After 10 years of environmental review and analysis, the Federal Highway Administration (FHWA) today signed a record of decision allowing the Washington State Department of Transportation (WSDOT) to begin final design and construction of the State Route 99 tunnel beneath downtown Seattle. The 2.72km long tunnel will be bored using a 17.5m diameter EPBM and will replace the double-deck Alaskan Way Viaduct along Seattle’s waterfront.
Following issuance of the record of decision, WSDOT directed Seattle Tunnel Partners, consisting of Dragados-USA, Tutor Perini and HNTB to begin work on the second phase of their $1.35bn design-build contract – final design and construction of the tunnel. Initial construction activities, such as utility relocation, and final design and manufacturing of the Hitachi Zosen EPBM will begin this fall. The SR 99 tunnel is projected to open in late 2015.
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The tunnel will begin on Alaskan Way South near South King Street, move away from the waterfront at Yesler Way toward First Avenue, and eventually end at Sixth Avenue North and Thomas Street. With the tunnel, WSDOT will be able to create a safer SR 99 corridor and remove the seismically vulnerable viaduct, which was damaged in the 2001 Nisqually earthquake.
“After more than a decade, we are moving forward to replace the Alaskan Way Viaduct,” Gov. Chris Gregoire said. “Now that the tunnel has approval from the Federal Highway Administration, we can kick off the next phase of its design and construction.”
Besides completing the environmental process, the decision outlines WSDOT’s mitigation measures and commitments for the project, such as monitoring buildings and utilities during tunnel boring, replacing lost parking during construction and keeping neighbors and the public informed throughout the project.
“This is a major milestone for Seattle,” said Federal Highway Administrator Victor Mendez. “SR 99 represents an investment in the city’s economic future by creating jobs and strengthening the economy.”
“After thoroughly analyzing the bored tunnel and considering more than 90 other alternatives, we know it’s the right project for the city, region and the state,” Washington Transportation Secretary Paula Hammond said. “We look forward to continuing our work with the Seattle City Council, Port of Seattle, King County and Seattle Tunnel Partners to construct the SR 99 tunnel safely and with transparency and accountability to Washington taxpayers.”
For more information on the Alaskan Way Viaduct and Seawall Replacement Program, visit: www.alaskanwayviaduct.org/.
For the TBM information see: http://tunnellingjournal.com/news/hitachi-zosen-selected-to-build-alaskan-ways-mega-epbm/ – more-3080