Look at the facts:
AK mining dam engineer (forgot his name) said in a mtg in Dillingham years ago "all tailings dams leak". It takes a massive pump back system to "mitigate" the effluent. Forever! 
Most all (>90some %) of open pit mines have created water contamination issues.
Most, if not all of those mines, occur in desert environments.
Pebble prospect is located in essentially a swamp.
Bristol Bay is the largest salmon producer in the world because we have allowed all the others to be destroyed by fragmenting or polluting the vital habitat.
People only think about the adult salmon that we harvest, eat, or run up the river. But w/o intact habitat and water their is no place for the eggs to incubate or the juvys to survive long enough to head to the ocean (where habitat is also being stressed) to come back to our plates, smokers, or to spawn.
The state of Alaska permitting process is flawed. We have never denied a development/extraction project.
Think long v short term! 
EPA=help