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.

By Guest Bloggers Nathan Karres and David Gitlin

If you crossed the SR 520 floating bridge this morning, you may have caught a glimpse of our contractor crews completing a major project milestone: we placed the 58th of 58 total anchors for the new SR 520 floating bridge.

It’s March madness on Lake Washington as one of the final four fluke anchors is lowered to the lakebed. Photo taken March 12, 2013

Construction crews pose for a group photo moments before submerging the last of 58 anchors for the new SR 520 floating bridge.

 When you’re crossing Lake Washington on 520 or I-90, it’s easy to forget that you’re actually floating on the lake’s surface above 200 feet of water. The new SR 520 floating bridge will be no different. In order to hold the bridge in place and help withstand winds and waves, we built and installed three kinds of anchors:

1. Forty-five fluke anchors will secure the bridge in the deepest parts of the lake by creating drag that resists pulling from bridge pontoons floating on the lake’s surface. Weighing 100 tons and with a surface area of 910 square feet (think 20 elephants packed into the floor space of a typical apartment), the immense weight, size and shape of fluke anchors ensure they stay firmly in place. Fluke anchors are covered with mounds of heavy rock to strengthen their hold. 
2. Eight gravity anchors will secure the bridge where the lake bottom is sloped with hard soils. These massive concrete boxes are filled with rocks to hold the bridge in place by shear enormity. 
3. Five shaft anchors have been drilled directly into the lake bottom where the lake is too shallow for gravity anchors. 

 Gravity and fluke anchors were built at the north end of Lake Washington in Kenmore, at a pair of specifically designed concrete casting areas. After the concrete cures and anchors are ready to go, they’re transported by barge and floated to the bridge site. This is no small feat – each anchor weighs up to 420 tons!

Crews set each anchor at a specifically mapped location in the lake, all the while carefully navigating around the numerous anchor cables for the existing floating bridge. Each anchor will eventually be attached to a new SR 520 bridge pontoon. While remaining pontoons are being constructed in Aberdeen and Tacoma, the anchors will be temporarily connected to mooring buoys bobbing atop the lake.

With one major component of the new SR 520 floating bridge complete, another has only just begun: crews in Medina are preparing to pour the first roadway section for the new bridge. Casting this roadway section is the first of thousands of feet of pavement that will be constructed for the project. 

Check back for more updates as we share our progress building the world’s longest floating bridge.

by guest blogger Joe Irwin

Snapshot of the work at the SR 520 Pontoon Construction site

What happens in Vegas may stay in Vegas, but what happens in Aberdeen goes around the world.

Working with our contractor Kiewit-General this week, we installed a webcam at the SR 520 Pontoon Construction site, providing people everywhere a peek at one of the state's mega projects.

The camera takes photos every 10 minutes at the site, 24 hours a day, seven days a week. You can watch the work happen as it happens – which will include everything from excavation of a casting basin large enough to hold an aircraft carrier to construction of floating bridge pontoons the length of football fields.

The website will store all these photos, so you can also turn back the clock to view previous work on the job – hours, months or years after it occurred. You can also use the time lapse function, which takes a photo each day, to watch months and even years of construction whiz by in just a few minutes. A photo calendar provides an additional tool, giving a way to scan the project a month at a time and key in on certain dates of interest.
Work started at the 55-acre site on Grays Harbor in February, and since then we, along with K-G, have been busy clearing, dewatering and driving 900 steel piles 135 feet into the ground to construct the foundation for the pontoon casting basin.

Excavation of the 4-acre basin starts the week of April 18, and requires crews to remove upward of 260,000 cubic yards of material. As sections of foundation piles are driven and dirt is excavated, workers will begin placing concrete for the basin.

We are on track to start constructing 33 pontoons this July that will be used to form the backbone of a new SR 520 floating bridge. The pontoons will be built in six cycles with the final cycle being completed in May 2014.

From guest blogger Jeff Switzer

Sideways rain in Grays Harbor last weekend couldn’t stop more than 200 people from cheering the start of construction on the SR 520 pontoon project in Aberdeen. Gusts from the coast that roared up Saturday only underscored the need for project everyone was celebrating: The aging SR 520 floating bridge on Lake Washington is vulnerable to windstorms and we are going to replace it.

The 33 pontoons – giant floating concrete boxes – to be built in Aberdeen starting this year will form the backbone of a replacement bridge.

Local carpenters and trades workers turned out to celebrate, saying they’re ready to start earning paychecks on the project. We’ve been working hard to get started on construction, and Grays Harbor is eager for the work. The $367 million project will ramp up to 300 direct construction jobs later this year.

Work starts this week on a casting basin – a big bathtub of a work zone on Grays Harbor. The basin will be connected to the water so new pontoons – many as long as a football field – can be built in the basin, floated out and towed to Seattle. They’ll each be three stories tall and narrow enough to fit through the Ballard Locks when complete. Some of the 33 new pontoons will weigh 11,000 tons each – as much as 23 Boeing 747s.

Take a look at our step-by-step guide to building a floating bridge to see what we have planned starting in 2012.

The same windstorm that hit the coast this weekend also sent high winds hammering the SR 520 floating bridge, giving a timely reminder why building a new bridge is so important. Since 1993, we’ve repaired about 30,000 feet of cracks in the pontoons to keep the bridge afloat and safe for traffic – but it’s time to build a stronger replacement bridge. It’s scheduled to open to traffic by the end of 2014.

Check out the Flickr photos, our YouTube video or our project page for more about the project.