Community Water System · PWS 090605004
Grindstone Rancheria
Operator location Elk Creek, EPA Region 9 — Tribal Water Systems - smaller served population (≤ 999) at 150 people served; 1,214 SDWIS violations on record from surface water sources.
- 150
- People served (this PWS) Smaller third of systems
- 1,214
- EPA violations (this PWS) Upper third of systems
- 210
- Health-based (this PWS) Middle third by health-based share
- Untested
- UCMR5 (this PWS) No UCMR5 result
Grindstone Rancheria standing, high SDWIS violation third
150 people served (SDWIS) - smaller served population (≤ 999). Corpus terciles use 29,740 systems serving 500+ (the sitemap cohort). Health-based share 17% is middle-third health share (≤ 23%).
The verdict
Grindstone Rancheria sits in the upper third of the sitemap cohort by violation count (1,214), so the tables below sample a dense compliance trail rather than a near-clean ledger. Population served is smaller (150; smaller served population (≤ 999)), so each violation row represents a compact service footprint. Health-based share is 17% (middle-third health share (≤ 23%)). No UCMR5 PFAS test appears for this system in this extract.
- 1,214
- Total EPA violations on record
- 17%
- Health-based (MCL / treatment failure)
- 150
- People served by this PWS (SDWIS)
- N/A
- PFAS compounds detected (UCMR5)
Population ordinals match the sitemap cohort (systems serving 500+, population_served DESC). See methodology · corpus placement.
Based on EPA SDWIS violation history and UCMR5 PFAS testing only, not water taste, odor, infrastructure age, or contaminants outside the federally tracked set.
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 |
Violation Count vs. the National Corpus
Grindstone Rancheria has 1,214 recorded EPA violations, 99% of the 29,740 public water systems serving 500+ people nationwide carry fewer, and 1% carry more. 17% of this system's own violations are health-based (210 of 1,214), and it ranks unranked by population served among that same cohort.
EPA violations vs. the national water-system corpus
Public water systems serving 500+ people (EPA SDWIS)
1,214 Higher than most more violations than 99% of 29,740 water systems
the national water-system corpus, bucketed by value
Each bar is a band; taller bars hold more water systems. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source EPA SDWIS · 2026-05-15
How many violations vs. how serious, among peer systems
Grindstone Rancheria plotted against 29 peer public water systems (500+ people served), by total violation count (x) and the share of those violations that are health-based (y). The crosshair sits at this sample's own median on each axis. A high violation count does not automatically mean a serious record: most monitoring and reporting violations are minor, not health-based.
Violation volume vs. health-based share
Population served record for Grindstone Rancheria
EPA SDWIS lists 150 people served and 58 connections for this PWS, confirm the service-area footprint on the federal report before comparing to municipal census totals.
Sources: EPA SDWIS
Nationwide peers
1,214 violations · 150 served: nearest cross-state SDWIS matches.
Cross-state systems with comparable violation load
Nearest cross-state community systems (500+ served) by total SDWIS violations on record.
What to do with Grindstone Rancheria
Use this system's EPA-reported record as a starting filter, not a final verdict.
- See how every tracked system in EPA Region 9 — Tribal Water Systems compares on the same EPA violation measures. EPA Region 9 — Tribal Water Systems systems
- Check whether PFAS was detected at this system under UCMR5 testing. PFAS guide
- Find and compare another public water system by name or PWSID. Search systems
EPA SDWIS and UCMR5 figures are informational only, not a substitute for a certified lab test of your own tap water.
Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.