Seattle’s waterfront demolition show will turn twice as spectacular and twice as noisy this week, as crews sic their munching jaws on the double-deck mainline of the Alaskan Way Viaduct.
Contractors finished breaking down the one-lane Columbia Street onramp last week, clearing a path to start chomping all six highway lanes Wednesday. Work will proceed north from Columbia Street past the state ferry terminal toward Pike Place Market, the biggest phase of a five-month project.
This part of the demolition combines long-necked machines on the ground with shorter chompers and rams parked on the viaduct. Subcontractor FERMA Demolition will punch through the decks in what’s called a “stitch break,” so that from above the roadway looks honeycombed.
That’s followed by chewing and cutting of the cross beams before the pieces are hauled away.
Rubble will be dumped in the defunct Battery Street Tunnel, where workers have torn down viaduct spans in the way. Another single-deck roadway segment has been removed near the market, next to train tracks used by BNSF Railway, Sounder and Amtrak. Workers from those spots will move south, to accelerate the highway removal.
Even when work on one section is relatively quiet, such as during rubble removal, pounding and crunching will proceed on a deck below or adjacent, said Phil Wallace, senior operations manager at prime contractor Kiewit Infrastructure West.
That means a continuous racket all day long, unlike the initial four weeks while workers took down smaller structures.
Viaduct removal is part of the $3.3 billion project to replace the aging, weakened structure with a four-lane tunnel that opened last month.
Traffic was reduced to one lane in each direction last week on waterfront Alaskan Way, causing increased congestion around the Highway 99 tunnel’s new south interchange, as exiting drivers headed toward the state ferry terminal or downtown. Those lane closures will continue for several weeks to maintain a safe separation between travelers and the viaduct removal work, Wallace said.
About 20 million pounds of concrete and rebar have already been knocked down — roughly 15 percent of the total volume, he said.
“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.”
People at the north end of the viaduct stood within 50 feet of the work zone at midday Monday, to witness span removal next to the Battery Street Tunnel. Workers there have used protective netting to contain flying debris and sprayed water from the concrete cruncher’s jaws to reduce dust.
Contractors have heard few complaints, though on a couple of occasions workers started too early on weekend mornings, Wallace said. By city permit the work may reach 90 decibels, as loud as a motorcycle.
Soon crews will start erecting a temporary pedestrian bridge over Western Avenue and Alaskan Way to the state ferry terminal. A pillar from the viaduct’s Columbia Street onramp was left standing, to serve as a support column under the temporary steel detour bridge.
In July pedestrians will use that bridge, while the Marion Street bridge a block north is removed. Until then, the Marion Street viaduct span, where the existing foot bridge is attached, will remain standing for weeks after decks next to it are smashed.
Eventually, the city will build a new Marion Street pedestrian bridge, as part of its project to create a parklike experience along the waterfront.