Again: Don't bury it.
I keep hearing about how we have to protect generations centuries in the future. If civilization falls to savagery, a set of concrete bunkers in the middle of the desert that kills anyone who breaks into it is going to be the least of humanity's problems.
If civilization advances beyond our reckoning, at some point they might be able to close the facilities and change the waste into cotton candy.
Just put it into a facility and watch it.