The backward river backs up. A metropolis has risen from wetlands that once stored and filtered copious amounts of water. In their place concrete spreads from the lakefront into the Illinois prairie. When rain hits these impermeable surfaces, it is moved toward storm drains. Beneath the ground, these drains meet with those taking sewage from homes and businesses. This is called a combined sewer system.
As the city expands, so does its sewage. Rain events— high volumes of rain hitting the ground in a short period of time—mark a prominent effect of accelerated climate change in the Great Lakes region. With only so much room to hold water, the toxic brew of sewage and rain often rises back to the surface and floods Chicago.
During a serious rain event, the very waters intended to be sent far away from Chicago are spit up into the river through a second set of pipes called outflow pipes that pour untreated water from the combined sewers back into the river. This is called a combined sewer overflow (CSO).
In 2019, more than 50 CSOs were recorded. According to 2017 research, an average of 318 million gallons of water poured into the Chicago River during and after rain events. The failures of the combined sewer system and other water infrastructure are not uniformly experienced. Instead, low-income communities on the South and West Sides of Chicago experience the most and the worst flooding. Between 2007 and 2016, flood damage insurance payments totaled more than $400 million, where 87% were paid to residents in communities of color.
The lock between Lake Michigan and the Chicago River is meant to draw lakewater into the Chicago Area Waterway System. But, when it opens, it can spew waste into the lake –the drinking water source for millions of people. This recurring public health hazard represents exactly the opposite of what the Sanitary and Ship Canal and the Deep Tunnel were intended to do. Swollen by outfall pipes, the backward river returns to its original course. In this way, the sewers exact their revenge.
