At the end of FY2024, only 14% of the purification capacity run by the Tokyo Metropolitan Government Bureau of Waterworks was seismically reinforced. The Bureau's Management Plan 2026, published on 30 March 2026, targets 76% by FY2035. Its ten main plants together treat up to 6,844,500 m³ a day for 13,928,448 people.
The pipes are further ahead
Other parts of the system are better protected. By FY2024, 75% of intake facilities and 84% of distribution reservoirs had been reinforced, and 52% of mains had seismic joints. Supply routes to evacuation centers and major stations were substantially converted to seismic joints by FY2022. The plan aims for 66% of mains with seismic joints by FY2035, and for intake facilities to reach 100% by FY2030.
Why the plants lag
Treatment plants cannot simply be shut for repair. The Bureau is reinforcing them one treatment train at a time while each plant keeps running. It is also building two alternative plants, a rebuilt Sakai plant and a new Upstream Purification Plant, so that Higashimurayama can be renewed later. Survey and design for that renewal starts in FY2029, and the Bureau expects to renew all of its plants over about 90 years.
What an earthquake would mean
The Management Plan 2026 puts the expected water outage rate after a major earthquake at 24% in FY2024 and aims to cut it to 16% by FY2035. The target for restoring supply moves from within 14 days to within 13. Capital spending to deliver this is planned at JPY 469.2 billion over FY2026 to FY2028, against JPY 132.4 billion in FY2024.
Which plants come first, how drought exposure in the Tone and Arakawa basins compares with the seismic risk, who now runs plant operations and how the program is funded at current tariffs are covered in the full report. The full report, Water Systems Overview: Tokyo Metropolitan Government Bureau of Waterworks, is available for USD 499 at https://ourfuturewaterintelligence.com/reports/water-systems-overview-tokyo-metropolitan-government-bureau-of-waterworks. For a free overview, read the Tokyo Metropolitan Government Bureau of Waterworks Utility Snapshot at https://ourfuturewaterintelligence.com/utilities/tokyo-metropolitan-government-bureau-of-waterworks.