Site restoration: cleaning up after the viaduct comes down

Posted on Jun 11 2019 4:19 PM

The process of removing the viaduct is more than just demolition work. Removing the viaduct is done in three stages: site preparation, demolition, and finally, site restoration. You can see where crews are on our viaduct demolition tracker, which is updated weekly.

Once a portion of the viaduct has been demolished, crews must restore the work zone to its former condition. In this case, “restoration” means re-opening streets, sidewalks, and parking that was available before the removal process began.

Two photos showing same section of waterfront, four months apart. In second photo, the viaduct is gone.
Above: Looking north on Alaskan Way between Seneca and Marion streets, before removal and after restoration.

The most easily visible part of site restoration is clearing the piles of viaduct rubble. The two main rubble materials – concrete and rebar – must be separated. Initial separation happens on site during processing, before rubble is loaded onto trucks and hauled south to Terminal 25 for additional sorting and processing. The concrete rubble is then hauled north to fill the Battery Street Tunnel.

Cleanup also entails removing the “crush pad” placed on the ground before demolition began. This bedding of rock protects not only the surface of the street, but also the utilities buried below it. Site restoration includes clearing away this bedding and cleaning the ground beneath.

Machinery sitting in the middle of a dirty intersection with no viaduct overhead

Above: Site restoration in March 2019 at the intersection of Western Avenue and Bell Street 

One of the last steps in site restoration is removing and filling the viaduct’s foundations. The viaduct’s support columns are connected to foundations buried beneath street level. Once the columns are munched away during demolition, crews hammer out the foundations, in most places to five feet below the surface. They then backfill the hole to prepare for final restoration activities. This time-lapse video captures demolition and site restoration at University Street along the waterfront (you can see a foundation dug out and filled in the foreground at the 0:39 mark).

The last step is restoring the area to its “original” condition, including paving and striping the pavement, and opening it back up to parking and pedestrians.

Restored only for a short while

The land where the viaduct once stood will not remain static for long. Once the viaduct has been completely removed, the City of Seattle will step in to begin construction of the Waterfront Seattle project. The SR 99 tunnel was designed in tandem with a rebuilt Alaskan Way surface street, and Waterfront Seattle will build that street, along with new public spaces and an extended pedestrian promenade. Visit www.waterfrontseattle.org for more information on the project to come.

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