After the new State Route 99 tunnel opens to drivers, the Alaskan Way Viaduct along Seattle's waterfront will be demolished to make way for a new surface street built by the City of Seattle. This project will help transform Seattle’s waterfront while removing a vulnerable structure from our road network.
Project at a glance:
- Removes the Alaskan Way Viaduct.
- Closes and fills the Battery Street Tunnel.
- Rebuilds Aurora Avenue North between Harrison Street and Denny Way, and reconnects Thomas and John cross-streets.
- Begins shortly after the SR 99 tunnel opens to drivers.
- More information coming this spring and summer.
On May 16, WSDOT announced Kiewit Infrastructure West Co. as the apparent-best-value contractor, which means Kiewit submitted the best combination of technical proposal and price for completing the work. We will have more information to share in the coming weeks about the contractor’s schedule and approach to the work.
Why demolish the viaduct
The Alaskan Way Viaduct was built in the 1950s to carry roughly half the number of vehicles it carries today. After the 2001 Nisqually Earthquake, WSDOT repaired and strengthened the viaduct, but the structure is showing its age. While it remains safe for daily use and is inspected twice a year, it remains susceptible to damage or collapse in a future earthquake. The viaduct’s functionality will be replaced by a new tunnel that provides a direct route between the stadiums and Seattle Center, and a new waterfront Alaskan Way surface street being built by the City of Seattle.
The goal of demolition
WSDOT’s primary goal is to demolish the viaduct safely and with as little disruption as possible. The contractor will be required to adhere to a variety of safety standards and industry best practices in conducting the work, and WSDOT will monitor their work to ensure it is done safely.
More than just a demolition project
WSDOT is combining three projects into one in order to save overall construction time, lower costs and improve efficiency. The scope of the combined project includes:
- Removing the viaduct from South Dearborn Street to the Battery Street Tunnel.
- Removing the Columbia Street and Seneca Street ramp structures.
- Removing a majority of the viaduct’s 397 foundations and footings to five feet below ground.
- Decommissioning the Battery Street Tunnel, removing utility and mechanical systems, sealing the entrances and filling the tunnel.
- Raising Aurora Avenue North to grade between Harrison Street and Denny Way, rebuilding the street, and reconnecting Thomas and John streets across Aurora Avenue North. (Harrison Street intersection will open at the time of tunnel opening.)
- After viaduct demolition is complete, restoring waterfront roadways, sidewalks, street lighting and other elements to a temporary condition until the City of Seattle builds the new waterfront.
What will demolition look like?
Demolition is expected to take up to nine months, with the viaduct being demolished in sections. We will have more information to share in the coming weeks about the contractor’s proposal for the work, but their work plan will adhere to the requirements of the contract (PDF).
- Request for qualifications (RFQ) issued to national demolition community.
- WSDOT develops a request for proposals (RFP).
- WSDOT submits permit applications to City of Seattle.
- RFP issued to most-qualified contractors.
- Proposals from contractors due.
- Demolition contract awarded to best-value contractor.
- Execute project contract.
- Contractor develops demolition plan.
- Public outreach to share work schedule, methods, traffic control plans and other information.
- SR 99 tunnel ready for traffic.
- Viaduct closes for approximately three weeks to complete construction of ramps connecting SR 99 to the new tunnel.
- New SR 99 tunnel opens to traffic; viaduct and Battery Street Tunnel permanently closed.
- Viaduct demolition begins.
- Battery Street Tunnel decommissioning begins.
- Aurora Avenue North connections construction begin.
- Viaduct demolition complete.
- Battery Street Tunnel decommissioning complete.
- Aurora Avenue North connections complete.
*Estimated date and subject to change
WSDOT used a best-value approach and a design-build contracting method to select a contractor for the work. “Best value” means we selected the proposal that was the best value for the price, not simply the lowest price. “Design-build” is a contracting method that asks the bidding contractors to propose how they would design, schedule and conduct the work (within restrictions and limits).
This approach encourages innovative and cost-effective proposals, and allows the state to benefit from the contracting industry’s expertise and experience. This is also why we didn’t know the methods and schedule for the demolition prior to awarding the contract.
What is a design-build contract?
Under a design-build contract, the contractor is responsible for both project design and construction. By WSDOT issuing requirements for the finished product instead of outlining a particular approach for the work, the contractor gets increased flexibility and efficiency, and WSDOT gets a better product at a better value. Design-build is an alternative to the traditional design-bid-build project delivery method, in which the contractor is hired to build a design that we have fully completed.
WSDOT has used design-build successfully on several projects, including the SR 99 Tunnel Project, the SR 520 Bridge Replacement and HOV Program, Tacoma Narrows Bridge, I-5 Everett HOV, SR 519 and several I-405 projects.