Environment Agency v Empress Car Co (Abertillary) Ltd [1999] 2 AC 22

Empress Car Company stored diesel in a tank with unsafe withdrawal arrangements so that an unknown person could open an unlocked tap, causing diesel to enter a nearby river. The House of Lords held the company had "caused" the pollution under strict liability, clarifying causation where third-party acts intervene.

Facts

Empress Car Company (Abertillery) Ltd maintained a diesel fuel tank in a yard close to the River Ebbw Fach, which constituted controlled waters under the Water Resources Act 1991. The yard drained directly into the river.

The tank was surrounded by a bund intended to contain any spillage, but the company defeated this safeguard by attaching an extension pipe to the tank outlet so that diesel could be drawn from a drum standing outside the bund. The outlet tap had no lock.

On 20 March 1995 an unknown person opened the tap. The entire contents of the tank flowed into the drum, overflowed into the yard, then went through the storm drain into the river. There was local hostility to the company’s business, and the incident coincided with a public inquiry about a disputed footpath. The Crown Court found the tap might have been turned on by a malicious intruder, an aggrieved visitor, an upset local person or an employee but made no finding as to identity.

The company was convicted at first instance, and its appeal to the Crown Court and by way of case stated to the Divisional Court was dismissed. It then appealed to the House of Lords.

Issues

1. Requirement of a positive act

The company argued that conviction for “causing” pollution under section 85(1) of the Water Resources Act 1991 required a positive act by the defendant, and that it had merely created a state of affairs in which someone else could make the oil escape. It submitted that only the unknown person who opened the tap could be said to have caused the oil to enter the river.

Lord Hoffmann noted that section 85(1) contains two limbs, “causes” and “knowingly permits”. Referring to Lord Wilberforce’s analysis in Alphacell Ltd v Woodward, he cited:

"The subsection evidently contemplates two things–causing, which must involve some active operation or chain of operations involving as a result the pollution of the stream; knowingly permitting, which involves a failure to prevent the pollution, which failure, however, must be accompanied by knowledge."

The company maintained that there had been no such “active operation” on its part.

2. Causation where third parties or natural events intervene

The central issue was whether, in circumstances where an unknown person opened the tap, the company could nonetheless be said to have “caused” the diesel to enter the river for the purposes of section 85(1).

Lord Hoffmann emphasised that causation in this context is a matter of common sense, but it must be addressed in light of the statutory purpose and the strict liability imposed by section 85(1). He quoted Lord Salmon in Alphacell:

"what or who has caused a certain event to occur is essentially a practical question of fact which can best be answered by ordinary common sense rather than by abstract metaphysical theory."

He also cited Lord Wilberforce’s warning in Alphacell about unnecessary refinements:

"In my opinion, ‘causing’ here must be given a common sense meaning and I deprecate the introduction of refinements, such as causa causans, effective cause or novus actus. There may be difficulties where acts of third persons or natural forces are concerned . . ."

The question became how to treat deliberate third-party acts or natural events that were necessary conditions for the escape, and in particular whether such acts always broke the chain of causation initiated by the defendant.

Judgment

Approach to acts and omissions

All members of the Appellate Committee agreed that some form of “active operation” or “positive act” is required for liability under the “causing” limb, because the second limb separately captures liability for “knowingly permitting” pollution. However, they rejected a narrow concept of what counts as a positive act.

Lord Hoffmann held that the requirement of a positive act does not mean the defendant’s conduct must be the immediate cause of the escape. He criticised earlier decisions which had taken too restrictive a view, such as Price v Cromack and Wychavon District Council v National Rivers Authority, explaining that these cases had wrongly insisted that the defendant’s act must be the immediate cause.

He endorsed Lord Mackay’s observation in National Rivers Authority v Yorkshire Water Services Ltd that:

"the word ’cause’ should be used in its ordinary sense and that "it is not right as a matter of law to add further requirements.""

Maintaining installations such as tanks, lagoons or sewage systems containing polluting matter is itself “doing something” and can constitute the requisite positive act, even if the immediate escape is triggered by a third party or a natural event.

Lord Clyde likewise warned against overlaying the statutory term with additional tests:

"the word ’cause’ is to be used in its ordinary sense in these provisions and it is not right as matter of law to add further requirements."

He considered “positive act” to be a potentially misleading label and instead adopted Lord Wilberforce’s expression of “active operation” merely as a reminder that “absolute passivity is not enough”. He stressed that:

"The maintaining of a system, the carrying on of an enterprise, and the management of a going concern may each constitute causative factors."

Failures to take precautions in the running of such premises could be analysed as part of the defendant’s active operations.

Causation and the role of third parties and natural forces

Lord Hoffmann gave a detailed analysis of causation tailored to the policy and structure of section 85(1). He stressed that asking in abstract “What caused the pollution?” is misleading, because multiple causes may coexist. The correct statutory question is:

"Did the defendant cause the pollution?"

That another person or factor also caused it does not preclude the defendant from having caused it as well.

He emphasised that, in both law and common sense, special significance is often attached to deliberate human acts and extraordinary natural events when attributing responsibility. However, section 85(1) imposes strict liability “in the nature of a public nuisance”, so liability does not depend on fault or foreseeability in the negligence sense. Referring to previous authorities, he explained that foreseeability is not the test for causation under this provision:

"the question is not whether the consequences ought to have been foreseen; it is whether the defendant caused the pollution. And foreseeability is not the criterion for deciding whether a person caused something or not. People often cause things which they could not have foreseen."

