Paris Olympics postpone triathlon because of pollution in river Seine

The Paris Olympic men’s individual triathlon was postponed on Tuesday after organizers found dangerous levels of bacteria in the River Seine, which was due to host the event’s swimming leg.

The decision, made by World Triathlon, came just hours before athletes were due to squeeze into their wetsuits and dive in for a 1,500-meter swim. Instead, the race will move to Wednesday, July 31, right after the women’s race.

The water had been deemed safe as recently as last week. But heavy rain in the French capital on Friday and Saturday strained Paris’s antiquated sewage system and led to wastewater going straight into the Seine, despite the city’s $1.5 billion efforts to make the river swimmable.

And with that, one of the Paris Olympics’ signature moments began to spiral the drain.

“The tests carried out in the Seine today revealed water quality levels that did not provide sufficient guarantees to allow the event to be held,” organizers said.

Now, the men’s triathletes enter a holding pattern, unsure if they will be braving the waters of the Seine later in the week. That said, adapting to variable conditions is a major part of triathlon. Athletes are used to changing their plans on the fly, according to USA Triathlon high performance general manager Scott Schnitzspahn.

Still, sending swimmers into the Seine represented a larger gamble than usual. The plan had been a marquee piece of the Parisian bid to host the Olympics. But as the Games approached, it became clear that this would be a game of fine margins.

The city unveiled the keystone of its clean-river strategy this spring—a massive underground reservoir that would store wastewater during spells of heavy rain to prevent it being dumped into the river. Yet even that was just a tool for buying time. Conditions could change from day to day and were heavily dependent on the weather.

When Paris mayor Anne Hidalgo made good on her promise to go for a dip in the Seine earlier this month, the levels of E. coli and other bacteria were perfectly safe, the city said. Then over the weekend, things began to deteriorate. The first sign that the triathlon might be in jeopardy came on Sunday when officials canceled a practice session for the athletes in the Seine. They canceled another on Monday. And by Tuesday things still hadn’t improved enough.

Two other triathlon races are planned for later in the Olympics. The women’s race is scheduled for July 31 and the mixed relay is scheduled for Aug. 5.

The Seine is also due to be used for the marathon swimming events on Aug. 8 and 9. Plan B for those races is simpler, as the athletes don’t require road closures to contest two-thirds of their race. Organizers have said that if conditions aren’t favorable, the 6.2-mile swim races will be moved to Vaires-sur-Marne nautical stadium, the venue hosting the rowing and canoe competitions.

Write to Joshua Robinson at Joshua.Robinson@wsj.com and Laine Higgins at laine.higgins@wsj.com