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12.33 pm
The Parliamentary Under-Secretary of State for the Environment (Mr. James Clappison): I can give the hon. Member for Torridge and West Devon (Miss Nicholson) assurance on the points that she raised. I shall set out the important issues implicit in
the incident and, especially, our understanding of the cause of the incident on the River Claw; the remedial and other measures that were taken by the Environment Agency in its aftermath; whether any longer-term effects will arise from the incident; what action may be taken as a result of the incident; and our policy on minimising the risk of water pollution from agricultural sources.
I should, however, like to begin by thanking the public-spirited member of the public, to whom the hon. Member for Torridge and West Devon referred, who brought the incident to the attention of the Environment Agency and thereby allowed action to be taken at an early stage. I understand that the alert was given using the 24-hour free emergency pollution hotline which the agency operates and which was introduced by the National Rivers Authority in 1993. Last year, the hotline handled more than 30,000 calls, all of which were intended to allow prompt action to be taken to help protect the water environment. Once again, that initiative has shown its worth.
The hon. Member for Torridge and West Devon gave a description of the River Claw, which is a tributary of the Tamar. The catchment is predominantly intensively farmed grassland, used for stock rearing. The origin of the incident appears to have been a stock farm in the upper reaches of the Claw near Holsworthy. The cause of the pollution, which the hon. Lady described, seems to have been liquid farm waste that contained some slurry. The hon. Lady called the liquid "poisonous" and I will describe its effects later, but it is important to clarify that it was liquid manure.
Slurry is organic waste. It is polluting not because it is persistent or contains toxic substances but because it has a high biochemical oxygen demand--in other words, it depletes oxygen levels in waters which it enters because micro-organisms have to absorb additional oxygen to break down the organic material. The biochemical oxygen demand of cattle slurry may be up to 12,000 mg per litre compared to perhaps 50 mg per litre for treated domestic sewage. Thus it has a severe, if relatively short-lived, impact. That is why we have measures in place to require slurries to be stored in a safe manner--measures to which I shall return later.
In the incident on 9 June, a large quantity of liquid waste appears to have drained from a store to a "low rate" irrigation system used for disposal of dirty water by sprinkling to land, as the hon. Member for Torridge and West Devon mentioned. As a result, the polluted water was spread on to land by the irrigator and then entered the land drainage system and the river, resulting in the incident on Sunday afternoon 9 June.
Spreading dirty water to land to dispose it under controlled conditions is generally an acceptable method, but in this case the effects were disastrous. I understand the points made by the hon. Lady, but at this stage it remains unclear to the Environment Agency why the polluting matter drained from the store to the dirty water disposal system and why there was such a rapid loss of liquid from the store. It seems that the irrigator itself may have been operated in a manner that does not accord with the guidance given in the Government's code of good agricultural practice.
Miss Emma Nicholson:
The farmer's waste management system had been cleared 100 per cent.
Mr. Clappison:
I am sure that the hon. Lady will accept that I was trying to be precise when I described the exact effects of slurry. The important point, as I am sure she will agree, is the effect of slurry on fish and other wildlife. The hon. Lady's description of the incident is based on the information she has, but the matter will be subject to further investigation and I will describe that later. I hope that the hon. Lady will understand if I am somewhat circumspect in my remarks about the incident.
Whatever the cause, the effects of the entry of the polluting matter were severe. Oxygen levels in the Claw fell from 88 per cent. saturation, which is about what would normally be expected, to zero. About 3 km of the river turned dark brown. As a result, there was considerable fish mortality in the stretches affected before remediation began. The agency estimates that between 2,500 and 3,000 fish may have died, of which perhaps about 400 were brown trout.
The agency took remedial measures and initially focused on providing information to other relevant bodies and assessment of the polluting impact of the incident in order to concentrate remedial action in the most effective manner. The closest abstraction point for potable supply is about 45 km from the incident, so there was no threat to drinking water supply.
One of the main strands of remedial action was to save as many fish as possible. That was achieved with considerable success, I am pleased to say. About 1,700 fish were saved, of which over half were either trout or juvenile salmon. These fish were transferred to waters downstream of the incident. The second strand was to remove the polluted water from the river through pumping. Again this proved successful. The third was to re-oxygenate the river as rapidly as possible. This was achieved through the insertion of a mechanical whisk in the polluted stretch that re-aerates the water, as well as the use of other aeration equipment at other strategic sites in the Claw, to assist re-oxygenation. In addition, hydrogen peroxide--it is a strong oxidising agent--was used to introduce oxygen at strategic sites.
These remedial measures were undertaken between 9 and 12 June. By 12 June the oxygen levels in the Claw had recovered to the standards before the incident and remediation ceased. The incident was declared closed by the agency on 12 June.
The longer-term effects of the incident will be of concern. Slurry is biodegradable and the pollution was therefore primarily transient. The Claw is categorised as a class 2 river under our river ecosystem classification system, which requires, among other things, a dissolved oxygen level of better than 70 per cent. saturation. It is unlikely that there will be any longer-term diminution in the high quality of the river as a result of the incident. The agency will, however, be monitoring the manner in which the river recovers from the incident.
The main longer-term effects will be in relation to biological communities in the river. It may take up to 12 months for the invertebrates to recover. For fish, the
recovery period will be even longer. The agency will be considering whether there is a need to improve spawning grounds to assist the development of fish populations. An alternative would be to introduce new stock to the river. As I have said, the incident had no consequences for any public use of the river, including drinking water supply.
The agency made use of its powers under section 161 of the Water Resources Act 1991 to undertake remedial work. It is now open to the agency to seek to recover the costs that it has incurred from any person who may have caused or knowingly permitted the polluting matter to enter the river, so that the polluter pays for the costs associated with his actions. I understand that the agency intends to take such action. I noted the hon. Lady's support for the important principle that the polluter must pay.
The agency has been gathering information that might be used to support a prosecution for an offence of polluting controlled waters under the 1991 Act. A decision on whether to take such action will be a matter for the agency. It is, however, the agency's policy to prosecute major pollution incidents where there is sufficient evidence and it is possible to do so as the person concerned can be identified. For the reasons I gave following the hon. Lady's intervention, I do not wish to say any more on that subject. I have set out the general legal framework that applies to this incident and to all others.
It has long been an offence under water pollution law to cause or knowingly permit the entry of poisonous, noxious or polluting matter to fresh waters. This approach has been successful in ensuring that those who undertake actions that are potentially polluting do so in the knowledge that they are liable for the consequences to the water environment of their actions. We should all recognise, however, that, although it is important to be able to take action where pollution has occurred, it is better to prevent that pollution in the first place.
Accordingly, in the agriculture sector, the Government have adopted an approach that employs both regulatory controls and advice and guidance to farmers and growers on how to carry out their activities in a manner that reduces the risk of water pollution. That is important. The guidance is found primarily in the code of good agricultural practice produced by the Ministry of Agriculture, which is being revised. The code has proved highly successful in setting out for farmers, their staff and contractors who handle, store, use, spread or dispose of any substances that could pollute water, the causes and results of water pollution, how best to minimise the risk of such pollution through their operations and what to do in an emergency.
The code includes extensive guidance on the principles of storing and applying livestock wastes and other organic wastes to land as well as the storage of slurry and the operation of dirty water systems. The guidance supports the regulatory requirement which we have introduced for the storage of slurry via the control of pollution regulations of 1991. The regulations specify that slurry must be kept in a reception pit or slurry storage tank, whether this is a pit, lagoon or above-ground store. They set out minimum requirements for the design and construction of such facilities.
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