This weekend’s southbound viaduct closure previews the big traffic challenge still to come

Posted on Jun 21 2018 9:02 AM

First, a short closure and a small shift

This weekend, contractor crews working for WSDOT will close southbound State Route 99 in order to pour a new concrete roadway near Seattle’s stadiums. Crews will close southbound SR 99 between the south end of the Battery Street Tunnel and the West Seattle Bridge from 9 p.m. Friday, June 22 through 6 a.m. Sunday, June 24.

When the highway reopens, drivers will move to a new, short stretch of highway just south of the viaduct. Getting this roadway in place is important work that must occur before the SR 99 tunnel can open to drivers. 

Below: the yellow outline is southbound SR 99 today. The green outline is southbound SR 99 after the traffic shift. The spur on the right side is the South Atlantic Street off-ramp, which will start earlier and lengthen slightly.

Southbound SR 99 today through SoDo Seattle

Southbound SR 99 after closure shifts traffic to new lanes

Beyond the weekend work – a much bigger closure

This weekend work is a small preview of what it will take to realign SR 99 into the new tunnel to get the tunnel ready to open.

Ramps and a permanent SR 99 must be built over the current SR 99 roadway. This means WSDOT must close SR 99 through Seattle to complete the work that opens the tunnel to traffic. We estimate it will take three weeks of construction – which means three weeks with no Alaskan Way Viaduct and no tunnel. This blog post explains more.

We don’t have a date yet for the three-week closure as a date depends on the timing of tunnel work. Currently the tunnel contractor is testing operational and safety systems to make sure the tunnel can operate safely. At this point in time, we estimate the tunnel could open later this fall. We will give drivers about a month’s notice before we close the viaduct forever and begin the three weeks of critical ramp and realignment construction.

Three weeks of viaduct closure, plus additional time for ramp closures

In addition to the three solid weeks of no viaduct/no tunnel, the southbound SR 99 off-ramp to South Atlantic Street will close one week early. This ramp provides access to I-5, I-90, SODO and the stadiums.  

After the tunnel opens, the new northbound off-ramp into downtown could take up to two additional weeks to complete. Northbound drivers who don’t want to use the tunnel can continue to exit SR99 at South Spokane Street and take city streets into downtown. It will be a rough period for drivers as there could be up to six weeks of traffic impacts to Seattle.

This map sequence shows how the viaduct closure and tunnel opening will play out.

There’s time to plan

When the closure starts (again, we will give about a month’s notice), we will need everyone’s help to keep traffic moving. From past closures, we know shutting down the viaduct has a  region-wide effect. So we are asking everyone to start thinking of potential alternatives now to help you later.

Using available tools and having a game plan will be vital during the closure. We will have much more information about alternative ways (PDF) to keep people and goods moving as the closure approaches.

It’s an exciting time here at WSDOT as we approach our end goal of replacing the aging and seismically unsafe Alaskan Way Viaduct with a much safer tunnel. Keep following our program website and program Twitter account for more information as we move closer to opening the tunnel and tearing down the viaduct.

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