It will be a groundbreaking moment when HS2’s 1,600 tonne tunnel boring machine (TBM), Mary Ann, successfully completes the 3.5-mile underground drive to link the North Warwickshire village of Water Orton to the northeast Birmingham suburb, Washwood Heath.
The team is just days away from realising its goal, and HS2 is hailing the achievements of the 450 men and women who have each played a role in one of the most complex tunnelling operations on the entire HS2 network.
The mission, led by HS2’s West Midlands contractor Balfour Beatty VINCI, has taken years of meticulous planning. Tunnelling director, Jules Arlaud, knew it would require pinpoint precision, flawless preparation, and a highly committed team to safely navigate the giant machine under the M6, past key National Grid infrastructure and the River Tame without disruption.
The team has spent 649 days and nights onboard Mary Ann, working up to 40 metres below ground, and is now on the final straight towards the epic breakthrough moment.
When BBV’s first giant tunnelling machine arrived from Germany, Arlaud was mobilised to the West Midlands. He already had a string of successful worldwide missions under his belt and his next challenge was to join—and eventually lead—the team responsible for constructing two of the five twin-bore tunnels on the HS2 network.
The completion of London’s new super sewer – Tideway – gave BBV access to an experienced tunnelling workforce. But the stop-start nature of major infrastructure projects in the UK meant the pipeline of homegrown talent simply wasn’t in place in the numbers needed. Recruiting and upskilling local people, in partnership with Solihull-based Rorcon and Tunnelcraft, would be pivotal to the success of BBV’s tunnelling programme.
Navigating the 125-metre-long TBM is no mean feat. The crew must work together to ensure the machine cuts through the earth, whilst simultaneously reinforcing the excavated tunnel with over 20,000 individual concrete segments – each weighing up to seven tonnes.
At peak production, the TBM advanced at around 30 metres per day, lining the tunnel with segments to form precision-placed concrete rings. As the cutterhead rotates, excavated material is extracted and mixed with slurry. The solids and liquid are then separated at an on-site slurry treatment plant.
The treatment plant is where most new starters learn the ropes and is where 21-year-old Dylan Kehoe works alongside his dad, Greg. The father and son duo from South Wales moved to nearby Minworth to work on HS2, and Dylan’s proud to be following in his dad’s footsteps.
Dylan was recruited by Solihull-based Rorcon, as part of the drive to upskill a new generation of tunnellers. After an initial stint as a labourer, the company supported him to achieve his Level 3 Supervisor NVQ, enabling Dylan to climb the ladder to treatment plant operative. The experience has left him hungry for more. “If you work hard, the progression opportunities are there. I’ve worked my way up from being a labourer and hope to progress into mining next, so I can work on the tunnel boring machine.”
There’s no glamour in tunnelling. Whether onboard the giant moving factory, or supporting the machine’s drive from the rear, the team work long hard hours. Seven 12-hour shifts are rewarded with a three-day break, then it’s another stint of 7/12s before a long awaited four-days off. It’s not for the work shy.
Around one million tonnes of spoil will be excavated during Mary Ann’s 3.5-mile drive, and those at the back of the operation are just as integral to the machine’s daily advance. Teamwork and superstition are at the heart of every tunnelling operation, from naming the machines after notable local women (Mary Ann takes her name from the Warwickshire-born writer, better-known by her pen name George Eliot), to the religious ceremony that takes place to bless the machine and the safe return of its crew.
Back at the treatment plant, Greg Kehoe keeps a watchful eye from the control room. During his 40-year career, he’s worked on some of the UK’s biggest tunnelling projects, from Crossrail to Tideway. With his lad, Dylan, and Erdington-based new recruit Edward East– who quit a career in the RAF to retrain and work on HS2 – the trio work in sync to keep pace with the TBM’s miners.
Every tonne of excavated earth is compressed to extract the groundwater, and not a drop is wasted. Recycled slurry is pumped to the front of the giant digging machine to maintain ground pressure, while the excavated material goes back to the treatment plant and through the slurry circuit.
The solid material is repurposed too. Men and women wait in the bays with excavators, shovels and dumper trucks. They transport the earth along specially constructed haul roads, so it can be reused elsewhere on the HS2 route. The whole operation runs like clockwork – most of the time.
“The toughest bit’s keeping pace with the mining,” explains Greg. “It’s a balancing act to keep the water tanks at the right level, so we’ve got the volume we need for the machine. Too much, or not enough is never a good thing.”
