Exactly 15 years ago today, Chicagoans were in the midst of one of the worst disasters in the city’s history. It was a massive flood that swept through the basements and sub-basements of many of the city’s most prominent downtown buildings. It shut down power, the CTA and much of the Loop.

No one died, but when it was all over 6 weeks later, the total damage caused was estimated at nearly 1 billion dollars.

Today on 848, we’re looking back on the Great Chicago Flood of 1992.

It started innocuously enough on the morning of Monday, April 13th. Early that day, a maintenance engineer at the Merchandise Mart noticed a few inches of water covering the basement floor. He called 911 to report the leak. But no one knew the source – or the full extent – of the problem.

At the time, CTA employee Bruce Moffat was on his way to work at the Mart…

[Bruce Moffat tape]

The tunnel actually refers to a 47 mile network of tunnels that maze underneath the Chicago River and flow through most of downtown. A hole in one of them near the Kinzie Street drawbridge allowed hundreds of millions of gallons of water to go rushing through.

The tunnels connect to old, vintage office buildings and soon the water levels in their basements began to rise. The water rose from just a few inches to more than 20 feet in just a matter of hours. And as the workday started, building managers grew worried…

[Archival audio]

The waters also raised questions about the health and safety of the public. So Chicago Mayor Richard Daley and Fire Commissioner Raymond Orozco decided to act…

[Archival audio]

And so a massive evacuation of the loop began. Hundreds of thousands of workers came streaming out of high rise buildings and were sent home for the day. Ira Glass reported on that aspect of American Life for NPR News:

[Archival audio]

As emergency workers were evacuating employees from their office buildings, reporters at City Hall were pressing Mayor Daley for answers…

[Archival audio]

It was later revealed that a company hired to replace the pilings at the Kinzie Street Bridge had inadvertently cracked a hole in the tunnel wall below. City workers knew about the breach, but didn’t move quickly enough to replace it in time.

As the waters continued to rise downtown, word of Chicago’s underground flood began to spread to the national news media. By the end of the day on Monday April13th, it was the lead story on NPR’s All Things Considered.

[Archival audio]

Engineers eventually plugged the hole to stop the flow of water. But that wasn’t the end of the crisis. The water in the buildings and the rest of the tunnel system had to be slowly pumped out and diverted into the Deep Tunnel.

The process was painstakingly slow and took weeks to get the Loop back to normal. 

It’s been 15 years since the Great Chicago Flood, but you can still see evidence of it on the walls beneath City Hall

[Bruce Moffat tape]

Bruce Moffat wrote about the 1992 flood in his book The Chicago Tunnel Story. He’s an historian and an expert on the Chicago Tunnel System. And he says to understand the flood, you have to understand the infrastructure that made it possible…

[Bruce Moffat tape]

The Chicago Tunnel Company closed up its operations in 1959. And for decades thereafter, only a few city workers and utility companies gave much thought to the underground passageways. But the 1992 flood changed all of that.

Since then, the City of Chicago has made a number of improvements to the system. They’ve built concrete bulkheads, installed an electronic monitoring system and now inspect the tunnel on an annual basis.

Even though the Chicago Tunnel System caused major headaches and millions of dollars in damages on that April day 15 years ago, Moffat says it remains a unique and important asset for the city…

[Bruce Moffat tape]

Bruce Moffat is the author of the Chicago Tunnel Story: Exploring the Railroad “Forty-Feet Below.” 

Click here to see pictures of our journey into the City Hall sub-basement.

(Photos by Steve Edwards)