The Cook Strait is a violent body of water. It’s an exception. Unlike other straits around the world, it has opposite tidal flows at either end. When it’s high-tide on the Tasman side, it’s roughly low-tide on the Pacific side and vice versa
Before the end of the last Ice Age, you might have been able to walk between the two islands – if there had been anyone around to do it. But for the last 20,000 years this strait has divided New Zealand in a way most countries have never known.
What if the country could become physically connected again? Is a Cook Strait bridge or tunnel pure fantasy?
There would be far more to gain than just the novelty of being able to take a 27 hour 2,000 kilometre drive from Cape Reinga to Bluff: an immense increase in traffic between the two islands, the untold billions saved in shipping and flying costs, the Marlborough and Wellington areas thriving and booming from increased commerce, the tourist dollars, the sheer convenience of replacing a three-hour ferry ride (and its associated on- and off-loading times) with a short drive.
It’s an idea that’s so outrageous even some of our more seasoned politicians have never heard it being raised before.
But Stuff pitched the idea to Transport Minister Phil Twyford.
Transport Minister Phil Twyford suggested a tunnel would be ruled out by the Alpine Fault and a bridge by the strait’s rough waters.
“This is the first time I’ve heard the idea. I know there is a successful tunnel between the United Kingdom and France, but I would have thought our faultline would rule out a tunnel. It is also a very rough stretch of water, and I’m no engineer, but I suspect that would rule out a bridge,” he said.
Judith Collins, who has National’s transport portfolio, was impressed by the idea, but pointed out an obvious flaw.
“Wow, this is a hugely ambitious and audacious idea. Where would be the fun of a Cook Strait pie in the middle of a howling gale though?” she said.
The idea of having a bridge or a tunnel between Wellington, pictured, and the South Island was raised seriously just once by Premier Richard Seddon in 1904.
It seems to have been seriously raised only once by a New Zealand politician. A long time ago.
A Hawke’s Bay Herald article from 1904 said that Premier Richard “King Dick” Seddon had been travelling all over the country bragging about how much money the Government had for grandiose projects, including a tunnel through the Cook Strait .
The unnamed reporter at the time felt it was inappropriate given the large loans New Zealand had taken from London. With a tongue-in-cheek, the reporter said that if Seddon told the public about the reality of the Government’s financial position, they might agree to his tunnel plan some time in the future.
JULIAN LEE/GOOGLE MAPS
One of the possible routes for a Cook Strait bridge or tunnel: Cape Terawhiti to the peninsula east of Picton, the shortest route between the mainland and the North Island, 27km.
These days something like 1.1 million people and 350,000 vehicles cross the strait every year with the two ferry companies, Interislander and Bluebridge. Should there be a drive option, many more would be guaranteed to use it – those who would normally fly or not take the trip at all.
With a bridge or tunnel, the prohibitively expensive and time-consuming trip from somewhere like Palmerston North to somewhere like Nelson becomes a drive that could be done in less than five hours.
Ask someone in the know and they will quickly explain that it is a pipe dream.
University of Canterbury structural engineering and materials professor Alessandro Palermo suggests that a “submerged floating tunnel” could be a better option for the strait.
“I think given the geometry and the morphologies of the strait, a conventional bridge is not possible. The water is extremely deep and the cost will be prohibitive. Tunnelling will also be very expensive.”
That’s from University of Canterbury structural engineering and materials professor Alessandro Palermo – one of New Zealand’s top bridge specialists.
Palermo does have a proposal, but before that, what are we dealing with here? And most importantly, how much would these projects cost?
The Bluebridge and Interislander ferries, seen here in Picton, both take about three hours to cross the often violent stretch of water.
It is tempting to look at the strait’s narrowest point of just 22km for a potential crossing from Cape Terawhiti to Arapaoa Island in the Marlborough Sounds. That, however, means building a state-highway tier road through the extremely hilly country behind Karori all the way to the coast, another such road across undeveloped Arapaoa Island in the sounds, a bridge across the Tory Channel and another road to get back to State Highway 1.
A 27km bridge or tunnel from the cape directly to the mainland and bypassing Arapaoa, landing on the peninsula east of Picton, would still involve significant roadworks.
If, on the other hand, you wanted to build a link between the two closest developed points (Wellington city and either Picton or Blenheim), the distance is 64km to Picton and 65km to the shoreline just east of Blenheim.
The 2.4km Waterview Tunnel in Auckland, pictured, cost $1.4b, which equates to about $583m per kilometre. For a 27km tunnel, that’s $15.7b. For a 65km tunnel, that’s $37.9b.
BRIDGE OR TUNNEL?
Bridges are much cheaper than tunnels. The catch? A bridge would have to withstand a highly turbulent Cook Strait, probable earthquakes and be high enough for ships to get through (or at least able to open up).
A 65km-odd bridge would be New Zealand’s biggest bridge by far. The current longest bridge is Canterbury’s Rakaia Bridge at just 1.8km.
JULIAN LEE/GOOGLE MAPS
One of the possible routes for a Cook Strait bridge or tunnel: Cape Terawhiti to Arapaoa Island, the shortest point between the two islands, 22km.
