Deep Tunnel reservoir will take at least a month to drain

The Thornton reservoir, a massive south suburban quarry within the Deep Tunnel flood-control system, will take at least one month to drain. Located in South Holland, the facility collects sewer wastewater during heavy storms before pumping it to the Calumet treatment plant in the Riverdale neighborhood. This event marks the first time since its 2015 opening that the reservoir reached near capacity, managing billions of gallons of stormwater and sewage to prevent regional flooding.