Ontario Power Generation

The most impressive photographs of Big Becky were taken just after she was assembled onsite at the outlet end of the tunnel.



Only Big Becky's 14.44 metre cutterhead had disappeared into the rock in this photo taken in September 2006.



Looking down the tunnel towards Big Becky.

At the intake area, a 300 metre long grout tunnel was excavated below the Niagara River to precondition and seal the ground in preparation for the TBM breakthrough. Here a drill makes holes for the explosives.



In this photo the back of the TBM is about to go underground. The conveyor belt to remove the excavated rock can be seen in the lower left corner.



The TBM back-up trailers move along the tunnel on removable rails.



A bus transporting workers to the TBM drives inside the tunnel. The tunnel conveyor booster station pictured on the right-hand side was installed in November 2008. The tunnel ventilation duct (yellow tube) can also be seen in the tunnel crown.

A large, moveable ramp brings the construction workers within working distance of the tunnel ceiling.



Two robots mounted on these rings spray about 100 millimetres of shotcrete onto the rock to complete the initial tunnel lining.



Construction equipment under the shotcrete robots during assembly of the TBM in the outlet canal.



Overbreak in the Queenston shale, of over four metres at this location, slowed the TBM’s progress and prompted the decision to change the tunnel alignment.