Manukau Harbour Water Issues

The resource consent for the new outfall from the Watercare wastewater treatment plant, which was issued finally in 2018, requires that Watercare establishes a Community Liaison Group to provide opportunity for community engagement with the project. The first meeting of the group was held on November 17th.

Key issues that emerged from the meeting were:

  • The expectation is that the outfall in the Waiuku Channel, offshore from Clarks Beach Golf Club, will still be used, and the conditions upon which consent was granted will be met. But the architecture of the system (originally planned to pipe wastewater from Clarks Beach and Kingseat to Waiuku for treatment, then piping of the treated water back to the outfall) might not proceed as had been assumed earlier. The whole project is delayed at present due to uncertainty of funding; but inevitably enhanced treatment capacity will be needed because the present facilities will become overloaded. The resource consent lapses in 2026, so there will definitely be a new system in place by then.
  • Watercare commissioned a hydrodynamic model of the harbor from NIWA in 2016, with expected delivery in 2019. It still has not been delivered. Most of the model (the parts that address nutrients, salinity etc.) appears to work, but not the part which predicts where algal blooms are expected to arise, and this is throwing doubt on the whole model’s accuracy. Watercare hope to take possession of the still-incomplete model before Christmas 2020, with NIWA expected to still get it refined so that it works fully. This should allow modeling of the gross effects of changing how emissions to the harbour will affect conditions. It is planned to be integrated with a further model being developed by Auckland Council Healthy Waters for the land-derived inputs to the harbor, which will refine the inputs for the hydrodynamic model further, but this may be another two years away.
  • Conditions of the resource consent include installation of a rain gauge at Clarks Beach, which the meeting urged Watercare representatives to do sooner rather than later, and enhanced water quality testing up- and down-stream of the outfall. The meeting urged Watercare, despite their reservations that the system is more difficult to make effective in salt water, to use monitoring buoys such as is already installed in the Tamaki River to achieve this task, because they deliver continuous real-time information.

It was a pleasure to see the openness of Dr Nathaniel Wilson, Watercare Environmental Care Manager, who convened the meeting and was prepared to address every question that was put to him. Meetings of this Liaison Group are expected to take place every six months, and we will try to attend and keep the community informed of the outcomes.  Matters that should be progressed before the next meeting include the timetable for planning/construction of the new system, and the plans for ‘baseline monitoring’ which the Environment Court requires to commence at least two years before the outfall is brought into operation.

John Duncan