Cominco, Teck, Rio, Anglo, FM knew and many others know. https://www.adn.com/opinions/2020/01/12/ive-worked-in-mining-for-decades-pebbles-environmental-impact-statement-is-fatally-flawed/
"In my professional opinion, the small mine being evaluated by the draft EIS is almost certainly not economically feasible, with likely financial losses in the billions of dollars. A much larger mine would almost certainly need to be constructed to attain a positive rate of return on the very large initial capital investment. The EIS thus fails to evaluate the true environmental impacts and risks associated with a viable mining project. Even a small expansion of the project to extract 20% of the ore body would almost double the size of the disturbed footprint, quadruple water quality risks and likely spread large-scale impacts into three different river drainage basins. Although such a mine expansion would need to be re-permitted, the artificial fragmentation of the full-scale mine plan would hide the full environmental harm of the project until after half of the impacts had already occurred. This is clearly unfair to the people of Alaska, who wish to make an informed decision about the relative benefits, impacts and risks of the project."