[estaseuropano]

That is simply wrong. Underground storage is not a panacea. Few mines are suitable and even those require expensive preparation and maintenance for coming decades or even centuries, with many hard to predict risks (think earthquake, flood).

[jojobas]

Few mines is all we need. The entirety of the USA would need just one such site.

There's plenty of nasty natural stuff underground and a well-designed mine storage site would be a lesser risk than continuously radioactive coal power plants of today.