CNN  — 

At the western edge of Europe lie two little islands with a complex past.

Ireland and Britain are just 12 miles apart at the Irish Sea’s narrowest point, but waters run deep here – in every sense.

For the past century, Ireland’s northeast corner has been part of the United Kingdom of Great Britain and Northern Ireland.

In a bid to improve domestic transport links, the UK government is now conducting a feasibility study to see whether Northern Ireland can be linked by a bridge or tunnel to Scotland, its neighbor over the water. The findings are due later this summer.

The idea is not a new one, but it’s been gaining traction since 2018, when UK Prime Minister Boris Johnson gave the bridge concept his support, and Scottish architect Alan Dunlop unveiled his proposal for a rail-and-road bridge between Portpatrick in Scotland and Larne in Northern Ireland.

More recent arguments – dubbed “sausage wars” – between the European Union and the UK over trade links disrupted by Brexit have added a fresh impetus to the search for a way to create a frictionless route across the water.

The distances involved are short. However, there are geological and environmental challenges so immense this would be one of the most technically ambitious projects in engineering history. There are also questions of economics, infrastructure and entrenched local politics.

The Westminster plans have met with scepticism from local politicians, with Scotland’s First Minister Nicola Sturgeon describing it as a diversion from “the real issues,” while in Northern Ireland, Sinn Féin Deputy Leader Michelle O’Neill called it a “pipe dream bridge.”

Now isolated in Europe, the UK today has a reputation more for burning bridges than building them. However, if it pulls this project off, it could be a wonder to rival the Golden Gate Bridge or the Channel Tunnel. The question the upcoming report must answer is: Can a fixed sea link be done – and is it worth it?

Bridge over troubled water

The Giant's Causeway on the Antrim coast is Northern Ireland's most visited tourist attraction.

The unique geology of this corner of the world is seen to spectacular effect in the Giant’s Causeway, a Northern Irish UNESCO World Heritage site, and its Scottish counterpart Fingal’s Cave. Legend has it that the countries were once linked by a bridge made of these basalt columns created by ancient volcanic lava flow.

But deep below the surface of this narrow sea you’ll also find Beaufort’s Dyke, a huge 50-kilometer-long natural trench created during the last glacial period. Its average depth is around 150 meters, but at its deepest point, it’s about twice that – enough to submerge the Eiffel Tower.

This dyke lies slap-bang on the most direct route between Scotland and Ireland, and what’s more, it’s the largest known British military dump. There are more than a million tons of unexploded munitions here, as well as chemical weapons and radioactive waste, jettisoned by the UK Ministry of Defence between World War II and the mid-1970s.

On top of this, there are rough seas, strong currents, and the famously unpredictable Irish and Scottish weather. The munitions are the first challenge to the fixed sea link project.

The clearance operation

It’s “a considerable clearance campaign,” says David Welch, managing director of bomb and explosives disposal experts Ramora UK: “not impossible, but incredibly challenging.”

He compares the project to trying to recover the most famous product of Northern Ireland’s shipbuilding industry: “It’s a bit like raising the Titanic.”

On an average offshore project, clearance teams might deal with anywhere between one and 10 large munitions a day – so the bill for clearing the trench would run to “many, many millions of pounds” before any construction work could take place.

“We have very strong currents around there,” says Margaret Stewart, a marine geoscientist from the British Geological Survey. The precise location of the munitions aren’t known, as many have been swept north along the seabed, and others never made it to the dyke at all, having been dumped ahead of target by crews cutting corners.

If you’re putting in the foundations for a bridge or tunnel, says Welch, “you need to be confident that the area in which you’re about to place equipment or assets or people is sufficiently clear to allow the safe mooring or positioning of the vessels and everything else.

“What you don’t want is to clear an area around the bridge, only for it to over time have migrated munitions move up against the base of the bridge.”