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Hihi Wastewater Treatment Plant Upgrade

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Hihi's wastewater treatment plant needs to be replaced. The Council wants to understand the community preferences to support the development of options. The project team held information ‘drop-in’ session on Sunday 11 July at the fire station on Marchant Road, Hihi to talk about the future of Hihi’s wastewater treatment plant to learn more about community views.

The goal is to achieve an affordable and sustainable solution for the community, that is future-focused. We would like to understand what ‘affordable’ and ‘sustainable’ means to the Hihi community and mana whenua. We also want to make sure that we share a similar vision for the future.

Staff will be on hand at the information session to talk about the options are on the table and to answer any questions you may have. It is an opportunity for us to hear what the community considers to be affordable and sustainable. It's also an opportunity to understand if the community wants Council to maintain the existing level of service.

Residents and ratepayers of the Hihi community and surrounds were invited to participate in an online survey. The survey closed on 31 July. Council will report back to the community in due course.

Following successful consultation with hapū, residents and ratepayers of the Hihi community, agreement has been reached to replace the ageing aeration tank as an initial stage in the upgrade of the wastewater treatment plant. The intention of this initial stage is to address the high priority need without compromising the community’s desire for further engagement in determining an affordable and sustainable long-term solution for the plant.

Preliminary design options were presented to the community collective at a meeting held at the Hihi fire station on 2 September 2022. This meeting agreed to progress the following single tank option to detailed design. This is now well underway with site survey, geotechnical, PSI contaminated land investigations, HAZOP and safety in design complete; while equipment and technical evaluations are nearing completion.


The agreed option will extend into the adjoining Reserve for part of the tank placement and a new accessway to the treatment plant. Earthworks are planned to commence in early 2023 after the holiday season. Landscaping options for the screening of the treatment plant and new accessway is to be located within the Reserve and will be planned in conjunction with the Te Hiku Community Board Reserve Plan for the Marchant Rd Reserve.

As agreed at the September meeting, detailed design will be presented to the community collective for review. This is likely to occur early in 2023.

The project completion date is June 2023.

Questions and answers

What's the history?

The last comprehensive community engagement happened in 2011 when the community confirmed their preferred option was to relocate the plant. However, it was determined that the most affordable option was to construct a new plant on the existing site. Since 2011 a number of remedial works have been completed to keep the plant operational and compliant.

Council has investigated what the options are, based on using the existing site, and which of those options will result in the best outcomes for the community. However, we want to engage with the community to make sure we consider growth, location, climate/environment and to other related community concerns before we develop the preferred option. This includes considering what the community’s desired levels of service are.

The risk of plant failure has been high for a long time. What has changed?

There are visible signs of significant deterioration which suggest that the risk of complete failure of the aeration tank is imminent.

What needs to be done?

All expert evidence supports the replacement of the plant. The question is how best to achieve that. We need to repair the failing structures, we need to increase the area in which the plant is located, we need to stabilise (refurbish) the wetlands and prepare for resource consent renewal.

What are the options?

We think the options are:

  • Replace the failing parts of the plant and keep using the rest of the plant (do minimum)
  • Build a new plant on the existing site
  • Build a new plant in a different location
  • Remove plant and transition to individual treatment systems

Is there a short-term option?

We are investigating a short-term option while we develop an affordable and sustainable long-term solution. Replacement of the tank (and associated failing structures and equipment) is our best short-term approach. However, this option does not address all the issues and may not meet the conditions for resource consent renewal in 2022. Short-term costs are in addition to the cost of the final solution and may result in a higher overall cost.

What will it cost? What have we budgeted for?

The Long Term Plan 2021-2031 includes a budget of $5.9m over the next two years to construct a new treatment plant at the existing location. This is an estimated cost which would be refined in the detailed design phase.

Why is the Council’s 'preferred option' so expensive?

We need to keep the existing plant operating during construction and commissioning of the new plant. This limits our design options. A modular solution lends itself to this particular challenge but it is costly.

If it is so expensive at this site, why not use another?

Selecting another site comes with its own costs, including land purchase, technical investigations and consents. It will not necessarily reduce the costs and is likely to take longer to implement.

In 2011 we investigated relocating the plant outside the residential area (adjacent to the wetlands). It was widely supported by the community, but eventually discounted because the benefits did not outweigh the costs.

Can we use the land at the wetlands site?

The wetlands site, together with an adjoining property, is being considered as an option.

The resource consents are due for renewal in 2022. What is the process?

The process of renewing a consent can be quite complex. Northland Regional Council (NRC) has great resources to explain the process: https://www.nrc.govt.nz/consents/consent-application-process. Council prepares the application and submits it to NRC for resource consent processing. NRC might ask for further information to allow them to make a sound decision. Once they are satisfied that they have all the relevant information, they will publicly notify the application at our request. Anyone can make a submission on a publicly notified application and be heard by independent commissioners.

What is Council's position on investigating discharge-to-land options?

In the past, we have investigated options for discharging to land as an alternative to discharging to water in several locations including Rāwene, Ōpononi, Kohukohu and Taipā. Recent updates to the Regional Policy Statement for Northland give a clearer requirement to consider land discharge options as part of the consent renewal process. We are investigating land-based discharge options for Kaitāia and Kaikohe.  We will investigate this option for Hihi.

Who will make the decision?

Ultimately elected members make the decisions about our wastewater treatment infrastructure. Their decisions are informed by technical experts and the guidance of our senior leadership. As representatives of the people of the Far North, they consider the wants and needs of the communities in balance with the constraints and regulations on Council.


13 Marchant Road, Hihi  0494  View Map

Last updated: 02 Apr 2024 4:18pm