Field measurements and investigations have identified the most reliable and safe water sources.
Finding groundwater sources is not easy. You need:
- a large ‘catchment area’ uphill of the proposed site so enough water is seeping underground
- rock with lots of cracks in it to let the water flow underground
- a spot to drill in that is free from contaminated land.
Finding surface water sources is not easy. You need:
- suitable water quality
- suitable flow of water - a six litres a second flow rate would be sufficient to supply approximately 10,800 people every day.
Frequently asked questions
How were the locations selected?
A number of criteria were used to help select the sites for investigation:
- Regional supply – the location of the site in relation to existing reservoir locations, proposed surface water abstractions and desalination points, as well as access to possible underground water sources
- Accessibility – recreation areas were priorities as such sites would be easily identifiable to the public, and easily accessible following a significant earthquake event
- Proximity – how close the site is to population centres and to critical customers such as hospitals was considered, as well as whether the site was close to major recovery routes
- Operational viability – the ability to support the emergency equipment required at each distribution point, as well as being able to support recovery efforts i.e. can be used to fill water bladders with water (for distribution further afield)
- Gravity – whether gravity could be used to move water. This will minimise the reliance on scarce fuel reserves following an emergency
- Resilience – the need to avoid known liquefaction, tsunami or secondary hazard zones as well as being accessible via resilient road links
- Security – whether it is likely that the sites will remain undeveloped for the foreseeable future
- Built environment – need to avoid contamination of the water source from the built environment (such as ruptured wastewater mains, possible chemical contamination or areas of historic contamination)
- Community – how likely the community is to be cut off from the water network or other water sources after a major earthquake
What happens if the tests prove that the bores are viable?
If the testing indicates that the bore is viable, it will then be placed on a list for further investigation. Once selected, the bore will then proceed to the development stage. This will mean working with the councils to develop the infrastructure required to access the water in an emergency.
What tests will be carried out on the water samples?
The bore will be pumped for 72 hours at a constant rate. This will help us understand whether the aquifer is recharging and what rate we can pump at sustainably without the well going dry.
We’ll be collecting water samples near the end of the pumping test and will test them to make sure that the water is safe to drink. We’ll be testing for bacteria and heavy metals, as well as other factors that could impact taste, smell and appearance
Would the water need to be treated before it is drunk? If so, how will it be treated?
We’ll be testing the water as part of our investigations. What treatment will be required depends on the result of our water quality testing.
How would the permanent bores look?
How we will access the water in an emergency will determine how the permanent structure will look. We’re exploring a range of options from storing the equipment offsite (in which case, the bore will just have a manhole flush to the ground, to building an above ground community water stations.
How would we access the water in an emergency?
The emergency groundwater bores will be activated by Wellington Water staff or community responders following an earthquake. The water will be pumped out of the bores into either a large water bladder on the back of a ute or into a water tanker for distribution to the community.
How much water will each bore supply?
We are aiming to have each bore to have a flow rate of approximately 2 litres per second.
How deep do the bores go?
The depth of the bores will range from 40 metres to 100 metres deep, depending on ground conditions.
Didn’t Christchurch do okay without an above-ground network?
Christchurch's water supply network is fed by bores distributed throughout the city - like a spider’s web style system of bores which is adaptable to faults.
In Wellington we're dependent on three water sources that feed the network. The restoration times are a culmination of the fact that the water supply network crosses multiple fault-lines and many customers are a long way away from one of the region’s three water sources.
With no viable network alternative in many parts of the region, our customers will need to wait until repairs are carried out before drinking water can be restored. It is notable that parts of Wellington City are likely to be without drinking water for more than 100 days. This represents a serious risk to our customers’ safety, and to the ability of the region to recover from a significant earthquake.