Entergy Corp was denied a request for a water-quality certification for its Indian Point nuclear power plant in New York, setting back efforts for a 20-year renewal of its license to operate the controversial plant.

The company said on Sunday it plans to appeal the decision by New York State’s Department of Environmental Conservation.

The state on Friday concluded that the plant’s cooling systems, whether operated as they have been for decades or modified under a proposal by Entergy, “do not and will not comply with existing New York State water quality standards.”

Entergy said the ruling could force it to spend $1.1 billion over 19 years to build new cooling towers.