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Supercell Storm Dumped More Than 5 Inches Of Rain In Parts Of City: ‘No Combined Sewer System In World Could … Hold That Kind Of A Burst’

City officials defended the sewer system after the major rainfall, saying the storm's unusual speed and intensity were partially to blame for mass flooding.

A basement near Irving Park Road and Central Avenue in Portage Park floods during the "supercell" storm Sept. 11, 2022.
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CHICAGO — Nearly 2,000 North Side residents reported flooding in their basements after a “supercell” storm overwhelmed city sewers and created flash floods Sunday

More than 1,900 service requests were filed related to the storm by Monday afternoon, said Mary May, a spokesperson with the city’s Office of Emergency Management and Communications. About 1,600 involved flooded basements, about 300 involved water on the street and seven were connected to flooded viaducts, May said.

Yisrael Shapiro, a staffer with Ald. Debra Silverstein (50th), said the city’s water department told the ward office it had fielded about 2,000 reports of flooded basements among North Side residents. The West Ridge ward office received hundreds of calls Monday morning, Shapiro said.

“The phones are ringing off the hook,” Shapiro said.

Credit: Provided
A basement near Foster Avenue and Pulaski Road in North Mayfair floods, toppling a bag of wood chips.

The heaviest rain of the rain came around 8 a.m. Sunday, meteorologists said. With extremely low wind, the storm stalled over the North Side, dropping nearly 4 inches of rain in about two hours.

Shapiro and other North Side aldermanic representatives said most residents were dealing with 1-2 inches of flooding in their basement. Some residents reported more than 1 foot of standing water at certain points Sunday, they said.

City officials and aldermen say affected residents should file a ticket with 311 to report basement flooding. The filing should trigger a city official to visit the property to inspect home flooding, according to 311. 

‘This Was White Water Flying Up From The Drain’

Plumbers said Monday they received hundreds of service calls related to the storm.

Rae Lynn Piccioli, a co-owner of Power Plumbing in North Center, said the flooding happened for a variety of reasons, with water seeping through people’s foundations, doors and up basement drains.

“Even people that did have floor drains, flood control systems and ejector pumps … they still took in some water,” Piccioli said. “This was just kind of a very weird situation.” 

Emily Friend, who lives near Irving Park Road and Western Avenue, said she had about 6 inches of flooding. The water came up from her basement sewer drain and covered her home’s baseboards, she said.

That kind of flooding was unprecedented — but most of Friend’s block had similar experiences, she said. 

“Our house is 120, 130 years old, and we’ve had water seepage before from cracks in the foundation,” Friend said. “This was not seepage. This was white water flying up from the drain. There was way more accumulation. We’ve never had water get past our hallway.”

Friend said the water accumulated over a period of hours, then rapidly receded back into the drain. 

“It seemed like the city opened the drains or something, and all of a sudden it was gone,” Friend said. 

Residents along Berenice Avenue in Portage Park got 4 inches in their basements, one homeowner said. On Monday, Berenice neighbors between Major and Menard avenues received notices of an indefinite boil water order as precaution for water main work, according to a notice shared with Block Club. It was not immediately clear whether the flooding affected that.

Credit: Noah Asimow/Block Club Chicago
Flooding across Lincoln Square on after a “supercell” storm swept across the North Side on Sept. 11, 2022.

City officials defended the sewer system, blaming the flooding and infrastructure challenges on the severity of the storm.

Water department and the Metropolitan Water Reclamation District officials said the city’s complex sewer infrastructure functioned largely as it was supposed to during the storm Sunday, despite the basement flooding. 

A massive, interconnected network that carries storm runoff and wastewater, the city sewer system has an “inlet valve control system” that is designed to prevent rainwater from overwhelming sewer capacity and bubbling up through basement drains, officials said. During heavy rainfall, the streets are supposed to act as a catch basin, holding water until the system can relocate it to a reclamation facility or into its underground storage tunnels, known as TARP. 

Megan Vidis, a spokesperson with the city water department, said in a statement that “extreme rainfall events” like Sunday “require time for the sewer system to process.” She said the water department has installed the valves to prevent the kind of flooding Friend and others experienced, but the sewers can get overwhelmed nonetheless. 

“Basically, this was a supercell. There’s no combined sewer system in the world that could be designed to hold that kind of a burst,” Vidis said.

Allison Fore, a spokesman with the water reclamation district, said staff worked overnight to handle the rain and the city’s underground tunnel storage system was at about 80 percent capacity. She said “TARP was functioning as designed.”

The district’s “water reclamation plants and the [agency’s] Tunnel and Reservoir Plan (TARP), consisting of 110 miles of tunnels and three reservoirs, managed to keep up with the increased flow,” Fore said. “Despite several inches of rain, there is still capacity in the TARP system.”

Vidis and Fore pointed to the speed of the rainfall in explaining the flooding as the storm cut across a broad swath of the North Side. 

Matt Friedlein, a meteorologist with the National Weather Service, said West Ridge reported 4.25 inches of total rain, and Albany Park reported 5.63 inches, with 3.5 inches falling between 8:40-9:40 a.m., which is more akin to a tropical storm than typical rain events. Rainfall rates averaged about 2 inches per hour, but they rose to 4-8 inches per hour for a brief period of time in some North Side neighborhoods, he said. 

“One of the biggest keys of flash flooding is rainfall rate,” Friedlein said. “That was the key there in the morning yesterday.”

Credit: Provided
Floodwaters pour into a basement near Greenwood and Ellis avenues in Woodlawn during a Sept. 11, 2021 storm.

Piccioli and other plumbers said the city has seen significant residential development in recent years, which could increase the rain burden on older homes that don’t have modern flood control systems. 

Friend said she has neighbors who have lived on the block for 25 years and never experienced flooding like they did Sunday. But with severe storms becoming more common, the city shouldn’t expect residents to deal with basement flooding during every major rainfall event, she said.

“With climate change, we’re going to continue to experience these crazy storms and flash floods,” Friend said. “So is the solution that every time this happens, we’re gonna all just have to redo our basements? What’s the endgame here?”

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