Marengo residents have received notices from the city about elevated manganese levels in the city’s water supply – but residents do not need to panic or run out and get bottled water, city officials said.
“Manganese is a naturally occurring mineral found in rocks, soil, and ground water,” Marengo officials said in an FAQ. The mineral is a normal and essential part of human diets, but elevated levels can increase risks of health problems, officials said.
But Marengo residents do not need to take any action, and city officials said wells supplying the city’s water do not show elevated levels of manganese or any other contaminant, as the well in question has been taken offline. The water system is in compliance with Illinois EPA standards and the water is fine, officials said.
City Administrator Derik Morefield said the city voluntarily took Well 6, which had the elevated manganese levels, offline. He added the IEPA didn’t require or request Marengo do that.
Morefield said residents are getting water from another well that has no issues and that’s why the water meets IEPA standards. Well 6 will not go online until the city ensures manganese levels are below the limit, he said.
Despite the well being idled, residents were advised in the mailed notice not to give tap water to infants or boil the water.
However, resident don’t need to purchase bottled water because of the manganese, the city said. Residents also will not be eligible for credits or reimbursement because of it.
Some home water filtration systems, including softeners and reverse osmosis, can “remove elevated forms of manganese levels and other water contaminants,” officials said in the FAQ. Residents should check manufacturer specifications if they want to take action on their home systems.
City officials said the notice that went out was required by the Illinois EPA.
The Marengo Water Department monitors drinking water for naturally occurring and man-made contaminants and follows the Illinois EPA established testing schedule, officials said.
“In the fourth quarter of 2025, one sample from a group of four taken from Well #6 showed manganese above the allowable state threshold. The other three samples in that group were within acceptable limits. Importantly, no subsequent follow-up samples have exceeded the threshold,” city officials said in a follow-up communication.
The sample results were reported to the Illinois EPA but officials said one “exceedance in routine monitoring does not automatically trigger public notification.”
But in January, the Illinois EPA told Marengo to inform residents, despite no detection of further elevated levels of manganese. Marengo officials are conducting additional testing this week to expedite IEPA confirmation that the well in question can be put back into use, which the city expects by the end of the month.
Marengo officials were notified Oct. 29 that a water sample “at Marengo Well #6 exceeded the IEPA MCL of 0.15mg/L,” adding three more samples were pulled and the combined average of the samples exceeded the maximum contamination limit.
The well is also offline as part of preparations for a new water filtration plant. The new plant is meant to filter out, rather than treat, drinking water contaminants, and improve water service, officials said.
A new well, Well 9, is going to be added to service the city and will enable Well 6 to be “a supplementary source, farther lessening its use, and decreasing the likelihood of elevated manganese levels in the future,” officials said.
City officials said Marengo follows IEPA testing and notification protocols and IEPA policy dictated the notification schedule.
“Procedure does not trigger public notifications for routine test results; those go to our Water Department and the IEPA. Further notifications to the public are then determined based on results and procedures and in coordination with IEPA. The schedule is predetermined, and also subject to IEPA discretion, which is why it may leave the impression that this is tardy,” according to the FAQ.
According to the notice provided to Marengo residents, consuming water with too much manganese over an extended period of time can cause problems with memory, attention and motor skills, while infants can develop learning and behavior problems.