“Earthquake-resistant” water pipes also break in Wajima City, expected to be a seismic intensity 7, but unexpected shaking
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In Wajima City, Ishikawa Prefecture, where a seismic intensity of 6+ was observed due to the Noto Peninsula Earthquake, water outages continue, and interviews with the city revealed that one of the main water and sewage pipes, an earthquake-resistant pipe that is said to have earthquake-resistant properties, had broken. Ta. It has been 3 weeks since the earthquake occurred on the 22nd. The city believed that the earthquake-resistant pipes would not be seriously affected by the magnitude 7 earthquake, but a combination of factors may have caused more damage than expected, and the city is likely to be forced to reconsider how to make the water supply system earthquake-resistant.
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Approximately 10,000 households in Wajima City have been without water supply since the beginning of the outbreak. The earthquake’s violent shaking caused cracks to appear in water treatment plants and other facilities, and the main water pipes that carry water to the area came loose at joints and broke.
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According to a city investigation, as of the 18th, breaks in water and sewage pipes had been confirmed in at least nine locations: five within water treatment plants and four connected to water distribution reservoirs. The investigation is limited to only a small part of the city, and there are fears there will be more.
Two of the main water supply pipes connected to the water distribution reservoir were earthquake-resistant pipes with NS-type ductile cast iron pipes that do not easily come loose at their joints. The water distribution reservoir had also been made earthquake resistant based on standards established after the Great Hanshin Earthquake in 1995, but the recent earthquake caused cracks in the reservoir, making it impossible to store water.
In accordance with the 2020 revision of the ministerial ordinance, the Ministry of Health, Labor and Welfare will promote earthquake resistance for important water facilities such as water pipes and distribution reservoirs to the extent that even the largest earthquake expected in the location where the facility is installed will not have a significant impact. We are asking local governments to do so.
Regarding the cause of the earthquake-resistant pipe rupturing, Hiroshi Togishi, director of the Wajima City Water and Sewerage Bureau, said, It appears that the slope was sliding due to stronger shaking than expected, and the earthquake-resistant pipe came off (at the joint).''I don’t know what to do next,” he says at his wits’ end.
The city is currently installing a bypass route that sends water directly from the water treatment plant to the city center without going through the distribution reservoir. The city hopes to repair the water supply by turning water on a trial basis starting on the 17th, and to resolve the water outage by the end of March. Meanwhile, no progress has been made in repairing the sewerage system, and the outlook for restoration is unclear.