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Press Release

U.S. Requires Arizona and New Mexico Plant Owners to Reduce Emissions at Navajo Nation Four Corners Power Plant

For Immediate Release
Office of Public Affairs

Today, the U.S. Department of Justice and the Environmental Protection Agency (EPA) announced a federal Clean Air Act settlement with several Arizona and New Mexico-based utility companies to install pollution control technology to reduce harmful air pollution from the Four Corners Power Plant located on the Navajo Nation near Shiprock, New Mexico. 

The settlement requires an estimated $160 million in upgrades to the plant’s sulfur dioxide (SO2) and nitrogen oxide (NOx) pollution controls.  The settlement also requires $6.7 million to be spent on three health and environmental mitigation projects for tribal members and payment of a $1.5 million civil penalty.  EPA expects that the actions required by the settlement will reduce harmful emissions by approximately 5,540 tons per year.

“This settlement is a significant achievement for air quality and the health of the people of the Navajo Nation and the surrounding region,” said Assistant Attorney General John C. Cruden for the Justice Department’s Environment and Natural Resources Division.  “The agreement will require stringent pollution controls as well as public health and environmental projects that will have lasting benefits for the Navajo people.  It is also a reflection of how serious we are about addressing environmental justice issues in Indian country.” 

“All power plants should be using the latest air pollution control technology,” said Assistant Administrator Cynthia Giles for EPA’s Office of Enforcement and Compliance Assurance.  “The law requires companies to protect clean air, and those living nearby – like Navajo communities – expect it.  In addition to installing pollution controls, Arizona Public Service will also take the responsible steps to protect the health of those living near the Four Corners plant, which is one of the largest sources of harmful pollution in the country.”

“This settlement will reduce pollution from the Four Corners Power Plant for years to come, and requires the Plant's owners to fund significant health and environmental projects that will further benefit the Navajo Nation and other communities impacted by the Plant,” said U.S. Attorney Damon P. Martinez for the District of New Mexico.  “We also applaud the efforts of the citizen groups and other co-plaintiffs who helped represent the interests of the Navajo people and the environment so well, and who contributed significantly to obtaining such a fine result for the Four Corners Region.”

Arizona Public Service Company (APS) is the operator and primary owner of the Four Corners Plant.  El Paso Electric Company, Public Service Company of New Mexico, Salt River Project Agricultural Improvement and Power District and Tucson Electric Power Company are current co-owners of the plant and Southern California Edison Company is a former co-owner of the plant.  The settlement resolves claims that the companies violated the New Source Review provisions of the federal Clean Air Act by unlawfully modifying the Four Corners Power Plant without obtaining required permits or installing and operating the best available air pollution control technology.  

The pollution controls for NOx required by the settlement improve the Selective Catalytic Reduction controls for the Four Corners Power Plant finalized by EPA in 2012 under the Clean Air Act’s regional haze program.  The current controls for SO2 will be upgraded to increase their efficiency. These additional upgrades will reduce SO2 emissions by approximately 4,653 tons per year and NOx emissions by approximately 887 tons per year.

The settlement requires $6.7 million of mitigation funds to be spent on three types of projects, including cleaner heating systems, weatherization and a Health Care trust fund. Southern California Edison will spend approximately $3.2 million on a project to replace or retrofit local residents’ inefficient, higher-polluting wood-burning or coal-burning appliances with cleaner-burning, more energy-efficient heating systems.  In addition, APS and the other current co-owners will spend approximately $1.5 million for weatherization projects for local homes to reduce energy use.  Examples include the installation of floor, wall and attic insulation; sealing of windows and doors; duct sealing; passive solar retrofits; and testing and repair of combustion appliances. 

Finally, APS and the other current co-owners will spend $2 million to establish a Health Care Project trust fund.   The Health Care Project trust will pay for certain medical expenses for people living on the Navajo Nation, near the Four Corners Power Plant, who require respiratory health care.  The funds may be used to pay for complete medical examinations, tests, review of current medications, prescriptions, oxygen tanks and other medical equipment.  The funds may also be used to pay for transportation to and from the hospital or doctors’ offices.

SO2 and NOx, two predominant pollutants emitted from power plants, have numerous adverse effects on human health and are significant contributors to acid rain, smog and haze.  These pollutants form particulates that can cause severe respiratory and cardiovascular impacts and premature death.

This settlement is part of EPA’s national enforcement initiative to control harmful emissions from large sources of pollution, which includes coal-fired power plants, under the Clean Air Act’s Prevention of Significant Deterioration requirements.  The total combined SO2 and NOx emission reductions secured from all these settlements will exceed 2 million tons each year, once all the required pollution controls are installed and implemented.

Citizen groups including Diń́é Citizens Against Ruining Our Environment, To’ Nizhoni Ani and National Parks Conservation Association are co-plaintiffs to the settlement and will simultaneously be resolving their own currently pending lawsuit against the companies.

The settlement was lodged with the U.S. District Court for New Mexico and is subject to a 30-day public comment period and final court approval. The proposed consent decree can be viewed at

More information about EPA’s enforcement initiative:

Updated April 5, 2024

Press Release Number: 15-791