one is in a super dense downtown location which makes construction difficult as it is.
Another element is that, in order to avoid underpinning, Osgoode and Queen are being tunneled through bedrock, in order to prevent any shifting of the soil between the new tunnel and the existing station (you can really see this in the way Queen Station puts all the vertical access areas either side of the existing station, with nothing below the existing station until you get down to the concourse level (also within bedrock); which is also true of Osgoode, only the tunnel in the bedrock runs under the existing station). And bedrock depth differs site to site. And while I don't know the specific geology of the area offhand, due to the fact Pape Station is at a greater elevation from sea level than Queen St, it very well might mean that tunneling through the bedrock at this station would mean making the OL station comically deep compared to the surface (and tbh, given this location, even the 45m depth of Queen and Osgoode stations would be a bit ridiculous). Regardless, it's unlikely the bedrock is shallow enough here to be worth tunneling through, so you're stuck doing building in soil, and if you're building entirely within soil, underpinning really is the only answer for any excavation as large as a subway station if you want to avoid any shift of the existing tunnel.
And to unnecessarily take this even further, 40-45 m depth would just narrowly exceed the max grade of 3.5% for ontario line since the south portal to station distance is about a kilometre .
There you go. That's the interchange plan. I was looking at it today as I though underpinning the station met it would be shallower, but its not.
They have to match the TBM tunnel depth or they'll have to buy a whole strip of land both south and north of the station to demolish homes and do some cut and cover. That's definitely a no go these days.
Of course, they should be buying a whole strip of land around the station and demolishing the single family homes anyways, to build appropriately dense housing.
Does it seem like the labels for "Lower concourse level" and "Ontario Line service level" should be swapped? The level at 17.5m seems more like a partial service level.
Except this isn't right beside Pape but 50m east of the street. They did this for the Yonge line between Bloor and College and today it remains mostly parks and parking lots. Bloor-Danforth is mostly parking lots. This so called dense housing won't happen unless the flatten the whole neighbourhood.
There will be some development where the excavations take place, which will be a bit of a focal point. Much higher density than what exists today.
Since they are buying that whole parcel of land, something is more lively to happen.
Metrolinx will be demolishing basically an entire city block here, including most of the storefronts along Danforth between Pape and Eaton.