States → EPA Region 9 — Tribal Water Systems
State profile · EPA SDWIS + UCMR5
EPA Region 9 — Tribal Water Systems Drinking Water Quality
323 public water systems serve 555,721 people across EPA Region 9 — Tribal Water Systems, with every Safe Drinking Water Act violation and UCMR5 PFAS result on record.
- 323
- Water systems
- 48,296
- Total violations
- 96.6%
- Systems w/ a violation
- 73.2%
- PFAS detection rate
The verdict
Across EPA Region 9 — Tribal Water Systems, 312 of 323 water systems (96.6%) carry at least one EPA violation, and 30 of 41 UCMR5-tested systems show PFAS.
- 48,296
- Total EPA violations on record
- 7%
- Health-based (MCL / treatment)
- 96.6%
- Systems with ≥1 violation
- 73.2%
- UCMR5 PFAS detection rate
Water Systems
323
Total Violations
48,296
Violation Rate
96.6%
PFAS Detection
73.2%
30 of 41 tested
Violation Composition
How EPA Region 9 — Tribal Water Systems's 48,296 violations break down by type, per EPA SDWIS classification.
Health-based (3,354) Monitoring/Reporting (44,942)
| Metric | Value | Share |
|---|---|---|
| Public water systems | 323 | - |
| Population served | 555,721 | - |
| Total violations | 48,296 | 100% |
| Health-based violations | 3,354 | 6.9% |
| Systems with violations | 312 | 96.6% |
| PFAS detection rate | 30 of 41 | 73.2% |
Health-based violations indicate the contaminant exceeded an EPA Maximum Contaminant Level (MCL) or treatment-technique requirement. Monitoring/reporting violations indicate procedural issues (missed tests, late reports) - not necessarily a contamination event.
Largest Water Systems
Pechanga
Temecula, 09 · 29,100 served
Casino Arizona Talking Stick (CATS)
Scottsdale, 09 · 25,785 served
GRIC DPW Wild Horse Pass
Sacaton, 09 · 22,795 served
Salt River Public Works
Scottsdale, 09 · 20,951 served
Thunder Valley Casino
Auburn, 09 · 18,007 served
Morongo
Banning, 09 · 16,000 served
WMATUA Miner Flat
Whiteriver, 09 · 15,570 served
Pala North
Pala, 09 · 14,280 served
Yocha Dehe Potable Water System
Brooks, 09 · 12,800 served
Sycuan
El Cajon, 09 · 12,350 served
Talking Stick Resort
Scottsdale, 09 · 12,087 served
Ak-Chin Village
Maricopa, 09 · 11,646 served
Red Hawk Casino - Shingle Springs
Shingle Springs, 09 · 11,268 served
Table Mountain Rancheria
Friant, 09 · 10,675 served
Casino Arizona
Scottsdale, 09 · 10,603 served
Graton Resort and Casino
Rohnert Park, 09 · 10,127 served
Viejas Community System
Alpine, 09 · 9,600 served
Hard Rock Fire Mountain Water System
Oroville, 09 · 9,500 served
Santa Rosa Tachi Palace
Lemoore, 09 · 9,000 served
Colorado River Regional Water System
Parker, 09 · 8,490 served
Most Violations
#1 Grindstone Rancheria Elk Creek
1,214 #2 Havasupai Village Supai
754 #3 Kaibab Village Pipe Spring
740 #4 Tule River Reservation Main Porterville
662 #5 SCUA Upper Seven Mile San Carlos
659 #6 Quechan Utility Yuma
623 #7 Yurok - Weitchpec Klamath
622 #8 Arizona Village Needles
607 #9 Oasis Mobile Home Park Thermal
564 #10 Yurok - Kepel Klamath
561 #11 Hopi Cultural Center Kykotsmovi
554 #12 Yurok - Wautec Klamath
525 #13 SCUA Bylas San Carlos
516 #14 SCUA Lower Peridot San Carlos
503 #15 Shungopavi Second Mesa
494 Counties in EPA Region 9 — Tribal Water Systems
County 09013
23 systems · 114,768 served
· 2,232 violations
County 09017
18 systems · 47,180 served
· 4,330 violations
County 09073
10 systems · 41,233 served
· 1,205 violations
County 09019
29 systems · 26,556 served
· 2,067 violations
County 09031
23 systems · 19,530 served
· 2,193 violations
County 09061
1 systems · 18,007 served
· 10 violations
County 09025
9 systems · 14,489 served
· 1,501 violations
County 09021
8 systems · 13,612 served
· 500 violations
County 09007
17 systems · 11,319 served
· 4,099 violations
County 09097
2 systems · 10,727 served
· 3 violations
County 09015
10 systems · 9,353 served
· 3,120 violations
County 09027
5 systems · 9,290 served
· 557 violations
County 09012
2 systems · 8,788 served
· 266 violations
County 09005
6 systems · 6,766 served
· 1,625 violations
County 09071
6 systems · 6,234 served
· 478 violations
County 09001
6 systems · 5,960 served
· 512 violations
County 09009
2 systems · 5,245 served
· 531 violations
County 09039
1 systems · 5,000 served
· 9 violations
County 09103
1 systems · 4,782 served
· 49 violations
County 09023
8 systems · 4,233 served
· 2,869 violations
County 09109
2 systems · 2,630 served
· 35 violations
County 09107
2 systems · 2,585 served
· 786 violations
County 09045
7 systems · 2,388 served
· 676 violations
County 09089
2 systems · 2,105 served
· 370 violations
County 09043
2 systems · 1,986 served
· 29 violations
County 09065
20 systems · 880 served
· 274 violations
County 09003
3 systems · 695 served
· 752 violations
County 09049
4 systems · 648 served
· 464 violations
County 09033
1 systems · 487 served
· 5 violations
County 09051
1 systems · 222 served
· 254 violations
Showing top 30 of 31 counties.
Drinking Water Guides
Frequently Asked Questions
How many water systems are in EPA Region 9 — Tribal Water Systems? ▼
EPA Region 9 — Tribal Water Systems has 323 public water systems serving approximately 555,721 people. These include community water systems, non-transient non-community systems, and transient non-community systems regulated under the Safe Drinking Water Act.
How many drinking water violations are in EPA Region 9 — Tribal Water Systems? ▼
EPA Region 9 — Tribal Water Systems has 48,296 total drinking water violations on record, with 3,354 classified as health-based violations. 96.6% of water systems in the state have at least one violation.
Has PFAS been found in EPA Region 9 — Tribal Water Systems drinking water? ▼
Of 41 water systems tested for PFAS in EPA Region 9 — Tribal Water Systems, 30 had PFAS detected, a 73.2% detection rate. PFAS are persistent "forever chemicals" that do not break down in the environment.
What is the violation rate for EPA Region 9 — Tribal Water Systems water systems? ▼
EPA Region 9 — Tribal Water Systems's violation rate is 96.6%. This measures the percentage of public water systems that have at least one recorded violation in the EPA SDWIS database, including both health-based and monitoring/reporting violations.
Where does this EPA Region 9 — Tribal Water Systems water data come from? ▼
All drinking water data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS is the federal database that tracks compliance for all public water systems regulated under the Safe Drinking Water Act.
Data Sources & Methodology
Drinking water violation data from the EPA Safe Drinking Water Information System (SDWIS). PFAS testing data from the UCMR5 monitoring program. SDWIS tracks all public water systems regulated under the Safe Drinking Water Act.
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial
Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on 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.