A top Tokyo Olympic Games organiser has pledged to invest in keeping water clean and safe at marathon swimming and triathlon venues, where bacterial contamination was detected during the summer.
Toshiro Muto, Tokyo 2020 organising committee's chief executive officer, said in an interview with the Associated Press that officials have been trying out various measures at the Odaiba Marine Park venue, including underwater curtains to close off the venue, which have tested effective.
Muto says water quality has improved and further measures are being tried out.
The water quality survey during the summer found E.coli at concentrations up to 21 times the levels permitted by the sport's governing body, a surprise for a country known for cleanliness. This raised concerns among athletes.
The water issue came up in early October at a project review meeting of the International Olympic Committee and the Tokyo organising committee. Tokyo officials have ruled out moving the venue.
Muto said the metropolitan government has conducted tests on the problem using underwater screens, and Tokyo organisers are working with them to set a roadmap to improve water quality and keep it under control.
"Results of their experiments have demonstrated significant improvement," he said. "We will keep working on them so that we can take highly effective measures."
Test results have demonstrated that use of underwater screens in two layers could keep out 90 percent of E.coli inflow to the venue. Officials have been trying out curtains in double or triple layers to compare results.
Muto said adding a third layer of the screens could prove even more effective in keeping the water clean at the venue.
Metropolitan officials attributed the excessive reading to Tokyo's near-record summertime rainfall that affected sewage processing capacity. Japan's capital had 21 consecutive days of rain in August, the longest streak in 30 years.
Exceeding the processing capacity of sewage facilities can cause sewage water diluted by rain to be discharged into the ocean.