Participate Palmy

How we achieved six shortlisted options

This new page has been developed in response to public demand for more detailed information about how we achieved the six shortlisted options. Published 2 July 2020.

Stage one: Fatal flaw analysis

We started with 36 options. To reduce the options to a long list, a fatal flaw analysis was completed. The criteria used is described as:

Options that have clear and significant defects will be removed from being considered further. An option will be classed as fatally flawed, and will not progress to stage two, where it clearly:

  • poses a significant increase in public health risk
  • will significantly increase adverse environmental, cultural, social effects on the river
  • has unproven technology
  • prevents growth and economic development in Palmerston North
  • is not consentable under the Resource Management Act
  • has whole-of-life costs that are absolutely unaffordable

At the end of this process we had a long list of 26 options.

Investigating the long list 

Photo shows table that summarises the longlist options for Nature Calls.

Click on the image to see a summary of the longlist options.

In determining a potential shortlist of options, our technical experts reviewed all 26 options against a range of criteria to determine which options merited further development and should proceed to consultation and engagement. The assessment criteria are outlined in the table below.

All options include consideration of innovations in wastewater management, conveyance and treatment. The detail has not been developed at this early shortlist development and assessment phase but will be developed for the preferred option. Specific innovations being considered include:

  • strategies to reduce wastewater generation from residential and tradewaste sources
  • wastewater collection options
  • beneficial re-use of treated wastewater options
  • residuals management options
  • byproduct alternatives waste stream beneficial reuse options
  • options for innovations

Stage two: Traffic light assessment

This is a simple and easily understood method for assessing and scoring a large number of options. Those with a high number of red scores are unlikely to progress to the shortlist. For the traffic light assessment, the options will be scored against the following:



Public health Degree of public exposure to health risks in treated wastewater (including through land application or re-use options).
Natural environment Potential adverse effects on the receiving environment, including the Manawatū River - particularly in relation to water quality, soils, and aquatic and terrestrial ecology.
Māori cultural values Potential adverse effects on the mauri of natural resources, on kai moana, and on the relationship of Māori, their cultures and traditions, with ancestral lands, water, sites, waahi tapu, and other taonga.
Social and community considerations Potential adverse effects on social and community values relating to amenity, recreation, and food gathering.
Financial implications Comparative capital, operational, whole of life costs of the options. Where relevant, this includes considering land acquisition costs, capital gains, and product net revenue.
Technology and infrastructure

Degree to which the option:

  • uses reliable and proven technology
  • can be staged
  • is able to be constructed (and within an appropriate timeframe)
  • allows for resource recovery / beneficial re-use.
Resilience Degree to which the option is resilient to natural hazards and climate change and offers operational resilience.
Growth and economic development Supports the city's projected population and economic growth.

To enable Council to compare and select from the 26 options, a traffic light system was used. For each of the 26 options, the eight criteria were scored using one of the traffic light colours of red, orange or green, depending on how well the option achieved the target standard or expectation. Initial scores were developed by each of the technical experts for their specific field of expertise. The collated traffic light scoring was then workshopped to develop an agreed shortlist of options. These options were presented to Council for its endorsement in June 2019.

During the assessment of the financial implications of the options, three options were identified as having whole of life costs well over $1 billion (and in one case over $2 billion). These options were scored red for financial implications. Through the workshop process and subsequently through Council it was agreed that these options be fatally flawed under the fatal flaw criteria of “whole of life costs are absolutely unaffordable”.

At this short list stage of the project, the options are conceptual and have been developed to provide context around the scope and key elements for options which discharge to the full range of receiving options and a small number of dual environments. Each of the options has been developed to meet known receiving environment standards and a general understanding of the soils available. No specific site selections have been made for any of the key components of any of the options. Specific site and location selection will follow more detailed investigation once a preferred option is selected.

The next stage will be a Multi-Criteria Analysis (MCA) to be undertaken in late 2020. This will involve technical experts and iwi, who will be asked to assess a range of criteria for each of the options in further detail, to inform Council and key partners in their MCA weighting and scoring.

The detailed assessment of effects has not yet been undertaken for all six shortlisted options. This is because to complete this work on all options would be cost and time prohibitive and considered wasteful where options are unlikely to proceed. Further, more detailed work will be undertaken on only one or two options which are considered most preferred to enable Council to make a final decision.

Following selection of the preferred option, a formal Assessment of Environmental Effects will be undertaken which will include detailed treatment and engineering design and costing, and assessments of effects from environmental, cultural, economic and social perspectives.

The objective is to identify the option that satisfies the environmental standards as we know them to be and best meets the other criteria.

