'No barriers' let bug into water

Testing at the reservoir showed no breach of standards

A stomach bug which left hundreds ill entered the north Wales water supply because treatment procedures were not sufficient, says an official report.

A total of 231 people became sick from cryptosporidium last winter.

Welsh Water had not needed measures to kill the bug because it was thought it would be diluted in a reservoir, but there had been "no effective barriers" to stop it reaching the mains supply.

Welsh Water said its new ultra-violet treatment would kill the bug.

Around 70,000 homes in parts of Gwynedd and Anglesey with water supplied from Llyn Cwellyn were told to boil their drinking water for two months after the outbreak.

The bug causes diarrhoea and vomiting for about two weeks.

The report said the outbreak was linked to the mains water supply from Llyn Cwellyn at Rhyd-ddu, and it was likely one or more people in the area had cryptosporidiosis before the main outbreak.

There was no failure of equipment and this outbreak could not have been anticipated Welsh Water

"Although they would have been ill with diarrhoea, they would probably not have known that this was due to cryptosporidium," it said.

The agencies who investigated included the National Public Health Service for Wales, Environment Agency Wales, and local health boards and councils in Anglesey and Gwynedd.

The report said after the bug entered Llyn Cwellyn "there were no effective barriers to prevent it then reaching the mains water supply."

Llyn Cwellyn's water treatment was in accordance with regulatory requirements. But Welsh Water did not need measures to kill cryptosporidium because regulators believed sewage would be sufficiently diluted in the lake to remove any risk.

About 70,000 Anglesey and Gwynedd households had to boil water

The report concluded that such an outbreak should not occur again with the "proper functioning of the ultra-violet treatment".

Welsh Water said it accepted that the outbreak was linked to the mains water supply from Llyn Cwellyn.

"Our investigations at the time confirmed Cwellyn water treatment works to be operating normally, and all testing for water quality showed no breach of standards," it said in a statement.

"There was no failure of equipment and this outbreak could not have been anticipated.

"We greatly sympathise with those people who were ill as a consequence of the outbreak and, while we do not consider that there was any failure or neglect on the part of the company, we will be considering and settling appropriate claims for compensation from those people who were diagnosed as having cryptosporidiosis.

"We will be writing to individual claimants or their solicitors in the next few days."

It said protecting public health was Dwr Cymru's highest priority.

Professor Jeni Colbourne, the chief inspector of drinking water, is to decide on any prosecutions. She said she would meet Wales' chief medical officer in January "to jointly consider lessons learnt."

Chief Medical Officer Dr Tony Jewell said he would also take the issues highlighted in the report to his counterparts across the UK.