Jun. 25—MITCHELL — A historic rainstorm that pummeled Mitchell with 7.9 inches of rain in three days tested the city of Mitchell’s stormwater drainage system and critical infrastructure.

While a few areas were flooded with several feet of standing water during the peak of the storm on Thursday night and into Friday, Public Works Director Joe Schroeder said the city’s drainage system performed better than he anticipated considering the amount of rain that fell in a short time span.

“It performed better than I initially anticipated it was going to when it started coming down very hard,” Schroeder said of the city’s stormwater drainage system.

The storm brought back eerie flashbacks to the 2019 flood for Schroeder. A key difference Schroeder said he noticed with the recent storm was the amount of rain that fell in a shorter time span compared to what Mitchell saw in 2019 when almost 8 inches of rain fell over a three-day stretch. This time, a two-day record of 7.7 inches of rain fell in two days, according to the National Weather Service. The three-day total was 7.9 inches during this storm.

“I felt like the water came down much faster in a shorter period of time this time around, which puts a lot of stress on our drainage and infrastructure,” Schroeder said. “I think it’s fair to say it was well above a 100-year storm event.”

Schroeder said some residents he spoke with had rain gauges showing 4 to 6 inches of rain fell within 2 hours during the peak of the storm.

If 5 inches of rain falls within 2 hours in the Mitchell area, it would be classified by the National Oceanic and Atmospheric Administration (NOAA) as a 1,000-year storm event. In terms of probability, a 1,000-year flood has a 0.1% chance of happening in any given year, according to the U.S. Geological Survey.

Areas in Mitchell that have a history of flooding were hit hard by the storm, including East Hackberry Avenue, low-lying areas around Dry Run Creek and a residential neighborhood along Williams Avenue and Anderson Street on the west side of Mitchell.

Once again, the recent rainstorm wreaked havoc on businesses and homes along East Hackberry Avenue. Over 2 feet of standing water seeped into Klock Werks and TK Electric. The flooding caused basement walls to cave in at a few homes in the area.

Considering the area had a $3.7 million drainage improvement project finished in 2022, the latest flooding along East Hackberry Avenue and South Kimball Street was frustrating for some residents and business owners alike.

Patzer Woodworking is among the businesses in the area that’s no stranger to dealing with floods. Tom Patzer, owner of Patzer Woodworking, said the business saw much less damage and standing water inside the building during the recent storm compared to the 2019 flood.

Patzer had high hopes the stormwater drainage system in the low-lying area would perform much better than it had in previous years following the completion of the drainage improvement project.

Despite being hit with another round of major flooding, city officials said the standing water that temporarily submerged the East Hackberry Avenue area drained quicker than it did during the 2019 flood.

The city’s wastewater treatment plant was being pushed to keep up with a constant flow of wastewater throughout the two-day flood. Schroeder said the wastewater treatment plant performed well and managed to hold steady without any water restrictions being imposed.

The creek that stretches near the city’s wastewater treatment plant caused temporary flooding on the road used to access the plant.

“We just had a little issue with the road going to the wastewater treatment plant due to flood water going across the road. We were able to mitigate the issue and access the wastewater treatment plant,” he said.

The widespread flooding stressed dams in neighboring states and caused a partial failure to a vital dam in Mankato, Minnesota. On Monday, the Rapidan Dam in Mankato was declared to be in imminent failure condition due to rising river water and debris piling.

Lake Mitchell’s spillway dam held strong throughout the storm event, Mayor Bob Everson said.

During the peak of the rainstorm, Lake Mitchell’s water levels drastically rose. By Friday morning, beaches were covered in water, public boat docks were submerged and water was creeping onto several lakefront properties.

The city imposed a no wake zone for the entire lake on Friday when water levels measured as high as 3.5 feet above the spillway dam. The city imposes a no wake zone on the lake when water levels measure 1 foot above the spillway.

City Administrator Stephanie Ellwein said the no wake zone restriction for Lake Mitchell is estimated to remain in effect until the end of this week, pending no additional significant precipitation adding to the water levels.