Construction of the Channel Tunnel was the realisation of a 200-year-old dream to connect England and France, and has been described as the civil-engineering project of the twentieth century.
The 63-month Anglo-French construction project included a 50km triple-bore tunnel, 39km of which is undersea – making it the longest undersea tunnel in the world.
Tunnel-boring machines (TBMs) worked simultaneously from the French and English sides through a single chalk stratum, at an average of 45m under the sea floor. The TBMs for the 4.8m-diameter service tunnel met in 1990; TBMs for the main tunnels met in 1991.
The tunnelling operation saw 8,000,000m3 of soil excavated at an average of 2,400 tonnes an hour. Much of the excavated soil on the English side was used to reclaim land near Folkestone, which is now a popular park.
The twin 7.6m-diameter running tunnels linking to the 4.8m service tunnel were driven in just over three years under stringent safety criteria.
The construction consortium TransManche Link included UK contractors Balfour Beatty, Tarmac, Costain, Taylor Woodrow and Wimpey.
Despite the fact that the project ran 80% over budget with an estimated final cost of around £10bn, no-one would argue with the awesome magnitude of the undertaking or the challenge of bringing it to fruition.
Not least given the project was completely abandoned once, a decade earlier when prime minister Harold Wilson found the then £1bn project unaffordable.
“In the waning afternoon light of 20 January, the Channel Tunnel died,” NCE said in January 1975. “It was killed by a Labour Government which found it economically impossible to justify financing, even at reduced cost, the necessary high speed rail link between London and Dover.”
The death warrant was signed just 16 hours before the permanent service tunnel drive was due to start.
But the project was revived and tunnelling finally got going 13 years later in summer 1998. Mott MacDonald consultant Alan Powderham saw it all, and says it still feels like yesterday when the attention of the world was on him.
“For me it was an amazing engineering adventure and was a watershed opportunity,” he says, citing the design and build nature of the project as a “huge opportunity” to work closely with a contractor. “That has always been a driving passion of mine,” he says. “It is a key way of introducing appropriate innovation.”
Innovations on the Channel Tunnel included significant use of the observational method. “Some have described that as a renaissance of the observational method,” says Powderham. “And that was only made possible by a wonderful team and close relationship with the client.”
The tunnel was formally opened in May 1994 with freight and passenger services beginning operations in the summer. Operator Eurotunnel has since suffered massive losses on the project, citing a lack of business, high access charges and massive debt, which causes a heavy interest-payment burden. Three major fires have also seriously hampered operations. This has discouraged investors from looking at a second Channel Tunnel.
However, passenger numbers on the Eurostar service have risen steadily to 9.5 million in 2010, with cars, trucks and coaches using Le Shuttle close to 3.8 million.