Immersed in Marvel: New Tyne Tunnel Showcases Industry Innovation

This article describes how tunneling under the River Tyne in the United Kingdom has a history that goes back to the 1950s, when a pedestrian and bicycle crossing was created to provide workers with better access to jobs in the shipbuilding industry on both banks of the river. The original Tyne tunnel, which was used by more than 16,000 travelers per day soon after it opened in 1951, was followed with a vehicular tunnel that opened in 1967 and was considered an engineering feat at the time. With approximately 36,000 vehicles traversing the existing vehicular tunnel each day, exceeding its designed capacity by more than 30%, a second tunnel is needed to alleviate congestion and create favorable conditions for public transport links. A new engineering marvel, incorporating some of the most innovative tunnel-design techniques known in the business today, is now under construction. Scheduled for completion in December 2010, the $171 million project is being executed under a 30-year design-build-finance-operate-maintain concession financed and developed through a public-private partnership with concessionaire TT2 (Tyne Tunnel 2) Ltd. The concessionaire is responsible for operating the tunnel until 2037 and for refurbishing and operating the existing auto tunnel as well as the pedestrian and bicycle passage. Once the new tunnel is complete, the old one will be closed to traffic, refurbished and reopened in late 2011. Ultimately, one tunnel will handle all southbound and the other will carry all northbound traffic. The new tunnel will be only the second immersed tunnel in all of England, the other being the River Medway Tunnel in Kent. Linked at either end to deep cut-and-cover tunnel sections, the northern approach will be 1,050 ft long and the southern approach more than twice that, 2,700 ft. The fact that the northern approach tunnel crosses over the existing tunnel with less than 10 ft of clearance presented one of the greatest engineering challenges, since the weight of the ground above had to be temporarily removed, posing the risk of heave of the existing tunnel due to unloading.