“The Cojo (organizing committee) has always said that there was no plan B as to the location of these events,” said Marc Guillaume, the prefect of the Île-de-France region, in front of the press.

At the beginning of August 2023, the dress rehearsal for the open water swimming event turned into a nightmare for the organizers, forced to cancel it due to the river’s water quality thresholds being clearly exceeded, after a very heavy rainy episode. intensity.

In a recent interview with AFP, the reigning Olympic champion in the specialty, the Brazilian Ana Marcela Cunha, did not hide her “concern”.

“But (the organizers) insist on wanting the events to take place there,” she lamented, demanding “a plan B in case it is not possible to swim” in the Seine. “We are working to ensure that the tests are held in the Seine,” replied Marc Guillaume.

“If the water samples which will be taken in the Seine show that we have difficulties, we must postpone the tests (…) with the contingency days” planned, i.e. “one or two days”, he said. -it develops.

Scheduled between the Alexandre-III bridge and the Eiffel Tower, the triathlon events (July 30 and 31, August 5) and open water swimming, now called marathon swimming (August 8 and 9), remain threatened by heavy precipitation which would degrade the water of the Seine, via the discharge of wastewater mixed with rainwater into its bed.

For a decade, the State and local authorities in Ile-de-France have invested 1.4 billion euros in work intended to make the river swimmable for the general public, on defined and secure sites, the day after the Olympics.

A storage basin capable of accommodating nearly 50,000 m3, the equivalent of 20 Olympic swimming pools, is nearing completion near Austerlitz station, among other works intended to limit and/or clean water discharges. worn.

“Statistically, there are still a few rains during the year for which these storage capacities would not be enough,” acknowledged Marc Guillaume, for whom “the objective of decontaminating 75% will be met.”