Overseas Tankship (UK) Ltd v The Miller Steamship Co [1966] UKPC 10 (Wagon Mound no 2)

Overseas Tankship’s ship Wagon Mound leaked furnace oil in Sydney harbour. Welding sparks ignited it, destroying nearby repair ships. The Privy Council held that even a very small but serious risk must be guarded against if reasonably foreseeable, shaping negligence breach analysis.

Facts

Overseas Tankship (UK) Ltd chartered a freighter, the Wagon Mound, which was taking on bunker oil at Mort’s Dock in Sydney. Due to carelessness by the ship’s engineers, a large quantity of oil overflowed onto the surface of the water. After several hours, the oil drifted to the vicinity of two vessels owned by the Miller Steamship Co that were being repaired nearby. Sparks from welders working on those vessels ignited the oil, and all three ships were destroyed by fire.

At first instance in the Supreme Court of New South Wales, Walsh J made factual findings that: (1) the officers of the Wagon Mound would regard oil as very difficult, but not impossible, to ignite on water; (2) ignition of oil on water had very rarely occurred; and (3) it was a possibility that would materialise only in very exceptional circumstances. On those findings he held that Overseas Tankship was not liable in negligence, but that the large quantity of oil constituted a public nuisance for which Overseas Tankship was liable in damages.

Overseas Tankship obtained leave to appeal directly to the Privy Council on the nuisance finding. Miller Steamship Co obtained leave to cross-appeal on the dismissal of its negligence claim.

Issues

The key issues before the Judicial Committee of the Privy Council were:

• Whether, in nuisance, it was sufficient for liability that the fire damage was the direct result of the oil pollution, even if that particular damage was unforeseeable.
• Whether, in negligence, a reasonable person in the position of the ship’s engineer ought to have foreseen a real risk that the oil on the water might catch fire, notwithstanding that such an event was unlikely and had rarely occurred.
• More broadly, how the test for breach of duty of care in negligence should accommodate a low likelihood of harm where the potential consequences are extremely serious.

Judgment

The Privy Council upheld both the appeal and the cross-appeal. It held that it was not enough, for nuisance, that the damage to the Miller Steamship vessels was the direct consequence of the oil pollution if that particular kind of damage was unforeseeable. Thus, unforeseeable damage could not be recovered in nuisance merely because it was directly caused by the defendant’s act.

Turning to negligence, the Privy Council held that a reasonable person in the position of the ship’s engineer would have been aware of the risk of fire arising from oil floating on water. Although the probability of ignition was small, the gravity of the potential damage from a fire of this kind was extremely great. In such circumstances there was no adequate excuse for allowing the oil to be discharged.

The Board reasoned that a reasonable person would only choose to run a risk of such potentially grave magnitude if there were a justification for doing so, such as prohibitive cost or some other compelling reason. In the absence of such justification, a failure to guard against even a small but real risk of catastrophic harm amounted to a breach of duty of care.

Lord Reid stated at 718–719:

It follows that in their Lordships view the only question is whether a reasonable man, having the knowledge and experience to be expected of the chief engineer of the Wagon Mound, would have known that there was a real risk of the oil on the water catching fire in some way.

The judgment explained that the phrase “real risk” expresses the requirement that the damage must not be too remote, but that the test of foreseeability does not turn on the statistical likelihood of the occurrence alone. The essential question is whether the type of consequence (here, the outbreak of fire) ought to have been foreseen by a person in the defendant’s position.

Implications

Wagon Mound (No. 2) is a landmark tort decision on the test for breach of duty in negligence. It complements the earlier Wagon Mound (No. 1), which introduced remoteness as a rule of causation to limit compensatory damages, by clarifying that even very unlikely harms must be guarded against when the potential seriousness is great and the precautions are reasonable.

The case articulates a balancing approach between the magnitude and seriousness of the risk and the cost or burden of taking precautions, similar to the formulation associated with Learned Hand in United States v. Carroll Towing Co. The decision has been influential in framing negligence analysis in terms of whether a reasonable person would eliminate a low-probability but high-consequence risk absent some countervailing justification.

The holding has, however, attracted academic criticism. Leon A. Green, for example, attacked the case for its “overloading of the foreseeability concept”, suggesting that the decision stretches foreseeability beyond its proper function in negligence doctrine.

Verdict: The Privy Council upheld both the appeal and the cross-appeal, holding that unforeseeable damage was not recoverable in nuisance and that, in negligence, the risk of fire from oil on the water was a real, foreseeable risk that ought to have been guarded against.

Source: Overseas Tankship (UK) Ltd v The Miller Steamship Co [1966] UKPC 10 (Wagon Mound no 2)