Channel tunnel or bridge?

Press, 9 February 1982, Page 17

Channel tunnel or bridge?

From

the “Economist”

The British and French Governments are approaching the deadline for a decision on how best to link island Britain to the continent of Europe. If Ministers do not give their blessing to a channel tunnel scheme by April, construction will be delayed until after Britain’s next general election — and that delay could shelve the chunnel indefinitely. Deciding which of the rival chunnel schemes to back, however, will not be easy. One criteria will be the ease with which each chunnel design can he built. Any of the three front-running schemes — European Channel Tunnel Group’s train-only tunnel. Channel Tunnel Developments’ car-and-lorry-carrying rail tunnel, and Euroßoute's • road-and-rai! bridge tunnel — will be economic, say their backers, assuming any can be built at the planned cost. Can any? Among the three schemes.

there are two different construction techniques for the government to choose from. Both the European Channel Tunnel Group (E.C.T.G.) and the Channel Tunnel Developments (C.T.D.) schemes require a tunnel to be bored underneath the channel. Conventional tunnelling machines would be used to

dig the hole, and it would be lined with reinforced concrete. The Euroßoute scheme, on the other hand, requires little conventional tunnelling — and is the only scheme that would enable people to drive between France and Britain without transferring to rail. Most of the tunnel section of this combined bndge-and-tunnel (brunnel) scheme would be made by burying prefabricated steel-and-'con-crete tunnel sections in the channel bottom.

The (relatively shallow) hole for the tunnel would be dug from the surface and, after the tunnel sections had been lowered into place and connected together, covered over again to complete the tunnel. Bridge sections would also be pre-fabricated, and laid into place on pylons to complete construction. Generally, such modular construction techniques speed construction and help avoid cost overruns. The bridge and tunnel sections could be built in existing shipyards and offshore oil-rig construction sites. Spreading

out the pre-fabrication work among various sites would reduce the chance of a single, disastrous bottleneck. There would be no need to build from scratch large fabricating facilities on the French and British coasts. Thanks to modular construction. Euroßoute’s backers reckon they could open one of the brunnel's two roadways five years after the start of construction. Its

rivals estimate their schemes would not start carrying traffic for at least seven years. Weighing against these advantages. however, are the cost and complexity of the Euroßoute scheme’. EuroRoute is planned to cost about $8 billion — much more than either C.T.D.’s $4 billion scheme or E.C.T.G.'s $l6OO million one. Euroßoute’s two roadways

would leave the British coast in l‘z miles of tunnel. The tunnel would lead to two bridges, one for each traffic direction, running seven miles to an artificial island. At the island, the roadways would spiral down through the island's interior to IP'2 miles of tunnel. This tunnel would end at another artificial island, four miles from the French coast, where the roadways would come to the surface' and join up with bridges completing the link with France. Trains would have their own tunnel. Compared with EuroRoute. the rival schemes are quite simple. Because their tunnels would run coast to coast, they would require no artificial islands. Because designed to carry only electrically driven trains, they would not require ventilation outlets to be brought to the surface in mid-channel as the Euroßoute’s roadway would. At first glance, either tunqel scheme would seem easier to build than EuroRoute's brunnel. Their

backers argue that tunnelling through the chalk underneath the channel, should be easy. And proper organisation, they say, can overcome the problems of relying on newly created building sites on the British and French coasts — despite Britain's abysmal record or organising large construction sites.

While arguments will rage over the potential earnings and relative economics of the rival schemes. EuroRoute's backers have a strong answer to critics who question their ability to build their design. They have a precedent. America's Chesepeake Bay Bridge — a similar 17‘z-mile brunnel, replete with artificial islands — was opened in 1964, four years after the start of construction. It was built more or less to the planned cost.

Whichever scheme is chosen — modular construction or not — that is the sort of record Britain’s would-be chunnel builders should be aiming for.