Public water system record
Ofallon PWS
Serves O'Fallon, St. Charles County, MO · 32,515 people served
Federal records show no health-based violations and 1 monitoring/reporting issue for Ofallon PWS in the last ten years.
System profile
- Health-based violations, last 10 years
- 0
- Resolved
- 0
- Unresolved
- 0
- Any acute record
- No
- Monitoring issues, last 10 years
- 1
Key facts
- Ofallon PWS draws water from 11 wells (2 of them for emergency, seasonal or other part-time use).
- Record on file since 1991, with 1 health-based violation before October 19, 2016.
- Lead pipe inventory: 0 lead and 13,001 unknown out of 13,821 service lines.
Check whether Ofallon PWS serves your address
Health-based violations
Since October 2016Violation data reflects EPA records through March 2026. For the most current status, visit the EPA ECHO database.
None since October 2016.
Monitoring and reporting issues
Since October 2016Missed tests or reports, not contaminants found above a limit.
| Issue | Start date | Status |
|---|---|---|
|
Groundwater Rule
Monitoring and reporting
|
Jun 1, 2025 | Resolved |
Full record since 1991
EPA's records for Ofallon PWS go back to 1991. Before October 19, 2016 they list 1 health-based violation (1 archived by EPA without a recorded fix) and no monitoring or reporting violations.
| Violations that began in | Health-based | Monitoring and reporting |
|---|---|---|
| 1990s | 1 | 0 |
| 2020s | 0 | 1 |
Most recent health-based violation before October 19, 2016: Total Coliform, began June 1991, Archived.
Show the health-based violation before October 19, 2016
| Contaminant | Start date | Status |
|---|---|---|
|
Total Coliform
Contaminant limit exceeded
|
Jun 25, 1991 | Archived |
Where the water comes from
Ofallon PWS draws water from 11 wells (2 of them for emergency, seasonal or other part-time use). It also buys water from St Charles County PWSD 2 and MO American St Louis St Charles Counties. It also has an emergency connection to Wentzville PWS. 1 other community water system and 1 smaller public system such as schools, businesses or campgrounds buy water from Ofallon PWS.
Buys water from
- St Charles County PWSD 2 O'Fallon, MO
- MO American St Louis St Charles Counties Chesterfield, MO
Emergency or part-time connections to
- Wentzville PWS Wentzville, MO
Community systems that buy water from it
- Tara Oaks Manor Assn St Paul, MO
Annual water quality report
Ofallon PWS must give its customers an annual water quality report (Consumer Confidence Report) by July 1, with the levels its tests found in the previous year.
Systems serving 10,000 or more people must mail or deliver the report to every customer, and from 2027 they must send it twice a year.
Find a posted report with EPA's Consumer Confidence Report search
Testing your own water
To test the water at your tap, or a private well this record does not cover, use a laboratory certified for drinking water by Missouri.
Certified drinking water labs by state EPA guidance for private wells