Central Interceptor tunnelling team celebrates first ‘breakthrough’

Photo of our micro tunnel boring machine breaking through at Haycock Avenue
Photo: The Central Interceptor team celebrates micro-TBM Domenica’s successful first breakthrough.

Our $1.2b Central Interceptor tunnelling project has reached an exciting milestone today as the micro-Tunnel Boring Machine ‘Domenica’ finished her first drive, breaking through to the Haycock Avenue shaft in Mt Roskill.
The mTBM has been laying the 2.1-metre-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. When it’s finished in 2026, the Central Interceptor will store and transport both stormwater and wastewater to our Māngere Wastewater Treatment Plant, preventing wet-weather overflows and significantly cleaning up Auckland’s waterways.
Chris McCarthny, delivery manager for the Central Interceptor’s link sewers, says it’s been a “rocky road” for Domenica in more ways than the obvious.
“We started tunnelling from our 55-metre-deep May Rd shaft on this first section of the link sewer in June. 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 stopped for just one day as Auckland entered Alert Level 4 in August, before the project received a crucial exemption to allow a minimal number of staff to continue tunnelling under strict Covid-19 protocols.
“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. When we entered lockdown Domenica was in almost the worst possible position – more than 70m 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,” McCarthny says.
“For the rest of alert level 4, we used a skeleton crew to keep Domenica inching 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.”
The Central Interceptor team is thrilled to have completed the first of many breakthroughs on the five-year tunnelling project.
“Everyone on site is really excited to have reached this significant milestone in time for Christmas, and they’re definitely looking forward to a holiday," Central Interceptor executive programme director Shayne Cunis says.
“I’d like to thank the Ghella-Abergeldie Joint Venture and their team for their hard work over a very tough few months, not to mention their families who’ve supported them in lockdown while they do the mahi on this groundbreaking project.”
The mTBM will now be retrieved from the shaft at the Haycock site, for a thorough service, before she’s launched again next year at the Dundale Ave site in Blockhouse Bay where she will start the 720-metre journey back to Haycock Ave.
Meanwhile Hiwa-i-te-Rangi, the Central Interceptor’s main Tunnel Boring Machine that was launched in July, has laid more than 145 rings and travelled more than 240m of her 14.7km journey from the Māngere Wastewater Treatment Plant to Grey Lynn. She’s expected to start tunnelling deep beneath the Manukau Harbour in winter next year.