to clean the Seine and approach the Olympics “with serenity”, Tony Estanguet inaugurates the Austerlitz basin – Libération

Supposed to limit pollution of the Seine in the event of a storm, the Austerlitz rainwater and wastewater retention basin was inaugurated this Thursday, May 2. The opportunity for all those involved in the Olympics to reiterate their confidence in the system before the triathlon and freestyle swimming in the river.

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The lightning that streaked the Parisian sky on the evening of May 1 and the deluges of water that followed could have constituted a perfect crash test. But the storm broke too soon. Too bad because a weather episode “like the one that hit the capital last night could have been absorbed in its entirety by the basin”, trumpets Tony Estanguet. Alongside the president of the Olympic Organizing Committee, the mayor of Paris, the Minister of Sports, the prefect of Ile-de-France and the mayor of the 13th arrondissement inaugurated the “storm basin” this Thursday, May 2. » d’Austerlitz, the centerpiece of the system intended to make the Seine suitable for swimming from July for the Olympic triathlon and freestyle swimming competitions. At their feet, a circular slab 50 meters in diameter replaced the old Marie-Curie square in front of the entrance to the Pitié Salpêtrière hospital. Below, a raw concrete cathedral which will be able to accommodate up to 50,000 m³ of water – the equivalent of 20 Olympic swimming pools – in the event of severe weather.

Built in forty-two months for a final budget of around 100 million euros, this infrastructure bears on its immense 35-meter pillars the responsibility for a somewhat crazy promise: “to carry out the 2024 aquatic events at the foot of the Eiffel Tower and make the Seine swimmable by 2025,” recalls Anne Hidalgo, the mayor of Paris. The Austerlitz basin will act as a safety reservoir in the event of severe weather which, until then, saturates the combined Parisian sewer network before flowing untreated into the Seine with its bacteria, harmful to the health of swimmers.

A concrete cathedral

Captured by an interceptor tunnel, this wastewater will now be redirected and stored in this immense tank before being gradually redistributed to the wastewater treatment plants in the Paris region via the Paris sewers. On average, the basin should make it possible to reduce the number of untreated wastewater discharges into the Seine from twelve to two each year. This concrete cathedral, which will be put into service “between mid and end of May” after final tests, remains a “fundamental crossing point to approach this summer’s competitions with serenity”, insists Estanguet in the face of the concerns expressed by certain competitors on the waters of the Seine.

According to the environmental NGO Surfrider Foundation, the water quality between September 2023 and last March was “above or even very well above” the thresholds recommended for swimming. But, between the Austerlitz basin and the other infrastructures built or renovated to purify the water of the Seine, the boss of Paris 2024 repeats without fear that he has made “an appointment this summer, or even before, to taste the water”.

Tribute to a deceased site manager

More than the concept of such a water retention basin, the urban insertion of such a massive structure was a challenge of “engineering and technicality in civil engineering”, supports Samuel Colin-Canivez, responsible for the large works on the Parisian sanitation network. Because the structure had to be built at a depth of 30 meters between a 17th century hospital, a railway station, an RER and an elevated metro line.

“I am very proud of all the companions and workers who worked hard to complete this project on time,” says the engineer who mentions the name of Amara Dioumassy. This 51-year-old site manager lost his life on the site in June 2023, hit by a reversing truck. Anne Hidalgo held a minute of silence in her honor before the start of the ceremony and the name of Amara Dioumassy, ​​who was buried in Mali, was inscribed on the inaugural plaque.

If the emergency is at the Olympics, each speaker drifts towards the “legacy” that this pool will represent for Parisians, as part of a “bathing plan” – 1.4 billion euros of investment – ​​which must allow everyone in the world to splash around in the Seine from 2025. A “childhood dream” for the mayor of Paris, who confirmed that she would take a dip in the river at the end of spring. Thanks to a system of flags to authorize or not bathing depending on the quality of the water, Samuel Colin-Canivez would like the capital to function like a coastal city. In the event of severe weather, diving will be prohibited. “Somewhere, it’s always nature that governs us,” he says with a smile. Paris Plage will not become Paris Piscine.