By Lynda Myer
Considering the recent extreme weather events, including the heavy rain causing unprecedented flooding in Auckland in early February and last week’s Cyclone Gabrielle that have destroyed other regions of New Zealand, City Rail Link (CRL) has suffered minimal lasting impacts from these natural disasters.
After 11 lives fatality due to the cyclone, the government has just announced a NZ$300m (US$187m) recovery package.
According to Chief executive Dr Sean Sweeney: “At the CRL construction sites, extensive flood response planning stood the project in good stead to withstand both the flooding and the cyclone.”
Including dams erected in the Maungawhau/Mount Eden Station tunnels, additional measures for Cyclone Gabrielle was made by CRL and Link Alliance crisis management teams due to the advance cyclone warning. Moreover, installing extra bunds, pumps across all sites as well as moving plant and machinery to higher ground, were the other measures.
There have been no reports of significant flooding or wind-related incidents on any sites as a result of Cyclone Gabrielle.
In order to minimizing the impact on what is New Zealand’s largest transport infrastructure project, Dr Sweeney singled out the Link Alliance workers who worked through the Friday night before the heavy rain in early February.
“To maintain the highest standards of professionalism in the face of unprecedented flooding, while tunnels were being inundated, speaks to our people’s expertise and bravery,” said Dr Sweeney.
He also added: “At this stage there is no identified damage to infrastructure, permanent works or surrounding ground as a result of the flooding or the cyclone. This is a direct result of the detailed planning for events such as Auckland has unfortunately recently undergone – the professionalism and bravery of CRL and Link Alliance workers has been tested and found equal to the task.”
Considering that at city-bound cut-and-cover tunnel south of the Maungawhau/Mount Eden Station temporary portal, the storm partially flooded the works and a mobile crane and several elevated work platforms were inundated, it was the worst-affected site from the early February flooding.
“This area was pumped dry within 48 hours. Other than damage to a waterproofing layer behind a reinforced concrete wall, which we will replace, we haven’t identified any damage to the permanent works,” said Sweeney.
Elsewhere across the CRL, stormwater flowed from the inundated portal area in the city-bound tunnel northwards to the Karang-a-Hape Station. With the weir at the north end, this turned the entire station into a 100mm-deep reservoir.
Sweeney continued: “Our teams were able to move all but one item of plant to high ground and we were relatively unaffected, other than a general clean-up. The bottom of our temporary access shaft at Mercury Lane is lower than the platforms and ended up about 1000mm deep. Again, after pumping out, we identified no significant damage to the permanent works other than some blocked under-platform drainage that we are cleaning out.”
While the Te Waihoratiu Station (Aotea) was almost unaffected, due to a minor inflow down the tunnel, the stormwater entered Waitemata (Britomart) Station through a combination of openings in the roof at Te Waihorotiu and from the main Waitemata train portal at the eastern end.
“Our partner Link Alliance has been supporting Auckland Transport by supplying pumps and labour to remove stormwater from the existing station,” stated Sweeney.
The tunneling process of this project was completed in September 2022 by Link Alliance – comprising City Rail Link Ltd, Vinci Construction Grands Projets, Downer NZ, Soletanche Bachy International NZ, WSP NZ, Aecom New Zealand, and Tonkin + Taylor. CRL comprises a twin-tunnel with 3.45km length underground rail link up to 42m beneath Auckland city center.
