The construction site of the Colne Valley Viaduct for the HS2 high-speed rail project, on November 23, 2023 in Denham, northwest London (AFP/Justin TALLIS)
The Colne Valley Viaduct, under construction around thirty kilometers northwest of London, traces a gentle curve over several lakes. An exceptional work of art, it is one of the most advanced of the very ambitious (and very expensive) HS2 high-speed rail line.
“The architect wanted the viaduct to look like a pebble ricocheting on the water. This forced us to face major technical challenges, particularly in terms of the construction of the piers” of the bridge over the lakes, explains to the AFP Daniel Altier, project director for Bouygues Travaux Publics.
Above the viaduct under construction, the gigantic red launching beam, a sort of horizontal crane, comes to place one after the other the concrete sections of the bridge, manufactured a little far away in a specially built factory. Out of 1,000 deck segments, more than 600 are in place.
“There have been a lot of efforts to minimize noise and ensure that the viaduct is completely integrated into the water,” describes Mr. Altier. “Obviously compared to a much more basic viaduct this increases the cost per kilometer.”
The French construction giant is at the head of a consortium of companies responsible for carrying out this 3.4 kilometer work, which will be the longest railway bridge in the country, but also a 16 kilometer tunnel which will pass under the protected area of the Chilterns.
This is the section “the most advanced among all the HS2 project contracts”, argues the French group, which highlights a project whose scale “defies the imagination”.
The construction site of the Colne Valley Viaduct for the HS2 high-speed rail project, on November 23, 2023 in Denham, northwest London (AFP/Justin TALLIS)
Generally speaking, HS2, the country’s second high-speed line after the one to the Channel Tunnel, is a project that has seen a very big picture, in a country lagging behind its European neighbors in this area.
The line was designed to run trains faster and more frequently than elsewhere (even if the initial ambitions were lowered), while being more respectful of local residents and the environment – which translates in particular by more expensive tunnels.
– Amended project –
“Here, we do not flout the environment, planning law, the authorities and local populations,” said Jon Thompson, president of the public company HS2, at the start of the year.
Construction of the Chiltern Tunnel for the HS2 high-speed rail project in West Hyde, on November 23, 2023 in northwest London (AFP/Justin TALLIS)
The fact remains that these ambitions have a price which, added to the consequences of Covid and inflation, have increased the bill for a highly contested project.
It is one of the world’s most expensive rail projects per kilometer, according to economic growth charity Britain Remade, which compared infrastructure projects in 14 countries.
So much so that Downing Street recently cut the route twice to reduce costs. Designed to bring London and the major cities of the north of England closer together, the project will now stop in Birmingham – a far cry from Manchester and Leeds.
But even this severely reduced version will cost 45 to 54 billion pounds (52.2 to 62.6 billion euros) according to the government’s latest estimate (which does not take into account inflation since 2019), much more than the 37.5 billion pounds envisaged in 2013 for the entire route.
Construction of the Chiltern Tunnel for the HS2 high-speed rail project in West Hyde, on November 23, 2023 in northwest London (AFP/Justin TALLIS)
At the exit of the tunnel under construction, the ballet of small trains on tires will feed the two tunnel boring machines in voussoirs (the curved elements of the tunnel lining) of concrete, 14 kilometers further.
The complex built by Bouygues, which includes the tunnel and the viaduct, has also seen its price rise, from 1.2 billion pounds initially to around 2 billion today.
It will be “very beautiful” and “in the long term the line will only be better”, according to Ben Hopkinson, researcher at Britain Remade, interviewed by AFP.
But wanting only the best when the country has “no real experience in building high-speed lines for decades (…) is a bit ambitious”, he euphemizes.
The end of work on the section of the Colne Valley Viaduct and the Chiltern Tunnel is scheduled for November 2025. But trains will have to wait to set off until the entire line is completed, between 2029 and 2033, according to the latest timetable in date.
© 2023 AFP
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