“I started my career about 30 years ago, and throughout my career I have been heavily involved in transportation projects. My first three jobs were associated with tunnel collapses. That probably gives the impression that we have a lot of collapses in tunnelling, which is not the case,” quips Mott MacDonald tunnel practice leader for UK and Europe Rosa Diez.
Rosa Diez is tunnel practice leader for UK and Europe at Mott MacDonald
Diez clarifies that she started her career as a member of the recovery team for Heathrow Express. She then moved on to work on many UK transport projects, such as Victoria Station Upgrade, Crossrail and HS2. She was also involved in international metro projects in Portugal, Australia and Norway.
Diez has observed a decline in investment in underground transport infrastructure over the past five years.
“There have been transport projects cancelled or postponed, while the investment in the London Underground is decreasing. There’s been an uptick of funding on metro systems, but they are not really underground.”
She highlights that the cancellation or postponement of schemes has had a negative impact on the industry. “The Stonehenge tunnel contract was awarded, so we had some people working on that project before it was delayed and eventually cancelled. That creates huge uncertainty. Also, the cancelation of HS2 [Phase 2] has been disastrous, because it was a continuous pipeline which is no longer there.”
Diez says the resulting uncertainty and reduction in the number of major tunnelling projects has led to an exodus of tunnelling experts to markets offering attractive packages, such as Saudi Arabia and Australia.
“I have seen the market fluctuate during my career,” she says, adding that she is confident that activity will soon ramp up again, just not through transport projects. She points to the increased investment in energy and water infrastructure to boost resilience and achieve Net Zero, which could see a significant number of underground assets being built.
Differences and similarities
In general, water and energy tunnelling projects are smaller than transport ones – even though there are exceptions like Sizewell C – but larger in number.
“Water and energy projects are similar to multi-disciplinary transport projects; you still need to understand what goes into them and why, what the drivers for the operational functionality and maintenance are, and the futureproofing aspects needed,” says Diez.
“The main difference is that water and power tunnels will not have people going into them regularly. Instead of a daily basis as is the case for transport tunnels, someone may go into them once every 10 years. Transport tunnels need clear guidance for emergency evacuation provisions. The same considerations will apply when it comes to tunnel construction, although perhaps with more focus on maintenance needs. For example, large sewage tunnels with terminal pump stations will need the ability to collect and remove debris brought into the system from combined sewer overflows.”
Diez adds that different construction methods and equipment are often used for water and power tunnels compared to the transport tunnels.
She uses pumped storage hydro (PSH) schemes as an example, as many are under development in the UK, predominantly in Scotland. Diez says some of the proposed schemes will involve tunnelling in ground conditions that the UK industry is not familiar with.
These schemes will require practices like drill and blast, which are not commonplace in the UK, and the development of the associated skills. “We will need to drag in experience from overseas,” she adds.
Ground investigations for PSH schemes will also be different. Diez explains: “The majority of UK transportation projects have been in big cities and had huge funds, so in many instances we’ve been spoiled for choice in terms of boreholes and variety of ground investigations. For some PSH schemes you might not have that luxury. Some underground assets will be quite deep which would make drilling boreholes expensive, leading to more reliance on non-intrusive methods such as geophysical surveys and expertise of people with knowledge of the geology and geotechnical properties.”
With PSH schemes typically located in remote areas, Diez emphasises the clear need for projects to offer the right working conditions and facilities to attract tunnellers. She adds that this will be an opportunity to upskill people from the local communities.
As to whether the industry is ready to deliver an expanded portfolio of projects in the energy and water sectors, Diez says: “The industry has been preparing for it. At Mott MacDonald, we’ve seen the trend and we are training more people to get involved in these projects so that we can cope with the increased demand.”
Diez has observed a decrease in investment in underground transport infrastructure over the past five years, with transport projects cancelled or postponed, while the investment in the London Underground is decreasing
Learning from transport
Could the knowledge acquired from the delivery of transport tunnels help the industry with underground works for the water and energy sectors?
“Transport tunnelling projects, especially in urban environments, have developed robust approaches to managing complex risks, unknowns and interfaces. These include: early contractor involvement and collaborative frameworks; detailed geotechnical baseline reports and risk registers; programme and construction management practices that can be adapted for water and energy tunnels, where unknown ground conditions and stakeholder interfaces are also significant,” says Diez.
“Transport projects have also developed sophisticated methods for engaging with multiple stakeholders, navigating complex regulatory environments and managing public interfaces. Water and energy projects can benefit from these practices, especially as they increasingly intersect with urban environments and require approvals from multiple authorities.
“In terms of delivery models, we’ve seen that frameworks and alliances developed for major transport projects are being adopted for large-scale water and energy tunnels, improving efficiency and knowledge transfer. Simplification around the number of parties involved and on the intricacy of processes applied could help the water and energy industry avoid the programme and costs overruns experienced by many of the transport projects.
“It is also clear that transport projects have led in terms of pioneering and adopting cutting edge tunnelling technologies and digital tools. These innovations will be increasingly used and further developed in the water and energy sectors.”
Diez points to the use of data and automation to improve efficiency of delivery. She highlights the industry’s drive towards the use of data to optimise designs via the observational method rather than the prescribed method which “might be over-conservative”, as well as robotics on site with additional health and safety benefits.
Even though there is a shift in the types and sizes of tunnels being constructed, Diez believes the tunnelling industry still offers opportunities for a “fulfilling” career. “It’s just a question of people being flexible and wanting to diversify. It’s an opportunity for some to work on different types of projects than they did before, which might be equally or even more interesting, and learn from those.
“In the tunnelling industry, we work on assets that society can use. We are helping the community move, be energised and have access to water, which makes everyone feel really proud of what they achieve.”
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