I worked as a geological consultant in the early to mid 70's. On one project, I spent nearly a year visiting and inspecting every underground salt mine in the U.S. I have been in the mine in question. Yes, big companies can make mistakes and Morton made one here. They knew it was a mistake by 1975, as the reason I was there was to see if we could use the mine for a different purpose. Morton was jumping with joy at the thought of being able to unload this mistake, for whatever cash they could get for it. We got the royal treatment while we were there doing our evaluation.
Our client choes to not purchase the facility in the end, and Morton shut the place down. I am glad I was not one of the geologists who told Morton this was a good place to build a salt mine.