Paraparaumu wastewater treatment plant consenting
We’re working through a process of improvements and consenting issues for the Paraparaumu Wastewater Treatment Plant to ensure it can meet changing public health and environmental standards and community expectations for the next 15 years.
Waikanae, Paraparaumu and Raumati are served by a single wastewater treatment plant, located in Fytfield Place, Paraparaumu. The plant was commissioned in 1981 and upgraded in 2001/02. At the same time, the oxidation ponds (now Pharazyn Reserve) in Waikanae were closed, and all Waikanae wastewater is now pumped to Paraparaumu for treatment.
The Paraparaumu Wastewater Treatment Plant uses biological nutrient removal, one of the most advanced treatment processes in New Zealand. It treats approximately 10-to-12 million litres of wastewater daily to a high standard to protect human and environmental health.
Treated wastewater is discharged to the Mazengarb Drain, which drains to the Lindale/Mazengarb Stream and then to the Waikanae Estuary. During times of low rainfall treated wastewater makes up most of the downstream flow.
Find out about the Paraparaumu Wastewater Treatment Plant.
Background
The objectives of the project are to:
- Ensure the performance of the Paraparaumu wastewater treatment plant and treated wastewater meets the existing resource consent, public health and environmental standards and limits.
- Work with our iwi partners and stakeholders to consider and evaluate a range of treatment and disposal options and decide on the best practicable long-term option/s.
- Apply for resource consent for the best practicable option (BPO).
The Paraparaumu wastewater treatment plant has five existing consents covering discharges to:
- air, associated with plant odours and operating a boiler
- land, via an unlined storage basin used to store untreated wastewater in wet weather when unusually high amounts of wastewater reach the plant (this occurs approximately two or three times a year)
- the Mazengarb Stream (this discharge makes up a high proportion of the stream’s flow).
This project will identify the best long-term solution for the plant and its discharges. Laws and standards, and community views about the environment, have all changed since the last consents were granted. Combined with population growth and higher standards, our current treatment method will not meet future requirements.
Process
Phase 1 – Renewing the Resource Consent
In December 2021, Council lodged an application with Greater Wellington Regional Council (GWRC) to renew the resource consents held for the plant. GWRC agreed that Council can continue to operate the plant until a decision is made on the application. GWRC 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 (18,600 m3/day) to the Mazengarb Drain through the Rakahore channel (an open channel filled with rocks) to help cleanse it before it’s discharge into the existing drain
- discharge contaminants to air from treatment plant facilities
- increase the overflow pond capacity and install an impermeable liner
- discharge screened wastewater during extreme wet weather when plant storage capacity is exceeded.
Phase 2 – Planning for the future
Phase 2 of the project will investigate the long-term needs of the community.
Council will work with our iwi partners and stakeholders to consider a range of treatment and disposal options and then evaluate them within a criteria framework which includes regulatory limits and standards, future community needs and cultural, environmental, and economic values.
The scoring criteria for this matrix will be developed in partnership with iwi partners and stakeholders.
Outputs of the project include a proposed improvement plan for treatment and discharge options within the existing facility, ie lifecycle capex and opex costs for 30 years, and the consideration of an option to identify a new WWTP site.
Phase 3 – Resource consent for the BPO
The identified BPO for the WwTP might require a change to the existing resource consents or an application for new resource consents. Phase 3 of the project will involve preparing and lodging any required resource consent applications that will enable Council to implement the BPO.
Options
The longlist of options to discharge treated wastewater includes combinations of the following (to be consulted with mana whenua/ Te Ātiawa).
Surface water discharge options
- No change (discharge via the Mazengarb Drain to the Waikanae Estuary).
Higher level of treatment (discharge to the Mazengarb Drain through the Rakahore channel (an open channel filled with rocks) which help cleanse it before it’s discharged into the existing drain). - Existing level of treatment (discharge to Waikanae River).
- Split discharge to surface water (combination of discharge to the Mazengarb Drain and Waikanae River).
Ocean discharge options
- Discharge south of Marine Reserve.
- Discharge north of Marine Reserve.
- Long outfall with outlet beyond Kāpiti Island.
- Most to coastal marine area, some to land.
- Discharge to coastal marine area, with lower treatment.
Land application options
- Discharge to land near coast.
- Discharge to land in inland areas.
- Part of discharge to inland with peak discharge to sea.
- Part of discharge to inland and Mazengarb Stream
- Part of discharge to inland and Waikanae River.
Groundwater/water supply network options
- Discharge to shallow aquifer.
- Bore injection into Waimea/Parata aquifers.
- Bore injection into deep aquifers near Raumati.
- Discharge to Waikanae River downriver of water supply intake.
Community engagement
We'll be working with our iwi partners and key stakeholders throughout the process. We'll engage with neighbours of the wastewater treatment plant in the early stages of the project, and with our district-wide community on the shortlist of options when it has been identified.