(CN) - The 10th Circuit upheld the government's plan for regulating emissions at a coal-burning power plant on the Navajo reservation in New Mexico. A three-judge panel rejected lawsuits filed by the plant owner and environmentalists, who challenged the restrictions as too strict and not tough enough.
Under the Clean Air Act, the federal government can enforce state emission plans approved by the Environmental Protection Agency. The EPA previously approved New Mexico's state plan, which limits the emission of certain pollutants from coal-fired power plants.
The New Mexico plan does not apply to the Four Corners Power Plant, according to the EPA, because the plant is located on tribal land in northwest New Mexico.
Although plant operator Arizona Public Service Co. complied voluntarily with the state plan, the plant's emissions remained officially unregulated until the EPA proposed a plan in 1999.
After taking public comments, the EPA finalized its "source-specific federal plan" in 2007, prompting lawsuits from the plant operator and environmental groups, including the Sierra Club and the San Juan Citizens Alliance.
The environmentalists said the regulations were too lenient and failed to sufficiently improve the surrounding air quality, while the Arizona Public Service Co. claimed they were too harsh and unreasonable.
The plant operator claimed it couldn't meet the 20 percent opacity limit - referring to the cloudiness of emissions - with its existing pollution-control equipment.
The environmentalists argued that the "tribal authority rule," which treats tribes as states for most provisions of the Clean Air Act, requires the EPA to impose a stricter federal plan.
The Denver-based federal appeals court rejected environmentalists' call for additional modeling and analysis.
"The federal plan, by necessity, is adequate because the plan is but a stricter version of the satisfactory emissions limits already applied by the Plant and implemented throughout the State of New Mexico," Judge Seymour wrote.
The court also denied the plant operator's claim, saying the EPA "provided a reasoned basis for the 20 percent opacity limit" and has no duty to exempt plant malfunctions from regulation.
Finally, the court granted the government's motion to voluntarily remand a "fugitive dust limit" on the basis that the EPA failed to adequately explain the limit. None of the parties objected.
Read the Top 8
Sign up for the Top 8, a roundup of the day's top stories delivered directly to your inbox Monday through Friday.