Twin Metals hasn’t formerly proposed a mining project yet. That’s still months away. Rather, for nearly a decade, the Minnesota-based company, a subsidiary of Antofagasta of Chile, has been conducting mineral exploration and has been preparing to tap a mineral-rich site nine miles southeast of Ely.

A few key things are known already about its plans, however.

One is that the mining is to be underground, meaning far less intrusive than the massive, dust-filled, open-pit ore mines that mark so much of the Iron Range. Also, “Underground mining creates opportunities to target the ore, minimize surface impacts, and eliminate waste rock,” as a company official wrote in a commentary in the News Tribune last month.

Another thing known is that the mining won’t produce environment-harming acid, as the company has said repeatedly, citing “extensive testing.” While critics’ claims to the contrary refuse to abate, Twin Metals Minnesota CEO Kelly Osborne explained it again last week: The rock sandwiching the copper, nickel, and platinum that the company plans to extract “is almost completely free of sulfides,” and “only a minute amount of sulfides will remain” after minerals are removed.

So, “non-acid-generating,” as the company’s press release stated it one more time — a claim that certainly will be scrutinized, as it should be, during an exhaustive and very-public environmental review of the mining plan that’s still to come.

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Last week we learned one more thing about Twin Metals’ plans — and this one seems game-changing. The company announced it no longer plans to store tailings behind a dam, which has been the target of the most vocal of concerns. Critics claim tailings dams inherently leak toxic waste and sometimes fail completely.

Rather than having a dam, the company will employ a “dry stack method,” meaning its tailings will be compressed into low-moisture, sand-like deposits that can then be stored on a lined ground facility nearby. The facility is to be monitored and later reclaimed with soil and trees on top.

(Some tailings will still be mixed with cement and placed back into the underground mine for permanent storage, as had been planned, the News Tribune reported last week.)

“Dry stack tailing storage is the most environmentally friendly tailings management approach,” Osborne said. “There’s no dam (and thus) no risk of dam failure.”

It’s a more expensive option. For one thing, the dry stack method requires an additional 50 employees to manage. But Twin Metals’ additional investment can be seen by our region as nothing but good news. It pushes the job-creation forecast for Twin Metals to a local economy-boosting 700 during operations.

The very environmental groups so critical of Twin Metals — and copper-nickel mining in general — long have been touting the advantages of dry-stack tailings storage. And its success can’t be denied at four mines in the northern United States and in Canada where it’s employed and where climates are similar to ours here in northern Minnesota.

All of which is reassuring and encouraging, no matter what your level of environmental concern. And good to know.