoon project RFP quality control requirements (pdf 2 mb).

Nov. 15, 2012 - Pontoon Quality Management Plan, additional correspondence between WSDOT and KOMO posted

WSDOT recently received questions from KOMO that cited an anonymous source regarding the quality control process. Questions were raised about such things as rebar being placed without proper clearances, concrete pours done in rain, and other topics.

View our response to KOMO (pdf 47 kb), which included the Quality Management Plan (pdf 10 mb) developed by pontoon contractor Kiewit-General.

Nov. 14, 2012 - Superstructure milestone; media invited to tour pontoons on Lake Washington

We recently completed the first concrete superstructure on top of Pontoon W at the east end of Lake Washington to support the new SR 520 floating bridge deck.

Five columns under construction on Pontoon W

The five columns are approximately 55 feet tall and 4 feet in diameter.

We also invited media to tour the exterior of Pontoon W and the interior of Pontoon V.

Media guest on the existing 520 bridge

More photos are on Flickr.


Nov. 5, 2012 - Project overview video

Click to watch a presentation on the floating bridge and pontoon projects on YouTube

Streaming video link (WMV)


WSDOT and KOMO email correspondence

KOMO-TV recently interviewed Secretary of Transportation Paula Hammond, which you can see below. In addition, we've also provided several detailed responses to questions received from KOMO.

We've posted their questions and our answers so you can have all of the information we've shared with KOMO.

Link: WSDOT and KOMO email exchange (pdf 510 kb)

Pontoon inspection videos

We want you to be able to see all of our inspection videos of the new SR 520 bridge pontoons. This summer, our pontoon inspection crews recorded and cataloged over 45 hours of pontoon inspection footage so we could track issues that needed repairs.

We've posted their footage -- completely unedited -- for you to view. A word of warning: many are huge files (some over 1 GB large!), so they may take a while to download.

Link: Pontoon inspection videos page

Paula Hammond and KOMO TV - the full 25-minute interview

Watch the full interview between Secretary Hammond and KOMO-TV on YouTube

Streaming video link (WMV)

Sept. 26, 2012

Major work has been completed for the SR 520 Pontoon Construction Project. Crews built a massive pontoon construction facility in Aberdeen, and constructed, inspected, repaired and floated out the first six pontoons for the new SR 520 floating bridge.

WSDOT is proud of the pontoon construction work completed to date. These are the largest pontoons the agency has ever built and we have complete confidence they will meet the 75-year design life called for in the Pontoon Construction Project design-build contract.

We've developed the below timeline to help clarify how pontoons built in Aberdeen have been constructed, inspected, repaired, and towed to Lake Washington.

  Pontoon construction, inspection and repairs timeline

September 2012

Construction continues on cycle 2 pontoons. View a video update about this work from WSDOT project managers, as well as photos from the Aberdeen construction site on our Flickr page.

Crews are implementing recommendations from the pontoon peer review panel

August 2012

On Aug. 22, inspections found ballast water leaking between two cells in Pontoon V. This leak was repaired almost immediately.

View a PDF graphic (pdf 660 kb) for more information.

Inspections also found moisture on the inside of an end wall in Pontoon W. WSDOT and the contractor are continuing to look into the cause of this moisture, and are developing repair plans as necessary to meet contract requirements.

A YouTube video from inside the pontoon shows these issues in full detail.

On Aug. 17, the pontoon expert review panel submitted its report to WSDOT. The report includes a review of repairs made on cycle 1 pontoons and findings that address the causes of, and recommendations to correct, two key issues: pontoon spalling and cracking. You can read the panel's report (pdf 74 kb) and WSDOT's response (pdf 72 kb).

The panel indentified three key factors of spalling and cracking:
1. The placement and location of post-tensioning ducts contributed to concrete spalling.
2. Resistance to post-tensioning from interior precast walls caused end walls to crack.
3. Finally, all quality assurance practices need to be fully implemented to monitor a variety of concrete properties, including: concrete shrinkage, curing and thermal controls, and water/cement ratios, as well as length of wall pours.

July 2012

All repairs complete and endorsed by the pontoon peer review panel.

On July 30, all six Cycle 1 pontoons were floated out of the casting basin.

Watch our time-lapse YouTube video.

June 2012

WSDOT convened a panel of experts to review WSDOT's repairs, analyze the cause of pontoon cracking, and make recommendations for future pontoon construction cycles.

Watch WSDOT engineer Mike Cotten explain WSDOT's pontoon inspection and repair process



May 2012

Crews found cracking and spalling after completing post-tensioning on a longitudinal pontoon. At that time we began repairs on the affected pontoon and pre-emptive modifications on the other longitudinal pontoons.

View a PDF graphic (809 kb) with more information.

September 2011-May 2012

Major construction under way on the first cycle of SR 520 bridge pontoons.

Cycle 1 included six total pontoons:

 - Three longitudinal pontoons (360 ft. x 75 ft. x 29 ft.)
 - One cross pontoon (270 ft. x 75 ft. x 33 ft.)
 - Two supplemental stability pontoons (98 ft. x 60 ft. x 28 ft.) 
 


Aug. 28, 2012 - Pontoon Peer Review Panel Update

In May 2012, cracked concrete and spalling were discovered in one of the Aberdeen pontoons. In response, WSDOT convened a panel of experts to investigate the first cycle of Aberdeen pontoons. The panel has completed its work and WSDOT has reviewed its recommendations. 

Aug. 27, 2012 - Pontoon Inspection Update

As pontoons arrive on Lake Washington, we continue to inspect them prior to assembly of the new floating bridge so they will support the new SR 520 floating bridge for 75 years or longer. This video inside a pontoon on Lake Washington for the new SR 520 floating bridge shows an internal leak that has since been repaired. The video may be used by some to say the pontoons are leaking. We want you to have the full story.

This leak is not water from Lake Washington. Instead, it involves water that we added to the inside of the pontoons as temporary ballast to lower them to the height of the new bridge. In this one location shown in the video, there was a small hole between separate, water tight compartments inside the pontoon. The hole was repaired as part of the inspection process.

Inspectors also noted condensation on the walls of the pontoons where repairs were made in Aberdeen. We are continuing to work with the contractor to make the necessary and minor repairs on the pontoons to meet our high safety standards. WSDOT is continuing its due diligence to ensure that the pontoons meet the specifications of the contract. WSDOT is committed to building a new SR 520 floating bridge that is safe for drivers.

Previous construction updates:


Have additional questions? Let us know

Email: SR520Bridge@wsdot.wa.gov
Phone: 206-770-3500