The V-shaped, 180-metre breach opened up just after 5am local time at a hydroelectric plant and in a matter of minutes the 20-hectare reservoir had emptied itself, turning the surrounding area into a landscape of flattened trees and clay-covered grass.
“We’ll never see anything like it in our lifetime again,” paramedic Chris Hoover said.
Gary Rainwater, the chaiman of St Louis-based energy company AmerenUE, which runs the plant, said the plant’s automated instruments had pumped too much water into the reservoir and caused it to rupture.
A backup set of instruments should have recognised the problem but didn’t, and the utility is trying to figure out why, AmerenUE said.
Trucker Greg Coleman was hauling a load of zinc when a wall of water emerged from the darkness and slammed into his truck near the Taum Sauk Lake Hydroelectric Plant.
The water hit Coleman’s truck, splashing through the windows.
He climbed onto the roof and saw that another truck and a car were also submerged, with the drivers also on the roofs. The water receded within minutes.
It was then that Coleman said he heard a man screaming for help.
The man’s home had been washed away. Badly bruised, he was clinging to a cedar tree while his young children held onto other trees. Rescue workers arrived and rescued the family.
The three children, aged seven months, three years old and five years, were listed in critical condition at a hospital in St Louis, 195 kilometres to the north east.
The two older children had breathing problems; the baby suffered from hypothermia, authorities said.
The reservoir, built in 1963, was dug out of the top of 477-metre Profit Mountain, with huge, sloping, 27-metre-high walls made of the stone removed from the peak.
The cause of the accident was under investigation by federal regulators and other authorities.