I actually live about 100 miles north of the WIPP site. I'm fairly unconcerned about danger. This area was an inland sea ~250 million years ago (the continents

I actually live about 100 miles north of the WIPP site. I'm fairly unconcerned about danger. This area was an inland sea ~250 million years ago (the continents were gathered together in Pangaea at the time). The salt deposits in the mine that WIPP occupies are precipitate from this sea drying down and are very deep. If the site were collapsed (which I understand it will be at some point) people with primitive tools won't be digging it back up. It is simply too deep. It isn't going to erode down to the level they can either in any reasonable period of time....i.e. millions of years. A society technologically advanced to dig this stuff up presumably will be aware of some history and/or be able to decipher what is written on the marker. Unless civilization disappears in which case it will take a long time to re-develop the technology needed to dig that deep starting from ground zero. Also... people need a reason to go to great effort. I just don't see future people digging that far in the earth out of curiosity and with no immediate economic benefit. But just in case.... if you need a marker to discourage them, how about instead of abstract symbols we put some pictures of the effects of radiation on humans with the material containers notably present in the picture? The one thing I guess that could become an issue is the amount of oil well activity in the area. It is geologically stable, there are no earthquakes, but maybe fracking could change that. I hope they are taking future fracking into account in their equations.