Acid mine drainage (pit lake), Broken Hills, Nevada. Chemicals that leach out of mine tailings result in high concentrations of acids in puddles, ponds, and if containment fails, streams and rivers. This is a tiny--but very poisonous--puddle. I have also seen gigantic pit lakes in Nevada. The old Anaconda Copper Mine in Yerington has a very large pit lake. It is an EPA Superfund site, that like so many others, just sits there.
