Circumstances

There are 22 activities (such as storing home heating oil or sewage storage through a septic system) that can be threats to municipal sources of drinking water.

What is a circumstance that makes a threat significant?

Quantity and location are examples of circumstances that can make an activity a significant threat to drinking water sources.

For example, if you are located within 100 metres of a municipal well, and you have home heating oil stored at your house, circumstances that would make it a significant threat are that the fuel is stored below grade (in your basement, for example) and the volume is greater than 250 litres.

Provincial Tables of Threats and Circumstances

You can find out what circumstances make that threat significant online here:

• https://www.ontario.ca/environment-and-energy/provincial-tables-circumstances

The Ontario Ministry of the Environment, Conservation and Parks (MECP) has made these tables to show when an activity or condition can be a significant, moderate or low threat to drinking water.

The tables show levels of risk posed by hundreds of combinations of threats, vulnerability scores, and circumstances (such as quantities) under Ontario Regulation 287/07.

Hazard Ratings

When the tables of circumstances were prepared, hazard ratings were considered. Hazard ratings were calculated from a database from such components as:

• The toxicity, environmental fate, quantity, and method of release for chemical parameters, and;
• The frequency of presence of pathogens, and the method of release for pathogens.

 

A land-use activity could be a significant threat to drinking water if:

It is located near a municipal well – for instance,

1) Within 100 metres of that well, or;
2) Within the two-year time-of-travel area leading to that municipal well.

• The activity has not been prohibited
• The activity is not properly managed
• The activity is taking place in certain circumstances.

 

One way to find out if your activity is a significant threat to drinking water is to contact staff in your region or your municipal risk management official.

You can also check our online maps to find out if you are in a wellhead protection area zones A, B, or C.

You may also go to the Province of Ontario’s Source Protection Information Atlas.

Visit our threats page for a list of the 22 activities and conditions which could pose risk to municipal drinking water sources.