Our preferred solution for south-west’s future wastewater servicing

We are pursuing a new solution for the south-west area’s wastewater servicing that involves expanding and upgrading our two existing treatment plants at Clarks Beach and Waiuku.

Staff shared the preferred option for servicing the Clarks Beach, Waiuku and Glenbrook Beach communities, which includes an option to connect Kingseat, at a community meeting in Glenbrook last month.

Watercare head of wastewater planning Andrew Deutschle says a lot of work went into a comprehensive assessment of the options over the past 12 months.

“We’re going to be investing more than $500m in a new wastewater servicing scheme for the south-west communities that benefits the Manukau Harbour and enables the area to grow – so it was important to take the time to get it right.

“We looked at eight options, including three that involved a single wastewater treatment plant that would serve the wider area.

“But this option of upgrading and expanding our existing treatment plants at Clarks Beach and Waiuku takes advantage of the investment we’re already making to upgrade the Clarks Beach Wastewater Treatment Plant, better aligns with updated population projections, which are slower than what was previously anticipated, and reflects the feedback we received from the local communities.

“We expect these upgrades will lift the combined treatment capacity to serve a population of 20,000 initially, but this level of detail will be ironed out in the design phase.

“Our strategy will be to allow for staged upgrades at the plants, which spreads the cost so that we’re not over-investing up front.”

A new conveyance pipeline will carry treated wastewater from the Waiuku plant to Clarks Beach, where it will be discharged via the new outfall that’s currently under construction. The outfall and discharge were granted consent in 2018 and will serve the area over the long term.

An interim upgrade of the existing Waiuku Wastewater Treatment Plant will also be needed in the short-term to facilitate construction of the main plant, and maintain compliance with current consent standards while construction takes place. Design work on this is expected to start shortly.

An upgrade of the Clarks Beach Wastewater Treatment Plant is underway now, along with the treated wastewater outfall. The upgraded treatment plant and outfall will go into service in winter next year. Permanent storage for treated wastewater will be needed to ensure there is sufficient capacity to hold it until it can be discharged on the outgoing tides.

The exact timing for the permanent upgrades is dependent on design completion and receiving landowner approvals and the relevant consents. We will soon begin design and consenting for the construction work.

The construction phase is expected to take about three years.