Our services need to withstand shock and stresses. We have long-term plans to future proof the network to enable a strong regional economy and enhanced natural environment.
We began implementing our water supply resilience strategy “Towards 80-30-80” in early 2017. “Towards 80-30-80” is a long-term strategy focused on implementing a series of network improvement and community initiatives that will progressively improve the resilience of the water supply network over time.
The key outcome of the strategy is to have a “80-30-80” resilient water supply network in place that will provide 80 per cent of our customers, within 30 days of a reasonable seismic event (i.e. a 7.5 magnitude earthquake), with 80 per cent of their drinking water needs.
We work with a 'top down’ approach - focused on providing the key infrastructure we think is required to get our region back up and running again following a significant event.
Prince of Wales/Omāroro Reservoir
The proposed new 35 million litre Prince of Wales/Omāroro reservoir will add capacity to Wellington’s water storage network, significantly enhancing resilience to disaster events.
It will be built to modern seismic standards, ensuring it remains fully operational following a significant earthquake. It will also enhance the operational resilience of the water supply network, allowing Wellington Water to undertake essential works on other reservoirs, pipes and network infrastructure with little impact on local water supply.
Exploratory Harbour Bores
In 2016 it was agreed to explore the feasibility of tapping into the aquifer in the harbour as an alternative option. The reason for this investigation was to ensure that we are well informed on all potential options. The harbour bores option, if successful, could have potentially reduced the cost of the project by as much as 50 per cent whilst still achieving the resilience outcome.
Other benefits of the exploratory harbour bores include:
- Understanding the geology of the Waiwhetu Aquifer to increase our understanding of the likely impact scenarios after a large seismic event on aquiclude (the sediment cap on top of the aquifer).
- Enabling future constant monitoring of the aquifer pressures and water quality near the harbour entrance that will allow better management of the Waiwhetu Aquifer resource.
Two exploratory bores were drilled in the harbour. Following completion of the exploratory drilling, assessment of the probable yield and water quality from the bores was completed by hydrogeological specialists with Waiwhetu aquifer expertise.
While potable water was found at both locations, the quality and quantity were not as good as expected. The investigations completed indicate that the first bore site is likely to have produced between 2.5 and 3 MLD, and the second bore site between 10 and 20 MLD.
The water from both sites contains Manganese, Ammonia, and Iron requiring treatment to meet drinking water standards. The second bore drilled also identified traces of Arsenic, within treatable limits. These results confirm that additional treatment is required for the harbour bores option to be viable.
The water quality and quantity found in the harbour is different to that taken from the aquifer and treated at the Waterloo and Gear Island treatment plants, which requires little treatment by comparison.
Completion of the harbour bores investigations now provides confidence to proceed with further work on the cross harbour pipeline in the knowledge that all alternative options have been adequately explored and considered.
Read our 2 June 2017 media statement: Looking for drinking water beneath the harbour
Read our 16 August 2018 media statement: Council endorses cross harbour pipeline
Our work for long-term improvements to water supply resilience is made up of a combination of new initiatives and prioritisation of future improvement expenditure - renewals and upgrades.