Cheers, Thanks for the info.

I'm not sure how generally applicable it is. When you have several acres of undeveloped land full of sand at your disposal it's relatively trivial to dig a pit, mix some concrete from the sand you excavated, and pour a subterranean cellar to house a battery bank and other hazardous infrastructure. Nobody would even notice it happened/exists.

The situation is far more complicated for folks in apartments or high density housing.