City Rail Link (CRL) is Auckland’s first underground rail line and the largest transport infrastructure project ever undertaken in New Zealand. CRL will transform the downtown Britomart Transport Centre into a two-way through-station, doubling the capacity, reducing travel times and supporting a growing population with a world-class transit system.
The 3.45km twin tunnel underground rail link will run up to 42m below the city centre and includes the construction of two new inner-city underground stations (Karangahape and Aotea) and rebuilding the existing Mt. Eden Station. Construction of the stations and tunnels is through cut-and-cover and tunnel boring machine (TBM) methodologies, except for Karangahape Station (K-Road) which is being excavated by roadheaders due to its layout and dimensions.
The main construction contract for the stations and tunnels was awarded to The Link Alliance Joint Venture, comprised of Vinci Construction Grands Projects S.A.S, Downer NZ Ltd, Soletanche Bachy International NZ Limited, WSP Opus (NZ) Limited, AECOM New Zealand Limited, Tonkin+Taylor Limited and CRL Ltd.
Ventilation and dust control are needed to keep workers’ exposure to fumes and dust at safe, acceptable levels. Grydale provided ventilation design consulting to develop an extract ventilation system for the excavation of K-Road Station and supplied a JMS-60-MES dust collector and a 50m3/s axial fan to complete this work.
K-Road will have two entrances, one at Mercury Lane and one in the center of Beresford Square. The excavation of K-Road, which is the deepest of the CRL stations at 32m below the surface. The station is being excavated by two roadheaders because the Karangahape tunnel needs to be larger than the TBM to accommodate four underground station platforms which will be 150m long, suitable for nine train cars to increase capacity from the current six. The platform tunnels are maximum 8.9m high and 9.8m wide with an area of 80.2m2.