ABC7's Paul Meincke went 300 feet below the surface for a look at the project from the floor of the Thornton Quarry.
For years this section of the quarry has been redesigned by dynamite for its future as a flood water reservoir fed by the deep tunnel. Next Monday will mark the last blast on the quarry floor.
ABC7's Paul Meincke asks, "Where we now stand will one day be underwater?"
"Yes. Yes. Every time it storms and the water will go about 300 feet above our heads," said Kevin Fitzpatrick, MWRD project manager.
It's a big hole. It'll hold 7.9 billion gallons of water. When it fills, as it will after flooding, the water will be slowly pumped out, treated, and sent to nearby waterways. This is the reservoir's portal to the deep tunnel: a tube 30-feet in diameter lined with concrete a foot thick. It too is nearing completion.
"Just beyond us here is the final earthen plug. And when that's removed in 2015, this all becomes operational," said Fitzpatrick.
Steel gates will be installed in the tunnel to regulate flow in, and prevent the reservoir from backing up. The first phase of the Deep Tunnel project, begun in the 70s several billion dollars ago, now consists of over 100 miles of tunnels. It was designed principally for pollution control. Phase two is about flood control, and the Thornton Quarry is the star attraction. It will not eliminate, but is meant to alleviate a lot of the damage caused by flooding on the South Side of Chicago and surrounding suburbs.
"It's four times more than we can take in all our tunnels around Chicago, so it'll be a huge help we think," said Fitzpatrick.
The Metropolitan Water Reclamation district still has years of work ahead on its overall flood control effort, but it's at point of some celebration because this big bathtub is just about ready.