Clients must dig heels in to decarbonise tunnelling, PAS 2080 advocate urges

Challenging one another across the supply chain will be an essential part of slashing the lifetime greenhouse gas emissions of tunnelling projects.

That was the key message from the Digging for net zero event, which explored how to apply the PAS 2080 decarbonisation standard to tunnelling – a traditionally carbon-intensive activity.

“The word ‘challenge’ is woven into PAS 2080 – it is repeated about 20 times,” said Lewis Barlow, keynote speaker and ICE trustee for climate and carbon.

“We know in our heart of hearts that the way we’re doing things is unsustainable,” he said. “PAS 2080 recognises this and says that everyone in the supply chain needs to challenge everyone else… recognising that the system needs to change.”

Carbon management must therefore become integral to procurement, with “carrots and sticks” included in contracts, added Barlow, who is also decarbonisation head of profession at WSP in the UK.

One important tool for achieving this has been the update to the NEC4 suite of contracts to include a clause containing decarbonisation requirements: secondary option X29.

Decarbonising the Lower Thames Crossing

Also speaking at the event was Dr Neil Phillips, principal engineer at COWI, which is working on the Lower Thames Crossing (LTC).

This project will build a 23km road linking Kent and Essex via a 4.2km twin-bore tunnel beneath the river east of Gravesend and Tilbury.

The LTC sets the example as the first substantial highways project to gain PAS 2080 accreditation.

It even requires subcontractors to be PAS 2080 accredited, let alone its contractors. 

“Decarbonisation is an engineering problem we need to embrace as engineers,” he said. “But it’s also a commercial problem – and we must understand how to make that change right from the start of our projects and drive it all the way through.”

LTC contracts contain clauses that incentivise decarbonisation.

Set the tone

Phillips said clients should set the right tone by devoting enough time early in a project to explore several possible options and their effects on lifetime emissions.

The LTC’s leaders have set the ambitious target of a 70% reduction on the baseline figure calculated for its CO₂ emissions.

It has been designated a “pathfinder project” for the construction industry by testing innovative low-carbon methods and technologies.

“We are really focused on outcome, rather than over-specification,” said Phillips, who is also a member of the British Tunnelling Society’s Net Zero Tunnelling Group.

“We’re allowing the designers and contractors – the guys who really know how to do this – to come to us with ideas as to how they can drive carbon out.”

Digging for net zero was hosted by the ICE, the British Tunnelling Society and the British Geotechnical Association.