ROBERT SIEGEL, HOST:
The water temperature of some canals in South Florida has been rising. And that's a problem when the canals are used to cool a nuclear plant. The situation at the Turkey Point plant near Miami has federal regulators concerned. And the plant's closest neighbors are worried, too. NPR's Greg Allen explains how the canals work and why the water is getting warmer.
GREG ALLEN, BYLINE: The cooling system at Turkey Point is unlike that used at any other nuclear plant in the country. Instead of cooling towers, water circulates through a 168-mile long series of canals. Florida Power & Light spokesman Mike Waldron says that water helps keep the plant within safe operating limits.
MIKE WALDRON: It cools the nonnuclear side of the power plant and is discharged back out into the canal system. And what it actually does is it allows us to use the same water over and over for cooling.
ALLEN: It's a system that's worked since the plant went online more than 40 years ago. The closed loop of saltwater canals have been successful in another way. They've become prime habitat for American crocodiles, an endangered species that have thrived in the unusual, man-made habitat. But in recent months, those cooling canals have run into problems. A shortage of rain and algae growth have been steadily raising the temperature of water in the canals to the point where it's threatening operations at the nuclear plant. As water temperature in the canals approached 100 degrees, the limit set by the Nuclear Regulatory Commission, Florida Power & Light went to the commission with an emergency request. The NRC agreed to temporary allow the nuclear plant's cooling system to exceed that 100 degree limit - up to 103 degrees if necessary. Waldron says the NRC action allows the nuclear plant to keep operating.
WALDRON: It allows us adequate margin to maintain generation during what are very hot and humid summer months in South Florida, while we're also dealing with some of the environmental issues that have caused the canals to become warmer than they typically are.
ALLEN: There are many concerned about what's happening in the canals at Turkey Point. They include state and federal regulators, environmental groups and the nuclear plant's closest neighbor, Biscayne National Park. Brian Carlstrom is the park's superintendent.
BRIAN CARLSTROM: We're standing on the - one of the docks of the Biscayne National Park looking to the South, and the prominent feature on the skyline is the Turkey Point power plant.
ALLEN: You can see the reactors containment domes from most places in the park. But it's the canals and the poor quality of the water they contain that is Carlstrom's biggest concern. Over the years, with evaporation, the water in the canals has become super saline, at least three times as salty as seawater. Because it's heavier than freshwater, water from the canals has begun sinking into the aquifer. The utility and state regulators are monitoring a plume of super salty water that's now moving into the area's groundwater. Carlstrom says when he learned of new problems in the canals, his first concern was for how they might affect water in Biscayne Bay where algae is already a problem. So far, he says, the park and the bay have been unaffected.
CARLSTROM: We're still concerned. Anytime there's that big of a change in a closed system like that adjacent to the park, we want to err with an abundance of caution and make sure that nothing's going to happen that could potentially influence the park.
ALLEN: The utility received permission from state regulars to add chemicals to the canal waters to alleviate the algae problem. Also to bring down the temperature, it's taking 5 million gallons a day of brackish water from the aquifer and adding it to the canals. Roger Hannah with the Nuclear Regulatory Commission says rising temperatures in the cooling system don't raise the temperatures of reactors, but they do affect operations.
CARLSTROM: It does mean that there's some efficiencies lost. And, again, we're looking now at what safety implications there may be to see if there are further things or additional information that we may want to know.
ALLEN: The NRC's permission for Florida Power & Light to raise the cooling system's temperature is just for 10 days. The federal agency and the utility are hopeful that by then increased cloud cover and rain in Florida may provide a natural solution to the problem. Greg Allen, NPR News, Miami. Transcript provided by NPR, Copyright NPR.