Welsh Water yesterday pleaded guilty at Caernarfon Magistrate's Court to supplying water unfit for human consumption.
The incident involved the supply of drinking water containing the parasite Cryptosporidium hominis from the Cwellyn Water Treatment Works which resulted in 231 confirmed cases of illness in November 2005.
Chief Inspector of Drinking Water Professor Jeni Colbourne, who brought the charges under Section 70 of the Water Industry Act 1991 said, "This was a serious incident. Many consumers were affected at the time and for some, the consequences were severe.
"My inspectors will shortly be issuing their Incident Assessment Letter. This will record the conclusions and findings of our investigation. Dwr Cymru Welsh Water are required to respond to all recommendations for action to prevent a recurrence," she said.
Section 70 of the Water Industry Act 1991 makes it criminal offence for a water company to supply water which is unfit for human consumption.
The Company was fined a total of £60,000 from 4 contaminated specimen counts, and an additional £69,399.43 costs.
As a result, from 22nd December, the Surface Water Abstraction Directive will be repealed by the Directive 2000/60/EC, the “Water Framework Directive”, which should tighten regulations and prevent such accidents ocurring again.
This should include new requirements to protect and monitor waters used for the abstraction of drinking water, known as drinking water protected areas.
"I am pleased to report that wider lessons have been learnt from this incident. To reduce the chance of a repetition of the mistakes made by the water supplier, Dwr Cymru, the relevant regulations are being changed," said Colbourne.