Severn Crossings

Year:1886, 1966 & 1996

Duration:13, 5 & 4 years

Cost:Unknown, £8m & £350m

Country: Wales, UK

What did this project achieve?

Build a crossing between England and Wales to cope with increasing demands

Bridges over the Severn

1966: The Severn Bridge, a motorway suspension bridge that crosses the rivers Severn and Wye between Aust, in south Gloucestershire and Chepstow in Monmouthshire.

It took 3.5 years to build and was opened by the Queen in 1966. It replaced the Aust ferry. But by the 1980s traffic levels had tripled.

1996: Second Severn Crossing, 30 years on, built to relieve traffic congestion on the original Severn Bridge. Drivers pay a toll (fee) as they cross into Wales.

Severn tunnel

1873-86: Built by the Great Western Railway (GWR). The construction team was headed up by civil engineer Sir John Hawkshaw.

At just over 4 miles long (7,000m) it was the longest railway tunnel in the UK until 2007 when the Channel tunnel rail link with its 2 high speed tunnels opened. It was the longest underwater tunnel in the world until 1987.

Difference the crossings have made

The Severn tunnel

It considerably reduced journey time by rail when travelling from England into Wales. Before the tunnel was built crossing the Severn in this area meant a ferry journey or a long detour via Gloucester. It takes less than 4 minutes to go through the tunnel. Construction started in 1873.

Severn Bridge

Over 100 years later the Severn bridge made it much faster to cross into Wales by car. As early as the 1920s traffic congestion was rising on roads approaching the area. After several false starts and some issues with funding the bridge opened in 1966 – decreasing congestion and making it faster to travel from England to Wales.

Second Severn Crossing

It's now the main road link between England and Wales and used by more than 80,000 vehicles a day. It has won numerous construction industry awards.

How the works were done

Severn tunnel

With over 2 miles of the tunnel being dug below the river flooding was a constant challenge for engineers working on the tunnel.

In October 1879 with only 130 yards (130m) to go to the Monmouthshire side water flooded the works. The water was fresh, from the Welsh side. The source became known as 'the Great Spring'.

Diver Alexander Lambert was sent down a shaft and 300m along the tunnel to close a watertight door and seal off the waters. Lambert used recently-patented rebreathing equipment invented by diving engineer Henry Fleuss. The Great Spring also flooded in 1883 with Lambert again called in to help seal it off.

Steam-driven pumping engines were used to pump out the Great Spring and other waters until the 1960s when they were replaced by electric pumps.

Severn Bridge

The bridge is 1,600m long with a 988m span between the towers and 2 x 305m side spans. It was the first pioneering use of lighter, steel box girders to provide the deck.

Unlike most suspension bridges the cables carrying the deck are not vertical but arranged in a zig-zag style. Engineers used this arrangement of cables to reduce vibration.

'Stockbridge dampers' were also used to reduce vibration. The dumb bell-shaped devices suppress vibration caused by wind on overhead power lines by dissipating energy.

Engineers decided on the shape of the bridge after extensive wind tunnel testing.

Much of the structure was built in Chepstow with sections floated down the river to the construction site and then hoisted into place.

Second Severn Crossing

Work started in 1992. It's a viaduct with a central 1,000m cable-stayed section. Total length is 5km.

Sections of the bridge weighing 200 tonnes each were moved from the shore using a large tracked vehicle, loaded onto a barge then floated out at high tide. These sections then had to be lifted in position using a heavyweight crane barge.

"​‌

A supreme achievement for British engineering… a thing of beauty

British Pathé News

on the opening of the Severn bridge in 1966

Fascinating facts

Great Western Railway (GWR) built houses for Severn tunnel workers during the project. As chief contractor Thomas Walker was a deeply religious man. GWR also built a mission hall to hold 250 worshippers and a Sunday school.

To speed up work on digging the Severn tunnel Walker ordered 10 hour shifts spent entirely underground, including meal breaks. Tunnel workers went on strike in protest. In response, Walker ordered surface workers to down tools. Afraid of losing their jobs the strikers went back underground the next day.

The Severn Bridge has always been a toll bridge. In 1966 the charge for a car to cross was 2 shillings and 6 pence – known as half a crown and worth about 12p today. By 2017 the charge was £6.70.

The Second Severn bridge was the longest river crossing in the UK when it opened in 1996. It has been designed to withstand an earthquake or a ship crashing into it.

All bridge tolls (fees) are to be scrapped at the end of 2018 and both road bridges will return to public control.

People who made it happen

  • Severn tunnel designer: Sir John Hawkshaw.
    Builder: Great Western Railway.
  • Severn Bridge consulting architect: Sir Percy Thomas.
    Builder: Associated British Builders
  • Second Severn Crossing: Project director: Norman Haste
  • Chair: Sir John Armitt, Chairman of the Laing/GTM joint venture
  • Consultant Ronald Weeks, Percy Thomas Partnership
  • Contractor: Anglo-French consortium Laing-GTM

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