Breakthrough at Niagara Tunnel

The 14.4m diameter hard rock TBM mining Canada’s Niagara Tunnel completed an initial breakthrough on March 1.

The Robbins main beam machine entered a pre-existing grout tunnel excavated using drill and blast. The TBM, for contractor Strabag, will continue boring another 300m up to the intake structure and make a final breakthrough in mid-April.

While the tunneling portion of the project is nearly complete, two years of work still remain. Approximately 30 per cent of the continuous concrete lining was completed during tunnelling. The finished 12.8 m diameter tunnel will be fully lined with both 600 mm thick continuously poured concrete and a polyolefin waterproof membrane to prevent leakage.

The project, located in Queenston, Ontario, was initiated in June 2004 by provincially owned company Ontario Power Generation. The machine was launched in summer 2006.

The newest Niagara tunnel is the third headrace under Niagara Falls, and will supply up to 500 m3/sec of water for hydroelectric generation—resulting in enough additional power to service 130,000 Canadian customers. The tunnel is expected to go into operation in 2014.