5 things I learned about building an Irish Sea tunnel instead of a ‘Boris Bridge’

UK Prime Minister Boris Johnson wants a mega-bridge between Scotland and Northern Ireland. What if we built a tunnel instead?

7 min readJul 14, 2020

In 2019, United Kingdom Prime Minister, Boris Johnson, ordered a study into a mega-bridge linking Northern Ireland with Scotland(1). Experts said his bridge is ‘as feasible as building a bridge to the moon’(2). Afterwards, the Scottish Secretary Alister Jack insisted a tunnel could be an option instead(3).

For the craic, I decided to see what a tunnel could look like. Turns out there was a lot to discover! Here’s my top 5.

Landscape of coastline and sea — Photo by Piotr Gaertig on Unsplash

5. A sea tunnel is an old and popular idea

Back in 1890, Belfast engineer Luke Livingston Macassey published ‘The Proposed Channel Tunnel and Through Trains Between Edinburgh, Glasgow, Manchester, Belfast and Londonderry’. His idea was for an Irish Sea tunnel to create a super-region with faster journeys, more trade and ‘constant intercourse between the three countries’ of Ireland, Scotland and England (4)’.

A century later, the Republic of Ireland worried the Britain-France Channel Tunnel gave the UK too big an advantage in the European Union single market. The government was asked about building an Irish-Wales tunnel ‘…in order that Ireland will not be disadvantaged’(5). The Irish assessment was a tunnel would cost ‘…over twice…the Britain-France tunnel, while the potential usage is estimated at less than 20 percent of that predicted for the Britain-France tunnel’.

Many other tunnel routes have been proposed over the years — such as Wexford to Fishguard, Dublin to Holyhead and Antrim to Argyll. Today, the tunnelling industry is studying a route between Northern Ireland, the Isle of Man and England(6). With so many competing routes, the next big surprise is…

4. The best tunnel route is still open to debate

With so many competing ideas for a tunnel route, I’ve had to draw a table and map. It stopped my heads spinning.

**Table 1 — Irish Sea tunnel short list of options**

Map showing possible Irish Sea tunnel routes between island of Ireland and Great Britain — **Figure 1 — map showing possible sea tunnel routes between island of Ireland and Great Britain**

While we may not yet know where a tunnel will go, we can assume it’s going to look a bit like the Channel Tunnel. A big challenge is connecting that structure to existing infrastructure networks.

3. The sea tunnel is probably simpler to build than the connecting land infrastructure

A sea tunnel will need trunk road and rail infrastructure both to build it and then traffic to use it.

The Irish Mail route has ‘oven-ready’ existing infrastructure. The other options start and finish in remote areas far from trunk road and rail connections. Carving connections through, for example, Scotland’s Kintyre coast would need massive infrastructure work in hilly areas. And without the decent trunk connections, a sea tunnel would struggle to attract decent traffic to help pay for it.

Building a tunnel won’t be a cake walk either…

Fireworks exploding and streaking in a nightsky — Photo by Marc Sendra Martorell on Unsplash

2. A tunnel will be tough to build…

It took six hears, 13,000 workers and £12bn (2019 prices) to dig the Channel Tunnel from the chalk below the English Channel. That geology was excellent for tunnelling; but the Irish Sea is more challenging.

‘Not a simple layer cake’. BGS(11)

Geologically, the Irish Sea is way more exciting than the English Channel. Over a 2.6 million year period, massive glaciers covered the sea, gouging deep valleys and creating a thick stew of sandstones, mudstones and gravels all blanketed with a thick sediment.

And then, near Scotland, on the seabed, there’s the bombs. Lots of bombs.

Beaufort’s Dyke historically blows up a lot

Beaufort’s Dyke is a deep sea trench west of Portpatrick, Scotland. 50 km long, 3.5km wide and 300m deep, the British used it as a munitions dump. Over 1 million imperial tons of WW2 cannon shells, incendiary bombs, high explosive bombs and chemical weapons were sunk, never expected to be heard of again. The British Geological Survey (BGS) seismograph network (12) detected over 47 explosions between 1997 and 2004. One registered 2.9 on the Richter scale. With the still exploding bombs impossible to remove, this is a key reason why a Boris bridge probably won’t work.

