Under Article 9 of the Drinking Water Directive ("the Directive"), Member States may, for a limited time, deviate from chemical quality standards specified in annex I. This process is called "a derogation". A derogation can be granted, provided it does not constitute a potential danger to human health and provided that the supply of water intended for human consumption in the area concerned cannot be maintained by any other reasonable means.
As a rule, two derogations are allowed by the Directive; each of them limited in time to a maximum of three years. The administrative and management specifications taken into account are:
(a) the grounds for the derogation;
(b) the parameter concerned, previous relevant monitoring results, and the maximum permissible value under the derogation;
(c) the geographical area, the quantity of water supplied each day, the population concerned and whether or not any relevant food production undertaking would be affected;
(d) an appropriate monitoring scheme, with an increased monitoring frequency where necessary;
(e) a summary of the plan for the necessary remedial action, including a timetable for the work and an estimate of the cost and provisions for reviewing;
(f) the required duration of the derogation.
First and second derogations are the responsibility of Member States. Where a Member State grants a first or second derogation concerning an individual supply of water exceeding 1000 m³ a day as an average or serving more than 5000 persons, it shall inform the Commission, providing the information specified above. Provisions of derogations are subject to the general right of scrutiny by the Commission on Member States' implementation of the Directive, and where appropriate the Commission may commence an infringement procedure.
The Directive foresees the possibility of a third derogation for maximum 3 additional years. For a third derogation the same administrative and management specifications apply as for the first or second derogations. In such a case, it is the Commission who decides whether or not to grant the derogation. In a Decision, the Commission will express an agreement (or refusal) with the request for derogation and indicate which measures must be taken in order to protect public health. The format agreed to be used when presenting second derogation notifications or third derogation requests is available here.
The concerned Member State is notified of the Decision, and the text can be consulted by Member States, by stakeholders and by the public on this site.