Men's and women's triathlon races took place in the Seine, but the river could not be used at other Paris 2024 test events last month ©Getty Images

Paris' Deputy Mayor for Sports Pierre Rabadan has revealed plans for more stringent monitoring for pollution in the River Seine, after it was unusable for Paris 2024 test events in open water swimming and triathlon.

Swimming in the Seine has been banned since 1923 because of high pollution levels, but reopening it for public use in 2025 is a key legacy ambition for organisers of next year's Olympic and Paralympic Games.

Open water swimming and triathlon are due to use the Seine at Paris 2024, but there were issues at last month's test events.

An Open Water Swimming World Cup in Paris was cancelled after above-average rainfall led to sewers overflowing and a drop in the water quality of the Seine.

It prompted a warning from World Aquatics that "further work is needed with Paris 2024 and local authorities to ensure robust contingency plans are in place for next year".

Swimming in the Seine has been banned since 1923 because of high pollution levels but re-opening it after the Olympics is seen as a key legacy of hosting the Games ©Getty Images
Swimming in the Seine has been banned since 1923 because of high pollution levels but re-opening it after the Olympics is seen as a key legacy of hosting the Games ©Getty Images

The Seine was used for men's and women's races at the World Triathlon Olympic Games Test event in Paris, but not for the mixed relay or the World Triathlon Para Cup.

Organisers claimed this was due to "a significant discrepancy on the data between the results of the latest water quality tests provided by the laboratory and the high frequency sample analysers".

Both competitions were switched to the duathlon format featuring cycling and running.

Paris 2024 insisted water quality would be "improved" by the time of next year's Olympics and Paralympics.

Rabadan said that the triathlon test event had "led us, with the State and the regional prefecture, to put in place a plan, which we will announce in the coming days, which is much stricter for monitoring the network", said on Demain Le Sport organised by French newspaper L'Equipe and broadcast on France Televisions

Paris Deputy Mayor for Sports Pierre Rabadan said Olympic and Paralympic test events had led to plans for
Paris Deputy Mayor for Sports Pierre Rabadan said Olympic and Paralympic test events had led to plans for "much stricter" pollution monitoring of the Seine ©Getty Images

A faulty valve at a water treatment plant was blamed by Rabadan for the issues in the mixed relay and Para triathlon events.

Rabadan also claimed the Olympic and Paralympic Games had been "the driving force behind the acceleration of the necessary transformations" of the Seine's water quality.

A total of €1.4 billion (£1.2 billion/$1.5 billion) has been spent since 2016 to clean up the river, including installing wastewater collection networks for the 260 boats moored in Paris.

The still-under-construction Austerlitz basin is hoped to prevent heavy rain pushing wastewater into the river, and contribute to Parisian Mayor Anne Hidalgo's aim to have three sites of the Seine open for public swimming in 2025.

Triathlon, Para triathlon and open water swimming at Paris 2024 are due to start at Pont Alexandre III.