Details of the country's most expensive transport project by far will be announced by Finance Minister Michael Cullen today.
The Government is poised to reveal plans for a long and deep motorway toll tunnel costing up to $2.3 billion.
But although a bore tunnel stretching 5km beneath Mt Albert in Auckland is Transit NZ's preferred option for completing Auckland's western bypass, the Government is understood to be about to put the project under a steering group of public- and private-sector officials.
Sources indicated last night that Transit, soon to be merged with Land Transport NZ, was about to be sidelined on the "Waterview Connection" project in favour of a six-member committee of two Government and three private-sector representatives with an independent chairman.
Although Transit is understood to have political backing for a full tunnel, to limit social and environmental upheaval along a route running mainly through Prime Minister Helen Clark's Mt Albert electorate, it fears a 2015 deadline for completing the project may be missed if the new body chooses to re-examine all alternatives.
These range from a $1.1 billion covered trench through the sensitive Oakley Creek catchment to Waterview, to a $2.5 billion extended route through the industrialised Rosebank Peninsula - an option ditched by Transit but favoured by the Auckland Regional Council, although at a lower cost.
A full tunnel to Waterview, with capacity for three traffic lanes each way, would cost up to $2.3 billion. It could be up to 50m deep.
Although Transit had yet to complete tunnelling investigations before designating land for the project, its estimate of design costs alone has soared from $50 million last year to $79.4 million in its latest draft highways programme.
It also emerged yesterday that Transit was considering road tolls to help pay for the project, even though public opposition last year forced it to back away from a wider proposal to charge motorists to use the ring route along most sectors between Manukau City and Albany.
The agency would not answer queries from the Herald on Tuesday about tolls, but has described these to Auckland local body officials as critical to the project.
Although Beehive staff would not discuss the project ahead of an announcement expected from Dr Cullen at an Auckland Chamber of Commerce lunch today, Transport Minister Annette King is understood to favour a bore tunnel.
So is Helen Clark, who a fortnight ago foreshadowed "an important announcement soon about progress on the Waterview Connection".
Although a bored tunnel would cause less community and environmental disruption than Transit's initial $1.15 billion "cut-and-cover" trenching proposal for the Waterview link, Green MP Keith Locke said his party would oppose any extension of the State Highway 20 motorway if it gained the balance of power in this year's election.
"We should complete Auckland's public transport network first, and then see if we still need it when peak oil goes through the roof."
But Auckland Chamber of Commerce chief Michael Barnett, who is also the regional council deputy chairman, said on Tuesday there was little point having a "ring route" with a missing middle section.
Regardless of whether the Waterview link was tolled, he saw it as an ideal candidate for funding through a public-private partnership.
HOW IT COMPARES
* Waterview Connection - proposed - up to $2.3 billion
* Auckland-Manukau Eastern Transport Initiative - proposed - $1.33b
* Transmission Gully motorway (Wellington) - proposed - $950m
* Auckland Northern Busway - completed - $300m