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Email viaduct@wsdot.wa.gov or call 1-888-AWV-LINE (298-5463)

Viaduct questions

  • + When will the viaduct be demolished?

    In 2011, crews demolished the southern mile of the viaduct, which accounted for nearly half the structure. The remaining portion of the viaduct will be demolished after the SR 99 tunnel opens to traffic, and then a new Alaskan Way street will be built in its place. The new Alaskan Way, which will connect over the railroad tracks to Elliott and Western avenues and to SR 99 near the stadiums, will provide several east-west connections to downtown.


  • + Is most of the traffic using the viaduct going to downtown or through downtown?

    Before we demolished the southern mile of the viaduct in October 2011, it carried approximately 110,000 vehicles per day just south of the mid-town ramps. Of this amount, approximately 17,000 vehicles entered or exited downtown at Columbia and Seneca streets, and 33,000 exited or entered at Elliott and Western avenues toward Belltown, Uptown, and neighborhoods along the 15th Avenue and Elliott Avenue corridor. The remaining 60,000 vehicles continued north through the Battery Street Tunnel, either exiting in the South Lake Union/Queen Anne area or continuing further north.


  • + Is the viaduct still a safe structure on which to drive?

    Routine safety inspections and maintenance keep the viaduct safe for public use. In 2008, crews strengthened four column footings where the viaduct had settled approximately five-and-a-half inches into the ground since the 2001 Nisqually earthquake. The column safety project limits settlement in this area of the viaduct and prevents further damage to the structure.

    We also installed a system designed to close the viaduct automatically in the event of a moderate to severe earthquake in the greater Seattle area. The automated closure system consists of traffic gates at all viaduct access points controlled by an earthquake detection system. If the earthquake monitoring system detects significant ground movement, it will simultaneously lower all nine traffic gates and safely close the viaduct in two minutes.

    In 2011, crews demolished nearly half of the vulnerable viaduct near Seattle’s port and stadiums. Drivers now use a construction bypass connected to new side-by-side bridges built to current safety standards.


  • + What will happen to the Battery Street Tunnel?

    The Battery Street Tunnel was constructed in the 1950s and has not been upgraded since. Its electrical and mechanical systems are difficult to maintain and do not meet modern safety requirements. WSDOT conducts regular safety inspections of the tunnel. It will be closed and filled in after the SR 99 tunnel opens to traffic.


  • + Why is replacing the viaduct important to public safety?

    The 1950s-era viaduct was already showing signs of age and deterioration before the 2001 Nisqually earthquake further weakened the structure, but the earthquake heightened the need for its replacement. The major risk facing the viaduct is its seismic vulnerability. The viaduct stands on fill soil bounded by the seawall. Marine organisms have slowly eaten away parts of the seawall and weakened it. In an earthquake, the fill soil is subject to liquefaction, where a shaking motion causes the soils to turn into a quicksand-like condition. Another major earthquake could collapse the seawall and liquefy the soil, damaging the viaduct beyond repair.

    View a simulation (YouTube) of what could happen to the viaduct if a strong earthquake were to shake the Puget Sound region (or watch a non-YouTube version - requires Windows Media Player). Visit the Elliott Bay Seawall Project website for information on the plans to replace the seawall.


  • + How are you managing parking during construction?

    WSDOT and program partners meet regularly with a group of Pioneer Square and central waterfront stakeholders to identify and implement parking mitigation strategies. A plan to address short- and long-term parking concerns in these neighborhoods was completed in 2012. Example strategies include: partnerships with parking facilities to offer low-cost, short-term parking options; wayfinding signs that direct drivers to the parking supply; a responsive mobile website that provides data on parking availability and directions; and a public awareness program to let visitors and the general public know that parking is available in Pioneer Square and on the waterfront during SR 99 tunnel construction.


  • + Is viaduct replacement construction being coordinated with other nearby projects?

    WSDOT coordinates with partner agencies on nearly every aspect of the program including overall strategy and management, project schedules, construction and public involvement. Project coordination extends beyond the SR 99 viaduct replacement - coordination with the Seawall Project, the Seattle Multimodal Terminal at Colman Dock ProjectWaterfront Seattle and many other projects is vital to keeping traffic and construction moving.


SR 99 tunnel questions

  • + Where will the tunnel be located?

    The tunnel route begins on Alaskan Way South south of South King Street, then moves toward First Avenue near Yesler Way, turns north near Stewart Street and ends at Sixth Avenue North and Thomas Street.


  • + Why is the tunneling machine named Bertha?

    Naming tunneling machines is a long-running tradition within the tunneling industry. Brenda, Togo, Balto, Rainier and Elizabeth are all names of tunneling machines that are currently or have recently completed tunneling in the Puget Sound region.

    Like most ships, tunneling machines are traditionally named after females and WSDOT chose to follow in that tradition. Bertha’s name was chosen as part of a contest for kindergarten through 12th-grade students. Proposed names had to be female and have significance to Washington state heritage, life, nature, transportation or engineering. Elected mayor of Seattle in 1926, Bertha Knight Landes was the first woman to lead a major American city.


