Seattle Tunnel Partners Successfully Lower the Repaired “Big Bertha” Tunneling Machine
SEATTLE, Aug. 25, 2015—Seattle Tunnel Partners and crane crews from Mammoet have successfully lowered the 2,000-ton front end of the SR 99 tunneling machine to a platform at the bottom of the access pit.
Crews will now use the crane to fine-tune the position of the piece. When that process is complete, they will begin reconnecting the piece to the portion of the machine that remains in the ground.
The effort to return the tunneling machine’s front end to the 120-foot-deep access pit began early Monday morning. Crews started by vertically lifting the piece, which includes the machine’s cutterhead, motors and the new main bearing assembly. The crane then moved horizontally on its rails to the north. When the piece was above the pit, crews rotated it to a semi-vertical position and lowered it partway into the pit before breaking for the evening. Work resumed early Tuesday morning, with the piece reaching the bottom of the pit Tuesday afternoon.
Three pieces of the machine’s shield that remain at the surface will be lowered and reinstalled in the coming days, according to STP’s latest schedule. After the machine has been reassembled, STP and manufacturer Hitachi Zosen will conduct a series of tests will follow reassembly to ensure the machine is ready to resume mining.