The City Rail Link has reported that Cyclone Gabrielle and the earlier Auckland Anniversary flooding event have left minimal lasting impacts on the 3.45km long, $4.42bn twin tunnel project. At the CRL construction sites, extensive flood response planning stood the project in good stead to withstand both the flooding and the cyclone, says project Chief executive Dr Sean Sweeney
The advance cyclone warning allowed CRL and Link Alliance crisis management teams to install additional measures for Cyclone Gabrielle, including dams erected in the Maungawhau/Mount Eden Station tunnels, he says. Other measures included installation of extra bunds, pumps across all sites and the removal of plant and machinery to higher ground.
There have been no reports of any significant flooding or wind related incidents across any sites as a result of Cyclone Gabrielle.
Dr Sweeney singled out the Link Alliance workers who worked through the Friday night of Anniversary Weekend to ensure there was little damage and disruption to New Zealand’s largest transport infrastructure project
“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,” he says
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,” Dr Sweeney says.
The worst-affected site from Auckland Anniversary flooding was the city-bound cut-and-cover tunnel immediately south of the Maungawhau/Mount Eden Station temporary portal. The storm partially flooded these works and a mobile crane and several Elevated Work Platforms (EWPs) were inundated.
“This area was pumped dry within 48 hours and the good news is that 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 at this stage,” Dr Sweeney says.
Elsewhere across the CRL, stormwater flowed from the inundated portal area in the city bound tunnel northwards to the Karang-a-Hape Station (Karangahape). With the weir at the north end, this turned the entire station into a 100mm-deep reservoir.
“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,” notes Dr Sweeney. “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 currently cleaning out.”
Dr Sweeney says Te Waihoratiu Station (Aotea) was relatively unaffected with a minor inflow down the tunnel but stormwater did make its way to 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, nearest Vector Arena.
“Our partner Link Alliance has been supporting Auckland Transport by supplying pumps and labour to remove stormwater from the existing station,” he says.
The City Rail Link (CRL) is New Zealand’s largest ever transport infrastructure project, involving construction of a 3.45km twin-tunnel underground rail link up to 42m below the Auckland city centre.
The Link Alliance, delivering the main CRL works – the stations and tunnels comprises (Vinci Construction Grands Projets S.A.S., Downer NZ Ltd, Soletanche Bachy International NZ Limited, WSP Opus (NZ) Limited, AECOM New Zealand Limited and Tonkin + Taylor Limited). City Rail Link and the Link Alliance negotiated a $75M Early Works Contract.