Long term solution for Shotover Wastewater Treatment Plant
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About the project
In response to the challenges with the disposal field at Shotover Wastewater Treatment Plant, QLDC allocated $77.5M through the Long Term Plan 2024-2034 to implement a new disposal strategy for the facility. This project commenced in October 2024 and a new disposal solution is expected to be in operation by the end of 2030.
The project aims to determine and implement a new solution to discharge treated wastewater from Shotover WWTP in an environmentally friendly, futureproofed, and sustainable way.
Chat to staff about the project at an upcoming drop-in session
We're hosting three drop-in sessions over the next two months, where you can stop by to chat with staff about the project, and learn more about wastewater treatment and the potential future long term disposal solution for Shotover Wastewater Treatment Plant.
All are welcome, drop by at any time on the below dates:
Community drop-in session #1
Date: Thursday 11 December
Time: Anytime between 5.00pm and 8.00pm
Location: Queenstown Events Centre
Community drop-in session #2
Date: Monday 15 December
Time: Anytime between 4.00pm and 7.00pm
Location: Queenstown Events Centre
Community drop-in session #3
Date: Thursday 22 January
Time: Anytime between 4.00pm and 7.00pm
Location: Queenstown Events Centre
Tea, coffee, water, and some light snacks will be available.
Long list options
Many potential solutions were initially considered alongside analysis of land available, leading to a long list of options being created.
This long list was presented to Councillors on 29 April 2025, along with the scoring of each option. The long list of options featured:
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High rate land disposal on Shotover Delta
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Moderate rate land disposal in Southern Corridor, Frankton and Shotover Country/Lake Hayes Estate
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Low rate land disposal on DoC Land and/or Coronet Peak
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Land flow path to river to Shotover or Kawarau Rivers
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Deep well injections at Frankton or Bridesdale
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Shallow well injections on the Delta
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Wetlands and land flow path to river on the Delta
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Well points or soakage wells at Frankton
Assessment of options
Each option on the long list was assessed against a Multi Criteria Assessment (MCA) Framework that considered:
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IO1 - The health and well-being of the surrounding waterways are maintained, protected, and improved where practicable to support water quality.
IO2 - The disposal of treated wastewater aligns with tikanga as guided by mana whenua.
IO3 - Ability to service the community’s and visitor wastewater needs now and into the future up to the equivalent flows projected for 2060.
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S&E1 - Mō tātou, ā, mō kā uri ā muri ake nei For us and our children after us.
S&E2 - Cultural impacts to sites of significance and access to sites for cultural activities.
S&E3 - Impacts to the surrounding environment.
S&E4 - Environmental impacts to surrounding catchment land, soil and groundwater.
S&E5 - Visual effects.
S&E6 - Amenity effects.
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CSF1 - Constructability and technical feasibility.
CSF2 - Sustainability - Carbon emissions and sustainable use of resources supporting organisational goals.
CSF3 - Operational reliability and maintainability.
CSF4 - Property difficulties and impacts.
CSF5a - Achievability of Indicated Outcomes.
CSF5b - Consent, Design, Construction, and Implementation Timeframe.
CSF7 - Costs and affordability.
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Short list options
The long list was refined to a short list of four options from the assessment to carry forward.
During further analysis and development of short list options, the lack of land available for a moderate rate disposal at Frankton resulted in this option being withdrawn as a standalone option and only able to be used as a supplementary option.
Additionally, analysis of the aquifer capacity on Frankton Flats determined that it had an assessed maximum capacity of 20,000m3/day, with a likely average capacity of 12,500m3/day without causing adverse effects. This analysis means that a standalone option on Frankton Flats is not considered likely to be able to accommodate the future disposal volumes required. As a result, Option C and D in the short list of options below are hybrid options that include a partial discharge to land, with remaining treated wastewater discharged to the Kawarau via a sub-surface wetland.
The short list options are:
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Option A proposes discharging treated wastewater via a rock outfall at the Shotover Delta into Kawarau River, using a land flow path.
Treated wastewater would be conveyed to the rock outfall for discharge either by a pipeline or channel.
