Utah regulators’ ideas for cutting emissions from coal-fired electrical plants is under fire from environmentalists who dismiss it as a rehash of a flawed plan the Obama-era Environmental Protection Agency has already rejected — twice.

Under the Clean Air Act, the state is obligated to minimize “regional haze” that obscures vistas at national parks and other protected airsheds with the goal of achieving “natural conditions” by 2064.

Emissions from two power plants in Emery County impair visibility at Utah’s five national parks and three others in neighboring states, according to Cory MacNulty, associated director for the Southwest region of the National Parks Conservation Association.

She was among the critics lined up at public hearing Wednesday to denounce the plan before the Utah Air Quality Board, arguing that it allows a corporation to foul the air over Utah’s redrock country with avoidable emissions of nitrogen oxides, or NOx.

“This is pollution that obscures up to 87 miles of the landscape that should be visible through Delicate Arch at Arches National Park, from Island in the Sky at Canyonlands National Park,” MacNulty said. “These same facilities are emitting substantial amounts of greenhouse gases contributing to climate change.”

The proposal under consideration this month is a federally mandated revision to a controversial plan the Utah Division of Air Quality negotiated with PacifiCorp, Utah’s largest utility, more than a decade ago to substantially cut emissions of particulate matter and sulfur dioxide from the Hunter and Huntington plants.

“The plan we developed focused on those two [pollutants] because that’s where we had the biggest visibility impacts,” said agency Director Bryce Bird. Those upgrades have been installed, as well as retrofitted burners that don’t put out as much NOx, a pollutant that regulators say doesn’t impair the clarity of the air as much as sulfur dioxide and PM.

Bird’s boss Alan Matheson, who heads the Department of Environmental Quality, said the plan not only protects the view of Utah’s scenery but also insulates electrical customers from “significant price hikes" that could result were the state to require upgrades envisioned by the EPA under the Obama administration.

“Utah implemented pollution controls years ahead of schedule to achieve early visibility improvements,” he said. “The most accurate modeling tools demonstrate the state plan clears the skies over our parks as effectively as the federal plan, but at a cost of hundreds of millions of dollars less.”

HEAL Utah, Sierra Club and other environmental groups, however, insist the state should go further and require scrubbers that remove much of the NOx from the exhaust coming from four of the plants’ five units subject to the regional haze rule. This equipment, known as selective catalytic reduction, or SCR, is now an industry standard in place at 269 plants around the country, including some that PacifiCorp operates outside Utah, and could reduce NOx emissions by 76 percent, activists said. That would cut annual emissions by 10,000 tons from Hunter alone.

The utility contends it would cost $700 million to install SCR at its Hunter and Huntington plants and another $150 million in operational costs over the lives of the plants.

Activists disputed those figures and argued SCR is worth the investment, considering the importance of Utah’s scenery to its economic foundations.

National Park Service modeling indicates that human-caused haze disrupts views on more than 300 days a year at Arches and Canyonlands, according to retired park manager Philip Brueck, who lives in Saratoga Springs.

“The state must do the right thing and hold PacifiCorp’s Hunter and Huntington coal plants accountable, requiring that their pollution be reduced so that visitors have the opportunity to experience the extraordinary beauty that these iconic national parks of the Southwest have to offer now and in the future,” said Brueck, a member of the Coalition to Protect America’s National Parks. “As stewards of these beautiful lands, if we have the opportunity to improve any aspect of the environment that we live in, why wouldn’t we want to do that?”