It's worth considering that the US also used the islands as a dumping ground for waste from previous tests in the US [1] ... At a site which is now under threat of leaking due to the effects of climate change [2]
[1] https://www.latimes.com/projects/marshall-islands-nuclear-te...
I think the only way you could top this would be to place a vault at ground level that spanned the San Andreas fault.
Even more comical is that it's not like we didn't think of that because we literally do use that space for those reasons. We just also decided to fill the atoll with large amounts of nuclear waste... Seemingly for fun. To give the benefit of the doubt, for transportation logistics reasons.
“… the soil and the lagoon water surrounding the structure now contain a higher level of radioactivity than the debris of the dome itself, so even in the event of a total collapse, the radiation dose delivered to the local resident population or marine environment should not change significantly.”
This is just insane.
If dilution is so straightforward then why wasn't the waste mixed with a large volume of sea water and then dumped far out at sea to begin with? That probably would have been cheaper.
Go and see for yourself. /s