How Paris Cleaned Up the Seine Ahead of 2024 Olympics, and Where to Swim

Eight years after Paris city officials resolved to clean up the Seine once and for all, the city has declared victory over the E. coli, enterococci and other assorted micro-organisms that for centuries struck down the unfortunate bather. To show off the river’s newly pristine waters, the Seine was chosen to host the Olympic open-swimming competitions — marking the first time that an urban river has been used for swimming events at the Games since they were revived in 1896.

It’s a risky move: The Seine has long had a dirty reputation, and swimming in the river has been banned — officially at least — since 1923. A billion people were expected to watch the games, and it would only take one vomiting Olympian to tarnish the river’s new image. Games organizers showed they were taking no chances when they postponed the men’s triathlon on July 30, saying the water wasn’t clean enough.

Unfortunately for Paris, Olympic events in the river may have resumed too soon. On Aug. 4, Belgian triathlete Claire Michel was admitted to hospital, with an infection reported by the Belgian media as E.Coli, prompting the withdrawal of the entire Belgian triathlon team. Swiss triathlete Adrien Biffod also withdrew from competition after reporting a gastrointestinal infection over the weekend, though the Swiss Olympic team said in a statement that it was “impossible to say” if this was linked to the Seine’s water quality.

The Olympics, however, are supposed to be just the beginning. By next summer, it should also be possible for the general public to take the plunge at selected spots.

The sight of people splashing around in clean waters with the Eiffel Tower or the spire of Notre Dame cathedral looming over them would mark a victory for Socialist Mayor Anne Hidalgo and her combative pro-environment agenda. But the costs of the cleanup are high, and it’s yet to be seen whether the modifications will make the Seine swimmable on a durable basis. Critics are already asking whether it was really worth all the expense.

The Seine was often malodorous, especially during periods of heavy rain, as dirty water was discharged into the river when the system was overwhelmed. To stop this happening, Paris has introduced:

The river is still vulnerable to occasional sewage runoff if heavy rains overwhelm the new water treatment system. That’s what appears to have happened during the first week of the Olympics, with part of the opening ceremony taking place under a downpour and some competitions delayed due to the rain.

€1.4 billion ($1.5 billion). Cleaning up a water system running through Europe’s most populous metropolitan area has proved very expensive, with the southern super-sewer alone involving an outlay of €300 million.

Not at all. Paris has been seriously discussing the idea of making the Seine swimmable as far back as 1988, when then-Mayor Jacques Chirac first promised to clean up the river. That plan sat on the shelf for decades. A full Seine cleanup was proposed as part of Paris’s bid to hold the Olympics, as a way for the city’s leaders to show that holding the games would “ensure that our candidacy is useful to Parisians.” The work itself began in 2016. In 2017, Paris launched open-water bathing spots along the city’s newly cleaned eastern chain of canals, which flow into the Seine.

In the meantime, Paris has been pushing hard to reclaim the riverside, known as “les quais,” as a kind of open-air living room for the city. Since 2007, it has laid out sand and deckchairs each summer to create an impromptu “beach” at selected locations. In 2016, it transformed the river’s lower quayside — a major traffic route along the Right Bank since the 1960s — into a promenade free of motor vehicles. Making it possible for sunbathers to step off the promenade for a cooling dip was arguably a logical next step.

Not entirely. Paris already has past experience of how hard it can be to keep open water clean: The new canal swimming spots have had to close temporarily on several occasions due to bacteria in the water, although they have mostly stayed open. For the river’s main body, pre-Olympic water quality was a little hit-and-miss because of successive bouts of heavy rain, and the new infrastructure wasn’t enough to prevent undesirable bacteria being detected at the beginning of July. The river was given the all-clear just before the Games began, but heavy rain around the night of the opening ceremony may have seen more pollutants flushed into the water despite all the new infrastructure, possibly leading the the current health issues reported by triathletes.

Swimmers could be exposed to bacteria that cause nausea and diarrhea — with the most serious symptoms potentially requiring a visit to the hospital. If the water is deemed to be a risk, some events will move to the suburban aquatic stadium at Vaires-sur-Marne, which is also hosting the Olympic rowing and canoeing.

If the goal was simply to get a new river bathing site, then probably not. Swimming along one of the world’s most beautiful urban riverfronts will be a delightful experience, but one whose cost would seem astronomical if that were the city’s sole objective. Viewed another way, the project has been a canny maneuver – using the attention that comes with the Olympics to power a major upgrade of some dull yet vital infrastructure that might otherwise have been sidelined in favor of other spending priorities.

The cleaning of the Seine also helps to burnish Paris’s brand as a new capital of sustainability – a place where cars and tarmac are ceding space to bikes, pedestrians and trees – right when all eyes are on it. It may not be the only place in Europe to offer city-center swimming: Zurich, Copenhagen, Stockholm and Oslo already have some facilities. But Paris is so far the only place to have tried it on a relatively narrow river (rather than a harbor or a lake) flowing through a heavily-populated metropolis.

The highest-profile event was the opening ceremony on July 26, staged for the first time on boats and barges floating downstream through the city. After the recent triathlon events, the Seine is scheduled to host the marathon swimming on Aug. 8 and 9. The events start from the Alexander III bridge, which provides a crossing point between the Hôtel des Invalides and the gardens at the base of the Champs Elysées.

The city is preparing three bathing spots for 2025 that will be marked off by buoys and supervised by lifeguards. They will be along the north side of the Île Saint-Louis (near metro stations Pont Marie and Sully-Morland), just south of the Eiffel Tower along the river’s Grenelle arm (metro Bir-Hakeim) and between the Bercy and Tolbiac bridges in the city’s southeast (metro Bercy or Quai de la Gare).