The Northern Gateway Toll Road project extended the existing Northern Motorway between Orewa and Puhoi, north of Auckland. The 7.5 km route crossed areas of native bush with high environmental sensitivity. The steep topography required a number of major bridges, tunnels, deep cuts and extensive fills.

At the time, the Northern Gateway Toll Road project was the largest capital cost roading project ever undertaken in New Zealand and was valued at $350 million. The design required special attention to protection of the natural environment and included eco-viaducts, fish passages, water quality treatment facilities and use of construction methods that minimised disturbance of the native bush.

The project was delivered by the Northern Gateway Alliance - composed of Fulton Hogan, Leighton Contractors, URS, Boffa Miskall, NZTA and Tonkin + Taylor. We were a full alliance member, involved right from the bid phase through to the completion of construction, and to the end of the maintenance period. A key aspect which contributed to the success of the project was the direct involvement of designers during the construction phase.

Services provided:

• Geotechnical investigations and development of the geological model

• Geotechnical input into design of the twin 370 m long sequentially excavated tunnels

• Bridge foundation design for viaduct bridge structures up to 500 m long and 30 m high

• Retention design, including landslide stabilisation measures

• Stormwater and motorway pavement drainage design

• Earthworks design, including embankment design for fills up to 30 m high and cuts up to 50 m deep

• Pavement design

• Erosion and sediment control design

• Construction observation and design support during construction.

Northern Gateway Toll Road, Auckland, New Zealand