Great Chart, unfortunately, this is what the report that goes with it actually says -
The Pebble Mine and its host environment are not comparable with other Alaska mines or their environments. That Pebble poses a greater threat to the environment or fishery does not mean that the practices at other, less threatening mines are not problematic. It simply implies that Pebble poses greater qualitative and quantitative threats than any other Alaska mine to fisheries, the environment, and cultural and economic resources.