Public water system · OR4100587
ActiveOntario, City of
At a glance
City of Ontario (PWSID OR4100587) is an active community water system in Malheur County, Oregon. It reports serving 14,465 people through 4,082 service connections. Its primary water source is surface water, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in March 2023.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
14,465
Service connections
4,082
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does City of Ontario compare with other water systems in Malheur County?
By EPA's size categories, City of Ontario is a large system (10,001 to 100,000 people). Malheur County has 20 active public water systems, and City of Ontario is the largest of them by population served. Its population served is about 14 times the county average of 1,067 people per system, and accounts for 68% of the 21,335 people reported by systems filed under the county. Across Oregon, the 2,536 active systems average 1,587 people each. Nationally, the average active community water system reports serving 6,703 people, so City of Ontario is about twice 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. Oregon has 940 active community water systems, 37% of the state's 2,536 active systems. Surface water means the system draws its water from rivers, lakes, streams or reservoirs. 211 Oregon systems (8.3%) list surface water as their primary source.
Who owns and regulates City of Ontario?
EPA lists City of Ontario as owned by a local government. The OR state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 8 of the 20 active systems in Malheur County (40%) are also owned by a local government.
Does City of Ontario have drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in March 2023. The violations listed here began between August 2014 and March 2023. By type: 11 monitoring and reporting and 1 monitoring. The contaminant or rule involved most often is Surface Water Treatment Rule (6 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 |
|---|---|---|---|---|
| 2023-03-01 | Monitoring and reportingMonitoring, Turbidity (Enhanced SWTR) · code 38 | Interim Enhanced Surface Water Treatment Rulecode 0300 | No | Resolved |
| 2023-03-01 | Monitoring and reportingMonitoring, Turbidity (Enhanced SWTR) · code 38 | Interim Enhanced Surface Water Treatment Rulecode 0300 | No | Resolved |
| 2023-03-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2023-03-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2023-03-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2023-03-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2023-01-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2015-07-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Haloacetic acids (HAA5)code 2456 | No | Resolved |
| 2015-07-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Total trihalomethanes (TTHM)code 2950 | No | Resolved |
| 2014-08-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2014-08-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2014-08-01 | Monitoring and reportingMonitoring, Turbidity (Enhanced SWTR) · code 38 | Interim Enhanced Surface Water Treatment Rulecode 0300 | No | 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.
City of Ontario: frequently asked questions
Who runs City of Ontario?
City of Ontario (PWSID OR4100587) is a community water system owned by a local government. It is regulated by the OR state drinking water program.
How many people does City of Ontario serve?
City of Ontario reports serving 14,465 people through 4,082 service connections in Malheur County, Oregon.
Where does City of Ontario get its water?
EPA SDWIS lists this system's primary water source as surface water. Surface water means the system draws its water from rivers, lakes, streams or reservoirs.
Does City of Ontario have any drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in March 2023. 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 City of Ontario'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, none is health-based, and the most recent began in March 2023. For current results, consult the system's annual water quality report, EPA ECHO, or the OR state drinking water program.
Where can I find City of Ontario's water quality report?
As a community water system, City of Ontario 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 Malheur County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Nyssa, City of | Malheur | 3,285 | Community | Groundwater |
| Vale, City of | Malheur | 1,837 | Community | Groundwater |
| Fry Foods | Malheur | 280 | Non-transient non-community | Groundwater |
| Oprd Mccormack Cg | Malheur | 250 | Transient non-community | Groundwater |
| Jordan Valley, City of | Malheur | 175 | Community | Groundwater |
| Harper High/Elementary Sd 66 | Malheur | 170 | 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, “Ontario, City of, PWSID OR4100587, Oregon”, https://aquacensus.com/water-systems/oregon/ontario-city-of-or4100587 (data as of October 1, 2026).