Mason City officials report they stopped discharging wastewater to the Winnebago River at 8 p.m. June 18.
The discharge was reported Friday after a sewer line collapsed in the 300 block of South Rhode Island Avenue. The city pumped the untreated wastewater to a storm sewer that flows into the river near the softball complex on Second St. NE.
The DNR recommends keeping children and pets away from the riverbanks near the discharge for the next 24 hours.
DNR plans to review the matter and consider appropriate enforcement action.