Overflow Action Days

The recent flooding of the Chicago Riverwalk was yet another reminder that water conservation is critical during rain events to conserve and protect clean, fresh water which is one of our most valuable assets and reduce the chance that sewage and stormwater pollution will reach the river.​ 

Based on the concept of Ozone Action Days, Overflow Action Days alert people that before, during, and after rain storms we need to reduce the amount of water that goes down our drains and the chance of combined sewer overflows. 

Recently, Overflow Action Days was featured on WTTW's Chicago Tonight.

Find Out More About It

The purpose of Overflow Action Days is to minimize the amount of water that goes into the sewer system. Water conservation can play an enormous role in protecting our rivers. 

 Albany park flooding in April 2013. Photo courtesy CNT/ RainReady.

Since the MWRD treats all water that enters its sewers, any water conserved effectively increases treatment capacity. If concentrated and timed properly, Overflow Action Days has the ability to offset combined sewer overflows throughout the Chicago River system. Overflow Action Days are necessary because the regional combined sewer system cannot always handle the amount of rain that falls in addition to the daily load of sewage and industrial waste. In addition, parts of the region rely on separated sewer systems and also see harmful pollutants conveyed directly into the river system through stormwater outfalls.

In 1975 the Metropolitan Water Reclamation District of Greater Chicago (MWRD) began construction of the Tunnel and Reservoir Plan (TARP). The system captures excess stormwater and wastewater until it can be treated a one of three MWRD plants.  TARP was designed to prevent flooding and combined sewer overflows. However, while the system of tunnels and reservoirs has contributed to significant improvements in water quality, the reservoirs are not complete—including the 10 billion gallon McCook Reservoir, scheduled for completion in 2029—and climate change has exacerbated these issues.

Why should you act now?

The Chicago metropolitan area cannot rely solely on MWRD’s tunnel and reservoir system to solve flooding and sewer overflows (CSOs). Climate change forces us to act collectively and to support multi-pronged approaches to reduce the environmental and economic damages of these extreme rain events. 

Climate change is making it harder to manage stormwater and prevent CSOs in the Chicago metropolitan area. Heavy isolated rains and 100-year storms now occur every couple of years and can overwhelm the system.

River Park boat dock  flooding in April 2013.

A number of Chicago metropolitan area precipitation records have been broken in the last three years, leading to widespread flooding, property damage, massive amounts of CSOs, and even a state of emergency:

  • June 2015: Early June saw record breaking precipitation and, on June 15, a Chicago weather station recorded 2.56 inches of rain. This massive multi-day rain event caused flash flooding and sewage overflows at nearly every point on the Chicago River.
  • April 18, 2013: Government officials declared a state of emergency after the second-rainiest April day in Illinois history, 3.53 inches. The two-day total of 5.53 inches of rainfall is about the amount that typically falls over a two month period.
  • Weather data shows that the number of 100-year rain events has nearly doubled over the past century due to a rapidly changing climate. The increase in 100-year rain events necessitates that we increase capacity in our sewer system, demanding both water conservation and water storage (TARP and on site storage). 

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