Less than two months before swimming competitions are set to take place in the Seine River during the Paris Olympics, test results published yesterday revealed elevated levels of E. coli, deeming the water unsafe. Persistent heavy rains in Paris during the first eight days of June caused contamination levels of E. coli and enterococci bacteria to exceed safe limits for athletes.

The report by monitoring group Eau de Paris came a day after a senior International Olympic Committee (IOC) executive expressed confidence that the races would proceed as planned in the historic downtown stretch of the Seine near the Eiffel Tower.

The Olympic events set to take place in the cleaned-up Seine begin with the men’s triathlon on July 30, followed by the women’s triathlon the next day, a mixed relay on August 5, and marathon swimming races on August 8 and 9. These events are part of a significant effort, marked by a $1.5 billion investment, to clean up the previously polluted waters of the Seine.

Despite the IOC’s assurance, the final decision on the safety of the water rests with the governing bodies of World Aquatics and World Triathlon. Concerns have persisted since test events last August were canceled due to unseasonal heavy rains.

European standards set the safe limit for E. coli at 900 colony-forming units per 100 milliliters, the same criteria used by the World Triathlon Federation. Tests from early June frequently showed E. coli levels above these thresholds, although enterococci levels mostly stayed within safe limits. An improvement in water quality was noted from June 1 to June 9, largely due to better weather.

Rainwater infiltrates the sewer system, and to prevent street flooding, excess water carrying fecal bacteria is diverted into the Seine. A new reservoir, capable of storing 50,000 cubic meters of water during heavy rainfall, was inaugurated in May to address this issue.

Water quality in major city rivers can be affected by runoff, illegal dumping of chemicals, and boat traffic. Paris’ mayor Anne Hidalgo has reaffirmed her commitment to take a dip in the Seine before the competitions start, although she postponed her swim until after the snap elections in France, concluding on July 7.