The Environmental Protection Agency has rejected Colorado’s state haze control plan, arguing that the required shutdown of several coal plants would harm grid reliability.

The EPA said on Friday that it would disapprove Colorado’s revised 2022 Regional Haze State Implementation Plan (SIP) after the state’s attempt to shut down several coal plants without consent, which the agency said does not comply with the Clean Air Act and is not necessary to meet requirements. It also noted that the shutdown of coal plants may disrupt the grid.