The fine stems from a series of incidents that began in June 2020, during which MPC employees discharged pollutants into the Milwaukee Metropolitan Sewage District.

Milwaukee Precision Casting is a casting foundry that makes simple cast steel components and complex aluminum cast components for the military, firearms, medical, and aerospace industries. The company uses corrosive chemicals to dissolve casting molds.

MPC has operated a casting foundry in the City of Milwaukee since 1990.

The MPC facility located at 3400 S. Nevada St. houses a sump pit that’s connected to the Milwaukee Metropolitan Sewage District sewage system, according to the plea agreement reached in July.

Beginning in June 2020, MPC and its employees discarded used and untreated chemical waste, including waste with a pH below 5.0 standard units, through the sump pit into the MMSD sewage system. This continued through about September 2021, according to the plea agreement.

The Clean Water Act prohibits people and businesses from discharging any pollutant into any body of water in the U.S. without authorization. Federal regulations define the term “pollutant” to include discharges having a pH lower than 5.0 standard units.

“MPC acknowledged that it operated without the necessary industrial pretreatment permits from the Milwaukee Metropolitan Sewage District and that its employees had discharged untreated wastewater into a sewage system operated by the MMSD,” according to Monday’s sentencing announcement.

Half of the $100,000 fine MPC is slated to pay will go towards approved environmental compliance and remedial efforts.