At 2.25 gigawatts, Arizona’s Navajo Generating Station is the biggest coal-burning power plant in the Western US. The plant, and the nearby Kayenta coal mine that feeds it, are located on the Navajo Indian Reservation, and the Navajo and Hopi peoples have had a conflicted relationship with coal since the plant opened in the 1970s. Almost all the 900-plus jobs at the mine and plant are held by Native Americans, and the tribes receive royalties to account for large portions of their budget.

Negotiations were underway to improve the tribes’ lease terms, which expire in 2019. But on Monday, the four utilities that own most of the plant voted to close it at the end of 2019. They decided that the plant’s coal-powered electricity just can’t compete with plants burning natural gas. A press release from Salt River Project, which runs the plant, explained, “The decision by the utility owners of [Navajo Generating Station] is based on the rapidly changing economics of the energy industry, which has seen natural gas prices sink to record lows and become a viable long-term and economical alternative to coal power.”

The US Bureau of Reclamation owns a portion of the plant—using the power to run the Central Arizona Project that carries water from the Colorado River all the way to Phoenix and Tucson—and it’s at least possible that the tribes could work out a deal to keep the plant running under a different ownership arrangement. Salt River Project's press release included a statement from a Bureau of Reclamation official that “Department of the Interior’s preferred path is to explore ways in which the plant could operate economically post-2019.”

As High Country News notes, the lease negotiations included consideration of a plan to close one of the plant’s three turbines and replace the generation with renewable energy. But the economically vulnerable tribes will be hard-pressed to immediately replace the critical jobs and revenue associated with coal should the plant close three years from now. The flip-side, of course, is that closing the plant (as well as the mine) would eliminate a significant amount of pollution and water use.