Ensuring the Safety of St. Charles' Drinking Water

We know St. Charles residents have questions. This website was created to give you answers and is updated regularly.

Is St. Charles water safe to drink?

Yes. According to the U.S. Environmental Protection Agency (EPA): "St. Charles' drinking water supply meets the drinking water health standards established by Missouri's Safe Drinking Water Law and EPA's Safe Drinking Water Act. Water distributed to the public after treatment at the city's water treatment plant has been sampled regularly for VOCs, including vinyl chloride and DCE, since 2008 and has never shown any level of contamination."

Further reading:

EPA Fact Sheet (PDF)

Missouri Department of Natural Resources (PDF)

What's Ameren Missouri doing?

Ameren Missouri is implementing treatment techniques approved by the EPA to contain and remove low level remnants of cleaning solvents used decades ago at the Huster substation in the City of St. Charles. Additional treatment techniques at the substation site began in January and will be followed by a monitoring period. All work is being performed under the supervision of the EPA.

See below for more detail as well as this announcement from Feb. 9, 2023.

November 2023 Update

MDRN issued a report (PDF) which found the groundwater containment system (GCS) at Ameren Missouri's Huster substation in compliance with Missouri's Clean Water Law, Missouri Clean Water Commission Regulations and the state operating permit. A subsequent analysis of the water inspection report shows 100% compliance (PDF) with effluent levels.

The MDNR report and analysis is further supported by a technical memorandum (PDF) that Ameren Missouri shared with the EPA. In concluding that Ameren's various remediation technologies are not having an adverse impact on water quality, a third-party consultant noted, among other findings, a significant reduction in DCE and VC levels reflecting the positive impact of Ameren's remediation efforts.

October 2023 Update

At the EPA's direction, Ameren Missouri commissioned a third-party study investigating ammonia levels in the Elm Point wellfield. The updated report issued in October 2023 evaluated additional sampling data from EPA and found it impossible for ongoing treatment to have a significant impact on water quality or a drop in ammonia levels from City Well 10 (PDF). The City's arguments to the contrary are without technical merit.

September 2023 Update

On Monday September 18, the U.S. Environmental Protection Agency (EPA) instructed the City of St. Charles to cease pumping and dumping water into the sewer from City Well 4 and interfering with the EPA’s and Ameren's ongoing remedial measures. Read the EPA's full letter to the City of St. Charles (PDF).

The decision by the City to use this decades-old, obsolete well for the first time in approximately 20 years in an attempt to undermine remediation activities was irresponsible. For weeks, Ameren Missouri had been warning that the City's unprecedented use of the well will reduce the effectiveness of treatment techniques underway on our property, particularly so because the City was using the well without benefit for the residents of St. Charles.

Once the EPA approves our work plan, Ameren Missouri will install an extraction well that will mitigate those risks. We urge the City to cooperate with, not further hinder, Ameren Missouri's efforts.

It's also important to reiterate that, according to the EPA: "St. Charles' drinking water supply meets the drinking water health standards established by Missouri's Safe Drinking Water Law and EPA's Safe Drinking Water Act. Water distributed to the public after treatment at the city's water treatment plant has been sampled regularly for VOCs, including vinyl chloride and DCE, since 2008 and has never shown any level of contamination."

Ameren Missouri motion to dissolve a temporary restraining order. Filed on Sept. 22, 2023 (PDF).

To help you better understand this issue, we asked some questions of Dr. Ray Ferrara, who has more than thirty years of experience as an educator, scholar and consultant. Dr. Ferrara is well known throughout the United States for his work in solving complex water quality problems involving contamination of ground waters, surface waters, and drinking water supplies.








How our public water systems work.

Frequently Asked Questions

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.

No. The material used has been approved by EPA for remediation purposes and should have no impact on City wells. Monitoring wells will confirm to us that groundwater is not adversely impacted as it leaves the substation.

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.

