Courtesy of WOWSA, Odaiba Marine Park, Tokyo.

After numerous Japanese open water swimmers got sick or were hospitalized in a national open water swimming competition in Odaiba Marine Park, there were calls by the athletes to move the chosen location of the 2020 Olympic 10K Marathon Swim to a cleaner and safer venue.

But FINA confirmed that the water quality was adequate and no public concerns were raised.

Subsequently, the local media and the triathlon community expressed concerns about the water quality in Tokyo Bay and in the Odaiba venue in particular.

After heavy rains which are not infrequent in Japan, untreated sewage flows into Tokyo Bay from waterways across the city. Since Odaiba sits alongside the natural coastline of Japan – but far within huge artificial islands that have filled in the outer parts of Tokyo Bay – the natural ebb and flow of the ocean is altered.

Odaiba is a large artificial island in Tokyo Bay across the Rainbow Bridge from central Tokyo. It was initially built for defensive purposes in the 1850s, dramatically expanded during the late 20th century as a seaport district, and was later developed beginning in the 1990s as a major commercial, residential and leisure area.

Odaiba was initially a series of six island fortresses constructed in 1853 for the shogunate to protect Edo (modern-day Tokyo) from attack from the sea, the primary threat being Commodore Matthew Perry’s Black Ships which had arrived in the same year. “Daiba” in Japanese refers to the cannon batteries placed on the islands.

In 2017 during an independent water quality test, E. coli bacteria and other microbes greatly exceeded the triathlon governing body’s safety standards for water quality in the bay. This was not a surprise to the citizens of Tokyo or open water swimmers who have competed there.

With renewed pressure from the IOC, the Tokyo metropolitan government vowed to improve its sewage treatment facilities and double its current purification capacity.

On 20 days of the 26 days that formal tests were conducted, the amount of E. coli exceeded the accepted limit for the International Triathlon Union by up to more than 20 times. For open water swimming, which reportedly has lower standards although the swimmers are in the water more than four times as long as triathletes, the number was reportedly seven times higher than the acceptable limits.

If a rain occurs during the Tokyo Olympics, it is highly unlikely that the water quality will meet the IOC or governing bodies’ own standards given the current situation.

But the organizing committee has promised that sufficient purification devices will be installed by the 2020 Olympics and the International Triathlon Union has accepted their promise. As a result of the promises made between the organizing committee, and the installation of underwater screens that would surround the triathlon and marathon swimming courses to keep out further contamination, the IOC and the International Triathlon Union, Odaiba Marine Park will remain the Olympic venue for the Olympic triathlon event.

IOC coordination commission chairman John Coates said, “I am assured those matters are under control, coming under control, and are certainly receiving attention.”

According to FINA officials, this decision is also acceptable for the Olympic 10 km marathon swim event.

Water quality during summer is a source of concern, but we hope that by the Olympics we will have achieved a stable water quality. We want the Olympics to be an opportunity to enjoy outdoor water sports and swimming in Tokyo Bay,” said an official of the Japan Triathlon Union.

The 50 finalists in the Olympic 10 km marathon swim also certainly hope so.

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