Assessing suitable well locations - Lower Hutt

Overview 

Background 

The Gear Island and Waterloo wells in Lower Hutt provide approximately 40% of the average annual water supply to the Wellington Region and up to 80% in peak summer periods. 

The existing infrastructure is vulnerable to natural events including earthquakes, tsunamis, flooding, sea level rise and saline intrusion. The condition of some of the existing well casings is currently unknown.  The Gear Island wells are estimated to be between 40-50 years old, and the Waterloo wells 30-40 years old. These are nearing the end of their design life of 50 years.  

Figure 1 shows the location of existing Knights Road water supply bores circled in yellow and Gear Island bores circled in red. The associated water treatment plants are shown as blue boxes, and the project area is circled in orange.   

Figure 1. Project location and existing water supply bores 

The Waterloo well extraction network is situated along Knights Road, consisting of eight water supply wells that flow into the Waterloo Water Treatment Plant. An additional three water supply wells (used when required) are in Petone’s foreshore and flow into the Gear Island Water Treatment Plant. 

We’ve setup a project to develop and implement replacement wells for the Waterloo treatment plant water supply wells to improve the resilience of this crucial water supply asset and enhance our understanding of the Waiwhetu Aquifer. 

Investigating possible locations for two new water wells 

An important part of the project is investigating possible locations for new water wells. We have identified two locations that assessments indicate would be good locations for water wells, following a comprehensive review of 93 possible locations across Lower Hutt. The kind of things we take into account when assessing locations include the availability of safe, healthy drinking water, proximity to the Waterloo Water Treatment Plant, and achieving value for money among other factors.  

We’re now fully investigating the suitability of these areas. The locations are shown below:  

Once the investigations at Hautana Square and Massey Ave are complete, we’ll look into the findings to determine whether these locations are suitable for a new well, based on set criteria.  

New water wells to improve resilience, rather than increase amount of water sourced  

It’s important to note that any confirmed additional well will not increase the amount of water sourced from the Aquifer, rather it increases overall resilience. To explain this, in normal operations we currently have eight wells operating at maximum capacity during the peak summer period (when water demand is at its highest annually).

By increasing the number of wells we use, we can spread the load, allowing all nine wells to operate at a more sustainable level (i.e. around 80%). This is known in the industry as having greater “redundancy”, or in other words, we’ll have a more resilience and reliable regional water supply. 

What are the next steps in the process 

Once we have reviewed the findings from the investigations at Hautana Square and Massey Ave, Lower Hutt, we will update residents and stakeholders, and confirm the next steps in the process. At this point, we will be able to confirm whether the two identified locations are suitable for water wells.