Ikenogawa treatment plant flooded during last September’s heavy rain disaster in Hitachi City (Courtesy of the city)
During the heavy rains caused by Typhoon No. 13 in September last year, which caused extensive damage to Hitachi City in Ibaraki Prefecture, rainwater entered through the joints of aging sewage pipes, contributing to the flooding of the sewage treatment plant. This was discovered through an investigation by a team from the Ibaraki University Faculty of Engineering. The city was aware that rainwater was getting into the aging sewer pipes, but a person in charge said, “It wouldn’t be a big problem during normal rain, and they didn’t take the risk of heavy rain seriously.” (Shuhei Sano)
The research team held an interim report meeting in March at the Hitachi Campus in Hitachi City, where the Faculty of Engineering is located, and explained the factors that led to the spread of flood damage in the city. According to the team and the city, rainwater flows into the sewage treatment plant “Ikenokawa Treatment Plant” (2 Higashi Narisawa-cho, Higashi-Narusawa-cho, in the same city) through sewage pipes. Due to the flooding, water treatment functions, which remove dirt from sewage before it is discharged, were temporarily suspended.
However, the treatment plant is located on low-lying land near the coast, and large amounts of rainwater flowed in from nearby flooded rivers and surrounding roads. A city official said, “Rainwater poured in from many places almost simultaneously in a short period of time.We don’t know how much of an impact the rainwater flowing through the sewer pipes had on the flooding damage.”
In line with the five-year plan (FY24-2028) formulated in FY2022, the city will check the condition inside the pipes once every five years to every few decades, and update them as necessary. ing. When the plan was drawn up, they did not anticipate heavy rains comparable to last fall’s Typhoon No. 13. A person in charge says, “We need to maintain and manage the structure while keeping in mind the lesson that it can cause flooding during heavy rains.”
Professor Masashi Fujita explaining about flooding from old sewage pipes at an interim report meeting in Hitachi City (Photo provided by Ibaraki University)
The main source of revenue for sewerage projects is usage fees collected from citizens. With revenue expected to continue declining due to population decline, it is financially difficult to replace a large number of aging sewage pipes at once. For this reason, the city wants to reduce expenses by researching ways to make maintenance and equipment longevity more efficient.
Professor Masashi Fujita of the Ibaraki University team commented on the problem of aging sewage pipes, which pose a risk during heavy rains: “Finance and disaster prevention are both important, so it’s difficult to find a balance between the two.This could lead to an increase in usage fees.” “We should think about this while communicating with residents.”
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At the research team’s report meeting, Professor Kaoru Kobayashi also explained that many small and medium-sized rivers in the city had flooded. Noting that water levels in small and medium-sized rivers were rising faster than in large-scale rivers, he said, “For small and medium-sized rivers, it is necessary to examine methods that allow evacuation even in a short period of time, as well as methods of disseminating information such as evacuation instructions.” .
At the interim report meeting, professors from the same faculty explained the results of their research in each specialized field, and people from the city, companies, and students participated. The team plans to hold a final report meeting in September, which will mark one year since the typhoon occurred.
Tags: Ibaraki University teams investigation reveals aging sewage pipes contributing factor flooding treatment plant Hitachi heavy rains Tokyo Shimbun TOKYO Web
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