The project involves the construction of 4.8 km of a six-lane motorway to link State Highways 16 and 20, bringing relief to the city of Auckland and providing speedier access to the national roads network from New Zealand’s primary international airport. It will significantly improve commuter routes.

Each tunnel will carry three lanes of motorway traffic. They are part of Auckland’s Western Ring Route, one of the Government’s flagship Roads Of National Significance (RONS). When completed, the Western Ring Route will be a 47-km-long motorway between Albany on the North Shore, around the top of the Waitemata Harbour, and Manukau in the city’s south.

Surface works, both to the north and the south of the tunnels, include construction in some densely populated areas. Dennis, a 98-m-long, 140-tonne "super" gantry, has been launching precast beams for more than 18 months. According to the NZTA website, the four interchange ramps to connect the two motorways involve 1.7 km of new bridge structures, including 270 precast concrete beams, each up to 37 m long and weighing up to 65 tonnes, to create the 53 spans.

Peter Spies, chief advisor of engineering assurance with NZTA, says the authority considered a number of contracting models.

"Alliancing is the premium contract model used where there are special features associated with the project and/or where the project is very complex," Spies says. "While a number of tunnels have been built in New Zealand, none were of the size or length required for the Waterview Connection Project. The length of the proposed tunnels also increased the need for specialized fire and life-safety features, while construction would take place in a built-up urban area with major traffic issues and a sensitive environment."

The NZTA concluded that an alliance (known in the U.S. as partnering) model, was the best approach. On the Waterview project, reimbursement to the non-owner participants is 100% open-book, subject to verification by audit. Reiumbursement includes 100% of what they expend directly on the work, including project specific overheads; a fixed lump sum fee to cover corporate overheads and profit; and an equitable sharing of gain/pain depending on how actual outcomes compare with pre-agreed targets in cost and non-cost performance areas.

An Alliance Management Team (AMT) manages the project day-to-day, with members assigned on a "Best for Project" basis without regard to which party employs them, Spies adds. There is an express commitment to resolve issues without recourse to litigation except in the case of "willful default." The participants also develop and commit to work within an agreed set of "Alliance Principles."