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.<\/p>\n
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<\/a> along with another flood-control reservoir known as McCook in Bedford Park.<\/p>\n 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\u2019s largest wastewater plants.<\/p>\n The reservoirs have been slowly draining for days as the water they are holding is being pumped to sewage-treatment plants. On Saturday, Thornton was at 82% capacity and McCook was 54%, according to the Metropolitan Water Reclamation District. The district is a government body that treats sewage and manages stormwater.<\/p>\n \u201cIt will take many weeks to completely draw Thornton reservoir down, so a month would be a rough estimate,\u201d said Patrick Thomas, a spokesman for the district. \u201cThe speed at which we can drain the reservoir depends on additional rainfall, incoming sewer flows and treatment plant conditions.\u201d<\/p>\n The reservoirs filled after a rainy July Fourth weekend that was preceded by a very wet spring and early summer. There has only been one rainstorm since the disclosure that the reservoirs were nearly full, and that rainfall was \u201cnegligible\u201d on the sewage levels, Thomas said.<\/p>\n Thornton and McCook are among three reservoirs that serve the Deep Tunnel flood-control program. The massive operation includes more than 100 miles of large underground tunnels that move sewer water from Chicago and other Cook County municipalities out to three reservoirs.<\/p>\n The third reservoir, Majewski in Elk Grove Village, reportedly has no water standing in it. It\u2019s considerably smaller than the other two sites, holding less than 3% of the more than 13 billion gallons in the Deep Tunnel system.<\/p>\n Deep Tunnel, officially known as the Tunnel and Reservoir Plan, began construction 50 years ago. It\u2019s actually still being built out with a project to expand the size of McCook by the end of 2032. Even so, government planners, including those at the district, acknowledge that more must be done to mitigate flooding as extreme thunderstorms are intensifying and are predicted to get worse in part because of climate change.<\/p>\n \u201cThere\u2019s no one silver bullet,\u201d Kari Steele, president of the water reclamation district\u2019s elected board, said at a recent news conference<\/a> related to flood control.<\/p>\n