Community Water System · PWS 090605004
Grindstone Rancheria
Elk Creek, EPA Region 9 — Tribal Water Systems 95939 - drinking water served from surface water sources to 150 people, tracked in EPA SDWIS and UCMR5.
- 150
- People served
- 1,214
- EPA violations
- 210
- Health-based
- Untested
- UCMR5 result
The verdict
EPA records 1,214 drinking-water violations at Grindstone Rancheria, 17% of them health-based.
- 1,214
- Total EPA violations on record
- 17%
- Health-based (MCL / treatment failure)
- 150
- People served by this system
- N/A
- PFAS compounds detected (UCMR5)
Water Quality Snapshot: Grindstone Rancheria
Grindstone Rancheria is a native american-owned community water system that delivers drinking water to 150 residents in Elk Creek, EPA Region 9 — Tribal Water Systems through 58 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 1,214 total violations for this system , of which 210 (17%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 705 monitoring and reporting violations are on file. The most recent violation on record dates to 2025.
The most frequently cited contaminant at this system is Surface Water Treatment Rule, recorded in 174 violations (MR). This system has not yet been sampled under EPA's UCMR5 PFAS monitoring program, so no PFAS detection data is available here.
EPA Region 9 — Tribal Water Systems has thousands of regulated public water systems tracked by EPA under the Safe Drinking Water Act.
All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.
System Details
- System Type
- Community
- Owner Type
- Native American
- Connections
- 58
- School/Daycare
- No
- MCL Violations
- 17
- Monitoring Violations
- 705
- Treatment Tech Violations
- 193
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Surface Water Treatment Rule | MR | 174 | 2025 |
| Surface Water Treatment Rule | TT | 174 | 2024 |
| Public Notice | Other | 130 | 2024 |
| Coliform (TCR) | MR | 58 | 2016 |
| Revised Total Coliform Rule | MON | 36 | 2025 |
| Consumer Confidence Rule | Other | 27 | 2024 |
| Revised Total Coliform Rule | MCL | 14 | 2022 |
| Nitrate | MR | 13 | 2024 |
| Revised Total Coliform Rule | TT | 12 | 2022 |
| Chlorine | MR | 8 | 2025 |
| Interim Enhanced Surface Water Treatment Rule | MR | 8 | 2009 |
| BHC-GAMMA | MR | 7 | 2020 |
| Methoxychlor | MR | 7 | 2020 |
| Toxaphene | MR | 7 | 2020 |
| Carbofuran | MR | 7 | 2020 |
| Atrazine | MR | 7 | 2020 |
| LASSO | MR | 7 | 2020 |
| Heptachlor | MR | 7 | 2020 |
| Heptachlor epoxide | MR | 7 | 2020 |
| 2,4-D | MR | 7 | 2020 |
| 2,4,5-TP | MR | 7 | 2020 |
| Pentachlorophenol | MR | 7 | 2020 |
| cis-1,2-Dichloroethylene | MR | 7 | 2020 |
| Total Polychlorinated Biphenyls (PCB) | MR | 7 | 2020 |
| 1,2-DIBROMO-3-CHLOROPROPANE | MR | 7 | 2020 |
| ETHYLENE DIBROMIDE | MR | 7 | 2020 |
| Xylenes, Total | MR | 7 | 2020 |
| Chlordane | MR | 7 | 2020 |
| o-Dichlorobenzene | MR | 7 | 2020 |
| p-Dichlorobenzene | MR | 7 | 2020 |
Verify This Water System
The figures above are aggregated from EPA's public databases. To verify the underlying records, or to file a complaint, request a Consumer Confidence Report, or check current monitoring status, go directly to the federal and state regulators that enforce the Safe Drinking Water Act for Grindstone Rancheria.
EPA SDWIS, Federal Reports
EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:
View PWS ID 090605004 on SDWISSource: EPA SDWIS Federal Reports Search
EPA Region 9 — Tribal Water Systems Drinking Water Authority
EPA Region 9 — Tribal Water Systems's primacy agency administers the Safe Drinking Water Act locally. Search EPA SDWIS for the current state contact, or use the state's public health or environment department portal.
Find 09 regulator via EPA SDWISViolation Timeline
Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.
| Year (latest) | Contaminant | Category | Count | EPA Record |
|---|---|---|---|---|
| 2025 | Surface Water Treatment Rule | MR | 174 | SDWIS / 090605004 / 0200 |
| 2025 | Revised Total Coliform Rule | MON | 36 | SDWIS / 090605004 / 8000 |
| 2025 | Chlorine | MR | 8 | SDWIS / 090605004 / 0999 |
| 2024 | Surface Water Treatment Rule | TT | 174 | SDWIS / 090605004 / 0200 |
| 2024 | Public Notice | Other | 130 | SDWIS / 090605004 / 7500 |
| 2024 | Consumer Confidence Rule | Other | 27 | SDWIS / 090605004 / 7000 |
| 2024 | Nitrate | MR | 13 | SDWIS / 090605004 / 1040 |
| 2024 | Total Haloacetic Acids (HAA5) | MR | 7 | SDWIS / 090605004 / 2456 |
| 2024 | TTHM | MR | 7 | SDWIS / 090605004 / 2950 |
| 2023 | Long Term 2 Enhanced Surface Water Treatment Rule | Other | 4 | SDWIS / 090605004 / 0800 |
| 2022 | Revised Total Coliform Rule | MCL | 14 | SDWIS / 090605004 / 8000 |
| 2022 | Revised Total Coliform Rule | TT | 12 | SDWIS / 090605004 / 8000 |
| 2022 | Stage 1 Disinfectants and Disinfection Byproducts Rule | TT | 3 | SDWIS / 090605004 / 0400 |
| 2020 | BHC-GAMMA | MR | 7 | SDWIS / 090605004 / 2010 |
| 2020 | Methoxychlor | MR | 7 | SDWIS / 090605004 / 2015 |
How Grindstone Rancheria Compares
Cross-reference this system's record against state averages and the federal MCL framework for context.
| Metric | Grindstone Rancheria | EPA Region 9 — Tribal Water Systems avg | Federal benchmark |
|---|---|---|---|
| Total violations | 1,214 | - | SDWA compliance, any non-zero count is a recorded breach |
| Health-based violations | 210 | - | Indicates a contaminant exceeded a federal MCL |
| PFAS detection | None | - | EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt |
| Population served | 150 | - | Sizing context for compliance burden |
Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across all regulated public water systems in EPA Region 9 — Tribal Water Systems.
Federal MCL reference, Safe Drinking Water Act thresholds ▼
| Contaminant | Federal MCL / Action Level | Note |
|---|---|---|
| Lead | 0 mg/L (Action Level: 0.015 mg/L) | Lead and Copper Rule treatment technique |
| Arsenic | 0.010 mg/L (10 ppb) | Health-based MCL since 2006 |
| Total Coliform | Treatment technique (RTCR) | Indicator organism, monitoring trigger |
| PFOA / PFOS (PFAS) | 4.0 ppt each (final 2024 rule) | Compliance deadline 2029 (EPA proposed extending to 2031, not yet final as of May 2026) |
| Nitrate (as N) | 10 mg/L | Acute health risk for infants |
Frequently Asked Questions
Is Grindstone Rancheria water safe to drink? ▼
How many people does Grindstone Rancheria serve? ▼
What type of violations does Grindstone Rancheria have? ▼
Has PFAS been detected in Grindstone Rancheria water? ▼
What water source does Grindstone Rancheria use? ▼
Where does this data come from? ▼
Read our methodology - how this data is sourced, computed, and verified.
Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This system's figures are rendered directly from EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.