FLAGSTAFF, Ariz. (AP) — The U.S. Environmental Protection Agency was expected to meet a deadline Thursday on a plan to control emissions from three Arizona power plants that it contends have impaired visibility at places like the Grand Canyon, but a spokesman for the agency said the details wouldn’t immediately be available.

The EPA had proposed approving Arizona’s air-quality plan to reduce sulfur dioxide and soot at the Cholla, Coronado and Apache coal-fired plants. But when it came to nitrogen oxide emissions, the EPA suggested the state’s plan didn’t go far enough and came up with one of its own.