Summary of key effects identified across each of the six options

Photo shows table of traffic light scores for the six shortlisted options (red, green and orange).

Expand the table to see the traffic light scores for each option.

This draft shortlist contains options that would discharge the city’s treated wastewater to a range of receiving environments. All options but option 1 involve a component of land application and involve shifting the discharge location for part or all the city’s treated wastewater.

The traffic light assessment indicated that the adverse effects on public health, natural environment, Māori cultural values and social and community considerations are generally low to medium.

The orange scores partly reflect uncertainty about the significance of the adverse effects of options. Some caution has been taken in defining the significance of adverse effects at this stage of the assessment process. However, options 1 and 2 are likely to have high to very high adverse effects on some values. In contrast the indicative estimates of the financial cost of these options are the lowest.

Option 1

The Manawatū River receives contaminants from both non-point and point source discharges upstream of the council’s wastewater discharge. This has over time, resulted in a deterioration in the water quality and negative impacts on invertebrates and plant life. It has also meant that people cannot swim or harvest food from the river year-round. Even if the treated wastewater is improved there will still be contaminants discharged to the river and therefore the restoration of the river to a state where it can be used for continuous recreation will be incomplete. The option will provide some improvements to the overall water quality of the river. For this reason, we ranked the effects of the discharge on the natural environment as moderate.

Because any discharge of wastewater has the potential to continue to have an adverse impact on the river, we ranked social and community effects as being high. This is because it provides opportunities for social activities, such as:

  • passive recreation i.e. walking, running, cycling and gatherings
  • recreational fishing
  • kayaking and canoeing
  • swimming
  • education

Continuing to discharge to the river may prevent these activities from increasing in frequency and occurring more widely. There is a strong desire from communities upstream and down stream of Palmerston North, to improve the river’s water quality. Over time, we may see some improvements to water quality and the diversity and health of fish and plant species in the river. However, the continued discharge of wastewater to the river, despite this being at a much higher treatment standard, may not meet the aspirations of the community. For these reasons, we ranked the impacts of the discharge to the River as high on social and community effects.

All options will be designed to meet future growth demands for the next 35 years (consent duration) for the city. However, there are other potential effects to be considered and options that involve discharging to the Manawatū River, there may be indirect impacts on tourism and economic growth. This has been identified if the river’s water quality is not improved and there is lost opportunity to develop the cities tourism around the River. For this reason, we ranked the effects on growth and development as being moderate.

Option 2

The effects on the river for option 2 reflect the scoring determined in option 1. For example, the continued discharge of wastewater has some negative effects on community and social well-being. For this reason, we saw the same effects occurring in option 2 as 1 and ranked these as high for both public health and social and community considerations.

This option does change the timing, volume and quality of this the discharge in a way that will contribute to improving the water quality of the river. It also includes a discharge to a new location within the river that is less sensitive to nutrients (Opiki area) than at Tōtara Road. This option was identified as having moderate effects on the natural environment.

We would design the final option to account for natural hazards and climate change including sea level rise and extreme wet weather events. There are still the potential effects from earthquakes to consider. This option was scored low for potential risks to natural hazards.

The technology, financial implications, growth and development were scored low risk on the basis option 2 requires less land than others, which reduces the overall cost of this option. It also provides a balance between locations that means the investment in treatment technologies and catering for growth without restricting growth can be achieved.

Because this option has some land-based treatment and mitigation is provided by establishing a wetland or land passage prior to discharging to the river, this option was ranked as moderate from a Māori culture perspective.

Options 3 and 4

Options 3 and 4 have a low degree of public health risk or effects on the environment. This is because the treatment and discharge to land can be managed through consent conditions, which meets environmental standards. From a public health perspective, the effects can be managed through consent conditions that limits any potential exposure.

Land that is 2,500ha to 3,500ha in area is limited within the region and highly expensive. These areas are likely to be used for agricultural purposes or be near the coastline. Option 3 is ranked high for financial implications. Less land is required for option 4 and therefore we ranked this as having a moderate financial implication.

The areas of land needed in options 2, 3, 4, 5 and 6 are not able to be accommodated in the Palmerston North City boundary. An option that occupies significant areas of land that is currently farmed or could be farmed, could result in an adverse effect on communities and social networks. For this reason, the social and community considerations were ranked moderate.

From a Māori culture perspective, the options 3 and 4 are ranked has having moderate effects as while it is preferable to discharge to land, there is still a remaining proportion of treated wastewater going to the river.

