In Rouen, 90,000 people have to cope with polluted water.
Faced with the contamination of its main drinking water source, the city of Rouen has been unable to find an alternative source after ten years of research.
A dead end. That, in a nutshell, is the conclusion of a research programme launched in 2015 by the Rouen-Normandie Urban Community (MRN) to find a new source of drinking water, as revealed by Reporterre. In Saint-Étienne-du-Rouvray, the La Chapelle catchment, the town’s main reservoir located in an area with a strong industrial past, is subject to multiple contamination.
In order to stop using this polluted groundwater, which supplies the taps of 90,000 people living in the southern suburbs of the Seine-Maritime prefecture, studies had to be carried out to find a source capable of producing 50,000 m3 of water per day.
The study, which cost 559,300 euros, was financed by the Agence de l’eau, the Bureau de recherches géologiques et minières (BRGM) and the local authority. The latter contributed 282,840 euros to finance the field tests.
“None of the sectors studied is sufficiently protected against pollution.”
After ten years of research, the diagnosis is clear: none of the sectors considered is sufficiently protected from pollution to be a viable alternative.
The fault lies in a past marked by “irrational exploitation of resources” and “pollution which, whatever we do, invades the aquifers near urban and industrial areas”, warned a BRGM geologist in a 1967 report unearthed by Reporterre.
The stigma of the industrial past
Because of the proximity of factories and former landfills, the water taken from La Chapelle has been degraded. Contaminated at the start of operations in 1960, the catchment area was first affected by toxic chlorine pollution in the late 1970s and then by ammonium pollution in 2011.
However, thanks to the extensive treatment provided by the water treatment plant, the water can still be distributed in accordance with the regulations. At least until 2022. At that time, pesticide residues and PFAS, also known as ‘persistent pollutants’, were found in the tap water at levels above the quality limit set by the regulations. Since then, measures have been taken to bring the situation back into line.
The Rouen conurbation also faces a global, invisible threat, which BRGM experts described in detail in 2015: “The heavy industrialisation of the region in the past has left behind a multitude of contaminated sectors whose pollutants […] are slowly migrating towards the water tables, with the risk of rendering certain parts of them unfit for human consumption. This risk is exacerbated by the effects of climate change.”
The Rouen agglomeration is no exception. In 2022, France will have 32,900 active drinking water catchments. Between 1980 and 2024, 14,300 were closed, including 4,600 due to pollution problems, according to a roadmap for the protection of drinking water catchments by the Ministry of Ecological Transition. The document, published on 28 March, points out that “pollution of water resources is an insidious threat with long-term effects on health and the environment”.
A promising lead ruled out
In 2015, preliminary research into a new source of drinking water led BRGM to identify 17 potential sectors – including 4 in the Seine Valley. However, 11 were automatically rejected. The reasons for this were “the presence of potential sources of pollution”, the geological characteristics of certain sites that could facilitate the infiltration of contaminated water into the aquifers, and the risk of competition with industrial and agricultural abstractions, according to an official document issued by the MRN in 2023.
Another constraint is that the deposit must be located within a 30km radius of the La Chapelle catchment, where there is a treatment plant that the local authority wants to keep. “The network was built around this site,” explains Arnaud Delahaye, a manager in the MRN’s environmental department.
The green islands in the loop of the Seine upstream of Rouen, just 5 km from this plant, were initially considered ‘particularly interesting’ by BRGM engineers. But a number of problems arose. “On the banks of the Seine, there has been a lot of quarry backfilling. The sediments are potentially contaminated with various substances that can be released in unpredictable ways”, explains Arnaud Delahaye. The sector is also exposed to discharges from the Saint-Aubin-lès-Elbeuf chemical platform downstream. This promising option was abandoned in 2019.
Last hopes dashed by pollution
Hopes then turned to a vast area of five potential sites outside the metropolis, in the neighbouring department of Eure. The landscape here is characterised by market gardens, a lake, a leisure centre, etc. But it is also characterised by a variety of industrial activities, from paper production to metallurgy, waste processing and chemicals.
When the results of the drilling tests came in, it was a cold shower, according to an exclusive document obtained by Reporterre. The document, which was presented to the research programme’s steering committee on 6 March, shows that the groundwater at 4 of the 5 sites contains levels of pollutants – nitrates, pesticides, metals or PFAS – that exceed the quality standard for drinking water. Even the last site, in the commune of Poses, which has been used for organic farming for 30 years, shows ‘traces of contamination’, says Arnaud Delahaye.
“There is a huge challenge in terms of decontamination techniques.”
Jean-Pierre Breugnot, vice-president of the Rouen Urban Community in charge of water and wastewater treatment, is resigned to the research: “We wanted to find a new source of drinking water for the conurbation. We found a source that met our expectations, around 50,000 m3 per day. Unfortunately, the quality of the water was not much better than that from the La Chapelle catchment”.
The cost of treating this alternative source, which was also polluted, plus the cost of transporting the water to the drinking water treatment plant, would have pushed the bill through the roof. Beyond the environmental and health considerations, this operation was not considered economically viable.
Increasingly expensive treatment
As a result, the city council had to resort to continuing to operate the La Chapelle catchment, but with additional treatment. According to the local authority, measures to reduce PFAS levels alone represent an additional annual cost of around €200,000.
According to Alain Rouziès, environmental officer for the Rouen branch of the UFC-Que Choisir, “there is a very real problem with the pollution control techniques used in the La Chapelle catchment. During our sampling campaign, we found eleven different PFAS in the tap water from this source.” He says he “protested” against the project to transport water from the Eure: “We thought it was excessive to spend 30 million euros to build an aqueduct. The priority is to protect the existing water catchments.”
The installation of a hydraulic barrier (a device that changes the direction of groundwater flow) by the city council, scheduled for the end of 2025, should prevent further pollution of the La Chapelle catchment area from the industrial estate.
“Our guiding principle is to ensure that the water distributed to our taps meets quality standards,” explains Jean-Pierre Breugnot.
In 2022, BRGM’s experts recommended that the Rouen conurbation develop ‘protection zones’ to ‘safeguard future water supplies for future generations’. Their studies should feed into discussions on a future water safety plan to protect users.
