Chicago Discharges Waste Water 99 Billion Gallons Pumped into Lake After Record Rainfall
By DON BEHM
Chicago’s deep tunnels, surface reservoirs and waterways filled to the brim in last weekend’s record rainfall, prompting the Metropolitan Water Reclamation District there to open emergency floodgates and discharge up to 99 billion gallons of storm water and diluted sewage to Lake Michigan to avoid urban flooding.
It is the largest volume of waste water to flow into the lake since the first section of the deep tunnel opened there in 1985, district records show.
In Milwaukee, by comparison, sewer overflows discharged an annual average of 8 to 9 billion gallons of storm water and sewage into the lake before a deep tunnel system was opened here in 1994. The largest annual overflow volume reported since the tunnel system opened was 4.37 billion gallons in 1999.
In Chicago, the weekend deluge by early Saturday had filled the 2.5 billion-gallon capacity of the 109-mile-long network of storage tunnels, along with the more than 4 billion-gallon capacity of district reservoirs, said Jill Horist, spokeswoman for the reclamation district.
About 6.6 inches of rain — a one day record for Chicago — fell Saturday at O’Hare International Airport.
“Three gates to the lake were wide open for a day and a half,” Horist said.
An estimated 4 billion gallons of water an hour flowed out of the gates to the lake during the peak of the storm.
District officials said little sewage flowed to the lake while gates were open.
“There was an insignificant amount of sewage, much less than 1%” of the total volume of the discharge, Horist said.
Even so, the volume of waste water flowing to the lake surprised environmental advocates at the Alliance for the Great Lakes office in Chicago.
“That’s astronomically high,” said Cameron Davis, president of the regional alliance.
“We’re concerned anytime waste water goes into the drinking water source for 10 million people,” Davis said.
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