Leighton Contractors take to the roads

The southern end of the old motorway which has been dismantled on the Newmarket Viaduct. Photo / Sarah Ivey

Road and infrastructure works worth $465 million for central and local government are the biggest jobs on now for Leighton Contractors.

The jobs are the $170 million Auckland west road maintenance alliance for Auckland Transport and two jobs for the New Zealand Transport Agency: the $215 million Newmarket Viaduct replacement, to be finished next December, and the $80 million Wellington tunnel upgrades, to be finished this Christmas.

The Auckland road maintenance contract, started in 2008 and finishing in 2013, is an alliance between Auckland Transport, Leighton, MWH New Zealand and Blacktop Construction.

"The alliance is responsible for achieving all the contract's objectives such as high road construction standards, road signage, pavement design, stakeholder communications, safety improvements and improving the condition of the overall network in as short a period as possible. The five-year contract is the first maintenance alliance awarded in New Zealand," Leighton said.

The area includes Auckland's CBD and stretches from Dominion Rd to the western boundary of Auckland City. That takes in 454km of roads (of which 50km carries more than 20,000 vehicles a day), 25,081 signs, 7km of cycleways, 50 bridges and 30,000 catch pits.

Leighton's second most valuable job at Newmarket is a key to the extensive upgrade of Auckland's motorway network and Leighton is in an alliance on that with NZTA, Fulton Hogan, VSL, URS New Zealand, Beca, Tonkin & Taylor and Boffa Miskell.

The 700m twin-cast-in-situ balanced cantilever bridges were opened to traffic in 1966 but the existing flyover has to be replaced with a wider, stronger motorway bridge. The viaduct carries 160,000 vehicles a day and as the Transport Agency says, a carefully orchestrated sequence of construction and deconstruction stages is taking place, enabling the vital link to operate at almost full capacity throughout the four-year replacement process.

A new southbound carriageway is now up, 13m to the east of the original structure. Traffic is flowing there while the existing southbound bridge was demolished. Part of the job involves realigning the State Highway 1 offramp at Gillies Ave and the onramp at St Marks Rd.

The upgrade of Wellington's Mt Victoria and Terrace tunnels is being carried out by an alliance of NZTA, Leighton with SKM and Aecom. That work is due to finish this December. It involves new fire control systems, ventilation systems, drainage and seismic upgrades

"In an international first, the alliance is applying the tunnel refurbishment and enhancement process developed jointly by Leighton Contractors, SKM and Aecom. This is a holistic refurbishment programme which addresses the challenges of upgrading infrastructure that, in the case of the Mt Victoria Tunnel, is up to 80 years old," Leighton said.

Up to 40,000 vehicles a day use the Terrace Tunnel and thousands of pedestrians and cyclists use the Mt Victoria Tunnel which links the eastern suburbs to Wellington's CBD. Leighton says the tunnel systems are reaching the end of their design life and the infrastructure inside falls short of modern standards.

Big jobs Leighton has completed since setting up here more than a decade ago include the upgrade of the city's Central Motorway Junction, Northern Gateway Toll Road from Orewa to Puhoi and the Manukau Motorway Extension connecting State Highway 1 to State Highway 20 at Manukau. The firm describes its role as "a key partner in some of the country's most complex infrastructure projects".

Leighton Contractors

* Auckland road maintenance alliance, West: $225m

* Newmarket Viaduct replacement: $207m

* Wellington tunnel upgrades: $80m