Learning Legacy Podcast: Episode Three – Reducing and reusing
HS2’s place within the current climate and environment has always been its top priority. Once operational, the British-built bullet trains will provide zero-carbon journeys between the UK’s two largest cities, Birmingham and London.
Episode 3 explores how HS2’s railway assets have been designed from the start with climate change resilience in mind, as well as utilising waste clay from tunnelling, and how it can be transformed into low carbon concrete.
Featuring:
- Kay Hughes – HS2 Design Director
- Alison Walker – HS2 Climate Change Manager
- Dr Rachel Allison – HS2 Climate Change Specialist
- Nick Podevyn – Align Innovation Manager
- Athina Papakosta – SCS Sustainability and Carbon Lead
- Dr Fragkoulis Kanavaris – ARUP Concrete Materials Lead
- Apostolos Tsoumelekas – SCS Materials Engineer
- Tom Burr-Hersey – HS2 Senior Environmental Manager
Kay sets the scene with how the project is being delivered with the future in mind, achieving sustainability from as early as the design stage and maintaining it through strong communication.
Alison and Rachel take us through all things climate when it comes to construction of the project. ‘The 4R’s of resilience’, the planning towards weather conditions by using multiple climate models, and how much climate adaption is front and centre from design all the way through to operation.
Nick focuses on the construction of the Colne Valley Viaduct with Align’s giant launch girder. Combating issues with wind, rain and heat to ensure the construction schedule isn’t affected and the use of MetSwift weather models.
Athina, Fragkoulis, Apostolos and Tom dive into the reuse of London Clay to reducing climate impact by cutting transport emissions related to removing the material. The possibility of excavated London Clay being turned into local concrete, it could also reduce the embodied carbon emissions.
Find out more about HS2’s Learning Legacy Programme
Learning Legacy papers featured in this episode
- Delivering a climate change resilient railway
- Transformation of London clay into construction resources: Supplementary cementitious material and lightweight aggregate
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Episode transcript
This is a transcript of episode one of HS2’s Learning Legacy podcast, first published on 28 March 2023.
Rhian Owen
Hello, and welcome to the HS2 Learning Legacy Podcast. I’m your host Rhian Owen.
In this episode, we are going to look at projects that consider the railway’s place in the environment, and the impacts climate change might have on the railway. We’ll see how railway assets have been designed from the start with climate change resilience in mind. We’ll learn how granular modelling of weather conditions is allowing for safe, efficient, construction, regardless of wind, rain or scorching heat. And we’ll discover how waste clay from tunnelling can be transformed into low carbon concrete.
The future we face is an uncertain one. As humans we know that our activities are having an unprecedented impact on the climate. But we don’t know just how extensive or disruptive these changes will be.
Once operational, HS2’s British-built bullet trains will provide zero-carbon journeys between the UK’s two largest cities, Birmingham and London.
Kay Hughes is design director for HS2. She says that a key part of the legacy of the railway will be what it tells us about how we can design for this future.
Kay Hughes 01:19
The aspiration of the programme at the outset to deliver a future proofed railway around climate change at scale, has massive lessons for the industry across all of the different areas, you know, from the Urban Design integration from improving passenger experience from minimising environmental impact or, or integrating it cost effectively. I think all of those are big lessons that we are working to deliver in HS2 and I think they’re really good examples of where we’re delivering better and well that are coming through the learning legacy.
Rhian Owen
HS2 is one of the UKs first pieces of major infrastructure that has climate resilience embedded at every step of the process.
Alison Walker 02:11
The difference between HS2 and legacy infrastructure is that we’ve been able to build in climate resilience every step of the process, planning, designing and constructing the railway. As well as integrating this work into plans for future operations and maintenance.
Rhian Owen
Alison Walker is climate change manager at HS2 and author of the ‘Delivering a climate change resilient railway’ learning legacy paper.
Alison Walker 02:35
HS2 is designed to be resilient to a one on 1000 year event. And our drainage infrastructure is also designed to cope with a one in 100 year plus climate change. So this will protect the railway infrastructure from floodwater, ensuring that it will remain operational or we can restart without undue delay.
