Environmental Protection Agency efforts earlier this week to curtail the way some U.S. utilities are disposing of coal ash could hamper Georgia Power’s plans of dealing tens of millions of cubic yards of the material near the Chattahoochee River and elsewhere in the state.

Coal ash includes potentially toxic leftovers from combustion at coal-burning generating plants. Such material often sits in on-site impoundments at electric plants around the nation.

Georgia Power has asked state regulators to let it leave its ash — without protective liners underneath — at plants near Smyrna, Rome, Newnan, Carrollton and Juliette. State regulators say the bottom of the ash at those plants sits in anywhere between a foot of groundwater to more than 50 feet. Environmental groups and some neighbors worry about contamination migrating off site.

On Tuesday, the EPA said it was restating the federal agency’s “consistently held position” that coal ash sites cannot be closed with the material in contact with groundwater. Limiting such contact “is critical to minimizing releases of contaminants into the environment and will help ensure communities near these facilities have access to safe water for drinking and recreation.”

An EPA official this week also asked the Georgia Environmental Protection Division to review its pending and issued closure permits for coal ash sites to ensure they comply with the federal interpretation of standards. Georgia is one of only three states that has received special authorization to issue coal ash closure permits that would typically be handled by the federal agency.

Kevin Chambers, a spokesman for the state EPD, wrote in an email that the state was informed of “the potential change to the performance standards.”

“We are awaiting further clarifications and discussion with our federal partners,” Chambers said, and any impact on pending applications ”is unknown at this time.”

A Georgia Power spokesman wrote in an email that the company is evaluating the EPA’s position. The Atlanta-based utility will “continue to work with them, as well as Georgia EPD, to safely close our ash ponds.”

The company’s proposed $9 billion cleanup plan, which will likely be paid by its customers, includes removing some ash to lined landfills. But Georgia Power has asked to leave three-fourths of the ash in updated sites beside current or former plants. They would have protective covering and surrounding monitoring wells to track any potential contamination. Most would not have a synthetic liner underneath, which are typical protections required at regular landfills.

The state regulators have taken heat from environmental groups and people who live in communities around the plants. Some complained about an early draft permit issued by the Georgia EPD that, if finalized, would allow more than a million cubic yards of coal ash — enough to fill 5,400 tractor trailers — to sit forever in an unlined site along the Coosa River near Rome.

Frank Holleman, a senior attorney with the Southern Environmental Law Center, said he thinks state regulators will not try to buck their federal counterparts “now that the EPA has made it clear to them, which should have been obvious in the first place.”

Staff writer Drew Kann contributed to this article.