The issues on appeal were:
i. Did the trial judge err in holding that the discharge of the nickel particles by Inco on to the property of the class members constituted an actionable nuisance?
ii. Did the trial judge err in holding that Inco was liable for the discharge of the nickel particles under the rule established in Rylands v. Fletcher?
iii. Did the trial judge err in holding that the claimants had established a diminution in value of their properties after September 2000?
iv. Did the trial judge err in holding that assuming there was a diminution in the value of the properties after September 2000, that diminution was caused by the discharge of nickel particles on to the land?
v. Did the trial judge err in failing to hold that the claim was time barred under s. 45(1)(g) of the Limitations Act?
The Court allowed the appeal on the basis that the property owners failed to establish Inco's liability under either private nuisance or the rule in Rylands v. Fletcher (which is basically that a landowner cannot allow a harmful substance to flow from his or her property onto a neighbouring property). Alternatively, if liability had been found, the Court of Appeal would still have found that the property owners failed to prove that they suffered any damages.
Here is some of what the Court said about the tort of nuisance:
People do not live in splendid isolation from one another. One person’s lawful and reasonable use of his or her property may indirectly harm the property of another or interfere with that person’s ability to fully use and enjoy his or her property. The common law of nuisance developed as a means by which those competing interests could be addressed, and one given legal priority over the other. Under the common law of nuisance, sometimes the person whose property suffered the adverse effects is expected to tolerate those effects as the price of membership in the larger community. Sometimes, however, the party causing the adverse effect can be compelled, even if his or her conduct is lawful and reasonable, to desist from engaging in that conduct and to compensate the other party for any harm caused to that person’s property. In essence, the common law of nuisance decided which party’s interest must give way. That determination is made by asking whether in all the circumstances the harm caused or the interference done to one person’s property by the other person’s use of his or her property is unreasonable: Royal Anne Hotel Co. Ltd. v. Village of Ashcroft (1979), 95 D.L.R. (3d) 756 (B.C.C.A.), at pp. 760-61.
[...]On the rule in Rylands v. Fletcher, the Court wrote:
In our view, actual, substantial, physical damage to the land in the context of this case refers to nickel levels that at least posed some risk to the health or wellbeing of the residents of those properties. Evidence that the existence of the nickel particles in the soil generated concerns about potential health risks does not, in our view, amount to evidence that the presence of the particles in the soil caused actual, substantial harm or damage to the property. The claimants failed to establish actual, substantial, physical damage to their properties as a result of the nickel particles becoming part of the soil. Without actual, substantial, physical harm, the nuisance claim as framed by the claimants could not succeed.
The rule in Rylands v. Fletcher imposes strict liability for damages caused to a plaintiff’s property (and probably, in Canada, for personal damages) by the escape from the defendant’s property of a substance “likely to cause mischief”. The exact reach of the rule and the justification for its continued existence as a basis of liability apart from negligence, private nuisance and statutory liability have been matters of controversy in some jurisdictions: see Transco plc v. Stockport Metropolitan Borough Council,  2 A.C. 1 (H.L.); Burnie Port Authority v. General Jones Pty. Ltd. (1994), 179 C.L.R. 520 (Aust. H.C.); Murphy, “The Merits of Rylands v. Fletcher”. In Canada, Rylands v. Fletcher has gone largely unnoticed in appellate courts in recent years. However, in 1989 in Tock, the Supreme Court of Canada unanimously recognized Rylands v. Fletcher as continuing to provide a basis for liability distinct from liability for private nuisance or negligence.
[...]The Court of Appeal found that there was no liability under this doctrine because Inco's use of its property was not a "non-natural use".
There are various formulations of the rule found in the case law and the academic commentary. The authors of The Law of Nuisance in Canada suggest different potential formulations, including one, at p. 113, that requires four prerequisites to the operation of the rule:
• the defendant made a “non-natural” or “special” use of his land;• the defendant brought on to his land something that was likely to do mischief if it escaped;• the substance in question in fact escaped; and• damage was caused to the plaintiff’s property as a result of the escape.
Finally, although the Court of Appeal did not have to address the limitation period issue in order to make its decision, it did provide a brief commentary on the issue because of its potential effect on future cases. The Court cautioned that discoverability is often an individual issue requiring individual adjudication after common issues (such as liability and damages, in this case) have been decided. The trial judge in this proceeding had made a ruling on a limitation period defence on the basis that "most property owners" would not have been aware of the potential effect of nickel contamination as of a certain date. The Court of Appeal ruled that the limitation issue could not be decided in that way in the trial of common issues:
If, as the trial judge found in this case, the evidence does not establish that all class members were not aware of and ought not to have been aware of the material facts, then the application of the Limitations Act to the claims is an individual and not a common issue.Read the full decision at: http://canlii.ca/s/6lhbs.