Upper Clutha Wastewater Conveyance Scheme

The existing Hāwea wastewater scheme was established in 1988 and includes a wastewater treatment plant (WWTP) adjacent to the Hāwea River. Treated effluent is disposed of using a combination of irrigation and in ground disposal trenches. The scheme currently treats wastewater from the existing Hāwea township.

The plant was upgraded in 2000 and has now reached capacity. An interim upgrade of the existing plant has been implemented to enable QLDC to complete the design and construction of a long-term solution.

The following options were shortlisted as part of the development of the Business Case.

• Option 1 - A new wastewater treatment plant on a new site with a new sub-surface irrigation area
• Option 2 - Upgrade of the existing wastewater treatment plant with construction of new rapid infiltration basins for discharge of treated wastewater
• Option 3a - Pumping of wastewater through public and private land for treatment and disposal at Project Pure
• Option 3b - Pumping of wastewater through Albert Town for treatment and disposal at Project Pure (preferred solution)

QLDC completed a robust Multi Criteria Analysis (MCA) of the shortlisted options to determine a preferred solution for further design development. The MCA assessed each option against the following eight criteria:

1. Whole of life costs
2. Environmental wellbeing
3. Social wellbeing
4. Risk
5. Consenting
6. Achievability
7. Future proofing
8. Resilience

Option 3b was determined as the preferred solution as it provides the best balance of environmental, social, cost, and resilience benefits to the area. Importantly, it can be implemented with the least consenting risk and does not require any land acquisition or new land access agreements such as easements.

The new pump station at Domain Road will convey wastewater from Hāwea along a new pipeline running down SH6, through Albert Town, and then on to Project Pure WWTP, making use of existing treatment and disposal infrastructure in the Upper Clutha.

The existing plant was built in 1988 and QLDC has recently completed interim upgrades to enable short term compliance with consent requirements for the plant. While there are benefits to a dedicated Hāwea WWTP, construction of a new plant or upgrade of the existing plant were ruled out for two key reasons:

1. The whole of life cost is estimated to be greater than the conveyance-based solution selected, due to construction costs associated with meeting the required treatment standards, and land acquisition and consenting costs.
2. A Hāwea treatment plant-based solution comes with risks associated with complex consenting and/or land acquisition requirements for a new or upgraded treatment plant. As a result, there is significant risk that a treatment plant-based solution could take many years to complete or is unable to be implemented at all.

The infrastructure has been sized to service Hāwea and to enable future connection of Hāwea Flats and the Hāwea Campground.

Hāwea is currently home to an estimated 1,000 Dwelling Unit Equivalents (DUE) with around 4,000 people enjoying the township and surrounding areas on a peak day. We have assumed a high growth rate in Hāwea for the next 30 years and are currently forecasting the number of DUEs to increase to around 4,000 and the population to be around 15,000 on a peak day in this time.

The upgrades will provide capacity for approximately 3,000 more DUEs, which meets the growth expected to occur in the area over the next 30 years.

The growth projection assumptions are considered conservative and as part of the design we have confirmed the population triggers for future upgrades. Therefore, future upgrades would be required earlier if growth is faster than expected. Upgrades may include additional buffer storage, construction of a second pipeline, a local treatment plant and disposal area, or a combination of further staged upgrades.

The population forecast used to determine the sizing of the new system allows for full occupancy of land in Hāwea and surrounding areas enabled by the Queenstown Lakes Spatial Plan.

Currently, all of Wānaka’s wastewater is pumped out to the Project Pure using the Albert Town No.2 WWPS and rising main. This includes most of southern and western Wānaka’s flows which are pumped from the Riverbank Road WWPS to the Albert Town No.2 WWPS. The Albert Town No.2 WWPS and existing rising main to Project Pure are forecast to reach capacity around 2028 - 2030.

The future need for a second pipeline and WWPS upgrades was identified when the first pipeline was installed in 2008, and funding for the replacement was provided for in the QLDC Long Term Plan 2021-2031. As part of this project, we assessed the pipeline alignment and WWPS upgrade options. Options included upgrading the existing Albert Town WWPS and constructing a second rising main out to Project Pure or, upgrading the existing Riverbank Road WWPS and constructing a second rising main from this WWPS out to Project Pure.

Ultimately, upgrading the Riverbank Road WWPS and constructing the rising main from this WWPS out to Project Pure was preferred. This is because this option increases network resilience by splitting Wānaka’s current and future wastewater flows between two pump stations, which will help to reduce the reliance on a single WWPS, provide the ability for either pump station to pump into either rising main if repairs and maintenance are required, and reduce the scale of upgrades needed at each pump station.

As with any large construction project, there will be some disruption while work is undertaken. This is likely to include noise, vibration, and construction machinery around work sites.

Large parts of the new pipeline running from Hāwea to Project Pure will be installed to the side of SH6 or within rural road corridors, meaning we can limit most of the project’s impact with short sections of temporary traffic management while these works are completed.

Other key impacts to be aware of include:

• Bridge works: We expect increased disruption while installing the new pipeline on Camphill Road Bridge and Albert Town Bridge. More detailed updates will be provided to the community and any directly affected people or businesses once we have more information on timing of works and the duration of any potential bridge closures.
• Albert Town works: Construction will be more noticeable as the project progresses through Albert Town from the bridge, and along SH6 to Mt Iron Roundabout.

Council staff will ensure open communication is maintained between members of the Upper Clutha community and the contractor delivering these works, to help minimise as much disruption as possible.

We’ve been engaging with NZTA Waka Kotahi throughout the design process for these wastewater upgrades and can confirm the new pipeline will be attached to Albert Town Bridge. We have taken steps during design to ensure that in the event the bridge is replaced, the wastewater pipe can be realigned and attached to the new bridge.

We will continue to discuss any opportunities to integrate our respective projects with our partners at NZTA.

The approved budget for this project in the QLDC Long Term Plan 2024-2034 is $80.1m. This includes $21.88m of grant funding from the Infrastructure Acceleration Fund (IAF) administered by Kainga Ora. QLDC is funding the balance of the $58.22m for this project.

The Infrastructure Acceleration Fund (IAF) is administered by Kainga Ora on behalf of the Crown. It provides councils with funding to support the delivery of critical infrastructure needed to enable housing development in areas of high housing need. Because the IAF contribution is a grant, it does not need to be repaid to the Crown; this means the community will benefit from a high-quality, future-proofed asset for considerably less cost than if QLDC funded the project without IAF support. Kainga Ora makes payments to QLDC on satisfactory completion of agreed milestones.

Wānaka and Hāwea ratepayers will contribute to the funding of this project, and other planned QLDC Long Term Plan 2024-2034 expenditure, via annual wastewater charges. Wānaka and Hāwea’s wastewater rates for next three years are provided in the table below, alongside the other wastewater scheme charges across the district.