The records request to the Minnesota Department of Natural Resources resulted in the release of 17 files of e-mails to and from the agency's commissioner since Jan. 1. The topic: PolyMet and Twin Metals, the two controversial copper-nickel mines proposed in northeast Minnesota.

Much of the correspondence requested by the Editorial Board involved legislators for or against the projects, with some asking for more details from the lead permitting agency. But what wasn't in the documents was more enlightening than what was. Only once was there a specific mention of the Twin Metals mine. The rest concerned PolyMet.

While PolyMet is further along in the approval process, and process irregularities have prompted court action, the dearth of discussion about the Twin Metals mine is disturbing. The project, which is owned by a Chilean mining conglomerate, would be located on the doorstep of the state's beloved Boundary Waters Canoe Area Wilderness (BWCA). It has been mired for months in its own controversy — with questions raised about politics, not science, driving federal decisionmaking.

Twin Metals also made a major announcement in July — that it is switching to the "dry stack" method of waste rock storage. The company, which touted dry stacking as "environmentally friendly," said it "eliminates the storage pond and dam associated with conventional tailings facilities." It instead compresses waste rock into a "low-moisture, sandlike deposit" stored on the ground.

Scrutiny of the decision by lawmakers, Gov. Tim Walz and others is in order, but there's little in the e-mails to suggest adequate follow-up. That's unacceptable. There are serious questions about whether dry stacking could heighten the risk of BWCA pollution rather than reduce it. Those concerns shouldn't take a back seat to questions about PolyMet. Here's what Minnesotans deserve to know:

Mine waste will be closer to the BWCA. The dry stacking decision means the leftover rock will now be stored at the mine site instead of at a holding facility in a different watershed. The Twin Metals mine is planned perilously close to Birch Lake, whose waters flow north into the BWCA. While Twin Metals says that up to half the waste rock will be stored underground, the rest won't be. Any pollution from the waste pile would have a direct water route to the wilderness. Twin Metals is projected to mine 20,000 tons per day.

The DNR has a different take. Twin Metals and the DNR are sharply at odds in their conclusions on dry stacking. The DNR considered the storage method for the PolyMet project but rejected it, partly due to the state's climate. In a 2018 report on PolyMet, the agency found no "meaningful environmental benefits" and said dry stacking could generate "significant pollution." One possible pollutant: "fugitive dust" containing potentially reactive materials such as sulfur that "could spread over nearby lakes and forests or could be carried out to populated or tourist areas."

Dry stacking's success is dubious. Twin Metals has said that dry stack storage has been "successfully used" in four mines in the northern U.S. and Canada. One of the mines is Greens Creek in Alaska. Elevated levels of heavy metals have been documented in sea life near it since its opening. Guy Archibald, a scientist with Southeast Alaska Conservation Council, had a one-word answer when asked if dry stacking had been a success there: "No."

A key state environmental group also criticized Twin Metals last week. The mine firm's communications frequently mention the Minnesota Center for Environmental Advocacy (MCEA) and its preference for dry stack storage at the PolyMet site. MCEA leaders said this week that this does not equal support for Twin Metals and said the company has been "misleading."

In e-mail exchanges with an editorial writer, Twin Metals officials said that the company "knows from more than a decade of research" that mine waste can be safely exposed to air and water. And that the mine will not create acid runoff, a claim that merits additional scrutiny.

Twin Metals continues to call for open, honest and respectful conversations about mining in Minnesota. Those discussions are clearly needed, and they should be based on complete information, a condition so far unmet.