Instead, Lord Hoffmann identified the true distinction as lying between:

"acts and events which, although not necessarily foreseeable in the particular case, are in the generality a normal and familiar fact of life, and acts or events which are abnormal and extraordinary."

Ordinary occurrences such as leaky pipes, malfunctioning equipment, or vandalism of a routine kind will not break the chain of causation. They are treated as part of the ordinary risks of operating installations containing polluting matter. By contrast, highly unusual events, such as terrorist attacks or truly extraordinary natural disasters, may be so abnormal that they negative the causal connection between the defendant’s conduct and the pollution.

Lord Hoffmann illustrated this approach by reference to Alphacell, where pumps became choked with vegetation, causing an overflow:

"There was not even any unusual weather or freak of nature. Autumn is the season of the year in which dead leaves, ferns, pieces of bracken and pieces of bramble may be expected to fall into water and sink below the surface and, if there is a pump, to be sucked up by it. . . ."

Such occurrences were normal hazards of the operation, so the defendant could still be said to have caused the pollution.

On this reasoning, the House concluded that earlier decisions such as Impress (Worcester) Ltd v Rees and National Rivers Authority v Wright Engineering Co Ltd, which had treated deliberate third-party acts as automatically breaking the chain of causation, were wrongly decided or unduly restrictive. Lord Hoffmann stated that the reasoning in Impress could not stand in light of Alphacell and Yorkshire Water.

Guidance for magistrates

Lord Hoffmann distilled his analysis into a structured series of guidance points for magistrates considering prosecutions under section 85(1):

"(1) Justices dealing with prosecutions for "causing" pollution under section 85(1) should first require the prosecution to identify what it says the defendant did to cause the pollution. If the defendant cannot be said to have done anything at all, the prosecution must fail: the defendant may have "knowingly permitted" pollution but cannot have caused it.
(2)  The prosecution need not prove that the defendant did something which was the immediate cause of the pollution: maintaining tanks, lagoons or sewage systems full of noxious liquid is doing something, even if the immediate cause of the pollution was lack of maintenance, a natural event or the act of a third party.
(3) When the prosecution has identified something which the defendant did, the justices must decide whether it caused the pollution. They should not be diverted by questions like "What was the cause of the pollution?" or "Did something else cause the pollution?" because to say that something else caused the pollution (like brambles clogging the pumps or vandalism by third parties) is not inconsistent with the defendant having caused it as well.
(4) If the defendant did something which produced a situation in which the polluting matter could escape but a necessary condition of the actual escape which happened was also the act of a third party or a natural event, the justices should consider whether that act or event should be regarded as a normal fact of life or something extraordinary. If it was in the general run of things a matter of ordinary occurrence, it will not negative the causal effect of the defendant’s acts, even if it was not foreseeable that it would happen to that particular defendant or take that particular form. If it can be regarded as something extraordinary, it will be open to the justices to hold that the defendant did not cause the pollution.
(5) The distinction between ordinary and extraordinary is one of fact and degree to which the justices must apply their common sense and knowledge of what happens in the area."

Application to the facts

Applying these principles, the House held that the company’s manner of maintaining its diesel tank and fuel system was an operative cause of the pollution. Lord Hoffmann observed that the Crown Court had found the escape was caused by the way the company maintained its tank. Maintaining such a tank with an extension pipe bypassing the bund and an unlocked tap, in premises subject to local opposition and unsecured against interference, constituted a relevant “active operation”.

Lord Clyde agreed that the critical question was whether the appellant had caused the oil to enter the controlled waters, not merely to leave the tank. He emphasised:

"It must involve some kind of active operation by the defendant whereby, with or without the occurrence of other factors, the pollutant enters the controlled waters."

He concluded that, having regard to the exposed and unguarded tap, the unsecured nature of the premises, the existence of local hostility, and the direct layout from tank to yard to drain to river, it was open to the courts below to hold that the appellant caused the pollution. He regarded the possible intervention of an intruder as not being “out of the ordinary course” in those circumstances.

Accordingly, the House held that there was ample evidence on which the Crown Court could find that the company had caused the diesel oil to enter the river.

Implications

This decision clarifies the interpretation of “causing” in section 85(1) of the Water Resources Act 1991 and similar environmental offences. It establishes that:

• Liability is strict and does not depend on negligence, intention, knowledge, or foreseeability in the tortious sense.
• Maintaining installations or systems containing polluting matter can be a sufficient positive act for the purposes of “causing” pollution.
• The fact that a third party or natural event is a necessary condition of the escape does not automatically break the chain of causation; the focus is on whether such an act or event is an ordinary or extraordinary occurrence.
• Causation must be assessed in light of the statute’s protective purpose, and courts should avoid introducing additional technical requirements beyond the ordinary meaning of “cause”.

The case provides detailed guidance for magistrates and higher courts on how to analyse causation where pollution results from a combination of the defendant’s operations and third-party acts or natural events. It also effectively disapproves narrow readings in earlier authorities that treated deliberate third-party acts as necessarily superseding the defendant’s responsibility.

The House of Lords ultimately concluded that Empress Car Company’s configuration and operation of its fuel storage arrangements caused the diesel to enter the river, and upheld the conviction.

Verdict: Appeal dismissed; the company’s conviction for causing polluting matter to enter controlled waters under section 85(1) of the Water Resources Act 1991 was upheld.

Source: Environment Agency v Empress Car Co (Abertillary) Ltd [1999] 2 AC 22