Flooded basements in Chicago are increasingly common. What you can do.

By Chicago 20 Min Read

Chicago was built along a maze of rivers and marshy wetlands. Flooding has been an issue since Day 1.

Engineers have dreamed up big, ambitious schemes to keep the water confined to our rivers and lakes and out of our streets and homes. They raised buildings to lay the original sewer pipes, reversed the flow of the Chicago River to protect our source of drinking water and in 1975 began construction of the Deep Tunnel — formally known as the Tunnel and Reservoir Plan, or TARP — to capture excess water during heavy rains.

And still we flood.

The sewer system gets overwhelmed after just two-thirds of an inch of rainfall in an hour, according to the Metropolitan Water Reclamation District of Greater Chicago, the government agency responsible for managing stormwater and cleaning wastewater in Cook County.

It’s an all-too-familiar scene: Chicago gets hit with fast, heavy rain, then the city is left with sewage backup and flooded basements.

But why does this happen so often? And what can be done about it?

Here are answers to some common questions about flooding in Chicago and information to help protect your home, your communities, waterways and the city.

Why does sewage get into basements?

Most of Chicago’s sewer system was built before 1930. As in many older cities, Chicago has a combined sewer system. That means any rain or runoff that runs into streets goes into the same pipes as anything we flush down a toilet or pour down a drain.

In dry weather, that works fine. When it pours, though, there’s too much water heading into those pipes at the same time, and it creates a kind of gridlock.

Patrick Jensen, a senior civil engineer for the water reclamation district, says it’s a lot like pouring a giant pail of water into a small kitchen sink.

“That sink is going to overflow not necessarily because the drain isn’t working,” Jensen says. “It simply cannot handle that flow in that fast amount of time to prevent it from over-topping.”

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When that happens, pressure builds in the pipes, pushing in every direction, including backwards — and into basements. Any water flushed down the toilet or drain also has a hard time leaving and is likely to back up into the house.

Beyond the design of the sewer system, there are two key reasons this is happening more in recent years: First, the area’s built environment has covered up most of the grass and soil that might otherwise absorb stormwater into the ground. Second, heavy storms are happening more often — and that’s expected to become the norm as the climate continues to change.

Wasn’t the Deep Tunnel supposed to stop flooding?

Construction of the Deep Tunnel began almost 50 years ago. It’s designed to provide a holding place for excess water when the sewer system is overwhelmed. It consists of 110 miles of giant tunnels below sewer systems throughout Cook County, ready to carry excess water to one of three massive reservoirs, where it is held until the water-treatment plants can catch up.

The reservoirs can hold more than 11 billion gallons. Still, in July, one of them — the McCook Reservoir — reached capacity. To increase that capacity by 6.5 billion gallons, crews are blasting through rock and creating a fourth reservoir, set to be finished by 2029.

But here’s the catch: Though the Deep Tunnel helps hold excess water, it’s up to municipalities to get the water from their sewer systems into the tunnels. That means it’s the responsibility of the city of Chicago Department of Water Management and its suburban counterparts to keep their sewers clear and functional.

“And that’s the biggest problem we have,” says Dick Lanyon, retired executive director of the water reclamation district. “The sewers have to be maintained, periodically inspected by closed circuit TV cameras, cleaned. Any failures have to be repaired.”

Things like leaves and debris can block pipes, and sometimes they cave in after years of use. The agency’s top engineer says the rule of thumb is to inspect sewer lines every five years or so, depending how often an area experiences problems. But Matt Quinn, deputy managing commission of the city’s Department of Water Management, says his crews make their way through each neighborhood about once every 10 to 15 years.

They also respond to problems when people file complaints and inspection requests with 311.

The agency doesn’t keep centralized records of when and where it inspects sewer mains and structures, so it’s hard to know how often they’re checked.

Does opening locks reduce basement flooding?

The Chicago Harbor Lock is located near Navy Pier between Lake Michigan and the mouth of the Chicago River. During heavy storms, the water reclamation district can open gates at the lock after the river rises above the level of the lake to reduce flooding along the river banks by temporarily letting water flow towards the lake.

