PFAS in Tribal Systems, EPA Region 9 drinking water
EPA's final UCMR 5 data covers 41 public water systems in Tribal Systems, EPA Region 9, serving about 377,577 people. PFAS turned up in 8 of them (20%). 2 averaged above at least one EPA limit at a sampling point, affecting about 21,283 people.
Highest PFOA and PFOS averages among systems serving 1,000 or more: Rincon Northern (2.8 / 4.5 ppt) and Pala North (5.7 / 0.0 ppt).
Every tested system in Tribal Systems, EPA Region 9
Largest first. PFOA and PFOS columns show the average at each system's worst sampling point; EPA's limit for each is 4 ppt. Filter by name:
| Water system | People | PFOA | PFOS | PFAS found | Result |
|---|---|---|---|---|---|
| Pechanga · Temecula | 29,100 | - | - | 3 | Below limits |
| Casino Arizona Talking Stick (CATS) · Scottsdale | 25,785 | - | - | 0 | None found |
| GRIC DPW Wild Horse Pass · Sacaton | 22,795 | - | - | 0 | None found |
| Salt River Public Works · Scottsdale | 20,951 | - | - | 0 | None found |
| Thunder Valley Casino · Auburn | 18,007 | - | - | 0 | None found |
| Morongo · Banning | 16,000 | - | - | 0 | None found |
| WMATUA Miner Flat · Whiteriver | 15,570 | - | - | 0 | None found |
| Pala North · Pala | 14,280 | 5.7 | - | 4 | Above limit |
| Cache Creek Casino Resort · Brooks | 12,800 | - | - | 0 | None found |
| Sycuan · El Cajon | 12,350 | - | - | 0 | None found |
| Talking Stick Resort · Scottsdale | 12,087 | - | - | 0 | None found |
| Ak Chin Village · Maricopa | 11,646 | - | - | 1 | Below limits |
| Red Hawk Casino - Shingle Springs · Shingle Springs | 11,268 | - | - | 0 | None found |
| Table Mountain Rancheria · Friant | 10,675 | - | - | 0 | None found |
| Casino Arizona · Scottsdale | 10,603 | - | - | 0 | None found |
| Graton Resort and Casino · Rohnert Park | 10,127 | - | - | 0 | None found |
| Viejas Community System · Alpine | 9,600 | - | - | 1 | Below limits |
| Hard Rock Fire Mountain Water System · Oroville | 9,500 | - | - | 0 | None found |
| Santa Rosa Tachi Palace · Lemoore | 9,000 | - | - | 0 | None found |
| SCUA Upper Seven Mile · San Carlos | 8,478 | - | - | 1 | Below limits |
| Fort McDowell Community · Fountain Hills | 7,260 | - | - | 0 | None found |
| Rincon Northern · Valley Center | 7,003 | 2.8 | 4.5 | 5 | Above limit |
| Jackson Rancheria Casino & Hotel · Jackson | 6,120 | - | - | 0 | None found |
| Barona · Lakeside | 6,000 | - | - | 1 | Below limits |
| Pauma · Pauma Valley | 5,700 | - | - | 0 | None found |
| Quechan Utility · Yuma | 5,660 | - | - | 0 | None found |
| GRIC DPW Sacaton · Sacaton | 5,307 | - | - | 0 | None found |
| Cocopah Casino · Somerton | 5,300 | - | - | 0 | None found |
| Chukchansi Gold Resort · Coarsegold | 5,000 | 2.4 | - | 4 | Sample at limit |
| Rolling Hills Casino · Corning | 4,782 | - | - | 0 | None found |
| Sells Intertie · Sells | 4,000 | - | - | 0 | None found |
| Polacca · Polacca | 3,890 | - | - | 0 | None found |
| Lone Butte Industrial · Chandler | 3,810 | - | - | 0 | None found |
| Hoopa Valley-Wide System · Hoopa | 3,500 | - | - | 0 | None found |
| Colorado River Regional Water System · Parker | 3,476 | - | - | 0 | None found |
| Colusa Southern System · Colusa | 3,474 | - | - | 0 | None found |
| Dry Creek Rancheria · Geyserville | 2,200 | - | - | 0 | None found |
| Yavapai Apache - Cliff Castle · Camp Verde | 2,016 | - | - | 0 | None found |
| California Village · Needles | 1,290 | - | - | 0 | None found |
| Vaya Chin Intertie · Sells | 1,151 | - | - | 0 | None found |
| BIA Truxton Agency · Valentine | 16 | - | - | 0 | None found |
Cite this page
Well & Tap. "PFAS in Tribal Systems, EPA Region 9 drinking water: results for 41 systems." Data: U.S. EPA UCMR 5, final release August 2026. https://wellandtap.com/pfas/tribal-systems-epa-region-9/
Source: EPA UCMR 5 final occurrence data (August 2026); population from EPA SDWIS. Method.