Today TBM Hiwa-i-te-Rangi broke through into a 30m-deep shaft in Western Springs after excavating 13km of the 16.2km Central Interceptor tunnel that will stretch from Māngere to Point Erin, Herne Bay in New Zealand’s largest city.
Chief programme delivery officer Shayne Cunis said the breakthrough had special significance for the whole Central Interceptor project team as Western Springs was the original end point for the tunnel.
“When the Central Interceptor construction contract with Ghella Abergeldie JV was signed in 2019, the tunnel was due to finish at Western Springs. Since then, it has twice been extended all the way to Point Erin. Everyone is to be congratulated on reaching this important milestone in a safe and timely manner. This is a complex engineering project being delivered to the highest standard and we’re another step closer to significantly improving water quality at Tāmaki Makaurau (Auckland) beaches and in waterways by reducing 80% of wet weather overflows,” said Cunis.
The TBM is currently lying 25m below ground just south of the Museum of Transport and Technology Auckland. Hiwa-i-te-Rangi began tunnelling in August 2021. Since then, she has crossed under the Manukau Harbour and passed through the 110m-deep Hillsborough Ridge – the deepest section of the route.
The 4.5m-diameter tunnel has a 1:1,000m gradient, so that wastewater will flow downhill by gravity all the way from central Auckland to Māngere Wastewater Treatment Plant for processing.
Ghella Abergeldie JV project director Francesco Saibene said the successful TBM breakthrough was testament to the skill and expertise of the tunnelling team.
“This is world-class engineering. Infrastructure tunnelling projects of this size and complexity are rare and we are very proud of our team and everything they have achieved,” he said.
“From here, we will continue to encounter favourable ground conditions, helping us to continue tunnelling north safely and efficiently to complete the tunnel by mid-2025.”
Elsewhere on the Central Interceptor project, construction of two link sewers that intersect the main tunnel has been completed. Testing is under way at the new Māngere Pump Station, which will send flows from the tunnel to the treatment plant and the tunnel is being connected to local wastewater networks along the tunnel route.
Preparations for excavation of a shaft at the Point Erin site are under way.
Section one of the tunnel will be ready for operation by the end of the year.
The Central Interceptor project is scheduled for completion in 2026.