But doing that pollutes Lake Michigan, our source of drinking water.

It also doesn’t actually do anything to reduce basement flooding, according to Lanyon.

“Even if you could open the locks earlier,” he says, “the water has to go such a distance to get to the lakefront — and through all the sewers and canals — that [it’s] not a solution at all.”

So extraordinary rains overwhelm the city’s system regardless of whether the gates and lock are open.

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What’s government doing to deal with this?

There are two main agencies responsible for the sewer system in Chicago and the surrounding area. The water reclamation district is the regional stormwater-management authority that cleans wastewater and releases it back into waterways. And City Hall’s water management department manages about 4,500 miles of sewer pipes running under streets and delivers drinking water to Chicagoans.

The two agencies have several initiatives aimed at improving the function of and reducing pressure on the system during heavy rains.

Replace and repair sewer mains: In the past decade, the city has lined or replaced more than 750 miles of sewer mains as part of an infrastructure improvement project that kicked off during former Mayor Rahm Emanuel’s administration. But that accounts for just 17% of the system. The work will continue based on funding, prioritizing older sewer lines and those that modeling suggests might be problem areas, often because they are too narrow for modern rains.

Install water restricter valves: Restricter valves, or rain blockers, attach to storm drains and act as funnels, controlling the flow of water into sewers during rains. The city has installed these on most Chicago streets — basically acting as temporary retention pools when sewer mains are overwhelmed. According to the agency, Water in the street is better than water in the basement. But people don’t always see it that way and sometimes remove the valves to avoid having flooded streets.

Create green infrastructure: In the past decade, the city agency has worked with the water reclamation district, the Chicago Public Schools and others to rip up large swaths of impervious pavement on more than 30 schoolyards and replace them with permeable pavement, vegetation and other stormwater-retention features. The district also has invested heavily in green infrastructure and rainwater management. In partnership with municipalities, it has more than 220 green infrastructure and flood-resiliency projects in some phase of planning or construction as part of its Green Infrastructure Partnership Program.

Increase capacity: Commissioner Andrea Cheng says the city agency also is designing and seeking funding for more large-scale tunnels to help get Chicago’s sewer and stormwater to the Deep Tunnel system more quickly, thought the timeline for that is unclear.

Educate people and provide resources: The water reclamation district has a number of resources available for homeowners to learn about protecting their home and reducing their contribution to regional flooding problems. The agency also sells and delivers discounted rain barrels to Cook County residents.

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What more could the city do?

Over the years, city officials have had several to try to tackle this, including former Mayor Richard M. Daley’s plan for Green Urban Design and Climate Action Plan, Emmanuel’s Green Stormwater Infrastructure Strategy and former Mayor Lori Lightfoot’s Climate Action Plan. But none of those plans was executed in a comprehensive way.

Other cities, though, have come up with plans that might provide a model:

Create a centralized plan: Milwaukee has made really clear plans, has a clear vision and has put in place millions of gallons worth of stormwater storage with green infrastructure, says Nicole Chavas, president of Greenprint Partners, a sustainable planning and engineering firm in Chicago. That city’s Environmental Collaboration Office acts as a hub for promoting and coordinating sustainability efforts across government agencies and communities. Chicago’s Department of the Environment, with a similar mandate, was dismantled by Emanuel in 2012 — though Mayor Brandon Johnson has proposed re-establishing such an agency.

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Provide government assistance for flood mitigation: Several suburban communities — including Oak Park, Morton Grove and Wheaton — offer rebates, cost-sharing or grants to help install flood-mitigation retrofits, such as check valves, overhead sewer lines or even green infrastructure. I do think that a lot of the federal funding that’s coming down the pipe is eligible and could be used to implement grant programs to support homeowners, Chavas says.

Send emergency alerts during heavy rains: Rachel Havrelock, a professor at the University of Illinois Chicago’s Fresh Water Lab, says the region should have mass alert notifications that encourage people to adjust their behavior during heavy rains. The water reclamation district has an opt-in text notification, but Havrelock says these ought to be similar to the air-quality alerts that were impossible to ignore this past summer. People need to hold their household water use when it is raining, she said at a recent City Council hearing. Anybody in an area that’s flooding, their phone should light and buzz … in conjunction with billboards [and] public service announcements for people to begin to understand that any water put into the system during a rain event can resurface in your household. 

