The largest coal-fired power plant in the West officially shut down Monday afternoon. KNAU’s Ryan Heinsius reports, owners of the Navajo Generating Station closed the facility as the industry faces more competition from natural gas and renewables.

Officials with the Salt River Project say all three units at NGS have been permanently shut down after on-site stockpiles of coal were used up. SRP and the plant’s other owners voted in 2017 to close the 2,250-megawatt plant that had been operating since the mid-1970s.

Two investment firms as well as a Navajo Nation-owned company made attempts to buy NGS and keep it and the nearby Kayenta Mine operating, but the efforts failed. The mine closed in August.

The Navajo and Hopi tribal governments will lose large portions of their revenue without the coal royalties, and the mine closure forced the layoffs of hundreds of tribal members.

SRP will now focus on decommissioning NGS, which will take three years and cost the plant’s owners about $150 million. They’ll also continue to lease the property for 35 years from the Navajo Nation in order to conduct long-term monitoring.