With our current resource consent ending soon, our Nature Calls project is determining the best practicable option for how we manage our wastewater for the next 35 years.
It will be the largest financial and environmental decision our city needs to make for many years.
More than 1100 people had their say in mid-2020, with both full land and full river discharges receiving almost identical levels of support.
Recent scientific and technical reports have provided more insight into our options
The information that formed our public consultation was provided at the end of 2019 so consultation could occur in March, however Covid-19 meant that consultation could not occur until June and July of this year. We based our consultation on the information we had available, which at that time was mostly conceptual.
Over the course of this year, Council's experts have moved from conceptual level detail to a more technical understanding of the details behind each option. This work includes investigations that explore proposed treatment options and applying these to each of the options to determine preliminary effects on water quality and land based discharges, at desktop level only. This information was used to determine if we can meet water quality targets under the One Plan and resulted in a more refined set of options that include a river discharge.
The nature of the wetland and land passage components has been developed, as well as desktop analysis of the coastal conditions an outfall pipe could be located. Land application elements were explored at desktop level to determine how we could meet One Plan targets for nitrogen and leaching rates and refinement of the total land areas required. We have also initiated testing of wastewater arriving at and leaving the current plant to understand specific contaminants and how effectively they are removed e.g. emerging organic contaminants. This information will be valuable for refining the treatment component of which ever option or options is preferred.
Planned new environmental policy and legislation changes at a national and regional level will have an impact on each of our shortlist options, especially when discharging to the river.
To understand how we might meet future requirements, we have used advanced modelling tools to determine the potential effects of treatment levels and volumes of wastewater on periphyton growth in the river. The outcomes of the modelling confirm there are limited options we can consider that will meet these targets. Options with limited discharge to the river and substantial land based discharge are more likely to meet these targets in the river.
We’ve prepared a more detailed factsheet on the health of the river:
A refined shortlist
We’ve continued to undertake technical investigations and have refined the shortlisted options. The options continue to include a river discharge, varying combinations of land and river discharges, and ocean discharges.
- A river discharge all the time, with improved treatment to what we currently do
- A river discharge with improved treatment to what we currently do, and a small percentage discharged to land in low river flow
- Two river discharges, one at the existing treatment plant and a second below Opiki Bridge. Both with improved treatment, and a small percentage to land during summer low river periods.
Mostly land discharge
- 97% to an inland land application site, and a river discharge in exceptional circumstances
- 97% applied to a coastal land application site, and a river discharge in exceptional circumstances
Exceptional circumstances account for around 10 days of the year during very heavy rain.
Combined land and river discharges
- 45% applied to an inland land application site, and a river discharge for the remainder of the time
- 45% applied to a coastal land application site, and a river discharge for the remainder of the time
- 55% applied to an inland land application site and a river discharge the remainder of the time
- 45% applied to a coastal land application site and a river discharge the remainder of the time
- Ocean discharge, with a small percentage to land
- Full ocean discharge that can potentially accommodate the wastewater of our neighbouring councils
While an ocean discharge wasn’t as supported as the river or land-based options during consultation, we would like to further investigate the merits of a regional scheme that neighbouring councils could take part in in future years. The ocean option is most feasible to accommodate wastewater from our neighbouring councils or major industry. With recent progress with the government’s Three Waters Agency, and a likelihood of there being a regional water agency, we also believe it is something that should be investigated thoroughly.
The public consultation found that there was little public appetite for a discharge to groundwater. The investigations we have carried out have also identified that there are large land areas required and very high treatment levels needed to achieve one plan requirements. Therefore, very high costs have been confirmed for this option. For these reasons, that option has been fatally flawed and removed from the assessment process.
Refining the shortlist involves many experts and stakeholder input
We’re assessing the options through a number of evaluations, one of which includes assessing each of the options within a Multi-Criteria Analysis (MCA) process. An MCA is used in large scale and complex infrastructure projects in New Zealand and has been tested in the Environment Court. This process provides a systematic way of comparing options using a range of qualitative and quantitative measures. The initial workshops have been held with a wide variety of stakeholders, iwi, councillors and our technical experts.
In addition to the MCA, we’re also assessing the options through the lens of iwi in the region and are working with various hapu to determine what this looks like. We will also assess the options against our eco-city strategy, environmental policy legislation and the project objectives.
Public consultation to occur in 2021
The MCA process is helping us narrow down the options and enables Council to bring selected options to you for consideration in a second round of public consultation in early 2021.
Later next year, Council will choose the best practicable option to proceed with.
Once that decision is made, a resource consent application will be prepared and lodged before June 2022.
This process must continue, despite recent developments with the government’s Three Waters Reform and the consideration of a new agency or regional agencies that would take control of drinking water and wastewater. As nothing has been confirmed, nor timeframes set, we need to continue to work on our resource consent application to ensure we meet our legal obligations.