The National Parks Conservation Association and other clean air advocates, represented by Earthjustice, reached an agreement today with the Environmental Protection Agency (EPA) and the owners of New Mexico’s Four Corners Power Plant to reduce the plant’s pollution and improve the health of surrounding communities and national parks.

“For far too long, the irresponsible management of Four Corners has denied the Navajo people the basic human right to clean, healthy air in our communities,” said Lori Goodman, board member of Diné Citizens Against Ruining Our Environment (Diné CARE). “Now with this settlement, Four Corners will have to take steps to stop poisoning our air and start moving toward a healthier future.”

Four Corners, located on the Navajo Nation in New Mexico, is responsible for dirtying the air in Grand Canyon and 15 other national parks in the Southwest. Over the last 30 years, the owners of the plant made changes that resulted in additional pollution. In 2011, NPCA, Diné CARE, and To’ Nizhoni Ani filed a lawsuit asserting that the plant violated the Clean Air Act by increasing emissions without also installing best pollution controls.

Under the consent decree, the plant will reduce emissions of nitrogen oxides and sulfur dioxide –major contributors to both respiratory health problems and haze in the parks. The owners will also pay $1.5 million in civil penalties and $6.7 million in healthcare and other mitigation costs for the affected communities.

“Pollution from Four Corners has sickened local communities for decades despite plenty of opportunities for the plant to clean up its act,” said Nicole Horseherder of To’ Nizhoni Ani. “Today's agreement provides a much needed investment in the health and wellbeing of those residents.”

“After years of dangerous pollution, this settlement is a welcome shift towards a cleaner, more just future for the people and parks of the Southwest,” said Kevin Dahl, Arizona senior program manager for the National Parks Conservation Association. “Clearer skies over parks like Mesa Verde and Petrified Forest are good news for visitors, nearby communities, and the local economy.”

“This legal victory represents a relentless and inspired fight led by members of the Navajo Nation and concerned local leaders, who refused to give up on the health of their community,” said Earthjustice attorney Mary Whittle, who represented the groups. “It’s a shame it takes a legal battle to hold the operators of this dirty coal plant accountable, but we’re glad to see action to clean up the air around Four Corners.”

Once the nation’s single largest source of nitrogen oxide emissions, Four Corners’ pollution has long been recognized as a threat to the region’s health. In 2009, NPCA and Diné CARE submitted comments to the EPA demonstrating that the Regional Haze Rule—the Clean Air Act program designed to reduce air pollution in national parks—required Four Corners to clean up its emissions. The following year, the EPA proposed limits that cut 85% of the plant’s nitrogen oxide emissions.

Plant owners offered their own pollution mitigation plan, which called for closing the first three coal units at Four Corners and installing best controls for nitrous oxide pollution at the remaining two units. Those first three units closed at the end of 2013.