Non-Transient Non-Community Water System · PWS 090400060
BIA San Carlos
Operator location San Carlos, EPA Region 9 — Tribal Water Systems - upper-third violation load (> 74 violations) with 309 EPA violations; groundwater source; 2,150 served (PWS-level, not municipal population).
- 2,150
- People served (this PWS)
- 309
- EPA violations (this PWS)
- 28
- Health-based (this PWS)
- Untested
- UCMR5 (this PWS)
BIA San Carlos standing, high SDWIS violation third
309 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 9% is middle-third health share (≤ 23%). Population rank #13,014 of 29,740 among systems serving 500+.
The verdict
BIA San Carlos sits in the upper third of the sitemap cohort by violation count (309), so the tables below sample a dense compliance trail rather than a near-clean ledger. Population served is mid-pack at 2,150 (mid served population (≤ 3,309)). Health-based share is 9% (middle-third health share (≤ 23%)). No UCMR5 PFAS test appears for this system in this extract.
- #13,014 of 29,740
- Population · /systems
- #61 of 129
- Population · 09
- 309
- Total EPA violations on record
- 9%
- Health-based (MCL / treatment failure)
Population ordinals match the sitemap cohort (systems serving 500+, population_served DESC). See methodology · corpus placement.
System Details
- System Type
- Non-Transient Non-Community
- Owner Type
- Federal
- Connections
- 75
- School/Daycare
- No
- MCL Violations
- 27
- Monitoring Violations
- 201
- Treatment Tech Violations
- 1
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Coliform (TCR) | MR | 29 | 2013 |
| Coliform (TCR) | MCL | 15 | 2015 |
| Arsenic | MCL | 12 | 2012 |
| Arsenic | MR | 10 | 2012 |
| Revised Total Coliform Rule | RPT | 9 | 2025 |
| Nitrate | MR | 6 | 2017 |
| TTHM | MR | 6 | 2021 |
| Consumer Confidence Rule | Other | 6 | 2009 |
| 1,2-DIBROMO-3-CHLOROPROPANE | MR | 5 | 2014 |
| ETHYLENE DIBROMIDE | MR | 5 | 2014 |
| Total Haloacetic Acids (HAA5) | MR | 5 | 2021 |
| Atrazine | MR | 4 | 2014 |
| Total Polychlorinated Biphenyls (PCB) | MR | 4 | 2004 |
| Chlordane | MR | 4 | 2004 |
| Chlorine | MR | 4 | 2023 |
| Barium | MR | 3 | 2004 |
| Cadmium | MR | 3 | 2004 |
| Chromium | MR | 3 | 2004 |
| Mercury | MR | 3 | 2004 |
| Fluoride | MR | 3 | 2004 |
| Selenium | MR | 3 | 2004 |
| BHC-GAMMA | MR | 3 | 2004 |
| Toxaphene | MR | 3 | 2004 |
| Methoxychlor | MR | 3 | 2004 |
| Carbofuran | MR | 3 | 2004 |
| LASSO | MR | 3 | 2004 |
| 2,3,7,8-TCDD | MR | 3 | 2014 |
| Heptachlor | MR | 3 | 2004 |
| Heptachlor epoxide | MR | 3 | 2004 |
| 2,4-D | MR | 3 | 2004 |
Violation Count vs. the National Corpus
BIA San Carlos has 309 recorded EPA violations, 91% of the 29,740 public water systems serving 500+ people nationwide carry fewer, and 9% carry more. 9% of this system's own violations are health-based (28 of 309), and it ranks #13,014 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)
309 Higher than most more violations than 91% 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
SDWIS compliance record for BIA San Carlos
309 violations on record for 090400060; use EPA SDWIS to confirm return-to-compliance dates and monitoring categories.
Sources: EPA SDWIS
Nationwide peers
309 violations · 2,150 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.
Cross-state systems near this population served
Nearest cross-state systems by EPA SDWIS population_served (same 500+ sitemap gate).
What to do with BIA San Carlos
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.