A federal appeals court will not reconsider its ruling that Dominion Energy Virginia did not violate the Clean Water Act when arsenic from coal ash stored at the Chesapeake plant seeped into groundwater.

The three-judge panel for the United States Court of Appeals for the 4th Circuit ruled in September that coal ash piles and ponds adjacent to Dominion Energy Virginia's retired coal plant in Chesapeake, Va., do not constitute "point sources" as defined in the 1972 Clean Water Act.

"We conclude that while arsenic from the coal ash stored on Dominion's site was found to have reached navigable waters — having been leached from the coal ash by rainwater and groundwater and ultimately carried by groundwater into navigable waters — that simple causal link does not fulfill the Clean Water Act's requirement that the discharge be from a point source," Judge Paul Niemeyer wrote in the court's opinion.

The court on Oct. 10 denied the Sierra Club's petition for rehearing and rehearing en banc, or before all the judges of the court.

The appeals court decision reverses a federal judge's ruling in March 2017 that the discharge of arsenic through groundwater into the nearby Elizabeth River violates the law. The U.S. District Court judge said Dominion Energy Virginia, known legally as Virginia Electric and Power Co., should be held liable for pollution in groundwater and navigable waters surrounding the plant.

The judge, however, did not impose any civil penalties and rejected the Sierra Club's "draconian injunction" that the Dominion Energy Inc. utility move more than 3 million tons of coal ash to a landfill.

The Southern Environmental Law Center, representing the Sierra Club, filed a lawsuit in March 2015 against Dominion alleging that coal ash pollution is leaking from its impoundments at the Chesapeake power plant into the Elizabeth River. The groups said the Chesapeake power plant, which retired its coal-burning units in December 2014, stores more than 60 years of coal waste onsite in "unlined, leaking pits and a landfill built on top of the old pits."

Dominion has filed plans to close its coal ash ponds at its Virginia power plants, including the Chesapeake site, but lawmakers have extended a moratorium on the necessary permits while Dominion studies beneficial reuse.