Are We Ready? What would happen if a 500-year storm hit Chicago
Loop North News


(Above) Texas National Guardsmen rescue a Houston resident by boat during flooding caused by Hurricane Harvey. Army National Guard photo by Lt. Zachary West. (Click on images to view larger versions.)

What if a Harvey or Irma-like storm pummeled Chicago? The president of Metropolitan Water Reclamation District of Greater Chicago makes some predictions about what this will be like when it happens.

4-Oct-17 – We are a few weeks removed from the onset of three intense hurricanes that hit American soil, and while we are months – even years – away from comprehending the true level of destruction they leveled, the picture coming into focus is one of utter devastation.

Chicago has had its share of storms, but we have benefited from our geographical location to avoid anything near comparison to what our neighbors on the coasts have experienced. The record rainfall for O’Hare in a 24-hour period is 9.35 inches. Harvey dumped a record-setting 50-plus inches in some places. The wettest year on record in Chicago is 2008 when 50.86 inches of rain fell. But the question should be asked: What if a Harvey or Irma-like storm pummeled Chicago?

A National Weather Service study suggests that such an event would mean that Millennium Park and the Loop would be swamped with four to five feet of water. Runways at both major Chicago airports would be flooded with four to five feet of water, too. Games at Wrigley Field would have to be postponed until their four feet of water could be removed. Guaranteed Rate Field would see similar flooding. Edgebrook Golf Course would be one very large water hole with nearly six feet of standing water. And up in Rogers Park, Loyola Beach would be swamped five and a half feet deep.

At a time when we are rapidly approaching the daunting intersection of environmental responsibility, scientific evidence, and economic investment decisions, it is a question that we need to ask sooner than later.

Photo by Steven Dahlman (Left) MWRD boat on Chicago River on August 9, 2012. Photo by Steven Dahlman.

Overall, it is estimated that over 20 trillion gallons of water fell on Texas. In Harris County alone, over 500 square miles were under water. Combined, there have been at least 100 fatalities reported that were related to the two storms. In Texas, 30,000 people have been permanently displaced from their homes. In Florida, 6.5 million people were evacuated. In Texas alone, experts are estimating up to $75 billion in economic costs related to the storm in what is being called a many-year recovery.

The Metropolitan Water Reclamation District of Greater Chicago is constantly monitoring weather patterns, so any major storm would not hit us by surprise. Our engineers have multiple tools to prepare our system for intense rainfall. First, they begin drawing the river system down to the absolute minimum elevation four feet below lake level. This allows for maximum retention in our waterways.

Next, our seven treatment plants go into maximum production. Pumps located 30 feet below the ground start draining sewers throughout the county, again providing as much space to hold and convey storm water in our system. This would include emptying our Deep Tunnel – a system of 109 miles of 30-feet-diameter pipe which can hold two billion gallons of water – and our three reservoirs, which currently can hold approximately ten billion more gallons.

(Right) McCook Reservoir, under construction in Summit, Illinois, about 14 miles southwest of the Loop. Photo by Steven Dahlman. Photo by Steven Dahlman

When the storm hits, the system won’t take long to fill. In addition to maximizing our plants, tunnels, and reservoirs, MWRD would begin pumping storm water directly into the Ship and Sanitary Canal. In extreme cases, with both the discharge and the rainfall increasing elevation on the river system, locks are opened to relieve water into Lake Michigan and save downtown Chicago from being completely under water.

The lake, with its vast dimensions, would not be in any danger of overflowing, but with wind speeds nearing 100 miles per hour, depending on its direction, giant waves could crash onto Lake Shore Drive, as we have seen before.

The largest issue, as we see in any rain event, is conveyance. Local sewers simply cannot carry water fast enough to move it into the MWRD system. Imagine draining a swimming pool with a straw. The analogy shows the difference between the amounts of water we would receive in a 500-year storm and the size of the pipes used to drain it. With double-digit rainfall, nearly the entire county would be plagued with flooded streets and basement backups. In addition to sewer backups and slow draining water, much of Cook County – particularly the suburban areas surrounding Chicago – would experience significant overbank flooding.

Metropolitan Water Reclamation District of Greater Chicago

(Above) A $61 million ultraviolet disinfection system at the MWRD’s Terrence J. O’Brien Water Reclamation Plant, located about 12 miles north of the Loop in Skokie. The plant serves more than 1.3 million people residing in a 143-square-mile area that includes Chicago north of Fullerton Avenue. It cleans an average of 230 million gallons of wastewater per day. (Photo obtained from Metropolitan Water Reclamation District of Greater Chicago.)

In all, the Cook County region would experience over $200 million worth of damage, with economic loss in the billions. It would be a devastating event with far-reaching consequences. The district has done a lot to prepare for intense rain events, but nearly every year, some area of the county suffers flooding due to intense rainfall.

The truth is that we can never be fully prepared for catastrophic storms. But with smart investment, we can help to reduce the effects of those storms on the residents of Cook County. We need to look at our undersized and outdated infrastructure. Sewers built a hundred years ago cannot convey large amounts of water fast enough.

Given the unreliability of our aging infrastructure, it is important for us to find more creative ways to capture storm water before it enters our system. This is where green infrastructure comes in. Rain gardens, permeable pavement, rain barrels, green roofs. While individually these technologies have minimal impact, when implemented on a wide scale they can act as additional means of water detention and drainage.

Development is essential to our economic growth, but simply paving over our greenspace with concrete and asphalt eliminates the porous areas of Cook County that absorbs rain water.

Photo by Steven Dahlman (Left) Mariyana Spyropoulos speaks at an event hosted by Friends of the Chicago River on March 31. Photo by Steven Dahlman.

Unlike Houston, the district enacted the Water Management Ordinance in 2013. It mandates developers to take runoff and detention into account when building. We need to continue to engage the business community to do their part to protect against intense flooding.

Finally, we have the responsibility to operate in a manner that reduces the effects of climate change. That means being smarter about enacting policies and regulations that protect our environment. The bottom line is that it’s no longer a question of if a 500-year storm is coming to Chicago, but rather when. Will we be ready?

Mariyana Spyropoulos is president of Metropolitan Water Reclamation District of Greater Chicago. The MWRD manages storm water and water treatment for an 883-square-mile area of Cook County that includes the entrance to the Chicago River from Lake Michigan at the Chicago River Controlling Works.

By Mariyana Spyropoulos | Metropolitan Water Reclamation District |

Published 4-Oct-17 3:19 PM

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