Micro-tunnelling completed on NZ water project

The 2.8m diameter micro-TBM Domenica broke through today into the nearly 30m-deep Norgrove Avenue shaft after completing the last 300m of Link Sewer B in New Zealand’s largest city.

Link Sewer B is 1100m long, stretching from Mt Albert War Memorial Park to Rawalpindi Reserve.

Tunnelling on the 3.2km Link Sewer C was completed in March last year.

The link sewers will collect combined wastewater and stormwater flows from West Auckland, sending them to Mangere 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 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 4km of tunnelling safely and expertly, including a particularly long challenging single drive, with a lefthand bend,” he said.

Ghella Abergeldie JV project director Francesco Saibene said the multi-national crews completed the work despite constraints during the Covid pandemic and extreme weather.

“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. That’s what our people have done, since Domenica was first launched back in June 2021,” he said. 
 
Domenica is one of three TBMs working on the Central Interceptor project. Victoria, a 12m-long micro-tunnelling TBM is connecting the main tunnel to the local wastewater network in Mt Roskill. The nearly 200m-long TBM Hiwa-i-te-Rangi 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 main tunnel.  
 
Domenica will be removed from the shaft in the 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.

The Central Interceptor project is the largest wastewater infrastructure undertaken in New Zealand history. It will store 226,000m3 of wastewater, control the flows into treatment plants and reduce the number of wastewater overflows into Auckland’s waterways and the Waitemata Harbour.  
 
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.