I am also curious about what happens to the water in the mine. Did the hole, big enough to swallow the drilling rig and several barges, seal up, and were the workings then pumped dry? If the water is still there, presumably it would become a saturated solution, but I am wondering if that could still erode the salt, on account of continual exchange of ions between the solution and crystals of salt? Or would the water be entirely absorbed into the salt crysyals, given that NaCl and other salts are hygroscopic? If I were a local resident, I would have more than a mild curiosity in these questions.
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.
On the other hand, I see that the storage cavities were created independently of, and some distance (horizontally and vertically) away from the flooded mine, which should answer their concerns that the flooding had made the proposal risky.
https://web.archive.org/web/20190215050528/http://www.aglres...
