Overview

• Interim checks of large pipes installed in or before fiscal 1994 found that, of 621 kilometers examined by Aug. 8, 72 kilometers (12%) require work within a year and 297 kilometers (48%) need measures within five years.
• The ministry sent written requests to municipalities overseeing these networks to move quickly to prevent road cave-ins following the fatal January sinkhole in Yashio, Saitama Prefecture.
• Local governments are surveying priority sections totaling 813 kilometers across 43 prefectures using drone imagery, visual inspections and tapping tests.
• Six underground cavities were identified near sewer lines — one in Kitami, two in Niigata City and three in Tamana — and officials say repairs completed or scheduled keep collapse risk low.
• Authorities asked cities to inspect roughly 5,000 kilometers of aging large pipes and to submit results for non-priority segments by the end of February 2026, with fiscal 2026 funds planned for replacements and parallel installations.