Today, the Supreme Court of Canada clarified the reporting requirement contained in section 15(1) of the Ontario Environmental Protection Act (EPA), which requires that the Ministry of the Environment (MOE) be notified forthwith when a contaminant that causes or is likely to cause an adverse effect is discharged into the environment outside of the normal course of events. Justice Abella, writing for the majority in Castonguay Blasting Ltd. v. Ontario (Environment), summed up the obligation to report as follows: "when in doubt, report".


In November 2007, Castonguay was blasting rock for a road construction project when the explosion did not proceed as planned and sent fly-rock approximately 90 metres in the air, causing substantial property damage to a nearby house and a car. Castonguay remedied the property damage, and the incident was reported to the Ministry of Transportation and to the Ministry of Labour, but not to the MOE, which did not find out about the fly-rock until 2008, when informed by the Ministry of Transportation. In 2009, the MOE charged Castonguay with failure to report the incident forthwith, as required under section 15 of the EPA. Castonguay argued that the fly-rock did not cause an adverse effect to the natural environment, and was acquitted by the Ontario Court of Justice. On appeal, the Ontario Superior Court of Justice reversed the acquittal. The Ontario Court of Appeal, in a split decision, upheld the decision of the Superior Court, leading to an appeal by Castonguay.

The Supreme Court (SCC) dismissed the appeal, and confirmed that Castonguay was obliged to report the incident forthwith when it happened. In interpreting section 15 of the EPA, the SCC began by referring to the purpose of the statute as a whole. As the EPA is a remedial legislation, the SCC wrote that it is entitled to a generous interpretation, because the objective of environmental protection reaches "wide and deep". The SCC also noted that the purpose of the reporting requirement contained in section 15 of the EPA is to ensure that the MOE – and not the notifier – conducts the investigation and decides what remedial steps are required, if any.

The expression "adverse effect" in the EPA is defined, among other things, as meaning one or more of: impairment to the quality of the natural environment for any use that can be made of it; injury or damage to property; rendering any property ... unfit for human use; and loss of enjoyment of normal use of property. The SCC rejected Castonguay's argument that, in order to amount to an adverse effect, the natural environment had to be impaired. However, the SCC accepted Castonguay's argument, based on the decision of the Ontario Court of Appeal in R. v.Dow Chemical, that the adverse effect must be more than trivial in order to constitute a reportable event (although the statute does not say so). Based on this interpretation, the SCC found that the discharge of the fly-rock was not in the normal course of events and, given the substantial property damage that resulted from the event, caused a not trivial adverse effect that had to be reported forthwith.


The SCC, in Castonguay, did not change the law; it simply applied the existing statute. However, the decision highlights the arguable overbreadth of the Ontario EPA's obligation to report. Indeed, taking Castonguay as an example, and considering the transient nature of the fly-rock discharge, the inertia and non-toxicity of the fly-rock, and the fact that the property damage had been remedied as required, the ramifications of the obligations to report under Ontario's EPA become apparent, and would seem to include events many people would have thought relatively innocuous.

Therefore, when determining whether a discharge should be reported to the MOE, the following test should be applied:

1. Is a contaminant (meaning any solid, liquid, gas, odour, heat, sound, vibration that causes or may cause an adverse effect) discharged?

2. Is the contaminant discharged into the natural environment (meaning air, land, or water) in Ontario?

3. Is the discharge out of the normal course of events (meaning unusual, or untypical)?

4. Does the discharge cause, or is likely to cause, an adverse effect, meaning one or more of:

1. Impairment of the quality of the natural environment for any use that can be made of it

2. Injury or damage to property or to plant or animal life

3. Harm or material discomfort to any person

4. An adverse effect on the health of any person

5. Impairment of the safety of any person

6. Rendering any property or plant or animal life unfit for human use

7. Loss of enjoyment of normal use of property

8. Interference with the normal conduct of business

5. Is the adverse effect not trivial or minimal?

If the answer to each question is "yes", the event must be reported forthwith to the MOE pursuant to section 15.