An Illinois Department of Transportation truck with a plow attachment attempts to remove water flooding I-290 at the CTA Blue Line underpass in Forest Park on Sunday July 2, 2023 | Todd Bannor

The Metropolitan Water Reclamation District of Greater Chicago, the agency responsible for reducing flooding and ensuring Chicago area residents have clean drinking water, insisted that reservoirs and tunnels system worked as intended during the July 2-3 flooding – it’s just that the flooding was more than it could ever accommodate.

On the first weekend of July, most of the Chicago area received anywhere between 3 to 7 inches of rain, but the west and southwest sides of Chicago and the nearby suburbs, including Forest Park and Oak Park, received the brunt of it, getting as much as 8 or 9 inches. 

In a statement to the Review, MWRD spokesperson Alison Fore said that tunnels and reservoir system that were built as part of the Tunnel and Reservoir Plan (TARP), also known as the Deep Tunnel, worked the way they were supposed to, but that was still not enough to handle all the water. 

She said that local stormwater mitigation projects, as well completion of the next phase of the TARP projects, can help address the situation, and further investments will most likely be needed on MWRD’s end.

As Forest Park officials noted in the past, part of the problem is that much of the village has a combined sewer system, into which both sanitary waste and storm runoff flow. The village has been separating sanitary an storm sewers block by block, but there is still ways to go.

Fore said the TARP interception sewers and the McCook Reservoir it connects to did what it could.

“It has captured more than 5 billion gallons between the McCook Reservoir and two tunnel systems to protect Forest Park and other communities that rely on combined sewer systems,” she said. “But these storms demonstrate the need to invest in both gray and green infrastructure to increase capacity for more storms. As storms have increased in frequency and intensity, even the valuable gray infrastructure technologies cannot always keep up with all of the runoff, leading to flooded basements and surface flooding.”

“Grey infrastructure” is traditional sewer systems, while “green infrastructure” projects include projects such as alleys with permeable pavers, which directs storm water away from the sewer system. MWRD helped fund installation of several permeable-paver alleys throughout Forest Park.

The MWRD is currently working to expand McCook Reservoir’s capacity to allow it to capture an extra 6.5 billion gallons from sewers serving areas throughout Cook County. The project is one of TARP Stage 2 projects, and it is expected to be completed in 2029. 

But Fore also said that “more work is needed across Cook County” in the long run.

“Climate change threatens to alter precipitation, water resources and the reliable systems that the MWRD has installed to protect area water quality, public health and safety,” she said. “We believe environmental leadership is our responsibility, so we are looking for solutions to climate change that can keep our region and world safe for future generations.”