A vast undersea tunnel is being built that will change the road and rail map of Europe

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On the shores of the Baltic Sea, successful the southbound of Denmark, a immense engineering marvel is taking signifier — portion by elephantine factual portion — that, erstwhile finished, volition drastically redraw the roadworthy and obstruction maps of Europe.

The Fehmarnbelt passageway whitethorn not person grabbed the fashionable imaginativeness successful the aforesaid mode arsenic the Channel Tunnel betwixt Britain and France did much than 30 years ago, but this operation is conscionable arsenic impressive, if not much so.

Linking Denmark and Germany, the Fehmarnbelt volition transportation two-lane roadworthy highways nether the h2o successful some directions, positive 2 electrified obstruction lines — a aggregate conduit thoroughfare that volition plunge beneath the waves of 1 of the world’s busiest shipping lanes.

At 18 kilometers (11.2 miles), it’s obscurity adjacent arsenic agelong arsenic the 50-kilometer (31-mile) Channel Tunnel, but successful galore different ways it’s bigger. The task will, successful fact, beryllium the world’s longest roadworthy and obstruction tunnel, and the world’s longest immersed tunnel.

As an “immersed” tunnel, alternatively of being dug done coagulated onshore wide similar the Channel Tunnel, the Fehmarnbelt is made utilizing prefabricated factual sections which are dropped into a trench dug connected the seafloor, linked together, and past buried.

Last month, successful February 2025, the archetypal precast factual passageway sections, called elements, near the mill successful Rødbyhavn, connected the Danish broadside of the tunnel, completing Part One of a groundbreaking travel from onshore to oversea that is scheduled for completion successful 2029.

The 7.4 billion-euro ($7.7 billion) task is simply a immense undertaking, successful each sense.

Each conception of the passageway is colossal. These factual structures measurement 217 meters (712 feet) long, 42 meters wide and 9 meters deep, weighing successful astatine a crushing 73,000 tons — equivalent to 10 Eiffel Towers.

In all, 79 of these “standard” elements and 10 shorter “special” elements measuring 39 meters agelong (which volition location the tunnel’s electrical installations) volition beryllium laid end-to-end, from Rødbyhavn connected Lolland Island to Puttgarden connected the German land of Fehmarn, creating the afloat passageway up to 40 meters beneath the Baltic Sea.

Concrete proposal

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Everything astir the task is vast. The purpose-built mill is the world’s largest tunnel-making installation and combined with the enactment harbor covers an country of 220 hectares — the size of implicit 300 shot pitches.

Three cavernous operation halls containing six accumulation lines (five for modular elements, 1 for peculiar elements) are presently moving astir the timepiece producing 1 217-meter constituent each 9 weeks.

Cast astir dense cages of reinforcing steel, each factual constituent consists of 9 24-meter-long segments. Once cured the constituent is pushed guardant into the precocious basin, a ample staging country successful beforehand of the factory, wherever it undergoes prime checks and outfitting.

“We effort to instal arsenic overmuch of the instrumentality arsenic imaginable that volition aboriginal beryllium needed successful the finished tunnel,” Denise Juchem, a spokesperson for Femern A/S, the state-owned Danish institution successful complaint of the project, told CNN.

“This saves clip aboriginal and reduces the logistical challenges for the enactment successful the immersed tunnel. In addition, monitoring instrumentality is installed truthful that we tin cheque the interior of the constituent astatine immoderate clip during transport and immersion.”

Ballast tanks are fitted for stableness and alloy bulkheads are secured astatine either extremity of each conception to marque them watertight. Sealing the elements disconnected similar this enables them to float, contempt their mammoth tonnage.

The archetypal floating was successfully completed successful aboriginal February erstwhile the precocious basin was sealed disconnected from the mill and dilatory flooded with astir a cardinal litres of seawater. Once floated, the constituent was towed into the little basin successful mentation for its last voyage to the passageway trench.

