ST. CHARLES COUNTY, Mo. – The city of St. Louis is now the sole provider of water for the city of St. Charles.

The city of St. Charles has been dealing with a contamination problem with its water for quite some time, but Tuesday morning a key component – ammonia is missing from the water, and now the water treatment plant is shut down.

The city of St. Charles has a total of seven drinking water wells at the Elm Point wellfield. The last operational well was number ten, but the city had to shut it down over the weekend because of a drop in the level of ammonia in raw water. Ammonia is used to disinfect the water.

Well number 10 provides 1/6 of the water demand for St. Charles customers, and summer demand is between 6 and 7 million gallons a day. City officials have requested that the EPA investigate the cause of the sudden change in ammonia levels.

You may remember that the city of St. Charles filed a lawsuit against Ameren Missouri over wellfield contamination back in May. The EPA revealed that an Ameren substation was the source of the city’s water well contamination and was leaking carcinogens into the soil and groundwater, and the city requested Ameren clean it up.

FOX 2 asked Mayor Dan Borgmeyer if this latest water issue has anything to do with this long-standing problem with Ameren.

“What we suspect is that Ameren, in their process of cleansing the substation, has released a lot of chemicals into the soil, which stripped out the contaminants, but it stripped everything else out too, Borgmeyer shared. “So now we have an aquifer that has no ammonia in it.”

FOX 2 will update this story with more information as it becomes available.