Private Water Supplies - Case Study 2010/04

Arsenic in the supply to a holiday cottage – technical support and advice

This small supply serves 3 holiday cottages and one domestic dwelling was sampled under the previous 1991 regulations because of its use for commercial purposes. The source is a borehole and the well maintained supply is disinfected by means of a common ultraviolet (UV) system. Under the previous regulations samples were not analysed for arsenic but based on a knowledge of local geological hazards relating to deep historical mining, the local authority included arsenic in its testing under the new regulations and obtained a result of 63µg/l. The health-based standard for arsenic is 10µg/l.

The treatment in place, although effective, only safeguarded users against microbiological risk. Advice from the Health Protection Agency confirmed the potential danger to human health which was controlled by a Regulation 18 Notice restricting the supply (owners to make all users aware and provide with bottled water to be provided for drinking, cooking and washing teeth) and seeking a suitable proposal to improve the supply to bring the level of arsenic below the standard. The Notice also made the owner aware that the permanent solution would need to comply with Regulation 5. Due to the absence of past experience of removing arsenic from private supplies, this case involved the local authority working with all the parties to enable the development of an appropriate solution. At the same time, the local authority also required a written procedure for maintenance and monitoring of the disinfection equipment by the owner. The owner has co-operated fully with the local authority and there has been no appeal to the Notice. This case illustrates the benefits of the risk based approach to the selection of monitoring parameters. It also demonstrates how owners have traditionally relied upon consultants and contractors, who may not act in the best interests of their clients (owners) because they are not themselves fully conversant with all types of hazards and may not necessarily know the historical land use of the area. This case demonstrates how local authorities can use the new provisions in the regulations to empower owners with the knowledge needed to commission sound advice. Contractors/consultants can be held to account by owners because the final solution together with suitable ongoing maintenance requirements and operational checks must be specified and independent advice obtained from the local authority. This case also demonstrates how local authorities need to access the technical expertise of the Inspectorate when dealing with situations that have not arisen previously.