After the new State Route 99 tunnel opens to traffic, 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.
Demolition is scheduled to start in early 2019 and take up to nine months to complete. WSDOT will be selecting a contractor in spring 2018, who will develop specific plans for the work. As part of this work, the Battery Street Tunnel will be decommissioned and Aurora Avenue North from Denny Street to Harrison Street rebuilt.
This page contains an overview of demolition and what we currently know about the work. The means and methods of the demolition won’t be known until after the winning contractor is selected (see "Selecting a contractor" below for more information). In August 2017 WSDOT held an in-person and online open house to share information about viaduct demolition. PDF versions of the display boards from the open house are available in our Program Library.
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 Alaskan Way Viaduct Replacement Program is building a tunnel and a new surface street that together will replace the viaduct’s role in moving people around Seattle.
The goal of demolition
WSDOT’s primary goal is to demolish the viaduct safely and with as little disruption as possible to people, property and businesses around the viaduct. WSDOT will require the selected contractor to adhere to a variety of standards and best practices to ensure the viaduct is demolished safely and efficiently.
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 demolishing the viaduct, decommissioning the Battery Street Tunnel, and reconnecting intersections along Aurora Avenue North. Within this are a number of work elements:
- 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 and restoring Aurora Avenue North between Harrison Street and Denny Way.
- After demolition is complete, restoring 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. The contractor will determine the means and methods to safely and efficiently demolish the structure, while adhering to the requirements of the contract.
By way of comparison, the demolition will more closely resemble the 2011 demolition of the viaduct’s southern mile than it will resemble the implosion of the Kingdome. The 2011 demolition involved saw cutting, munchers and hoe rams to break up the concrete and bring it down section by section.
- 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.
- Contractor develops demolition plan.
- Outreach to share demolition plan.*
- SR 99 tunnel ready for traffic.
- Viaduct closes for approximately three weeks to complete construction of ramps connecting SR 99 to the new tunnel.
- Viaduct and Battery Street Tunnel permanently closed.
- Tunnel opens to traffic.
- Viaduct demolition begins.
- Battery Street Tunnel decommissioning begins.
- Aurora Avenue North connections begin.
- Viaduct demolition complete.
- Battery Street Tunnel decommissioning complete.
- Aurora Avenue North connections complete.
*Estimated date and subject to change
WSDOT will select a contractor in spring 2018 using a best-value approach and a design-build contracting method that encourages innovative and cost-effective proposals. By giving the bidding contractors greater flexibility, it allows us to benefit from their expertise and experience. However, it also means that many details about the demolition work will not be determined until after the contractor is selected and completes their plans.
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.
What this means for the viaduct demolition
The contractor is responsible for designing and completing the work. We will not have specifics of the demolition plan until after the contract is awarded and the winning contractor completes the demolition plan.
What we know now
- The scope of work.
- The project timeline.
- Limitations on noise, dust, vibration, traffic and other effects of demolition work (see the open house display boards for more information).
What will be defined after the contractor is selected
- Work schedule and sequence (in accordance with the project timeline).
- Traffic control plans (e.g. detours).
- Demolition means and methods (within requirements of the contract).
Later this year, after the contractor has been selected, we will reach out again to share the contractor’s plans for viaduct demolition.