Public water system · WA5305867
ActiveHamma Ridge
At a glance
Hamma Ridge (PWSID WA5305867) is an active community water system in Mason County, Washington. It reports serving 63 people through 28 service connections. Its primary water source is groundwater, and EPA lists it as owned by a local government. EPA's records list 5 violations for this system; none is health-based, and the most recent began in April 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
63
Service connections
28
Primary source
GW
Groundwater
System type
CWS
Community water system
System record
How does Hamma Ridge compare with other water systems in Mason County?
By EPA's size categories, Hamma Ridge is a very small system (500 people or fewer). Mason County has 240 active public water systems. Its population served is well below the county average of 315 people per system, and accounts for less than 0.1% of the 75,633 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 Hamma Ridge 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. Groundwater means the system draws its water from wells or springs fed by underground aquifers. 4,370 Washington systems (93%) list groundwater as their primary source.
Who owns and regulates Hamma Ridge?
EPA lists Hamma Ridge 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. 64 of the 240 active systems in Mason County (27%) are also owned by a local government.
Does Hamma Ridge have drinking water violations?
EPA's records list 5 violations for this system; none is health-based, and the most recent began in April 2025. The violations listed here began between January 2007 and April 2025. By type: 4 monitoring and reporting and 1 monitoring. The contaminant or rule involved most often is Diquat (4 of them). EPA lists 5 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 |
|---|---|---|---|---|
| 2025-04-01 | MonitoringMonitoring, Routine (RTCR) · code 3A | Revised Total Coliform Rulecode 8000 | No | Resolved |
| 2007-10-01 | Monitoring and reportingMonitoring, Regular · code 03 | Diquatcode 2032 | No | Resolved |
| 2007-07-01 | Monitoring and reportingMonitoring, Regular · code 03 | Diquatcode 2032 | No | Resolved |
| 2007-04-01 | Monitoring and reportingMonitoring, Regular · code 03 | Diquatcode 2032 | No | Resolved |
| 2007-01-01 | Monitoring and reportingMonitoring, Regular · code 03 | Diquatcode 2032 | No | Resolved |
All 5 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.
Hamma Ridge: frequently asked questions
Who runs Hamma Ridge?
Hamma Ridge (PWSID WA5305867) is a community water system owned by a local government. It is regulated by the WA state drinking water program.
How many people does Hamma Ridge serve?
Hamma Ridge reports serving 63 people through 28 service connections in Mason County, Washington.
Where does Hamma Ridge 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 Hamma Ridge have any drinking water violations?
EPA's records list 5 violations for this system; none is health-based, and the most recent began in April 2025. 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 Hamma Ridge'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. EPA's records list 5 violations for this system; none is health-based, and the most recent began in April 2025. For current results, consult the system's annual water quality report, EPA ECHO, or the WA state drinking water program.
Where can I find Hamma Ridge's water quality report?
As a community water system, Hamma Ridge 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 Mason County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Shelton City of | Mason | 15,089 | Community | Groundwater |
| Belfair Water District 1 | Mason | 4,432 | Community | Groundwater |
| Lake Cushman System 5 | Mason | 3,675 | Community | Groundwater |
| Twanoh State Park | Mason | 3,173 | Transient non-community | Groundwater |
| Belfair State Park | Mason | 2,411 | Transient non-community | Groundwater |
| Timberlake Community Club Inc. | Mason | 2,337 | 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, “Hamma Ridge, PWSID WA5305867, Washington”, https://aquacensus.com/water-systems/washington/hamma-ridge-wa5305867 (data as of October 1, 2026).