It is a natural consequence of urban development. Not really that different from Yorkville/Annex in Toronto. I used to live on Lowther and Bedford where there are tons of two story homes in the shadows of high rise buildings.
I imagine a couple of reasons in addition to the cost of preserving all or parts of the structure: (1) there is probably no underground parking and (2) the location of the building may not make it ideal to build 4 towers on the site. So I guess it all all boils down to cost.
I agree though I do worry about air conditioning. They mix circulated air with air from outside and all units are supposed to have filters in the intake outlets but I don’t know how effective they are.
Drum is talking about typical shoring where drill boreholes are filled with steel beams and concrete. This technique was not used with M1 and M2 since bedrock in those locations is only few feet under the top soil.
That portion of the site is being used by the company constructing the Burnhamthorpe water main project. The “pool” is water waste from hydraulic drilling machines used along many points of the project.
More info about the project Here
I have seen few of them in Mississauga (one was going relatively very fast.) I suppose you would treat them like cyclists but it was unnerving driving next to them as they could be erratic or still learning.
I am guessing it could be because all modern construction is aided by GNSS/GPS based instruments which are probably calibrated against a standard vertical position. The so called mean sea level, MSL, is a standard geo vertical model which itself is defined in terms of GNSS measurements.