St Charles County Public Water Supply District 2 water quality
O'Fallon, MO · serves 100,587 people (39,978 connections) · Purchased surface water · Local government · EPA ID MO6024530
Data: U.S. EPA · How we read the data · How we check it
Buys water from St Louis City Public Water System. Treated water bought from another system can carry that system's contaminants.
Summary
No federal limits exceeded in EPA data.
- PFAS
- Detected, below limit1 of 29 PFAS found at least once. All averages below the federal limits.
- Lithium
- Above screening levelHighest result 47.5 ppb. EPA uses 10 ppb to decide what to study further. It is not a health limit, and there is no federal limit for lithium. About 1 in 4 systems tested were above it.
- Lead
- Below action level2.28 ppb (parts per billion) at the 90th percentile: 9 in 10 homes sampled were at or below it. Action level 15 ppb, falling to 10 ppb in Nov 2027. Monitoring period ending Jun 2026. Your home's pipes can make yours higher.
- Violations
- None health-basedNo health-based violations since 2016.
- Built before 1986, or not sure what your service line is made of? Check your service line and test your tap. Utility data can't show your pipes.
- Tested your own tap? Compare your result with these numbers. Moving? Compare this system with another.
- Read St Charles County Public Water Supply District 2's annual water quality report (Consumer Confidence Report). It lists every regulated contaminant tested and is usually on the utility's website or mailed with your bill, and you can also request it at (636) 385-5197. EPA: how to find it.
PFAS (“forever chemicals”)
EPA UCMR 5: 4 entry points tested Apr 2024 to Jan 2025. "Average" is the highest entry-point average (non-detects counted as zero), the way EPA compares UCMR 5 results to the limits. ppt = parts per trillion. These results do not determine compliance.
| Contaminant | Highest average |
|---|---|
| PFOA Not detected Limit 4 ppt | – |
| PFOS Not detected Limit 4 ppt | – |
| PFHxS Not detected Limit 10 ppt | – |
| PFNA Not detected Limit 10 ppt | – |
| HFPO-DA (GenX) Not detected Limit 10 ppt | – |
| Hazard Index (a combined score for PFHxS, PFNA, GenX and PFBS, where above 1 is over the limit) Not detected Limit 1 | – |
| PFBS Not detected Guideline 2,000 ppt | – |
| PFBA Detected, below limit Guideline 6,000 ppt | 3.25 ppt |
| PFHxA Not detected Guideline 3,000 ppt | – |
29 PFAS tested, 1 detected at least once. "Not detected" means below EPA's reporting limit (about 2 to 20 ppt depending on the chemical), not proven zero. PFAS not listed were not detected. The limits for PFHxS, PFNA, GenX and the Hazard Index were proposed for rescission in May 2026. That proposal is not final. Systems have until 2029 to meet the limits.
Lithium
Detected in 9 of 9 samples. Highest result 47.5 ppb. EPA's non-enforceable screening level is 10 ppb. Above screening level The screening level is how EPA decides what to study further, not a health limit. There is no federal limit for lithium and no filter is certified to remove it. About lithium.
Lead and copper
Latest 90th percentile: 2.28 ppb lead (Jan 2026 – Jun 2026). Below action level
| Monitoring period | Lead (90th pct.) |
|---|---|
| Jan 2026 – Jun 2026 | 2.28 ppb |
| Jan 2023 – Dec 2025 | 0 ppb |
| Jan 2020 – Dec 2022 | 1.14 ppb |
Earlier results (9)
| Jan 2017 – Dec 2019 | 1.29 ppb |
| Jan 2014 – Dec 2016 | 1.03 ppb |
| Jan 2011 – Dec 2013 | 1.4 ppb |
| Jan 2008 – Dec 2010 | 2.84 ppb |
| Jan 2005 – Dec 2007 | 2.02 ppb |
| Jan 2004 – Dec 2004 | 2.14 ppb |
| Jan 2001 – Dec 2001 | 13 ppb |
| Jan 1996 – Dec 1998 | 6.2 ppb |
| Jan 1995 – Dec 1995 | 6 ppb |
Lead comes from pipes and fixtures, not the source water, so it varies home to home. The 90th percentile means 9 in 10 sampled homes were at or below it. More on lead.
Violations
Health-based violations mean a contaminant exceeded a limit or a required treatment step was missed. Monitoring and reporting violations mean required tests or reports were late or missing, so the water's quality during that time is unknown. The total includes every violation in EPA's records, most of them paperwork.
Earlier EPA testing (2013–2020)
| Contaminant | Highest | Guideline |
|---|---|---|
| Manganese | 4.5 ppb | 300 ppb |
| Vanadium | 4.01 ppb | 21 ppb |
| Molybdenum | 4.51 ppb | 40 ppb |
| Strontium | 0.29 ppm | 1.5 ppm |
| Chlorate | 421 ppb | 210 ppb |
| Chromium-6 | 2.4 ppb | – |
Where it serves
ZIP codes the system reported serving: 63366, 63368
Nearby utilities
- St Peters Public Water System St. Peters · 6 mi · PFAS above limit
- Missouri American Water – St Louis St Charles Counties St. Charles · 11 mi
- St Charles Public Water System St. Charles · 11 mi
- St Louis City Public Water System St. Louis · 27 mi
- St James Public Water System St. James · 72 mi · PFAS above limit
- City of Columbia Utilities Columbia · 87 mi
Questions
Is St Charles County Public Water Supply District 2 water safe to drink?
St Charles County Public Water Supply District 2 has no health-based violations since 2016. EPA testing found no PFAS above the federal limits. Federal data can't tell you about your own pipes: lead comes from service lines and plumbing, so test your tap if your home was built before 1986. For the official word, read the utility's annual Consumer Confidence Report.
Does St Charles County Public Water Supply District 2 water have PFAS?
Yes. EPA's 2023–2025 testing of St Charles County Public Water Supply District 2 found 1 PFAS at least once. None of the averages were above the federal limits.
What is the lead level in St Charles County Public Water Supply District 2 water?
The most recent 90th-percentile lead result for St Charles County Public Water Supply District 2 is 2.28 ppb, for the period ending Jun 2026. The federal action level is 15 ppb, falling to 10 ppb in November 2027. The 90th percentile means 9 in 10 homes sampled were at or below this number. Individual homes can be higher.
Check these numbers yourself
Every figure on this page comes from public EPA records. You don't have to take our word for it:
- EPA's own report for MO6024530: violations, enforcement and inspections, straight from EPA.
- EPA UCMR 5 data: the PFAS and lithium results (search the file for PWSID MO6024530).
- EPA SDWIS download: the lead results, population and violation records we use.
- The utility's annual water quality report (Consumer Confidence Report): ask St Charles County Public Water Supply District 2 at (636) 385-5197, or see EPA's guide to finding it.
Found something that doesn't match? Tell us and we'll check it against EPA's records. How we check our data.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.