Toronto subway tunnel project passes halfway construction milestone
Construction of the Scarborough Subway Extension in Toronto has passed the halfway mark, marking a key milestone in one of Canada’s largest underground transit infrastructure projects.
The project, led by Metrolinx, includes excavation of a 10.7-meter-diameter tunnel that will ultimately extend Line 2 of the city’s subway network into Scarborough. Once complete, the tunnel will span approximately 7 kilometers and is expected to be the largest-diameter subway tunnel ever built in Canada.
More than half of the tunnel has now been excavated using a tunnel boring machine (TBM), with nearly 2,000 precast concrete segments installed to line and support the tunnel. The project uses a single, large-diameter tunnel to accommodate two tracks, rather than the twin-tunnel approach used in most subway construction.
Officials said tunneling progress has resumed steadily following earlier delays caused by challenging ground conditions that temporarily halted the TBM. Work is ongoing as crews continue advancing toward completion of the underground alignment, which will support expanded transit capacity in the Greater Toronto Area.
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