HC Deb 02 March 1992 vol 205 cc52-3W
Mr. Barry Field

To ask the Secretary of State for the Environment whether he has received the report by the drinking water inspectorate on the incident at the Iver treatment works of Three Valleys Water in July 1991; and if he will make a statement.

Mr. Trippier

I have now received the drinking water inspectorate's report on the incident at the Iver treatment works in July 1992, and copies have been placed in the Library of the House. A summary of the findings and recommendations is being made widely available.

The inspectorate found that the normal disinfection processes failed on Saturday 20 July 1991 because, when a changeover occurred from one bulk liquid chlorine storage tank to another tank, a valve on the outlet from the second tank was not opened and remained shut for 41/2 hours. The effect of this failure was mitigated however by mixing that occurs at the treatment works and in the distribution networks part of the normal operation of the system, and by the fact that chlorine is applied at various stages. Having weighed all the evidence, the inspectorate has concluded that there is no reason to believe that the water supplied by the company in the period following the incident was unfit for human consumption. Any breach of the quality standards in the Water Quality Regulations is likely to have been trivial.

The inspectorate is critical of the company for not taking appropriate remedial action at the works within a reasonable period. It has nevertheless concluded that, on the basis of the situation at that time and the information available, senior management took a prudent decision on the Saturday night to issue advice to consumers to boil water. However the water undertakers owned by Three Valleys Water which supply water from the Iver works, Colne Valley Water Company Plc and Rickmansworth Water Plc, contravened the Water Quality Regulations by failing to notify each local authority and district health authority affected by the incident. At the time of the incident there were no powers to take enforcement action in relation to a contravention of this nature, but I can confirm that this gap in the legislation has now been filled for the future.

The report identifies specific deficiencies in the instrumentation at the Iver works, in operational and management procedures, in emergency plans, and in contingency plans for communicating with consumers in such circumstances. Although microbiological analysis would not have provided results until the following day, the inspectorate is nevertheless critical of the company's failure to carry out comprehensive sampling and analysis particularly of water leaving the Iver works. The report also identifies weaknesses in the response to the incident by local authorities and district health authorities.

The report puts forward 13 recommendations. Most of these have already been met by action which Three Valleys Water has subsequently taken, and the company has accepted the remaining recommendations. Some of the recommendations about contingency planning also require the co-operation of the relevant local authorities, district health authorities and police forces, and of the media, and I hope that this will be forthcoming.

In a covering letter to the report, the chief inspector has drawn attention to a number of points which have implications for the approach adopted by water companies generally to preventing failures of disinfection and ensuring that the necessary contingency plans are in place. I have accepted the conclusions and recommendations of the report, and the chief inspector's advice that further guidance should be given to all water companies on these matters. He will be writing to companies promptly for this purpose, and special attention will be paid to emergency procedures in the annual inspections of water companies.

In the light of the conclusions of this report, my Department will discuss with the Department of Health and the Home Office whether further guidance needs to be given to local authorities and health authorities about their role in responding to incidents affecting water supply. To ensure that liaison with the media functions effectively on future occasions and to secure a prompt response, we are also drawing the attention of water companies to the BBC guide on facilities for broadcasting emergency announcements. We are recommending them to make appropriate standing arrangements both with the BBC and with other television and radio stations serving their areas.

The inspectorate's report is commendably thorough. The findings that, although we have a very high standard of drinking water in this country, and this particular incident did not cause damage to health, there is scope for improving procedures in order to provide more effective safeguards for the future. I confirm that the necessary action has either been taken or is in hand.