Public water system · IA1700854
ActiveFour Oaks (Mason City)
At a glance
Four Oaks (Mason City) (PWSID IA1700854) is an active non-transient non-community water system in Cerro Gordo County, Iowa. It reports serving 38 people through 5 service connections. Its primary water source is groundwater, and EPA lists it as owned by a state government. EPA's records list one violation for this system; it is not health-based, and the most recent began in January 2004.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
38
Service connections
5
Primary source
GW
Groundwater
System type
NTNCWS
Non-transient non-community water system
System record
How does Four Oaks (Mason City) compare with other water systems in Cerro Gordo County?
By EPA's size categories, Four Oaks (Mason City) is a very small system (500 people or fewer). Cerro Gordo County has 34 active public water systems. Its population served is well below the county average of 1,173 people per system, and accounts for less than 0.1% of the 39,879 people reported by systems filed under the county. Across Iowa, the 1,828 active systems average 1,718 people each. Nationally, the average active non-transient non-community water system reports serving 430 people, so Four Oaks (Mason City) is well below that figure.
What does “non-transient non-community water system” mean?
A non-transient non-community water system regularly serves at least 25 of the same people for more than six months a year, but not where they live. Schools, factories, office buildings and hospitals with their own supply are typical examples. Iowa has 118 active non-transient non-community water systems, 6.5% of the state's 1,828 active systems. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 1,502 Iowa systems (82%) list groundwater as their primary source.
Who owns and regulates Four Oaks (Mason City)?
EPA lists Four Oaks (Mason City) as owned by a state government. The IA state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 1 of the 34 active systems in Cerro Gordo County (2.9%) are also owned by a state government.
Does Four Oaks (Mason City) have drinking water violations?
EPA's records list one violation for this system; it is not health-based, and the most recent began in January 2004. By type: 1 monitoring and reporting. The contaminant or rule involved is Chlorine. EPA lists 1 as resolved. 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.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2004-01-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Chlorinecode 0999 | No | Resolved |
The one violation in EPA's records.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.
Four Oaks (Mason City): frequently asked questions
Who runs Four Oaks (Mason City)?
Four Oaks (Mason City) (PWSID IA1700854) is a non-transient non-community water system owned by a state government. It is regulated by the IA state drinking water program.
How many people does Four Oaks (Mason City) serve?
Four Oaks (Mason City) reports serving 38 people through 5 service connections in Cerro Gordo County, Iowa.
Where does Four Oaks (Mason City) get its water?
EPA SDWIS lists this system's primary water source as groundwater. Groundwater means the system draws its water from wells or springs fed by underground aquifers.
Does Four Oaks (Mason City) have any drinking water violations?
EPA's records list one violation for this system; it is not health-based, and the most recent began in January 2004. 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 Four Oaks (Mason City)'s 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 one violation for this system; it is not health-based, and the most recent began in January 2004. For current results, consult EPA ECHO, or the IA state drinking water program.
Where can I find Four Oaks (Mason City)'s water quality report?
The annual Consumer Confidence Report requirement applies to community water systems. Four Oaks (Mason City) is a non-transient non-community water system, so it is not required to publish one; like every public water system, it must notify the people it serves about violations under EPA's public notification rules.
Other water systems in Cerro Gordo County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Mason City Water Department | Cerro Gordo | 27,338 | Community | Groundwater |
| Clear Lake Water Department | Cerro Gordo | 7,687 | Community | Groundwater |
| Rockwell Water Supply | Cerro Gordo | 1,071 | Community | Groundwater |
| Ventura Water Works | Cerro Gordo | 716 | Community | Groundwater |
| Thornton Water Supply | Cerro Gordo | 400 | Community | Groundwater |
| Plymouth Water Supply | Cerro Gordo | 378 | 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, “Four Oaks (Mason City), PWSID IA1700854, Iowa”, https://aquacensus.com/water-systems/iowa/four-oaks-mason-city-ia1700854 (data as of October 1, 2026).