Technology
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Case
studies of technological practice
The
Newlands Interchange Project
This material has been produced by the Royal Society of New Zealand under contract to the Ministry of Education. It
has been written to assist teachers and schools in their delivery
of the Technology/Hangarau curriculum statements. The project
is jointly co-ordinated by personnel from the Technology
Education New Zealand (TENZ) and National Association of Māori Mathematicians,
Scientists and Technologists (NAMMSAT) networks. Monitoring and
evaluation of the material is carried out by a national project
advisory group.
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Introduction
Newlands interchange is at the top of the Ngauranga Gorge – a steep
grade of about one in twelve, over a short 1.8km length of State Highway
1 situated 8km north of Wellington City.
(PHOTO: Looking South down the Gorge)
The Newlands Interchange Project was a huge civil engineering challenge
which involved removal of an existing set of traffic lights and conversion
of the T-intersection with the State Highway into a grade-separated
interchange - the aim being to reduce both the amount of traffic congestion
and the number of vehicle accidents.
(Newlands Interchange: Layout)
The construction phase began in January 1997 and was completed, with
a minimum disruption to road users, two months ahead of schedule in
August 1998. The cost of $16.7 million was $600,000 below allocation.
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Overview
of the development of the project
The need
The Ngauranga Gorge section of State Highway 1 carries large volumes
of commuter traffic between Wellington City and northern areas including
Johnsonville, Newlands, Porirua, and the Kapiti Coast, as well as being
the main route for travellers north from Wellington. The traffic flow
is approximately 60,000 vehicles per day and this is growing at approximately
3 percent each year. About 13,000 vehicles a day use Newlands Road,
which previously formed a signalised
T-intersection with the State Highway. The very high morning and evening
weekday peak directional flows on State Highway 1 resulted in considerable
peak hour congestion and an unacceptably high number of traffic accidents.
A number of options were considered during the investigation and design
phases to resolve the problems at this intersection. The Interchange
proposal was finally adopted after extensive consultation and assessment
of the traffic, economic, and environmental issues.
Major
groups involved in the project
Client:
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Transit New Zealand
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Consultant:
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Opus International Consultants
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Main Contractor:
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Fulton Hogan Ltd
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Disciplines involved in the consultancy work for the investigation, design
and construction phases included engineers, scientists, planners, draughting
staff, and lawyers.
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Key features of the new interchange:
- The Newlands overbridge providing grade-separation of the
interchange
- A fourth lane northbound to the Newlands off-ramp
- Upgrading of signage
- Separate provision for pedestrians and cyclists, including
two subways
- Upgrading of highway lighting
- Extensive reshaping and trimming back of the steep rock bluffs
on both sides of the gorge
- Strengthening and rehabilitation of an existing major culvert
carrying the Ngauranga stream and buried up to 17m below the
intersection
- Extensive landscape rehabilitation and revegetation
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Specific features and innovations relating to the project:
- Adoption of a formal Partnering Charter at the beginning
of the construction phase to foster a team approach between
the client, consultant, contractor, and other parties involved.
This was one of the first applications of this approach on a
Transit New Zealand project.
- A very high standard of temporary traffic control to maximise
the safety of workers and motorists whilst also minimising disruption
to the public.
- Cuttings up to 50m high in highly fractured rocks with residential
properties at the top of these slopes and a very busy highway
at the bottom required risk assessment and decision analysis
to optimise costs and risks.
- Adoption of a steel box girder form for the bridge superstructure
to enable erection with minimum traffic disruption.
- Architectural input into the bridge design to produce an aesthetic
structure in a location where the bridge has high visual significance
as a gateway structure to Wellington.
- A demanding site which is exposed to high seismicity and in
close proximity to the Wellington fault, with variable ground
conditions across the site required a range of special features
to provide significant earthquake resistance.
- The use of new technology zinc/aluminium thermal metal spray
for corrosion protection of the bridge box steel girders to
provide an expected life to first maintenance in excess of 40
years.
- Resolution of potential conflicts between vehicles, cyclists,
and pedestrians through, for example, provision of subways.
- Strengthening and rehabilitation of the major culvert carrying
a stream beneath the intersection using an innovative system
employing internal sleeving and grouting.
- Measurement of noise and light levels prior to commencement
of construction to provide a benchmark against which to compare
these conditions as they arose both during and after construction,
and monitoring of noise levels during construction.
- Extensive landscaping to ensure revegetation and to blend
the interchange structures into the natural landscape and environment.
- Extensive community consultation throughout the duration of
the project, including regular meetings with community representatives
to provide information and promptly address any complaints as
they arose.
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