I heard about a program to develop those kinds of bombs near the beginning of the latest conflict in Iraq. There are probably a few out there, but not many.
My only concern in using them would be would the radiation leaks damage the groundwater for the survivors of the conflict. Would taking Kim Jong Il out with a bunker buster nuke be worth it, if we also kill many of his people by poisoning their ground water?
I can't answer your question about ground water contamination. I can only counter, does the risk of bioweaponry use, the cost in lives from such an attack and the possibility of taking out the bioweapons by deep-ground preemptive strike balance out the concern about possible water contamination?
Aww, c'mon---no self respecting commie dictator would dig his bunker where there was even ANY groundwater. Every tunnel rat knows if the ground is not dry and the blast doesn't get you the steam bubble would. And what radiation LEAK would you mean? Unless the blast fizzles there's nothing left to SOAK.