Toxic waste should be stored underground as that method would have the most assurance of keeping the waste contained and of protecting it from weather and vandalism. Storage above ground would be more susceptible to damage that might result in leakage. The underground storage facilities would need to be quite strong and monitored carefully because they would not be totally secure from problems.
Sure. Store it underground in secure bunkers. Underground, overground, underwater, above water. Ultimately, it does not matter as long as a logical containment system is built around them. Also, when storing underground we need to make sure we don't loose track of where we put things. Yes, this has happened in the past.
I think storing toxic waste underground could open up a whole host a problems as the toxic waste infects the soil and eventually could get into the water supply of an area, I think there needs to be intense studies on the most effective containment of toxic waste but storing it underground is not something we should be doing.
When toxic waste is stored underground it can leak. These leaks then go into the environment and cause significant problems. Toxic leaks have very real and negative effects on the environment and people living in it. The best way to store toxic waste is in sealed containers or outer space.
Since people are the reason that toxic waste exists in the first place, they should shoulder most of the risk. Storing this waste underground does not deal with the issue, and puts the environment at more risk than the people who made it. This will bring the issue forward as a topic of discussion.