Since the stuff could well have melted itself into the snow and ice very slowly, and might have moved laterally considerably, I guess you'd effectively have to skewer a giant, largely vertical glacier down to the rock below, with rocks of all sizes peppered in, using heavy machinery that doesn't exist yet, at high altitude where just surviving at all is a challenge, with lots of very extreme weather, avalanches, rockfall, crevasses, icefall... in a remote area that is hard to access in the first place. That's absolutely herculean. That would almost certainly cost lives. That would be ridiculously expensive. Chances are that Pu won't become a big issue during your term, and it's just one of what must be hundreds or thousands of gambles any Indian (or any other) government must be taking on issues that possibly might become huge liabilities with some small-ish likelihood. Meanwhile, launching such an endeavor because of a few kg of poison at the very end of the world, because it might somehow endanger 200 millions, that's going to be brutally tough. That's a danger that is very far from intuitive. There are legitimate reasons to argue against the endeavor being worth the cost. Probably not the hill PM Modi wants to die on.