Fluoride Action Network

Missing label on fluoride drum cause of Gravenhurst water emergency, says district

Source: Gravenhurst Banner | January 21st, 2022 | By Sarah Law
Location: Canada, Ontario

Second review underway into water outage and boil-water advisory in November 2021

More details have been shared about the emergency that left Gravenhurst without a stable water supply for three and a half days.

Chaos erupted at the Gravenhurst Water Treatment Plant the morning of Nov. 27, 2021. The town was under a do-not-use advisory until 5 p.m. that day when a boil-water advisory was then issued until midday Nov. 30.

During the engineering and Public Works Committee meeting on Jan. 19, commissioner of engineering and public works Fred Jahn and area water and sewer manager Mark Pringle presented an operational review of the water emergency.


According to the report, “the primary root cause of the event was the failure of a plumbing component called a check valve, which is designed to prevent water from back-flowing into the chemical metering systems.”

“This resulted in dilution of the fluoride contents and piping system with water, which explains why the required fluoride levels were not detected by the supervisory control and data acquisition system, subsequently triggering the low fluoride level alarms.”

While the district initially said the issue was an “improperly labelled fluoride container,” the report says the label was missing entirely.

“The significant contributing factor leading to the decision to shut down the drinking water system was the missing fluoride drum label. This missing label raised questions as to the actual contents in the drum.”


The staff overtime, water tanker truck, and bottled water provided to the public during the emergency cost the district $64,000.

Costs that cannot be measured easily are the stresses and inconveniences to the public and the money lost by businesses, particularly restaurants, that had to close during the water outage and subsequent boil-water advisory.


The district met with officials from the Simcoe Muskoka District Health Unit and Ministry of the Environment, Conservation and Parks on Dec. 8, 2021.

The report says that the ministry made five directives for “reducing risk and minimizing disruption time of potential events.”

These include:

— updating the standard operating procedure WS-35 — ordering and receiving treatment chemicals;

— developing a standard operating procedure for suspected or evident chemical contamination that is potentially identified within the source water, the treated water and/or the distribution systems;

— developing a standard operating procedure for systemic low pressure, loss of pressure, or full depressurization of the water distribution system;

— developing a hauled water standard operating procedure outlining when water can be transported from other Muskoka water treatment plants to maintain water supply to a plant that is experiencing technical or process issues;

— continuing to implement a backflow prevention program and prioritize obtaining cross-connection surveys in conjunction with area municipal chief building officials on program implementation.


A second review of the incident is underway that focuses on the emergency response, lessons learned, and recommendations for improvement.