Drinking Water Threats
From fertilizing lawns and gardens to safely storing and handling fuels and solvents, your actions and the actions of all residents and business owners may affect the quality of drinking water in the Halton-Hamilton Source Protection Region. Similarly, from watering your lawn to taking long showers, your activities may affect the quantity of water available for use.
The Clean Water Act, 2006 requires that the identification of activities considered threats to drinking water sources be undertaken in vulnerable areas within the source protection areas. Accordingly, an assessment of all the activities occurring in all vulnerable areas, was completed.
Water Quality Threats
The Province of Ontario has prescribed in regulation nineteen activities that under certain circumstances could impair the quality of drinking water sources. The activities deemed to be drinking water quality threats are related to the following:
- Waste disposal sites – their establishment, operation, or maintenance
- Sewage systems – their establishment, operation, or maintenance
- Agricultural source material – application to land
- Agricultural source material – storage
- Agricultural source material – management
- Non-agricultural source material – application
- Non-agricultural source material – handling and storage
- Commercial fertilizer – application
- Commercial fertilizer – handling and storage
- Pesticide – application
- Pesticide – handling and storage
- Road salt – application
- Road salt – handling and storage
- Snow – storage
- Fuel – handling and storage
- Dense non-aqueous phase liquid – handling and storage
- Organic solvent – handling and storage
- Chemicals used to de-ice aircraft – management of runof
- Land associated with livestock – use of for grazing, pasturing, confinement, or as a yard
- Establishment and operation of a liquid hydrocarbon pipeline
The conveyance of oil by way of a pipeline that crosses an open body of water was also identified as a local threat within the Halton Region and Hamilton Region Source Protection Areas. However, in 2017, the Province added pipelines carrying liquid hydrocarbons as a prescribed threat (22). Therefore, the local threat will be replaced by the prescribed threat during the next source protection plan update.
Water Quantity Threats
The Province of Ontario also identified two activities considered to be threats to the quantity of a water source. These include:
- An activity that takes water from an aquifer or a surface water body without returning the water taken to the same aquifer or surface water body
- An activity that reduces the recharge of an aquifer
These threats are considered when a municipal well has undergone a Tier 3 local water quantity risk assessment.
Provincial reference tables
The circumstances that would make the water quality activities listed above threats to a drinking water source typically refer to the quantity of chemical/material or land, the chemical released, and the affected source water.
The Ministry of the Environment produced reference tables for each combination of vulnerable area and vulnerability score for three threat categories and three risk levels. The threat categories are:
- dense non-aqueous phase liquid (DNAPL)
The risk levels are:
The 76 reference tables, called the Provincial Tables of Circumstances, were replaced by an online tool accessible at https://swpip.ca/Threats.
Locations of threats
The risk to drinking water associated with each of the water quality circumstances is assessed in relation to the vulnerability scores assigned within each of the vulnerable areas. Significant drinking water quality threats are only possible within the wellhead protection areas, specifically in the highly vulnerable areas with vulnerability scores of 10 and 8. Only low and moderate threats are possible in intake protection zones 1 and 2, significant groundwater recharge areas, and highly vulnerable aquifers.
Modelling was completed for activities along the Lake Ontario and Hamilton Harbour shoreline to identify events, such as a spill, that would result in significant impairment of the quality of the lake water at the four Halton Region municipal water intakes and the one Hamilton intake. Some locations of significant threat activities were also identified through this process.
Significant threats require action, which comes in the form of policies in the source protection plan.
The locations where drinking water quality threat activities would be significant have been mapped for each wellhead protection area. The maps can be reviewed and downloaded by clicking on the well field name.
Kelso, Campbellville, Walkers Line, Freelton, Carlisle groundwater, Carlisle surface water, Greensville, Lake Ontario-Hamilton Region, Lake Ontario-Halton Region
We are all responsible for protecting and preserving water sources for present and future generations. Learn more about how you can help keep our drinking water sources clean and reliable.