The NRA first warned about the pollution hazards posed by Wheal Jane early in 1991, when the operator, Carnon Consolidated, closed the mine after Government funding for pumping operations ceased (ENDS Report 195, p 8).
The NRA subsequently spent £1 million on a provisional treatment facility which relied on the settlement of metal-contaminated particles in an old tailings dam. But after two months, Carnon stopped pumping water from the mine because winds were delaying settlement of the sediment and there were fears that the dam's capacity might be exceeded. Before pumping could restart, an underground collapse on 13 January led to a massive discharge of 5-7 million gallons of metal-laden waters into the river.
The river ran orange with ochre and polluted coastal waters in Restronguet Creek, which contains a commercial shell fishery. Levels of metals in the river and estuary, which were high even before the Wheal Jane discharge due to other mine effluents, grossly exceeded environmental quality standards (EQSs) for cadmium, arsenic and zinc.
Improvements to the treatment plant during 1992 have trebled its capacity to over 3 million gallons/day. Metal levels in the river returned to near normal in the summer, but the NRA warned that water quality could easily deteriorate if rain increased water levels in the mine.
Last month, the water level rose and discharges increased until up to 2.5 million gallons/day poured into the river. Metal concentrations and loads rose, and the NRA feared that the orange coloration would return to the river.
The new £8 million scheme now promises a long-term solution to the problem. A pilot plant will be established to test alternative methods of treating the discharge and will increase the existing treatment capacity by 20%.
Establishment of the pilot plant will take three years, two of which will be needed for artificial wetland systems to grow to maturity. A full-scale plant will follow once the optimum treatment system has been developed.
Methods which the NRA plans to investigate include anoxic limestone drains and organic slurry ponds for primary treatment, followed by oxidation ditches or settlement ponds and dosing with lime. The wetlands will be used to polish the discharge.
The Wheal Jane case has highlighted the question of who should pay for environmental restoration when the polluter cannot. The NRA pleaded unsuccessfully in its last corporate plan for £12 million to fund work at Wheal Jane and other abandoned mines and contaminated sites (ENDS Report 209, pp 8-9 ).
In now stumping up £8 million for Wheal Jane, the Government was probably influenced by the threat of legal action by the European Commission. In April, Brussels threatened to prosecute the UK for breaching the 1980 Directive on groundwater by failing to prevent discharges of cadmium, arsenic, copper and zinc to groundwater. The UK may also be in breach of the 1976 Directive on dangerous substances in water for failing to prevent pollution by the black list metal cadmium and the grey list metals copper, arsenic and zinc.