Valued at NZ$1.4-billion, the largest road infrastructure development project in New Zealand’s history, the Waterview Connection, in Auckland, is due for completion in 2017; it is one of the most important infrastructure developments to take place in the country.

The project involves construction of 5 km of new motorway – half of it underground in twin tunnels – to complete the city’s long-planned Western Ring Route.

It will give the region the “connected and resilient strategic” road transport system it needs to underpin economic growth and sustainable development. It will also provide a direct motorway link between Auckland’s central business district and international airport.

Completion of the Western Ring Route has been prioritised by the New Zealand government as critical to the country’s future economic prosperity.

It is one of seven Roads of National Significance, which together represent the largest investment ever in road transport in New Zealand. The projects will ease the most significant pressure points in the national network, reduce congestion in and around the five largest metropolitan areas, improve road safety and link major sea and air ports more effectively into the State highway network.

The Waterview Connection project is being delivered for the NZ Transport Agency by the Well-Connected Alliance, comprising Aveng Group’s McConnell Dowell, Fletcher Construction, Parsons Brinckerhoff NZ, Beca Infrastructure, Tonkin & Taylor, Japanese construction company Obayashi Corporation and the Transport Agency. The alliance is using the world’s tenth-biggest tunnel boring machine (TBM), called Alice, to construct the 2.4 km twin tunnels at the centre of the project.

The alliance’s decision to use this machine was made following multicriteria analysis, which concluded that this method best addressed the project’s geotechnical risks and uncertainties, while decreasing cost and programme risk. Criteria considered during this evaluation were safety, cost, the programme, risk/opportunity, construction sequence and environmental sustainability.

Each tunnel comprises a single pass precast concrete segmental lining with an internal diameter of 13.1 m. The lining comprises two-metre-wide rings, 450 mm thick – each with a conventional configuration of nine interconnected segments and a smaller key segment.

Tunnelling began in November last year – cautiously at first to ensure that the machine’s capability and systems were well tested and its crews were totally familiar with its workings. By June this year, the first kilometre of tunnel had been constructed and the completion of the first of the two tunnels was being planned for late September. Planning was also well advanced for the machine’s turnaround over the following three months, ready for relaunching to build the second tunnel in early 2015.