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Option B combines a constructed wetland system with a land flow path before discharging treated wastewater into Kawarau River.
Treated wastewater would enter the wetlands and receive natural polishing and nutrient removal, before being conveyed to a rock outfall for discharge either by a pipeline or channel to Kawarau River.
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Option C involves injecting highly treated wastewater into deep bores located near Frankton, discharging into confined aquifers well below groundwater used for drinking.
This approach eliminates surface water discharge for approximately half the 2060 volume of highly treated wastewater, but requires additional treatment improvements to ensure performance of the bores are maintained.
This option would include remaining treated wastewater being discharged to Kawarau River, as per Option B.
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This method avoids direct river discharge for approximately a third of the 2060 volume of treated wastewater and provides natural filtration, reducing surface water impacts, but requires additional treatment improvements to maximise performance of the soak holes.
This option would include remaining treated wastewater being discharged to Kawarau River, as per Option B.
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These short list options provide the best balance of environmental protection, technical feasibility, and regulatory compliance within Queenstown’s geographic constraints.
The options also offer a mixture of proven reliability and future capacity, while minimising ecological impact and meeting stringent consent standards.
It’s important to note the short list options all include some form of discharge to water, due to the physical and environmental constraints of the district.
All options feature the following additional upgrades at Shotover WWTP, including:
Calamity pond: Already being constructed at Shotover WWTP as part of Stage 3 upgrades (repurposing an existing oxidation pond). The pond will provide the ability to store raw wastewater in the event the facility becomes inoperative, before it is returned to the start of the treatment process.
A second pond will be built to store treated wastewater if it is not meeting discharge requirements, or if any issues are encountered at the end of the treatment process (for example, at the UV disinfection stage).
Tertiary filtration: Installed before the UV disinfection step in the treatment process, working to reduce total suspended solids (TSS) and nutrients from discharge. This helps to improve UV disinfection efficiency, improving the quality of final treated wastewater discharged from the facility.
TSS are particles floating in the water, and are an important, visible indicator of water quality. Suspended solids can absorb light. Reduced light can increase water temperature and decrease oxygen levels, negatively impacting aquatic life.
Iwi position
Kāi Tahu considers the direct discharge of human waste (even if it has been treated) to natural water is unacceptable from the perspective of cultural value.
The Kawarau and Kimiākau/Shotover rivers are culturally significant to Kāi Tahu, with long held associations reflected in ancestral trails, mahika kai and nohoaka entitlements.
Since at least 1998 Kā Rūnaka have expressed their opposition to wastewater discharges to Kimiākau/Shotover River; their preference for land-based discharge; and their view that the Shotover Delta is an unsuitable location for land disposal.
The position of Kā Rūnaka is that a more holistic investigation of wastewater needs and alternatives for Queenstown is required that is not constrained by continuing to rely on treatment at this location.
We continue to actively engage with Kāi Tahu on the long term disposal solution for Shotover WWTP.
Next steps
Shotover WWTP remains a well-performing facility and treats wastewater to an extremely high degree – better than it ever has before. And as we begin to deliver a long-term discharge solution, treatment of wastewater at the facility will only improve further with the addition of a new calamity pond and the introduction of tertiary filtration.
While we acknowledge any future solution that involves discharge to water is a significant decision to make, it is important to note the options being considered (short list options) would ensure compliance with strict regulatory standards, provide operational resilience in all seasons, and accommodate future growth too.
With advanced treatment processes delivering high-quality treated wastewater, discharge to water plays a part in the most feasible, sustainable solutions for protecting public health and the environment.
Council will be asked to determine which solution they wish to proceed with at a Full Council meeting in early 2026.
Following a potential decision, consent for the future (long term) discharge solution would be lodged in May 2026, with construction to be completed by December 2030.
More information
We've created a 'Storymap' of the long term solution for Shotover Wastewater Treatment Plant, which summarises how the facility operates, more information about the recent performance issues, and further details about the different short list options available.
You'll also find a range of documents below detailing the different options that were assessed and how they were scored.
