Often undertaken by subsistance miners with hand tools .. eg: Coober Pedy is surrounded by a rabbit warren of tunnels 30 ft down and fanning out following opal.
Admittedly that's "soft" rock, but 30 foot is shallow underground mining compared to major league underground mines and open cut super pits.
In Reddit hand wringing land where your 3-gal homeowner air compressor gets called a bomb, yeah sure it's a major undertaking.
15-30ft holes in the ground can be constructed with bog standard earthmoving machinery that isn't even "wide load" so it's "within normal capabilities" by professional or military standards.
Often undertaken by subsistance miners with hand tools .. eg: Coober Pedy is surrounded by a rabbit warren of tunnels 30 ft down and fanning out following opal.
Admittedly that's "soft" rock, but 30 foot is shallow underground mining compared to major league underground mines and open cut super pits.
In Reddit hand wringing land where your 3-gal homeowner air compressor gets called a bomb, yeah sure it's a major undertaking.
15-30ft holes in the ground can be constructed with bog standard earthmoving machinery that isn't even "wide load" so it's "within normal capabilities" by professional or military standards.