On March 14 Watercare, owned by the Auckland City Council, and the Ghella Abergeldie Joint Venture, signed the contract to construct Watercare’s Central Interceptor, a $1.2 billion wastewater tunnel with associated infrastructure.
Construction of Watercare’s Central Interceptor will start with site works in August and the project is expected to be completed by 2025.
This 13-kilometre tunnel is a vital infrastructure project for Auckland and is part of Watercare’s wider wastewater long-term infrastructure strategy.
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, and a mix of wastewater and stormwater can flood urbans streets.
“The Central Interceptor will run underground from Western Springs to the Mangere Wastewater Treatment, collecting wastewater along the way via link sewers and drop shafts.”
While the Central Interceptor is being built, Watercare 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.
“The Grey Lynn wastewater tunnel has been included in our construction contract with Ghella Abergeldie Joint Venture,” says Jaduram.
“Together, the Central Interceptor and our western isthmus projects will reduce overflows in the area by at least 80 per cent.”
Back in 2005, the company carried out the largest rehabilitation project in our history by removing the oxidation ponds from the Manukau Harbour and upgrading the Mangere Wastewater Treatment Plant to improve the quality of treated wastewater.
More recently, Watercare built a large wastewater tunnel that runs from Parnell to Orakei, 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 Watercare’s 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.”
Watercare will fully-fund the Central Interceptor using revenue from its water and wastewater service charges on Auckland’s residents and businesses, 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 percent per year for water supply and an average of 3.3 percent per year for wastewater services.
This represents an overall average annual price increase for combined water and wastewater of three percent per year for a typical household.
As Watercare operates on a self-funded model, it doesn’t receive any money from Auckland Council towards this project.