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Front Line: Digging Scottish Water's Shieldhall Tunnel

In this month's Front Line feature we meet Tom Rushe, who is part of a team of engineers working on Scottish Water's £100M Shieldhall Tunnel project in the south west of Glasgow

Tom Rushe in the Tunnel Boring Machine (Picture credit: SNS)Tom Rushe in the Tunnel Boring Machine (Picture credit: SNS)

In Context

-Tom Rushe works for the Glasgow Tunnel Partnership, a commercial joint venture between Costain and VINCI Construction Grands Projects called CVJV, which is delivering the Shieldhall Tunnel project for Scottish Water.

-When complete in late 2017, the tunnel will be 3.1 miles long, more than five times as long as the Clyde Tunnel, and 4.65m in diameter, big enough to fit a double-decker bus inside. It is being dug at depths of up to 32m, or 105 feet

-It will be the biggest wastewater tunnel in Scotland, with a storage capacity equivalent to 36 Olympic-sized swimming pools.

It’s a daily commute to work with a difference.

Tom Rushe and his colleagues are part of a team of engineers working on Scottish Water’s £100M Shieldhall Tunnel project in the south west of Glasgow - part of the biggest upgrade in the Greater Glasgow area’s wastewater infrastructure since Victorian times. When complete, the 3.1-mile long tunnel will run from Craigton to Queen’s Park and help improve river water quality and tackle flooding in parts of the city.

The men are working on a massive, state-of-the-art Tunnel Boring Machine (TBM) to build the tunnel as it travels at speeds of about 30 metres per day excavating earth and stone and installing the lining of the tunnel in the form of massive concrete rings.

Progress has been steady and the engineers have recently completed the first mile of the tunnel.
Today, like any other day, the engineers’ shift starts at 7am and will run until 7pm when they’ll be replaced by another team of men working the 12-hour nightshift. The workers follow this pattern five days a week, as the machine tunnels away, night and day.

After they arrive on site at Craigton industrial estate the men receive a briefing from the shift manager, including an overview of the type of ground they will be working in, and then head for the main entry point to the tunnel, a giant 20-metre-deep shaft.

Once they are individually checked above-ground, and given their own tally or number, they climb down four flights of metal stairs, descending into what looks like an unfinished underground railway station but is actually the entry and exit point to the tunnel and TBM, for all men, materials and equipment.

Covered by a sound-proofing roof to minimise noise inconvenience to local residents, the shaft is a vast industrial cavern which houses a small-gauge railway and is all rolling stock, cranes, ducting and pipes.
It’s the hub of the whole operation, the point through which everything passes. By the end of the project, about 250,000 tonnes of excavated material will have come out this way – more than 18,000 pre-cast concrete segments (each weighing 2.5 tonnes) will have gone in.

At the bottom of the shaft, the engineers working on the TBM board a man-rider carriage on an electrically-powered locomotive which transports them, along with the concrete segments, to the tunnel boring machine.

The locomotive also takes stretches of pipes, ducting and cable to be installed behind the TBM as it progresses slowly but steadily along its route.

The electrically-driven TBM is 180 metres long - almost twice as long as a football pitch - but just 5.5 metres in height with a long, narrow gantry running along its side. That, combined with it operating deep underground, is what makes working in such an environment extremely challenging.

At any one time, there is usually a team of about eight working on the TBM, driving or piloting it and operating equipment used to excavate material.

Another 20 support staff work behind it installing the tunnel sections (six of the concrete segments are installed to form a 1.5m-long ring) and the pipework or ducting for water and air and to transport the slurry back to a slurry treatment plant above-ground.

The support staff also use the train to bring parts, supplies and spares to the TBM.

The machine has a cutting wheel with 25 cutters at the front, which rotate as it moves forward at the speed of about two millimetres per minute.

The TBM has to lay six of the concrete wedges to create one circular ring and the teams aim to lay about 24 rings per day.

Perhaps surprisingly, it’s work that the engineers relish.

Tom, who’s 25 and from Birmingham, says: “It’s really fantastic to be working on such an important project, the first of this type and size in Scotland, which will benefit Glasgow for generations to come.

“I enjoy working in tunnels and, although it’s a challenge carrying out very technical work in these conditions, it’s one I relish and enjoy every day.

“You quickly get used to the confined space and we have everything we need down here for working long shifts – including a kitchen and toilet!

“Getting to my current ‘place of work’ is certainly quite different to what most people do every morning above ground. But I would never want a conventional office job. Building tunnels is cool and I really wouldn’t swap it for anything.”

The machine is on schedule and expected to complete its journey and emerge at Queen’s Park in the summer of 2017, after which the new tunnel will be connected to the existing network and the project completed by about the end of 2017.

Inevitably, as the tunnelling progresses and the TBM gets further along its 3.1 mile-long route, the men’s journey will also get longer. Their ‘commute’ at the moment takes little more than 10 to 12 minutes from entry shaft to the back of the TBM.

In the final stages of the tunnelling work, when the TBM is further away from the shaft where the tunnelling began, that journey will take almost 30 minutes.

Today, after another hard day’s graft carrying out work deep underground in conditions that few of us would enjoy, the workers make the same journey in reverse, taking the ‘train’ from the TBM back to the entry/exit shaft, climbing the stairs and checking out at ground level.

Just like all commuters, the engineers are delighted to get to the end of their journey from work each day and, again like the rest of us, they go home, eat and relax ….and get ready to do it all over again tomorrow.

-An accompanying video of Tom Rushe and the Shieldhall Tunnel team is available here. Video and text supplied courtesy of Scottish Water.

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