How could I live in Chicago at one point and not know that there were 109 miles of tunnels being built under it? Not just small tunnels, but big ones, 9 to 33 feet in diameter. It’s all part of the Tunnel and Reservoir Plan (TARP) also known as “The Deep Tunnel”. It is pretty deep, as much as 350 feet below the surface, excavated through limestone since the 1970’s using similar equipment to the machines that drilled the Chunnel between the UK and France. But this tunnel system does not transport people. It carries and stores sewage and storm water overflow from the area to reservoir sites until water treatment plants can catch up with the peak flow during big storms.
It’s curious to me to read different descriptions of the project. The Metropolitan Water Reclamation District of Greater Chicago who runs the Deep Tunnel thinks it’s the best thing ever, and touts all the engineering awards it has won. Most of the $4 billion in funding has come from the EPA, and the project has helped improve the water quality of Lake Michigan and the Chicago River by keeping storm runoff from going directly into those bodies of water. Chicago has a mixed sewage and storm water system (like many cities) so that means sewage isn’t overflowing into the river or lake as well.
Then we’ll have to think of some NEW use for the Deep Tunnel. Fresh water storage for drought? Future “L” routes? Underground linear museum? What else?