Following the fire of 26 September 2019, the Hauts-de-France Regional Health Agency (ARS) introduced reinforced monitoring of drinking water quality. Fifty groundwater abstraction points and five surface-water intake points used for producing drinking water were targeted in the areas concerned by prefectoral orders on precautionary measures for agricultural products, which cover 119 municipalities.
Since these initial results, the Hauts-de-France ARS has prepared an update to its monitoring programme with new conditions regarding targeting, frequency and type of sampling, mainly according to geographical parameters specific to the region: distance from the accident site and geological vulnerability of the sector, which is generally lower than in Normandy.
The ANSES group of experts assessed this ARS proposal taking into account the available monitoring results, an analysis of the hydrogeological context of the Hauts-de-France region, and the trends observed for Seine-Maritime, as this département acts as a sentinel for the region.
Several adjustments to the analysis plans were formulated in terms of substances to be analysed, frequency and duration. In particular, the experts recommended maintaining the analysis of metals and polycyclic aromatic hydrocarbons (PAHs) and analysing volatile organic compounds (VOCs), whereas they considered that measuring polychlorinated biphenyls (PCBs), dioxins, furans and perfluorinated compounds no longer seemed necessary. Concerning sampling frequencies, graduated requirements were formulated according to the vulnerability of the abstraction points.
The experts proposed applying this monitoring plan until September 2020, to cover one hydrological year and therefore monitor a complete annual cycle of groundwater recharge. This monitoring and analysis programme may be modulated and adapted over time according to the results obtained in Normandy – as the sentinel region – and Hauts-de-France, as well as the results of the environmental monitoring of water bodies carried out by the water agencies.
More generally, ANSES recommended including some non-targeted analyses of contaminants in the various media (water, air, soil) besides drinking water in environmental and health monitoring, to be used as a point of comparison in a post-accident context.