A summer legislative hearing is imperative to address new and serious questions about how a state agency handled the final stretch of the permitting process for a proposed copper mine in northeast Minnesota.

A leaked e-mail and documents newly released by the U.S. Environmental Protection Agency (EPA) put a troubling spotlight on the PolyMet Mining Inc. project. PolyMet is one of several copper mines proposed in the state's mineral-rich but environmentally sensitive Arrowhead region.

It's by far the furthest along in the permitting process. The state Department of Natural Resources issued critical permits last fall for the $1 billion project — after 14 years of environmental reviews. But PolyMet still needed water and air quality permits from another state regulator — the Pollution Control Agency (PCA). The PCA issued those approvals last December. But the new EPA documents and the leaked e-mail that came to light this month have generated legitimate alarm about the PCA's decisionmaking.

Specifically, the documents released by the feds suggest that EPA officials were concerned about the project's ability to meet water-quality standards. That's a big deal because of the dangerous pollutants that could be discharged. The mine is located in a water-rich environment in the Lake Superior watershed.

The e-mail also raises questions about whether a former PCA staffer tried to keep EPA feedback out of the public eye and record. She requested that the EPA officials not submit written comments during a certain time frame.

The federal's agency input was read verbally over the phone. State and federal officials, as well as PolyMet executives, have said this is not an unusual way to exchange information, and some said it's even preferable. But it's hard to understand how reading a multi-page technical document over the phone, with state staff members taking notes, would be efficient. A retired EPA attorney's recent comments calling it "bizarre" underscores this.

PolyMet executives told an editorial writer this week that it was "grossly unfair" to suggest a lack of transparency or due diligence given the "exhaustive administrative record." In addition, "lost in all the hyperbole" is that the "EPA did not object to the final permit issued by the state," the company said.

At the same time, the EPA's Office of Inspector General has launched an investigation into the permitting process, suggesting not all here is "hyperbole." Scrutiny is needed at the state level, too.

State Rep. Rick Hansen, DFL-South St. Paul, has asked Legislative Auditor Jim Nobles for a review. That does not excuse lawmakers from calling a hearing, however. In particular, the public needs to hear from Shannon Lotthammer, the former PCA staffer who wrote the leaked e-mail.

Bolder leadership is also needed from Gov. Tim Walz and his administration. At a January news conference announcing agency leadership picks, Walz stated that his administration won't dodge tough environmental questions and that it try to offer a "reset" on divisive issues.

The PCA's PolyMet permitting decision was made under Gov. Mark Dayton's administration. But the PCA's defensive public comments under Walz until this week have unfortunately reflected the age-old strategy of protecting the agency bureaucracy.

Walz issued a welcome statement shortly after undergoing knee surgery last week. Going forward, no Minnesota employee is to delay or discourage public comment. The governor also is directing the PCA to review staff practices surrounding the permit and determine what changes are necessary to prioritize transparency.

Copper mining brings both economic opportunity and environmental risks, especially from acid runoff. Minnesotans must have confidence in the state's ability to regulate this new industry. The questions about PolyMet sow doubts not just about this mining proposal but about others to come. A hearing will be crucial to shoring up public trust.