Almost one in 10 of the State's public drinking water supplies is unsatisfactory, according to the latest water quality report from the Environmental Protection Agency (EPA). The report also found that many rural supplies continue to be grossly polluted.
Overall, the quality of public water supplies in 1999 was "satisfactory", with 92 per cent of samples tested being "fully acceptable", the EPA's report for last year says.
It says fluctuations in quality occurred due to natural or seasonal variations, or as a result of "once-off" contaminations.
Group water schemes showed a "modest" improvement over 1998, but only 62 per cent of those tested were fully compliant. The main causes of contamination are domestic and agricultural - due to intensified animal rearing and spillage of silage effluents or slurries. In the case of domestic contamination, the main source is faulty septic tanks or other household waste systems.
The EPA receives results for about one fifth of all group water schemes, amounting to 5,500 nationwide, but acknowledges the Department of the Environment is involved with local authorities and the National Federation of Group Water Schemes in a "vigorous" programme to improve the quality of rural water supplies.
Bacteriological contamination was regarded as the main problem in group schemes, according to Dr Paddy Flanagan of the EPA. "If this could be addressed, we'd be well on our way to an improvement," he told The Irish Times yesterday. However, as his report notes, the smaller the scheme, the higher risk of contamination.
"All concerned with group water schemes and small supplies must be constantly vigilant to avoid contamination of sources by run-off from on-site waste-water treatment systems or agricultural slurry," he says.
The most significant measure of quality is absence of human or animal faeces. The report compiled by the EPA relies on data collected by the sanitary authorities, and includes results from 18,000 samples taken from over 3,000 supplies.
About 4 per cent of unsatisfactory supplies contain non-faecal coliforms, which can usually be addressed through clearing mains distribution systems. The balance of 4 per cent of offending supplies may be "an overestimate", according to Dr Flanagan.
"If a local authority detects a problem, it takes additional samples and may even provide an alternative water supply for the duration. Some of the samples submitted to us may relate to water that is not being delivered to consumers," he said.
The 1999 results are generally consistent with those collected over the past six years, with modest improvements in some areas. Dr Gerry Cowley, chairman of the National Federation of Group Water Schemes, said he welcomed the findings, and the Government's £420 million funding of the rural water programme was having an impact.
"No one is more aware than me about problems in quality of drinking water, but I see a solution in sight, with new technology being applied in several group schemes," he said yesterday. "County strategic plans drawn up in co-operation with local monitoring committees will also improve the situation. In Mayo, for instance, we are just about ready for the first draft of that."
Lack of resources by successive governments had been a major problem, Dr Cowley said. The federation had harnessed a "great voluntary effort" which was contributing to improvements, he added.
