1overcosc
Active Member
The Confederation Line tunnel is extremely shallow. Where this incident happened, the roof of the tunnel is only five metres below the street. Normally, tunnels that shallow (like the original Yonge subway) are dug cut and cover. Ottawa is able to dig a shallow bored tunnel only because of its unusual geology (bedrock right below the surface) and even then it creates problem as this incident demonstrates.
A DRL would almost certainly be much deeper, as a bored tunnel in Toronto's geology would have to be deep. Ergo, it would avoid this problem of bumping into parking garages.
A DRL would almost certainly be much deeper, as a bored tunnel in Toronto's geology would have to be deep. Ergo, it would avoid this problem of bumping into parking garages.