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State lifts Huron River no-contact recommendation after tests show little hexavalent chromium

Kent Lake
By Colin Andersen Photo…, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=54602341
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wikimedia
Kent Lake is part of the Huron River system; the state advised no contact with the water pending the results of testing for hexavalent chromium, a carcinogenic chemical.

Swimming, boating, fishing, and other recreational uses of the Huron River are back.

That's after the Michigan Department of Health and Human Services lifted its do-not-contact recommendation urging people to stay away — and keep their pets away — from the river.

A hexavalent chromium discharge by Tribar Technologies in Wixom in late July led the health department to make the recommendation, but data it received on Wednesday from the Michigan Department of Environment, Great Lakes, and Energy led the health department to conclude that chromium levels in the river were below levels of concern for effects on human health. The data review found that:

  • The amount of hexavalent chromium released into the Huron River was much less than originally thought.  
  • The release was predominantly trivalent chromium, not hexavalent chromium. Trivalent chromium is a micronutrient that is part of humans’ diet and is far less concerning from a health perspective. 
  • Hexavalent chromium was not detected in the majority of the surface water samples. The detections in three samples were well below the level that could cause harm.

The environment department's report said most of the hexavalent chromium was either captured by Tribar's filters, or converted into trivalent chromium inside the Wixom Wastewater Treatment Plant.

The report said the department is confident that less than 20 pounds — far less than the 4,000-plus pounds originally feared — of hexavalent chromium is believed to have entered Norton Creek, part of the Huron River system.

The incident caused widespread concern, especially among people in the city of Ann Arbor, which relies on the Huron River for the majority of its drinking water.

The state health and environment departments said they will continue testing the river water, and Tribar Technologies still faces multiple violation notices for the incident, which happened after an operator at the chemical plant overrode waste treatment alarms 460 times between 5:00 and 7:45 p.m. the night of the discharge. Tribar said the operator in question no longer works at the company.

Tribar did not immediately notify state environmental regulators of the spill when it was discovered on Monday, leading to one of the violation notices.

In a statement Friday, the company said its filtration system worked as designed.

"While it’s very disappointing the discharge occurred, the Tribar filtration system performed as it was designed, capturing nearly all the hexavalent chromium prior to release," the company said. "Additionally, the quick action taken by the City of Wixom wastewater treatment operators helped contain any discharges to the Huron River system."

Tribar said it's "making changes" to its environmental operations "in order to make sure these types of events do not occur in the future" and will work with two environmental consultants "to assist the company with ongoing environmental issues, processes, and procedures."

Tracy Samilton covers energy and transportation, including the auto industry and the business response to climate change for Michigan Radio. She began her career at Michigan Radio as an intern, where she was promptly “bitten by the radio bug,” and never recovered.
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