The "L" in PLP stands for "limited liability".  They know about the ring of fire and know earthen dams have failed all over the world without volcanic and seismic impact.  They just do not care.  If something happens, they'll scatter like cockroaches, and the corporations will no longer exist.  

It is "interesting" however that 39 percent of tailing pond dam failures happen in the US.

https://news.vice.com/article/tailings-ponds-are-the-biggest-environmental