Efforts to make water supply facilities earthquake-resistant through vertical cooperation

　In the Noto Peninsula Earthquake that occurred on January 1, 2024, severe damage to water and sewage facilities occurred, and in particular, water purification plants, sewage treatment plants, and pipelines directly connected to those facilities were extensive and long-term. Recovery has been prolonged due to the fact that emergency facilities in water and sewage systems, which have an impact on the long term, have not been earthquake-resistant.
　In addition, in order to enable the use of domestic water even in the event of a disaster, it is important to ensure both the water supply and sewerage functions. We have once again recognized the necessity of systematically and intensively promoting seismic retrofitting of water and sewage pipes connecting to important facilities such as evacuation shelter.
　Based on the above, in cooperation with Sewerage and Rivers Bureau, we organized the concept of earthquake resistance of water and sewage facilities and formulated the "Yokohama City Water and Sewage Seismic Improvement Plan (PDF: 289KB)".

　The "Water and Seismic Improvement Plan" is a plan in which the government has instructed all water utilities and sewer managers to formulate the plan in order to promote earthquake resistance together with water and sewage based on the damage of water and sewage facilities due to the Noto Peninsula Earthquake. .
　In Motoichi, in order to build a water and sewage system that is resistant to disasters, water and sewage systems that require measures, water and sewage pipes that connect to important facilities such as refuge, etc. We devised "Yokohama-shi water and sewage earthquake resistance plan" in January, 2025 to promote earthquake resistance together.

　The planning period of the water and sewage seismic retrofitting plan is approximately five years from January 2025 to March 2000. After that, it is assumed that it will be updated every five years.

The main items stipulated in the water and sewage earthquake resistance plan are as follows.
[Main contents of the plan]
　① Targets
　② Plan period
　③ Establishment of important facilities such as refuge
　④ Seismic retrofitting of water supply systems
　⑤ Seismic resistance of water pipes connected to important facilities such as refuge
　⑥ Seismic retrofitting of high-point facilities in sewerage systems
　⑦ Earthquake resistance of sewer pipes connected to important facilities such as refuge

　We will give priority to seismic retrofitting of water supply facilities, water purification plants, and distribution reservoirs that have a very significant impact when affected by the disaster, and aim to complete them in approximately 15 years until 2040. Of these, during the five years from FY2025, which is the acceleration period of the new Yokohama City Earthquake Disaster Prevention Strategy, to FY2011, we will implement earthquake resistance with the highest priority given to the Sagamiko system, which is a natural flow system.
　Regarding water pipes, we will complete earthquake resistance by FY41, but we will aim to complete earthquake resistance as soon as possible based on the importance of pipelines.

　In Motoichi, we push forward earthquake resistance of water supply facilities systematically, and earthquake resistance rate is higher than the national average.

　The following figure shows the earthquake resistance schedule for steep facilities (water supply facilities, water purification plants, water pipes, distribution reservoirs). By abolishing the Banyu River system Kosuzume Purifiction Plant, which lacks earthquake resistance, in fiscal 2040, the rate of earthquake resistance at water supply facilities, water treatment plants and distribution reservoirs is expected to be 100%.
　In addition, about facilities of Banyu River system, we carry out necessary measures based on policy of abolition.

　In addition to 459 locations in refuge, 41 locations in evacuation shelter, 459 locations in the city and ward offices and Public Works Office, 79 locations in the disaster base hospitals, and 92 emergency hospitals*, which were not covered by the Water Works Bureau.
※Of the 92 locations, 55 locations overlap with disaster base hospitals.

　In past large-scale earthquakes, damage is concentrated on small-diameter pipes (water supply: water distribution pipes, sewer: branch lines) compared to large-diameter pipes (water supply: water distribution mains, sewer: main lines). . Based on these circumstances, the city is focusing on seismic resistance of small pipes with a diameter connected to important facilities, both water and sewage systems. In addition, we will share the maintenance plan and progress of water and sewage, and efficiently increase the number of important facilities where both water and sewerage have been earthquake-resistant.
　As for water supply facilities, we aim to complete the earthquake resistance of water distribution pipes connected to important facilities over the next 20 years. However, evacuation shelter, which does not have emergency water supply facilities such as underground water tanks for disasters or school water tanks, is expected to be completed by fiscal 2027, the medium-term management plan period.
　For sewerage facilities, evacuation shelter is scheduled to complete by fiscal 2025, emergency recovery bases are scheduled to be completed by fiscal 2024, and disaster base hospitals are scheduled to be completed by fiscal 2029.

　As of the end of FY2023, there were 357 important facilities where both the water distribution branch (water supply) and the branch line (sewer) have been earthquake-resistant, and about 60% of the facilities have been earthquake-resistant. (357/616 = 58%)

　The distribution branch connecting to important facilities is expected to be completed in the next 20 years, and it is expected that the small pipes with a diameter connecting to important facilities will be 100% for both water and sewerage.

　●Water and sewage earthquake countermeasure
　●earthquake countermeasure of the sewer

　Water Works Bureau has established "disaster water stations" in elementary, junior high schools and parks within approximately 500 meters of their homes as a place where anyone can obtain drinking water in the event of water outages due to disasters. In the event of an emergency, the reservoir will also serve as a water station in the event of a disaster. In each case, water can be supplied by bringing a container such as a plastic tank.

　●Pamphlet "City of Yokohama, Water Works Bureau Disaster Countermeasures"

　●Water stations during disasters