Rain caused ‘secondary failure’ of Nashville City Reservoir dam. What does that mean?

Heavy rain in southwestern Illinois on Tuesday caused what’s known as a “secondary failure” of the dam at the Nashville City Reservoir, allowing water to spill out and causing a portion of the town to be evacuated.

It’s what is designed to happen during emergencies, the Washington County Emergency Management Agency and the dam safety division of the Illinois Department of Natural Resources confirmed Tuesday morning.

Jayette Bolinski, spokeswoman for the state agency, said local emergency management officials are following their required emergency action plan for the dam and the safety of residents who live nearby.

“This dam was deliberately built so that when water rises it activates an emergency ‘fuse plug’ spillway and follows an emergency path,” Bolinski stated in an email to the Belleville News-Democrat.

The last time this happened was during the flash flooding in July 2022.

The Washington County Emergency Management Agency has been urging residents in a portion of town to evacuate because of the flooding. For some, water had already entered their houses.

Alex Haglund, spokesman for the local agency, said he knew of at least one woman who received help evacuating because her home had waist-high water.

“It’s not an enormous area, but it’s an enormous effect for the people in that area,” he said.

No injuries had been reported from the flooding as of 11 a.m., according to Haglund.

Local officials are asking residents to stay off the roads if they can and avoid driving over standing water to prevent injuries.