MARENGO – City officials have halted a $12 million upgrade of Marengo’s wastewater treatment plant because crews discovered the expansion site is an old landfill with 12 feet of rotting waste below the surface.

The City Council met in special session Monday to decide what to do with what a private engineer called the decaying, nonhazardous waste.

After more than 90 minutes behind closed doors, City Manager Gary Boden made about a one-minute statement that the council will meet Monday on “the potential of litigation” and for city staff to try to answer aldermen’s concerns about the property and the upgrade.