How the Severn Tunnel brings beer, diving and the Oasis together

Its seeping water is in your beer, it’s where the Oasis classic was born and where one of the first dives took place.

It is also one of the most hostile places to put a railway line.

The Severn Tunnel draws water from more than 20 Olympic-size swimming pools every day – some of which is used in drinks such as Budweiser and Stella Artois, which are brewed just a few kilometers away.

You’d be forgiven for not knowing just how difficult it is to make a train journey when traveling between Wales and England on this engineering marvel deep below the UK’s longest river.

It was once the world’s longest underwater tunnel, a structure that took 13 years to build by hand — using picks, shovels, drills and dynamite — nearly 140 years ago.

It’s a place where you feel like it’s constantly drizzling – and it’s the constant seepage of salt water from the river above that makes it the most inhospitable environment a railway line has.

When it gets dark outside for three minutes and 40 seconds while driving through a tunnel at 120km/h on one of Britain’s busiest rail routes, connecting London and Bristol to South Wales, most people forget all about the work that went on. they did to keep themselves moving.

It is the deepest part of the UK’s 22,000-mile (35,000 km) railway network, and more railway track is replaced than any other due to the extremely corrosive salt water atmosphere almost 50m below sea level.

That is why the Severn Tunnel is currently there closed for the longest time – different than when it was electrified a few years ago – since its opening in 1886.

Normally, about 200 trains per day pass through the four and a half mile (seven kilometre) structure each day.

Not at the moment though, as engineers have shut it down for 16 days until July 19 to restore the submerged line to south Wales and replace all 66 rails, 10,800 sleepers and 22,000 tonnes of gravel that support the track.

“Water ingress, diesel fumes from the trains and the aggressive nature of the minerals in the tunnel are attacking the tracks so we now have to renew the line every five years,” said Network Rail’s Brian Paynter.

“The sleepers and ballast are replaced every 15 years. It’s probably the fastest renewal of any rail in the UK because of the hostile environment.”

Outside the Severn Tunnel, track is usually replaced every 25 to 30 years.

Although 76.4 million bricks – often 10 layers deep surrounded by 1m (3ft) of rock – hold back the tide from one of the most famous stretches of water, the Severn still seeps through the tunnel lining.

Keeping the tunnel dry – under a fast-flowing river with the third-highest tidal range in the world – has been a challenge since digging under the Severn estuary began in 1873.

It was only the second attempt at an underwater tunnel – but it was more than 13 times longer than the first, the 400 m (1,300 ft) Thames Tunnel in London, which opened in 1843.

In Victorian times, there was no laser-guided radar equipment or tunnel boring machines capable of constructing this feat of engineering.

It was all blood, sweat and tears with a lot of geology and math plus some trial and error.

“Engineers were made of something else in those days,” Mr Paynter added.

“I can only imagine how difficult it was, no computers, no phones, no lasers, no sonar – they did an amazing job and 150 years later it’s still going strong.”

The tunnel and its approaches are about seven miles (11 km) long, so the track can drop almost 450 feet below the Severn’s lowest point, but make sure the grade is gentle enough for express trains to pass through.

The work was arduous and slow, with pumps pumping out all the water – but disaster struck six years into the construction when the excavators hit an underwater spring.

Workers were less than 119 m (400 ft) from joining the two tubes when the tunnel first flooded in 1879.

Construction was delayed for more than a year and could only resume after Alexander Lambert made one of the first dives in history using Henry Fleuss’s newly developed self-contained rebreather apparatus, which allowed him to close the watertight doors.

The Chief Engineer of the Great Western Railway, Sir John Hawkshaw, also ordered the spring sealed and rerouted the tunnel’s path below to avoid further problems.

Flood water broke through the tunnel several more times, notably in 1883 and 1885, so engineers installed larger permanent pumps on the Welsh side.

But to this day, these huge pumps work 24/7, pumping 20m gallons of water out of the tunnel every day – some of which goes into your pint.

The tunnel cut the journey time between Bristol and South Wales by about an hour – and was the fastest way you could cross the estuary before the first Severn road bridge opened in 1966.

Until 1987 it was the longest underwater tunnel in the world and for over 100 years it was the longest mainline railway tunnel in the UK.

But keeping it running and reducing delays is a huge task that requires constant attention – and each work program takes five years to plan and starts as soon as the previous cycle ends.

Yet one delay under the tunnel in the 1990s gave Noel Gallagher time to write one of Oasis’ most popular songs and a British anthem of the 1990s.

Acquiesce, a fan favorite and 15-year regular on the Oasis setlist, had his musical beginnings under the sea between England and Wales.

“I wrote that song on the train on the way to Loco Studios in South Wales for the Definitely Possible sessions,” Oasis songwriter Noel Gallagher once said.

“I was alone. I was stuck in the Severn Tunnel and I had my acoustic guitar. I was like ‘give me the guitar, what does the word Acquiesce mean?’

The tunnel was closed for 10 days last year for a track replacement, this year it is closed for 16 days for similar round-the-clock works which will cost around £10 million.

Water collection drains were added to the tunnel crown to minimize saltwater dripping onto the tracks.

Ventilation fans have also been installed to create a constant breeze that helps make the environment kinder to steel rails and electrical wires.

Each of the 66 lengths of new rail track, which will be installed this July, is larger than two football pitches at 215m (705ft) long and costs about £14,000 each.

Around 10,800 concrete sleepers will also be replaced, costing £90 each.

“There are skeptics who say you are blocking the railway again,” added Network Rail’s Mr Paynter.

“But I’m doing it for the greater good, to ensure a more resilient and secure network. This is a temporary period of disruption, but if we don’t change course, everything will expire. It’s a short pain for a long gain.” “