Drinking water advisory lifted in South Slave region after THMs level off : My North Now

The drinking water advisory has been lifted for Hay River, Kátł’odeeche First Nation, Ka’a’gee Tu First Nation and Enterprise after trihalomethane levels drop within an acceptable range meeting Canadian guidelines.

Today, nearly three months after the initial advisory was issued, the NWT’s Health and Social Services announced that “normal use of drinking water may resume” without precautionary measures. 

Dr. Rohit advised the communities of Hay River, Enterprise, Kátł’odeeche First Nation and Ka’a’gee Tu First Nation (Kakisa) that the precautionary Public Health Advisory for drinking water has been lifted.

“The Community Government of Hay River reported monthly results of THMs, and the
current annual running average has come below 100 µg/L. The drinking water now meets
the Guidelines for Canadian Drinking Water Quality. Normal use of drinking water may
resume.The Environmental Health Unit will continue to monitor results from the Town of Hay River Water Treatment Plant,” read a message issued by the department.

North Now reached out for more information and will share those details when they become available. 

Back in November, Dr. Rohit reported that lakewater quality, which has changed significantly since the Hay River treatment plant was built, is the cause of high levels of trihalomethanes behind the boil water advisories issued Monday for Hay River, Enterprise, Kátł’odeeche First Nation and Ka’a’gee Tu First Nation.

The chief officer explained that the heightened trihalomethanes (THM)levels were first detected in September, but because of the way Health Canada assesses water samples for THMs, those results had to be assessed, remeasured and confirmed before being made public.

Dr. Chirag said that the testing was being done monthly in place of the standard quarterly sampling to help officials and engineers understand how the modifications at the treatment plant impact the THM levels.

The chief officer explained that heightened levels of THMs are caused by the reaction of chlorine with naturally occurring organic material which has accumulated substantially in the lakewater in the decades since the water treatment plant was built.

“What we know for certain is that the source water, the water that we are taking in from the lake, over the years, has seen higher amounts of organic material. And that organic material is interacting with the chlorine used for disinfecting. And that’s where we end up having THMs”

Investigations have found that climate change and low water levels are part of the picture, but “multiple” factors are involved, said Rohit.

The THMs are produced when the chemical chlorine is added to the lakewater.
“To have a higher level of chemicals called trihalomethanes which are byproducts of when the drinking water is disinfected with chlorine, THMs are a group of chemicals, they are produced where the chlorine interacts with organic materials in the water,” explained the chief environmental officer.

“The way THMs are monitored in Canada and because this is a standard set by Healthcare Canada. Is that it’s one sample taken every three months. And then over one year, four samples are collected and those values are averaged out,” added Dr. Rohit.
Over the years, the values of THM’s have been “fluctuating” in the South Slave’s lakewater but “slowly creeping up,” said the chief environmental officer.

Dr. Chirag and community officials said they have been closely monitoring the THM values as well as exploring methods and optimizations to reduce the THMs levels.

“Part of the other thing that we do is notify public when the measures are higher. And so, the action can be taken at the individual level to protect themselves and their loved ones,” added Dr. Rohit.

The chief environmental officer said that according to assessments done so far, there’s no damage or technical issues with the Hay River water plant. But because its infrastructure is outdated, the system is not able to filter the amount of organic materials that come in and when chlorine is added, THMs are produced.