Paraparaumu wastewater treatment plant consenting

We’re seeking approval from Greater Wellington Regional Council (GW) to continue operating the Paraparaumu Wastewater Treatment Plant (WWTP) for the next 15 years. This will allow time to determine the Best Practicable Option (BPO) for managing long-term wastewater discharges for the Raumati, Paraparaumu, and Waikanae communities. The application was publicly notified in late 2024.

As part of the consenting process, we’ve been upgrading the plant and working closely with iwi to identify and resolve potential issues ahead of a hearing, which is expected in early 2026.

Waikanae, Paraparaumu, and Raumati are all served by the Paraparaumu WWTP, located on Fytfield Place, Paraparaumu. The plant was originally commissioned in 1981 and upgraded in 2001/02. At that time, the Waikanae oxidation ponds (now Pharazyn Reserve) were closed, and all Waikanae wastewater has been pumped to Paraparaumu for treatment.

The Paraparaumu WWTP uses biological nutrient removal, one of the most advanced treatment processes in New Zealand. It treats approximately 10–12 million litres of wastewater daily to a high standard, protecting both human and environmental health.

Treated wastewater is discharged to the Mazengarb Drain, which drains into the Lindale/Mazengarb stream and then to the Waikanae Estuary.  During periods of low rainfall, treated wastewater makes up most of the stream's flow downstream.

Wastewater national environmental performance standards

Taumata Arowai released new national Wastewater standards, which came into effect on 19 December 2025. These standards set contamination limits that all new and replacement resource consents for municipal wastewater discharges must meet. The Paraparaumu Wastewater Treatment Plant (WWTP) discharge is classified as a “very low dilution environment,” meaning it must meet particularly high-quality standards.

Councils with applications already in progress, where a notification decision has been made (including ours), can either continue with their current application or withdraw it and lodge a new one under the new standards.

We have a comprehensive water-quality monitoring programme in place, which already tracks most of the contaminants covered by the new standards. Our monitoring shows the Paraparaumu WWTP discharge meets the required limits for all contaminants except total nitrogen (TN) and total suspended solids (TSS).

Under the new standards, any discharge that does not comply must include upgrades to meet compliance within five years. We already have a proposed upgrade programme that would significantly improve TN and TSS performance over that period and will ensure the treatment plant meets the new standards.

We’re currently assessing whether to continue with the existing application or withdraw it and reapply under the new standards. Once a decision has been made, we’ll update the community and explain what it means for the reconsenting process.

Find out about the Paraparaumu Wastewater Treatment Plant.

Background

The objectives of the project are to:

1. Upgrade and optimise the performance of the Paraparaumu wastewater treatment plant.
2. Work with our iwi partners and stakeholders to identify and implement environmental improvement options. Council is working in partnership with Ātiawa ki Whakarongotai, to investigate and pursue the best environmental and cultural outcomes for the continuous improvement of wastewater treatment and disposal at the Paraparaumu Wastewater Treatment Plant (including, but not limited to, the discharge of treated effluent to land).
3. Apply for resource consent enabling the continued operation of the wastewater treatment plant. 

 The Paraparaumu wastewater treatment plant has five existing consents authorising the discharges of:

• treated wastewater to the Mazengarb Drain
• contaminants to air from treatment plant facilities, associated with odour and operating a boiler
• screened wastewater to land from the base of the storage basin; in March 2024 the storage basin was expanded and lined with an impervious lining. The discharge of treated wastewater makes up a high proportion of the Mazengarb Stream’s flow, especially during dry summer month.

Process

Phase 1 – Upgrades and optimisation

Council implemented a significant improvement plan for the wastewater plant. Upgrades and optimisation activities include:

• a new aeration system to meet the requirement of maintaining dissolved oxygen in the treatment system
• lining and expanding the storage basin to cease discharges to land and provide more storage capacity for community growth and extreme weather events
• improving treatment capability within the treatment plant to improve discharge quality through reduced nutrient and bacteria concentrations
• ongoing rehabilitation of historical contaminated land on the treatment plant site
• planning for riparian planting along the Mazengarb Stream.

Phase 2 – Renewing resource consents

In December 2021, Council lodged an application with Greater Wellington (GW) to renew the resource consents held for the plant. GW agreed Council can continue to operate the plant until a decision is made on the application. GW has engaged a few technical specialists to review our consent application.

Council is seeking consent to continue to operate the existing plant with planned improvements over the next 15 years. Consent has been sought to discharge:

• treated wastewater to the Mazengarb Drain
• contaminants to air from treatment plant facilities
• screened wastewater during extreme wet weather when plant storage capacity is exceeded.

Lining and expansion of the storage basin has been completed, this means that discharges to land have now ceased, and no resource consent is required. While no future discharges of screened wastewater to the Mazengarb Stream are anticipated, resource consent is being sought to provide for any reasonably unanticipated weather events.

Community engagement

We have been working with our iwi partners and key stakeholders throughout the process. If you would like to know more about the treatment plant or the resource consent process, contact us.