A documentary lifts the veil on the Austerlitz basin, a “cathedral” used to make the Seine swimmable

Preparing the world’s biggest sporting event is a real challenge for the host country. Directed by Jules and Gédéon Naudet, the documentary At the heart of the Gamesbroadcast on France 2 Monday July 22 at 9:10 p.m., looks back at this epic project.

This four-part series, produced in collaboration with the IOC and Paris 2024, chronicles the arrival of the Olympic flame in Marseille through to the final preparations for an opening ceremony that is unprecedented in the history of the Games. It is also an opportunity to discover the transformation of historic sites, such as the Place de la Concorde and the Château de Versailles, into modern Olympic venues.

For the first time in the history of the Summer Olympics, the opening ceremony will take place not in a stadium, but on a river. Around 326,000 spectators are expected, according to the Interior Ministry. The triathlon and swimming marathon will also take place on the Seine, making the heart of Paris the ideal setting for this competition.

The most ambitious challenge that the Olympic Committee has had to take on since awarding the Games to Paris in 2017 was to make the waters of the Seine swimmable.When we started our application, the president of the International Triathlon Federation told us that she would dream of having a triathlon event in the Seine, that it would be fantastic.”, confides the mayor of Paris, Anne Hidalgo, in the documentary.

In 2021, a colossal construction site was set up near the Gare d’Austerlitz to build a huge wastewater storage basin. This huge cathedral-shaped well, 50 metres in diameter and 30 metres deep, can hold 50,000 m3 of wastewater, the equivalent of 20 Olympic swimming pools.When there is a very, very big storm, the sewers overflow and there is a mixture of dirty water and rainwater (…). The Austerlitz basin is designed to retain the water so that there are no discharges from the sewers into the Seine.”, specifies the mayor of Paris in the film during the inauguration of the basin which cost 80 million euros.

“The sewers (…) will overflow here first,” Samuel Colin-Canivez, responsible for the work on the Parisian sanitation network, explains in the documentary.Then when we reach the maximum capacity of the structure, we close the doors to restore the path to the Seine. But 50,000 m3 of pollution will have been removed.” However, these measures to make the waters of the Seine suitable for swimming have long been considered insufficient, as we explained in an investigation published in January.

Despite the presence of devices to monitor the level of bacteria, doubts about the possibility of organizing Olympic events in the Seine persisted until the end. A study by the specialized NGO Surfrider Foundation published on July 16 finally confirmed that swimming in the river was no longer dangerous. To prove it, the mayor of Paris and the resigning Minister of Sports took part in the diving exercise under the eye of the cameras.

The cost of this clean-up is also causing a reaction. The State and the Paris region communities have invested a total of 1.4 billion euros over the past decade to clean up the Paris river and the waters of the Marne, with the Olympic Games having played a role. “accelerator”. However, this swimming plan, which also has an ecological aim, will not be limited to this event. It should benefit all Parisians from 2025 with pools located in the center of Paris, at the Bras Marie (Parc des rives de Seine, right bank), at Grenelle (15th) and at Bercy (12th).

The documentary At the heart of the Games, directed by Jules and Gédéon Naudet, is broadcast on France 2 Monday July 22 at 9:10 p.m. and on the france.tv platform.