Aucklanders to enjoy cleaner beaches and waterways with a new super-sized wastewater tunnel

On Thursday 14 March, Watercare and the Ghella Abergeldie Joint Venture will celebrate signing the contract to construct Watercare's Central Interceptor, a $1.2 billion wastewater tunnel with associated infrastructure. Construction will start with site works in August and the whole project is expected to be completed by 2025.
This 13-kilometre tunnel is a vital infrastructure project for Auckland and is part of our wider wastewater strategy to protect and enhance the natural environment.
Watercare’s chief executive, Raveen Jaduram, says that in older parts of central Auckland, wastewater and stormwater flow into a combined network of pipes. When it rains, stormwater overwhelms these pipes, which are designed to overflow into waterways.
“We want everyone to be able to enjoy clean waterways, beaches and estuaries – that’s why we’re building the Central Interceptor. It will run underground from Western Springs to the Māngere Wastewater Treatment, collecting wastewater along the way via link sewers and drop shafts.”
While the Central Interceptor is being built, we will deliver further projects in the area such as separating the stormwater and wastewater pipes. The largest of these projects is the Grey Lynn wastewater tunnel which is a two-kilometre extension of the Central Interceptor.
“We are delighted to announce that the Grey Lynn wastewater tunnel has been included in our construction contract with Ghella Abergeldie Joint Venture,” says Jaduram. “This is an extremely good outcome for Aucklanders because it means a better result for the environment without any extra cost for customers. Together, the Central Interceptor and our western isthmus projects will reduce overflows in the area by at least 80 per cent.”
We have a long history of delivering large-scale and complex projects. Back in 2005, we carried out the largest rehabilitation project in New Zealand’s history by removing the oxidation ponds from the Manukau Harbour and upgrading the Māngere Wastewater Treatment Plant to improve the quality of treated wastewater.

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More recently, we built a large wastewater tunnel that runs from Parnell to Ōrākei, referred to as Project Hobson, using the same tunnelling boring technique that will be employed for the Central Interceptor. This allowed the removal of an old sewer that bisected Hobson Bay and reduced overflows.
Jaduram says the Central Interceptor is our largest project to date: “Because it is a key part of our region-wide wastewater strategy, it was important to find the best company in the world to construct it. So after a vigorous tender process we chose Ghella Abergeldie Joint Venture with over 150 years’ experience working on major tunnelling and wastewater projects across the globe.”
New Zealand’s Ghella representative, Francesco Saibene, says:  “We have been very impressed with Watercare’s process. They kept to the intended timing, were clear with requirements and the evaluation process. Plus, the probity measures in place were very robust. One key factor was the extreme dedication and professionalism Watercare has demonstrated on the project. This was an ideal situation for our joint venture, which had an international component that needed those certainties.
“Of utmost importance for us is that Watercare has much the same values and vision as Ghella and Abergeldie, creating an environment where our joint venture can put the same amount of dedication and passion into this project, which will leave a long-lasting legacy to Auckland and its residents.”
Auckland mayor Phil Goff says, “The central interceptor will help improve Auckland’s water quality and clean-up our beaches by reducing waste water overflows in central Auckland.
“The central interceptor is one of the most significant infrastructure projects in our city. It will increase the capacity of our wastewater system to deal with population growth, help protect our environment and ensure Aucklanders can enjoy clean and healthy beaches for generations to come,” says Goff.
This project continues to meet its scheduled milestones and stay within budget.
We will fully fund the Central Interceptor using revenue from its water and wastewater service charges, infrastructure growth charges and borrowings. The project has been included in the Asset Management Plan since at least 2010 and is built into the price path. The Funding Plan projects price increases over the 10-year period to 2028 of:
  • an average of 2.5 per cent per year for water supply
  • an average of 3.3 per cent per year for wastewater services.
This represents an overall average annual price increase for combined water and wastewater of 3 per cent per year for a typical household.
We will not receive any money from Auckland Council towards this project. The council’s water quality targeted rate is being used to rehabilitate streams as well as address stormwater network and private septic tank issues.