Chicago Deep Tunnel (TARP, 1975-present)
Chicago began building a web of tunnels and reservoirs to capture combined sewer overflows rather than discharging into Lake Michigan. The system has grown over five decades, with major segments still under construction.
Early tunnels cut the worst Lake Michigan beach closings andreduced basement flooding.
Became the model for large-scale CSO storage, inspiring cities including Milwaukee and now Hartford.
Shows how multi-decadal sewer storage programs can reshape urban drainage, the model MDC is following at smaller scale.
