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NRDC, Sierra Club and Prairie Rivers Network filed a federal lawsuit today in the Northern District of Illinois over the regional water treater’s pollution problem. The suit points to discharges of pollution from treatment plants that regularly violate federal standards requiring that discharges not cause or contribute to low levels of oxygen, which fish need to breath; and unnatural sludge or growth of algae, which harms other forms of life in the water.

MWRD manages water infrastructure in the nearly 900 square mile region in Cook County. This includes the area’s sewer lines and sewage treatment plants, most notably the three plants that are the subject of the lawsuit – Calumet, North Side, and Stickney.  These plants, the largest in Illinois, are authorized to release over a billion gallons of wastewater every day to Chicago waters, and that wastewater contains large amounts of phosphorus. Excess phosphorus acts as an unnatural fertilizer triggering growth of algae, aquatic plants and bacteria that block sunlight needed by other aquatic life, sucks the oxygen out of the water, and can potentially be toxic.

Phosphorus is also a major cause of the Dead Zone in the Gulf of Mexico, a huge area in the Gulf where fish and other forms of life cannot survive. Chicago waters, which consist primarily of effluent from the MWRD plants, have been shown to be the largest single contributor of phosphorus to the Dead Zone. As treatment plants around the region address phosphorus, MWRD has fallen behind results achieved by water systems in many Midwestern cities and towns, including Detroit, Milwaukee, and Minneapolis.

MWRD’s water infrastructure also includes dozens of overflow points where untreated sewage combined with storm water pour into the river during rain events that overwhelm the District’s treatment plants.  The sewer system of Chicago, like many older cities, combines waste water with storm water, sending both through the same system of pipes to the sewage treatment plants that are spread around the Chicago area. Because the system is combined, stormwater floods the pipes beyond the capacity of sewage treatment plants, forcing raw sewage and rain water directly to Chicago waters through overflow pipes.” – NRDC Press Release