Environmental groups made good Monday on a promise to sue Kennecott Utah Copper over air pollution.

Utah Moms for Clean Air, Utah Physicians for a Healthy Environment, the Sierra Club of Utah and WildEarth Guardians are demanding that the mining giant scale back its operations to pre-2007 levels and pay penalties of about $68 million for violating the Clean Air Act for nearly five years.

"This is a very simple clean-air lawsuit," said Jeremy Nichols, of WildEarth Guardians. "There are people at stake here. There are communities at stake here. There are families at stake here."

The suit comes as Kennecott, which insists it already is complying with its state license, pursues plans to expand as part of its Cornerstone Project.

Filed on Monday in U.S. District Court in Salt Lake City, the suit comes after the groups vowed in August to take legal action. It notes Kennecott is one of Utah’s biggest sources of particle pollution, partly from dust kicked up as crews dig and haul ore from the massive open pit mine in the Oquirrh Mountains on the Salt Lake Valley’s west bench and partly from fossil fuels being burned to operate vehicles, equipment, the smelter and the mine’s power plants.

Kennecott spokesman Kyle Bennett said the suit is "without merit." In keeping with the company’s commitment to sustainability and the well-being of its workers and the community, he added, Kennecott complies with strict, health-based pollution limits set by state and federal regulators.

"We are absolutely in compliance with those limits," he said. "We take that seriously."

In 1994, the U.S. Environmental Protection Agency, which delegates responsibility for upholding federal law to the Utah Division of Air Quality (DAQ), approved a state pollution-control plan that allowed Kennecott to move 150.5 million tons of ore and dirt a year.

Five years later, the state granted the company’s request to haul 197 million tons of material a year. And, in May, DAQ approved Kennecott’s bid for a new limit of 260 million tons, an amount needed to expand the copper pit and extend the mine’s life through 2028.

For the first permit change, state regulators say, Kennecott found ways to offset additional dust from the increased material hauled. And, for the recent permit change, the company expects pollution to decrease — despite the added earth moving because it would cut emissions by using clean-air fuels, paving roads with gravel instead of dirt and launching other emission-reduction measures.

Both permit changes also passed a technical review by state regulators, a public-input process and a vote of the Air Quality Board.

The EPA never signed off on either change.

Without that approval, clean-air advocates say, Kennecott is bound by the 1994 limit.

But DAQ Director Bryce Bird said his agency followed the law both times in allowing Kennecott to step up production. He noted that the company had demonstrated in each case that its activities wouldn’t cause PM 10 violations.

"That’s the burden of proof they had to meet," Bird said, "to get those production increases approved."

But the environmental groups argue Kennecott is reaping multibillion-dollar profits at the expense of the health of northern Utahns, and they said Monday that now is the time to put a stop to those polluting practices.