The proposed City Rail Link through downtown Auckland has been given planning approval. It confirms the route of the tunnel, which is expected to be built within the next decade.
The creation of the 3.5km long rail loop through the central city is the most ambitious transport project in Auckland. The independent commissioners have imposed some conditions, but found no evidence to challenge the benefits of the $2.8 billion project.
Television broadcaster Mediaworks lost its bid for the route to be diverted from underneath its TV3 studios, or for the agency, Auckland Transport, to find it a new home.
The commissioners instead imposed noise and vibration limits during the construction and operation of the tunnels. The Auckland Council wants to start work on parts of the tunnel inside three years, but the Government is so far committed only to construction beginning in 2020.
The council and Government will share the cost but the detail of how it will be funded is not yet clear.
Mayor Len Brown has welcomed the approval, saying it adds another layer of certainty to the project.
Mr Brown has, as his top priority, starting on the rail tunnel by 2016, four years head of the Government's timeline.
The council agency that will build the tunnel has begun talking about a possible early start to individual sections of the link, rather than treating it as one single project.
Auckland Transport's chief executive David Warburton told a council committee on Tuesday that a single start date for the entire project could create too much disruption through the central city.
Mr Warburton said the timing of several large commercial property developments along the route may also dictate when adjacent sections of the tunnel might be built.
Precinct Properties has yet to set a start date for the redevelopment of the downtown shopping centre, under which the rail lines will have to be built.
In the mid-town area, the city's tallest building is expected to be built on the corner of Albert and Victoria streets, adjacent to the proposed Aotea Station.
Auckland Transport says it could be several months before the timing of those developments becomes clearer, and the agency can then assess the impact on the tunnel's construction.
While Auckland Council and the Government will share the cost of the project, the council still hasn't determined how to finance a large part of its share, and the Government's contribution is uncertain.