Setting the foundation for a Seattle waterfront revival

The existing seawall had protected Seattle for more than 70 years, but time and a harsh marine environment weakened the structure.

The days of gribbles are over. And waterfront safety hazards are a thing of the past too.

As we conclude 2017, we’re proud to report that construction of one of our major capital projects is now complete: The 3,750 feet or 0.7 miles, $410.2 million—Elliott Bay Seawall.

The original wood, concrete, and steel seawall, built between 1919 and 1936, had become increasingly unstable thanks to tidal erosion and gnawing gribbles (sea crustaceans) that consumed exposed wood portions.

Gribble – in case you were wondering…eww.

The precarious wall, an essential barrier between Elliott Bay and the downtown infrastructure, was putting Viaduct commuters and Seattle’s future waterfront development in jeopardy; if the wall collapsed, the adjacent soil and infrastructure would fall into the bay, flooding the land, threatening the Viaduct and making future development nearly impossible on soupy real estate. Recognizing the alarming reality, voters passed a levy in 2012 directing the City to rebuild this critical section of the seawall.

With the new seismically enhanced and structurally sound system in place—a concrete seawall, a column foundation of soil infused with jet grout, and cantilever support beams—we haven’t merely completed a necessary safety upgrade, we’ve also put the foundation for the Seattle’s waterfront revival in place.

  

  

The $700 million plan, with a target to fully open the waterfront by 2024 as a pedestrian friendly boulevard and park with concerts, art, family attractions, shops, cafes, restaurants, and breweries was inconceivable without completing step one: refurbishing the decaying seawall.  Check! ✔️

Finished seawall replacement in front of historic Piers 55 to 57. You can now walk on the light penetrating surface (LPS) panels all the way from the Seattle Aquarium to Colman Dock.

Another result of Seawall 2.0? The state-of-the-art design aids the local ecosystem instead of undermining it. With marine life “habitat benches” built in below the semi-transparent light filtering sidewalks, we have created a seamless transition between the land and the Sound that’s friendly to aquatic life.

Light filtering sidewalks cross section.

Twenty-First Century cities must be sustainable cities. And the new Elliott Bay Seawall, serving as necessary safety infrastructure, instigating a revived waterfront, and providing eco-friendly habitat is a key component of a sustainable Seattle.

“Then” – Looking north at serious construction efforts in February 2016.

“Now” – Overlooking the same stretch of waterfront, this time in March 2017.

Highlights of the new Elliott Bay Seawall

  • Marine mattresses that provide intertidal zone habitat.
  • Structural “Z” shaped precast concrete system to carry load in support of the Light Penetrating Surface panels.
  • Jet grout soil improvement-largest volume in the Nation.
  • Extensive soil freeze wall used for construction to mitigate groundwater challenges.

Photos + videos

Check out our photos and videos to learn more about past Seawall Project work. More photos of past construction can be found on the SDOT Flickr account.

Contact us

Major construction work on the Seawall project is now complete and all calls are now directed to the Waterfront Project hotline (206-499-8040; staffed from 8 AM to 5 PM, Monday through Friday). You can reach the Seawall Project Street Team via email at seawall@waterfrontseattle.org.