Public water system · 090605004
ActiveGrindstone Rancheria
At a glance
Grindstone Rancheria (PWSID 090605004) is an active community water system in California. It reports serving 150 people through 58 service connections. Its primary water source is surface water, and EPA lists it as Native American-owned. 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
150
Service connections
58
Primary source
SW
Surface water
System type
CWS
Community water system
System record
How does Grindstone Rancheria compare with other water systems in California?
By EPA's size categories, Grindstone Rancheria is a very small system (500 people or fewer). Across California, the 7,479 active systems average 5,706 people each. Nationally, the average active community water system reports serving 6,703 people, so Grindstone Rancheria 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. California has 2,997 active community water systems, 40% of the state's 7,479 active systems. Surface water means the system draws its water from rivers, lakes, streams or reservoirs. 609 California systems (8.1%) list surface water as their primary source.
Who owns and regulates Grindstone Rancheria?
EPA lists Grindstone Rancheria as Native American-owned. The EPA Region 09 is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act.
Does Grindstone Rancheria 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 April 2025 and March 2026. By type: 12 monitoring and reporting. The contaminant or rule involved most often is Surface Water Treatment Rule (12 of them). EPA lists 12 as archived. 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 |
|---|---|---|---|---|
| 2026-03-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Archived |
| 2026-02-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Archived |
| 2026-01-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Archived |
| 2025-12-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Archived |
| 2025-11-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Archived |
| 2025-10-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Archived |
| 2025-09-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Archived |
| 2025-08-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Archived |
| 2025-07-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Archived |
| 2025-06-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Archived |
| 2025-05-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | No | Archived |
| 2025-04-01 | Monitoring and reportingMonitoring of Treatment (SWTR-Filter) · code 36 | Surface Water Treatment Rulecode 0200 | 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.
Grindstone Rancheria: frequently asked questions
Who runs Grindstone Rancheria?
Grindstone Rancheria (PWSID 090605004) is a community water system Native American-owned. It is regulated by the EPA Region 09.
How many people does Grindstone Rancheria serve?
Grindstone Rancheria reports serving 150 people through 58 service connections in California.
Where does Grindstone Rancheria 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 Grindstone Rancheria 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 Grindstone Rancheria'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 EPA Region 09.
Where can I find Grindstone Rancheria's water quality report?
As a community water system, Grindstone Rancheria 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 California
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Los Angeles-City, Dept. of Water & Power | Los Angeles | 3,875,566 | Community | Surface water |
| East Bay MUD | Alameda | 1,442,800 | Community | Surface water |
| San Diego, City of | San Diego | 1,385,379 | Community | Surface water |
| San Jose Water | Santa Clara | 1,039,920 | Community | Surface water |
| Sfpuc City Distribution Division | San Francisco | 848,019 | Community | Purchased surface water |
| Eastern Municipal Wd | Riverside | 666,581 | Community | Purchased 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, “Grindstone Rancheria, PWSID 090605004, California”, https://aquacensus.com/water-systems/california/grindstone-rancheria-090605004 (data as of October 1, 2026).