pebble was happy to talk. >> nobody can guarantee there won't be an accident, right? but we've done a hell of a lot to minimize the possibility of there being an accident on this site. >> reporter: pebble mine would sit in a wetland prone to earthquakes, so the biggest worry is a tailings dam failure like this one in british columbia, which sent a lake full of acidic waste downstream. but collier says the mine site is so far from bristol bay, that is a risk he can live with. >> if there is an accident, it will kill fish for about 20 miles down the north fork of the cockatooly, and that's it. and for ten years. it will come back naturally. >> reporter: utah's bingham canyon is the biggest mine in the world. pebble has enough wealth to dig one three times bigger. but after all the resistance, those plans have been cut in half. >> and there are some theories that you shrink the footprint of the mine in order to get the