This case study relates to a small supply serving three domestic premises and a milking parlour. Some, but not all, of the properties were fitted with point of use treatment (ultraviolet (UV)). A planned sample collected by the local authority contained E.coli and the local authority advised all users to boil water before use or to drink bottled water while an investigation was carried out.
The borehole source, located in pastureland grazed by cattle and sheep, was situated in a depression in the land that is heavily waterlogged resulting in ponding. However, the owner explained that when there is little rain in the summer the supply becomes insufficient and at these times there is no ponding around the borehole. From this evidence it was concluded that surface water seeps directly into the borehole.
The local authority concluded that the supply posed a potential danger to human health and served a Regulation 18 Notice restricting the supply. The Notice required water to all the properties, including the dairy, to be UV treated. The effectiveness of the arrangements was to be evaluated and enhanced by a system of regular checks and maintenance and the keeping of records. There was no appeal to the Notice but following risk assessment the owner decided that drilling a new borehole and abandoning the existing poorly sited one would be a more cost effective long-term solution. The local authority was not informed of this decision until after the new borehole had been completed. On inspection the construction of the new borehole showed basic faults allowing ingress, for example, there was no cover, the casing was partially open and the top of the chamber was less than 150mm above ground level. As a result of these deficiencies the owner of the supply had to pay additional costs for remedial works.
This case study illustrates the importance of providing owners with advice when identifying risks relating to borehole siting and construction. Owners should be recommended to consult the Environment Agency or the British Geological Survey and attention is drawn to the Guide to Good Practice for borehole location, construction and headworks published by SEPA at http://www.groundwateruk.org/downloads/SEPA_borehole_construction.pdf.