The proposal requires safe management of coal ash that was dumped in currently unregulated areas, including inactive power plants with surface impoundments that are no longer in use.
Coal ash contains hazardous pollutants including arsenic, chromium, lead, and mercury, which have been linked to cancer, heart and thyroid disease and other illnesses.
It tends to have a larger impact on low-income, minority communities living near power plants.
The groups that filed the petition last year, represented by Earthjustice, found that the EPA exempted coal ash heaps at 566 landfills and dumps at 242 coal plants in 40 states.
Now, plant owners in states including Illinois, Indiana, Tennessee, New Mexico and Florida with some unregulated coal ash dumps would be required to monitor and clean up all coal ash at a given site, Earthjustice said.