Seattle celebrates construction of world’s longest floating bridge

A celebration for the completion of the new SR 520 bridge, the world’s longest floating bridge, is happening this weekend in Seattle, though it won’t be open to traffic for a few weeks.

The existing SR 520 bridge was closed to traffic from Friday, April 1 at 11 p.m. through Sunday, April 3, at 1:30 p.m. The usual detour routes were available during the closure, including the I-90 floating bridge, SR 522, and I-405.

Related: Forward thinking may prevent future headaches for 520 commuters

Traffic officials say the old 520 bridge will be closed to traffic this upcoming weekend, as westbound traffic shifts onto the new bridge.

More than a decade of planning and five years of construction went into the completion of the bridge.

A 10k run was held on Saturday morning, with a run starting at 7:30 a.m. at Husky Stadium.

Chopper 7 was overhead as more than 13,000 runners ignored the foggy, chilly start to the day to run from the University of Washington to the bridge, then back again.

But the festivities were just getting started.

KIRO 7 news anchor Monique Ming Laven led off the official opening of the bridge with the pronouncement, “Welcome to the grand-opening ceremonies for the world’s longest floating bridge.”

Alongside her were several local, state and federal dignitaries, including the state’s governor.

“We do big things,” Gov. Jay Inslee told the crowd on the bridge. “We do hard things. And we do things that work. And this bridge is a monument to that belief system.”

Foot traffic was the first to cross the new bridge.

On Saturday afternoon, event-goers were reporting lengthy travel times leaving the bridge. The event was at capacity at around 2:30 p.m. Shuttles were working to transport the large crowd.

By 3:30 p.m., inbound shuttles to the SR 520 event were done for the day. All shuttles were being used to help transport people away from the bridge.

A presentation from Guinness World Records certified the bridge as the world’s longest floating highway.

The new 520 bridge is nearly twice as wide as the old one. It will have a shoulder for drivers and will better withstand high wind events.

The new westbound lanes of the 520 bridge won’t open to traffic until April 11. April 25 is when eastbound lanes will open.

“After over a half century of use, the existing floating bridge is showing its age,” write WSDOT officials over the project’s information page. “The bridge’s pontoons have become vulnerable to windstorms and its support columns are vulnerable to earthquakes.”