Public water system · WA5311800
ActiveCastle Rock Municipal Water
At a glance
Castle Rock Municipal Water (PWSID WA5311800) is an active community water system in Cowlitz County, Washington. It reports serving 4,367 people through 1,202 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 2026.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
4,367
Service connections
1,202
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Castle Rock Municipal Water compare with other water systems in Cowlitz County?
By EPA's size categories, Castle Rock Municipal Water is a medium system (3,301 to 10,000 people). Cowlitz County has 77 active public water systems, and Castle Rock Municipal Water is the 6th-largest of them by population served. Its population served is about 168% above the county average of 1,628 people per system, and accounts for 3.5% of the 125,351 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 Castle Rock Municipal Water is about 35% 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 Castle Rock Municipal Water?
EPA lists Castle Rock Municipal Water as owned by a local government. 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. 14 of the 77 active systems in Cowlitz County (18%) are also owned by a local government.
Does Castle Rock Municipal Water 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 2026. The violations listed here began between January 2008 and March 2026. By type: 12 monitoring and reporting. The contaminants or rules involved are Surface Water Treatment Rule, Total trihalomethanes (TTHM), Haloacetic acids (HAA5) and 1,2-Dichloroethane. EPA lists 9 as archived and 3 as resolved. 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. 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 |
|---|---|---|---|---|
| 2026-03-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Resolved |
| 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 |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | 1,2-Dichloroethanecode 2980 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Trichloroethylenecode 2984 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | 1,1-Dichloroethylenecode 2977 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | p-Dichlorobenzenecode 2969 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Vinyl chloridecode 2976 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Dichloromethanecode 2964 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Ethylbenzenecode 2992 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Benzenecode 2990 | No | Archived |
| 2008-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | trans-1,2-Dichloroethylenecode 2979 | No | Archived |
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.
Castle Rock Municipal Water: frequently asked questions
Who runs Castle Rock Municipal Water?
Castle Rock Municipal Water (PWSID WA5311800) is a community water system owned by a local government. It is regulated by the WA state drinking water program.
How many people does Castle Rock Municipal Water serve?
Castle Rock Municipal Water reports serving 4,367 people through 1,202 service connections in Cowlitz County, Washington.
Where does Castle Rock Municipal Water 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 Castle Rock Municipal Water 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 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 Castle Rock Municipal Water'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 2026. For current results, consult the system's annual water quality report, EPA ECHO, or the WA state drinking water program.
Where can I find Castle Rock Municipal Water's water quality report?
As a community water system, Castle Rock Municipal Water 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 Cowlitz County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Longview Water Department | Cowlitz | 57,617 | Community | Groundwater |
| Kelso City of | Cowlitz | 15,775 | Community | Groundwater under influence of surface water |
| Beacon Hill Water & Sewer District | Cowlitz | 11,969 | Community | Purchased groundwater |
| Woodland City of | Cowlitz | 10,640 | Community | Groundwater under influence of surface water |
| Kalama City of | Cowlitz | 8,020 | Community | Groundwater under influence of surface water |
| Toutle River Rest Area Nb/Sb | Cowlitz | 3,590 | 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, “Castle Rock Municipal Water, PWSID WA5311800, Washington”, https://aquacensus.com/water-systems/washington/castle-rock-municipal-water-wa5311800 (data as of October 1, 2026).