THM Water Advisory

CURRENT WATER ADVISORY: Elevated THM Levels

  • Locational Running Annual Average When Public Health Advisory was Issued (November 3rd, 2025): 109 ug/L
  • Current Locational Running Annual Average (November 24th, 2025): 105.75 ug/L
  • Health Canada’s Guideline for 12 Month Running Average Maximum Acceptable Concentration: 100 ug/L

About the THM Water Advisory

The Town of Hay River has detected elevated Total Trihalomethane (THM) levels through routine monitoring. In coordination with GNWT Public Health, a precautionary advisory has been issued. This page contains updates and guidance for all residents. Short-term use (e.g., showering, bathing, cleaning) poses minimal risk, but long-term consumption of water (over 70 years) with elevated THM levels may pose health risks.

What Residents Should Do

  • Do not drink tap water until further notice.
  • Use bottled or filtered water for drinking, cooking, and preparing infant formula.
  • Tap water is safe for bathing, showering, laundry, brushing teeth and cleaning.
  • Provide bottled or alternative water for pets
  • More specifics on precautions can be found within Public Health Advisory – CPHO

What Are THMs?

Total Trihalomethanes (THMs) are chemical by‑products formed when chlorine used for disinfection reacts with organic matter. Organic matter most commonly originates from natural sources such as decomposing plant material in rivers and lakes. Long-term exposure (over 70+years) to elevated levels may pose health risks.

Town Actions Underway

  • Adjusting water treatment and disinfectant processes.
  • Flushing areas of the water distribution system.
  • Conducting increased sampling and laboratory analysis.
  • Collaborating closely with GNWT Public Health, MACA, and other water experts.

Latest Updates

Updates will be added as new information becomes available, including water sample results and expected timelines for lifting the advisory. The advisory will remain in place until consecutive testing confirms that THM levels meet safety standards. This process may take multiple months. Updates will be provided monthly or upon any significant change.

Last updated: November 25th

The Town of Hay River has been working closely with both the Department of Health and the Department of Municipal and Community Affairs. There have been improvements made to treatment systems, and more optimization processes will be implemented shortly.     Recent water sample results have shown improvement in the THM levels, unfortunately, even though this is a good progress, the new annual average is still higher than the Health Canada guidelines values. As such, the Public Health Advisory will remain in effect. The Town will continue to make adjustments to the treatment system and collect new samples for public health review.  Current annual sample results are:

28-Jan-25         Underground Reservoir                           83 ug/L

29-Apr-25         Underground Reservoir                           118 ug/L

19-Aug-25        Underground Reservoir                           124 ug/L

18-Nov-25        Underground Reservoir                           98 ug/L

November 17th – Regular Meeting of Council

The Council of the Town of Hay River accepted a report on the drinking water THM public health advisory. The report provides background on the advisory and information on testing and treatment actions being pursued by the Town and supported by the Chief Public Health Officer. The report can be found on page 58 of the package.

November 5th – Public Meeting

A meeting was held with public officials that included representation from the Town of Hay River, Office of the Chief Public Health Officer, and MACA to present information on the advisory and respond to questions from the public.

November 3rd – Public Health Advisory

The Office of the Chief Public Health Officer issued a Public Health Advisory for Hay River, Enterprise, Katl’odeeche First Nation, and Ka’a’gee Tu First Nation (Kakisa) on November 3, 2025 due to elevated Trihalomethanes (THM) levels identified through routine testing.

Resources for Residents

Contact Information

Town of Hay River
Phone: (867) 874-6522
Email: townhall@hayriver.com

NWT Health and Social Services Authority
For health‑related guidance and information contact Environmental_Health@gov.nt.ca