Flooding Update: Virtual Community Meeting, 8/29

On Sunday, July 17th, the southwest side experienced a significant rain storm. As a result, thousands of homes in the 19th Ward, Oak Lawn, Evergreen Park, Hometown, and Blue Island experienced flooding problems. Following the storm, Alderman O’Shea asked the Department of Water Management (DWM) and Metropolitan Water Reclamation District (MWRD) to conduct an investigation of the storm to identify factors that contributed to residential flooding. On Monday, August 29th, at 7:00 pm both agencies will participate in a virtual community meeting to share what was learned from the investigation and take questions from residents. Please register to participate.

The total rainfall for this storm is estimated at 3.47 inches in less than one hour with approximately 104 million gallons of water hitting the Mt. Greenwood community alone. When a storm occurs, rainwater flows into the City’s sewer system which carries the water into an MWRD reservoir. For this storm, MWRD has confirmed that their infrastructure had capacity. This means that the storm overwhelmed the local sewers with water entering the system faster than it could travel into an MWRD site. When this happens, the water overflows the sewers causing residential flooding.

To reduce incidents of residential flooding, restrictors have been installed in all area sewers. Restrictors will hold water on the street during and after a storm, delaying its entry into the sewers. The DWM investigation into this incident found a number of restrictor valves that had been damaged or tampered with. Failing restrictors increase the risk of basement flooding.

The status of gutter downspouts can also contribute to flooding. If a downspout is connected to the sewer system, all of the rainwater that falls on the roof of a home will flow directly into the sewer system bypassing the restrictor altogether. Engineers estimate that connected downspouts can contribute to as much as two-thirds of the water that flows into the sewer system. During a heavy storm, those downspouts could create flooding problems for homeowners. To reduce the risk of flooding, residents are strongly encouraged to disconnect downspouts from the sewer system.