Rachel Allison 02:56
Just to explain what we mean by a one on 1000 year event. So that’s a flood event that magnitude was statistically speaking, have a one in 1000 chance of occurring in any given year. So as Allison said, it’s a higher bar than most other infrastructure projects.
Rhian Owen
Dr. Rachel Alison is a Climate change Specialist at HS2.
HS2’s environmental policy set out from the start that the network had to be climate resilient in the long term. And it specified many climate change related requirements and standards for the design and construction process.
Alison Walker 03:28
So underneath that we have the bespoke climate change adaptation and resilience technical standard that provides all of HS2’s requirements and associated guidance for managing climate change resilience. That includes design construction and operation of HS2. The requirements set out in that technical standard are really important because they set the basis for all our decision making.
Within that we talk about the climate change design impact assessment, or CCDIA, for assessing the resilience of standards and our future designs. We provide the climate change design impact assessment to our contractors. And then they use that to assess their risks and provide us with a climate change adaptation and resilience report that we then assure.
Rhian Owen
By receiving an impact assessment contractors understand exactly what is required, and their resilience report allows HS2 to know that their resilience standards are being met.
One example of HS2’s commitment to high standards is station’s BREEAM certifications. BREEAM is the Building Research Establishment Environmental Assessment Method. It scores a building from pass to outstanding based on a number of different environmental and sustainability criteria.
For all HS2 stations, achieving the BREEAM credit for climate adaptation is mandatory. This has led to some creative innovations at stations like Interchange in the West Midlands.
Rachel Allison 05:10
In terms of climate resilience, some of the adaptation measures they’ve implemented at interchange include the innovative roof design, and this captures and reuses rainwater to reduce the mains water demand.
So, during times of drought will be much more resilient and also the landscaping features that will be implemented around the station. These use sustainable drain systems to reduce the burden on our surface water during periods of intense rainfall, and then naturally irrigate the planted areas during periods of drought.
Rhian Owen
What has been key to ensuring the delivery of climate resilience is making the process clear and consistent for the design and construction contractors. That will be a valuable legacy for the industry, says Kay.
Kay Hughes 05:56
The lessons learned from those projects are, how do we respond to the effects of climate change and making greener buildings that lower carbon. So, the lessons we have from those is 1) at the outset and during the design stages a certain amount of kind of fluidity in the design to get all of those different constraints resolved into a design. And then the other part of that is the kind of objective for having a sustainable outcome which is low carbon, so using timber in the roof, using daylight within the building, and then also using the grey water from the roof and using that in the balancing ponds nearby. It’s a perfect learning legacy, particularly for what you would call parkway stations, you know, how they can be done in an environmentally way.
Rhian Owen
But it’s not just the stations, assets of all types up and down the line need in some form or another to be able to face the changing climate, and avoid the kind of problems that are caused for the existing, conventional railway, by extreme weather events.
Rachel Allison 07:16
So, in HS2, we’ve got lots of earthworks, we’ve got embankments, and we’ve got cuttings, and these are all going to be susceptible to climate change. And their stability is obviously absolutely critical. So what we’ve done is we’ve tried to combine the different climate variables that are going to be impacting these variables and then made sure that our earthwork designers have adopted a cautious design approach.
Rhian Owen
But being climate change resilient is not just about preparing for the worst and hoping to survive it. In fact the climate resilient railway learning legacy paper lays out what Alison calls the “4 R’s of resiliency”.
Alison Walker 07:55
Resistance concerns protecting physical assets from impact of adverse climatic events.
Reliability, that’s the capacity of the infrastructure or asset to maintain operations under a range of conditions.
Redundancy is the adaptability of the infrastructure system, or network and response and recovery, which is the ability to recover from a disruption to return to functionality.
Rhian Owen
The final R, or two R’s, for response and recovery are particularly important. Predicting what climate change will bring in 100 years is nearly impossible. Therefore, HS2 is being careful when using future projections.