It’s so long, in fact, that if it existed it would be the sixth-longest bridge in the world.
But the cost of a bridge is not impossible for New Zealand.
The 38km Lake Pontchartrain Bridge in Louisiana, United States is the longest in the Western world. It cost roughly NZ$561m in today’s dollars. For a 60km-odd long bridge, that would be more than $1 billion.
Looking towards Wellington city – the starting point for a tunnel or bridge?
Tunnels, on the other hand, are much more expensive.
The 2.4km Waterview Tunnel in Auckland cost $1.4b, which equates to about $583m per kilometre. For a 27km tunnel, that’s $15.7b. For a 65km tunnel, that’s $37.9b.
JULIAN LEE/GOOGLE MAPS
One of the possible routes for a Cook Strait bridge or tunnel: Wellington to Picton, the shortest route between two developed centres, 64km.
Stuff pitched the strait drive options to the New Zealand Transport Agency (NZTA). A spokesman pointed out that using the Waterview’s costing was probably not worth while.
“Waterview Tunnel went through rigorous business case and cost/benefit analysis. It’s hard to imagine a serious case for a Cook Strait tunnel that would be more than 10 times longer and three times deeper than Waterview and considerably more expensive.
Nonetheless the NZTA was open-minded.
“To the best of our knowledge there’s never been a serious feasibility study of a Cook Strait tunnel, nor has there been a need for it,” the spokesman said.
“The costs to build and operate such a tunnel would be huge, but anything is possible with unlimited time, money and expertise.”
There does not appear to be a simple way to work out how much tunnels cost.
The Channel Tunnel, or “Chunnel” connecting Britain and Europe has the longest undersea portion of any tunnel in the world – its total length is 50.45km, just shy of what would be required under the Cook Strait. The Chunnel’s lowest point is 75 metres below sea level – the strait averages almost twice that depth at 128m.
The Chunnel cost £9b at the time of completion in 1994 – something like $30b in today’s New Zealand dollars.
Japan’s Seikan Tunnel is 54km connecting the islands of Honshu and Hokkaido across the Tsugaru Strait, which is much deeper than Cook with a maximum depth of 200m. Japan, like New Zealand, is a shaky country. It cost around NZ$10b in today’s money.
Stuff pitched the idea of crossing the strait to Treasury. A Treasury spokesman said: “In a hypothetical situation such as what you suggest, the Treasury would provide analysis and free and frank advice to the responsible ministers.
“We would factor in a number of aspects, such as cost-benefit analysis, alternative options and solutions for whatever issue the project is intended to address, impact on the Crown accounts, the government’s capital spending allowances, project funding alternatives (eg government-funded, privately funded, a public-private partnership etc), broader considerations such as environmental and social impacts, and other matters.”:
The spokesman also said how much money was in the kitty for transport infrastructure projects: There is $3.4b available this year and another $3.4b next year, but in 2020 there will be only $3.1b and the following year just $2.7b.
In other words, even if the government were to spend 50 per cent of the country’s capital allowances for transport over the next four years, a tunnel starting from Wellington might not even get to the water.
Having to choose between a bridge that could fall over in the next earthquake and a tunnel that could impoverish the entire country would be enough to make most Kiwis spit their tea out. But perhaps there is a third way.
Palermo, the engineering professor who wrote off the idea of a traditional tunnel or bridge, has another, more modern idea. A “submerged floating tunnel” – a tunnel that floats on or near the surface of the sea and is anchored to the ground.
One has never been built, but the idea is being developed and explored in places like Japan and the USA.
Palermo said sea currents, earthquakes and tsunamis are the main challenges, but: “I think the concept could be feasible. Construction will not be easy, but not far different than building an off-shore petrol platform. The bridge could be manufactured with innovative ultra-high performance concrete and segments of the tunnel prefabricated in a specialised precast yard.
“The great challenge will be the anchors, but it will not be more challenging than an off-shore platform.
“Given the flexibility of the tunnel, its response to earthquakes may not be so problematic and the anchors could be designed to accommodate big ground displacement generated by fault rupture.”
Palermo said the ultra-high performance concrete will reduce the amount of concrete required and guarantee long-lasting durability – perhaps more than a century.
“I also like the possibility to create within the tunnel an outlook with structural glass windows and turning it into an iconic tourist attraction.
“Moreover, it could have a negative carbon footprint (this means that it doesn’t have embedded energy costs) if the impact of currents could be turned into energy to be used for the tunnel or possibly sold out to Wellington and Marlborough.
“It will not have a strong environmental impact and I think it could be seen in the future, especially if there will be a take over with electric cars.”
Palermo said the concept is still being developed and costs are unknown.
The closest New Zealand has ever come to physically uniting the country seems to be a bit of political banter loosely attributed a politician more than a century ago. Seasoned politicians from our own time have not even heard the idea raised once in the halls of Parliament – not even in the back halls.
If New Zealand were to really bridge a 20,000-year-old gap over one of the more problematic stretches of water the world has to offer, it may be time, rather than money, that might be the best bet.