Build Back Better・Safe Utilities・Sewage Works

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Build Back Better・Safe Utilities・Sewage Works

Amidst the catastrophic damage suffered by sewage treatment facilities in the Great East Japan Earthquake and tsunami, we were able to prevent the sewage from 700,000 people from overflowing in the city, maintain a hygienic environment, and accomplish a quick recovery. Additionally, in the process of recovery we are implementing projects to reduce disaster risk and the burden on the environment.

Case Study

Build Back Better・Safe Utilities・Sewage Works

Quick restoration of sewage treatment capabilities and disaster-resistant, environmentally-friendly restoration

Which priority of action does the case contribute to?

4. Reduce the underlying risk factors.

5. Strengthen disaster preparedness for effective response at all levels.

Context

Sewage works facilities suffered catastrophic damage in the earthquake and tsunami. Pipelines broke in many areas of the city, and machinery as well as electrical power were lost at the coastal sewage treatment plant. Moreover, as water utilities in the city center recovered more quickly, there was a threat of sewage overflow.

Location

Sendai City’s Minami-Gamo Wastewater Treatment Plant and all of Sendai City

How was the problem adressed?

After the disaster, staff quickly carried out an initial response based on the Business Continuity Plan that was then being developed, making judgments in response to the conditions. Since the gate of the damaged treatment plant was destroyed, a portable pump and septic tank truck were deployed to handle localized overflows. In response to the loss of electrical power, fuel stored for electric power generators was gathered from key inoperational pumping stations around the city. In addition, the support networks we had built allowed us to receive aid from sewage works and other businesses around the country.

During the formulation of recovery policies for treatment facilities, we established a committee of experts from industry and academia and worked to create recovery initiatives that would not only restore the previous functionality of the sewage treatment plant, but also support the future development of the city. These included countermeasures for earthquakes and tsunamis as well as reduction of the burden on the environment.

Due to the topography between the city center and the damaged coastal treatment plant, as well as the location of the plant, it was possible to carry out simple treatment functions without power, through the natural flow of water downhill. Considering this, as well as the location relative to the sludge treatment plant, the time and cost necessary for recovery, and crisis management in a disaster, we deemed it desirable to rebuild the plant on the existing site. Using the recent tsunami as a standard for rebuilding, we decided to elevate the facility, install lids on tanks as a tsunami countermeasure, and establish appropriate evacuation areas for the safety of employees. Additionally, in order to secure electricity in times of disaster and reduce the burden on the environment, we decided to introduce solar and small hydroelectric power generators ad well as energy-saving equipment.

Results

Immediately after the disaster, we were able to prevent a large-scale overflow of the sewage of 700,000 people in Sendai City and maintain the city’s hygienic environment.

In addition, by incorporating the reduction of risk factors and reduction of the burden on the environment into the restoration process, we were able to build a disaster-resistant, environmentally-friendly sewage works.

Measuring success

Because preparations for an initial response had been completed in advance and staff were able to make spontaneous judgments and respond even in an exceptional situation, we were able to maintain sanitation in the city without enacting limits on the use of the sewage works and avoid a sewage overflow.

In addition, during reconstruction, we aim to reinforce existing disaster countermeasures and curtail energy dependence in order to realize a disaster-resistant, independent city system.

Relevance to HFA

Our city’s experience demonstrated the importance of advance preparation, including the preparation of a Business Continuity Plan and the creation of networks with related organizations. Moreover, in the restoration process, we are implementing comprehensive disaster-prevention measures that are also environmentally friendly, putting into practice the HFA priorities for action: “reduce the underlying risk factors” and “strengthen disaster preparedness.”

Potential for replication

The restoration achieved in Sendai City through measures addressing both infrastructure and systems could be a model for earthquake and tsunami countermeasures for coastal sewage works facilities both domestically and abroad.

Contribution by

City of Sendai (Construction Bureau).