Business as usual. Using available space effectively. In the 90s I went to a customer site south of St Louis to install some electronic equipment, it was in a similar looking former mine. There was no entrance control, just a bid hole in the side of a hill. The customer was a music duplication business, duplicating 1000s of cassettes from studio masters. They said it was a perfect place, no radio or electrical interference. There were dozens of other businesses in the same mine.