Projected cost of harbour tunnels rises by $1.2bn

The Auckland Harbour Bridge over Waitemata Harbour. Photo / Dean Purcell

A $1.2 billion dollar blowout in the projected cost of building tunnels across the Waitemata Harbour has been revealed in a new report investigating third harbour crossing options for Auckland.

The NZ Transport Agency report into the costs and benefits of building a bridge or a tunnel across the harbour puts the cost of four tunnels at $5.3 billion - up from the $3.7 billion to $4.1 billion price tag put forward in a 2008 study by the agency and multiple Auckland Councils.

It shows a second bridge across the harbour would cost $1.4 billion less than a tunnel, reduce the annual maintenance bill by $15 million and take less time to construct.

Differences in the constructability of a bridge or a tunnel were minimal, the report said.

Despite the report's findings, Transport Minister Stephen Joyce stopped short of endorsing a bridge project.

He said the Government wanted to consider public views before deciding on what kind of crossing to build across the Waitemata Harbour.

"Both the form of a third crossing and the timing of it will be part of the discussion around Auckland's spatial plan. This will likely be one of the biggest projects for Auckland over the next 20 years and it needs to be planned and sequenced carefully alongside other investments."

Auckland Mayor Len Brown indicated he would prefer to see a tunnel dug under the harbour, but said it was important to keep options open.

"My initial view is that the tunnel option makes more sense. However, I want to hear Aucklanders' perspective on the options available.

"Tunnelling technologies are advancing quickly and many countries are building combined road and rail tunnels that would future-proof our system. The study only looks at dual tunnels and I hope NZTA will look at single tunnel options for the future."

Mr Brown said whichever option was agreed to, it must include capacity for rail.

Mr Joyce said he hoped the report would frame the debate around what harbour crossing option should be approved.

"Because of the importance of any new crossing, all stakeholders, including members of the public, must have access to solid information as they form opinions and consider options as to whether a bridge or tunnel is more appropriate, and when it should be built."

Another harbour crossing would be needed within 20 years to cater for Auckland's growth, Mr Joyce said.

He confirmed the new harbour crossing would allow for public transport and include walking and cycling lanes.

The report was also welcomed by the New Zealand Contractors' Federation because, it said in a statement, it would contribute to the ability of the industry to look forward and plan for future scenarios.

"It will also help to give contracting firms confidence in developing skill levels among their staff and help avoid the patterns of boom-bust and pricing fluctuations we have seen too often in the past," chief executive Jeremy Sole said.

"Today's announcement is also clearly and deliberately focused on lifting New Zealand's economic performance. That is how we will pay for the services our communities need and the people of New Zealand will benefit from these decisions for many years to come."

The 2008 report by the NZ Transport Agency, then Transit NZ, and Auckland's Councils evaluated 159 route options before recommending a set of four tunnels from between Esmonde and Onewa Road on the North Shore and Victoria Park in Auckland City.

It recommended that two tunnels carry three lanes of highway traffic and two contain a single rail line.

Mr Joyce put the option of a bridge across the harbour back on the table in March 2010 when he asked the NZ Transport Agency to develop the 2008 study further.

A statement from the agency said the latest business case aims to establish an understanding associated with each form of crossing.

"The business case will provide a greater level of robustness in the decisions that lead up to the construction."