How was the bridge constructed and why?

Severn Bridge

The Construction of the Severn Bridge

When the Severn Bridge was opened in 1966 to replace the Aust Ferry, it wasn’t the first time someone had proposed building a crossing at that exact spot. In 1824, the mail coach between London and Wales was less than satisfactory, and Thomas Telford – the Scottish civil engineer dubbed ‘the Colossus of Roads’ for his road and bridge construction prowess – was tasked with designing a crossing. For whatever reason, this never came to pass, and within the next few decades the rail network took up the slack, with both the Severn Railway Bridge and the Severn Tunnel being opened before the end of the century.

 

That might have taken care of postal traffic, but as the twentieth century got underway, a new pressure made improvements essential – motor transport. The 1920s saw another attempt to get a bridge built across the Severn, and another in 1935. The latter was blocked – ironically – after opposition from the Great Western Railway Company. The reason for that opposition isn’t on record, but presumably owes much to the company celebrating its centenary, including bring the broad gauge train and the ‘Centenary’ carriages onto the network. Taking the shine off the company’s ‘super-saloon’ boat trains would potentially have been disastrous.

 

The wrangling recommenced after the Second World War, with plans for a bridge over the Severn as part of the plan for a network of trunk roads. The public inquiry at Bristol University in September 1946 went smoothly enough, but Government funding was earmarked as a priority for the Forth Road Bridge, so construction on the Severn Bridge didn’t begin for another 15 years. The plan was to charge a princely 2s 6d for all motorised vehicle crossings – pedestrians and cyclists went free – in order to recoup the construction costs over time.

 

The design contract went to Hyder Consulting, a company which could trace its roots back to the early 18th Century to John Taylor and Sons, and which is now part of Arcadis NV. Interestingly enough, the company had also been responsible for the Forth Road Bridge (which opened in 1964), and for the Sydney Harbour Bridge thirty years previously. The build contracts for the sub and superstructure were split, the former going to John Howard & Co. and the latter to Associated Bridge Builders Limited, a joint venture of three firms, Sir William Arrol & Co., Dorman Long, and Cleveland Bridge & Engineering Company.

The task of constructing the Severn Bridge was enormous; aerial views from 1962 of the work in progress from the Beachley side in Gloucestershire show little more than site-clearing and cranes. It’s not until December of that year that the bridge starts to look like a bridge, with a 600 foot roadway out from the shore for engineers to start work on the Welsh end. By August of the following year, the support towers were under construction, and just over a year later, most of the roadway was in place – notably, the bridge was lit up after dark to enable round the clock work. Taking a trip on the Severn ferry during the construction period must have been a combination of fascinating and alarming, especially if a crossing coincided with one of the road deck sections being lowered into place! Although officially opened by Queen Elizabeth II on 8th September 1966, a group of teenagers did beat her to it, managing to gain access to the bridge just a few hours earlier.

 

For thirty years, the bridge carried the M4 motorway, until the second Severn Crossing opened further south, taking a path close to that of the railway tunnel below the river bed, in place since 1886. During its 40th year, a corrosion check on the suspension cables led to immediate restrictions on heavy goods vehicles, which are now restricted to one lane only. Not all deterioration has been entirely age-related – weight of traffic led to weaknesses as early as the mid-1970s, with strengthening and resurfacing work taking place in the late 1980s to compensate for the ever-increasing tide of traffic. Perhaps the last issue of controversy is the “tax on entering Wales”, since single-side tolls were introduced in the early 1990s. Tolls are £6.70 as of the beginning of 2017, with plans for a two-stage reduction proposed by former Chancellor George Osborne still in place. Cyclists and pedestrians, however, still travel free.

The freelance quantity surveyor provides construction estimating services and construction templates.

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