Digging a 10.7-metre diameter tunnel, Diggy Scardust is the largest tunnel boring machine (TBM) ever used on a project in Canada.

Project owners Metrolinx have published an article how its extraction shaft (24 meter deep) has been built. Nothing extraordinary. But still it is good that they hace documented it with nice photos and published.

https://www.metrolinx.com/en/discover/how-we-built-the-scarborough-subway-extension-tbm-extraction-shaft