In its heyday the Durham coalfield produced over 35 million tonnes of coal per year, but production is now down to one-fifth of this amount and shrinking as British Coal proceeds with its pit closure programme. The latest closures were the Westoe, Vane Tempest and Easington collieries.
The pits are close to the coast but are supported by an extensive pumping operation extending far inland into the Wear valley. Massive volumes of groundwater are pumped out upstream of Durham and the population centres of Chester-le-Street, Washington and Sunderland. The operation is believed to cost British Coal o6 million annually.
British Coal has been attempting to sell Vane Tempest and Westoe and agreed to continue pumping only while offers were considered. At the end of August, however, it revealed that no bids had been received from the private sector to resume mining at either pit. A decision on the pumping operation therefore appears to be imminent.
Turning off the pumps would allow groundwater to rise and flood abandoned mine workings upstream of Durham. According to British Coal, the environmental consequences would be minimal because the groundwaters would only reach the surface via existing mine adits near the coast. The NRA regards this as a highly optimistic view, and has commissioned two successive hydrogeological studies from consultants Wardell Armstrong.
The studies describe the groundwaters of the coalfield as three cascading underground "pools". The highest is in the west, upstream of Durham, the second lies to the north, upstream of Chester-le-Street, and the third and lowest lies along the coast to the east.
British Coal's pumping strategy removes 16 million cubic metres of water annually from the highest pool to prevent overflow to the deeper levels where pumping costs would be greater. The most recent study has concentrated on the likely effects of rising groundwaters in this area.
Hydrological models show that the upper pool will overflow into the river Wear 3-12 months after pumping ceased. When the flow equilibrates, over 9,000m3 of acidic, iron- and sulphate-rich water will enter the river annually.
According to the NRA, the worst scenario is the total destruction of life in the Wear. The river is Class 1B between Bishop Auckland and Durham, where most of the overflow will occur, and supports salmonoid and coarse fisheries, a major drinking water abstraction at Lumley near Chester-le-Street, and various amenity uses.
The economic consequences for the area would be severe, the iron-stained river would become an eyesore through the tourist centre of Durham, and North East Water's abstraction point would have to be relocated at a cost of o25 million.
The NRA estimates the cost of maintaining sufficient pumping of the upper pool to prevent overflow to be o200,000 per year. However, the consultants' reports suggest that this will provide only a short-term solution.
Minewaters in the second pool will overflow to the river within about 30 years if pumping ceases lower down the river. This would threaten the Lumley intake, but of more immediate concern would be the possibility of overflow back into the first pool. This could occur within 15 years and add to the pumping costs upstream.
British Coal maintains that it is working closely with the NRA with a view to "agreeing an appropriate course of action...should the company decide that it can no longer sustain pumping operations". It has agreed to give "at least" 14 days notice of the pumps being switched off.
If pumping stops, the NRA will be forced to intervene to protect the river. However, it has no budget for remedial works of this scale and, without specific Government funding, could only try to recover costs from abstractors.
Last year, the Department of the Environment (DoE) provided o8 million for treating minewaters from the Wheal Jane tin mine after it caused extensive water pollution (ENDS Report 215, p 10 ). But the NRA says that it has received no assurances from the DoE about funding to clean up Durham minewaters.
The Water Resources Act 1991 empowers the NRA to recover the costs of remedial works from the polluter, but the NRA regards the legal position of mine pollution as "highly ambiguous". Section 89 of the Act excludes mine owners from liability for pollution from abandoned mines, but only when the discharge of waters has been "permitted" and not when it has been "caused".
The issue has never been tested in court. The NRA did not bring proceedings against the owners of the Wheal Jane mine because it was unlikely to obtain damages from its near-bankrupt owners (ENDS Report 195, p 8).
The first test case will not be brought by the NRA, however, but by the Anglers' Cooperative Association, which has initiated proceedings against British Coal for alleged pollution of the river Rhymney, in south Wales, following the closure of the Britannia colliery in 1990. The case is likely to come to court in the autumn.
If British Coal stops pumping at Durham, the NRA is unlikely to allow the opportunity to test the law to pass. Its argument would be that turning off the pumps would amount to "causing" pollution, although earlier NRA prosecutions have foundered on this point (see ENDS Report 213, p 39 ).
The DoE appears confident that the law is in the NRA's favour. Environment Minister Tony Baldry told the House of Commons in July that it is "clearly an offence for mine owners, such as British Coal, to cause pollution of water courses, regardless of whether a mine is active or abandoned".