KEY POINTS:
Transit NZ is re-examining its $330 million Victoria Park motorway tunnel project in Auckland to ensure compatibility with deeper excavations for a possible new $4 billion Waitemata Harbour crossing.
Although it has planning approvals for a northbound "cut and cover" motorway through Victoria Park to carry traffic to the harbour bridge, Transit is investigating the robustness of its design against the prospect of digging a pair of deeper cross-harbour tunnels next to it.
Harbour crossing study consultant Tony Innes told Auckland's regional land transport committee yesterday that initial analysis suggested a need for some "alterations" to the shallower Victoria Park tunnel to protect it from the larger and longer-term project, which may be 20 to 40 years away.
That meant extra work on the Victoria project "to make sure it is designed and built so the harbour crossing can be built next to it without compromising it," he told the committee.
Engineers would have to ensure digging the deeper tunnels would not undermine its stability, said Mr Innes, who is transport planning manager for consultants Sinclair Knight Merz.
Although Transit officials were not involved in yesterday's presentation, Auckland Regional Council transport group manager Don Houghton told the committee that the highways agency had already commissioned work to that end.
Similarly, the Auckland Regional Transport Authority had agreed to start work on protecting a route for a separate pair of railway tunnels, to follow a proposed new motorway link beneath the harbour to Wynyard Pt, before diverging from it to head to the central business district.
A preferred route for three-lane motorway tunnels would be under Victoria Park to link them with Spaghetti Junction.
The new crossing would then be designated part of State Highway 1, leaving the existing harbour bridge for local traffic between North Shore City and central Auckland.
The shorter tunnel option was challenged by an "access and mobility" representative on the transport committee, Bevan Woodward of Cycle Action Auckland.
"They want it [the below-harbour crossing] to be the connection with SH1 - therefore the Victoria Park tunnel is not necessary," he said.
Mr Innes said the Victoria Park tunnel would remain the key connection for traffic heading to the harbour bridge, from Wellington St, but acknowledged vehicle volumes would be "significantly reduced" if a new crossing was built.
Transit aims to open a northbound tunnel through Victoria Park by 2013, with provision for a southbound tunnel to be built later, after which it would demolish the existing motorway viaduct.
Mr Woodward, who also represents the Forum for Auckland Sustainable Transport, told the Herald it seemed Transit may be preparing to spend even more money on a tunnel which was "going to be redundant."
Asked how Auckland traffic would cope without a tunnel while waiting 20 to 40 years for another harbour crossing, he said he believed that rising oil prices would be enough to reduce congestion.
Senior Transit official Tommy Parker said last night that although design modifications to the Victoria Park tunnel may add to the project's price, they would not require any changes to resource consents.
He was unwilling to provide traffic projection figures for the harbour bridge in the event it loses its status as part of SH1, saying there was no guarantee the new crossing would be built, and Auckland's transport needs had to be met in the meantime.
But he said the preferred crossing route recommended from a $1.3 million multi-agency study was aimed at a balanced distribution of traffic between harbour tunnels and the bridge, with or without its clip-ons.
