O'Fallon
O'Fallon, MO water profile — supply sources, drought status, wastewater reuse, and the key water issues facing the city.
st charles county pwsd 2
surface water (rivers/reservoirs) · local government · PWSID MO6024530
Below EPA's 15 ppb lead action level at last testing.
Source: EPA Safe Drinking Water Information System (SDWIS) · 2026 Q1
O'Fallon is a small but growing city and the 8th-largest in Missouri, home to roughly 85,040 residents. O'Fallon's drinking water comes largely from the same regional sources that serve Missouri: Missouri River, Mississippi River, and Ozark aquifer.
As elsewhere in Missouri, the central challenge is aging infrastructure. Major rivers provide ample supply; aging systems are the main vulnerability.
Missouri reuses an estimated 4% of its treated wastewater and maintains minimal reuse programs; O'Fallon tracks abnormally dry to moderate drought conditions on the U.S. Drought Monitor scale.
Explore the Missouri profile for statewide context, or dig into the water issues shaping O'Fallon below.
St. Charles County water quality
Source: EPA SDWIS · 2026 Q1
At a glance
- Population ~85,040 (8th-largest in Missouri)
- Primary sources: Missouri River, Mississippi River, and Ozark aquifer
- Drought: abnormally dry to moderate conditions
- State reuse rate: ~4% of wastewater
Statewide drought history
% of Missouri in severe+ drought (Moderate (D1) now).
Source: U.S. Drought Monitor
Common questions
Is tap water safe in O'Fallon?
O'Fallon's largest water system, ST CHARLES COUNTY PWSD 2, serves about 100,587 people. EPA records show 0 health-based violation(s) since 2016 and a most-recent 90th-percentile lead level of 0 ppb (EPA action level is 15 ppb). Always check your own provider's annual Consumer Confidence Report.
Where does O'Fallon get its water?
ST CHARLES COUNTY PWSD 2 draws primarily from surface water (rivers/reservoirs), part of Missouri's supply from Missouri River, Mississippi River, Ozark aquifer.
Related water issues
Aging Infrastructure
Much of America's water infrastructure is decades past its design life, leaking trillions of gallons a year and demanding hundreds of billions in reinvestment.
ExploreAgricultural Demand
Agriculture accounts for the majority of consumptive water use in the West, making farm efficiency and water markets central to any supply solution.
Explore