North Carolina’s hog-manure lagoons have stayed contained so far, according to the state, as the region continues to get pelted with rain from the remnants of Hurricane Florence.

The state’s 4,000 lagoons are holding out, even though huge swaths of farmland in the state’s eastern corner are underwater, Gov. Roy Cooper (D) said. The lined earthen pits that hold treated waste had been a major environmental concern as unprecedented rain lashed North Carolina, with at least 30 rivers breaching their banks.

“We are closely monitoring hog lagoons, and we haven’t had any reports of issues,” Cooper said in a...