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Workers guide Big Becky along the tunnel route using a complex computer system. They keep her progress on course to within a few centimetres (an inch or so).

• When fractured (broken) rock is encountered, Big Becky pauses in her work while workers support the surrounding rock.
  
  
• As Big Becky progresses, a massive conveyor system carries the rock debris out of the tunnel. Big Becky will dig up enough rock to fill 100,000 dump trucks. Some of this rock is being crushed to produce gravel for use on the project.
  
  
• Workers reinforce the walls of the tunnel using steel ribs, wire mesh, and rock bolts. They also spray on shotcrete, a concrete mixture. These steps seal and support the rock surface of the tunnel.
  
  
• Finally, the workers apply a waterproof membrane and a final concrete liner. In all, about 400,000 cubic metres (14 million cubic feet) of concrete will line the Niagara Tunnel.
  
  

Keeping Safety Top Priority

Big Becky works twenty hours a day, seven days a week. Every day, the TBM takes a four-hour break so that workers can complete safety checks and regular service to keep Big Becky in good working order.

Despite the round-the-clock work, progress was slow in the beginning for several reasons. First, Big Becky had to be built, workers trained, and the site prepared. Second, the initial downward angle presents the problem of groundwater inflow. After the tunnel route evens up at a depth of 140 metres (500 feet), that problem largely disappears. Third, workers have had to adapt processes to deal with fractured rock formations. Workers have developed strategies for stabilizing the tunnel, processes that ensure both worker safety and continued progress.



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



This aerial photograph shows the intake end of the tunnel, at the International Niagara Control Works upstream from Niagara Falls. Strabag has subcontracted to several Canadian firms for work at the tunnel intake and outlet. Preparations at the intake end will complete the tunnel after Big Becky finishes tunnel excavation.



At the worksite 140 metres (500 feet) underground, no one can tell if it's day or night.



Be it noon or midnight, the work goes on seven days a week, all year long. With the exception, that is, of one day. On December 4, the machinery is turned off and the workers walk into daylight to honour the feast day of Saint Barbara, the patron saint of tunnellers and miners.



Safety is always the top priority in the tunnelling process, even if it slows down progress. Here a worker reinforces the rock immediately above the area Big Becky is about to dig into. The workers drill long holes, into which they insert long poles called spiles to support unstable rock.



As Big Becky progresses through the rock, workers reinforce the walls and ceiling of the tunnel to ensure long-term stability. In this photograph, workers apply a wire mesh.