RICHMOND, Va. — Potentially dirtier rivers or possible higher electric prices.

An upcoming federal court ruling in Virginia could have far-reaching effects on how energy companies dispose of coal ash waste left over from decades of burning coal. Spurred by high-profile coal ash spills and new federal regulations, utilities are grappling with the disposal of vast amounts of the heavy-metal-laced waste.

In Richmond, Judge James A. Gibney Jr. heard four days of arguments and complex testimony last month from experts about what should be done at a Dominion Virginia Power coal ash site along the Elizabeth River in southeast Virginia. He hasn’t said when he will rule.

Central to the case are questions about the scope of the Clean Water Act and whether it applies to tainted groundwater connected to rivers and other surface waters.

The lawsuit, according to industry and legal experts, is the first of its kind to go to trial in the U.S., and its outcome could help shape future fights over coal ash ponds and the extent to which certain federal regulations apply.

“It’s always been a real gray area the extent you need a Clean Water Act permit for situations where there’s leeching of toxics materials into groundwater,” said Robert V. Percival, director of the environmental law program at the University of Maryland.

Whichever way he rules, experts said, Gibney’s decision is likely to be appealed. But the case could lead to a definitive ruling that affects coal ash disposal around the country.

“This has Supreme Court written all over it,” said Patrick Parenteau, a professor at Vermont Law School who specializes in environmental law.

Environmentalists and utilities are often at odds over coal ash disposal, with environmental groups pushing for excavating unlined coal ash sites near waterways and moving millions of tons of ash to lined landfills less prone to leeching toxic chemicals.

That could cost more than a trillion dollars, said Jim Roewer, executive director of the Utility Solid Waste Activities Group, a Washington-based trade group.

“If you had to clean-close all these facilities it would have a huge impact on the industry,” Roewer said.