Wisconsin v. Illinois
Headline: Great Lakes water diversion limited as Court orders Illinois and Chicago’s sanitation district to reduce Lake Michigan outflow, protect lake levels and navigation, and allow time to build sewage treatment.
Holding: The Court held that the Chicago Sanitary District’s large diversion from Lake Michigan must be reduced because it unlawfully lowered Great Lakes levels, ordering a decree to restore navigable capacity while allowing time to install sewage treatment.
- Requires Chicago to reduce Lake Michigan diversion and build sewage treatment.
- Restores higher lake levels to aid Great Lakes navigation and local harbors.
- Gives Midwest states a path to stop out-of-state water takings harming shores.
Summary
Background
Several Midwest States (Wisconsin, Minnesota, Michigan, Ohio, Pennsylvania, New York) sued Illinois and the Sanitary District of Chicago to stop the withdrawal of about 8,500 cubic feet per second from Lake Michigan. A Special Master investigated history, engineering, permits, and effects. He found the diversion has lowered lake and connecting water levels about six inches, harmed navigation, harbors, resorts, fisheries, and riparian property, and that the Sanitary District has relied on an Army Corps/Secretary of War permit dated March 3, 1925 that was temporary and conditional on sewage treatment.
Reasoning
The core question was whether federal authority under the 1899 Rivers and Harbors law and the Secretary of War’s permit lawfully allowed the large diversion. The Court explained that the Secretary can approve works to prevent unreasonable obstructions to navigation, and that such technical delegations are lawful. But the permit here was issued to meet an emergency created by the District’s own failure to control sewage, and it was temporary and conditional. The Secretary could not base a continuing large diversion solely on local sanitation. The Court held the diversion beyond what was needed to protect navigation was not legally supported and ordered relief to end the unlawful diversion while protecting public health during transition.
Real world impact
The decision requires the Sanitary District to reduce the diversion and to install sewage treatment, restoring lake levels gradually over years and improving navigation and local harbors. The Court did not issue a final permanent schedule itself but sent the case back to the Master to design a practicable timetable and detailed decree balancing lake restoration with public health needs.
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