HS2’s tunnel boring machine (TBM), Mary Ann has reached the halfway point on its 3.5-mile journey to create the Bromford Tunnel into Birmingham.

This 1,600-tonne machine has so far excavated and constructed 1.75 miles of tunnel, starting from Water Orton and heading towards Washwood Heath in Birmingham.

HS2’s tunnelling into Birmingham reaches halfway point © HS2 Ltd

The TBM began its work last year and is currently operating approximately 40 metres underground. Having already passed beneath the Park Hall Nature Reserve and the River Tame, it is now tunnelling under Castle Vale.

The machine is set to continue its journey adjacent to and beneath the M6 motorway, with the breakthrough at Washwood Heath expected early next year.

Jules Arlaud, Tunnelling Director for Balfour Beatty VINCI said:

“Reaching the halfway point on this complex stretch of the HS2 route into Birmingham is a great milestone for our 180-strong tunnelling team. We’re looking ahead now to delivering the final stages of tunnelling, and celebrating the breakthrough of both TBMs at Washwood Heath next year.”

A team of skilled tunnellers has been working around the clock to manage the TBM, which excavates the tunnel and installs concrete segments as it progresses.

The completed tunnel will consist of 2,971 concrete rings, formed by 20,797 segments. The construction’s halfway point is marked by a 47-metre-deep ventilation shaft at Castle Vale, which will eventually connect with cross passages to provide ventilation, servicing, and emergency access.

The entire structure, including a headhouse atop the shaft, is scheduled for completion in 2027.

A second TBM, named Elizabeth began excavating the tunnel’s second bore in March 2024 and is expected to complete its task by late 2025.

Together, the two TBMs will remove 1.87 million tonnes of excavated material, which is being processed at an on-site slurry treatment plant and repurposed for use at nearby construction sites.

Steve Powell, HS2’s Head of Delivery said:

“We’re now at peak construction in the West Midlands, and it’s great to celebrate the halfway point for the Mary Ann tunnel drive into Birmingham. By the end of next year, both of these tunnels will be built, marking a significant step in HS2’s construction in the region.”

In preparation for the TBMs’ arrival at Washwood Heath, a large earthworks operation involving 130 workers has been completed, constructing the west portal of the tunnel.

This portal, situated 22 metres below ground, is the deepest of the four tunnel portals on the Midlands section of the HS2 route.

The portal leads into a 750-metre-long cut-and-cover structure, where HS2 trains will transition from the Bromford Tunnel and travel below ground before rising onto viaducts through Birmingham’s industrial areas towards Curzon Street Station.