Resilient water and wastewater networks: 8 things to consider if an earthquake hits

The study focused on, contributing factors that are likely to disrupt water and sewage networks in wake of an earthquake, the amount of water needed if pipes were cut-off, earthen ware vs. cast-iron piping, plus restoration estimations.  

We developed guidance on assessing the vulnerability of buried infrastructure and improving its resilience.

The research paper will help local authorities across New Zealand prepare for and respond to the next earthquake – whilst prioritising the requirements of lifelines that would be needed in such events.

Here’s what our research revealed: 

1. It’s not the shaking that causes most of the damage in pipelines, but the quality of the surrounding grounds: – we found that the performance of the ground’s (and associated grounds) played a significant influence on the damage occurred by an earthquake. – Thus, suggesting that ground should be surveyed and treated in built and residential areas.
2. The restoration time is also very dependent on ground conditions. Poor ground stability is extremely problematic and will take longer for repair.
3. Restoration of service involves several phases. It may take many years to fully restore service to the pre-earthquake condition. Priorities and needs change as restoration progresses through these phases.
4. When supplying lifelines such as water. there is a hierarchy of needs. For instance, the level of water needed for health centres would be 40-60 litres a day and these types of services would (likely) receive lifelines first.
5. Per average person, we estimated that in wake of a water shortage (due to natural disasters like earthquakes), the amount of water needed per day is 15 litres.
6. All utility materials will sustain damage. However, we found the degree of damage was a lot less in modern flexible pipes than the older earthenware and cast-iron pipes. Larger pipelines typically sustained less damage than smaller pipelines.
7. Resilience can be improved through a combination of improving the robustness of pipes, increasing redundancy, making it easier to make repairs and planning to respond to an event.
8. Resilience improvements can generate benefits that amount to more than ten times the cost involved.

Abstract

New Zealand’s Local Government Act requires Councils to provide for the resilience of infrastructure assets. But what does ‘resilience’ mean in this context?  How can the level of resilience be assessed?  What is an acceptable level of resilience?  How can community expectations regarding resilience be balanced against requirements to manage growth, service standards and concerns about ageing infrastructure?

To address these questions the paper will draw on preliminary findings from research work being undertaken into the seismic response of underground infrastructure. This research is being sponsored by the Ministry of Business, Innovation and Employment.  A methodology for assessing vulnerabilities to earthquakes and for improving robustness will be outlined.

This methodology will then be broadened out to provide a framework for ascertaining an appropriate level of resilience to natural disasters in general.