Would YOU hop on a floating tube to Ireland?
It’s not a bridge or a tunnel, and it will run from Scotland... 164ft under the waves
WHEN Boris Johnson floated the idea of a bridge linking Northern Ireland with Scotland in 2018, one offshore engineer ridiculed the concept saying it would be ‘about as feasible as building a bridge to the moon’.
But last week, it emerged that the idea of a fixed link between Portpatrick in Wigtownshire and Larne across the Irish Sea is very firmly back on the agenda.
Sir Peter Hendy, chairman of the Union Connectivity Review, a study to identify ways to strengthen transport links across the UK post-Brexit, revealed that he has been ‘asked specifically’ to look into the idea.
Indeed, he has gone so far as to appoint construction bigwigs Douglas Oakervee, a former chairman of HS2 and Crossrail, and Gordon Masterson, a former vice-president of Jacobs Engineering, to undertake an investigation into the proposed crossing.
But it turns out that a bridge over the water is no longer the engineering community’s favoured option, as gale-force winds in the Irish Sea would force any such link to be closed for around 100 days a year.
The alternative scheme attracting growing support is a tunnel — not a conventional one drilled under the sea floor but a revolutionary £12.3 billion ‘submerged floating tube bridge’, which would sit 164ft (50 metres) below the surface supported by a system of pontoons and anchors. At that depth, its proponents point out, ‘the water is very constant and calm’ and so bad weather is not an issue.
Detailed plans have yet to be drawn up — but the graphic here shows some of the thinking that might go into such a link.
‘There’s no doubt that a submerged tunnel link would be feasible,’ says Professor Guy Walker, head of the pioneering education department at Edinburgh’s Heriot-Watt University, which has produced a 169-page report on the concept. ‘We’ve done the sums and we have worked out that four million people would use it every year. It is expensive, but then large infrastructure projects always are. Eventually, it would pay for itself.’
NOT only would a tunnel floating 164ft below the surface allow for the free passage of ships above it and submarines above and below it, but it also promises to be the cheapest option by far. A bridge would require the installation of up to 50 huge supports — 30 of which would have to be 1,400 ft (430 metres) tall in order to hold the bridge over the deepest part of the sea and keep it high above shipping lanes.
Any bridge would also have to cross Beaufort’s Dyke, a natural trench seven miles off the coast of Portpatrick that is filled with a million tons of dumped munitions. Conservative estimates put the price tag for such a project at £20 billion but some suggest it could rise as high as £50 billion.
There are two other tunnel options: a direct tunnel to Northern Ireland under the seabed, which would involve drilling up to 1,000ft (300 metres) beneath the waves; and another involving three tunnels, one from Liverpool, another from Heysham in Lancashire, and a third from Stranraer in Wigtownshire, meeting under the Isle of Man and continuing to Northern Ireland. Both options are seen as prohibitively expensive.
The floating tunnel idea may be radical but it is inspired by a project under way in Norway.
The Norwegians are world leaders when it comes to submerged roadways, which are especially suited to traversing deep fjords surrounded by steep mountains.
Oslo is funding a £30 billion project designed to halve the time taken to make the 700-mile drive between the cities of Kristiansand in the south and Trondheim in the north, which involves seven ferry trips and takes 21 hours.
The idea is to replace the ferries with a combination of bridges, conventional tunnels and a submerged roadway — a pair of concrete tubes running about 100 ft (30 metres) below the water’s surface. They will be held in place by floating pontoons and, if necessary, massive concrete anchors attaching them to the sea floor.
The proposed Celtic crossing would be considerably more challenging, consisting of a 28-mile subsea section. To avoid disruption and protect wildlife, the HeriotWatt plan envisages establishing the terminals around three miles inland on each coast.
They believe the new link — with a lifespan of up to 150 years — could reduce the travel time of two hours 30 minutes by ferry to 40 minutes by car, with vehicles loaded on to a rail service like Eurotunnel’s Le Shuttle or driven over.
It would still have to contend with Beaufort’s Dyke, of course. Two miles wide and 700 ft to 1,000 ft (213 to 304 metres) in depth, it was used as a munitions dump after World War II because of its proximity to Cairnryan Military Port.
Its toxic contents include 14,500 tons of five-inch artillery rockets filled with phosgene dumped there in 1945, and two tons of metal
drums filled with radioactive waste from the 1950s.
The debris has been described as ‘unstable’, with former Royal Navy diver Michael Fellows explaining to the BBC in 2004 that there are ‘sporadic explosions two or three times a month’ in the Irish Sea.
But Heriot-Watt’s Professor Walker, whose team has submitted a summary of its study to the Hendy review, argues that a floating tunnel would get round the dangers. ‘One of the strengths of this technology is that, unlike drilling under it or laying something on top of it, a floating tube bridge is submerged about 50 metres, so we’re well clear of hazards,’ he says. ‘Ships can pass over the top and submarines can pass underneath. We’re a long way from disturbing anything on the seabed that needs to be left there.’
The ‘floating tunnel’ project was originally the idea of Alan Dunlop, an academic and a fellow of the Royal Incorporation of Architects in Scotland. ‘In 2018, I was asked by a newspaper if a physical link between Northern Ireland and Scotland was feasible,’ he says.
‘I was intrigued by that. It would certainly be financially beneficial to both Scotland and to Northern Ireland. So I set about researching it and drawing up some plans and the whole thing took off.’
The Prime Minister has form for proposing grands projets, such as Boris Island — an airport proposed but never constructed on a manmade site in the Thames estuary — and the Garden Bridge, a doomed folly farther up the Thames that was abandoned after soaking up £53 million of taxpayers’ money.
‘There was a sea change as soon as he endorsed [the floating tunnel],’ says Professor Dunlop. ‘Engineers, architects like myself and other professionals were all in favour of it. Then Boris got involved and it became Boris’s folly, a crazy idea. But I still believe in it and it will be built. It might take ten years but it will happen.’
The submerged roadway has already been given an official vote of confidence. It is one of the schemes covered by a £20million feasibility study of infrastructure projects considered worthy of further examination by the Hendy review, which will deliver its findings in the summer.
It remains to be seen whether Boris Johnson will decide that now is the time to give the Celtic crossing serious political backing and stump up the cash. Or whether, like the Garden Bridge, it will be left to wither on the vine.