By rosebell
Following that TBM Hiwa-i-te-Rangi broke into a shaft at Point Erin Reserve, Herne Bay, tunneling was completed on Auckland’s Central Interceptor.
In July 2021, TBM was commissioned from Māngere Wastewater Treatment Plant and has completed a 16.2km-long drive.
In order to building New Zealand’s longest wastewater tunnel, the 200m-long Herrenknecht TBM has travelled beneath Manukau Harbour, across the city and laid more than 10,000 rings. With a daily progress of almost 22m, she laid eight to 10 rings each day. With the aim of ensuring that the tunnel lasts 100 years, the concrete rings are coated with a plastic liner to protect against the corrosive effects of wastewater.
According to Chief programme delivery officer Shayne Cunis: “The breakthrough was a huge milestone and testament to the skills of the tunneling team provided by Ghella Abergeldie Joint Venture. The tunnellers have worked 24 hours per day, six days a week to build the tunnel. This is world class engineering, and it’s been completed safely, economically and on time, which is rare for any major infrastructure project. The TBM has been through 10 shafts, but breakthroughs never get old, and we’ll always remember this final one. I am incredibly proud of the 600 staff who’ve worked on this project. This is a very special day.”
“The Central Interceptor was the longest tunnel Ghella had built with a single TBM and it rated highly among other international infrastructure projects because of the technical complexities.We had a number of challenges to overcome, including crossing the Manukau Harbour and tunnelling just 15m below the seabed, as well as tunnelling 110m deep below the Hillsborough Ridge, Mount Roskill,” said Ghella Abergeldie project director Francesco Saibene.
He also added: “We did all this despite the Covid-19 pandemic, skills shortages of skills, hyperinflation and major storms. We are very proud of our team.”
Considering that Ghella has committed to staying in the country following the government’s recent infrastructure investment summit, it is the first that this company time has worked in New Zealand.
The date of removing TBM Hiwa-i-te-Rangi from the shaft will be in coming weeks and elsewhere, the tunnel is due to continue to be linked to the existing wastewater network.
Operating the the southern half of the tunnel from Blockhouse Bay south was done in previous month, whereas a new pump station at Māngere sends combined stormwater and wastewater flows from the tunnel to the treatment plant for processing.
The scheduled date for completing the NZ$1.6bn project and associated work in Herne Bay is 2028 and it is slated to decrease 80% of wet weather overflows into streams along the tunnel catchment and improve water quality at beaches. It will also cater for future urban growth and create a more resilient wastewater network.
