Sounds pretty interesting.
It was. PPG also injected water into the ground into the salt deposits. The brine was pumped to the plant to electrolysis cells to make sodium and chlorine. The sodium was reacted with the limestone to make soda ash for glass production. The chlorine was used to make phosgene. Plant is gone since the early 1970's. The is a small token production of certain chemicals now but nothing like it used to be.