Public water system · MO6010588
ActiveOfallon Pws
At a glance
Ofallon Pws (PWSID MO6010588) is an active community water system in St. Charles County, Missouri. It reports serving 32,515 people through 13,527 service connections. Its primary water source is purchased surface water, and EPA lists it as owned by a local government. EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in June 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
32,515
Service connections
13,527
Primary source
SWP
Purchased surface water
System type
CWS
Community water system
System record
How does Ofallon Pws compare with other water systems in St. Charles County?
By EPA's size categories, Ofallon Pws is a large system (10,001 to 100,000 people). St. Charles County has 54 active public water systems, and Ofallon Pws is the 5th-largest of them by population served. Its population served is about 5.5 times the county average of 5,867 people per system, and accounts for 10% of the 316,837 people reported by systems filed under the county. Across Missouri, the 2,943 active systems average 2,049 people each. Nationally, the average active community water system reports serving 6,703 people, so Ofallon Pws is about 4.9 times that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. Missouri has 1,612 active community water systems, 55% of the state's 2,943 active systems. Purchased surface water means the system buys surface water from another public water system rather than drawing its own. 179 Missouri systems (6.1%) list purchased surface water as their primary source.
Who owns and regulates Ofallon Pws?
EPA lists Ofallon Pws as owned by a local government. The MO state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 20 of the 54 active systems in St. Charles County (37%) are also owned by a local government.
Does Ofallon Pws have drinking water violations?
EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in June 2025. The violations listed here began between June 1991 and June 2025. By type: 1 monitoring and reporting and 1 contaminant level above the legal limit. The contaminants or rules involved are Groundwater Rule and Total coliform bacteria (TCR). EPA lists 1 as resolved and 1 as archived. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed. Archived means the violation was not marked resolved but is more than five years past the end of the noncompliance period, so it no longer counts toward current compliance status.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2025-06-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Unfilt/GWR) · code 31 | Groundwater Rulecode 0700 | No | Resolved |
| 1991-06-25 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Archived |
All 2 violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
Ofallon Pws: frequently asked questions
Who runs Ofallon Pws?
Ofallon Pws (PWSID MO6010588) is a community water system owned by a local government. It is regulated by the MO state drinking water program.
How many people does Ofallon Pws serve?
Ofallon Pws reports serving 32,515 people through 13,527 service connections in St. Charles County, Missouri.
Where does Ofallon Pws get its water?
EPA SDWIS lists this system's primary water source as purchased surface water. Purchased surface water means the system buys surface water from another public water system rather than drawing its own.
Does Ofallon Pws have any drinking water violations?
EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in June 2025. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is Ofallon Pws' water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. EPA's records list 2 violations for this system; 1 is health-based, and the most recent began in June 2025. For current results, consult the system's annual water quality report, EPA ECHO, or the MO state drinking water program.
Where can I find Ofallon Pws' water quality report?
As a community water system, Ofallon Pws must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in St. Charles County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| St Charles County Pwsd 2 | St. Charles | 100,587 | Community | Purchased surface water |
| St Charles Pws | St. Charles | 78,961 | Community | Purchased surface water |
| St Peters Pws | St. Charles | 52,575 | Community | Purchased surface water |
| Wentzville Pws | St. Charles | 41,784 | Community | Groundwater |
| St Paul Pws | St. Charles | 1,700 | Community | Groundwater |
| Orchard Farm Schools | St. Charles | 1,600 | Non-transient non-community | Groundwater |
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About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “Ofallon Pws, PWSID MO6010588, Missouri”, https://aquacensus.com/water-systems/missouri/ofallon-pws-mo6010588 (data as of October 1, 2026).