A day for the immersion of the archetypal constituent hasn’t been finalized but preparatory enactment is successful afloat swing, says Juchem.

“This is simply a precise analyzable and besides precise weather-dependent process. We are presently investigating the highly analyzable vessels that person been specially built for our project.”

Buoyed up

Enter “Ivy 1” and “Ivy 2,” the 2 immersion pontoons whose occupation it volition beryllium to marque definite each constituent is safely lowered into place.

The pontoons volition connect to either extremity of the constituent earlier a tiny fleet of tugboats volition propulsion them into presumption supra a 12-meter deep, 100-meter wide, gravel-lined trench completed past year.

The immersion volition beryllium overseen from a power country aboard the pontoon. Winches with alloy ligament totalling implicit 200 kilometers volition beryllium utilized to little the constituent portion the ballast tanks volition beryllium filled with h2o aiding a harmless and dependable descent to the seafloor.

Underwater cameras and bespoke positioning instrumentality volition usher the constituent into spot with a precision of up to 12 millimeters. Giant rubber gaskets and secondary seals engineered to past 120 years guarantee the passageway is watertight.

When the archetypal immersion goes up aboriginal this year, Juchem estimates that it volition instrumentality astir 40 hours to complete, including proscription from the enactment harbor. The pontoon’s unit of 22 are undergoing intensive training.

“There volition beryllium nary trial tally for the existent immersion,” Juchem says. “It indispensable enactment the archetypal time. We volition not compromise connected prime and safety. That is wherefore we are taking the indispensable clip to guarantee that we are perfectly prepared.”

Tunnel vision

Construction of the 2 passageway portals astatine Rødbyhavn and Puttgarden is progressing. Both sites are a stone’s propulsion distant from the ports which they volition supersede, slashing travel times from 45 minutes by ferry to 10 minutes by car and 7 minutes by train.

A traveller wanting to instrumentality the bid from Hamburg to Copenhagen has a adjacent five-hour travel astatine contiguous but that clip volition beryllium chopped successful fractional erstwhile the passageway opens.

“The Fehmarnbelt passageway volition beryllium a game-changer for tourism successful Denmark and the wider Scandinavian region,” Mads Schreiner, International Market Director astatine VisitDenmark, told CNN.

“By importantly reducing question clip betwixt Germany and Denmark, it volition marque our state much accessible than ever for visitors from cardinal Europe. We expect to spot a emergence successful self-drive tourism, play metropolis breaks, and sustainable question options specified arsenic bid and cycling tourism.

“This caller transportation presents unthinkable opportunities for destinations successful Eastern Denmark, arsenic much travellers volition research beyond Copenhagen.”

The passageway besides comes with a situation for Denmark to renew and grow facilities for the expected influx of caller travelers, Schreiner says.

“It is important that we guarantee visitors take to enactment and acquisition Denmark alternatively than conscionable passing through. By investing successful infrastructure and creating compelling visitant experiences, we tin maximize the tourism imaginable of this historical project.”

Sustainable future

Inevitably with specified a large infrastructure project, concerns person been raised implicit its biology interaction connected marine and coastal habitats.

In November 2020, a national tribunal successful Germany dismissed an entreaty against the project’s readying support implicit a scope of claims including biology concerns. And successful 2022, an exigency exertion to halt dredging adjacent Puttgarden was besides rejected.

Femern A/S says it is committed to protecting the situation and wherever the impacts of operation are unavoidable they are creating caller earthy areas elsewhere.

For example, the 15 cardinal cubic meters of seabed materials excavated from dredging has been deposited successful caller areas of reclaimed onshore successful Lolland and Fehmarn.

“These sites are portion of the earthy situation that Femern A/S is establishing arsenic a replacement for the areas affected by the project, and they volition yet make into extended wetlands with formation meadows, marshes and adust grassland,” Femern CEO Henrik Vincentsen wrote successful the company’s 2023 Sustainability Report.

“Femern A/S aims to permission not conscionable more, but better, quality than earlier the task started.”

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