Chicago’s Deep Tunnel: The solution to urban flooding, or a cautionary tale?

Except that Chicago's publicly stated position is that the Deep Tunnel system is not the solution. This is not a new thing, either. It's been that way for more than 2 decades.

For more than 10 years, they've had a stormwater management building ordinance and (with few exceptions) any project (new construction or renovation) that changes the amount of stormwater exiting a piece of property is subject to it. It limits the flow rate of stormwater leaving, the volume of stormwater leaving, and the amount of sediment that can leave a piece of property. It is entirely math-based, with published formulas and coefficients and makes determining compliance straightforward, objective and fast.

They've received international recognition for their incremental approach to stormwater management, which recognizes that the vast majority of property in the city is private property built long ago. As for public property, whenever the city rebuilds an alleyway, it is done with permeable pavement and is disconnected from the sewer. Whenever the city rebuilds a road, it is disconnected from the sewer to the extent that surrounding private property allows. Last year an entire block of a road near me was rebuilt and the side that was adjacent to a railroad embankment was built with swales every 50 feet or so to manage stormwater. It was actually visually attractive as well.

The specific project I linked to involved installing over 25 miles of storm drain to avoid combined sewer/storm overflows into the ocean. We lived on one of the impacted streets.

Older houses had gutter downspouts that dumped all rainwater into the combined storm drain/sewer system. The MWRA came to neighborhood association meetings, and helped residents to re-aim downspouts onto green space.