Eighteen states, the U.S. Chamber of Commerce and other groups are urging an appeals court to overturn a coal ash cleanup order at a federal utility's Tennessee plant.

The states' 6th U.S. Circuit Court of Appeals brief argues the decision at Tennessee Valley Authority's Gallatin Fossil Plant expands federal oversight and could require ash cleanups elsewhere, costing ratepayers tens of billions of dollars.

Another brief filed by the National Mining Association and others says the decision upends federal rules addressing groundwater contamination at coal ash impoundments.

A third Chamber-led brief says permitting costs could increase by billions of dollars nationwide.

In August, a judge ordered Gallatin's ash excavated and removed. He cited Clean Water Act violations of pollutants leaking into the Cumberland River, but said there's scant evidence of harm.