GLOBAL REPORTS suggest that the country’s economic bubble could be dwindling. For example, the prices of dairy exports – on which the country’s economy relies heavily – have dropped by 40 per cent since the beginning of this year, mostly due to falling demand in China, the country’s main trading partner. Mining, retail, manufacturing and tertiary education job cuts have been made However, the construction sector is one of largest employers in the New Zealand economy, employing seven per cent of the workforce and still growing, a new Government report shows, and is vital to help grow the economy, it states.

Construction Sector Report, the fourth in a series of seven that make up the New Zealand Sectors Reports Series 2013, reveals that the construction sector generates annual revenues of more than NZD 30bn (USD 23.3bn) to the New Zealand economy. It employs 170,000 people, which is more than the agriculture, forestry and fishing sectors.

Steven Joyce, economic development minister, says: "Construction has a vital part to play in our communities and its activity can be felt throughout the economy. From infrastructure and telecommunications to city and community development, it has a direct impact on the quality of life of all New Zealanders.

"Importantly, demand from the construction sector drives a wide range of other activities in the economy. It is part of the fabric of society and that is why this sector is so important." The timing of the projects coming to the table is important. According to the Construction Sector Report the number of firms is 10,000 higher than 2002. However, Brett Gliddon, highways manager for Auckland and Northland. explains that a key consideration for the NZTA when the Waterview Connection project was tendered was "the availability of tunnelling resources in the Australasian market".

Gliddon adds: "The Waterview Connection project commenced in 2011 as a number of large tunnelling projects in Australia were nearing completion, making the timing favourable."

There is a treasure trove of underground opportunities in New Zealand with many tunnelling projects underway or in the pipeline.

Last year the NZ Transport Agency (NZTA) revealed plans for a second Mt Victoria Tunnel, as part of a NZD 800M (USD 621.M) traffic improvement project from Ngauranga to the airport.

Construction of the Mt Victoria Tunnel is expected to take place from 2018 – 2022, although construction has yet to be formally confirmed. The tunnel will be roughly 14m wide, 650m long, and located about 25m to the north of the existing tunnel. NZTA states that next year the agency will seek RMA approvals for the highway improvements via the national consenting process.

Just north of Auckland an underground tunnel is currently being constructed from the Watercare Pump Station off Millwater Parkway at Orewa to subdivisions north of Grand Drive. McConnell Dowell Constructors is drilling the 3.15km tunnel for the Millwater project using TBM Nancy. The company also bored wastewater micro tunnels for the NZD 83.5M (USD 64.9M) Christchurch Ocean Outfall, the largest civil engineering project undertaken by the Christchurch City Council before the Canterbury earthquakes.

Auckland is now home to New Zealand’s longest road tunnel, and the most expensive tunnel project in the country. Auckland has a population that is expected to continue to grow faster than the national average and there are numerous infrastructure projects planned for the city – including the Auckland CBD rail link and the Second Harbour Crossing – are planned for the city.

Gliddon says: "The size and geographic location of Auckland, a city with a population of 1.5 million people and growing by three per cent annually, is situated on a narrow isthmus between two harbours. Space available for necessary infrastructure to support the city is at a premium.

"Auckland’s transport authority, Auckland Transport, is planning an underground extension to the commuter rail network known as the City Rail Loop (CRL). While the metropolitan water authority, Watercare, is applying for consent for a 14km wastewater tunnel."

The City Rail Link (CRL) is an underground rail line linking Britomart and the city centre with the existing western line near Mt Eden. The New Zealand government has said that the project is a top priority for Auckland as current public transport will be unable to cater for the growth expected in the city, hindering economic development.

The current phase is to confirm and protect a route to enable future construction. The CRL will use twin 3.4km long tunnels up to 42m below city centre streets. It is estimated to take five and a half years to build at a cost of NZD 2.4bn (USD 1.9bn) when inflated to 2021, which will overtake the Waterview Connection as the country’s most expensive tunnel. The proposed Additional Waitemata Harbour Crossing (AWHC) project is part of NZTA’s long term planning to meet Auckland’s future transport needs, the agency states. The AWHC project is currently in the investigation stages.

The recommended option, selected from several hundred considered alignments, comprises four tunnels – two for trains and two for the motorway – east of Auckland Harbour Bridge.

The Central Motorway Junction on the isthmus would link to the Northern Motorway, while the suburban rail network could in future be extended northward from the Auckland Central Business District to the North Shore.

While the Waterview Connection project, which will provide the final link in Auckland’s Western Ring Route, has recently reached its halfway point. The first of the twin road tunnels on the NZTA Waterview Connection project has been completed and the TBM, named Alice, is currently being turned around to bore the northbound tunnel. The project is the country’s biggest and most complex roading project to date and is due to be completed by 2017.

"At some 2,450m long the Waterview Connection tunnels will be the longest road tunnels in New Zealand surpassing the 1940m Lyttelton road tunnel near Christchurch, which opened in 1954. Regarding cost, the NZD 1.4bn (USD 1bn) Waterview Connection is the largest and most expensive roading project undertaken in New Zealand," says Gliddon.

When tunnelling in New Zealand, it is vital to consider the country’s topography and geology. Gliddon adds: "The Waterview tunnels are being undertaken in an urban environment in NZ’s largest city, through predominantly sedimentary sandstone with average strengths between 1MPa and 5 MPa. By contrast, the Manapouri Tailrace tunnel (a 10kn-long, 10m wide tunnel using a 1,000t TBM) was constructed in an extremely remote location in the southwest of the South Island through with rock exceeding 100MPa".