(At 3:39, WSDOT’s video shows excavation on its final day, today)
Just in from WSDOT, the latest Highway 99 tunnel news: The pit being dug to lift out the tunneling machine’s damaged cutterhead has reached the desired depth, 120 feet.
… Approximately 20,000 cubic yards of material was removed from the ground over the course of excavation, which began in mid-October. With excavation complete, crews can begin construction of the concrete cradle at the bottom of the pit. The cradle will support the machine after it moves through the pit’s southern wall, which is about 20 feet thick.
STP plans to tunnel through the concrete wall. The length of time it takes Bertha to reach the pit will depend largely on her ability to mine through and digest the concrete. If she’s unable to mine through the wall, STP will create an opening from within the pit to give her an unobstructed path forward. Once inside the pit, crews will use the massive red gantry crane … to hoist the front end of the machine to the surface for repairs.
Today’s update also says, “Settlement levels near the pit remain stable.”
(WSDOT photo)
Meantime, for more info on that giant crane – which you’ve likely noticed right next to the Viaduct downtown – check out Seattle Times (WSB partner) transportation reporter Mike Lindblom‘s story from two weeks ago.
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