Before revision: Six of those main reasons are: The mine ceases to be economically important Depletion of raw materials Political reasons, war or accidents Instability of the mine workings Prevention of disulfide oxidation Safety reasons In some locations, flooded mines have been converted into pumped-storage hydroelectric reservoirs .
After revision: Six of those main reasons are: The mine ceases to be economically important Depletion of raw materials Political reasons, war or accidents Instability of the mine workings Prevention of disulfide oxidation Safety reasons In some locations, there are discussions to use flooded mines for, but finished projects are still missing pumped-storage hydroelectric reservoirs .