Rachel Allison 08:39
No one climate model is going to be perfect, these are projections, they’re not predictions. So we have to be cognizant of that and make sure that we’re not putting all our design scenarios into one model that may or may not happen so we’ve chosen ones that are conservative so yeah trying to make sure that the climate protection use is realistic but not too excessive.
Rhian Owen
And if something does happen or when it becomes time for an asset to be replaced, HS2 will have the ability to improve the resilience again.
Rachel Allison 09:15
While the railway is designed to be built over the 120 year life span, not all components of it will have that full length of lifespan. So where we are doing asset replacement cycles as part of the regular use, adaptive management will allow us to look at the climate projections at the time that they’re replaced and make adjusted decisions accordingly. So it might not be replaced, for there might be a better solution in the future.
Rhian Owen
Climate adaptation has never been so front and centre of a major infrastructure project before. The results are individual assets and an overall train system that will be fit to face climate change challenges.
From aerodynamic bridge design, to water efficient stations every single asset along the route has had resiliency considered and built in.
But it’s not the individual design elements or innovations that make HS2’s climate resilience special, it’s the commitments, clear standards and collaboration across the project that has allowed them to deliver an asset fit for the entire 21st century.
Alison Walker 10:20
I think the main reason why we’ve been able to do so much is that we’ve had fantastic colleagues to work with HS2 to set up a climate change adaptation, resilience focus group, that’s been really helpful. So that I think is a really good piece of learning from the work that we’ve been doing. No one person can do this job. It has to be collaborative across the organisation.
Rachel Allison 10:49
l think it’s just that a project of this scale has so many different aspects and things that need to be thought about. And I think as Allison said, it was no one person can do all of this. So having it all set out, make sure that it is considered and it doesn’t get lost in the scale of the project. Because that would be a real loss to the project is it strengthened by how many experts and how many different elements are being considered across the project to make it the best railway it can be.
Rhian Owen
Alison and Rachel’s paper looked at the broad challenges of climate resilience. Their work considers the long term impact of climate on a project that is designed for a 120 year lifespan.
But we are already seeing the effects of climate change today. Extreme weather events like rain, heat and high winds, can all disrupt construction work. And, as climate change takes hold, all of these are becoming more frequent.
Nick Podevyn is an innovation manager for Align, working on the section Phase One of HS2 that includes the Colne Valley Viaduct and Chiltern Tunnel. He worked with Alison and Rachel on their paper.
For the Colne Valley Viaduct, Align is using a bridge launch girder. This sits on top of the partially built viaduct. It picks up heavy concrete sections, and positions them for attachment to the viaduct.
Nick Podevyn 12:24
it’s a huge challenge about wind, winding off events for lifting for, for cranes and stuff. So straightaway, that was something that was a laser focus for us. And that was really the starting point for me as the innovation manager to look for some ways to optimise for weather, and really understand weather forecasting better.
Each segment is 140 tonnes-ish, and the wind speeds window is fairly small. And it’s not just the speed of the wind, but you’re looking for a window, once you start lifting that segment underneath the launch girder and moving it out into position and lowering it down into its final resting place, you need the wind speed to be low enough for that whole period of time.
Rhian Owen
When you’re slowly raising heavy concrete sections like this, wind is a real threat. But other construction activities around the girder are also impacted by weather.
Nick Podevyn 13:17
We use some multi wheeled vehicles. So we’re doing on site manufacturing. So all our segments are cast at the south portal site. And then they’re moved by those vehicles, sort of like a low loader from the site, down from the, the precast site down to where the launch girder is. There are other weather implications of that. So the haul road, particularly in winter, it’s, “What’s the quality of that haul road.” Traditionally, you know, these sort of temporary roads degrade through the heavy rain fall.
Rhian Owen
Rain is also a threat to the finish of the viaduct.
Nick Podevyn 13:57
To do the waterproofing, it needs to be dry to do it properly. So we’re not looking at wind speed anymore. We’re looking at what’s the likelihood of a rain event, how much rain, and for how long.
Rhian Owen
The summer presents its own challenges with the UK now seeing extreme high temperatures.
Nick Podevyn 14:15
2022 was the first year we saw, you know, above 40 degree heat, all of a sudden, it’s not an environment we’re used to working in and safety comes first. And sites are getting stopped in extreme weather.
