Is the River Seine deemed safe for swimming during the Paris Olympics 2024 Games

The River Seine will be crucial in the Paris 2024 Olympics, where it will host the opening ceremony highlighted by a procession of boats. Additionally, it will be the venue for two events: marathon swimming and the swimming segment of triathlon.

Nevertheless, concerns about athlete health have been raised due to pollution levels in the Seine.

1. What is the current status?

According to the monitoring group (State and City of Paris) and Eau de Paris water analysis, weekly reports are published. The initial three bulletins for June indicated that water quality did not meet bathing standards.The latest update on Thursday showed that the river met swimming standards on six out of nine days between June 24 and July.

2. What are the prerequisites for the river to be deemed safe for swimming?

Analysts assess the concentrations of two bacteria: E. coli (Escherichia coli) and Enterococcus faecalis. According to European regulations, the permissible level for E. coli is 900 colony-forming units (cfu) per 100 milliliters, while for Enterococcus, it is 330 cfu/100ml.

3. What are the determinants of water quality?

According to Benjamin Raigneau, Director of Water Quality at the Paris city hall, several factors affect water quality, including rainfall, which increases pollution runoff, and the UV index, which influences the degradation of pollutants in the water.

-Temperature affects the bacteria mortality rate: the higher the temperature, the quicker the bacteria die."Whether the temperature of the water is 16 degrees Celsius (60 Fahrenheit), or above 22 Celsius (71 Fahrenheit) like it usually is in the summer, it makes a significant difference," said Raigneau

-River flow rate impacts pollution levels: higher flow rates correlate with increased pollution.

4. What measures have been taken to enhance the water quality?

Paris constructed a storage basin with a capacity of 46,000 cubic meters to mitigate the risk of Seine pollution. Rainwater collected in the Austerlitz basin, a large structure 30 meters deep and comparable in size to twelve Olympic swimming pools, will be channeled through a tunnel to a treatment facility. Once the water meets health standards, it will be discharged into the Seine.

5. What criteria are used to determine if swimming is permitted?

The day before each familiarization session (athletes' swim) and competition, a technical committee convenes in the afternoon. This committee includes representatives from the City of Paris, Paris 2024, the International Federation, regional authorities, and Meteo France, all focused on assessing water quality in the Seine. Following this meeting, an initial analysis of weather conditions is conducted.

At 3:30 AM on the day of the competition, a final meeting is held with all stakeholders involved.

6. Who is responsible for making the decision?

The International Federation is involved in the sport.

7. What happens if the water is not safe for swimming on the scheduled day?

"There are contingency days planned for the summer of 2024 for both sports, which will give us some room for manoeuvre," organizers said. 

“Fuhemore, the decision-making process will be more refined and precise than ever, as the Eau de Paris laboratory will be analyzing the water twice a day”.

If, even after rescheduling, the competition cannot proceed, the marathon swimming event will relocate to the backup venue at Vaires-sur-Marne, traditionally used for rowing and canoeing events, and the triathlon will be modified into a duathlon.