Public water system · WA5374270
ActiveRosario
At a glance
Rosario (PWSID WA5374270) is an active community water system in San Juan County, Washington. It reports serving 1,426 people through 367 service connections. Its primary water source is surface water, and EPA lists it as privately owned. Of the 12 most recent violations in EPA's records, 3 are health-based, and the most recent began in October 2010.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
1,426
Service connections
367
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Rosario compare with other water systems in San Juan County?
By EPA's size categories, Rosario is a small system (501 to 3,300 people). San Juan County has 112 active public water systems. Its population served is about 4 times the county average of 361 people per system, and accounts for 3.5% of the 40,377 people reported by systems filed under the county. Across Washington, the 4,705 active systems average 2,172 people each. Nationally, the average active community water system reports serving 6,703 people, so Rosario 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. Washington has 2,392 active community water systems, 51% of the state's 4,705 active systems. Surface water means the system draws its water from rivers, lakes, streams or reservoirs. 140 Washington systems (3%) list surface water as their primary source.
Who owns and regulates Rosario?
EPA lists Rosario as privately owned. The WA state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 92 of the 112 active systems in San Juan County (82%) are also privately owned.
Does Rosario have drinking water violations?
Of the 12 most recent violations in EPA's records, 3 are health-based, and the most recent began in October 2010. The violations listed here began between January 2004 and October 2010. By type: 9 monitoring and reporting and 3 required treatment not met. The contaminant or rule involved most often is Surface Water Treatment Rule (4 of them). EPA lists 10 as resolved and 2 as archived. 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.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2010-10-01 | Monitoring and reportingMonitoring, Regular · code 03 | Asbestoscode 1094 | No | Resolved |
| 2010-07-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 2010-07-01 | Monitoring and reportingMonitoring, Regular · code 03 | Asbestoscode 1094 | No | Resolved |
| 2010-06-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Resolved |
| 2008-10-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Archived |
| 2005-06-01 | Required treatment not metTreatment Technique (SWTR and GWR) · code 41 | Surface Water Treatment Rulecode 0200 | Yes | Archived |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | trans-1,2-Dichloroethylenecode 2979 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | 1,1-Dichloroethylenecode 2977 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | o-Dichlorobenzenecode 2968 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Chlorobenzenecode 2989 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Benzenecode 2990 | No | Resolved |
| 2004-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Tetrachloroethylenecode 2987 | 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.
Rosario: frequently asked questions
Who runs Rosario?
Rosario (PWSID WA5374270) is a community water system privately owned. It is regulated by the WA state drinking water program.
How many people does Rosario serve?
Rosario reports serving 1,426 people through 367 service connections in San Juan County, Washington.
Where does Rosario 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 Rosario have any drinking water violations?
Of the 12 most recent violations in EPA's records, 3 are health-based, and the most recent began in October 2010. 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 Rosario'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, 3 are health-based, and the most recent began in October 2010. For current results, consult the system's annual water quality report, EPA ECHO, or the WA state drinking water program.
Where can I find Rosario's water quality report?
As a community water system, Rosario 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 San Juan County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Moran State Park-Mountain Lake | San Juan | 4,804 | Transient non-community | Surface water |
| Moran State Park - Summit Lake | San Juan | 4,803 | Transient non-community | Groundwater under influence of surface water |
| Moran State Park-Cascade Lake | San Juan | 4,783 | Transient non-community | Surface water |
| Eastsound Water Users Association | San Juan | 3,711 | Community | Surface water |
| Friday Harbor Town of | San Juan | 3,543 | Community | Surface water |
| Limekiln State Park | San Juan | 2,149 | 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, “Rosario, PWSID WA5374270, Washington”, https://aquacensus.com/water-systems/washington/rosario-wa5374270 (data as of October 1, 2026).