Land-based options will require investment in infrastructure between the treatment plant and the discharge location. The pipelines, pump stations and storage facilities would need to be designed to minimise potential effects from earthquakes, flooding, tsunami, storms, forest fires and disease (if forestry is carried out). There are a number of other factors to consider when identifying where the site and infrastructure will go, these include: erosion, stream crossings, land movement, flooding. These locations can be avoided, and the option will be designed in a way that the effects are minimised. For this reason, the resilience criteria were scored moderate for options 3 and 4.

Climate change has the potential to impact on all options. Land-based options are impacted by high intensity rainfall events where flooding occurs and we are unable to discharge to land, however prolonged dry periods will however improve the efficiency of the discharge. Sea level rise is expected to have limited adverse effects on the land options within the 35-year period (consent duration). However, if land is being considered along the coast (sandy soils) there is the potential for sea level rise, storm surge, erosion risk and/or groundwater table levels rise. Options 3 and 4 were scored moderate risks for resilience and technology.

Option 5

In order to discharge the treated wastewater to groundwater, the water quality will need to meet the same levels achieved in option 1 (to the river). Where there are areas of shallow groundwater, the proposed discharge may help improve the existing state of the groundwater quality (if it is poor). Buffer zones would be used to avoid pathogens entering groundwater. Option 5 was scored low risk to public health and the environment.

The effects of the discharge to the river, land and groundwater are interrelated on the basis that the discharge can enter rivers and the ocean via groundwater. In any option, these effects would be avoided through achieving high treatment standards and avoiding locations where there are existing water supplies. The effects of this option on social and community considerations was identified as being moderate to low.

As identified in the land-based descriptions above, the effects on growth and development in the region are similar. These options are identified as having low impacts on growth and development potential in the region.

The potential effects for this option directly relate to those identified in the land-based options (refer above). However, there are additional risks to this option that includes: prolonged wet weather can contribute to groundwater mounding and may require mitigation. Sea level rise will have limited effects on land located away from the coast. On this basis, option 5 is identified as being a moderate risk to resilience.

A discharge to land provides some mitigation to treat the wastewater and is the preferred solution from a Māori cultural values perspective. The option is scored as moderate effects from a Māori cultural perspective.

Option 6

As identified in the discharge to the river, there are potential effects from contaminants entering water. However, the treatment levels the treatment plant will be designed to meet will achieve environmental standards. On the basis the treatment levels and rate of discharge is managed to minimise potential effects on the ocean, there are minor effects on the ocean. The impacts on the natural environment are identified as being low.

This option does provide better dilution and dispersion of the treated wastewater and therefore is less likely to cause any risks to public health. Investigations into how long the pipeline and outfall need to be to avoid wastewater dispersion occurring in areas of recreational activity will be further undertaken if the option is selected. From a public health or community perspective, the impacts of the discharge may be more moderate given the use of the ocean for recreational activities and commercial fishing activities.

All options will be designed to meeting the future growth demands of 35 years (consent duration). However, there are other potential effects to be considered, and there may be indirect impacts on tourism and economic growth. The coastline is known for the following activities (but not limited to):

  • Commercial and recreational fishing and seafood gathering
  • Active recreation such as water sports, surfing, swimming 
  • Walking, motocross and four-wheel drive
  • Bird-watching
  • Tourism

There is also the potential for effects on growth and economic development, which scored moderate in the traffic light assessment.

Option 6 will require engineering design and locations to be identified that avoid the impacts of climate change and natural disasters. However given the location the discharge will occur and the extent of infrastructure needed to implement option 6, the resilience criteria was scored moderate.

The proposed discharge of wastewater to the ocean is not viable from a Māori cultural values perspective. However as there is a portion of waste going to land, some mitigation is achieved and the option was scored moderate.

Where would a treatment plant go?

The existing plant is located in a good location now. It is surrounded by existing industrial land that is at a reasonable distance from residential properties. The land is also designated for wastewater purposes and the underlying zone is industrial. This allows some flexibility to Council in undertaking upgrades. We have identified that if there is an upgrade, there will need to be improvements to prevent odour complaints.

An alternative location for a new plant would further increase the costs of all options considered. There is also a process underway to help Council identify what components of the existing plant could be used in each of the options.

For these reasons, it is desirable for Council to continue to use the existing plant site.

When will detailed assessments of effects from the proposal on the environment, social and community, cultural and economic wellbeing be undertaken?

The options and descriptions provided above are only conceptual at this stage and further investigation will be undertaken once a preferred option is identified. Site identification and technical assessments will be required to complete an assessment of environmental effects. This is scheduled to be completed in 2021 and into early 2022.

Will there be further consultation?

There will be another consultation process once the preferred option is selected. At this stage, there will be further information available. Once the consent is lodged (June 2022) there will be the formal consultation process under the Resource Management Act. This involves legal submissions and hearings.