Deep Tunnel, Chicago’s system of more than 100 miles of underground tunnels and reservoirs designed to hold floodwater, was nearly at capacity for the first time in the city’s history last week after more than 3 inches of rain — nearly a month’s worth — fell over the July 4 weekend, according to WBEZ.

The likelihood of heavy rainstorms that can dump more than 8.5 inches of rain in 24 hours has increased more than sevenfold in Chicago over the past century, but the city’s sewers can handle just 2 inches of rain before flooding is likely, according to the Chicago Sun-Times.

“We can only expect more storms to come as the effects of climate change hit Chicago’s communities,” Johnson said during a July 8 news conference. “And of course, they hit the South and West Side communities especially hard.”

The Center for Neighborhood Technology found that 87% of flood damage insurance claims in Chicago between 2007 and 2016 were in communities of color on the city’s south and west sides.

The Illinois Institute of Technology’s Storm Water Infrastructure Project found that underserved communities in Chicago are more vulnerable to flooding because of the city’s natural drainage pattern toward a canal on the southwest side, Fox 32 Chicago reported. Analysis of 311 calls during extreme rainfall events last summer found “a pattern of underserved communities being hit the hardest,” according to the report. 

The two underground installations will help reduce street and basement flooding and protect more than 2,900 homes, businesses and other buildings, according to the news release. The city and the Metropolitan Water Reclamation District will evaluate the project’s performance to help inform future flood mitigation and resilient infrastructure projects, the release states.

Chicago Department of Water Management Commissioner Randy Conner said the project makes it possible for the city to address flooding more quickly and efficiently in targeted areas instead of replacing entire sections of the sewer system.

“We have to be able to come up with innovative ways of upgrading the sewer system,” Connor said at the Tuesday news conference. “Sometimes we can upsize them, sometimes we can’t, so that’s why we have projects like this.”

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