The trio monitor the vast network of machinery that controls the pressing, dilution and pump process, and are in constant contact with the TBM team underground. The miners need to know the water’s coming and rely on Greg’s analysis of the ground conditions.
With everything running smoothly, Mary Ann’s giant hydraulic jacks push her forward.
A team of 16 work the TBM and 61-year-old Pit Boss Steve Rocke, is the man in charge underground. He wears a black helmet, pointing him out as the gaffer. And he’s earned it, after 43 years on the job. This will be his last assignment. The light at the end of the Bromford Tunnel will see Steve return to his family in Hull, and his beekeeping hobby.
There’s a rank and file onboard the TBM. The lead miner and pilot dictate the drive and even behind safety glasses, the responsibility shows in their eyes.
Pilot, Harsh is from Kolkata. He stands in the control room, his eyes affixed to a series of screens that show the cutterhead in action. He’s driving the 1,600 tonne machine under the meandering River Tame for the fourth and final time. Just five metres of ground separate him and his crew from the riverbed.
Harsh works in tandem with the lead miner. They share their tiny office space with three crew members who monitor the technical and mechanical side of the drive. If the cutterhead needs repairing or maintaining, one of the miners must enter the excavation chamber to fix it. “It can be like working inside a balloon,” says Steve. “So, we calculate to the second how long they’ve got.”
Air pressure levels inside the tunnel will determine whether a hyperbaric intervention is required on the miner’s return - a medical treatment that requires breathing in pure oxygen from inside a pressurised chamber.
This is high-risk stuff, and Tunnel Agent, Josh Knight is bestowed with that responsibility. He’ll assess the miner’s safe working time and calculate how long he must spend in the decompression chamber afterwards. From the mini submarine-like space inside the TBM, the miner must inhale pure oxygen to avoid the painful decompression sickness, known as the bends.
“Hyperbaric interventions don’t happen often”, explains Josh. “Thankfully, we’ve only had to do it once so far on this mission.”
Ring builders, miners and grouters scurry along the metal stairwells and corridors. Excavating the ground is just one part of the job, Mary Ann must also build the tunnel. Gary Jones and his two-man team dictate the installation of 20,000 concrete segments that line the tunnel walls. It’s Gary’s ninth year tunnelling, and Bromford is his first job away from his North Wales homeland.
Crane operators lift and load the huge concrete segments onto an electric vehicle (EV) which is driven into the tunnel, and Gavin Davis from Doncaster is the man at the wheel. Years of experience have earned him the accolade of being the only driver that can manoeuvre the 16-wheel EV in a three-point turn. It’s a badge of honour the team has bestowed upon him, and he wears it with pride.
When’ Big Gav’ arrives with another haul of segments, Gary and his crew lift, shift and lock them into place. Their objective is to create a series of interlocking rings. “On a good shift, we’ll build five or six complete rings,” explains Gary. Barely a dent in the 2,971 required.
The grout, which seals the segments into place, is made at the onsite batching plant and local lad, Jevon Lynch, is hard at work inside. The Tunnelcraft apprentice, recruited at a HS2 careers fair, was rewarded with a permanent job running the grout batching plant after passing his Tunnelling NVQ. “I’ve done a bit of everything in my two-year apprenticeship, from helping to build to the TBM to working with the crew onboard. Getting a permanent job sets me up for a career in the industry, which is exactly what I need with a baby on the way.”
It’s now 649 days since take off and the team is painstakingly close to the 3.5-mile finish line. The final approach will be slow. The cutterhead must slice through a 2.85 metre concrete wall for Mary Ann to emerge at her final destination – Washwood Heath, Birmingham. With sensors tracking her every move, the team above ground can pinpoint when the breakout will begin.
As the big day edges closer, the team calculate their chances of being on shift for the final drive to bring Mary Ann home. Their global expertise is staggering. The men and women behind the operation represent 45 different nationalities, and each of their country’s flags will be waved with pride as they watch their mission draw to a close. When the machine stops, the miners onboard Mary Ann will be given the ultimate honour of stepping out on to the cutterhead to mark their victory.
History will be made. Bromford Tunnel will be the longest railway tunnel in the West Midlands - a defining moment for the UK’s expanding railway network. And in the not-too-distant future, the tunnel will be used by millions of passengers travelling to Birmingham’s new terminus station - Curzon Street – just two miles away.
But it’s not quite the end for our tunnelling heroes. Tunnel boring machine, Elizabeth is already hard at work on the second drive of the Bromford Tunnel. Her breakthrough is expected later this year.
