October 26 2009
- Governor and Mayor sign agreement on the proposed bored tunnel.
- WSDOT requests bids to replace the southern mile of the Alaskan Way Viaduct.
- New video simulates the effect of an earthquake on the viaduct.
- WSDOT begins development of an automated emergency closure system for the viaduct.
Governor and Mayor sign agreement on the proposed bored tunnel
Gov. Chris Gregoire and Seattle Mayor Greg Nickels signed a memorandum of agreement (pdf 26 kb) on Saturday, Oct. 24 that outlines the city and state’s construction and funding responsibilities to replace the Alaskan Way Viaduct with the proposed bored tunnel. The Seattle City Council unanimously approved an ordinance on Oct. 19 that endorsed the proposed tunnel and authorized the execution of the agreement.
The agreement establishes a formal partnership between the City of Seattle and Washington state for removing the viaduct along the waterfront, between S. King Street and the Battery Street Tunnel. The state will fund the replacement of SR 99 along the waterfront, removal of the remaining viaduct, and construction of a new waterfront boulevard. The city will improve city streets such as Mercer Street, replace the central waterfront seawall, relocate utilities, and build new public spaces along the waterfront.
The Federal Highway Administration, state and city are leading the environmental review for the viaduct replacement along the waterfront. A second Supplemental Draft Environmental Impact Statement, which analyzes the bored tunnel and builds upon the previous review of other alternatives, will be published for public review in early 2010.
Photos of the Governor and Mayor signing the memorandum of agreement can be found on WSDOT’s Flickr site.
For more information about the proposed bored tunnel, visit our Web site.
WSDOT requests bids to replace the southern mile of the Alaskan Way Viaduct
On Oct. 26 WSDOT is issuing a request for bids for its S. Holgate to S. King Street Stage 2 contract, which will replace the southern mile of the Alaskan Way Viaduct near the sports stadiums. While crews have already begun preliminary construction for this project, such as relocating electrical lines and other utilities, we will begin road and bridge construction on this section of SR 99 in spring 2010.
As part of this project, the viaduct between S. Holgate and S. King streets will be replaced with a side-by-side roadway that is elevated over the railroad tracks. The new structure will have wider lanes and shoulders, meet current seismic standards, and improve access to the Port of Seattle’s facilities. It is designed to fit with any viaduct replacement along the waterfront. When the new roadway is open in 2013, it will temporarily connect to the existing viaduct north of S. King Street, until the replacement for that section is complete.
During south end construction, at least two lanes of SR 99 will remain open in each direction at most times, with the exception of occasional night and weekend closures. More information about this project is available on our Web site.
New video simulates the effect of an earthquake on the viaduct
WSDOT released a video that simulates what would happen to the Alaskan Way Viaduct and Seawall if another seismic event more intense than the 2001 Nisqually earthquake were to shake the Puget Sound region. This earthquake has a one in 10 chance of occurring in the next 10 years. We are releasing this video now in response to a public disclosure request.
The simulation is based on a 2007 viaduct vulnerability report that analyzed new geotechnical data and new information on local and regional seismic behavior. The report concluded that there is a higher chance than previously thought of an earthquake occurring that could cause portions of the viaduct and adjacent seawall to collapse. The Seismic Vulnerability Analysis Report is available on our Web site.
While the need to replace the viaduct remains, state and city crews work to ensure the structure is safe for drivers. Inspections like the one conducted last weekend are performed twice a year, with visual inspections done quarterly to measure any substantial cracks or settlement. Repairs to expansion joints and damaged bridge rails are made as quickly as possible, and weight restrictions are in place to reduce wear and tear on the structure.
WSDOT begins development of an automated emergency closure system for the viaduct
The viaduct program team is developing an automated closure system for the Alaskan Way Viaduct that will allow the state and city to act quickly if an earthquake, fire or other event compromises the structure. The current closure process is manual and utilizes the police force and others to close the viaduct in emergencies.
The new system will use the latest in monitoring technology, including GPS antennas and wireless equipment, to detect structure and ground movement. New signs and gates at the viaduct’s ramps and entrances will detour traffic away from the structure during an emergency, and advance warning signs will notify drivers in SODO, West Seattle, downtown and north of Seattle about any closures.
This project, which was made possible by federal funds, will allow police to address other areas in times of emergencies. The automated closure system is expected to be operational in mid- to late-2010. Visit our Web site for more information.
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