Rhian Owen
To understand all of these challenges, Nick needed more accurate information.
Nick Podevyn 14:33
Traditionally, you go to the Met Office, and you find their local weather station nearest you to get your weather data. And that gives you a certain level of confidence and detail.
But then you have to start asking yourself a few questions about the data that you’re getting from the Met Office, which is very good. But it is a general weather Met Office station. So for us, we wanted to be much more specific to the operations we’re doing.
And so that led us down the route of looking for something where we had weather stations on site, collecting the real weather data. And that then led us well, how do you then use that in a more, you know, with better insights. So that led us down the route of finding a small startup company that used artificial intelligence and machine learning. And they were able to bring in weather models, so global weather models, looking at historical patterns, and then bring in the sort of UK weather models and then bring in the site specific weather data, enabling us to get a very site specific forecast for 10 days ahead in detail and then also up to two years ahead in more general detail.
Rhian Owen
The company Nick describes is called MetSwift. It was able to make more accurate predictions around when adverse weather events would occur, and for how long. That meant the launch girder could work safely, without excess downtime.
MetSwift’s model also takes into account site-specific conditions. The Colne Valley naturally funnels wind, so gusts may occur on site even when overall wind speeds for the Met Office area are acceptable.
But the model can be used for more long term forecasting.
Nick 16:16
So the 10 day ahead capability is kind of like an app on your phone, where you are looking and at any time you going on to the system, it’s bringing all that weather data to you to your fingertips. And it depends on what operation as you’re doing. So as I described there, some teams might be more interested in the in the rain events, others more in the wind events. So you can optimise by just looking at one of those weather parameters and also setting your weather limits.
And then there’s the longer term forecasts where you’re not getting hour by hour type information. But you’re getting more a day by day view of the world, of these different parameters. So that’s more helpful to our planning teams. It’s helpful to the teams when they’re looking to budget for the next six to 12 months ahead.
Rhian Owen
By tracking site specific weather conditions, and making forecasts using MetSwift’s modelling, Nick and Align have been able to point the way to a brighter future.
Alison and Rachel’s work helps us understand how to build an asset that is ready for 120 years of unpredictable climate change. Nick’s work with MetSwift shows how, as adverse weather events become more frequent, we can continue to work on site safely and efficiently.
But how do we limit the impact of climate change? One way the construction industry can do this is by replacing Portland lime cement in concrete.
Athina Papakosta 17:43
Concrete is the second most consumed material on Earth after water, to give it context, and we are in dire need of solutions to decarbonize it, and decarbonize it fast.
Rhian Owen
Overall, Athina Papakosta, SCS Sustainability and Carbon Lead explains, the built environment accounts for around 40% of all climate changing emissions. Much of this from the impact of steel and concrete production.
Cement – the key binder material within concrete production produces greenhouse gas emissions that contribute to climate change in two ways: through the heat required to turn limestone into cement and the release of carbon dioxide during this chemical process.
Athina and her colleagues have been studying how London clay extracted from HS2 tunnelling could be used in construction. This would cut transport emissions related to removing the material. If the excavated London Clay could be turned into to be used locally in concrete, it could also reduce the embodied carbon emissions.
They worked on this through the REAL project – a feasibility study led by SCS and Arup to look into innovative ways to use the otherwise waste excavated clay as a construction resource.
Athina Papakosta 18:58
We initially were looking at two primary potential outcomes, which—one of which—was lightweight aggregates, but from expanded clay and the other one that gained more and more traction due it, due to its potential in all shapes and forms, including both technical potential and sustainability benefits was, the supplementary cementitious material from calcined clay.
Rhian Owen
Before they got their hands dirty, working directly with the excavated clay, Athina and her colleagues explored the existing research, and performed some lab tests.
Athina Papakosta 19:36
The first step was to look at what was out there in terms of literature, it was to analyse samples from different locations of calcine clay, to examine its variability in its property, so on and so forth, and run, let’s say, a first round of testing on these on these samples, with regards to the, to the suitability for these particular two applications, the expanded clay and the calcine clay.
