Olympic triathletes, paratriathletes and long-distance swimmers will hopefully get through their events without any issues from the water next year. A survey conducted at Odaiba Marine Park, the site of the Tokyo 2020 Olympic triathlon and the 10 km marathon swim events, has yielded largely positive results.

Odaiba Harbor in Tokyo, Japan.

Test results

With the exception of one of the 12 testing days, it was concluded that the use of underwater screens successfully reduced the levels of coliform bacteria within the limits stipulated by international federations. This was despite the fact that the area outside of the screens greatly exceeded the ideal levels due to heavy rainfall. Levels of enterococci, another form of bacteria, were also within the agreed limits.

The study was run from August 7 to 18 to correspond with the days of the Olympic and Paralympic Games. You can read all of Tokyo 2020’s findings here.

Use of underwater screens

The Tokyo 2020 organizing committee announced in March of 2018 that they would experiment with the underwater screens to help improve water quality after 2017 tests revealed an unusually high amount of bacteria levels in the bay.

Without the screens in use, the swim portion of the para-triathlon test event was cancelled in August after tests showed levels of E. coli reaching more than double the acceptable standard.

Moving forward, as the single-layered screens have proved to be effective, Tokyo 2020 plans to install triple-layered screens when the Games roll around next summer.

Results from surveys taken without the screens in place, both before and after the test with them, showed that levels of faecal coliforms were within the limits with the exception of when there was heavy rainfall. The level of enterococci exceeded the maximum amount on one day.

Another potential problem with the water conditions is the heat, though the survey showed that the temperature never rose above the maximum 31.0ºC. The highest it got was 30.8ºC, with the temperatures inside the screens 0.8ºC higher than outside the screens on average.

The organizing committee is considering moving the race start time up by one hour and allowing the underwater screens to float in an effort to deal with the potentially high water temperature.

Rio 2016 problems

The issues with the water conditions in Tokyo comes on the heels of the highly publicized Rio 2016 controversy.

Leading up to those 2016 Games, there were some startling findings on the state of the water in Guanabara Bay, where the triathlon and marathon swimming events would be held.

A study from the Associated Press showed the viral level of the water was up to 1.7 million times what would be considered dangerous in the US or Europe, and indicated that Rio’s water exceeded the California limit of 400 faecal coliforms per 100 millilitres by five times. There was even reported to be a floating corpse and severed arm found in the bay just weeks before the start of the Games.

However, after the test event in 2015, the triathletes weren’t bothered by the water conditions, and after the Olympic event itself, there wasn’t any backlash or widespread illness reported.

Though the potential issues in Tokyo are concerning, they pale in comparison to what was expected in Rio.

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