The following is a release from the Washington State Department of Transportation:

A huge piece of history will make its way to and through the Hiram M. Chittenden Locks this evening, July 20, as part of the decommissioning of the defunct, 53-year-old State Route 520 bridge. Pontoon E is the first of 31 old floating bridge pontoons being removed from Lake Washington.

Washington State Department of Transportation’s SR 520 Twitter account is live-tweeting the progress of the old pontoons.

Gotta love that view! pic.twitter.com/df1hL9Qlor

— SR 520 (@wsdot_520) July 20, 2016

This is a similar process, in reverse, of the route that was used to deliver the pontoons for the new bridge. Each of the old pontoons, some as long as 360 feet, will be guided by tugboats on a route through the Montlake Cut, Lake Union, and the Fremont Canal before being towed to Shilshole Bay and delivered to a third party.

As part of the contract requirements for building the new SR 520 floating bridge, contractor Kiewit/General/Manson (KGM) has been tasked with taking apart the old SR 520 floating bridge. Vulnerable to wind and waves, the old bridge is no longer in use; it’s been replaced by a bigger, stronger, safer floating highway.

The old pontoons make up about 75 percent of the aged bridge and are leaving the lake essentially intact. The old bridge’s remaining components will be dismantled onsite and hauled to concrete-recycling facilities. Most of these materials will be processed for reuse as dry aggregate for other paving projects throughout the region.

KGM has sold the pontoons to TrueNorth Operations Group, a company which has previously repurposed old pontoons for docks, artificial reefs and wharfs globally. KGM will transfer the pontoons to TrueNorth west of the locks. The pontoons’ final destination has not yet been disclosed by TrueNorth.