The reservoir – which represents 35 per cent of Jersey’s water storage capacity – has not been used for five months following the discovery in February of pesticide oxadixyl in streams feeding the reservoir.
However, the utility has now applied for a temporary dispensation under the Water (Jersey) Law 1972 to exceed the strict regulatory limit on oxadixyl in order to make use of water from Val de la Mare during the summer months.
The company says that it needs to allow its other main reservoirs, Queen’s Valley and Grands Vaux – which have been in use since February – time to refill, and insists that the water it supplies from Val de la Mare will still be safe to drink.
Jersey Water chief executive Helier Smith said: “The need for a dispensation in this instance is principally a regulatory compliance matter under the law rather than a health-based issue. The water that we supply will remain safe to drink. The presence of oxadixyl in Val de La Mare Reservoir and elsewhere is historic and has arisen due to factors outside of the company’s control.
“We are working hard to find a way to remove oxadixyl through treatment but in the meantime will work to comply with the lower limit where it is practical for us to do so.”
The regulatory limit for oxadixyl in treated water is 0.1 micrograms per litre (ug/l) which is equivalent to one part in 10 billion. The company has applied to increase that limit on a precautionary basis to 0.3ug/l, which is 100 times lower than the health base limit of 30ug/l, for a period of three years whilst it researches and implements a long term treatment solution to the oxadixyl problem.
The application for dispensation is currently being considered by the environment minister in consultation with the health and social services minister.
Jersey Water will continue to manage water quality by blending and treatment but the use of water from Val de la Mare increases the risk that on occasion, levels of oxadixyl in the treated water supply may exceed the regulatory limit.
“Val de la Mare Reservoir is a significant source of water for the island which we need to bring into service in order to manage our water resources,” said Smith. “Given that oxadixyl was only discovered in February, there is uncertainty over the likely concentrations of oxadixyl over the remainder of the year.
“Current indications are that concentrations in Val de La Mare are likely to increase over the summer. In these circumstances, normal blending options may be insufficient to enable us to comply with the 0.1ug/l limit all of the time.
“We have therefore taken the precautionary steps of applying for a dispensation to cover this eventuality. We will work with the Minister for Environment as he continues to discuss pesticide use with the farming community, in order to protect the Island’s water sources from further contamination. Our laboratories have stepped up their testing programme to monitor water sources supplying our reservoirs and will continue to report any environmental breaches.”