Heavy lifting with some very big cranes
Since SR 99 tunnel construction started, big cranes have become a familiar sight on the west side of the Alaskan Way Viaduct. Recently, two new cranes have risen up, and they are like redwoods in a forest of pine trees. The “little” crane can lift up to 300 metric tons and stands 180 feet high. Its big brother can lift up to 600 metric tons and tops out at 236 feet high. That’s more than four times the height of the viaduct, or about the same height as the clock tower at King Street Station, which is located a few blocks east of the tunnel’s future south portal.
New red cranes rise above the viaduct. King Street Station in Seattle.
Why the long cranes?
These tall crawler cranes will have one basic task – building the giant gantry crane that will hoist the 2,200-ton front-end of the SR 99 tunneling machine to the surface for repairs and enhancements. As the construction folks say, this is a “big pick.” How big? Well, to give you some perspective, 2,200 tons is the combined weight of four fully loaded Boeing 747-8’s … plus the Statue of Liberty.
Later this fall, the crawler cranes will start assembling the gantry crane. This crane will be similar to the one used to assemble Bertha in 2013. It will move north and south on rails to lower the front-end pieces to the ground and put them back together again. The gantry crane will be approximately 100 feet high, about twice as tall as the viaduct. It will be supported on both sides by a foundation of reinforced concrete slabs that sit atop concrete and steel piles that reach up to 130 feet underground.
The gantry crane at the launch pit in 2013. The access pit gantry crane will be installed here.
Watch the entire retrieval and repair effort unfold on our two access pit construction cameras. And be on the lookout for big cranes next time you’re in the neighborhood – they’re hard to miss.