Operators of the Cooper Nuclear Station near Brownville said they are optimistic that floodwaters will not force the plant to shut down — at least in the next few days.
The southeast Nebraska nuclear station came within about 18 inches of shutting down early Monday, when the Missouri River level at the plant rose to 43.8 feet.
The Missouri River must reach 45.5 feet (902 feet above sea level) before officials will shut down the plant, which sits at 903 feet.
The plant is operated by the Nebraska Public Power District. NPPD spokesman Mark Becker said the river dropped to 43.1 feet by mid-day Monday and was expected to continue to ebb.
Becker said a problem with the National Weather Service gauge at Brownville led some to conclude that the plant was within 3 inches of a forced shut down.
“We're operating at full capacity,” Becker said. “What we're seeing is the river leveling itself off, but we continue to watch and add protection around the plant.”
The Columbus-based utility sent a “Notification of Unusual Event” to the Nuclear Regulatory Commission when the river reached 42.5 feet about 4 a.m. Sunday. The declaration is the least serious of four emergency notifications established by the NRC.
Becker said workers have been preparing the station for flood conditions by filling sandbags, constructing barricades, stocking materials and supplies, and reinforcing the access road plant staff use to get to the station.
More that 5,000 tons of sand was brought in for constructing barricades, such as Hesco barriers, around the station's switchyard of transformers and other electrical equipment.
The U.S. Army Corps of Engineers said the river at Brownville had surged about 2 feet from Saturday morning to Sunday due to a combination of factors, including heavy rain over a Missouri River tributary, the Nishnabotna River in southwest Iowa.
It was the second time that a Nebraska nuclear power plant has posted a notice of an unusual event with the NRC due to flooding in the past two weeks.
The Fort Calhoun Nuclear Power Plant, operated by the Omaha Public Power District, posted such a notification on June 6. The Fort Calhoun nuclear plant, 20 miles north of Omaha, has been shut down since April for refueling. It has not been restarted because of the flooding.
The river has risen at least 1.5 feet higher than Fort Calhoun's 1,004-foot elevation above sea level. The plant can handle water up to 1,014 feet, according to OPPD.
In northern Missouri on Sunday, water was flowing over two levees choking off two more routes for people attempting to cross the Missouri River.
The surging water closed U.S. Highways 159 and 136 in western Missouri, which means drivers could no longer cross bridges at Brownville and Rulo, Neb. A spokeswoman for the Nebraska Department of Transportation said Sunday that the bridges are expected to be closed for the foreseeable future.
A third crossing, at Nebraska City, was closed when Iowa officials closed Highway 2 from the river to Interstate 29 due to rising water. All Missouri River bridges between Plattsmouth, Neb., and St. Joseph, Mo., are now closed.
At Omaha on Monday, city officials said the Nebraska National Guard has a Black Hawk helicopter is staged at Eppley Airfield if needed for flood emergencies. The helicopter can deploy sandbags weighing 1,500 pounds each in the event of a levee breach, officials said.
Sunday evening, officials at Lake Waconda near Plattsmouth advised all remaining residents to evacuate because of the appearance of several “sand boils” near the levee there. Sand boils occur when water under pressure wells up through a bed of sand and can contribute to levee failure.
Lisa Hathaway at the Lake Waconda caretaker's officer said engineers from the Corps of Engineers were en route to the levee Monday to try to determine its condition. Hathaway estimated that only a half dozen of the 200 lake residents were still there when the evacuation was advised.
In Missouri, authorities said water — some from recent rain — began pouring over levees Saturday night and Sunday morning in Holt and Atchison counties, flooding farmland and numerous homes and cabins.
A hole in the side of a Holt County levee continued to grow Sunday, deluging the state park and recreational area of Big Lake, a community of fewer than 200 people located 78 miles north of Kansas City and just across the river from Rulo.
Holt County Commissioner Mark Sitherwood said U.S. 159 was closed south of Big Lake because water was pouring over the road, and most of the west side of the community was flooded.
“It's going through in one place that we know of and overtopped in numerous places, and there is seepage everywhere,” Sitherwood said.
World-Herald staff writer Rick Ruggles and the Associated Press contributed to this report.
Contact the writer: 402-444-1272, firstname.lastname@example.org