U.S. Steel says its Midwest plant in Portage discharged elevated levels of iron Sunday evening, causing an rusty colored plume that entered a Lake Michigan tributary.
The leak prompted the closure of several nearby beaches and a water treatment facility.
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The company idled the Portage plant as a precaution after it said the finishing line of its wastewater treatment facility experienced “an upset condition” and discharged the rust-colored plume into the Burns Waterway, which is about 30 miles east of Chicago.
The company didn't indicate what concentrations of iron were detected in the discharge, and it was not immediately clear if the release posed a threat to public health, the environment or wildlife.