Why do we need to invest in a Hāwea wastewater solution?

    The existing Hāwea Wastewater Treatment Plant (WWTP) does not have sufficient capacity to treat the increasing wastewater flows from the township and those that will eventuate from projected growth.  These capacity constraints also mean there is no option to connect Hāwea Flat or the Hāwea campground to the scheme now or into the future. 

    As a result, Queenstown Lakes District Council (QLDC) is developing a business case to determine the best option for treating and disposing of wastewater from Hāwea and surrounding catchments.  

    This is a long term proposal. What's the interim solution?

    As part of the Three Water Reforms process QLDC was granted $9.47m in stimulus funding. Part of this fund has been allocated to an interim upgrade of the treatment plant to improve the quality of the treated effluent, providing time for the long term solution to be implemented.  

    Apex Environmental has been engaged to design and construct the interim solution which will utilise a Moving Bed Biofilm Reactor (MBBR) sidestream process.   MBBR is a fixed growth biological process which utilises plastic media to grow micro-organisms for treatment.  The technology is well suited to cold temperatures and constrained sites due to its small footprint. 

    The interim solution will allow for full utilisation of the discharge volume allowed under the Resource Consent (design can accommodate a peak of 1,000m3/day, current consent allows for up to 775m3/day).

    What other options were considered and how were they assessed?

    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 raw wastewater for treatment and disposal at Project Pure via public and private land.
    • Option 3b - Pumping of raw wastewater for treatment and disposal at Project Pure via Albert Town.
    • Option 4 -  Limiting investment into the maintenance of the interim upgrade only.  This option was considered only for the purpose of providing a baseline to assess the relative benefits of the other options.   

    We completed a robust Multi Criteria Analysis (MCA) of the shortlisted options to determine the preferred option for further design development.  Options were scored by representatives from both Beca (our designer) and QLDC on a 1-5 scale and input to the MCA. This was a two-step process whereby a QLDC team and a Beca team scored the options independently, followed by a moderation session with representatives from both organisations.

    The MCA assessed each option against the following criteria:

    • Whole of life costs:  Net present value of total cash costs (30 years)
    • Environmental wellbeing:  Impact on the natural environment
    • Social wellbeing:  Impact on the human environment and protection of the area’s culture/heritage
    • Consenting:  Likelihood of securing necessary environmental and planning authorisations
    • Achievability:  Difficulty and complexity of implementation by June 2026
    • Future-proofing:  Ability to respond to changes in demand and quality standards over time
    • Resilience:  Speed at which service can be resumed following disaster 

    The MCA tool we used was developed by a respected local economist with input from a cross-organisational working group. It is used for all new significant infrastructure investment projects. Each criterion within the MCA has a base weight that was agreed as part of the tool’s development process. Criteria and weightings are then reviewed and adjusted on a case-by-case basis to ensure appropriateness for the project.

    For this Hāwea wastewater project, four criteria within our MCA tool were not used for this project. They are:

    • Downstream economic impacts – No material economic downstream impacts were anticipated as a consequence of this project.
    • Economic wellbeing – It was agreed that this would be more appropriately considered as part of the detailed financial assessment to be completed as part of the business case. The whole-of-life costs for each option were considered an appropriate proxy for affordability in this instance. 
    • Cultural wellbeing - The cultural impacts of the project are to instead be assessed under the process developed with iwi. This assessment will be presented alongside the MCA and other decision-making considerations when making a final investment recommendation.
    • Risk – During moderation it was noted that project risk had already been accounted for within the scoring of other criteria, and accordingly was removed to avoid double counting.

    The weightings associated with the criteria removed from the assessment were redistributed proportionately across the remaining criteria (as shown in the table below).  


    We ran two tests to understand if our preferred option would change under different circumstances.  In the first test, we equalised consenting and whole-of-life cost scores (to see if our option would change if cost and consenting factors were the same). In the second test, we increased the weighting of the environmental, achievability, and social criteria. Our preferred option performed well in both tests.


    When would the long term solution be complete?

    End of 2026, subject to endorsement of the Business Case and confirmation during the design phase of the project.

    What diameter would the new pipe between Hāwea and Albert Town be?

    Further design work, including assessment of demand scenarios, needs to occur before we can confirm the size of the pipe.  To inform early cost and carbon impact assessments, we have assumed:

    • a DN280 poly ethylene pipeline for the paper road and road corridor sections, and
    • a DN200 steel pipe for the bridge crossings.  

    What will the emissions impact of this option be?

    A whole of life emissions assessment was completed for each short-listed option.  This assessment is underpinned by a number of assumptions; we are committed to periodically updating the impact assessment of our preferred option as design progresses.   

    Compared to the other options, the preferred option has the lowest operational carbon, and the highest capital (embodied) carbon.  We expect the capital carbon can be reduced through sustainability-in-design initiatives, and the operational carbon may further reduce as New Zealand’s electricity emissions becomes greener and/or an alternative solution for management of biosolids is introduced in the district.  Overall, the preferred option will reduce our emissions relative to retaining the status quo.  

    How will this project impact development contributions and rates going forward?

    It is too early to say exactly how this project will impact ratepayers and development contributions. Once we have validated our preferred option (due diligence is in process now), we will complete a detailed financial analysis. Generally speaking, connecting Hāwea to the Wanaka wastewater scheme will enable us to spread the cost of service across a much larger ratepayer base.