The former operations supervisor at Sioux City’s wastewater treatment plant intends to plead guilty to federal charges he conspired to manipulate water sample test results.

Patrick Schwarte’s attorney filed the plea notice Monday in U.S. District Court. His plea hearing is scheduled for January 23rd.

Prosecutors say chlorine was added to wastewater on days that E. coli samples were taken.

The samples then showed plant discharges into the Missouri River met federal limits for levels of fecal coliform and E. coli. The chlorine was reduced after the tests, saving the city money.

The city dismissed Schwarte and the plant superintendent in June 2015 after the Iowa Natural Resources Department began an investigation.

By Woody Gottburg, KSCJ, Sioux City