Public water system · OR4100537
ActiveMonmouth, City of
At a glance
City of Monmouth (PWSID OR4100537) is an active community water system in Polk County, Oregon. It reports serving 11,651 people through 3,027 service connections. Its primary water source is groundwater under influence of surface water, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in January 2023.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
11,651
Service connections
3,027
Primary source
GU
Groundwater under influence of surface water
System type
CWS
Community water system
System record
How does City of Monmouth compare with other water systems in Polk County?
By EPA's size categories, City of Monmouth is a large system (10,001 to 100,000 people). Polk County has 29 active public water systems, and City of Monmouth is the 2nd-largest of them by population served. Its population served is about 6.3 times the county average of 1,851 people per system, and accounts for 22% of the 53,687 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 Monmouth is about 74% above 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 under the influence of surface water is well or spring water that the regulator has found to be affected by nearby surface water, so it is regulated under the surface-water treatment rules. 21 Oregon systems (0.8%) list groundwater under influence of surface water as their primary source.
Who owns and regulates City of Monmouth?
EPA lists City of Monmouth 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 29 active systems in Polk County (28%) are also owned by a local government.
Does City of Monmouth have drinking water violations?
Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in January 2023. The violations listed here began between January 2014 and January 2023. By type: 10 monitoring and reporting, 1 monitoring and 1 required treatment not met. The contaminant or rule involved most often is Surface Water Treatment Rule (5 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 |
|---|---|---|---|---|
| 2023-01-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Total trihalomethanes (TTHM)code 2950 | No | Resolved |
| 2023-01-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Haloacetic acids (HAA5)code 2456 | No | Resolved |
| 2021-08-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Unfilt/GWR) · code 31 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2021-08-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2021-08-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2021-07-01 | Monitoring and reportingInitial, Follow-up, or Routine Source Water M/R · code 56 | Lead and Copper Rulecode 5000 | No | Resolved |
| 2020-04-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2020-04-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Unfilt/GWR) · code 31 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2020-01-01 | Monitoring and reportingInitial, Follow-up, or Routine Source Water M/R · code 56 | Lead and Copper Rulecode 5000 | No | Resolved |
| 2015-11-02 | Required treatment not metFailure to Filter (SWTR) · code 42 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
| 2014-02-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Unfilt/GWR) · code 31 | Groundwater Rulecode 0700 | No | Resolved |
| 2014-01-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Haloacetic acids (HAA5)code 2456 | 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 Monmouth: frequently asked questions
Who runs City of Monmouth?
City of Monmouth (PWSID OR4100537) 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 Monmouth serve?
City of Monmouth reports serving 11,651 people through 3,027 service connections in Polk County, Oregon.
Where does City of Monmouth get its water?
EPA SDWIS lists this system's primary water source as groundwater under influence of surface water. Groundwater under the influence of surface water is well or spring water that the regulator has found to be affected by nearby surface water, so it is regulated under the surface-water treatment rules.
Does City of Monmouth have any drinking water violations?
Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in January 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 Monmouth'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, one is health-based, and the most recent began in January 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 Monmouth's water quality report?
As a community water system, City of Monmouth 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 Polk County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Dallas, City of | Polk | 17,911 | Community | Surface water |
| Independence Water System | Polk | 10,300 | Community | Groundwater |
| Luckiamute Domestic Water Coop | Polk | 2,738 | Community | Purchased surface water |
| Perrydale Domestic Wtr Assn | Polk | 2,655 | Community | Groundwater |
| Grand Ronde Community Wtr Assn | Polk | 2,500 | Community | Groundwater |
| Rickreall Water Association | Polk | 1,650 | 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, “Monmouth, City of, PWSID OR4100537, Oregon”, https://aquacensus.com/water-systems/oregon/monmouth-city-of-or4100537 (data as of October 1, 2026).