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Underground Downtown
Much of the downtown section of the subway was built directly underneath Yonge Street. Since the street could not possibly be closed during years of construction, the subway was built using the "cut and cover" method. First, vertical steel piles were driven into the ground every six feet on each side of the street to provide support for the sides of the tunnel excavation. Then, workers and machines began to dig downward from the street, making the "cut." When the excavation was deep enough, horizontal steel beams were rested on the steel piles.
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Planking, Yonge Street looking south to Queen Street
October 18, 1949
Photographer: Canada Pictures Limited
City of Toronto Archives
Series 381, File 8, Item 6101-2
This image shows the one-foot-square timbers laid across steel horizontal support beams to provide a temporary surface for Yonge Street during construction.
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Planking over excavation, looking south on Yonge Street to Queen Street
December 3, 1949
Photographer: Canada Pictures Limited
City of Toronto Archives
Series 381, File 20, Item 6288-3
Once the planking was in place, traffic, including streetcars, could continue as usual on Yonge Street.
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Huge timbers one foot square were then set across the beams, forming a temporary street — level surface — the "cover" — for traffic to use, while work continued below. In places where the subway ran beneath buildings, the foundations of those buildings were deepened and reinforced while workers tunnelled from one cut to another. Once the concrete walls, floor, and roof of the subway had been poured, the piles were cut off, the remaining space was filled with earth, and Yonge Street was repaved.
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