Central Interceptor micro-Tunnel Boring Machine (m-TBM) finishes second drive

She’s done it again! Domenica - the Central Interceptor’s micro-Tunnel Boring Machine has broken through to the Haycock Avenue shaft, Mt Roskill after travelling 715m from Dundale Avenue.
 
It’s the second and shortest drive so far, since Domenica began her journey in July last year as she lays a 2.1m branch sewer pipe to connect to our giant wastewater tunnel, the Central Interceptor. Water and spoil gushed as Domenica broke-through, directly on target. The project is being delivered by Ghella Abergeldie (GAJV) and will significantly reduce wet weather wastewater overflows into central Auckland waterways when it’s completed in 2026.
 
There were loud cheers from crews, who gathered around the shaft and watched a live stream of the breakthrough operation happening 30m below ground. 
 
Executive programme director Shayne Cunis says the drive was completed efficiently, safely and ahead of schedule: “The tunnelling crew learnt a lot from the first drive and achieved breakthrough almost a month ahead of schedule.
 
“At one point, Domenica was tunnelling 22m and laying seven pipe rings per day - which is 25 percent faster than our first drive.”
 
One of the innovations seen this time, was the use of “double skips” which meant twice as much spoil could be removed from the shaft.
 
Domenica will now be lifted out of the shaft and refurbished before being dropped into the Dundale Avenue shaft to begin tunnelling again to Miranda Reserve, Avondale— just under 1.2km away. This will be the longest m-TBM drive on the project and is likely to be one of the longest single drives by a m-TBM in New Zealand. 
  
Meanwhile the 5.4 diameter Tunnel Boring Machine (TBM) called Hiwa-i-te-Rangi began digging the 14.7km long main tunnel in August from a site next to our Māngere Wastewater Treatment Plant.
 
COVID-19 caused minor delays in March but since then, the machine has been making good progress, travelling around 16m, and installing six to eight tunnel segment rings per day.  The TBM is currently 35m underneath Ambury Regional Park and is due to begin crossing the Manukau Harbour in August, before reaching Grey Lynn in 2026.