Tunnel Boring Machine breaks through for final time to complete two link sewers


A big crunch and she was there. Domenica, a micro-Tunnel Boring Machine broke through a concrete shaft wall at a Central Interceptor project construction site for the last time today to complete the second of two link sewers, marking another major milestone in New Zealand’s billion-dollar wastewater infrastructure project.
The 2.8m diameter cutterhead broke through a concrete shaft wall at the Norgrove Ave, Mt Albert site at 10.00am to loud cheers from assembled construction crews, who watched the breakthrough live via a large screen. Link Sewer B is just over one kilometre long and intersects the main Central Interceptor tunnel at a Mt Albert War Memorial site. Together with Link Sewer C, which joins the main tunnel at May Rd, the link sewers will collect combined wastewater and stormwater flows from West Auckland, sending them to Māngere Wastewater Treatment Plant for processing, instead of discharging into streams and beaches during heavy rain.
Central Interceptor Chief Programme Delivery Officer Shayne Cunis paid tribute to construction partners Ghella Abergeldie JV’s crew: “The micro-tunnelling teams, together with our own Watercare engineers have consistently performed above expectations. They have completed more than four kilometres of tunnelling safely and expertly, including a particularly long challenging single drive, with a lefthand bend.
They can be proud of all their hard work and for leaving an incredible legacy of cleaner waterways for the people of Tāmaki Makaurau.”

Map of the Central Interceptor link sewers

Clink here for an enlarged map

Francesco Saibene, Ghella Abergeldie JV Project Director says the multi-national crews completed the work despite constraints following a global pandemic and extreme weather events: “I am very proud of our crews, some of whom didn’t see their families for two years when borders were closed. Tunnelling is an unusual job and you have to really pull together to work effectively. And that’s what our people have done, since Domenica was first launched back in June 2021.” 
Domenica is one of three Tunnel Boring Machines (TBM) working on the Central Interceptor project. Victoria, a 12m long micro-tunnelling TBM is connecting the main tunnel to the local wastewater network in Keith Hay Park, Mt Roskill. Whilst Hiwa-i-te-Rangi (almost 200m long) is currently 70m deep underground as she travels under Sandringham on her way to Pt Erin, Herne Bay as she builds the 16.2km long tunnel.  
Domenica will be removed from the shaft in coming days, along with pipe-jacking equipment and other services. Teams of welders will carry out thermal welding on joins in the tunnel’s plastic liner, which protects against the corrosive effects of wastewater, helping to ensure a 100-year lifespan.
A section of the Central Interceptor tunnel (plus link sewers) will go live before the end of the year. The project is due for completion in 2026.