Public water system · OR4100543
ActiveMosier, City of
At a glance
City of Mosier (PWSID OR4100543) is an active community water system in Wasco County, Oregon. It reports serving 468 people through 217 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, none is health-based, and the most recent began in February 2026.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
468
Service connections
217
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does City of Mosier compare with other water systems in Wasco County?
By EPA's size categories, City of Mosier is a very small system (500 people or fewer). Wasco County has 44 active public water systems. Its population served is about 20% below the county average of 583 people per system, and accounts for 1.8% of the 25,664 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 Mosier is well below 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. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 2,175 Oregon systems (86%) list groundwater as their primary source.
Who owns and regulates City of Mosier?
EPA lists City of Mosier 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. 14 of the 44 active systems in Wasco County (32%) are also owned by a local government.
Does City of Mosier have drinking water violations?
Of the 12 most recent violations in EPA's records, none is health-based, and the most recent began in February 2026. The violations listed here began between July 2024 and February 2026. By type: 11 monitoring and 1 monitoring and reporting. The contaminant or rule involved most often is Revised Total Coliform Rule (11 of them). EPA lists 10 as resolved, 1 as archived and 1 as unaddressed. 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. Archived means the violation was not marked resolved but is more than five years past the end of the noncompliance period, so it no longer counts toward current compliance status. Unaddressed means the violation is not resolved or archived and is not yet covered by formal enforcement.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2026-02-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Archived |
| 2025-12-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2025-03-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2025-02-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2025-01-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2024-12-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2024-11-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2024-10-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2024-10-01 | Monitoring and reportingFollow-up Or Routine LCR Tap M/R · code 52 | Lead and Copper Rulecode 5000 | No | Unaddressed |
| 2024-09-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2024-08-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2024-07-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | 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 Mosier: frequently asked questions
Who runs City of Mosier?
City of Mosier (PWSID OR4100543) 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 Mosier serve?
City of Mosier reports serving 468 people through 217 service connections in Wasco County, Oregon.
Where does City of Mosier 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 City of Mosier 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 February 2026. 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 Mosier'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 February 2026. 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 Mosier's water quality report?
As a community water system, City of Mosier 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 Wasco County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| The Dalles, City of | Wasco | 13,010 | Community | Surface water |
| Chenowith PUD | Wasco | 4,500 | Community | Groundwater |
| Barlow Water District | Wasco | 900 | Community | Groundwater |
| Ote Memaloose Rest Area | Wasco | 800 | Transient non-community | Groundwater |
| Dufur, City of | Wasco | 610 | Community | Groundwater |
| Young Life | Wasco | 497 | Community | Surface water |
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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, “Mosier, City of, PWSID OR4100543, Oregon”, https://aquacensus.com/water-systems/oregon/mosier-city-of-or4100543 (data as of October 1, 2026).