Public water system · IA1750048
ActiveMason City Water Department
At a glance
Mason City Water Department (PWSID IA1750048) is an active community water system in Cerro Gordo County, Iowa. It reports serving 27,338 people through 19,000 service connections. Its primary water source is groundwater, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, 7 are health-based, and the most recent began in June 2024.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
27,338
Service connections
19,000
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Mason City Water Department compare with other water systems in Cerro Gordo County?
By EPA's size categories, Mason City Water Department is a large system (10,001 to 100,000 people). Cerro Gordo County has 34 active public water systems, and Mason City Water Department is the largest of them by population served. Its population served is about 23 times the county average of 1,173 people per system, and accounts for 69% 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 community water system reports serving 6,703 people, so Mason City Water Department is about 4.1 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. Iowa has 1,084 active community water systems, 59% 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 Mason City Water Department?
EPA lists Mason City Water Department as owned by a local 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. 11 of the 34 active systems in Cerro Gordo County (32%) are also owned by a local government.
Does Mason City Water Department have drinking water violations?
Of the 12 most recent violations in EPA's records, 7 are health-based, and the most recent began in June 2024. The violations listed here began between January 2004 and June 2024. By type: 7 contaminant level above the legal limit, 3 monitoring and reporting, 1 monitoring and 1 public notice, recordkeeping or other. The contaminant or rule involved most often is Total coliform bacteria (TCR) (4 of them). EPA lists 12 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 |
|---|---|---|---|---|
| 2024-06-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2012-08-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 2009-07-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Haloacetic acids (HAA5)code 2456 | No | Resolved |
| 2008-06-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 2004-10-01 | Monitoring and reportingMonitoring, Regular · code 03 | Gross alpha (excluding radon and uranium)code 4000 | No | Resolved |
| 2004-10-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2004-08-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 2004-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Complete Failure to Report · code 71 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2004-07-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
| 2004-07-01 | Monitoring and reportingMonitoring, Regular · code 03 | Gross alpha (excluding radon and uranium)code 4000 | No | Resolved |
| 2004-03-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Monthly (TCR) · code 22 | Total coliform bacteria (TCR)code 3100 | Yes | Resolved |
| 2004-01-01 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Single Sample · code 01 | Combined Radium (-226 and -228)code 4010 | Yes | Resolved |
The 12 most recent 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.
Mason City Water Department: frequently asked questions
Who runs Mason City Water Department?
Mason City Water Department (PWSID IA1750048) is a community water system owned by a local government. It is regulated by the IA state drinking water program.
How many people does Mason City Water Department serve?
Mason City Water Department reports serving 27,338 people through 19,000 service connections in Cerro Gordo County, Iowa.
Where does Mason City Water Department 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 Mason City Water Department have any drinking water violations?
Of the 12 most recent violations in EPA's records, 7 are health-based, and the most recent began in June 2024. 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 Mason City Water Department'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. Of the 12 most recent violations in EPA's records, 7 are health-based, and the most recent began in June 2024. For current results, consult the system's annual water quality report, EPA ECHO, or the IA state drinking water program.
Where can I find Mason City Water Department's water quality report?
As a community water system, Mason City Water Department 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 Cerro Gordo County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| 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 |
| Bell Harbor | Cerro Gordo | 352 | 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, “Mason City Water Department, PWSID IA1750048, Iowa”, https://aquacensus.com/water-systems/iowa/mason-city-water-department-ia1750048 (data as of October 1, 2026).