A long-running dispute over pollution from taconite mines finally landed in court Wednesday when three environmental groups sued the state of Minnesota, charging that it has allowed the massive Minntac waste pit in Mountain Iron to degrade lakes and trout streams for decades.

The 10-mile long tailings pit, owned by Pittsburgh-based U.S. Steel Corp., operates under a permit that expired 24 years ago and has not been updated with more recent standards designed to protect water, wildlife and wild rice. As a result, the suit says, the tailings basin is discharging water that violates seven state pollution limits and has destroyed the wild rice that once thrived in two nearby lakes.

“There are many industries in Minnesota that comply with the Clean Water Act, and the [state] effectively regulates them,” said Hudson Kingston, an attorney with the Minnesota Center for Environmental Advocacy, which filed the suit in Ramsey County District Court on Wednesday. “But the mining industry has not been one of them.”

A spokesman for the Minnesota Pollution Control Agency (MPCA), the lead regulator, said the agency is aware of the lawsuit but is not able to comment. Officials at U.S. Steel also declined to comment.

Minntac’s tailings permit has long been a sore point with environmental groups, Indian tribes and the U.S. Environmental Protection Agency (EPA). At least 15 of the state’s mining permits have expired, but Minntac’s is the oldest.

U.S. Steel has taken steps to collect tainted water and monitor pollutants at the Minntac operation, but the MPCA has been working on a new permit for years. One critical issue is how the state enforces its long-held standard regulating sulfate; the pollutant forms when waste rock is exposed to air and water, and can damage wild rice. Sulfate also contributes to a chemical process that can turn mercury into an organic form that contaminates the food chain, building up as a toxin in game fish and other wildlife.

In 2015, U.S. Steel officials warned the Legislature that mining jobs could be jeopardized if Minnesota tried to enforce the sulfate standard. After that, officials with the MPCA said they would not issue a new permit for Minntac until they had crafted a revised sulfate standard, which is now expected to be completed in 2018.

The lawsuit asks the judge to order the MPCA to issue a new permit for Minntac by a certain date — one that includes limits on discharges from the tailings basin and that complies with state and federal laws. It also asks the judge to require the MPCA to prevent Minntac from polluting water, air or destroying natural resources around the facility.

Kingston said the complaint relies on the MPCA’s own water quality data showing that water from the pit is significantly above legal limits for sulfate, dissolved solids and three other standards. That could simplify the case, allowing it to go to trial as early as next year, and perhaps compel the state to issue a permit before it completes the new rule for sulfate, he said.

The two other groups joining the suit are the Save Lake Superior Association and Save Our Sky Blue Waters, both based in northern Minnesota.

Minnesota’s regulation of mining is under intense scrutiny because of a new permit application by PolyMet Mining Corp. for a proposed Iron Range copper-nickel mine — a much riskier type of mining that has polarized Minnesotans along a jobs-versus-environment fault line.

The Minntac mine and tailings pit were built in the 1960s atop northern Minnesota’s Laurentian Divide, which separates the St. Louis River Watershed from the Rainy Lake Watershed. While most of the state’s taconite operations drain south and east toward the St. Louis River, which has long been affected by mining, Minntac also sends water north toward the pristine Boundary Waters Canoe Area Wilderness and Canada.

The lawsuit is just one of several efforts to pressure the MPCA to be more aggressive in its regulation of mining. The EPA, which delegates the enforcement of federal environmental laws to the state, has repeatedly pressed the agency to make new mining permits a higher priority. In late 2014, the EPA tangled with the state on Minntac specifically, when it suggested in a strongly worded letter that a proposed permit for the mine was not in line with the Clean Water Act and other federal laws because it had no clear deadlines to fix pollution problems.

Last year, in response to a complaint by the Minnesota environmental group WaterLegacy, the EPA launched an investigation into the state’s regulation of mining, which could take years to complete.