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Public water system record

Fort Defiance-Window Rock-St Michaels NTUA

On record as serving Fort Defiance, St. Michaels and Window Rock, Apache County, AZ · Serves 12,869 people

Federal records show 3 health-based violations and 9 monitoring/reporting issues for Fort Defiance-Window Rock-St Michaels NTUA in the last ten years, including an unresolved Revised Total Coliform Rule violation.

  • NN0403000
  • FT DEFIANCE
  • AZ
  • 12,869 served

System profile

Source water Groundwater
ZIP 86504
EPA system ID NN0403000

Verify this system on EPA ECHO →

Health-based violations, last 10 years
3
Resolved
2
Unresolved
1
Any acute record
No
Monitoring issues, last 10 years
9

Key facts

  • Fort Defiance-Window Rock-St Michaels NTUA draws water from 17 wells.
  • Highest measured level in the last 10 years: Total Trihalomethanes (TTHMs), 0.0843 mg/L, federal limit 0.08 mg/L (1.1 times the limit), 2017.
  • Record on file since 1992, with 20 health-based violations before October 19, 2016.

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Health-based violations

Since October 2016

Violation data reflects EPA records through March 2026. For the most current status, visit the EPA ECHO database.

Contaminant Rule family Start date Status Acute
Revised Total Coliform Rule
Treatment technique failure
 110 Feb 1, 2025 Active No
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0843 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
 220 Jan 1, 2017 Resolved No
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0829 mg/L, federal limit 0.08 mg/L (at or just above the limit)
 220 Oct 1, 2016 Resolved No

Monitoring and reporting issues

Since October 2016

Missed tests or reports, not contaminants found above a limit.

Issue Start date Status
Public Notice
OTHER
 Feb 1, 2025 Active
Total Trihalomethanes (TTHMs)
Monitoring and reporting
 Jul 1, 2018 Resolved
Haloacetic Acids (HAA5)
Monitoring and reporting
 Jul 1, 2018 Resolved
Total Trihalomethanes (TTHMs)
Monitoring and reporting
 Apr 1, 2018 Resolved
Haloacetic Acids (HAA5)
Monitoring and reporting
 Apr 1, 2018 Resolved
Nitrite
Monitoring and reporting
 Jan 1, 2018 Resolved
Nitrate
Monitoring and reporting
 Jan 1, 2018 Resolved
Public Notice
OTHER
 Jan 1, 2017 Resolved
Revised Total Coliform Rule
OTHER
 Apr 1, 2016 Resolved

Full record since 1992

EPA's records for Fort Defiance-Window Rock-St Michaels NTUA go back to 1992. Before October 19, 2016 they list 20 health-based violations (18 resolved, 2 archived by EPA without a recorded fix) and 126 monitoring or reporting violations.

Violations that began in Health-based Monitoring and reporting
1990s 0 1
2000s 5 87
2010 to October 18, 2016 15 38
October 19, 2016 to 2019 1 7
2020s 1 1

Most recent health-based violation before October 19, 2016: Total Trihalomethanes (TTHMs), began October 2016, Resolved.

Show all 20 health-based violations before October 19, 2016
Contaminant Start date Status
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0829 mg/L, federal limit 0.08 mg/L (at or just above the limit)
 Oct 1, 2016 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0932 mg/L, federal limit 0.08 mg/L (1.2 times the limit)
 Jul 1, 2016 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1148 mg/L, federal limit 0.08 mg/L (1.4 times the limit)
 Apr 1, 2016 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1148 mg/L, federal limit 0.08 mg/L (1.4 times the limit)
 Jan 1, 2016 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1076 mg/L, federal limit 0.08 mg/L (1.3 times the limit)
 Oct 1, 2015 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0844 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
 Jul 1, 2015 Resolved
Total Coliform
Contaminant limit exceeded
 Jul 1, 2014 Resolved
Combined Uranium
Contaminant limit exceeded
Measured 0.036 mg/L, federal limit 0.03 mg/L (1.2 times the limit)
 Jul 1, 2013 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1235 mg/L, federal limit 0.08 mg/L (1.5 times the limit)
 Jul 1, 2013 Resolved
Combined Uranium
Contaminant limit exceeded
Measured 0.036 mg/L, federal limit 0.03 mg/L (1.2 times the limit)
 Apr 1, 2013 Resolved
Combined Uranium
Contaminant limit exceeded
Measured 0.03492 mg/L, federal limit 0.03 mg/L (1.2 times the limit)
 Jan 1, 2013 Resolved
Combined Uranium
Contaminant limit exceeded
Measured 0.0371 mg/L, federal limit 0.03 mg/L (1.2 times the limit)
 Oct 1, 2012 Resolved
Total Coliform
Contaminant limit exceeded
 Aug 1, 2011 Resolved
Thallium, Total
Contaminant limit exceeded
 Oct 1, 2010 Resolved
Antimony, Total
Contaminant limit exceeded
Measured 0.025 mg/L, federal limit 0.006 mg/L (4.2 times the limit)
 Oct 1, 2010 Resolved
Total Coliform
Contaminant limit exceeded
 May 1, 2004 Resolved
Total Coliform
Contaminant limit exceeded
 Jan 1, 2003 Resolved
Total Coliform
Contaminant limit exceeded
 Jan 1, 2003 Archived
Total Coliform
Contaminant limit exceeded
 May 1, 2002 Resolved
Total Coliform
Contaminant limit exceeded
 May 1, 2002 Archived

What the violations mean

Total Trihalomethanes (TTHMs)

2 incidents

Disinfection byproduct levels exceeded the federal limit

Long-term TTHM exposure may increase bladder cancer risk

Revised Total Coliform Rule

1 incident

The system did not meet a requirement of the Revised Total Coliform Rule

Coliform and E. coli rules protect against bacteria in the distribution system

Where the water comes from

Fort Defiance-Window Rock-St Michaels NTUA draws water from 17 wells. 1 other community water system buys water from Fort Defiance-Window Rock-St Michaels NTUA.

Community systems that buy water from it

Annual water quality report

Fort Defiance-Window Rock-St Michaels NTUA must give its customers an annual water quality report (Consumer Confidence Report) by July 1, with the levels its tests found in the previous year.

Systems serving 10,000 or more people must mail or deliver the report to every customer, and from 2027 they must send it twice a year.

Find a posted report with EPA's Consumer Confidence Report search

Testing your own water

To test the water at your tap, or a private well this record does not cover, use a laboratory certified for drinking water by EPA Region 9.

Certified drinking water labs by state EPA guidance for private wells