The automotive supplier behind the release of 10,000 gallons of contaminated liquid into the Huron River in suburban Detroit has been cleared to resume operations in Wixom, Mich.
Injection molder Tribar Manufacturing was given "conditional approval" to resume wastewater discharge to the Wixom Wastewater Treatment Plant, the city said Sept. 1.
The company had been under a cease-and-desist order from the city since a July 29 incident allowed cancer-causing hexavalent chromium to flow into public waterways connected to the Huron River.
"Fortunately, other processes at Tribar and the WWTP served to contain the hexavalent chromium prior to discharge from the WWTP as testing results, conducted at the time of the incident and after, indicated the WWTP discharge was compliant with regulatory guidelines," the city said in a news release.
Before resuming operations, Tribar was ordered to make sure at least two operators are working whenever wastewater is being generated, add an automatic WWTP shut-off valve to stop discharge and implement comprehensive documentation of existing and new process controls and training of company staff.
Tribar parted ways with the worker responsible for the chemical release shortly after an investigation found the operator overrode waste treatment alarms 460 times during the incident and failed to immediately notify state authorities.
Michigan Department of the Environment, Great Lakes and Energy spokeswoman Jill Greenberg said earlier that the investigation of Tribar is ongoing and potential fines and penalties would be assessed upon completion
Testing by EGLE found slightly elevated levels of hexavalent chromium downstream from the release, including in lakes at nearby state and county parks.
The "avoid contact" order was lifted Aug. 12 after it determined the chromium levels in the Huron River were below levels of concern for effects on human health. Review of data also found the amount of hexavalent chromium released into the river was much less than originally thought and 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.