This case study concerns a private water supply serving a small village, comprising dwellings, a shop, a public house and a primary school. From the spring collection chambers water is piped to a large covered storage tank where chorine is added before the water is distributed to the village.
When, in January 2012, the local authority carried out a risk assessment the supply was considered a potential danger to human health because the source was not protected, the infrastructure was in poor condition, disinfection with chlorine was ineffective and the management procedures inadequate. Overall, it was felt that the supply was particularly at risk from Cryptosporidium. The local authority put in place a Regulation 18 Notice based on the risk and provided the owner with a summary of the gaps in control measures together with the improvement works required to mitigate the risks.
The owner of the supply disputed that the supply was at risk from Cryptosporidium on the grounds that the source originated from a deep groundwater spring and previous samples taken throughout the year had given satisfactory results. In response, the local authority was able to show that they had gathered information from consumers as part of the risk assessment process showing that the water at their taps turned brown and contained sediment after heavy rainfall, which blocked the filters on the supply causing low flows. This evidence clearly pointed to surface water ingress with local land use conditions such that Cryptosporidium oocysts could be present.
The local authority took samples from the supply four times a year and, unsurprisingly, the majority of these historic samples had been microbiologically satisfactory. Rainfall initiated events are often short lived and not picked up by occasional regulatory sampling. However, one particular consumer had been sampling twice a month at his supply and also a nearby supply. An examination of the combined data over a period of four years provided further supportive evidence that the source was not stable and prone to regular contamination events with the highest risk manifesting in the autumn. Such a pattern is entirely consistent with the large body of knowledge that underpins the risk assessment process embedded in the Inspectorate’s tool.
This case study reinforces the dangers inherent in the old regulatory regime, which has encouraged owners of private supplies to develop undue faith on sample results, which in turn reinforces mythology about the purity of spring water. The case study also highlights an aspect of the regulations that local authorities could make more use of when faced with obdurate owners unable to accept the findings of a risk assessment. The regulations give local authorities the power to increase the frequency of monitoring or tailor it to periods of highest risk. Where an owner refuses to accept the outcome of a risk assessment and persists in challenging behaviour in the face of published evidence such as that contained in the Bouchier report1 then a regime of enhanced monitoring for faecal indicators and turbidity may prove educative and move the situation forward. Such operational monitoring can be set out in a Regulation 18 Notice and this would be desirable, if there are concerns about recovering the costs of enhanced monitoring. Doing so would also facilitate communicating the continuing unmitigated risk to all of the users of the supply, itself a step that can be persuasive.
1 Cryptosporidium in Water Supplies -Third Report of the Group of Experts to:Department of the Environment, Transport and the Regions & Department of Health Chairman – Professor Ian Bouchier November 1998.