HS2 'green tunnel' reaches halfway stage with breakthrough due to join key segments

Two key segments of a new HS2 ‘green tunnel’ that uses a short alignment of a disused railway are set to be joined for the first time.

The 700-metre-long Burton Green ‘tunnel’ is now 50% complete.

HS2 has taken over a cutting which was home to the line between Berkswell and Kenilworth Junction (closed in 1969). It is turning the cutting into a tunnel with plants and vegetation on top, unifying the two halves of the Warwickshire village of the same name.

The tunnel itself is being built using a ‘top down’ method. The side walls and roof, which is currently made up of concrete beams before the main slabs go on, were installed before the excavation work was carried out and the tunnel base constructed.

Rupert Blake, Balfour Beatty VINCI’s Project Manager at the site, explained: “It [the roof] was originally going to be a single slab and everything dug out goes out through the northern portal.”

He described that method as “daunting”. It was estimated that excavating that way would have taken a year longer. Instead, teams have been able to excavate in three locations simultaneously.

Engineers dug three metres below the original trackbed before putting in the first concrete base. In the past year, retaining walls and 1,300 piles have been installed.

Once complete, there will be just over eight-and-a-half metres between the rails and tunnel roof, with another three metres from there to the top of the existing cutting’s embankments.

As this issue of RAIL went to press, a breakthrough under Cromwell Lane, to unite the 200-metre-long southern portal with the rest of the tunnel, was expected.

Blake described Cromwell Lane as a “thorn in our side”. He said the road had to be realigned for the old road bridge over the cutting to be removed, a process which also included temporarily severing gas, water and communication connections.

Since then, the road has remained open to keep the two halves of the village connected.

Meanwhile, engineers have constructed a cut and cover tunnel (immediately to the north) to the southern portal on the other side, and excavated earth from under the road.

Next year, Cromwell Lane will be put back on its original alignment, but resting on the tunnel and earthworks on top of it, rather than going over a bridge. Parts

of the original bridge are being donated to the community. The overall Burton Green work site is two kilometres long, with a retained cutting being installed immediately beyond the 200-metre-long northern portal.

Situated 12km (7.5 miles) south of Birmingham Interchange station, Up trains will be approaching top speed as they pass through the tunnel when the line opens in a few years.

At Waste Lane (the northern end of the site where the original railway diverted to the west of the new HS2 alignment), the road bridge over the disused line and embankment in the path of the high-speed route will be removed and replaced with a new bridge, built on site.

Work to replace the existing Waste Lane structures is expected to begin next year, once activity Cromwell Lane is complete. HS2 cannot have both roads closed simultaneously.

Engineers have also had to realign the Kenilworth Greenway, a country park which previously followed the old trackbed. Once complete, it will run along the
top of the tunnel, going under Cromwell Lane, then alongside the retained cutting.

“The state of the (greenway) land was shocking,” said Blake. “Halfway along was a condemned bridge. You would not want to walk your dog down there. You couldn’t ride your bike down there.

“The new greenway will be a bespoke footpath as opposed to an old railway for cycling, footway and equestrian.”

It’s estimated that the tunnel will be complete in autumn 2026. Eventually it will be one of five ‘green tunnels’ on the route, with others at Copthall in Hillingdon, Wendover (Buckinghamshire) and Chipping Warden and Greatworth (both in Northamptonshire).