The Alaskan Way Viaduct, shown in July in front of Century Link Field and Safeco Field in Seattle, will be torn down over about 5 1/2 months.
Visitors to the Seattle waterfront will hear the crunch of breaking concrete this February, while demolition equipment pivots through clouds of dust and mist, flexing spiked jaws that will munch the six-story-high columns and slice through steel Rebar.
For as long as 5 1/2 months, work crews will level the Alaskan Way Viaduct, working on three to five sections at a time. Reinforced fabric shrouds will be hung from frames that contractors can move along the route to protect building walls and windows.
Kiewit Infrastructure West, prime contractor for the $75 million job, has settled on its final strategy for the work, which senior operations manager Phil Wallace outlined in an interview last week. The Washington State Department of Transportation will announce details Tuesday and hold three public briefings on the project.
Barring an Anchorage-magnitude quake, Seattle will see the 2009 wish of Gov. Chris Gregoire fulfilled: “We want to take the viaduct down, before Mother Nature beats us to the punch.”
This may provide the city’s greatest demolition spectacle since 2000, when pyrotechnicians imploded the Kingdome in only 17 seconds. More recently, in 2011 the state removed the southern mile of the viaduct over Sodo in nine days, but the governor missed her self-imposed 2012 deadline to remove the 1.4 miles downtown.
The 65-year-old Viaduct will be replaced by a new four-lane Highway 99 tunnel, along with Sodo and South Lake Union interchanges, scheduled to open the week of Feb. 4. The program costs at least $3.3 billion, funded mostly by gas taxes.
Demolition equipment will clutter the waterfront until mid-year, and merchants like Ivar’s President Bob Donegan have worried about summer access. “The waterfront is open for business during demolition,” promises Brian Nielsen, the state’s Highway 99 administrator.
“What you’re going to see is the waterfront opening up, and by June you’re going to see a pretty wide open waterfront, without the viaduct there,” said Laura Newborn, spokeswoman for the state
Crews will work in sections of two to three blocks at a time. They will generally start by punching decks with jackhammers. Then the concrete beams will be demolished with a crab-claw-shaped tool.
Water will be sprayed on the dust to knock it down, and silty wastewater is to be processed onsite, Newborn said. That treatment would be similar to how Seattle Tunnel Partners pumped water into settling tanks, the size of shipping containers, to capture grit before releasing wastewater into the county sewer system.
Kiewit’s demolition subcontractor, FERMA Corp., will begin work over train tracks near Pike Place Market, removing concrete during limited hours to avoid freight and passenger trains using the Great Northern Tunnel.
“That is first-order work for us, so we can get out of the area as soon as possible,” Wallace said.
Soon afterward, the entire north end of the viaduct will be removed, Wallace said, so the city can start building the signature Overlook Walk from the Market to Seattle Aquarium. FERMA will bring excavator machines with arms tall enough to reach upper decks, said Wallace. Therefore, the team won’t need to keep old viaduct ramps in place, as previously reported, so the machines can be driven onto the viaduct decks.
The Columbia Street onramp will be demolished immediately, so the city can complete paving its future two-way bus corridor below, and embark on a new bridge promenade to Colman Dock. A temporary steel bridge will be installed nearby, to maintain walk-on ferry access from First Avenue.
Heavy demolition will be allowed seven days a week from 7 a.m. to 10 p.m., under city noise permits, though truck trips and equipment staging may continue overnight. The loudest jackhammering of up 90 decibels will wrap up at 8 p.m. weekdays and 5 p.m. weekends, according to WSDOT.
Once the viaduct is gone, the $35 million decommissioning of the Battery Street Tunnel will continue into 2020, along with $17.5 million worth of new street connections across lower Aurora Avenue North until 2021, all within the $94 million Kiewit contract. Newborn said contractors will be paid a few million dollars extra, still under negotiation, because of WSDOT’s decision to delay the opening of the new four-lane Highway 99 tunnel until February, which in turn delayed the initial Jan. 2 date to begin viaduct demolition.
