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Community Water System · PWS NN3500239

Whitehorse Lake NTUA

Ft Defiance, Navajo Nation 86504 - drinking water served from surface water sources to 277 people, tracked in EPA SDWIS and UCMR5.

277
People served
60
EPA violations
4
Health-based
Untested
UCMR5 result

The verdict

EPA records 60 drinking-water violations at Whitehorse Lake NTUA, 7% of them health-based - below the Navajo Nation per-system average.

60
Total EPA violations on record
7%
Health-based (MCL / treatment failure)
277
People served by this system
N/A
PFAS compounds detected (UCMR5)

Water Quality Snapshot: Whitehorse Lake NTUA

Whitehorse Lake NTUA is a native american-owned community water system that delivers drinking water to 277 residents in Ft Defiance, Navajo Nation through 81 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 60 total violations for this system , of which 4 (7%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 45 monitoring and reporting violations are on file. The most recent violation on record dates to 2016.

The most frequently cited contaminant at this system is Nitrite, recorded in 4 violations (MR). This system has not yet been sampled under EPA's UCMR5 PFAS monitoring program, so no PFAS detection data is available here.

Across Navajo Nation, EPA tracks 170 public water systems serving 167,275 people, with 29,535 cumulative violations and 1,366 health-based violations on record. About 100% of systems in the state carry at least one violation, and state-wide the average per system is 173.7 violations. Statewide, 13 of 13 UCMR5-tested systems have reported PFAS detections (100%).

Whitehorse Lake NTUA's 60 violations sit below the Navajo Nation average.

All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.

Population Served
277
Total Violations
60
Health-Based Violations
4
Water Source
Surface Water

System Details

System Type
Community
Owner Type
Native American
Connections
81
School/Daycare
No
MCL Violations
4
Monitoring Violations
45
Treatment Tech Violations
0

Violation History

Contaminant violations recorded by EPA.

Contaminant Category Count Latest
Nitrite MR 4 2013
Antimony, Total MCL 4 2010
Mercury MR 3 2008
Thallium, Total MR 3 2008
Endothall MR 3 2014
Glyphosate MR 3 2014
Total Polychlorinated Biphenyls (PCB) MR 3 2008
1,2-DIBROMO-3-CHLOROPROPANE MR 3 2008
Nitrate MR 3 2013
Coliform (TCR) MR 3 2012
2,3,7,8-TCDD MR 3 2014
Fluoride MR 3 2008
ETHYLENE DIBROMIDE MR 3 2008
Diquat MR 3 2014
Stage 2 Disinfectants and Disinfection Byproducts Rule MR 2 2013
Combined Uranium MR 1 2005
Combined Radium (-226 and -228) MR 1 2005
Revised Total Coliform Rule Other 1 2016
Gross Alpha, Excl. Radon and U MR 1 2005

Verify This Water System

The figures above are aggregated from EPA's public databases. To verify the underlying records, or to file a complaint, request a Consumer Confidence Report, or check current monitoring status, go directly to the federal and state regulators that enforce the Safe Drinking Water Act for Whitehorse Lake NTUA.

Federal Source of Truth

EPA SDWIS, Federal Reports

EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:

View PWS ID NN3500239 on SDWIS

Source: EPA SDWIS Federal Reports Search

State Regulator

Navajo Nation Drinking Water Authority

Navajo Nation's primacy agency administers the Safe Drinking Water Act locally. Search EPA SDWIS for the current state contact, or use the state's public health or environment department portal.

Find NN regulator via EPA SDWIS

Violation Timeline

Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.

Year (latest) Contaminant Category Count EPA Record
2016 Revised Total Coliform Rule Other 1 SDWIS / NN3500239 / 8000
2014 Endothall MR 3 SDWIS / NN3500239 / 2033
2014 Glyphosate MR 3 SDWIS / NN3500239 / 2034
2014 2,3,7,8-TCDD MR 3 SDWIS / NN3500239 / 2063
2014 Diquat MR 3 SDWIS / NN3500239 / 2032
2013 Nitrite MR 4 SDWIS / NN3500239 / 1041
2013 Nitrate MR 3 SDWIS / NN3500239 / 1040
2013 Stage 2 Disinfectants and Disinfection Byproducts Rule MR 2 SDWIS / NN3500239 / 0600
2012 Coliform (TCR) MR 3 SDWIS / NN3500239 / 3100
2010 Antimony, Total MCL 4 SDWIS / NN3500239 / 1074
2008 Mercury MR 3 SDWIS / NN3500239 / 1035
2008 Thallium, Total MR 3 SDWIS / NN3500239 / 1085
2008 Total Polychlorinated Biphenyls (PCB) MR 3 SDWIS / NN3500239 / 2383
2008 1,2-DIBROMO-3-CHLOROPROPANE MR 3 SDWIS / NN3500239 / 2931
2008 Fluoride MR 3 SDWIS / NN3500239 / 1025

How Whitehorse Lake NTUA Compares

Cross-reference this system's record against state averages and the federal MCL framework for context.

Metric Whitehorse Lake NTUA Navajo Nation avg Federal benchmark
Total violations 60 173.7 SDWA compliance, any non-zero count is a recorded breach
Health-based violations 4 8 Indicates a contaminant exceeded a federal MCL
PFAS detection None 100% EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt
Population served 277 984 Sizing context for compliance burden

Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across 170 regulated public water systems in Navajo Nation.

Federal MCL reference, Safe Drinking Water Act thresholds ▼
Contaminant Federal MCL / Action Level Note
Lead 0 mg/L (Action Level: 0.015 mg/L) Lead and Copper Rule treatment technique
Arsenic 0.010 mg/L (10 ppb) Health-based MCL since 2006
Total Coliform Treatment technique (RTCR) Indicator organism, monitoring trigger
PFOA / PFOS (PFAS) 4.0 ppt each (final 2024 rule) Compliance deadline 2029 (EPA proposed extending to 2031, not yet final as of May 2026)
Nitrate (as N) 10 mg/L Acute health risk for infants

Frequently Asked Questions

Is Whitehorse Lake NTUA water safe to drink? ▼
Whitehorse Lake NTUA (PWS ID: NN3500239) has 60 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 277 people using Surface Water sources.
How many people does Whitehorse Lake NTUA serve? ▼
Whitehorse Lake NTUA serves 277 people in Ft Defiance, Navajo Nation. It is a Native American-owned system using Surface Water water sources with 81 service connections.
What type of violations does Whitehorse Lake NTUA have? ▼
Whitehorse Lake NTUA has 60 total violations: 4 health-based violations (MCL exceedances or treatment failures), 45 monitoring/reporting violations, and 0 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.
Has PFAS been detected in Whitehorse Lake NTUA water? ▼
No PFAS testing data is available for Whitehorse Lake NTUA under the EPA's UCMR5 monitoring program.
What water source does Whitehorse Lake NTUA use? ▼
Whitehorse Lake NTUA uses Surface Water as its primary water source. It is classified as a Community Water System (CWS), serving residential populations year-round.
Where does this data come from? ▼
All data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS tracks compliance for all public water systems regulated under the Safe Drinking Water Act.
Data Sources: EPA Safe Drinking Water Information System (SDWIS), Q4 2025. This data is provided for informational purposes only.

Read our methodology - how this data is sourced, computed, and verified.

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 system's figures are rendered directly from 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.