Elected Members agreed to commence the first two stages of a multi-year project to increase the capacity of the Mangawhai Wastewater Scheme.

Stages one and two of the Mangawhai Community Wastewater Scheme (MWWS) – revised Master Plan Strategy will allow for more connections to the Mangawhai Wastewater Treatment Plant, which would otherwise reach capacity next year, and will kickstart steps to diversify how the town's treated wastewater is dispersed.

Kaipara Mayor Craig Jepson says Mangawhai’s population is rapidly growing, and it is essential that the wastewater scheme can accommodate this.

“We need to stay ahead of the game and have the wastewater system ready to come onstream when it is needed,” says Mayor Jepson.

Stage one consists of further optimising the Mangawhai Wastewater Plant’s performance with the design and implementation of an inDENSE system, increasing the plant’s capacity by 550 to 3,550 connections. This increase will cater for projected growth in Mangawhai to at least 2030, depending on the rate of the growth.

Kaipara District Council General Manager of Infrastructure Services, Anin Nama, says the current dispersal of treated wastewater at the Brown Road farm can be improved.

Treated wastewater from the plant currently flows some 13 kilometres to Kaipara District Council’s Brown Road farm effluent pond, where it is then irrigated onto paddocks. In stage two, Council will begin concept design and the resource consent process for a new irrigation system for the farm, including subsurface irrigation to specific areas of the Mangawhai Golf Course. Now that Council has approved stage two, discussions regarding the subsurface irrigation can continue with the Management of the Golf Club.

“In the future, the farm irrigation system will be reduced, with the majority of treated wastewater flowing a short distance over the hill to Mangawhai Golf Club,” says Anin.

“The current spraying operation at the Brown Road farm will be replaced with either a wetland system or subsurface irrigation. This plan was informed by an investigation into farm operations earlier this year.”

As of today, the farm’s capacity can only service new connections to the wastewater scheme up until 2026.

A sum of $1.8m was provided in the 2021-2031 Long Term Plan and this sum was increased to $2.3m in the 2022/23 Annual Plan. The unspent balance of $1.96m has been carried through into the 2023/24 capital budget and available for the stage one and two works. Stages one and two of the MWWS – revised Master

Plan Strategy will be undertaken by Kaipara District Council, prior to the planned transfer of assets to Wai Tāmaki ki Te Hiku, Auckland and Northland’s new water entity, as of 01 July 2024.

There are a further three stages to the revised Master Plan Strategy, which will be carried out by the water entity once it goes live next year. Council is working with it on handover of our asset management plan going forward.

About the Mangawhai Community Wastewater Scheme – Master Plan Strategy

The Mangawhai Community Wastewater Scheme (MWWS) – Master Plan Strategy sets out a plan for upgrades to Mangawhai’s wastewater network to meet the needs of the town for the next 30 years.

MWWS – Master Plan Strategy considers growth projections, peak flows, and the impact of extreme wet weather events on the network.

After its initial presentation to Council in February 2022, the Mangawhai Advisory Group (MAG) was established to provide advice on further refinement of the strategy. The MAG met monthly, until its last meeting in September 2022.

The Master Plan Strategy, including all five stages, was presented to elected members at the December 2022 Council Briefing at a cost of $90.5 million. At the time, staff advised Council that given the significant investment, an independent peer review to assess the strategy and conduct a value engineering assessment had been commissioned. The peer review by leading experts resulted in a revised solution at a cost of $72 million.

View the Council Meeting discussion and decision on the Kaipara District Council YouTube channel (1:35:56 minutes in).