You’ve heard it before but it bears repeating: the primary purpose of the Alaskan Way Viaduct Replacement Program is safety. The viaduct is an aging and seismically vulnerable structure, and retiring it from our highway network will make us all safer.

It’s not just addition by subtraction. We are replacing the viaduct with a modern tunnel, built with sophisticated systems that work together to keep vehicles moving and drivers safe. Learn more about how the tunnel’s systems work on our new Tunnel Safety page.

The viaduct’s vulnerability to earthquakes was the biggest motivation for its replacement, and here is another way the new tunnel shines. As it happens, tunnels are a rather safe place to be in an earthquake. If you find this counterintuitive, we’ve produced a video in conjunction with seismic and structural experts to help us explain:

Engineers in our earthquake-prone region designed the tunnel to withstand a strong earthquake – roughly one that happens every 2,500 years. This would include a magnitude 9 earthquake off the coast of Washington, where the Juan de Fuca plate of the earth’s crust forms the Cascadia Subduction Zone. The tunnel design also takes into account earthquakes that might occur along the Seattle Fault.

There are many design elements that work together to create a safe tunnel:

• Structure: The SR 99 tunnel is built with more than 1,400 strong concrete and steel rings, each 6.5 feet wide. These rings are bolted together to form the tunnel, and while very sturdy, they have some flexibility to account for ground movement. This means they can move and return to their round shape. The roads inside are also designed to be flexible, allowing them to move with earthquake waves and remain functional.
• Shape: The round tunnel can withstand lots of pressure from the outside – much like a submarine underwater keeps its round shape and withstands oceanic pressure.
• Location: Tunnels that are deep underground experience less movement from the energy waves of earthquakes. Those energy waves increase in size as they approach the surface, so a tunnel will not experience the same degree of movement as an above-ground structure like a viaduct.

The inherent advantages of a tunnel, combined with state-of-the-art seismic engineering, means the new SR 99 tunnel is designed to stand up to future earthquakes.

January 2019 marks the start of a series of dramatic changes to Seattle’s traffic landscape. The Alaskan Way Viaduct will close permanently as crews rebuild portions of State Route 99 to move it off the viaduct and realign it with the new tunnel.

When the new SR 99 tunnel opens in early February, getting to and from Seattle via SR 99 will be a very different experience for drivers than it is today.

The tunnel is a direct, 2-mile trip underneath downtown Seattle. The tunnel entrances and exits, near Seattle’s Space Needle to the north and the stadiums to the south, work differently than the entrances and exits on the viaduct.

These four new videos are designed to help you understand some of the changes ahead and how to get around when the new tunnel opens. Watch to learn:

• How to get to Seattle on SR 99 driving north
• How to get to Seattle on SR 99 driving south
• How to access northbound SR 99 from inside the city
• How to access southbound SR 99 from inside the city

The tunnel will be free to use when it first opens, with tolling starting as soon as summer 2019.

We expect it could take weeks or months for traffic patterns to settle down as drivers try different routes to get to and from their destinations.

Counting down to the viaduct closure

At 10 p.m. this Friday, Jan. 4, the SR 99 on-and-off-ramps close near the stadiums. An estimated 22,000 vehicles a day use those ramps.

At 10 p.m. Friday, Jan. 11, the Alaskan Way Viaduct closes between South Spokane Street and the south end of the Battery Street Tunnel. During this time, both the viaduct and the tunnel will be closed. This disruption is unavoidable due to the large amount of work needed to realign SR 99 into the new SR 99 tunnel.

After the new tunnel opens in early February, it will take up to two additional weeks to complete the northbound off-ramp into downtown Seattle – meaning the closure will cause up to six total weeks of traffic disruptions.

Make a plan. Now.

About 90,000 vehicles a day use the viaduct. Our roads and highways will become gridlocked if every driver decides to stay in their cars. This is why regional transportation agencies are asking everyone to make a plan to get around differently during the 3-week viaduct closure.

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

It’s been a year of progress and preparation for the Alaskan Way Viaduct Replacement Program. As we get ready for a jam-packed start to 2019, here’s a quick look at highlights of the past year.

In 2018 the SR 99 tunnel contractor, Seattle Tunnel Partners, completed the tunnel roadway and installed and tested thousands of components that together make up 90 tunnel systems. STP reached substantial completion in October and turned over control and ownership of the tunnel to WSDOT. During this time, WSDOT continued systems testing and training of tunnel operations and emergency response staff.

While STP worked on the tunnel, other contractors began their work. At both tunnel portals, the SR 99 Connections Project contractor Scarsella Brothers began working on the eight ramps connecting the tunnel to local streets. And, in May we awarded Kiewit Infrastructure West with the contract to remove the viaduct, close and seal the Battery Street Tunnel, and rebuild surface streets near the SR 99 Tunnel’s north portal. One of their first orders of work was to shift Alaskan Way out from beneath the viaduct and restore parking in October. This new alignment allows us to keep the road open while the viaduct is demolished in 2019.

Looking ahead to early 2019

This work sets the table for a very exciting start to 2019. On Jan. 4, we will close SR 99 on- and off-ramps near the stadiums, and the #Realign99 highway closure begins a week later, at 10 p.m. on Jan. 11. This approximately three-week-long closure will give crews time to complete the tunnel’s ramps and realign SR 99 off the viaduct and into the new tunnel.

A public grand opening ceremony on Feb. 2-3 will commemorate the viaduct and celebrate the opening of the new tunnel. Shortly thereafter, the new SR 99 tunnel will open, forever changing how we get to and through downtown Seattle. Shortly after that, Kiewit begins their work removing the old SR 99 route from downtown Seattle.

Two years ago, we estimated $149 million of additional program costs would be needed due to delay in completion of the tunnel project. The request for additional funds has been partially filled in previous legislative sessions. Today we presented to the Legislature’s Joint Transportation Committee and requested $43 million to complete the program, which brings the total request to $156 million. It’s important to note that none of these additional funds will be used to pay for tunneling machine repairs. WSDOT continues to follow the tunnel project’s design-build contract to recover added expenses incurred by the tunneling delay (e.g. insurance claims and litigation).

We have a few more years of construction and are on the cusp of many exciting milestones including opening the new SR 99 tunnel beneath downtown and demolition of the Alaskan Way Viaduct.

Last updated: 4:00 p.m. 1/12/19

Full SR 99 closure in place. Full sequence below:

Visit our Realign99 page for more information and resources on how to get around during the closure.