$1.5 billion effort

Paris' $1.5 billion effort to clean up Seine for Olympics swim events at risk

Rain on Tuesday had Paris holding its collective breath that sewage doesn't seep back into the Seine

By Grant Marek

Less than a tenth of an inch of rain fell in Paris Tuesday morning, which normally wouldn't be cause for alarm.

But after the city spent a reported $1.5 billion to clean up the River Seine — which regularly has sewage flow into it during heavy rains thanks to Paris' archaic sewer system — it was cause for some alarm ahead of Friday's kickoff to the 2024 Olympics. The competition is supposed to host multiple swim events in the river, as well as a country-by-country parade of boats on Friday for the Games' opening ceremony. In addition to Tuesday morning's rain, there's also plenty more rain in the forecast for Friday and Saturday, which could very well be problematic.

The Seine has been closed to swimmers for 100 years due to dangerous levels of bacteria caused by the a number of pollutants — including sewage, industrial and agricultural pollution, as noted by Arthur Germain who famously swam the entire length of the Seine in 2021.

"In deepest rural Burgundy — days before he got anywhere near Paris — he measured levels of faecal matter well above EU limits for swimming," read a wire story published July 11 by the Agence France-Presse. "Further north he swam past farmers spraying pesticides by the riverbank." Gaelle Deletang, one of the few people who intentionally swims in the river as a member of Paris' aquatic civil defense team, told the AFP she swam in the Seine last winter and got “diarrhea and a rash.” Several other swimmers "had a bug for three weeks... and everyone had stomach upsets," she said.

Over the last three months, multiple media outlets have independently measured the levels of bacteria and the Seine and found the levels to be 10 to 20 times above the maximum safety standard for the Games.

But an ambitious plan from Paris Mayor Anne Hidalgo — and also a lot of money — has the river nonetheless days away from potentially hosting both one leg of the triathalon and the marathon swimming event. All that money bought the city newly modernized sewage plants upstream, incentives for moored boats to use the city's sewage networks for their wastewater, as well as a vast underground tank. That tank — their hail Mary to combat this week's rain — connects directly to the wastewater lines and can hold 13 million gallons of wastewater before it heads off to a treatment plant, according to the Wall Street Journal. That's enough to fill 20 Olympic-sized swimming pools and maybe Paris' only shot at keeping water bacteria levels in the green.

The tank went online in the spring, and Paris officials have repeatedly said it's already doing its job without much data to support it, instead pointing to press stunt last week where Hidalgo swam in the Seine — in a wetsuit, with goggles on — to show just how safe it was.

She was originally supposed to swim in the river weeks earlier, but the wet start to the year caused the city's sewerage system to overflow into the river repeatedly, forcing the mayor to delay her dip. Paris also cancelled a dress rehearsal of the opening ceremony on July 2 — three weeks before Friday's event — due to "dangerous concentrations of faecal bacteria in the water."

“It was magnificent,” Hidalgo said after her swim. “The water is very, very good, a little bit cool but not that much.”