A year ago, four environmental groups threatened to sue over Clean Water Act violations, saying the plant was discharging toxic pollutants from its unlined coal ash ponds.

The groups say the Brunner Island plant is discharging toxic pollutants including arsenic, boron, sulfate, and lithium from its unlined coal ash waste ponds.

States may be able to stop monitoring at some sites, and power plants have more time to close leaking ash ponds.