News Japan survey finds 300 km of sewer pipes at risk, 72 km set for urgent repairs

A nationwide survey by the infrastructure ministry has revealed that close to 300 kilometres of ageing sewer pipes in Japan are in danger of causing road collapses. The warning comes in the wake of a deadly accident in January in Yashio, Saitama Prefecture, when a truck plunged into a sinkhole, killing its driver.


On 17 September, the ministry released the findings at a panel of experts convened to devise measures to prevent such tragedies. The investigation, launched in March, focused on roughly 5,000 kilometres of large sewer pipes—at least two metres wide and in use for over three decades. Engineers carried out inspections using cameras and visual surveys, checking for corrosion, sagging and other structural weaknesses.

Of the 5,000 km, 810 km were prioritized for inspection due to factors such as soft ground similar to the Yashio site, elevation differences that increase corrosion risk, or a history of collapses or confirmed corrosion. At the Sept. 17 meeting, the ministry reported on the condition of 621 km of these priority areas. Of these, 297 km in total, or 48 percent, were found to require countermeasures. Among these, 72 km managed by 71 municipalities were classified as urgency level 1, while the remaining 225 km fell under urgency level 2.

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Speaking of sinkholes, there was one in Fukuoka just June , so it's definitely something that catches your attention. Since different agencies are in charge of what's underground, and some local governments don't have strong finances, it's kind of worrying.

Fukuoka: Prefecture, Municipalities, and Related Agencies Exchange Views to Prevent Road Cave-ins
A meeting was held on the 7th to discuss ways to prevent road cave-in accidents. Officials from Fukuoka Prefecture, municipalities, and related agencies exchanged opinions on the issue.
The meeting took place at the Fukuoka National Highway Office, with participants including representatives from Fukuoka Prefecture, local municipalities, and organizations connected to road management.
In June of this year, during construction work to install a new stormwater drain on Kokutai Road in Fukuoka City's Chūō Ward, a road cave-in occurred. Several other cave-in accidents have also been reported within the prefecture, making countermeasures a pressing issue.
At the meeting, reports were presented on last year's road inspections by electric, gas, and water utility companies. It was noted that repairs had either been completed or were scheduled for nearly all locations where problems were found.
The Fukuoka National Highway Office stated that it intends to continue working closely with municipaliti

Britain has huge diameter sewer pipes…but they were nearly all laid in Victorian times and so are occasionally prone to cracking and collapse (Queen Victoria was an amazing engineer, with her golden pick axe and tiara). This very fact put me off buying a house on an 'unadopted road' meaning the local council was not liable for repair of the little cul de sac's infrastructure! Should the sewer need replacing, the ten or so residents would have to pay huge amounts for repairs!

When they redid the pipes on my street , it took 3 months of major hassle. They dug up my front lawn down 7 feet. Killed a beautiful cherry tree there. Dented the end of my newly made driveway. Glad they only do it every 100 years or so.

Actually I'm surprised its only 300kms of problem pipes in Japan. It feels like an almost negligible number - just a few kms per city, which, considering a lot of these pipes are probably vintage 1950 (or earlier) seems like a totally manageable problem. But I'm no civil engineer... maybe there are compounding issues.