Community Water System · PWS NN3500237
Tohatchi-Mexican Springs-Twin Lakes NTUA
Operator location Ft Defiance, Navajo Nation - upper-third violation load (> 74 violations) with 76 EPA violations; groundwater source; 1,669 served (PWS-level, not municipal population).
- 1,669
- People served (this PWS) Middle third of systems
- 76
- EPA violations (this PWS) Upper third of systems
- 3
- Health-based (this PWS) Middle third by health-based share
- Untested
- UCMR5 (this PWS) No UCMR5 result
Tohatchi-Mexican Springs-Twin Lakes NTUA standing, high SDWIS violation third
76 EPA SDWIS violations on record - upper-third violation load (> 74 violations). Corpus terciles use 29,740 systems serving 500+ (the sitemap cohort). Health-based share 4% is middle-third health share (≤ 23%). Population rank #15,035 of 29,740 among systems serving 500+.
The verdict
Tohatchi-Mexican Springs-Twin Lakes NTUA sits in the upper third of the sitemap cohort by violation count (76), so the tables below sample a dense compliance trail rather than a near-clean ledger. Population served is mid-pack at 1,669 (mid served population (≤ 3,309)). Health-based share is 4% (middle-third health share (≤ 23%)). No UCMR5 PFAS test appears for this system in this extract.
- #15,035 of 29,740
- Population · /systems
- #18 of 82
- Population · NN
- 76
- Total EPA violations on record
- 4%
- Health-based (MCL / treatment failure)
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
- 488
- School/Daycare
- No
- MCL Violations
- 3
- Monitoring Violations
- 64
- Treatment Tech Violations
- 0
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Total Haloacetic Acids (HAA5) | MR | 14 | 2020 |
| TTHM | MR | 14 | 2020 |
| Coliform (TCR) | MR | 5 | 2012 |
| Nitrite | MR | 4 | 2011 |
| Nitrate | MR | 3 | 2011 |
| Coliform (TCR) | MCL | 3 | 2014 |
| Stage 2 Disinfectants and Disinfection Byproducts Rule | MR | 3 | 2013 |
| Revised Total Coliform Rule | Other | 2 | 2016 |
| DICHLOROMETHANE | MR | 1 | 2005 |
| 1,1-Dichloroethylene | MR | 1 | 2005 |
| 1,2-Dichloroethane | MR | 1 | 2005 |
| 1,1,1-Trichloroethane | MR | 1 | 2005 |
| Carbon tetrachloride | MR | 1 | 2005 |
| 1,2-Dichloropropane | MR | 1 | 2005 |
| Trichloroethylene | MR | 1 | 2005 |
| Benzene | MR | 1 | 2005 |
| Ethylbenzene | MR | 1 | 2005 |
| Styrene | MR | 1 | 2005 |
| CHLOROBENZENE | MR | 1 | 2005 |
| Xylenes, Total | MR | 1 | 2005 |
| Vinyl chloride | MR | 1 | 2005 |
| 1,1,2-Trichloroethane | MR | 1 | 2005 |
| trans-1,2-Dichloroethylene | MR | 1 | 2005 |
| 1,2,4-Trichlorobenzene | MR | 1 | 2005 |
| Tetrachloroethylene | MR | 1 | 2005 |
| p-Dichlorobenzene | MR | 1 | 2005 |
| o-Dichlorobenzene | MR | 1 | 2005 |
| Toluene | MR | 1 | 2005 |
| cis-1,2-Dichloroethylene | MR | 1 | 2005 |
Violation Count vs. the National Corpus
Tohatchi-Mexican Springs-Twin Lakes NTUA has 76 recorded EPA violations, 67% of the 29,740 public water systems serving 500+ people nationwide carry fewer, and 33% carry more. 4% of this system's own violations are health-based (3 of 76), and it ranks #15,035 of 29,740 by population served among that same cohort.
EPA violations vs. the national water-system corpus
Public water systems serving 500+ people (EPA SDWIS)
76 Around the middle fewer violations than 33% 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
Tohatchi-Mexican Springs-Twin Lakes NTUA 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
SDWIS compliance record for Tohatchi-Mexican Springs-Twin Lakes NTUA
76 violations on record for NN3500237; use EPA SDWIS to confirm return-to-compliance dates and monitoring categories.
Sources: EPA SDWIS
Nationwide peers
76 violations · 1,669 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.
Cross-state systems near this population served
Nearest cross-state systems by EPA SDWIS population_served (same 500+ sitemap gate).
What to do with Tohatchi-Mexican Springs-Twin Lakes NTUA
Use this system's EPA-reported record as a starting filter, not a final verdict.
- See how every tracked system in Navajo Nation compares on the same EPA violation measures. Navajo Nation 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.