  • + Why did tunneling stop in December 2013?

    Tunneling began in summer 2013just west of the stadiums. In December 2013, Seattle Tunnel Partners stopped tunneling approximately 1,000 feet into the tunnel drive after experiencing increased temperatures in the machine. While investigating the cause of the high temperature readings, STP discovered damage to the machine’s seal system and contamination within the main bearing. STP has since completed repairs and enhancements to the machine and resumed tunneling. Their latest construction schedule is available here.


  • + How was the tunneling machine repaired?

    Seattle Tunnel Partners built a 120-foot-deep pit in front of the machine. When the pit was complete, the machine tunneled forward into it. Crews then partially disassembled the machine and made repairs and enhancements. This narrated video (links to YouTube) explains the repair process in detail. The machine mined out of the pit in January 2016.


  • + Did other work continue during the tunneling stoppage?

    Construction at the north and south ends of the SR 99 tunnel continued throughout the stoppage. Crews built ramp and roadway connections at each portal. They also continued work on the operations buildings that will control safety features, lighting and ventilation within the future tunnel. 


  • + Who will pay for the cost associated with the tunneling machine stoppage?

    In 2014, Seattle Tunnel Partners requested $125 million in additional compensation related to the stoppage. WSDOT denied that request after determining it had no contractual merit. The process for resolving disputes within the tunnel contract is prescriptive. It requires multiple steps by both parties. Should Seattle Tunnel Partners continue to pursue entitlement related to the stoppage, it will take time to resolve. Ultimately, the responsibility for costs associated with the delay will be determined through the project's design-build contract. 


  • + Will the viaduct close during construction?

    The viaduct closes for two weekends a year – generally in the spring and fall  for inspection and maintenance. The project also includes planned temporary closures due to construction activities, such as the 10-day closure that occurred in April and May 2016.

    Aside from planned closures, SR 99 will remain open during construction thanks in part to a construction bypass roadway that connects SR 99 in SODO to the viaduct along the waterfront. 


  • + Will the tunnel be safe?

    Structural engineers agree that tunnels can be one of the safest places to be during an earthquake. The SR 99 tunnel is being designed to withstand an earthquake that only happens every 2,500 years on average (in the range of a magnitude 9.0 earthquake) without collapsing.

    The tunnel will have emergency passages to safe refuge areas, and state-of-the-art ventilation, fire detection and suppression, security and lighting systems. It will be monitored 24 hours a day by WSDOT, similar to the I-90 tunnel today. Check out our tunnel safety fact sheet (pdf 1.6 Mb) for additional information.


  • + Will the tunnel work for freight?

    The SR 99 tunnel will maintain freight routes through Seattle and preserve I-5 for regional and state freight trips. It will also provide a route through the city for vehicles that would otherwise use city streets.

    Some freight trips destined for Ballard and the Interbay industrial area will likely use the new Alaskan Way street along the waterfront, with its crossing over the railroad tracks to Elliott and Western avenues. Traffic signals along the waterfront will be operated to ensure through trips move efficiently.

    Freight trips leaving Port of Seattle terminals will also have improved access to I-5 and I-90 as a result of SR 519 and Spokane Street improvements and a new overpass at South Atlantic Street, which was included in our south-end viaduct replacement project.


  • + Will there be restrictions on freight using the tunnel?

    Most freight will be able to use the SR 99 tunnel. Vehicles hauling hazardous or combustible materials will be prohibited from the tunnel, similar to current restrictions in the Battery Street Tunnel and on the viaduct during peak hours. These vehicles will take I-5 or Alaskan Way along the waterfront, as they do today.


  • + How will northwest Seattle residents get to SR 99?

    Residents from northwest Seattle will have two options to get to or through downtown Seattle. They could travel along Elliott Avenue, as they do today, and drive down a new bridge over the railroad tracks near Pike Place Market to a new Alaskan Way street along the waterfront. Alaskan Way will connect directly to SR 99 near South Royal Brougham Way.

    If northwest Seattle residents want to use the SR 99 tunnel, they could take the new two-way Mercer Street to Sixth Avenue North and enter the tunnel at Republican Street. They could also use any of the existing connections to Aurora Avenue north of Mercer Street.


  • + How many lanes will the tunnel have?

    The tunnel will have two 11-foot travel lanes with an eight-foot safety shoulder and a two-foot shoulder in each direction that will ensure enough space for all vehicles and legal size trucks.


  • + Will the tunnel have mid-town exits?

    The SR 99 tunnel will not have mid-town exits. The tunnel and a new Alaskan Way street are designed to work together to replace the functionality of the viaduct. The tunnel will have the capacity to accommodate trips through downtown, while the rest of today’s viaduct users will access downtown using ramps at either end of the tunnel. Along the waterfront, a new Alaskan Way street will provide several east-west connections to downtown, replacing the function of today’s midtown viaduct on-ramp and off-ramp.


  • + Will the SR 99 tunnel be tolled?

