ST. CHARLES, Mo. – On Wednesday, the Environmental Protection Agency (EPA) instructed the City of St. Charles to cease operations for City Well 4 after the well previously tested positive for vinyl chloride.

Vinyl chloride is used in the manufacturing of PVC. It can be found in PVC pipes, vinyl siding, packaging, car parts, furniture, shower curtains, and pet and children’s toys.

The gas has been banned in cosmetics, hair spray, and other products. The National Cancer Institute has identified vinyl chloride as a cancer-causing agent, saying inhalation of the compound is linked to liver cancer.

City leadership and Ameren Missouri are pointing the finger at each other for this particular incident. The city asserts that a barrier Ameren built at the substation failed, allowing vinyl chloride to enter Well 4.

Well 4 is connected to the city’s sewer line and not the water treatment plant.

An Ameren Missouri spokesperson said Well 4 has long been obsolete and that the city was warned against using the well. Furthermore, Ameren claims the city turned Well 4 on in order to undermine Ameren’s remediation efforts and that using the well does not benefit St. Charles residents.

In October 2022, St. Charles Mayor Dan Borgmeyer said the majority of the city’s water wells had been shut down due to contamination with hazardous chemicals. By December, the city had down five of its seven wells. Ameren’s Huster Road Substation, located near the Elm Point Wellfield, was leaking carcinogens into the soil and groundwater, Mayor Borgmeyer said at the time.

In the 1970s, Ameren Missouri used a scouring solvent called tetrachloroethylene to clean equipment at the substation, according to Paul Michalski, a senior hydrogeologist for 212 Environmental. Ameren attempted to degrade the chemical in soil and groundwater. Two carcinogens were created in the process—cis-1,2-Dichloroethene and vinyl chloride—both of which are harmful to human beings.

In January 2023, the EPA collected both ground and water samples from the Elm Point Wellfield. Lab results confirmed the presence of both cis-1,2-Dichloroethene and vinyl chloride and in February, the EPA identified the Ameren substation as the source.

This past August, the City of St. Charles briefly shut down Well 10 following a drop in the free level of ammonia in raw water and had to rely entirely on St. Louis City for its water needs.

St. Charles has purchased additional water from St. Louis since 2017.

At present, six of seven water wells in St. Charles are shut down. The water being pumped from the remaining well is still safe to drink, according to the EPA.