DELIVERING WELLINGTON’S EMERGENCY WATER NETWORK

Oscar van Paassen, Brett Eaton

1. Cardno Ltd, Melbourne, VIC, Australia

2. Cardno NZ Ltd, Wellington, New Zealand

KEYWORDS

Resilience, Strategic Planning, Potable Water, Community Involvement, Containerised Treatment Plants,

Emergency Preparedness, Infrastructure Coordination

EXECUTIVE SUMMARY

A significant earthquake in the Wellington region may damage the potable water network, and some customers could be without water for long periods. To overcome this, Wellington Water Ltd (WWL) initiated the Community Infrastructure Resilience project. The goal of this project was to provide 20L per person per day of potable water within 1000m of their residence during an emergency event. To achieve this, 22 containerised water stations were designed and built within a 15-month period to create an above-ground distribution network. These water stations are strategically located around the region to ensure all communities have access to emergency water.

INTRODUCTION

A significant earthquake in the Wellington region may result in damage to the potable water network, with modelling showing that some regions could take months to reconnect to the bulk water supply. After analysing the impacts on other infrastructure, a ‘water islands’ approach was adopted to reflect that the city will be broken up into isolated regions as transportation links between regions are damaged and broken. To overcome this, Wellington Water Ltd (WWL) initiated the Community Infrastructure Resilience project. The goal of this project was to provide 20L per person per day of potable water within 1000m of their residence by creating an emergency above-ground distribution network that can be utilised following an earthquake event. The messaging about the impacts this event would have on the community was also a key component to ensure the strategy would be effective.

This paper will discuss the challenges of the water network during a major earthquake event, and how it is proposed to supply emergency safe drinking water to customers isolated from the network. It will discuss the approach taken to determine the most suitable arrangement when a major earthquake occurs, and how the resilience of the system was enhanced by this approach. This approach could be adopted for other emergency events such as bushfires or floods.

YEAR CASE STUDY WAS IMPLEMENTED 2017 to 2018 CASE STUDY DETAIL

The vulnerability of Wellington’s water network to a significant earthquake has been a key risk considered by emergency management in the region. Previous studies show that some parts of the region could be without water for weeks or months following such an event, which combined with the impact on other infrastructure would be devastating for Wellington communities. Wellington Water – a council-controlled organisation managing water, sewerage and stormwater for the four local councils in the Wellington region - initiated a project to look at options that could be put in place to continue providing water in an emergency while the bulk supply is restored. From this background research and analysis, a target to provide 20L of water per person per day within 1000m of all residences in the region was adopted. The development of a ‘water islands’ approach led planning being balanced around the amount of water available within each island (from the existing network reservoirs) versus

how long it may be disconnected after a significant earthquake. The CIR programme was then initiated to identify and develop other water sources in islands that would have a water shortfall over the recovery period. The first stage of the programme was extensive water quality testing and bore analysis to identify potential water sources with sufficient supply. Following the results of this testing, Cardno and Wellington Water embarked on the second stage, which was the design and construction of 22 community water stations across the islands. All the stations were built within a 15-month period, which was a significant feat of management and coordination across stakeholders. The water stations consisted of containerised units that could be activated after a significant earthquake to achieve the programme target of providing 20L of water per person per day. Two types of water sources were identified for use at these water stations; ground water bores and surface water sources, where surface water sources are typically small streams and rivers. The 35-year design period for the water stations is based on these containerised water treatment plants that can become operational within 7 days following an earthquake. To ensure all communities will have access to an emergency water supply, an above ground delivery network of community distribution points was also developed. GIS mapping and rapid survey apps such as ArcGIS Collector were used to identify points for community water distribution to meet the target, and these maps were distributed to local council emergency management teams to incorporate into their plans. Across the whole programme, there was consistent coordination with the councils and emergency management groups to continue to spread the message for communities to store emergency water for themselves. The key points were to ensure that households would have enough water stored for 7 days of self-sufficiency (while the water stations were brought online) and to maintain this storage over time. The messaging is included when raising awareness about emergency preparedness and how the emergency water network will operate after an event.

SUMMARY OF OUTCOMES

This project successfully managed the following challenges:

• The expected “water islands” concept that will occur within the Wellington region, and the

emergency distribution network that will be set up to supply 20L per person per day within 1000m of

their residence

• The operational plan for the water stations and the downstream distribution network

• Engaging with multiple stakeholders and the local communities

• Designing water treatment plants and an associated delivery network for emergency community

operation and long-term readiness

• The implementation and operation of the containerised water treatment plants and the resilience

network

CONCLUSION

By installing the 22 water stations and developing an emergency above-ground distribution network, the Wellington region has created a resilient water supply network that is well prepared for the next significant earthquake.

Figure 1 - Community storage messaging

Figure 2 - times to restore bulk water supply (https://www.wellingtonwater.co.nz/your-water/emergency-water/above-

ground-emergency-water-network/)

Figure 3 - images showing the outside of a completed community water station, interior, and temporary inlet tank

Figure 4 - an overview of the treatment process for surface water station sites