Residents of Georgetown County, South Carolina, where five rivers flow into the ocean, were preparing on Friday for a deluge of water in the aftermath of Hurricane Florence, which has killed at least 40 people.

The county of 60,000 people, on the Atlantic coast between Myrtle Beach and Charleston, is one of several areas in the Carolinas waiting anxiously for rivers to crest, a week after Florence dumped some three feet of rain on the region. Flooding could begin early next week, officials said during a community meeting on Thursday.

The city of Georgetown on Friday will hand out 15,000 sandbags as the county develops plans to evacuate residents. “Please heed the warnings,” Sheriff Lane Cribb said. “Protecting lives and property will be our goal … You better pray.”

Thirty-one deaths have been attributed to the storm in North Carolina, eight in South Carolina and one in Virginia.

More than three dozen flood gauges in North and South Carolina showed flooding, according to the National Weather Service.

Some 4,700 people across North Carolina have been rescued by boat or helicopter since the storm made landfall, twice as many as in Hurricane Matthew two years ago, according to state officials. About 10,000 remain in shelters.

The coastal city of Wilmington, North Carolina, remained cut off by floodwaters on Thursday, and more than 200 state roads were closed or blocked. Over 60,000 customers were without power in North Carolina early on Friday.

As floodwaters continued to rise, concerns grew about environmental and health dangers.

Duke Energy Corp said on Friday that breaches in a cooling lake dam forced it to shut down its natural gas-fired L.V. Sutton plant in North Carolina. The utility said it could not rule out the possibility that coal ash from a dump adjacent to the plant, which formerly burned coal, might be flowing into the nearby Cape Fear River.

Coal ash can contaminate water and harm fish and wildlife.

The flooding from Florence has also caused 21 hog “lagoons,” which store manure from pig farms, to overflow in North Carolina, possibly contaminating standing water, according to the state’s Department of Environmental Quality. North Carolina is one of the leading hog-producing states in the country.

Several sewer systems in the region also have released untreated or partly treated sewage and storm water into waterways over the last week, local media reported.