Chicago's "sewer network, built and maintained by the Metropolitan Water Reclamation District of Greater Chicago, is a behemoth among urban wastewater collection systems. Girded by more than 109 miles of deep underground pipe, Chicago's massive 'Tunnel and Reservoir Plan' (TARP) ranks among the nation's largest public works projects, both in term of scale and cost, estimated at $3.58 billion."
"But questions remain as to whether -- having installed all this -- Chicago can keep up with the increasingly stringent demands of Mother Nature, especially as climate change ushers in greater weather instability marked by repeated record precipitation events.
The heaviest rain in Chicago history, a 6.86-inch deluge on July 23, 2011, put its so-called Deep Tunnel system to its toughest test yet. It flunked, and sewer managers were forced to relieve flooding by opening outfalls to the Chicago River and Lake Michigan, allowing tens of millions of gallons of filthy, bacteria-laden stormwater to pour into local waterways, including along the swimming beaches that line Lakeshore Drive."