PHOENIX (AP) — A federal court has denied two legal challenges to federal clean-air regulators' plan for reducing haze by limiting emissions from the Navajo Generating station, a coal-fired plant in northern Arizona. Rulings Monday by the 9th U.S. Circuit Court of Appeals turn down challenges filed by the Hopi Tribe and by environmental and conservation groups. One ruling said the Environmental Protection Agency acted reasonably in setting limits on nitrous oxide emissions.Read more on NewsOK.com