Paris closes Seine to swimmers 1 day after ending ban

Just one day after opening the Seine River to swimming for the first time in more than a century, French officials shut down the river due to concerns about pollution following heavy rainfall.

Swimming in the Seine has largely been illegal since 1923 due to pollution and other safety risks. The river was opened for public swimming Saturday in three designated areas.

The flip-flop follows a nearly 1.4 billion-euro project to clean up the river in the lead-up to last year’s Olympics. The river hosted several open-water events, including the swimming leg of the triathlon. It was also the site of the games’ opening ceremonies, with boats filled with athletes sailing through the city.

Paris Mayor Anne Hidalgo even took a swim prior to the Olympics to demonstrate the water’s cleanliness to a skeptical public.

Officials had first aimed in the 1990s to clean up the river. The plan that eventually got it done was proposed in 2015 and involved upgrading Paris’s 19th-century sewer system so that households were no longer dumping wastewater directly into the river. The city also built a reservoir to conserve rainwater and prevent waste from flowing into the river.

Still, the system is vulnerable on rainy days, a French official told Le Monde. That’s what happened Sunday, with heavy rainfall raising concerns about pollution. Heavy rain also caused a spike in bacteria during the Olympics, causing the triathlon to be postponed a day.

The river is tested daily for E. coli and other harmful bacteria.