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 would strike down the unfortunate bather.

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From July 30, the river’s newly pristine waters will host the Olympic open-swimming competitions — that is, unless rainstorms overwhelm the new sewage treatment system and force the events indoors. No host has staged Olympic swimming in an urban river since the Games were revived in 1896, and the stakes are high. The Seine has long had a dirty reputation, and swimming in the river has been banned — officially at least — since 1923. A billion people are expected to watch the games, and it will only take one vomiting triathlete to tarnish the river’s new image.

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 clean-up are high, it’s yet to be seen whether the modifications will make the Seine swimmable on a durable basis, and critics are already asking whether it was really worth all the expense.

What’s been done to clean up the Seine?

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:

• A cathedral-sized run-off basin beneath the Gare D’Austerlitz rail station that’s capable of catching as much as 50,000 cubic meters of storm overflow water, which can be pumped back into the sewers once water levels subside.
• An overhaul of sewage processing across the region to make sure water arrives in Paris in a cleaner state in the first place. Chief among these is an 8.8 kilometer (5.7 mile) super-sewer built south of the city.
• Financial incentives and a publicity campaign to encourage at least 10,000 rural households and houseboat owners upstream of Paris to stop discharging toilet waste directly into the river, diverting it instead into the sewer system.

How much has it all cost?

€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.

Is a Seine clean-up a new idea?

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.

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Has the clean-up been effective?

It has – but only just. 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 has been a little hit-and-miss because of a recent bout of heavy rain, and the new infrastructure wasn’t enough to prevent undesirable bacteria being detected as recently as the beginning of July. Since then, drier conditions have improved things and the water was expected to stay clean for the games.

What happens if things go wrong?

Very heavy rain might still cause some sewage to flow back into the river, meaning swimmers could be exposed to bacteria that cause nausea and diarrhea — with the most serious symptoms potentially requiring a visit to hospital. Regular water testing should alert swimmers ahead of time, however. If the water isn’t clean enough, the swimming marathon will move to the suburban aquatic stadium at Vaires-sur-Marne, which is already due to host the Olympic rowing and canoeing. The triathlon would be postponed by a few days in the hope that conditions improve.

Was the clean-up worth it?

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.

Which Olympic events will take place in the Seine?

The highest-profile event that the river will host is the opening ceremony on July 26, staged for the first time on boats and barges floating downstream through the city. The Seine is scheduled to host the swimming leg of the triathlon on July 30, July 31 and Aug. 5, and the marathon swimming on Aug. 8 and 9. Both events will 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.

Where will you be able to swim in the Seine?

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).

Source:

Feargus O’Sullivan at Bloomberg

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