Microtunnelling, New Zealand, News, Wastewater

Central Interceptor celebrates breakthrough

Micro-tunnel boring machine (mTBM) ‘Domenica’ has finished its first drive, successfully breaking through at the Haycock Ave shaft on 10 December.   

Domenica was placed in a 2.1 m diameter pipe for the link sewer that will run between Miranda Reserve in Avondale to the main Central Interceptor wastewater tunnel, connecting up at May Rd in Mt Roskill. 

Once complete in 2026, the Central Interceptor will store and transport both stormwater and wastewater to Watercare’s Māngere Wastewater Treatment Plant, preventing wet-weather overflows and significantly cleaning up Auckland’s waterways.

Watercare delivery manager Chris McCarthny said the process has not been the post seamless for the team. 

“We started tunnelling from our 55 m deep May Rd shaft on this first section of the link sewer in June,” said McCarthny. 

“Domenica was making great progress, working 24 hours a day, five days a week and laying up to 15 metres of pipe a day. And then Covid-19 threw a spanner in the works.”

Work was placed on hold for one day as Auckland entered alert level 4 in August before the project received a crucial exemption.

“With this method of tunnelling called pipejacking, where the micro-TBM and all of the pipes are pushed along from the base of the launch shaft, the machine can get stuck if it sits stationary for too long,” McCarthny explained.

“When we entered lockdown, Domenica was in almost the worst possible position – more than 70 m below the ground and in the middle of residential Mt Roskill – so it was critical to get her up and running again so she didn’t get stuck.” 

The Central Interceptor project operated under a skeleton crew during level 4 restrictions to keep the mTBM moving forward, covering just half a metre a day. 

“Thanks to the incredible people on the project, we were able to implement our level 4 protocols within 48 hours of the announcement and continue tunnelling, avoiding the potentially disastrous consequences of a stuck machine.”

This is the first of many anticipated breakthroughs on the five-year tunnelling project, and according to executive program director Shayne Cunis, the team is pleased to have completed the milestone ahead of Christmas. 

The mTBM will now be retrieved from the shaft at the Haycock site and serviced before it is launched again next year. 

From there, ‘Domenica’ will begin a 720 m journey back to Haycock Ave from the Dundale Ave site in Blockhouse Bay. 

Meanwhile, the Central Interceptor’s main mTBM ‘Hiwa-i-te-Rangi’ launched back in July has laid more than 145 rings and traveled more than 240 m of its 14.7 km journey. 

Hiwa-i-te-Rangi is expected to start tunnelling deep beneath the Manukau Harbour in winter next year.

For more information visit the Watercare website. 


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