I can’t agree with Carla Arneson’s letter to the editor. Her claims are all hypothetical in nature. No actual facts based on this potential mine. If she wants, she can Google Dr. Rens Verburg, a Principal Geochemist with over 30 years of experience, and find his article on Twin Metals and why Acid Rock Drainage is a zero issue and/or https://www.twin-metals.com/resource/twin-metals-minnesota-project-acid-rock-drainage-white-paper/. It explains it quite well.
Since there is no Twin Metals analysis, no permits to mine, or anything else for that matter, in any environmental analysis, it’s all hypothetical. Any NEPA project like this will have a multi-year process. It will take 10-20 years before any shovel is in the ground or not. Everyone will have more than enough time to address any concerns. The state has come a long way in recent years, and I believe they would do the right thing during an environmental analysis, whether they permit a mine or not. They are the ones that issue the permits after all and are supposed to protect the waters of the BWCAW.
Here are some concerns I have about the dry stacking of tailings: What testing will be done of the tailings as they are built up? Is limestone going to be added to neutralize acid if sulfate levels are detected in the tailings? How is rainwater dealt with in the tailings? Is the state going to require capping of the tailings with a Hypalon liner or bentonite before covering it with native soils to mitigate water intrusion and thus preventing possible low-level sulfates from escaping into the ground water?  So many more questions.
If people want to do any good, donate to the White Iron Chain of Lakes (WICOLA). They are trying to get funding for a pilot project to reduce as much as possible sulfate pollution from a 50-year-old mine dump that eventually flows into Birch Lake and then 18 miles by water into the Boundary Waters. 
Daniel Hernesmaa
Ely