ATLANTA (AP) -- Environmental groups urged Georgia officials to reject plans by Georgia Power to keep coal waste in ponds at several power plants.

The utility plans to leave coal ash in unlined retaining ponds that will continue leaching toxic metals after they are closed, the Southern Environmental Law Center said in a letter to Georgia environmental officials on Aug. 5. The storage pits would be submerged in groundwater, according to the environmental group.

"Although Georgia Power will add no more ash to the waste ponds, nearly fifty million tons of coal ash will remain, continuing to degrade and occupy the aquifer, and continuing to leak coal ash and its pollutant-laden leachate into the environment and surrounding public waters," said the letter signed by Christopher Bowers, senior attorney with the Southern Environmental Law Center. It was addressed to two state officials in the environmental protection division of the Georgia Department of Natural Resources and also written on behalf of three other environmental groups.

A Georgia Power spokeswoman said in a statement that the letter contained "incorrect assumptions and several critical inaccuracies that mislead the public of our ash pond closure process."

The environmental protection division declined to comment on the letter, spokesman Kevin Chambers said.

Coal ash is the waste product left behind when coal is burned. It contains contaminants such as mercury and arsenic that can pollute ground water if not properly managed, according to the U.S. Environmental Protection Agency.

The Southern Environmental Law Center cited decisions by other states requiring utilities to excavate ash and put it in lined disposal structures.

In her statement, Georgia Power spokeswoman Holly Crawford said the utility's plans "have always been, and continue to be, in compliance with all federal and state laws and regulations."

The company has roughly 500 groundwater monitoring wells around ash ponds and on-site landfills and has identified no risk to public health or drinking water, she said.

The company said last year it was excavating 17 ash ponds next to lakes or rivers and using "advanced engineering methods and technologies" to close others.

The utility plans to keep nine ash ponds in place at plants in Macon, Newnan, Smyrna, Rome, and south of Carrollton, according to the Southern Environmental Law Center.