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State and local agencies are investigating the source of a substance that left a sheen on the Mississippi River on Tuesday that stretched for up to two miles between Coon Rapids and Fridley.

State officials said a smaller sheen was detected shortly after 8 a.m. on Wednesday on the west shore of the river near Coon Rapids Dam Regional Park. Agencies are investigating whether this sheen is connected to the initial incident. 

As of late Thursday, it still was unclear what the substance might have been. Authorities said there did not appear to be any ongoing leak or spill.

The Minnesota Department of Health said all of the water samples it has tested “have come back negative for substances which would pose a threat to the safety of municipal drinking water systems. State agencies continue to test to identify a potential source.”

The initial sheen was first reported around 1 p.m. Tuesday. It extended from the Highway 610 bridge in Coon Rapids downstream to Fridley. 

Fridley Fire Chief Maddison Zikmund said the sheen was initially about 25 feet wide. 

“By 5 p.m. when we had a large presence of different agencies, we were down to approximately 2-feet wide,” Zikmund said. “And then by nightfall, when we really couldn’t see anymore, it was essentially naked to the visible eye — and so it was decreasing throughout the day.”

The cities of Minneapolis and St. Paul closed water treatment facility intakes as a precaution to protect drinking water. A spokesperson for Minneapolis said the city’s water treatment operations resumed Wednesday morning. 

The city says drinking water is safe, but is taking additional precautions, including drawing water deeper below the surface and adding powdered activated carbon to the treatment process.

The Minnesota Pollution Control Agency said crews also deployed booms to divert the sheen away from the city water intakes.

“It was a significant release. But there’s no evidence [Wednesday] to suggest that it’s, for example, a pipeline that burst that’s continuing to leak,” Zikmund said. 

Dan Kraker

Author

State and local agencies are investigating the source of a substance that left a two-mile long sheen on the Mississippi River on Tuesday between Coon Rapids and Fridley. A second, smaller sheen was detected Wednesday. 

Authorities investigating source of two sheens spotted on Mississippi River

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