Thursday, June 16, 2016

We’re saying goodbye to the old SR 520 bridge – one piece at a time

By Steve Peer

Back in April we shifted traffic onto the new SR 520 floating bridge. This bridge is so new, this drone video, taken just after we shifted traffic onto the new structure, almost looks like an animation. And while the new bridge is bigger, wider and a whole lot safer, you might wonder what’s happening with its predecessor.

Now that the new floating bridge is built, contractor crews are removing the old floating structure.

Vulnerable to wind and waves and built for a 50 year life span back in 1963, the old floating structure is being decommissioned by the same contractor that built the new bridge. Removing the bridge is part of the SR 520 Floating Bridge and Landings project contract and is expected to be complete by the end of the year.

The removal is happening in stages. Crews will:
  • Remove the barrier, railing and roadway surfaces from the old bridge (done).
  • Remove the old trusses that connected the floating bridge to the fixed structures (done).
  • Separate and float out the old pontoons.
  • Remove the fixed approaches on both ends of the old floating bridge.
  • Remove the anchor cables that kept the bridge in place.
Crews remove one of the trusses from the old SR 520 bridge.
The truss was then broken down into
smaller pieces and recycled.
Some of this work is happening on barges near the old bridge and the material is then transported off the lake. Of course, the contractor follows permit conditions and best practices to keep the materials out of Lake Washington. We’ve outlined more bridge decommissioning details in this folio.

Large scale recycling
Just like when we separate the paper and plastic to recycle at home, the old bridge is being separated and repurposed.
  • The pontoons will be floated out of the lake and reused elsewhere as piers, breakwaters and wharfs.
  • The steel from the trusses and rebar from the old structure will be melted down and reused after they are separated from the concrete.
  • The concrete will be broken up and reused for future road projects

The bottom line: We are doing our best to encourage our contractors not only to be sustainable during construction, but also be responsible and environmentally friendly during de-construction – almost always recycling. So while we say goodbye to the old bridge, we won’t necessarily bid it farewell…there’s a good chance the recycled components will reappear again – perhaps in a road or building coming soon near you.