We're always looking for ways to save taxpayer money. During the planning phase of a project, we focus on an important question: Can we deliver this work more efficiently?
The answer, as planning ramped up for demolition of the Alaskan Way Viaduct, was yes. And so we shifted gears by combining three previously separate projects into something much bigger – a super-sized effort that will demolish the viaduct, permanently close the Battery Street Tunnel and restore street connections across Aurora Avenue North, near the new SR 99 tunnel's future north portal.
|Workers carefully demolish the Alaskan Way Viaduct’s southern mile in 2011.|
While we know many of the key parameters for this work, we'll know more details next year, after the contractor that will perform the work has been selected and develops a plan. You can read about and comment on the guidelines for the demolition by visiting our online open house, which runs through Aug. 14. We're also hosting an in-person open house on Aug. 10.
|The Battery Street tunnel will be decommissioned and sealed as part of the new SR 99 tunnel project.|
Here are the basic elements of the largest remaining contract in the Alaskan Way Viaduct Replacement Program:
- Alaskan Way Viaduct Demolition
The name says it all: This is the project that will carefully bring down the remaining section of the viaduct. The viaduct was built in the 1950s to carry roughly half the number of vehicles it carries today. After the 2001 Nisqually Earthquake, we 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. Demolishing the structure could take up to nine months. Crews will perform the demolition in sections to minimize disruptions.
- Battery Street Tunnel decommissioning
We will decommission and permanently close the Battery Street Tunnel as part of this project. This is necessary because the Battery Street Tunnel was built in the 1950s and, like the viaduct, is beyond its useful life and is seismically vulnerable. Its electrical and mechanical systems are difficult to maintain and do not meet modern safety requirements. Decommissioning work includes disconnecting, removing or relocating tunnel systems, and cleaning soot and vehicle exhaust residue as needed. The tunnel will then be filled in and permanently sealed.
- North surface streets
Finally, the contractor for this project will be responsible for reconnecting the local street grid across Aurora Avenue North, near the SR 99 tunnel's north portal. Harrison Street will open across SR 99 when the tunnel opens to traffic; the other two intersections will open as work is completed under this contract. These improvements will provide greater connectivity between neighborhoods and alternative options for travelers.
|This rendering shows the streets reconnected across Aurora Avenue North.|
There are several benefits associated with packaging these three projects into one design-build contract. Combining the work reduces the risk of having three contractors sharing the same construction zone. Reducing the number of contractors also lowers administrative costs associated with managing the work. As an added bonus, by using the design-build contracting method rather than a more traditional design-bid-build contract, we enable the contractor to design the project as construction progresses, rather than having a complete design prior to construction.
The bottom line is that we expect to deliver all three projects approximately one year earlier than we could have if they were delivered as separate contracts. That means the viaduct comes down sooner, the City of Seattle can begin its long-awaited transformation of the downtown waterfront, and we save taxpayers money be getting our work done sooner.