It’s been over a year since New Zealand’s largest roading project, the Waterview Connection, first opened.
The tunnel has had one of the biggest impacts on how people travel in Auckland since the opening of the harbour bridge in 1959, and was described by client NZ Transport Agency as an example of ‘world-class engineering’. Last night, the auspicious project received recognition on the international stage, winning the 2018 Global Road Achievement Award for Design from the International Road Federation.
The project was delivered by the Well-Connected Alliance comprising the NZ Transport Agency, WSP, Beca, Tonkin + Taylor, McConnell Dowel, Fletcher Construction and Obayashi Corporation.
Charlie Jewkes, Project Alliance Board member and WSP Director for Transport, summarised the importance of the project and the people involved. He said, “The Waterview Connection was a unique opportunity for a group of internationally agile organisations to come together as one team to shape how the city of Auckland travels. By working cohesively we shared our strengths and challenged what had been done before in our respective disciplines. In doing so, we established a benchmark for road projects, and for future mega-projects in Auckland.”
Here, we take a look at what made this project a unique venture and one that left a lasting legacy for Auckland’s community and workforce.
Envisioned in the Fifties
The Waterview Connection was first anticipated in transport plans for the city in 1954, however complex geotechnical ground conditions and constraints at the project site meant it took more than sixty years before the tunnels became a reality. The 47 km motorway includes twin 3-lane tunnels at 13.1m diameter x 2.4 km long and a motorway-to-motorway interchange. Bypassing the city to the west, it links Manukau, Waitakere and North Shore regional centres and improves regional connections, completing the Western Ring Route (WRR), a second motorway route through the city.
Tunnelling Through a Lava Flow of History
Located in the Waitemata Basin, the project site features variable ground conditions including a thick layer of basalt formed from the nearby Mt Albert. As a result, most of the tunnel route passes through unique ground sediment, featuring challenging seismic conditions and high-water inflows. Sandstone and siltstone are present at the southern end of the alignment, while at the northern end the tunnel passed at a shallow depth of 8 m beneath the busy Great North Road.
Dr Doug Maconochie, WSP’s Technical Director of Tunnels and Tunnel Design Manager for Waterview says, “Excavation required the use of a Tunnel Boring Machine (TBM) that could operate in all possible ground conditions and resist potential high ground inflows, while limiting possible ground settlement to within consented limits.
In order to meet the challenging conditions, the 10th largest earth pressure balance TBM in the world, Alice, was used to build the project’s tunnels. It measured 87 m in total and weighed 2,400 tonnes (3,100 tonnes when combined with backup gantry.
Moving a TBM of Alice’s size is considered rare and the project attracted widespread media interest internationally.
“Turning Alice around to build the second tunnel was one of the most technically challenging tasks owing to its size and weight, combined with restricted access below and above ground, with the construction site bordered by the Great North Road and Waterview Primary School,” explains Dr Maconochie.
“The decision to use Alice proved to be the best option, supporting on-time and on-budget delivery of the tunnel design.
“We were able to manage the project’s geotechnical risks while also helping to minimise costs and programme risks.”
Managing Risks Efficiently
Two significant areas of risk were identified early on in the project: the design and production of 24,000 pre-cast tunnel lining segments, as well as the design, procurement, installation and commissioning of the tunnels mechanical electrical and fire protections systems. Using an innovative structure, the Well-Connected Alliance partnered with two specialist sub-contractors under a collaborative risk sharing sub-alliance contract which allowed expertise to be leveraged while ensuring delivery of their scopes were fully integrated with the overall project. This smart plan of attack meant risks were managed and both programs of work were delivered under budget.
The Alliance also adopted a unique way to manage the 140 building consents required for the project. Together with Auckland Council and the Ministry of Business, they spent 12 months developing and formalising a charter that set out an agreed process to fast-track building consents, saving significant time and costs in lengthy approvals and consultations. This process was recognised by Auckland Council as a successful regulatory delivery model for public and private infrastructure.
Safety in Design
Auckland sees thousands of commuters use the Waterview tunnel each day. With safety during operation being of utmost importance, the Alliance responded by building a fire-life safety and ventilation system that incorporated international best practice.
To achieve this, the team looked at design from a first principles approach, using a combination of models for fire, smoke, management and risk to assess the effectiveness of safety measures. The project utilised an ingenious jet fan solution to direct smoke downstream of fire and away from people and traffic; thereby demonstrating that acceptable safety levels could be achieved without costly and complex smoke exhaust ducts.
Meanwhile, the tunnels deluge system was designed to deliver approximately 5,000 litres of water per minute to a fire site. Adopting a risk approach enabled the team to capture the spectrum of system performance resulting in a fire-life safety system that was both effective and low-cost.
A Tribute for Auckland
Perhaps the most memorable part of the Waterview Connection is the tribute that it leaves for the city of Auckland. Not only did several project initiatives boost the local economy, they also provided an enhanced quality of life, supported environmental sustainability and paid respects to the city’s rich cultural heritage. Some of these initiatives included:
Upskilling the existing workforce to complete the project. This was supported by the provision of technical training and English lessons which left a tribute of knowledge behind for the New Zealand infrastructure development industry.
Building community recreational facilities in consultation with the community.
Using the project as a case study by the NZ Ministry of Education for its Education to Engineering Program.
Paying homage to the site’s unique heritage by adorning panels of concrete art at the southern portals of the tunnels which depict a Maori legend.
Preserving the remains of a historic local mill on Oakley Creek and rebuilding of century old stonewall.
Relocating a protected copper skin lizard colony and 1,500 short finned and long finned eels.
Relocating wild geranium plants and seeds into an impacted reserve with a local conservation group.
Transforming Oakley Creek to provide access to a naturalised community water feature, better natural habitats for native flora and fauna and more riparian planting than previously existed.
Since it opened, the Waterview Connection has supported a massive increase in capacity for the Auckland road network. A month into operation, Former Transport Minister Simon Bridges said, “Road users are benefiting from quicker, more reliable travel times and traffic flows across both local roads and Auckland’s motorway system. Around 60,000 vehicles are using the Waterview Connection each day, with more than 2 million vehicles now having travelled through the twin tunnels between the suburbs of Owairaka and Waterview.”
Over the next 10 years, the Alliance will continue to work together to maintain the project.
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