England Sank 90,000 Tons of Concrete Into a River to Build This Tunnel

England built three enormous concrete tunnel sections, floated them into the River Medway and deliberately sank all 90,000 tons beneath the water. In this video, discover how engineers constructed the Medway Tunnel using the immersed-tube method, controlled 30,000-ton concrete structures against powerful river currents and connected them underwater without allowing the river to flood the tunnel. See how the giant sections were built on dry land, made to float like ships, lowered into a prepared trench and transformed into one of England’s most impressive hidden engineering projects. Subscribe for more videos about British engineering, massive construction projects, innovative technology and the infrastructure hidden beneath the United Kingdom.