Sorry for the thread jacking.
Talking about tunnels reminded me about a video I watch a month ago. An automated way of building the tunnel before you bore it.
https://youtu.be/bfJY0syocfU
Only brought it up because it would sound like a Morrow thing of building something in stealth. Still have to get rid of the slurry as was suggested earlier.
I assume that you could bring in the huge equipment at the end to remove the excess material. Maybe allow it to look like a much smaller operation.