Ensuring the Safety of St. Charles' Drinking Water

Yes. The water coming out of the faucet at homes in St. Charles has been safe and remains so. Ameren Missouri remains committed to the safety of St. Charles residents and working cooperatively with the EPA to address groundwater impacts at and near the Huster substation.

The EPA adds:
Water being distributed to the public after treatment at the City’s water treatment plant has regularly been sampled for VOCs, including vinyl chloride and cis-1,2- DCE for over 20 years, and has never shown any level of contamination. EPA has found no reason to indicate that there are any health risks posed by drinking, cooking, bathing, or otherwise using the water that is supplied by the City of St. Charles.

On February 9, 2023, EPA announced that its investigation has identified that the source of the recent low-level detections in the groundwater is from Ameren’s Huster Substation site.  

Ameren has welcomed EPA’s investigation and has cooperated fully. Ameren has been moving forward with the solution to address historical groundwater issues underneath the substation. With the approval of EPA, Ameren has taken multiple measures to aggressively address the residual chemicals of concern at the substation and in surrounding groundwater.

Ameren Missouri has started implementing EPA-approved measures to contain and remove remnants of cleaning solvents used decades ago at a substation in the City of St. Charles. Treatment techniques targeting chemicals directly underneath the substation site are now underway, with completion set for the end of March, followed by a monitoring period. All work is being performed under the supervision of the EPA. Based on prior experience, a significant reduction in concentration levels is expected by early summer.

In addition to injecting sodium persulfate onsite to destroy solvents in groundwater beneath the substation followed by application of a biomass commonly used to further break down solvents, Ameren is installing subsurface barrier walls or curtains (Permeable Reactive Barriers or PRBs) at strategic locations on the substation property for added protection utilizing a technology known as zero valent iron (ZVI). As groundwater passes through the barriers, residuals in the groundwater are removed and destroyed before groundwater leaves the substation property. In addition, utilizing a series of extraction wells, an above-ground groundwater capture system permitted by the Missouri Department of Natural Resources also contains and treats on-site groundwater. Cleanup efforts will continue until groundwater beneath the substation achieves the strict standards established by the EPA. The barrier installation and treatment applications are expected to begin to work immediately and to be completed by the end of March. Monitoring will measure effectiveness.

Ameren Missouri has a strong record of environmental stewardship and will continue to take treatment actions to protect drinking water. On behalf of more than 700 Ameren co-workers who live or work in the City and County of St. Charles, and the thousands more who live in the metropolitan St. Louis area, Ameren will continue to work cooperatively with the EPA and the Missouri Department of Natural Resources (MDNR) on site clean-up.

The EPA adds:
ZVI has been used for more than 130 years to treat groundwater. The ZVI acts as a reducing agent to provide electrons to degrade the chlorinated compounds to non-toxic ethene and ethane. The ZVI has been successful in the treatment of groundwater contaminants in and around the Ameren substation. The plume shifted to the east most likely due to increased pumping rates of City Wells #6 and #7, which had not been used in several years, and the installation of City Well #10. For this reason, Ameren is installing additional ZVI permeable barriers to treat contaminants as the groundwater passes through the barriers. Additional remedies will be evaluated moving forward, but ZVI will help protect the wellfield from contaminants in the groundwater.

Through monitoring. We expect to see concentrations of chemicals continue to decrease.

Based on the successful treatment of sites across the country, we expect to start seeing positive results in weeks. As designed, the EPA-supervised treatment is anticipated to show a reduction in concentration levels by early summer. Robust testing will continue to ensure drinking water remains safe.

The area has been designated as a Superfund site, which means EPA procedures and requirements govern investigations, cleanup standards, monitoring and remedial actions. Based upon work performed to date, we have identified effective, proven technologies that can be employed immediately.

The remediation actions Ameren Missouri will continue to take are the quickest and most effective methods to protect drinking water. It is also the approach that would promote cleaner groundwater—an approach not achieved through moving a well. Installing a new water supply well is not necessarily a simple or easy process that can be implemented quickly. Doing so does not solve the current groundwater issue. Ameren’s solution cleans the groundwater and ensures a safe drinking water supply, now and into the future, for the City.

Drinking water is safe for public use. We understand that the City has a desire to upgrade its infrastructure, but the ground water issues can be addressed quickly and effectively through containment and treatment. EPA has repeatedly advised the City that a new well field is not necessary. Once approved by EPA, the remediation techniques can be employed in short order and the effects will be virtually immediate. Ameren's proposed corrective action measures are expected to provide both an immediate and effective solution.

The EPA adds:
The City made decisions based on operational preference to shut down City Wells 5, 7, 8, and 9 due to detections of DCE and VC that were much less than the MCLs. The City is entitled to make such decisions as the operator of the permitted public water supply system, but EPA did not request that the City stop pumping those wells.

By law, any environmental remedy must comply with the requirements of a federal regulation known as the National Contingency Plan (NCP). It's the government's blueprint for responding to these types of situations. Under the NCP, a chosen remedy must improve the environment while accomplishing several objectives, including the removal or reduction of contaminants in the environment in a manner that is more efficient than other potential options. Simply moving the wells does not accomplish those objectives and Ameren does not believe such an approach complies with NCP requirements which are mandatory regulatory standards that must be followed.

The EPA adds:
EPA has not requested Ameren to replace public water system wells at this time, but well replacement will be an option EPA expects Ameren to consider in their review of remedial options at the site. The City’s decision to purchase remediation equipment would be based on its operational preference vs. a specific EPA requirement due to contaminant levels entering the treatment plant. MoDNR can provide additional information regarding public water system requirements. EPA’s priorities are ensuring the City’s drinking water meets drinking water standards and restoring the aquifer. EPA is working with Ameren to ensure the contamination is addressed in a manner that is timely and effective in allowing the City to continue use of existing infrastructure.