Our Central Interceptor project completes tunnelling for first link sewer

CI tunneller Sam Stirrat celebrates the completion
Image: Central Interceptor tunneller Sam Stirrat celebrates breaking through to complete the first link sewer for the project

She’s done it! Domenica, a micro-Tunnel Boring Machine (m-TBM) has broken through for the last time to complete Link Sewer C—the first of two connecting sewers to our main Central Interceptor tunnel.
The 2.6m diameter cutterhead chewed through the concrete wall of a 13m deep shaft at Miranda St, Avondale just before 10.00am today (24 March), to loud cheers from assembled construction crew. Domenica was launched in June 2021 and has completed four shaft breakthroughs along the 3.2km link sewer tunnel route, which runs from May Rd, Mt Roskill to Avondale. The tunnel will significantly reduce wet-weather overflows by taking stormwater and wastewater to Māngere treatment plant for processing.
Our Central Interceptor commercial manager, Nigel Varcoe says the milestone, which was achieved four weeks early is one to savour: “This is a big moment for all the team.
“We’ve been through a lot: a global pandemic, closed borders and more recently floods. To have the first link sewer tunnel completed safely and ahead of schedule is a great achievement and I’d like to pay a particular tribute to the Ghella Abergeldie JV tunnellers who have worked so efficiently to get the job done.”
A crew of 15 people, working above and below ground operates Domenica, which uses a pipe-jacking method of construction, whereby the entire tunnel is pushed along by thrusters set against a wall. Hynds Pipe Systems manufacture the steel re-enforced concrete tunnel segments at their Pokeno factory. Domenica has been laying around four to five pipes per day on average and traveling up to 15m, five days per week.

CI celebrates completion of first link sewer
Image: Central Interceptor construction crews celebrate completion of first link sewer
Chris McCarthny, our surface & permanent works delivery manager says the link sewer team have every right to call themselves the ‘A team’: “In November, Domenica completed the longest drive of the project (1212m) from Dundale Ave, Blockhouse Bay to Miranda Reserve. Not only was it a very long continuous drive, but the tunnel was also curved, which was technically challenging.
“The long drive was necessary because a design change removed the need for another shaft at Whitney St, which would have caused months of disruption for Blockhouse Bay residents, so we’re very grateful to the team for pulling this off.”  
Domenica will now be removed for refurbishment before starting work on link sewer B in late July, which will run from a shaft near Rocket Park, Mt Albert to Rawalpindi St, Mt Albert (just over 1km) and will involve two separate drives.
Meanwhile, Hiwa-i-te-Rangi—the Central Interceptor’s main TBM has just completed a 5km milestone and is currently underneath Hillsborough Ridge as she travels on her 14.7km journey towards central Auckland.  Link sewer C will connect with the main Central Interceptor tunnel at a shaft in May Rd, Mt Roskill, while link sewer B will intersect at the Rocket Park, Mt Albert shaft.

To find out more information, watch our video here.