Tribar officials said the employee no longer works for the company.
"Based on an initial investigation, those automated controls were all functioning properly at the time the plating solution was released to the wastewater treatment plant," Tribar said through a spokesman. "However, the controls were repeatedly overriden by the operator on duty while the facility was shut down for the weekend."
A cease and desist order issued by the city of Wixom remains in effect for the plant, as does a "no contact" advisory for areas downstream from the release on and near the Huron River.
The Michigan Department of Health and Human Services continues to recommend that people and pets avoid contact with the Huron River water between North Wixom Road in Oakland County and Kensington Road in Livingston County, including Norton Creek, Hubbell Pond (also known as Mill Pond in Oakland County) and Kent Lake.
Hexavalent chromium can cause harm through ingestion, skin contact or inhalation.
As of Aug. 8, a total of 144 samples had been collected along the 42-mile river and three have detected hexavalent chromium: two in Hubbell Pond in Milford and one in the middle of Kent Lake.
Wixom City Manager Steve Brown said Aug. 10 that tests appear to indicate that the amount of hexavalent chromium in the contaminated liquid was less than previously feared.
"Test results on the effluent from the [wastewater treatment plant] into the watershed show the actual quantity discharged from the WWTP was 20 pounds of total chromium, which includes hexavalent chromium. That is 0.0025% of the initial estimate of full hexavalent chromium," Brown said in the email.
He said the city has not issued fines to the company.
"Due to the seriousness of the violations, EGLE has initiated accelerated enforcement, which will initiate an administrative consent order process and seek full cost recovery from Tribar," EGLE said.
It is unclear what fines the state plans to impose.
Another remaining question is why the public was not notified sooner.
EGLE initially notified the public through an Aug. 2 news release that said the department was notified of the release the day prior.