Sandbags weighing 1,000 pounds each and dumped by helicopter have delayed the full breach of a Missouri River levee, providing some time to build a secondary wall to protect the town of Hamburg, the Army Corps of Engineers said Monday.
The Iowa National Guard dropped 22 huge sandbags "to help fill that breach, but that is just going to delay the full breach," said corps spokeswoman Monique Farmer.
It will take about a week to raise a secondary flood protection for Hamburg by five feet to reduce the risk for the town from the full breach, Farmer said.
The earthen levee, which guards an area of farmland and small towns between Omaha, Neb., and Kansas City, was partially breached over the weekend in at least two places south of Iowa's border with Missouri.
"We anticipate these compromises rearing their ugly heads all up and down the levee system throughout this event," Rhonda Wiley, the emergency management director for Missouri's Atchison County, said Sunday. "It's not a pretty picture."
The corps has predicted record flows along the Missouri River and large releases from several upstream reservoirs because of steady spring rain and runoff from record snowpack.
The corps reported the first partial breach in the levee in Atchison County — a hole 1 inch to 1½ inches in diameter — on Sunday. Atchison County officials said the first break did not constitute a full breach because of its size, and called it instead, a "compromise."
Authorities ordered 600 residents of Hamburg, Iowa — nearly half the town — to evacuate their homes on Sunday after the first breach was discovered. The residents were told to get out within 24 hours.
"People's safety is our number one concern, so we want to stress how important it is for the public to stay off of these levees as we continue to assess the risk," said the corps' Omaha District Commander Col. Bob Ruch.
"We acknowledge the frustrations of the affected communities, and we are committed to working together to avoid the loss of life and minimize damages," said Ruch.
He said the corps has been working to raise the levee near Hamburg an additional five feet to help protect the town.
Officials are also concerned about a section of a levee near Brownville, Neb., and crews are trying to determine the extent of possible damage there, the corps said Monday.
In South Dakota, the Army Corps of Engineers began construction of a backup levee Sunday to protect the town of Dakota Dunes. Corps engineer LeeJay Templeton said the 1.4-mile long secondary levee is slated to be completed by Thursday.
The Missouri River was expected to rise about 8 feet to 1,098 feet above sea level by June 14 in the town of about 2,500 people, some of whom have evacuated ahead of the planned crest. Officials said construction of the primary levee is still under way to protect the town 2 feet beyond the projected high level.
Pressure on the earthen berms upriver in Pierre and Fort Pierre, S.D. — and the anxiety of area residents — will continue to increase through Tuesday, when the water being released at a dam just above the two towns reaches its peak of 150,000 cubic feet per second, nearly double the 85,000 cubic feet per second being released last week.
On Sunday, the U.S. Army Corps of Engineers said the dam was dumping 130,000 cubic feet of water per second into the Missouri, whose waters have already risen more than a foot over the past week.
Officials in South Dakota have not yet ordered mandatory evacuations in the state. But as many as 3,000 Pierre and Fort Pierre residents, and more than 800 of the 1,100 homes over 250 miles away in Dakota Dunes, are threatened.
So far, the releases from the Oahe Dam have raised water levels along the Missouri in the state more than a foot.
"All the levees are holding at this hour," said Nathan Sanderson, spokesman for the Southeast Incident Management Team, which is warily watching the creeping floodwaters in Dakota Dunes in the extreme southeastern part of the state.