Risk of Illinois dam breach is under control after once-in-a-century rainfall, officials say
(CNN) — After water overtopped a reservoir dam and forced residents of a small Illinois city to evacuate Tuesday morning amid fears the structure could rupture, local officials now say the situation is under control.
Extensive rain on Monday and Tuesday ran over the top of the dam and flooded downstream, which forced the evacuation of residents in Nashville, Illinois, said Alex Haglund, a spokesperson for the Washington County Sheriff’s Office.
“An estimated 200 residences were considered endanger and at risk of flooding,” Haglund said in a news release. First responders helped evacuate residents in the downstream area – some of whom reported waist-high water in their homes – including one woman who required a rescue, Haglund said.
“While the immediate danger to those downstream from the dam has been managed, there are still multiple road closures in the area,” the release stated, including on Interstate 64 between the Nashville and Ashley exits. Residents are encouraged to stay off the roads, if possible.
“Residents are allowed to return to the evacuated areas at this time, if they are comfortable doing so,” the Washington County Emergency Management Agency said in a Tuesday night Facebook post.
The agency said the US Army Corps of Engineers had assessed the reservoir for safety, noting, “The secondary dam reacted as designed, helping prevent a full dam failure. However, they did note that repairs to the Nashville IL Reservoir will be required, sooner rather than later, to maintain the integrity of the dam.”
Local officials had warned the rupture could happen at any moment.
“Attention the failure of the Nashville dam is imminent. Please evacuate your home at this time … you need evacuate now!” the emergency management agency said in a hasty Facebook post Tuesday morning.
Washington County was under a flash flood warning until 4:30 p.m. CT after the region received over 5 inches of rain in six hours, according to radar estimates from the National Weather Service office in St. Louis.
That level of rain approaches 100-year rainfall frequency – the type of downpour statistically likely to happen only once every century – according to weather records.
Extreme rainfall events like these are becoming more common, and they illustrate the effects of climate change. As the planet warms from fossil fuel pollution, the atmosphere is able to hold more moisture, which can then be released as intense rainfall.
After the heavy rain Tuesday morning, another round of heavy precipitation is possible for the region overnight, with a potential break in the heaviest rain later Tuesday afternoon and evening.
There have been no injuries or deaths due to this emergency.
Nashville – home to 3,105 people, according to the US Census Bureau – is in southeast Illinois, about 50 miles east of St. Louis.
On July 26, 2022, a secondary dam on the city reservoir was breached after over four inches of rain fell near Nashville in less than 12 hours, causing a 6-foot breach and flooding nearly 40 acres of land between Ashley, Illinois, and Nashville, according to Washington County records.
CNN has reached out to officials in Nashville and Washington County for updates.
This is a developing story and has been updated.
CNN’s Eric Zerkel, Christina Zdanowicz, Sara Smart and CNN meteorologist Brandon Miller contributed to this report
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