Fixing Flooding Problems

Our vision to increase residents’ enjoyment of all Chicago’s water features includes addressing flooding problems that plague some neighborhoods. Preventing flooded basements and other flood damage is a critical need to be addressed as part of the permanent re-separation of the Great Lakes and Mississippi River basins. Efforts already underway by the Metropolitan Water Reclamation District of Greater Chicago (MWRD), the City of Chicago, other municipalities and Chicagoland residents will continue to reduce flooding impacts.

Metropolitan Water Reclamation District
of Greater Chicago (MWRD) Efforts

Combined Sewer System

The Metropolitan Water Reclamation District of Greater Chicago treats much of the wastewater and stormwater generated in the Greater Chicago region. Within the Chicago waterways, wastewater is treated and discharged at three large wastewater treatment plants- Northside on the North Shore Channel, Stickney on the Chicago Sanitary & Ship Canal and the Calumet plant on the Little Calumet River.

Much of Chicagoland uses a combined sewer system in which stormwater is collected in the same pipes as sanitary waste from homes and businesses. This system works fine during dry weather and light rainfall events but becomes overwhelmed during heavy storms. During very wet weather, sewers can back up into basements and a mix of untreated stormwater and wastewater overflows at various points within the Chicago Area Waterway System (CAWS) and even into Lake Michigan. This untreated soup is a health hazard to people exposed to these combined sewer overflows (CSOs) and backups.

Since the 1970s MWRD has been working on the Tunnel and Reservoir Project (TARP) to collect and store the combined storm and waste water from all but the largest storms. With this system in place, MWRD will be able to hold, treat, and then discharge wastewater after the storm subsides. In 2006 MWRD completed the 109 mile system of tunnels that collect from the combined sewers and provide some storage. Reservoirs to hold more wastewater will be completed in the coming years. Thornton Reservoir, with a storage capacity of 7.9 billion gallons, is due to be completed by the end of 2015. Located in the Calumet River watershed, Thornton should solve many of the problems experienced by residents of Southside Chicago and southern suburbs. The first 3.5 billion gallons of storage in the McCook Reservoir is to be ready by Dec. 31, 2017 and another 6.5 billion gallons storage is scheduled for completion in 2029.

Watershed Management Ordinance

In 2005 the Illinois General Assembly granted MWRD the authority to act as Cook County’s stormwater management agency. Working with many stakeholders, MWRD developed a draft stormwater ordinance in 2009. The draft ordinance will protect residents from flooding by increasing protections for wetlands and stream corridors and requiring steps to hold and infiltrate stormwater.

Final adoption and implementation of the ordinance is key to ensuring that development and re-development projects in Cook County do not exacerbate flooding problems.

Green Infrastructure

MWRD has also recently committed to producing at least 10 million gallons of floodwater retention through green infrastructure practices. Rather than send stormwater into sewer system, green infrastructure eases the burden on sewers and wastewater plants. Green infrastructure makes use of plants and soil to capture, infiltrate and evapotranspire stormwater. These can include areas of native landscaping in swales, rain gardens and wetland areas as well as green rooftops. Permeable pavement, rain barrels and other methods to harvest and reuse stormwater are also green practices.

Many organizations and government bodies throughout the Chicago region have recognized the importance of green infrastructure in reducing flooding problems. We don’t have to wait for projects like MWRD’s TARP to be completed to take steps to reduce flooding problems. Green infrastructure projects can be undertaken by individual homeowners and businesses as well as municipal governments. Rain gardens and rain barrels are easy initiatives which individuals can install to capture precipitation and reduce their property’s contribution to storm runoff.

Basin separation and flooding

The planned improvements in TARP and green infrastructure will be important pieces as basin separation locations are identified. The Great Lakes Commission and Great Lakes and St. Lawrence Cities Initiative have identified improved flood plain storage and separation of combined sewers systems as key tools to reduce flooding problems under various separation options.