A federal judge ruled against the Tennessee Valley Authority (TVA) and how it stores coal ash near its four-unit coal-fired Gallatin power plant.

The ruling comes after a trial that claimed TVA violated the Clean Water Act by storing coal ash in unlined storage ponds. The Southern Environmental Law Center argued that TVA's practice violated the act.

The judge ordered TVA to excavate the existing ash pond and move the waste to a lined landfill.

The 123-page ruling says [pdf], "The ponds continue to be unlined. The terrain continues to be [limestone]. There is substantial evidence that the surrounding groundwater is hydrologically connected to the Cumberland River and that some of that groundwater contains coal ash pollutants in significant levels. While the Ash Pond Complex has undergone some repairs, none of those repairs were of the sort that would have negated the fundamental features of the Complex that make it so prone to leak."

TVA had argued that no direct link existed between the ponds and the Cumberland River. The environmental groups filed a motion that said TVA's own testing showed otherwise.

The court said that the environmental groups' own experts characterize their sampling strategy as designed to "identify the existence of leaks and not calculated to establish their extent or severity." Little evidence exists to lead the court to "conclude that TVA’s violations are particularly severe, in terms of the harm done or the amount of pollutants released."

Coal ash is a byproduct of burning coal for electric power generation. It may contain heavy metals like arsenic, mercury and lead.

A TVA spokesman said the utility was reviewing the order to determine its next steps, including a possible appeal.

TVA is in the process of building a dry storage landfill, but reportedly is waiting on direction from the state.

In December 2008, an ash dike ruptured at a solid waste containment area at TVA's Kingston Fossil Plant. Around 1.1 billion gallons of coal fly ash slurry was released into a nearby river.

In a separate case, a federal judge in late July barred TVA [pdf] from implementing a new vegetation management approach until it has completed an environmental impact statement as part of the National Environmental Policy Act. TVA can no longer remove trees taller than 15 feet near power lines, according to the ruling by Chief U.S District Judge Tom Varlan.