The massive hurricane expected to reach the Eastern Seaboard on Friday will bring with it heavy rainfall, which environmental advocates fear could lead to toxic washouts of coal ash repositories in parts of the Southeast.

Hurricane Florence has been downgraded to a Category 2 storm, but forecasters said that parts of the North Carolina coast where the storm is expected to come ashore could see rainfall of more than 30 inches. If the storm slows to a crawl, as some forecasts predict, rainfall will not only be torrential but prolonged.

Inside Climate News reported that Hurricane Matthew, a Category 1 storm, caused a breach in a cooling pond and a leak of coal ash at a power plant on the Neuse River in North Carolina when it struck two years ago. Flooding from Hurricane Florence could be much worse.

Sam Perkins of the Catawba Riverkeeper Foundation, an organization that monitors waterways in North Carolina, said that some coal ash piles are 100 feet high.

“Unless you have been on a river or lake and seen these up close, it’s tough to realize how high these piles are,” he said.

There are 71 surface impoundments for coal ash at power plants in Georgia, South Carolina, North Carolina, Virginia, and Maryland, according to Earthjustice. In addition, there are 29 ash dumps in those states. According to Inside Climate News, the ash contains arsenic and heavy metals that could contaminate rivers and, potentially, public drinking water supplies.

Utilities in North Carolina and Virginia have been slower to clean up ash piles than other states, according to Frank S. Holleman III of the Southern Environmental Law Center. Of particular concern, he said, is a site on the Cape Fear River near Moncure, North Carolina, where cracks in its dams have shown up in the past. That’s just northwest of Florence’s expected landfall in Wilmington.

“If Duke Energy and Dominion would simply remove its coal ash from all its unlined waterfront pits and move its ash to safe, dry, lined storage away from waterways or recycle it for concrete, then there would be nothing to fear from coal ash when a hurricane makes landfall in North Carolina or Virginia,” Holleman told Inside Climate News.

Duke Energy said it has extra staff and equipment ready to respond to any problems.

Impact on solar farms another concern

The Carolinas also are the nation’s second biggest solar region, Bloomberg said, and companies were taking steps to protect photovoltaic installations from high winds. Sunpower, for example, said it was changing the angle of solar trackers in the path of the storm, a precaution that has helped in the past.

“If the panels were vertical to the ground, it would be like a sail to the wind,” SunPower Corp. CEO Tom Werner told Bloomberg. “That would be the worst case.”

Most newer solar installations are designed to withstand winds of up to 160 miles per hour, Bloomberg said, but the region has not been threatened by such a powerful storm since the solar boom started there in 2014. North Carolina now has 4.4 gigawatts of installed solar arrays, according to the Solar Energy Industry Association, making it second only to California.

More than 504,000 homes in the state are powered by solar energy, with the total number of installations greater than 7,500. Rooftop systems also are built to handle hurricane-force winds. “As long as the roof stays on, so do the solar panels,” Sunrun spokeswoman Georgia Dempsey told Bloomberg.

With a downgrade to Category 2, Hurricane Florence is posing less of a wind threat than earlier in the week.