Minnesota will expand a surface mining buffer zone around the Boundary Waters Canoe Area Wilderness after determining its existing rules didn't do enough to prevent light and noise pollution, according to a decision released Wednesday.

The announcement from the Department of Natural Resources comes after the agency was ordered by a court to re-examine regulations for nonferrous mines, or those that extract minerals other than iron, like copper and nickel.

The agency said in a 74-page decision filed in Ramsey County Court on Wednesday that it will begin rewriting its rules to expand the size of a protective minerals management corridor next to the Boundary Waters. Mining of any kind is banned in the Boundary Waters, and mining that disturbs the surface is banned in the corridor.

"It is encouraging that they [DNR] recognize the inadequacy of the rules," said Ingrid Lyons, executive director of Northeastern Minnesotans for Wilderness (NMW), which challenged the agency's rules.

A DNR news release also noted that the agency will ask state lawmakers to address other concerns about mine waste storage and leaching raised by the public through comments collected about its rule in 2021. The agency reviewed 4,000 messages and letters.

"We received many comments that raised questions about the State's policy and risk tolerance around nonferrous mining," DNR Commissioner Sarah Strommen wrote in a statement. "We believe these broader policy questions are more appropriately addressed by Minnesota's Legislature."

DNR's decision stems from a 2020 lawsuit filed by NMW. The suit argued that the DNR hadn't done enough to protect the Boundary Waters from pollution and degradation because the state's rules didn't cover all of the Rainy River headwaters watershed, which flows south to north, through the 1.1 million acre preserve.

Twin Metals, a company attempting to open a copper mine near Ely, Minn., intervened in the suit. Company spokeswoman Kathy Graul wrote in a statement that it was reviewing the DNR's decision, and that the state already had "some of the most rigorous standards in the world."

Twin Metals, a subsidiary of Chilean mining giant Antofagasta, faces major hurdles. In January, the Biden Administration imposed a 20-year ban on mineral leases on 225,000 acres of national forest land in northern Minnesota, including the company's mine site.

Last year, the administration also canceled Twin Metal's mineral leases. The company sued in federal court, where the case is still pending.

Graul wrote on Wednesday that "we remain committed to advancing a modern mining project that is protective of the environment and that meets or exceeds all state and federal standards."

While the DNR is taking action based on light and noise concerns, the agency will not consider air and water issues as it re-examines its rule. In its decision, it pointed to existing Minnesota Pollution Control Agency regulations that already protect air and water quality.

"We like the destination. We've got some questions about how they got there," Lyons said.

Hardrock mining of copper and nickel — which would be new to Minnesota — risks compounds in the rock interacting with air and water to create acid drainage.

NMW and Twin Metals both have 30 days to challenge the decision by asking for a contested case hearing, where parties can bring experts before a judge to analyze the details of the DNR's decision.

Lyons said NMW is still deciding whether to pursue a hearing on the air and water issues the agency did not address.

Twin Metals did not comment on whether it would challenge the DNR's decision.