While the barrier held fast, authorities planned to keep a cautious eye on the continuing downpour overnight.
The Washington County, Ill., Emergency Management Agency warned residents shortly before 9 a.m. that the Nashville City Reservoir Dam was at immediate risk of "failure" as floodwaters began to overtop it.
About 200 people fled their homes as a result, officials said. Rising waters also closed roadways to the south, north and east of Nashville — including an 11-mile stretch of Interstate 64.
More rain was expected to hit the area in the coming hours.
Alex Haglund, the public information officer for the Washington County Emergency Management Agency, said the danger is no longer imminent, as residents have been evacuated.
“As of right now, the immediate danger has passed,” Haglund said. “The danger we’re dealing with is roadway danger.”
Tuesday's storms also caused localized flash flooding across the St. Louis region. The city received up to 6 inches of rainfall that shut down interstate highways and suburban roads and intersections, downed trees, and prompted complaints to the region’s sewer district about flooded roads and basement backups.
Parts of Interstate 70 in St. Charles County, Mo., Interstate 44 in west St. Louis County and Interstate 270 in north St. Louis County were all closed because of flooding.
In St. Louis' Midtown neighborhood, water flooded the basement of a St. Louis Fire Department engine house and inundated low-lying neighborhood roads. And in Warren County, the towns of Marthasville and Treloar along the Katy Trail were fully submerged in water, according to the Marthasville Fire Protection District.
The heaviest rainfall was in the region’s south and southeast; parts of St. Clair County received as much as 5 to 6 inches of rain and parts of south St. Louis County and Jefferson County received as much as 4 to 5 inches.
In University City, the upper River Des Peres, already high with backup from the Mississippi River, rose to its banks but narrowly avoided overflowing, said Bob Criss, a Washington University flood expert and University City resident. The river is a trouble spot for flash flooding during summer storms.
“It was as close as we would want to get,” Criss said.
Between 2 and 6 inches of rain had fallen in the St. Louis region as of about 12:45 p.m. and more was expected, according to the National Weather Service.
Despite the heavy rains and flooding, authorities did not immediately report injuries or deaths in the St. Louis region or Nashville, Illinois, a city of 3,000 residents about 55 miles east of St. Louis. At least one woman was trapped in her home in waist-deep water, said Alex Haglund, public information officer for Washington County Emergency Management Agency.
While officials warned Nashville residents that the dam was at imminent risk of failing, it remained structurally sound as of Tuesday evening, Haglung said. Water flowing over the top of an earthen dam can lead to rapid erosion and dam failure, according to Association of Dam Safety Officials.
All dams built in Illinois are equipped with emergency spillways when water exceeds a dam's maximum capacity. Loren Wobig, the director of the office of water resources in Illinois, said the county's Tuesday morning announcement of imminent "failure" from the county was too harsh.
“To say it failed is a misstatement,” Wobig said. “Is our roadway flooded? Absolutely. But that’s where the water was intended to go.”
I-64 in Washington County, Ill., was closed in both directions between exits 50 and 61, the National Weather Service office said.
Christy Jackson was driving her sedan along I-64 with water so deep she estimated it was along the bottom edge of her car door.
"I was afraid the whole time going through," Jackson said. "I was shook up."
Jackson, of Centralia, works at a manufacturing plant in Nashville. The company lost power Tuesday morning, and workers were told to go home. Jackson got on I-64 from Highway 127 in Nashville and headed toward the Centralia exit. She came around a curve, she said, and saw traffic at a standstill. She said there was no place to pull off the road.
She traveled about a quarter-mile in the high waters, she said. About 75 vehicles were having the same trouble.
The I-57 on-ramp near Marion, Ill., was flooded and impassable. About five inches of rainwater was drenching the streets near Nashville, and sewers were backing up.
Shelley Harper, who lives just outside Nashville city limits, spent much of Tuesday trapped in her home because of flooded streets.
"I think this is the worst I’ve seen it, and I’m 68," Harper said by phone. "The conditions were just right (for flooding).”
Nashville resident Cheyenne Nowakowski fled her home with her 2-year-old son shortly after 9 a.m. after learning of evacuation warning. She spent most of the day at the Trinity St. John School gymnasium, one of the city's designated evacuation sites.
Haglund said similar evacuations were ordered about two years ago downstream in the flood area. Tuesday's evacuations are proving more complicated, he said, because of the road closures.
Wobig said as rain continues to fall, the dam will continue to expel water from its spillways, given that it continues to function effectively. However, he said the dam was designed to function with emergency spillways.
“The IDNR inspected the bridge in November of 2023, and said it was perfectly fine,” Woebig said.
Haglund said there have been no injuries or deaths, despite the flooding and destruction to infrastructure.
“The flooding is not good,” Haglund said. “But it’s not a whole town being washed away by a tidal wave.”
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