We're talking about 237,000 tons of arsenic here, just from just one mine. Enough to, “kill the entire human population of our planet a few times over”. BTW the land seems primarily Native land:

2016 Vice article lays it out.

2021 CBC article that debunks claim that the arsenic is naturally occurring.

I'd heard about the story today via Reddit here It seems that many users mention how the profits are private, but any potential clean-up will be public.