A survey of the harbour floor between Katikati and Matakana Island is underway as Western Bay of Plenty District Council investigates long-term options for managing treated wastewater from Katikati.
Over the next two weeks, specialist contractors will assess ground conditions beneath the harbour as part of investigations for the design and construction of a potential replacement of the existing pipeline across the harbour, one of the future wastewater disposal options currently being explored for the area.
The work is part of Council’s Katikati Wastewater Disposal Future Directions project – a collaborative effort, guided by a Project Control Group and Te Ohu Waiora, a group consisting of representatives from tāngata whenua, Council, and external stakeholders.
Council’s Director of Water Services, Coral-Lee Ertel said the investigations are an important step in planning for the future.
“We’re focused on implementing a sustainable, long-term and culturally acceptable solution that protects our harbour, meets new wastewater standards, and reflects the values of our community and tangata whenua,” said Ms Ertel.
The Katikati Wastewater Treatment Plant currently discharges treated wastewater through an ocean outfall pipeline that extends across Tauranga Harbour, through Matakana Island, and out to sea. The ageing pipeline within the harbour has experienced several breaks over the past year, highlighting the need for a long-term replacement strategy. The plant’s current discharge consent expires in 2038, and Council is required to confirm its preferred future direction by the end of 2026.
Following completion of the Future Directions Report in 2025, the preferred long term approach sees the retention of an ocean discharge, but with higher treatment standards and a longer outfall pipe. Council also identified the early replacement of the ageing harbour crossing section of the outfall pipeline as a priority project.
The current investigations relate specifically to the option of replacing the harbour crossing section of the pipeline. The information gathered through the survey will help determine whether ground conditions are suitable for installing a replacement pipeline, support design of a replacement pipeline, and inform future resource consent applications for the works.
Following a procurement process, Brown Bros Drilling was selected by Council as the most suitable specialist contractor to carry out the survey.
The survey comprises of 14 investigation sites located along the proposed replacement pipeline route, which is just to the north of the existing pipeline location. At each site, crews will collect sediment and soil samples from beneath the harbour floor and undertake specialised testing to measure the strength and stability of the ground to depths of up to 15 metres.
At five of the investigation sites, sediment samples will also be collected and tested for the presence of environmental contaminants as part of the ecological assessment.
The investigations are expected to take up to two weeks to complete, depending on weather and tidal conditions. No disruption to residents or harbour users is anticipated.
“With the current outfall pipeline nearing the end of its operational life and experiencing multiple leaks, we’re working to address both the current infrastructure issues and future regulatory requirements,” said Ms Ertel.
“Understanding the ecological conditions and the nature of the harbour floor is essential, and the results from this survey will help us determine the best construction method to ensure a replacement pipeline can be safely and responsibly constructed, if that becomes the preferred solution.”
Council says the community will have an opportunity to provide feedback on the proposed wastewater disposal solution, once all technical and environmental assessments are completed.
For more information on the Katikati Wastewater Disposal Future Directions Project, visit: https://yourplace.westernbay.govt.nz/katikati-wastewater-disposal.
