State profile · EPA SDWIS + UCMR5
EPA Region 1 — Tribal Water Systems Drinking Water Quality
5 SDWIS-listed systems serve 58,570 people. UCMR5 PFAS detection is 50% on the tested subset (upper-third UCMR5 detection (> 35.3%)); SDWIS violation rate is 100%.
- 5
- SDWIS water systems
- 814
- Total violations
- 100%
- SDWIS systems w/ a violation
- 50%
- UCMR5 PFAS rate (2 tested)
The verdict
UCMR5 PFAS detection is 50% (1 of 2 tested) - upper-third UCMR5 detection (> 35.3%). According to EPA SDWIS population served, EPA Region 1 — Tribal Water Systems ranks #63 of 66 states and territories by people served through public water systems.
- #63 of 66
- Population · states corpus
- 814
- Total EPA violations on record
- 16%
- Health-based (MCL / treatment)
- 100.0%
- SDWIS systems with ≥1 violation
SDWIS violation % and UCMR5 PFAS % use different denominators (full inventory vs tested subset). Population ordinal uses SDWIS population served.
EPA Region 1 — Tribal Water Systems standing, high SDWIS violation-rate third
EPA Region 1 — Tribal Water Systems sits in the upper third of jurisdictions by SDWIS violation rate (100%), so the system lists below sample one of the denser state-level compliance trails in this extract. Population served is smaller (58,570; smaller served population (≤ 1,083,630)), so a high rate can still mean a compact household footprint. Health-based share is 16% - a material slice is exposure-relevant, with the rest monitoring or reporting. UCMR5 PFAS detection is 50% on the tested subset (upper-third UCMR5 detection (> 35.3%)) - a different denominator from the SDWIS violation rate. Systems listed below are ranked by population served or violation count; pair rate with inventory size before reading exposure scale.
Nationwide similar states
Nearest by SDWIS violation rate
Health-based share of this violation record
EPA SDWIS classifications for EPA Region 1 — Tribal Water Systems's 814 recorded violations.
EPA Region 1 — Tribal Water Systems vs nearest violation-rate peers
Share of SDWIS-listed systems with at least one recorded violation; peers are nearest by absolute rate distance, not a fixed top-seven list.
- 01
EPA Region 1 — Tribal Water Systems
100 % of systems
- DC
District of Columbia
100 % of systems
- 02
EPA Region 2 — Tribal Water Systems
100 % of systems
- GU
Guam
100 % of systems
- NN
Navajo Nation
100 % of systems
What this shows EPA Region 1 — Tribal Water Systems's rate is 100% (5 of 5 systems; upper-third rate (> 96.1%)). This is a comparison of recorded SDWIS violations, not a measure of current water safety.
EPA Region 1 — Tribal Water Systems vs all jurisdictions by SDWIS system inventory
Where this state's public water system count sits among every state and territory on PlainWater
5 65th of 66 the lowest of 66 jurisdictions
States and territories, banded by SDWIS-listed public water system count
Each bar is a band; taller bars hold more jurisdictions. 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 state aggregates · 2026-05-15
Largest Water Systems
Context: PFAS in drinking water · methodology · all states
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.