Comment by KaiserPro

it is ridiculously labour intensive.

First, all utilities have to be mapped out, then any basements shored up.

Then once the cut and cover is in progress, all utilities have to be re-routed, during, then replaced after the tunnel is cut.

Then, the disruption of having major transit ways shut for n weeks.

Lastly, there isnt a machine to do it. The TBM is pretty efficient labour wise.