    In 2013, WSDOT was directed by the Washington State Legislature to raise $200 million from tolls for the SR 99 Tunnel Project. The Advisory Committee on Tolling and Traffic Management studied ways to refine tolling of the SR 99 tunnel to minimize traffic diversion and meet funding goals, and investigate strategies to reduce or mitigate diversion. The committee submitted recommendations in 2014 (pdf 1.8 Mb).

    Tolling is anticipated to start when the tunnel opens to traffic.


  • + Where will the dirt from tunneling go?

    During tunneling, Seattle Tunnel Partners will remove 850,000 cubic yards of soil. Clean tunnel spoils will be barged to CalPortland’s Mats Mats reclamation facility at Port Ludlow where they will help fill a gravel quarry.


  • + How does the tunneling machine operate?

    When operating, the SR 99 tunneling machine's rotating cutterhead scrapes away soil, carrying it back through the machine using a spiral screw conveyor. Curved concrete panels are installed behind the machine’s front end to form rings that serve as the machine’s exterior walls. Ring by ring, the machine pushes forward while the tunnel takes shape in its wake. A conveyor belt that will eventually reach 9,000 feet in length moves excavated soil from the front of the machine out of the tunnel to barges waiting at nearby Terminal 46.

    The tunneling machine uses a laser as a reference as it moves forward through the earth. Projected from a fixed point behind the machine, the laser is received by a guidance system at the front of the machine that is precisely calibrated to the tunnel’s predetermined path. The guidance system is referenced by the machine’s operator to ensure the machine remains on course. The operator steers the machine by making slight adjustments with each push forward. To learn more about how the machine operates watch the tunneling machine video (links to YouTube).


  • + Why was the tunneling machine built in Japan?

    As WSDOT's design-build contractor, Seattle Tunnel Partners was responsible for procuring the SR 99 tunneling machine. Hitachi Zosen Corp. was selected as the SR 99 tunneling machine manufacturer ahead of three other American and international firms based on overall technical requirements, support capabilities, price and schedule. Based in Osaka, Japan, Hitachi has successfully built more than 1,300 tunneling machines, a number of them for large-diameter tunnel projects such as this one.  


  • + Why doesn't WSDOT provide daily tunneling progress updates?

    WSDOT receives regular questions from the public about the rate of tunneling progress. While we were able to provide multiple updates each day during the ten-day closure of the Alaskan Way Viaduct in spring 2016, sharing updates that frequently isn’t sustainable for the duration of the project.

    WSDOT receives a significant amount of information from the contractor during the course of tunneling. Before we can share that information publicly, it needs to be verified – a process that takes time and resources. That verification process was streamlined by our 24/7 command center during the viaduct closure, but is not feasible to complete daily during normal operations.  

    We recognize that the public has a strong interest in the outcome of the tunnel project, and we are committed to sharing regular progress updates as the project moves forward. For now, you can expect twice-weekly updates on our Follow Bertha page. Look for updates on Mondays and Thursdays. 

    Along with the latest statistics, the Follow Bertha page includes a route map that shows the general location of the machine and some of the characteristics of the “zone” through which crews are currently mining. You can also follow Bertha on Twitter @BerthaDigsSR99 for regular updates.



  • + Why doesn't tunneling happen 24/7?

    Seattle Tunnel Partners is responsible for the project schedule, including staffing. They are currently tunneling on a schedule of 20 hours per day, five days per week. Maintaining this schedule requires two tunnel crews working 10 hours per shift each working day. Each crew works 50 hours per week, and then gets two full days off to rest.

    For STP to safely tunnel on a 24/7 schedule, they would need two additional crews so that the four crews could work on a rotational basis – eight hours per shift, three shifts per day, seven days per week – to give each of the four tunnel crews two days off per week. There is not enough experienced and qualified supervision, engineering and labor available for STP to increase the number of tunnel crews from two to four to enable tunneling on a 24/7 schedule.


  • + Will there be an event for the public to watch Bertha tunnel into the receiving pit?

    WSDOT is working with the tunneling contractor Seattle Tunnel Partners to identify ways to share the end of Bertha's journey. While much work remains to be done even after tunneling is complete, we recognize that many people have closely followed Bertha’s 2-mile trip beneath downtown Seattle. The end of tunneling is an important milestone in the project to replace the Alaskan Way Viaduct, and we are working on ways to commemorate the moment. We will share additional information as the milestone approaches. 
    The receiving pit where Bertha will emerge is within an active construction site, however, which means the public will not be able to enter the site in person in order to watch. We plan to have a time lapse camera available for public view and are exploring other options to let the public see this important milestone in the project to replace the Alaskan Way Viaduct.


Alaskan Way Viaduct looking north from SODO district.

Alaskan Way Viaduct looking north from SODO district. The southern mile of the viaduct was demolished in 2011.


Alaskan Way Viaduct looking south from Victor Steinbrueck Park, Pike Place Market.

Alaskan Way Viaduct looking south from Victor Steinbrueck Park, Pike Place Market.