Bacteria Water

Can the River Seine accommodate swimming during the Paris Olympic Games?

The River Seine is a key element in the Paris 2024 Olympics. A boat parade will open the ceremony, and two events are scheduled there – marathon swimming and swimming leg of triathlon.

The pollution levels of the Seine has raised concerns about athletes’ health.

What is the current situation?

Weekly results are published by the monitoring group (State and City of Paris) based on Eau de Paris analysis. The first three monthly bulletins showed that the water was not suitable for bathing. The latest data published Thursday shows that the river is suitable for swimming six days out of nine between June 24 and August 2.

What conditions make a river swimmable?

The test measures the levels of two bacteria, E. coli and Enterococcus Faecalis.

According to European standards the safe limit for E coliis 900 colony forming units (cfu/100ml) while the threshold is 330cfu/100ml for Enterococcus.

What are the factors that influence water quality?

Benjamin Raigneau is the director of water quality for Paris City Hall. He says that four factors are responsible for water pollution.

Rainfall More rainfall means more pollution runoff

The level of pollution on the Seine River is affected by rainfall, UV index, temperature and river flow. Photo by Reuters

UV Index: “The faster bacteria die, the higher the UV Index,” says Raigneau.

Temperature : As the temperature rises, bacteria will die faster. Raigneau said that the difference between the water’s temperature at 16 degrees Celsius and 22 Celsius, which is the usual summer temperature, is significant.

The speed of the flow: the faster the flow, higher the pollution.

What have you done to improve water quality?

To reduce pollution risks on the Seine, the city of Paris constructed a basin that can hold 46,000 cubic meters of waste water.

After the rainwater is collected in Austerlitz basin, a 30-metre-deep structure that’s the size of 12 Olympic swimming pools, it will be pumped through a tunnel and into a treatment facility. Once the water has met the health standards, it is poured into Seine.

How does the decision to allow swimming come about?

A technical committee will be formed every afternoon, the day before the familiarisation session for the athletes (swim) and the competition, to bring together all those involved in the water quality issue in the Seine. (City of Paris Paris 2024 International Federation Regional Authorities Meteo France).

American Joel Stratte McClure, 75 completed a short swim on the Seine River on July 4, less that a month prior to Opening Ceremony. Photo: AP

After the meeting of the technical committee, a preliminary analysis of the weather is done.

A final meeting with all players is held at 3.30am the day before the competition.

Who is the decision maker?

The International Federation of the sport.

What happens if it is too cold to swim on D-Day

Organisers said that contingency days for both sports were planned for summer 2024, giving us some flexibility.

The Eau de Paris lab will analyse the water twice daily. This will make the decision-making more precise and refined than ever.

In the event that the competition is not able to take place despite postponements, then the marathon swimming will take place in the reserve of Vaires-sur-Marne where canoeing and rowing events take place. The triathlon will also be changed into a duathlon.