Deep safe nuclear waste repository is now possible Vertical DBHD is half the price and double the safety then the horizontal storage. Some countries have geological maps showing the thickness of the rocksalt layers - other countries have indications rock salt from drilling data. However, the thickness of the sediments above the rocksalt is important and the total thickness of the rocksalt unit if possible. Salt units older than 250 M are claimed to be feasible
For location of world salt units, see USGS report: https://bit.ly/2PqDr59
For details of the new approach, see: https://www.dbhd-hlw.de/dbhd---geology