MDjv completes HS2 box and tunnel

29 July 2022

HS2 station contractor Mace Dragados JV (MDjv) has excavated a 20m-deep box and a tunnel for the new Euston station.

The box will house a new traction substation (TSS) which will convert electrical power to a form suitable for a rail system. The TSS will enable the relocation of equipment needed to provide services and ventilation for the Northern Line at Euston.

In addition, MDjv dug a 90m-long tunnel to connect the TSS to the London Underground network. The 6.5m-wide tunnel runs under the HS2 construction site.

The tunnel construction took 16 months and saw the MDJV team sink a 20m-deep shaft before excavating the underground passage and applying a primary SCL. The tunnel was then reinforced with steel and concrete to provide the structure needed ahead of the construction of the HS2 station above it.

MDjv, supported by its principal sub-contractors Cementation Skanska, Careys and JGL, used several measures to reduce the environmental impact of the works. Redesigning the tunnel to lower the carbon impact during construction – through reduced material and water use, a reduction in vehicle movements, and a lower energy consumption – resulted in an overall carbon saving of 140 tonnes, while efforts to reuse material already on site resulted in over 1,000 fewer lorry movements and an associated saving of 76 tonnes of carbon dioxide from vehicle emissions.

Throughout the tunnelling works an acoustic shed enclosed the shaft to reduce noise impact. This enabled 24-hour working which was required to meet the demands of the programme.

Rob Williams, senior project manager for the traction substation at MDjv, said the progress made at the traction substation was a by-product of collaborative working between HS2, Mace Dragados, supply chain partners and critical external stakeholders, including Transport for London.

“Our one-team approach has allowed us to build a culture and leverage the expertise needed to deliver this complex and highly constrained project, which is essential for the construction of the new HS2 station at Euston,” he said.

With the tunnelling and excavation works at the site now complete, the team will now construct the below and above ground structures for the new traction substation, before fitting it out with the necessary equipment and connecting it to the Northern Line. The building will have three storeys below ground and four above.

Once the new structure is complete, the existing TSS will be demolished.