TOKYO -- No watertight doors were installed at nine water purification plants for tap water that were submerged by floods triggered by Typhoon Hagibis in mid-October, although they are situated in areas that local governments assumed could be inundated, the Mainichi Shimbun has learned.
There are at least 578 water purification plants across the country where no flood countermeasures have been taken even though they are situated in areas prone to immersion when flooding occurs. About two weeks after Typhoon Hagibis, a water purification plant in the Chiba Prefecture city of Kamogawa, eastern Japan, was submerged at the time of torrential rain on Oct. 25. It is therefore an urgent task to take countermeasures.
The typhoon, this year's 19th, cut off water supplies to 163,243 households in 14 prefectures including Tokyo. Of those, some 40% -- 63,698 in six cities and towns in the northeastern Japan prefecture of Fukushima and the eastern Japan prefectures of Ibaraki and Tochigi -- were left without tap water because a total of 10 local water purification plants were submerged. The 10 facilities include one each in the Fukushima Prefecture cities of Iwaki and Tamura, one in the Ibaraki Prefecture city of Hitachiota, two in the Ibaraki Prefecture town of Daigo, three in the Tochigi Prefecture city of Nasukarasuyama and two in the city of Tochigi.
Nine of the 10 plants, excluding the one in Tamura, are located in areas that prefectural governments have designated as zones that could be inundated under the Flood Control Act, but no watertight doors were installed at any of the facilities.
In Iwaki, where a levee of the Natsui River burst during the typhoon, water supplies were cut off to some 45,000 households at one point. An official of the municipal government's waterworks bureau admitted that it had not assumed that the city's water purification plant would be flooded as a result of the river dike bursting.
"We had believed we should prioritize the renovation of our aging water purification equipment and make the facility quake-resistant, and didn't take any particular measures against typhoons," said the official. "We thought if muddy water flowed into the facility, we would need to adjust the amount of disinfectant, but never assumed that it would end up under water as a result of the dike bursting."
When torrential rains hit western Japan in July 2018, some 264,000 households in 80 municipalities in 18 prefectures were left without water because local waterworks facilities including purification plants sustained damage.
This prompted the Health, Labor and Welfare Ministry to examine 3,521 major water purification plants across the country. The ministry then found that 758 of such facilities, or 22% of the total, are situated in areas designated as zones prone to floods, and that no anti-flooding measures, such as the installation of watertight doors and floodgates, had been taken at 578, or over 70%, of the 758 facilities. The huge cost of installing watertight doors poses a challenge.
In fiscal 2018, the ministry deemed 147 of these facilities, which could trigger particularly large-scale water supply cuts, in need of emergency countermeasures and began to subsidize one-third the cost of anti-flooding measures to waterworks bodies that lack financial resources.
However, the 10 water purification plants that were inundated in mid-October are not covered by the project.
Masakatsu Miyajima, professor of construction engineering at Kanazawa University, says, "Water purification plants are prone to flooding because they are situated near rivers, and need countermeasures. However, as the finances of waterworks operators are worsening due to the aging of society and depopulation, the national government needs to expand budgets for such programs. Residents should also stockpile water and local bodies should make arrangements for cooperation between themselves over water supplies in emergency cases," he said.
(Japanese original by Haruna Okuyama and Mei Nammo, City News Department)