“Chicago Is Building a Pair of Underground Reservoirs to Ease West Side Flooding,” WTTW Channel 11

Breadcrumb

1. Home
2. News
3. "Chicago Is Building a Pair of Underground Reservoirs to Ease West Side Flooding," WTTW Channel 11

The Chicago region's Tunnel and Reservoir Plan (TARP), aka the Deep Tunnel system, can hold billions of gallons of water during extreme weather events. Following a 48-hour period of near biblical rain between July 2 and July 4, TARP's reservoirs were all but maxed out, reaching unprecedented levels.

Is that a problem?

"TARP is doing exactly what it was designed to," said Kari Steele, president of the board of commissioners of the Metropolitan Water Reclamation District of Greater Chicago, which operates the Deep Tunnel. "We're keeping water out of basements."

But even the Deep Tunnel and its reservoirs have their limits. One constraint of the system: TARP's big pipes are paired with Chicago's 100-plus-year-old sewer pipes, which weren't designed for 21st century storms - when a month's worth of rain falls in a day - or for a 21st century asphalt jungle.

"Since these were originally built, you've paved over everything in the city, it's become more developed, more dense, so the existing sewer system just doesn't have the capacity to handle these larger storm events that we've gotten in recent years," said Justin Kirk, an engineer with MWRD, specializing in stormwater management.

"Obviously if you were going to build a new city from scratch today, you'd use larger sewers," Kirk said.

Hitting the re-set button isn't an option. Instead, MWRD and Chicago's Department of Water Management came up with an innovative retrofit for a part of the city hit hard by previous storms.

On Tuesday, local officials gathered on a West Side street in Austin to announce a targeted stormwater mitigation pilot project developed in response to severe flooding that devastated the community in 2023, also over the Independence Day holiday.

In partnership with MWRD, which is providing up to $6 million of the $12 million price tag, the city of Chicago is constructing two underground storage tanks, with a combined capacity of 1.7 million gallons of water. During extreme rains, these tanks - akin to mini-reservoirs - will hold water that would otherwise overwhelm the city's sewers and back up into homes.

"It provides additional volume for the sewers to have a little more time to drain during these short, intense rain events," Kirk said.

The water will be contained until the sewer is able to accommodate it, and then it will slowly move into the sewer to be sent to an MWRD treatment plant.

The tanks - or "box culverts" as Kirk calls them - consist of approximately 50, 12-foot by 12-foot concrete boxes positioned side by side under the street, running the length of half a block, or roughly 330 feet. The effect is something like a cross between a Lego and a Minecraft cube.

The first tank has already been completed on Maypole Avenue, between Cicero and Lavergne avenues. The second is under construction on LeMoyne Street, between Luna and Lorel avenues, with an expected completion date sometime this fall. Officials will spend the next six to nine months assessing the tanks' performance.

Once both are operational, they're expected to provide flood protection to more than 2,900 homes and businesses in the neighborhoods of North and South Austin, West Garfield Park and Galewood.

The project should offer relief to residents who have been dealing with uncertainty, property damage and loss, and ongoing disruption, Chicago Mayor Brandon Johnson said.

"We are delivering the peace of mind that every Chicagoan deserves when severe weather is on the way," Johnson said.

A new stormwater reservoir under construction on West LeMoyne Street on Chicago's West Side. (Patty Wetli / WTTW News)

Though the way the tanks function is fairly basic, implementing the solution has been anything but, said Randy Conner, commissioner of Chicago's Department of Water Management.

"Adding infrastructure in dense urban neighborhoods is like putting pieces of a puzzle together. … Sometimes it's a 10-piece puzzle that can be figured out in no time, but oftentimes it's a 1,000-piece puzzle that has to be assembled strategically," Conner said during a news conference Tuesday. "That's what we have done here."

To identify locations for the pilot, the city had to search for places in flood-prone areas where there was room for the tanks, which meant finding streets that weren't already crisscrossed by a subterranean network of utility pipes. Maypole and LeMoyne fit the bill, but the size of the tanks and the prevalence of underground utilities may limit larger-scale implementation.

Conner acknowledged that when it comes to handling flooding, there's no silver bullet.

His department is drawing on a wide range of solutions including the use of new real-time sewer-flow monitoring technology, which will help the department track how water moves through the sewer system during storms.

The department is also planning a downspout disconnection pilot program, he said, and will be installing more rain-blocker devices on catch basins in strategic locations.

The blockers, which keep stormwater on the street when sewers are overwhelmed, can be controversial with residents, but Connor said that using streets for water retention is preferable to backups in people's homes and businesses.

On its end, MWRD is promoting green infrastructure projects along with gray infrastructure like the box tanks.

"It's always our first preference to let rain soak into the ground where it is before even sending it to the sewer system," Kirk said.

In partnership with Chicago Public Schools, MWRD has been transforming school playgrounds into permeable surfaces that can hold rainwater. And it's also worked with suburban municipalities on adding permeable pavement to parking lots, particularly those attached to government facilities like village halls or police stations, Kirk said.

"If we can plan proactively," Kirk said, "we can hopefully help prevent some of the destruction that we've seen in recent years from these intense rain events."

https://news.wttw.com/2026/07/07/chicago-building-pair-underground-reservoirs-ease-west-side-flooding