Dive Brief:

• Duke Energy's Brunswick nuclear plant in North Carolina declared a low-level state of emergency on Monday due to floodwaters caused by Hurricane Florence, but regulatory officials said public safety was never at risk.

• Brunswick declared an "unusual event," the lowest-level of emergency notice, when high water blocked access to the nuclear plant, a spokesperson from the Nuclear Regulatory Commission (NRC) said. The plant was shut down ahead of the storm and remains stable.

• NRC rules require a utility to declare an unusual event when access to a nuclear facility is impeded, and Duke cannot restart the plant until access to the facility is regained. Nearly 327,000 people remain without power in North Carolina due to the hurricane, according to PowerOutage.US.

Dive Insight:

Brunswick's low-level emergency declaration on Monday is a reminder of the risks of siting nuclear generation close to ocean coasts. In 2011, three reactors at Tokyo Electric Power's Fukushimia Daiichi nuclear plant melted down after an earthquake and ensuing tsunami, killing one person and releasing radioactive material into the air and water around the plant.

The Fukushima disaster prompted reforms of nuclear safety codes around the world, and NRC officials said the emergency event declared by the Brunswick plant on Monday is a far cry from that event.

"Both of the units [at Brunswick] safely shut down well in advance of the storm," NRC spokesperson Joey Langford told Utility Dive. "They remain safely shut down. No plant equipment or safety equipment was damaged in the storm or since."

Brunswick remained in "hot shutdown" mode during the event, Langford said, and still had grid power to cool the reactors. The facility has backup generators in the event that grid power is lost.

With access to Brunswick blocked by floodwaters, essential plant employees slept on cots at the facility and received supplies from Duke by helicopter, the News and Observer reported.

Record-breaking rains also caused a coal ash spill at Duke's Sutton power plant in North Carolina over the weekend, releasing enough of the harmful waste product to fill two-thirds of an Olympic sized swimming pool, according to the utility.

The Environmental Protection Agency told reporters Monday they were investigating a second ash release at the Sutton plant, which Duke said was part of the first spill. EPA referred questions about the event to Duke, and late Monday a spokesperson for the utility said it and the agency "have connected and all agree there was one event at Sutton."

"The releases of water and ash from the Sutton landfill have stopped, and repairs are already underway," Duke spokesperson Paige Sheehan said via email. "The public and environment remain well protected."

Over the weekend, Duke said weather conditions made it difficult to ascertain whether coal ash from the Sutton plant had entered an adjacent cooling pond at the facility or the nearby Cape Fear River.

Inspections on Sunday revealed that ash itself had not entered the waterways, the utility said, but rainwater that came into contact with the waste product did, and some ash leaked into a nearby industrial facility.

"This 1,100-acre cooling pond was constructed by Duke Energy to receive treated water from plant operations, including water from coal ash basins when they were operating," Sheehan wrote. "At that time the lake would further process that wastewater — it is performing the same function today with this release."

Duke says coal ash is not hazardous, a label based on the EPA's decision in 2014 to classify the substance as "solid waste," rather than "hazardous waste" under federal disposal laws. It does, however, contain heavy metals and other substances known to cause health problems in humans, such as mercury and lead.

In addition to monitoring ash spills and its nuclear plants, Duke is also working to restore the millions of customers who lost power as part of the Category 1 hurricane. Utilities in the region have already restored power to 1.4 million customers affected by the storm, the Edison Electric Institute said Tuesday morning, but some of the toughest work remains in areas that are "inaccessible and that experienced massive flooding and structural damage."