Sewerage undertakers' special pollution defence

In an important judgement, the House of Lords has held that sewerage undertakers are not necessarily guilty of an offence of causing water pollution where an illegal discharge into the sewerage system by a third party enters water via sewage treatment works.

National Rivers Authority v Yorkshire Water Services Ltd (17 November 1994) reverses last year's decision of the Divisional Court, and will come as a considerable relief to sewerage businesses.

The case arose out of an incident which occurred at a Yorkshire Water sewage works when an illegal discharge of a solvent, iso-octonal, had been made into the sewers. Such discharges were not permitted under any trade effluent consent in the works' catchment because the solvent could not be treated effectively and would only be diluted as it passed through the works.

This in fact what happened. The iso-octonal was discharged to sewer at night to avoid detection, and its origin was never identified. The chemical flowed through the sewage works and entered the river Spen, causing pollution.

Yorkshire Water had a consent to discharge sewage effluent from the works, but the biochemical oxygen demand caused by the presence of iso-octonal was substantially in excess of the consent limit. The NRA prosecuted the water company for causing poisonous, noxious or polluting matter to enter the river, contrary to section 107(1)(a) of the Water Act 1989 - now to be found in identical terms in the Water Resources Act 1991.

Yorkshire Water was convicted by magistrates in 1991, but appealed successfully against conviction to Wakefield Crown Court. Subsequently, however, the Divisional Court allowed the NRA's appeal on a point of law, and ordered the case to be remitted to the Crown Court with a direction to convict.

It was against this decision of the Divisional Court that Yorkshire Water appealed to the House of Lords. Critical to the interpretation of the case was a special statutory defence provided to sewerage undertakers.

However, the first question which the Lords considered was whether Yorkshire Water could have been held in law to have "caused" the entry of polluting matter when the illegal discharge had been caused originally by an unidentified third party. In the lead judgement, Lord Mackay followed the key decision of the House of Lords in the 1972 case of Alphacell v Woodward concerning water pollution offences where their Lordships had stressed that causation in this context should be given a common sense meaning.

Lord Mackay noted that the discharge in question did not consist solely of iso-octonal, but contained it along with other materials, and that it was the whole discharge which was the subject matter of the prosecution. He concluded: "Yorkshire Water Services having set up a system for gathering effluent into their sewers and thence into their sewerage works there to be treated, with an arrangement deliberately intended to carry the results of the treatment into controlled waters, the special circumstances surrounding the entry of iso-octonal into their sewers and works does not preclude the conclusion that Yorkshire Water Services caused the resulting poisonous, noxious and polluting matter to enter the controlled waters, notwithstanding that the constitution of the effluent was affected by the presence of iso-octonal."

As part of its legal submission, the NRA had argued that a number of decisions had suggested that causation implied a positive act by the accused, and that these amounted to a wrong turning in the law. Lord Mackay declined to deal directly with the point, but said that each of these cases turned on their own facts. In applying an "ordinary" sense to the word "cause", it was necessary for courts to analyse the facts and indicate the reasons why they concluded that the defendants had not caused the pollution in question.

The critical point of the law in the decision turned on the meaning of the special defence in section 108(7) of the 1989 Act (now section 87(2) of the 1991 Act). This provided that a sewerage undertaker shall not be guilty of an offence under section 107 where a discharge contravenes consent conditions if "(a) the contravention is attributable to a discharge which another person caused or permitted to be made into the sewer; (b) the undertaker was not bound to receive the discharge into the works or was bound to receive it there subject to conditions which were not observed; and (c) the undertaker could not reasonably have been expected to prevent the discharge into the sewer or works."

It had been accepted by the Crown Court that in the circumstances of the case all three conditions had been fulfilled. But the Divisional Court had interpreted this section to apply only where an undertaker had been charged with the offence of not complying with consent conditions. This was a different offence from that of causing the entry of polluting matter, and where this latter offence was the basis of the charge, the special statutory defence was not available. The Court had acknowledged this to a restrictive interpretation, and that where, as in a case such as this, the defendants could not reasonably have prevented the polluting discharge, this would be a matter for mitigation.

The House of Lords rejected this approach. In its view, the plain wording of the provisions meant that the special defence was available in respect of any offence charged under section 107. The Divisional Court had recognised that there were few circumstances where there would be a discharge which breached consent conditions but which did not also contravene the wording of the polluting offence, and Lord Mackay concluded that "it would be extremely unusual, if not unique, to enable the prosecutor by choice of allegation in a given state of facts to deprive an accused person of a defence which would be available if the prosecutor took another choice on the same set of facts."

The Divisional Court's decision was undoubtedly strict, and if it had been upheld would have obliged sewerage undertakers to invest in improved detection of illegal trade effluent discharges and in treatment facilities designed to deal with the unexpected. The House of Lords' ruling is a fairer decision in terms of criminal justice, but in the longer run may make life more difficult for the NRA and its successor in curbing water pollution resulting from discharges from sewage treatment works.

Professor Richard Macrory, Director, Environmental Change Unit, Oxford University.

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