I was there this spring or last fall - can't remember. I did not trespass, but I consciously looked at the condo area.
I attach a sketch from City of Toronto website. From the property line, I drew 8.6m and it is well away from the building. The subway is 3m wide x 2 direction, plus 2 x 0.75m wall thickness for the retaining structure = 7.5m wide strip needed.
What is needed is a retaining wall about 60 to 100m long. This would vary in height, reaching about 8m maximum. Instead of this though, I would propose "tunnel" that is retaining the embankment on the north, covered above, and open to the south (or discrete columns with openings). This serve to retain the embankment, reduce noise to condo, and open on the south so it doesn't count as a tunnel along with the pedestrian egress requirements of a tunnel.
Construction would be a sheet pile wall (that will be left in place, or possibly pile and lagging) against the embankment, then some excavation of the embankment and building concrete "tunnel" structure. This would progress westward in small increments until the entire structure is built.
The old Canadian Tire and the next factory over are more in the way, but if this area is expected to redevelop, they will be gone.
Plus: The cost of this "tunnel" would be about $20M
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