Key points about land discharge
We don’t have the amount of suitable land we’d need within our Council boundaries for these large volumes. That means we have to look to neighbouring areas.
Ideally for the well draining soils we need, land should be close to rivers or the ocean. Through computer analysis we’ve identified some locations which have the right soil types in Horowhenua and Manawatū districts. We have not done any field work or testing to prove they’d be suitable, and that is why we are not identifying them during this consultation.
Once we know which option the public is leaning towards, we will then conduct soil tests and talk to landowners. The land areas include buffers and non-irrigation areas to prevent contamination and adverse effects for neighbouring areas.
Land-based discharges would require us to purchase land from owners. As the land we’d need requires good drainage, there’s also a chance we’d be taking away land that would otherwise be good for farming or growing food.
Feedback received from local iwi Rangitāne to date is that land application options are generally preferred over the discharge to the Manawatū River or ocean. However, given the very large land area required, it will be difficult to avoid discharging to land that does not hold significant cultural value for Māori. We’re investigating this issue and have not yet identified areas with suitable drainage and topography that meet these requirements.
Key points about river discharge
Any river discharge will also treat the wastewater through either a wetland or land passage. Wastewater would pass through these before entering the river.
This ensures the water has had a final filter before entering our awa. Wetlands are like a kidney – filtering out any remaining nutrients we wouldn’t want in our river.
We’re currently investigating what size wetland we’d need for the options involving a river discharge.
The Manawatū River is a significant taonga (treasure) for Rangitāne and the city. Even discharges of highly treated wastewater to the river are likely to be perceived negatively by parts of the community, with some community members refraining from recreation activities in the river as a result of the discharge.
The discharge of even highly treated wastewater would negatively impact the mauri (life force) of the river and impact the mana of iwi, who are kaitiaki (guardians) of the river. These negative effects may be partially mitigated by the installation of a wetland or land passage facility.
Key points about groundwater discharge
We’ve engaged environmental scientists and engineers to inform us how best to achieve regional plan and national targets for groundwater quality. Any consent application would ensure these targets are met.
If a groundwater discharge is the preferred option we’d investigate and identify all public and private water supplies. However, we still expect there will be community concern about the discharge of even highly treated wastewater to groundwater.
Very careful analysis will be needed to ensure that this does not negatively impact private water supplies or increase the potential for flooding or surface ponding on neighbouring properties.
Some landowners would be directly impacted if Council sought to acquire land for the rapid infiltration system and land application site.
Iwi have concerns about the potential for adverse effects on the mauri (lifeforce) of groundwater and connected streams. This may be partially mitigated by including a wetland prior to the rapid infiltration facility and by applying part of the wastewater to land during drier months of the year.
Care will be needed in locating the land application site to ensure that sites and values of significance to Māori and others are as far as practicably avoided.
Key points about ocean discharge
We’d ensure the treatment process for our wastewater meets guidelines for ocean water quality. We’ll also continue to investigate the best location for the outfall pipe.
The ocean is a significant taonga (treasure) for iwi and is highly valued by the whole community.
Discharging treated wastewater to the ocean may be perceived negatively by parts of the community, particularly those living in coastal communities. Some community members may also restrict their recreation and food gathering activity as a result of the discharge.
The discharge of treated wastewater would negatively impact the mauri (life force) of the ocean, the ability to harvest kaimoana and impact on the mana of iwi, who are kaitiaki (guardians) of the ocean.
These negative effects may be partially mitigated by applying a portion of the wastewater to land. However, the benefits of this mitigation are likely limited. We would carefully consider recreation values when selecting the location of the outfall pipe.