The Toronto Port Authority has taken a significant step in the building of an 800 feet (243.8 metres) pedestrian walkway across the Western Gap to Billy Bishop Toronto City Airport by lowering ‘Chip’, one of the two tunnel boring machines being used to excavate the tunnel. The 90-tonne Canadian-made machine joins its twin, ‘Dale’, which is creating the first of seven drift tunnels that will form the walkway’s crown. ‘Chip’ was lowered into the shaft on January 10 and will begin boring the second drift tunnel.
The new walkway will be completed in spring of 2014 and flanked by a new pavilion on the mainland and an addition to the airport terminal building on the island. The walkway will cost $82.5 million to build, and total construction cost is 100 per cent financed by the private sector and ultimately paid for by a portion of the existing $20 BBTCA passenger Airport Improvement Fee (AIF). When it is completed the walkway will be the only known pedestrian tunnel in the world that connects to an airport and sits beneath a body of water.
Being dug 10 stories (100 feet/30.4 metres) down, the tunnel is below approximately 32.8 feet (10 metres) of rock and river bed, and 65.6 feet (20 metres) of water. To reduce the potential for water ingress during construction seven six-foot (1.8 metres), interlocking tunnels will be constructed to form an arched roof for the walkway. Three of these tunnels will carry city mains to Toronto Island.