(WRAL) -- Thousands of gallons of water flowed out of a cooling pond at a retired Duke Energy power plant on Wednesday after part of the retaining wall on the 545-acre pond gave way.

Duke officials had stated repeatedly in recent days that flooding along the Neuse River after Hurricane Matthew had had very little impact on the coal ash basin and the cooling pond at the Goldsboro plant.

Spokeswoman Erin Culbert issued a statement noting the 50- to 60-foot break in the wall holding in the estimated 1.2 billion gallons of water in the pond, which was used to cool equipment at the coal-fired power plant before it was taken out of service in 2012.

Duke officials said they expect the water from the cooling pond to add less than 1 inch to the rising levels of the Neuse.

"The active ash basin is not impacted by this incident and continues to operate safely," Culbert said.

Still, environmentalists were upset that Duke appeared to be downplaying the risks of the flooding to the ash pond, noting the earthen dams surrounding Duke's coal ash ponds are similar to the one that gave way at the cooling pond.

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