How can I keep water out of my basement?

Homeowners have a few options to reduce the likelihood of sewage backing up into basements during heavy rains, particularly for older buildings. (Here are some resources for renters whose apartments flood.) These tend to be costly — and, because they result in more pressure on the system, make things worse for others on your block who don’t have flood-control mechanisms. Still, when faced with a flooded basement, those who can afford to might install upgrades. Some popular options:

Install a check valve: Check or backflow valves are installed into the private sewer pipe, usually by digging a pit in the front yard, to make sure wastewater can flow only out and can’t back up from the public main.

Cost: Typically $5,000 to $8,000.

Caveats: In a heavy storm, a check valve might not be able to allow any sewage to leave the home, meaning you have to be careful not to flush or pour anything down your pipes. They also require regular inspections to make sure they don’t get stuck.

Construct an overhead sewer line: This is a major reconstruction of your plumbing system that pumps wastewater from basement facilities — like your washer and any bathroom in a basement — to a pipe in the basement ceiling or first floor and from there out of the house. The higher elevation means it’s less likely your pipes will back up, unless flooding outside reaches above the level of the pipe.

Cost: Between $15,000 and $25,000.

Caveats: The cost.

Use a standpipe: A standpipe is basically a big PVC pipe that is sealed to the sewer drain in the floor. It raises the lowest drain opening in the home to a level higher than the sewer, making sewage backups into the home less likely.

Cost: About $30.

Caveats: This is only useful when all you’re getting is a small amount of backflow coming from the floor drain. Otherwise, water will likely find its way in through other openings in the home. And sometimes the seals crack and need to be replaced.

Such projects only help prevent sewage backups. If you also experience seepage during heavy rains, you might explore installing drain tiles, waterproofing or sealing cracks in the foundation.

In Chicago, you also can ask the city to inspect your sewer if you suspect a larger problem.

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How can I reduce pressure on the sewer system?

These small-to-medium lifts can greatly reduce your contribution to the sewers during heavy rains. They include:

Disconnect downspouts: Chicago’s city code used to require downspouts carrying water from roofs to feed directly into the sewer, which added pressure to the system during heavy rains. According to the water reclamation district, a house with a roof that’s 800 square feet can send about 500 gallons of water to sewers during a one-inch storm. When the system gets overwhelmed, that water can come right back into your home. A guide from the water reclamation district can help you tackle the project.

Plant a rain garden — or, at least, native plants: Native plants provide benefits to ecosystems and soak up water from your yard or rain garden. A guide from the water reclamation district can tell you more about native plants that are particularly adept at thriving in wet environments and returning stormwater to the ground.

Install a rain barrel: A rain barrel placed under a modified downspout can reduce your utility bill and help decrease the amount of stormwater going to sewers. The water reclamation district sells rain barrels at a discount and has guidance for how to install and maintain them. Pro tip: Empty it before a first winter freeze, and store it inside till spring.

Replace concrete and asphalt with permeable pavement: Unlike traditional paving that often directs stormwater into the sewer, permeable paving lets water absorb into the ground.

Have your sewer line checked: The privately owned sewer pipes from your home or building to the main under a street can cause problems if there are tree roots, grease or other blockages preventing wastewater from leaving the house. You also might have problems if cracks or connections to other pipes are letting in additional water and causing them to exceed their capacity. Periodic private inspections from a certified plumber can help identify and fix problems.

File a request with 311: In Chicago, if you get water in your basement or suspect a problem with your sewer line, notify the city online or by calling 311. This helps identify problem areas, measure the extent of the problem and plan future projects.

Other resources that might help include the water reclamation district’s Green Neighbor Guide, its Overflow Action Day text alerts and the Center for Neighborhood Technology’s RainReady Homeowner Guidance.

  • 25 years on, the soggy story of the Loop Flood lingers
WBEZ Curious City

This story originally appeared on WBEZ’s Curious City, a podcast that answers questions about Chicago and the region.

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