NEW ZEALAND: Extensive flood response planning at construction sites has enabled Auckland’s City Rail Link project to withstand Cyclone Gabrielle and the earlier Auckland Anniversary with minimal lasting impacts, project promoter CRL Ltd reports.
CEO Dr Sean Sweeney said the advance cyclone warning allowed CRL and construction consortium the Link Alliance to install additional measures for Cyclone Gabrielle in mid-February, including dams in the Maungawhau/Mount Eden Station tunnels. Other measures included installation of extra bunds, pumps across all sites and the removal of plant and machinery to higher ground.
As a result, there was no significant flooding or wind related incidents across any sites as a result of Cyclone Gabrielle, and there is no identified damage to infrastructure, permanent works or surrounding ground.
However, the Auckland Anniversary flooding in late January and early February caused problems. The worst-affected site was the city-bound cut-and-cover tunnel immediately south of the Maungawhau/Mount Eden Station temporary portal, where the storm partially flooded the works and a mobile crane and several elevated work platforms were inundated.
‘This area was pumped dry within 48 h 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’, said Sweeney.
Elsewhere across the project sites, stormwater flowed from the inundated portal area in the city bound tunnel northwards to the Karang-a-Hape station, which was flooded 100 mm deep.
‘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’, said Sweeney. ’The bottom of our temporary access shaft at Mercury Lane is lower than the platforms and ended up about 1 000 mm 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.’
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 portal at the eastern end.
