The Tennessee Valley Authority expects it will cost about $2 billion to excavate leaking coal-ash storage ponds at its Cumberland River power plant, near Nashville. In an Aug. 4 order, a U.S. district court judge directed the federal power producer to remove coal-ash slurry from multiple unlined ponds to dry storage at a landfill.

The utility estimates there are more than 10 million cu yd of the waste suspended in water at the Gallatin plant, said spokesman Scott Brooks. That is at least double the amount that was stored at its Kingston plant, which in 2008 spilled 5.4 million gallons of waste across farmland and into the Clinch River. While that spill was caused by an impoundment collapse, Gallatin ponds currently are leaking into the groundwater and flowing to the river through the limestone and karst terrain that underlies them. Between 1970 and 1978, about 27 billion gallons of waste­water flowed from the karst aquifer to the river, the order noted. The first of the 976-MW plant’s four units was built in 1953.

The court held that an unauthorized discharge action may be brought based on discharges to groundwater if a hydrologic link to the river can be traced. TVA argued that specific sinkholes or other linked karst features have not been identified, but Judge Waverly Crenshaw said they are obscured by a thick layer of coal ash. “While the burden of closure by removal may be great, it is the only adequate resolution to an untenable situation that has gone on for far too long,” he said.

TVA prefers to cap the waste in place, Brooks said. Crenshaw said the consequences of a past decision to build the pond on karst terrain should not be addressed by covering them “but to pull them up by their roots.” The ponds are “reasonably likely to continue discharging pollutants,” the order said. Two state environmental groups in 2014 sued, claiming TVA violated the U.S. Clean Water Act. A trial is set for early this year. TVA has not decided whether to appeal the ruling.

In another coal-ash-storage ruling involving pollution through hydrological groundwater connections, a Virginia federal district court on Aug. 3 held that utility Duke Energy had attempted to preempt a citizens’ lawsuit alleging violations at its Roxboro, N.C., plant by seeking a venue change to its northern neighbor.

The Roanoke River Basin Association had notified Duke in March that it would file suit in federal court in North Carolina. Two days before it could legally file, Duke asked the Virginia court to dismiss the case. In its ruling, the court said Duke engaged in “forum shopping,” noting that under the U.S. clean-water law, the filing must be in the venue in which the violation occurred. Duke wanted the suit heard in Virginia because the suit was also brought by a state-based group that cited risks to Virginia rivers, says a spokeswoman.

The U.S. Environmental Protection Agency is reviewing a 2015 coal-ash disposal rule that requires utilities to decide by October whether to clean out coal-ash ponds or cap them, with required monitoring. Advocacy group Earthjustice challenged EPA Administrator Scott Pruitt’s decision to order that review.