information from WSDOT

In 2001, the Nisqually earthquake shook the Seattle region and the Alaskan Way Viaduct along with it. The viaduct was repaired and strengthened, but the aging structure was still vulnerable to earthquakes and a modern replacement was needed.

Now, the Washington State Department of Transportation is on the cusp of retiring the viaduct and opening the new State Route 99 tunnel built underneath downtown Seattle. The modern tunnel’s sophisticated systems are designed to help keep vehicles moving and travelers safe – including during earthquakes.

“The viaduct was built in the 1950s and seismic design is now light years ahead of what we knew back then,” said David Sowers, deputy administrator of the Alaskan Way Viaduct Replacement Program. “Ultimately, replacing the viaduct is all about keeping people safe and this new tunnel meets the gold standard for safety.”

The viaduct’s vulnerability to earthquakes was the biggest motivation for its replacement. The new tunnel is designed to withstand a 2,500 year quake – roughly a magnitude 9 off the coast of Washington state.

In this new video, seismic and structural experts explain what keeps the SR 99 tunnel safe during earthquakes.

Its seismic design, along with cutting-edge safety features combine to make this new tunnel one of the safest and ‘smartest’ in the world.

Before the new SR 99 tunnel opens

• At 10 p.m. Friday, Jan. 11, 2019, the Alaskan Way Viaduct closes forever between South Spokane Street and the south end of the Battery Street Tunnel.
• On Sunday, Jan. 12, contractor crews working for the Washington State Department of Transportation start three weeks of intensive construction work to #realign99 into the new SR 99 tunnel. During this time, both the viaduct and the new tunnel will be closed.
• On Saturday, Jan. 12 contractor crew of three weeks of intensive construction work to #realign99 into the new SR 99 tunnel. During this time, both the viaduct and the new tunnel will be closed.
• The Battery Street Tunnel and its Western Avenue on-and-off ramps remain open until Feb.1, 2019. On Feb. 1, the Battery Street Tunnel and the Western Avenue ramps permanently close.
• The new SR 99 tunnel opens in early February. However, it will take up to two additional weeks to complete a new northbound off-ramp into downtown Seattle. Drivers should expect traffic disruptions for up to six weeks.

It’s not too late to make a plan.

From lengthy closures of the viaduct in 2011 and 2016, traffic congestion worsened considerably on highways and city streets.  This planned closure is unprecedented – three weeks long.

WSDOT and all the regional transportation agencies continue to urge everyone heading to and through Seattle to avoid driving solo and make a plan to get around differently, if possible, during this lengthy SR 99 closure.

Resources and ideas are available from WSDOT, King County and the Seattle Department of Transportation.