One of the most important services the Queenstown Lakes District Council (QLDC) provides its community is the reticulation and treatment of wastewater on behalf of its residents and ratepayers, before returning the water to the environment. Recently the performance of its Shotover Wastewater Treatment Plant (WWTP), located in Frankton, has attracted attention in local media.

The Shotover WWTP is a modern treatment facility capable of producing high-quality treated water. The treatment plant itself is currently performing well and producing water that meets the quality parameters required by its discharge consent (granted by the Otago Regional Council).

The treated water is designed to be returned to the environment, in this location the receiving environments are the Shotover and Kawarau rivers. Prior to 2019, the treated water was discharged directly to the Shotover River (in accordance with the consent conditions of the time).

In recognition of the cultural sensitivities around direct to water discharges a new disposal system was commissioned in 2019. Known as the ‘Dose and Drain’ disposal field, the system was intended to allow the treated water to soak into the ground prior to entering groundwater and ultimately the Kawarau River. While Council respects this land contact for the important cultural function it plays, it isn’t relied on as part of the treatment process.

The disposal system has experienced performance issues which has resulted in persistent ponding within the field, along with periodic spillover of treated water beyond the designated site. Put simply, the treated water is not soaking into the ground at the rate it was designed to. And while QLDC has been actively working to understand the field’s failings and to improve performance, a new and more reliable approach is required to enable the controlled return of treated water to the environment in the future.

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QLDC has allocated $77.5M through the current Long Term Plan to develop and implement a new disposal strategy for the Shotover WWTP. This project is underway, commencing with an assessment of options and working towards identification of a preferred disposal solution. Any new solution will require a new discharge consent to be obtained and it is anticipated that an alternative disposal approach will take some years to implement. That is the reality of delivering infrastructure projects in New Zealand, and is a challenge being met by local authorities across the country.

As a consequence of the disposal field’s inability to operate in a manner consistent with its design and the associated resource consent, the Otago Regional Council (ORC) has issued QLDC with two abatement notices and a series of infringement notices. QLDC is committed to working proactively with the ORC around solutions for the community’s wastewater, and is supporting ORC with their monitoring and investigation of the facility’s performance. QLDC is regularly testing and reporting on the treated water quality to ORC.

Despite these challenges it is important to highlight that there has been considerable investment in this treatment facility over the past decade. These upgrades have resulted in significant improvements to the quality of the treated water whilst also providing for the capacity to meet the growth demands of the Whakatipu basin.

Right now, work is underway on the construction of a second process treatment train at the plant. Once complete (at the end of this year) this investment will allow the oxidation ponds to be fully retired and will achieve a further step change in the quality of the treated water produced by the plant.

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