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Alaskan Way Viaduct Demolition Progresses

Thursday, March 21, 2019

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Kiewit Infrastructure West Co. is making progress on the demolition of Seattle’s double-decked Alaskan Way Viaduct, which serves as part of a larger move for the construction of the $712 million Waterfront Seattle Program.

This final stage of the structure’s $3.3 billion replacement will see the addition of the new State Route 99 tunnel. The Waterfront Seattle Program, led by the City of Seattle's Office of the Waterfront, is geared toward making a “Waterfront for All,” Waterfront Seattle writes on its website. Work includes replacing the Elliott Bay Seawall, the SR 99 Tunnel project and Viaduct demolition and the Multimodal Terminal at Colman Dock Project.

Project History

According to the Washington State Department of Transportation, the demolition work will help transform the city’s waterfront by removing a “vulnerable structure” from local infrastructure. The project will replace the Alaskan Way Viaduct—a stretch of SR 99 in the city that is subject to risk from seismic activity—with a new route that includes a nearly 2-mile-long tunnel. The project began after the 1950s-era viaduct structure sustained damage from a 6.8-magnitude earthquake in 2001.

In April 2017, after nearly four years, "Bertha," Seattle’s giant tunnel-borer, completed its 9,270-foot journey under the city. Bertha, the world’s largest tunneling machine, was built by Japanese manufacturer Hitachi Zosen, and has been operated by Seattle Tunnel Partners, the design-build contractor overseeing the Alaskan Way Viaduct Replacement Program.

WSDOT awarded the contract to Kiewit in May 2018, though work could not begin until the SR 99 tunnel opened to drivers in early February.

In August 2018, local news station KOMO reported on what looked like giant sugar cubes—blocks of expanded polystyrene—being used as fill on construction projects in the area, including in support of the northbound SR-99 off-ramp connected to the Viaduct project.

Alaskan Way Viaduct Demolition

Demolition of the Alaskan Way Viaduct began in mid-February, with completion slated for roughly six months after. According to The Seattle Times, contractors finished demolishing the Columbia Street onramp earlier this month, which in turn has made way to allow work to start on all six highway lanes. For this phase of work, long-necked machines are deployed on the ground, along with shorter chompers and rams being used on the viaduct. The demoliton itself costs $97 million.

Subcontractor FERMA Demolition will break down the decks in a “stitch break,” which will be followed by the cutting of cross beams. Finally, the pieces are taken away. Project rubble will be relocated to the defunct Battery Street Tunnel, and though some elements of the work are quieter, such as rubble removal, there will still be noise associated with other deck work in nearby areas.

Phil Wallace, senior operations manager for Kiewit Infrastructure West, told The Times that roughly 20 million pounds of concrete and rebar have already been demolished, which amounts to around 15 percent of the total volume.

“Everything’s going pretty much as planned,” Wallace said. “So far, the reaction from neighbors and the community has been pretty good. We’re trying to be good neighbors.”

Kiewit was also contracted to decommission and seal the Battery Street Tunnel, as well as rebuild some streets and restore parts of the waterfront’s infrastructure as a temporary measure in preparation for the new waterfront project.

“Finally, the viaduct is coming down,” said Seattle Mayor Jenny A. Durkan, back in February. “The start of the demolition of the viaduct is a big step toward building a city of the future. Now, we can begin to reconnect Seattle with its heart—the Puget Sound—and move ahead on our new 'Waterfront for All,' with 20 acres of public spaces for everyone.”

Those interested can keep track of demolition progress on an interactive map, updated weekly, provided by WSDOT.


Tagged categories: Construction; Demolition; Infrastructure; NA; North America; Program/Project Management; Tunnel

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