“Hamburg-Mitte-Elbe Tunnel” by Anita Janda, 2019. CC4.0 wikimedia. Included with appreciation.

Ten years to plan, nine years to build, seven billion to budget: the Fehmarnbelt Fixed Link Tunnel will offer an alternative to a 45-minute ferry between Germany’s Fehmarn island and Denmark’s Lolland isle. The new tunnel will clock travel time to ten minutes by car and seven minutes by train. Not just a faster trip between islands, Fehmarnbelt will reduce passage duration between Copenhagen and Hamburg.

Fehmarnbelt Fixed Link Tunnel will shorten the travel time between Copenhagen and Hamburg. Image: “Fehmarn bridge” by Bowzer. CC by SA 3.0, wikimedia. Included with appreciation.

It will be the world’s longest immersed tunnel, although at 11.1 miles long (18 kilometers) shorter than the Channel Tunnel stretching 31 miles (50 kilometers). Other differences include construction methods. The Channel Tunnel was built using a traditional boring machine. Fehmarnbelt will be pre-fab: tunnel sections completed on land will be submerged and then connected. Each section is 711 feet long (217 meters) – about half the size of a large container ship. All that length is heavy – each section weighs as much as 13,000 elephants.

One section of the tunnel’s pre-fab building blocks weighs as much as 13 elephants. Image: “Elephant,” by Felix Andrew, 2005. Public domain gnu. Included with appreciation.

In a world where the environment is part of every decision, Fehmarnbelt Fixed Link will include newly established stone reefs on both Danish and German sides, similar in some ways to the natural paths fashioned along the New River of England. Tunnels offer other environmental advantages, bringing automobiles, trains, and trucks below the surface where emissions be captured, if the tunnels are so equipped.

SMART Tunnel in Kuala Lumpur, Malaysia, combines transport and flood control. Image: “SMART tunnel entrance,” by David Boey, 2018. Wikimedia CC4.0. Included with appreciation.

Another environmental advantage of tunnels is response to flash floods. The Stormwater Management and Road Tunnel (SMART) in Kuala Lumpur, Malaysia, is designed to divert rainwater into a lower section, allowing the upper section to remain open to vehicular traffic. Floodwater diversion, storage, and reuse options are certain to present problems (and opportunities) in our future: can tunnels be part of the solution?

Thanks to Cherie E. Potts for suggesting this post, and to Frank P. Davidson for proposing and achieving the success of the Channel Tunnel.

Fehmarnbelt Fixed Link. “Why we’re building the Fehmarnbelt fixed link.” Femern. https://femern.com

Prisco, Jacopo. “Denmark and Germany now building the world’s longest immersed tunnel.” September 2022, CNN.com. https://www.cnn.com/travel/article/fehmarnbelt-longest-immersed-tunnel-cmd/index.html

SMART. https://smarttunnel.com.my/smart/what-is-smart/

Building the World Blog by Kathleen Lusk Brooke and Zoe G. Quinn is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Un