The waste included a chemical from a family of chemicals known to be hazardous to human health, federal prosecutors alleged in a criminal charge against Robert Massey, owner of Oil Chem Inc.
Massey was charged with violating the federal Clean Water Act. The charge was filed as an "information," which typically means a guilty plea is expected.
A message seeking comment was left for Massey’s attorney Tuesday.
Oil Chem processes oily industrial waste. Its permit says certain treatment steps must be taken before waste goes to Flint’s wastewater treatment plant and ultimately the Flint River, according to the government.
The company didn’t have permission to get rid of landfill leachate, which percolates through garbage and typically contains hazardous chemicals, the Dec. 21 court filing states.
Nearly 48 million gallons of liquid landfill waste were released into Flint’s sewer system, about half of it in 2014-15, the government alleged.
"Oil Chem employees routinely performed this activity at or around the close of business for the day, allowing the landfill leachate to flow into the sanitary system overnight," the charge says.