EPA's investigation provided more details about the exact location of chemicals with respect to the City wells. The chemicals of concern were detected at a handful of locations. Remediation measures proposed by Ameren Missouri will prevent those chemicals from creating unsafe conditions at the City’s wells.
No. EPA, in what is called an Action Memorandum, requested that the Findett PRP Group evaluate the relocation of two City wells along with its evaluation of other remedial measures. That request was later withdrawn by EPA as unnecessary because there are other effective remediation alternatives. EPA has repeatedly advised the City that well replacement is unnecessary.

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.

Questions about Chemicals in Water and Water Provided to Residents through the Tap:

The EPA created an illustration which shows how water reaches our faucets.

Every public water system or community water supplier must provide an annual report, sometimes called a Consumer Confidence Report (CCR), to its customers. The report provides information on local drinking water quality, including the water’s source, contaminants found in the water, and how consumers can help protect their drinking water. In addition, water suppliers must regularly monitor their water supplies and report any transgressions.

View the CCR for St. Charles

The presence of contaminants does not necessarily indicate that water poses a health risk. As the CCR for St. Charles states: Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants.

More Information

Even though U.S. tap water supplies are among the safest in the world, water contamination can still occur. There are many possible sources of contamination, including:

  • Sewage releases
  • Naturally occurring chemicals and minerals (for example, arsenic, radon, uranium)
  • Local land use practices (for example, fertilizers, pesticides, livestock, concentrated feeding operations)
  • Manufacturing processes (for example, heavy metals, cyanide)
  • Malfunctioning on-site wastewater treatment systems (for example, septic systems)
  • Internal home plumbing materials and customer service lines (for example, lead, copper)
  • Municipal water mains and service lines (for example, chemicals, lead, bacteria)

The expectation to have drinking water that is devoid of any chemicals is effectively impossible to achieve. In fact, dissolved minerals (e.g., calcium) in water often enhance its desirability. That is why EPA has defined acceptable levels of various constituents in drinking water. The SDWA, among other very important environmental regulatory programs, help protect our water supplies and work to keep the drinking water safe.

Questions about Treatment and Operations

Water may be treated differently in different communities depending on the quality of the source water that enters the treatment plant. The water that enters the treatment plant is most often either water from lakes, rivers or streams called “surface water” or from ground water. Surface water typically requires more treatment and filtration than ground water because it typically contains more particles and turbidity (e.g., soil particles, leaves, etc.), pathogenic (disease causing) organisms, organic and inorganic chemicals (e.g., iron), and other toxins.

Questions about public health and risk:

The Safe Drinking Water Act (SDWA) was passed by Congress in 1974, with amendments added in 1986 and 1996, to protect our drinking water. Under the SDWA, EPA sets the standards for drinking water quality and monitors states, local authorities, and water suppliers who enforce those standards. As part of the SDWA, EPA has set maximum contaminant levels (MCL), as well as treatment requirements for over 90 different contaminants in public drinking water.

The MCL is the highest level of a chemical that is allowed in drinking water delivered to the public. It is measured as the water flows out of the treatment plant after treatment has occurred and before it is delivered to the residential home tap.

Ameren Missouri is ready to work with the City to optimize the use of its wells and maintain the integrity of the City’s water supply. Such an operating regime would only need to be in place for a limited time until the remediation efforts are fully executed.

The EPA adds:
MCLs are developed based on non-cancer or cancer effects and are defined as “the level at which no known or anticipated adverse effects on the health of persons occur and which allows an adequate margin of safety”.

No less often than every six years, MCLs are evaluated for possible regulatory revision based on health impacts, cost, and technology of prevention or treatment. Any revision of an MCL should present a meaningful opportunity to improve the level of public health protection or achieve cost savings while maintaining or improving the level of public health protection. The six-year review of the MCLs for vinyl chloride (VC) and cis-1,2- Dichloroethylene (DCE) was last completed in 2017 and EPA anticipates completing its current review of these MCLs in 2023. More information is available here: https://www.epa.gov/dwsixyearreview.

Yes. EPA maintains a listing of accomplishments and successful outcomes.
Alert Info