pontoons

Big mistakes made on the design and construction of pontoons for the new 520 floating bridge could lead to tougher reporting requirements for the Washington state Department of Transportation.

Lawmakers want more transparency and accountability when it comes to costly mistakes. Repairs to cracks in the new 520 pontoons, for example, are expected to cost tens of millions of dollars.

Bellamy Pailthorp photo / KPLU News

Big mistakes were made by the State Department of Transportation in its construction of the pontoons that will hold up the new 520 bridge across Lake Washington.

The agency says it is making repairs and design modifications to ensure the bridge will last the full 75 year lifespan promised.

Bellamy Pailthorp / KPLU News

You may have heard about some issues with the large concrete pontoons being built for the new 520 bridge across Lake Washington. Several of them sprung leaks and cracks after the cement set in Aberdeen.

But the state Department of Transportation says drivers don’t need to worry; the situation is under control.

Click the "play" icon below to see video of State Construction Engineer Jeff Carpenter describing how pontoon cracks are being patched to ensure they will last 75 years, as stipulated in the design plan:

Photo by Bellamy Pailthorp / KPLU News

Washington State is the floating bridge capital of the world. We have four of the most famous ones, including the longest: State Route 520, which is about to be replaced.

What holds them all up? Giant floats made of concrete, called pontoons. The first and largest of them are being manufactured in Grays Harbor, near Aberdeen.