Media Release
31 August 2004
ALPURT B2 tunnel investigations commence
The Northern Gateway Alliance is undertaking further geotechnical investigations this week to develop its design for the
proposed twin tunnels through Johnson’s Hill, near Puhoi.
Earlier this month Transit New Zealand announced that the tunnels, a major environmental initiative, would be included
in the scope of the proposed ALPURT B2 toll road project between Orewa and Puhoi.
Transit’s Auckland Regional Manager Wayne McDonald said the investigations were part of an ongoing programme of site
research by the Northern Gateway Alliance.
“The information being gathered will feed into the design development of the proposed motorway and the finalisation of
the Alliance’s cost estimate, construction and environmental management plans,” Mr McDonald said.
A piling rig will be used to drill a large diameter inspection shaft at the northern portal of the twin tunnels,
allowing geologists to examine rock 20 metres underground. The information will be used to assess the support
requirements for the Johnson’s Hill tunnel portals.
The drilling is expected to be completed by the end of this week.
Mr McDonald said the twin tunnels had major ecological and road safety benefits.
“The tunnels will reduce the visual impact of the motorway on Johnson’s Hill, preserve a significant corridor of native
broadleaf forest and a site of special wildlife interest (SSW1) that links the east and west coasts.”
“The tunnels also reduce the gradient of the motorway, which will be positive for road safety.”
Approximately eight metres high, 13 metres wide and 240 metres long, the tunnels are being designed in accordance with
international best practice, with a strong focus on motorist safety.
A key feature is the twin tunnel design, with a cross-passage between the tunnels at the halfway mark. The tunnels will
be lit, ventilated and have a fire protection system.
Mr McDonald said the twin tunnels would add to a range of other environmental initiatives within the project, including
eco-viaducts over the Nukumea and Otanerua streams, special culverts to accommodate fish passage and extensive
re-vegetation.
The Northern Gateway Alliance, which is project managing, designing and constructing the motorway, is comprised of
Transit New Zealand, Fulton Hogan, Leighton Contractors, URS New Zealand, Tonkin & Taylor and Boffa Miskell. The Alliance has brought in two tunnelling experts with international experience to help with
the project.
Transit is proposing bringing forward the construction of ALPURT B2 by tolling, subject to funding approval from
Transfund and securing approval to toll from the Minister of Transport.
ENDS