The rear view on Waterview
30 November 2018
WSP:
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. To see the awards submission video,
click here.
The project was delivered by the Well-Connected Alliance comprising the
NZ Transport Agency, WSP,
Beca,
Tonkin + Taylor,
McConnell Dowell,
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:
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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.
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Building community recreational facilities in consultation with the community.
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Using the project as a case study by the NZ Ministry of Education for its Education to Engineering Program.
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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.
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Preserving the remains of a historic local mill on Oakley Creek and rebuilding of century old stonewall.
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Relocating a protected copper skin lizard colony and 1,500 short finned and long finned eels.
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Relocating wild geranium plants and seeds into an impacted reserve with a local conservation group.
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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.
--ENDS--
Source: WSP - www.wsp-pb.com
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