BISMARCK, N.D. — Demolition crews blasted chunks of ice near a huge ice jam in the Missouri River late Wednesday in a bid to open a channel, like pulling out a giant plug to drain a flood threatening the city.
"We are cautiously optimistic," Bismarck Mayor John Warford said after explosives detonated on about 500 feet of ice just south of the jam. He said officials would have a better assessment Wednesday night but that water appeared to be moving.
Water backing up behind the dam of car-size ice blocks already had forced the evacuation of about 1,700 people from low-lying areas in North Dakota's capital city.
On the eastern side of the state, volunteers continued stacking sandbags to protect Fargo from the rising Red River, as the city prepared to distribute evacuation route information.
The Missouri River jam, created by ice floating down the Heart River, was made up of chunks of ice up to 3 feet thick and the size of small cars, said Assistant Water Commission Engineer Todd Sando. It was about 11 miles downstream from the city.
"The ice is just solid as a rock," Sando said.
Crews from Advanced Explosives Demolition, with help from National Guard, the Army Corps of Engineers and the Coast Guard, drilled holes in the ice to detonate clay-like explosives.
A second ice jam about 18 kilometres upstream of Bismarck was also a concern, holding back a growing reservoir.
The National Weather Service posted a flash flood warning for a three-county area, saying the integrity of that ice jam, in an area called Double Ditch, was unpredictable.
"The fact that it could break at any time is bad news. But right now, the ice jam around the Double Ditch has not broken," Bismarck Mayor John Warford said at a morning news conference.
Residents of low-lying subdivisions in Bismarck and neighboring Mandan had been told to evacuate, and Fox Island residents Jane and Michael Pole didn't need much prodding. "We just grabbed a bag, threw some stuff in and left," Jane Pole said.
Some 320 kilometres east of Bismarck, officials also called for more sandbagging volunteers in Fargo, and its cross-river neighbor, Moorhead, Minn.
The Red River was projected to crest there at 41 feet Saturday afternoon, the weather service said in an updated forecast. The river had risen to 35.6 feet by midday Wednesday. The record at Fargo is 39.6 feet, set in 1997.
With that forecast, Fargo officials said they would raise their dikes a foot higher than planned, to 43 feet, and aimed to do it by Thursday afternoon.
"They're talking a 41-foot crest, and I don't care how old you are, you've never seen that in the valley," Mayor Dennis Walaker said.
Fargo officials planned to start distributing evacuation route information Thursday.
"Are we confident we're going to beat this?" Walaker said. "Yes, we are. But we need to have contingency plans in place."
More sandbagging was planned in part of Grand Forks, the city hardest hit by the 1997 Red River flood. An elaborate dike system was built after that disaster. The Red rose to 42.5 feet in Grand Forks by midday Wednesday with a crest near 52 feet projected for Monday. The record there was 54.4 feet, set in 1997.
- Associated Press