The massive Thornton reservoir, a south suburban quarry holding billions of gallons of stormwater and sewage that nearly filled up this past week, will take at least a month before it drains.
Thornton is part of the Deep Tunnel flood-control system and resembles a canyon in South Holland. It takes in sewer wastewater during heavy storms that is later pumped out to the Calumet treatment plant at East 130th Street in the Far Southeast Side Riverdale neighborhood. For the first time since opening in 2015, the quarry filled to near capacity along with another flood-control reservoir known as McCook in Bedford Park.
McCook is draining to a much larger treatment plant known as Stickney in Cicero. That plant can process more than three times the wastewater than the Calumet plant in a single day. Stickney is considered one of the world’s largest wastewater plants…