The duty to report depended on whether there had been a discharge within the meaning of Section 14(1) of the EPA. Section 14(1) prohibits a discharge of a contaminant into the natural environment if the discharge causes or may cause an adverse effect. "Adverse effect" is a defined term in the Act, and the majority of the Court of Appeal panel found that for the harms listed in subparagraphs (b) to (h), there is no requirement that there necessarily be harm to the environment (i.e. there can be an adverse effect for the purposes of Section 14(1) without harm to the environment). On this basis, although the "fly-rock" caused no apparent harm to the environment, the conviction was upheld.
Justice Robert Blair wrote a dissenting opinion. His view was that there could be no "adverse effect" without either non-trivial harm or impairment of the natural environment. As it was conceded that the "fly-rock" had no more than a trivial or minor impact on the natural environment, Justice Blair would have allowed the appeal.
Read the decision at: Ontario (Environment) v. Castonguay Blasting Ltd.