A third-party committee concluded that the January 2025 sinkhole incident in Yashio, Saitama, was caused by corrosive sewage pipes, asserting that it was difficult for the prefecture to prevent the accident despite inspections.
On January 19, a third-party investigation committee, led by Yozo Fujino, president of Josai University, released its final report regarding the sinkhole incident that occurred in Yashio City, Saitama Prefecture, in January 2025. The committee identified that the sinkhole was caused by a sewage pipe that had corroded due to hydrogen sulfide, determining that it was unlikely the prefectural authorities could have prevented the incident with existing inspection methods.
The report confirmed that the sinkhole appeared directly above the deteriorated sewage pipe and stated that no other external factors could be attributed to the collapse. The committee's investigation suggested that a gap in the pipe, caused by corrosion, led to the formation of a cavity above the pipe, which eventually resulted in the road collapse. Furthermore, it was pointed out that during an inspection in 2022, the prefecture failed to capture clear images of the damaged area due to water splashes, indicating a lack of thoroughness in their investigative procedures.
Although the report criticized the prefectural authorities for not conducting a more careful examination, it concluded that the practical technology to inspect the cavity around the pipe did not exist at the time. Thus, the report ultimately stated that it could not be asserted that the collapse could have been prevented, even if corrosion had been detected earlier.
