Swimming in the Seine during the triathlon and freestyle swimming events at the Paris Olympic Games is definitely not easy. On Friday, Paris town hall announced that the water in the Seine did not “generally” meet regulatory standards even if the trend is improving.
According to graphs posted online by the town hall, the level of concentration of fecal bacteria E.Coli, one of the two taken into account to authorize or not swimming in a natural environment, was greater than 1,000 colony forming units (CFU)/ 100 ml between June 1 and 8. The measurements are carried out on four Parisian analysis sites: Bercy, bras Marie, Alexandre III and bras de Grenelle.
Measures that have improved
However, if the threshold is above regulatory standards, we are far from the 6,000 and 8,000 CFU/100 ml which were recorded at the start of the period. On June 5, a peak of nearly 8,000 CFU/100 ml was reached at the most upstream site, that of Bercy. Conversely, on Sunday June 9, these values reached levels below this threshold of 1,000, retained by the international triathlon and open water swimming federations to authorize the holding of events.
With a week without rain, “the weather factors are working in the right direction”, noted Benjamin Raigneau, the director of cleanliness and water. According to him, the rainy spring generated “flow levels between three and four times higher than the normal flow of the Seine at the start of the summer period”. This natural factor was “the most penalizing in the analyses,” he added.
Rain, the main source of pollution
According to Benjamin Raigneau, the latest pollution peaks are due to “residual rain on the Marne which generates a spill”, or even a “malfunction of a unit” of the sanitation system, such as a storm overflow. Rain is therefore clearly the enemy of these events. It is for this reason that retention structures were built.
More information on the Olympics
However, suspense remains over the holding of the Olympic events since the “test events” of August 2023 which had to be largely canceled due to insufficient water quality. A plan B therefore consists of postponing the tests for a few days, but not changing location.