Manukau Harbour Bridge Auckland, New Zealand

The Manukau Harbour Bridge (crossing) is one of the key sections of the new 48km Western Ring Route motorway bypass in Auckland, which will bypass the Central Business District of the city. The aim of the project is to relieve congestion through the city, to make travel times shorter and more predictable and allow more room for bus lanes.

The existing harbour crossing, also known as the Mangere Bridge, was opened in 1984. The new bridge will duplicate this crossing to the east and allow the original bridge to take traffic one way and the new bridge to transport traffic the other way across the harbour. The aims are:

• To increase capacity for vehicles travelling across Manukau Harbour
• To improve access between the south-western Motorway and Onehunga to Pakuranga arterial route
• To improve efficiency and safety, and to reduce congestion on this part of the SH20 motorway

The project has been scheduled for completion by 2011 with construction completed in time for the Rugby World Cup, provided that funds are made available.

Construction will begin in 2008. Estimated cost falls within the $100m category of Transit New Zealand's 2006/07–2015/16 ten-year State Highway Forecast. The contractor has not yet been appointed.

OPTIONS

The project is the culmination of a series of investigations carried out over a period of more than ten years. In 2002 Transit completed a study that identified the best approach to provide more capacity at the Manukau Harbour Crossing on SH20.

The options considered were:

• Widen existing Mangere Bridge
• Widen motorway and provide duplicate existing Mangere Bridge
• Widen motorway (Queenstown to Neilson) and provide western harbour crossing
• Widen motorway (Queenstown to Neilson) and provide eastern harbour crossing
• Build alternative eastern crossing from Rimu Road to Neilson Street (put forward following consultation with the Maungakiekie Community Board)

The study concluded that building an additional motorway bridge next to the existing bridge is the best option, providing eight lanes across the harbour with bus shoulder lanes.

PROJECT OVERVIEW

The project will now involve the duplication of the Manukau Harbour Bridge to add extra lanes between the Mt Roskill Extension in Hillsborough and Walmsley Road in Mangere. This includes bus priority lanes and a dedicated pedestrian and cycle bridge. The bridge project will allow the continuation of the SH20 through route (relieving congestion), an arterial route from the city to the airport and a local community connection between Onehunga (Neilson St) and Mangere Bridge.

The project will widen the SH20 between Queenstown Road and Walmsley Road interchanges from four lanes to six lanes, with bus priority on shoulder lanes, and from four lanes to eight lanes between Rimu Road and Gloucester Park Interchanges, across the harbour. The existing Mangere Bridge will be duplicated to the east (a second bridge will be built) so that four traffic lanes and a shoulder lane for bus priority will be provided in each direction.

Pedestrian and cyclist usage will continue to be provided along the line of the Old Mangere Bridge. The Rimu Road/Mahunga Drive Bridge will be replaced to allow motorway widening. Further south at Tararata Creek, a new off ramp-bridge and widened motorway bridge is required. At the Queenstown Road Bridge, additional retaining walls at abutments will be required. The Beachcroft Avenue and Hastie Avenue footbridges will also need to be replaced to allow motorway widening.

MANUKAU HARBOUR CROSSING

After the council hearings in August 2007 it was confirmed that Transit New Zealand has decided to proceed with the main Manukau Harbour Crossing Project works to add a duplicate bridge and additional lanes on SH20 between Queenstown Road and Walmsley Street within the existing motorway designation.

The Gloucester Park Interchange is not due to be included at this initial stage. Transit New Zealand wants to move ahead and provide enhanced access on State Highway 20 between Auckland International Airport and Auckland City for both vehicles and public transport as soon as possible.

The future form and location of the Gloucester Park Interchange will be resolved through further discussions between Transit and key regional and community stakeholders, including Auckland City Council, the Auckland Regional Council and the Onehunga Inter Agency Working Group.

The decision to postpone the interchange and find a more broadly acceptable solution follows on from the joint council hearing earlier this year in which the Auckland City commissioners recommended substantial changes to the interchange as part of the amended motorway designation.

TENDER PROCESS

Transit New Zealand has advised that it is currently in the tender process in respect of the Manukau Harbour Crossing project. Auckland City Council conducted resource consent hearings in respect of the project from 21st March to 24th April 2007.

The tender process is expected to continue through to October 2007. Transit New Zealand has deferred the tender of the State Highway 18 Hobsonville Deviation project to July 2007.