The digging of the Deep Tunnel begins
Photo: Zbigniew Bzdak/Chicago Tribune

August 25, 1976

Conceived half a century ago and not scheduled for completion until 2029, it’s one of the biggest civil engineering projects ever undertaken. Engineers called this superhighway of sewers and reservoirs a “storm bottle,” designed to solve one of the most intractable problems of our low-lying waterfront city: street flooding and the surging of raw sewage into Lake Michigan and the Chicago River after heavy rains. The completed portions of the $4 billion system help to prevent sewage releases, though increased precipitation due to climate change makes the prospect of stopping them less certain every year.