Well the same mine, on the same 1300 ft level, had a water intrusion related collapse about 10 years prior that killed 4 miners. Without any oil drilling going

Well the same mine, on the same 1300 ft level, had a water intrusion related collapse about 10 years prior that killed 4 miners. Without any oil drilling going on in the area. Part of the engineering involved in the design of these mines is based on leaving enough salt, such that X" of salt on the surfaces will be dissolved by the mine eventually being flooded, either intentionally or not. After that surface-salt is dissolved (and the water approaches being supersaturated brine), enough solid structural salt needs to be left to support all of the overburden, with some additional factor of safety. Worst case would be some sort of underground fresh water river flowing through indefinitely. But mine design incorporates ways to naturally seal off flooded areas, such that even if they are left "open" to some connection of water, the supersaturated brine will effectively plug that hole. Usually as simple as changing elevations so that a brine-water interface forms that blocks any natural flow. And once water is supersaturated with salt, salt is no longer "hygroscopic", in the sense that it's no longer water, but brine.