But the last and most difficult surprise is probably the politics…

A pair of boxing gloves on a wooden table — Photo by NeONBRAND on Unsplash

1. Ironing out the politics is toughest challenge of all

Megaprojects need stable political support to build them. As example, while controversial, the UK’s HS2 project has that support, despite large opposition. As we will see by the nations’ reaction to the ‘Boris Bridge’, any Irish Sea tunnel will struggle to get that same commitment.

Scotland

‘…We already have a bridge to Northern Ireland from Scotland…it’s called Cairnryan ferry port…’. Colin Smith MSP.

Prime Minister Johnson’s bridge announcement broke protocol because he didn’t consult the devolved nations. The Boris Bridge was then badly received by Northern Ireland and Scotland. The Scottish Transport Secretary Michael Matheson called it a ‘vanity project’(12). He wants investment in local infrastructure, such as HS2 links. Matheson is supported by Portpatrick locals and their MSP, Colin Smith who want local infrastructure upgraded(14) first.

Northern Ireland

‘Surprise and disappointment…’ Nichola Mallon MLA

Minister for Infrastructure, Nichola Mallon, also criticised the break in devolution protocol. In her response, she highlighted that local infrastructure is her priority, such as an upgraded A5 road(15).

But, unlike Scotland, there is some local support for a crossing. Echoing Macassey 130 years ago, DUP Sammy Wilson said a crossing would forge ‘…a physical and economic link’ with the union’. This shows a link is greatly desired by many in the unionist community.

Wilson also points out: ‘…I think one of the big themes of this parliament will be how you protect the union of the United Kingdom and I think Boris cannot ignore the threat to the union…’. This is an interesting political point we’ll come back to later.

England: The ignored middle child of the debate

England is the only UK nation without a devolved government. Westminster is its government and so Prime Minister Johnson can be assured of parliamentary support there. However, it’s unrealistic to expect this policy to be popular with English voters without a vision they can also buy into.

Wales: happy to fence sit

A sea crossing is not a Welsh priority. Even and Ireland-Wales link would struggle to get much support. Wales wants infrastructure investment to focus on their internal needs(16).

Isle of Man: an unlikely project

An all-weather tunnel could be a huge boost for the island. However, the permanent changes to the island would be a hard sell for the Manx government.

Republic of Ireland

‘…worth examining…’ Leo Varadkar

When former Taoiseach (prime minister) Leo Varadkar met Prime Minister Johnson last December, he was openly supportive of a study. However, as a purely UK infrastructure project, Ireland’s interest is limited. Strategically, their infrastructure concerns are an upgraded cross-border railway and — like Nichola Mallon — an improved A5 road between Derry and Donegal.

Final thoughts

In my view, any infrastructure megaproject must pass three ‘possibility’ tests:

· Is it technically possible?

· Is it economically possible?

· Is it politically possible?

An Irish sea tunnel can be built with today’s technology. It will never be economic because, as Macassey predicted in 1890 ‘…No amount of traffic likely to arise would make the tunnel a dividend-paying concern’ (17) i.e. pay for itself through revenue alone.

That leaves us with politics — the art of the possible. Here, we are discussing a tunnel’s desirability for the UK. Wanting to build a tunnel (or bridge) for political reasons such as enhancing the union is legitimate. DUP MP Sammy Wilson’s made this point — the link could strengthen Northern Ireland’s bond with the UK. But neither the Scottish nor Northern Irish governments want a fixed crossing, despite what the Prime Minister is proposing. The only government that has made supportive noises is Ireland, a third country safe in the knowledge they won’t be paying towards it!

Realpolitik makes it possible for Westminster to impose an Irish Sea crossing on the devolved nations. In my opinion, that would be unlikely because it would be highly damaging politically. Without a pan-UK consensus first, a crossing would not strengthen the union but wedge it further apart.

Without a vision that excites and unites the UK, the crossing — be it bridge or tunnel — could be so divisive it may be better left on the drawing board.