Floodwaters surrounded several buildings at the Fort Calhoun Nuclear Station early Sunday morning after a water-filled wall collapsed.
The plant, about 19 miles north of Omaha, remains safe, Omaha Public Power District officials said Sunday afternoon.
The U.S. Nuclear Regulatory Commission is monitoring the Missouri River at the plant, which has been shut down since early April for refueling.
The 2,000-foot berm collapsed about 1:25 a.m. Sunday due to “onsite activities,” OPPD officials said. The Aqua Dam provided supplemental flood protection and was not required under NRC regulations.