Rhian Owen
Dr Fragkoulis Kanavaris is concrete materials lead for Arup. He worked on the project with Athina. The team saw that there was some potential for the waste clay to be used in expanded form as aggregate. But the biggest win would come from using it as a replacement for cement.
Fragkoulis ‘Frag’ Kanavaris 20:22
We started together, thinking about how to manage the waste that is going to be generated and is currently generated as part of the tunnelling operations within the London tunnels. And we came up with this exciting idea. And we’re seeing now that more and more industry bodies are getting interested in this kind of application of waste clay as a supplementary cementitious material.
Rhian Owen
The product the team focused on is known as calcined clay. Like cement, it is heated in a kiln. But the raw material and the chemical reaction taking place during production is different and does not release CO2 and the temperatures required are lower than those for cement.
Apostolos Tsoumelekas is a materials engineer for SCS and worked on the project coordinating the concrete trails at the SCS labs.
Apostolos ‘Apos’ Tsoumelekas 21:18
I was mainly involved in getting the calcine clay and doing the lab trials, developing the concrete mixes for the lab. As a contractor, we don’t get too much hands-on experience of new products coming up, we would normally rely on the supply chain to do that, and we attend trials. But this was a hands-on experience. And it was great to do.
It’s amazing to lead the industry into this and now we see more contractors, more supply chain, going into the calcine clay works. And HS2 gave us this opportunity to do that. It’s a project that can allow that, and the legacy coming out of that is massive.
Rhian Owen
Tom Burr-Hersey supported the project from the HS2 side. The HS2 tunnelling works under London, that SCS and other HS2 contractors are undertaking, would produce a vast amount of material for the team to work with.
Tom Burr-Hersey 22:10
Our contract is unlike any of the others on HS2, because I think if you look at the phase one, and hybrid build design, there’s 130 megatons of excavated material waste across phase one. So we’ve got to be really innovative on what we do with our waste, because we, we simply can’t reuse it under other kinds of materials management plans or other kinds of permitting regimes, we’ve got to work out what we’re going to do with it. So anything we can divest from going to landfill, or or being a proper waste product, is a win in my book and a massive sustainability score.
Rhian Owen
The idea of using clay in concrete is not a new one, Frag explains.
Fragkoulis ‘Frag’ Kanavaris 22:52
How did we have that eureka moment? And we have to acknowledge that when we were dealing with a problem of managing the waste and what we can do with a clay waste, the inspiration came from calcine clays being used back in the 60s and 50s, in the construction of massive dams in in Brazil in particular. And back then they were using low quality clays because the concrete that is being used in dams and was being used in dams at the time, didn’t need to be very high quality, very high strength.
We knew—back in 2018—that this was possible back then: they did it back then, they extracted clay, low grade, low quality clay, and they calcined it and they used it in concrete to produce medium to low strength concrete.
Rhian Owen
It’s important to emphasise that as well as finding a use for this waste excavated material, calcining clay offers a double win in climate change terms.
Fragkoulis ‘Frag’ Kanavaris 23:59
Portland cement is manufactured through heating up limestone and clay and other minor constituents to 1400, approximately 1400, degrees Celsius for an hour and a half. So, we’re following a similar thermal treatment process but with half of the temperature, and half of the duration required for calcination, so calcine clay encompasses about 1/3 of the embodied carbon of Portland cement.
Rhian Owen
The potential to make use of clay is well established. But would the London clay from these tunnels have the characteristics the team needed to use it in concrete?
Fragkoulis ‘Frag’ Kanavaris 24:42
So, the key points that need to be understood is whether the clay contains any contaminants that could be potentially detrimental to the durability or the behaviour of the concrete overall, whether the clay contains any contaminants that could impair its reactivity, and by reactivity, we mean, how well is it going to perform in concrete as a cementitious material?
Rhian Owen
They then moved on to consider the process of calcination, and the performance of the calcined London clay as a cement replacement.
Fragkoulis ‘Frag’ Kanavaris 25:19
Because we want to use as low a temperature as practically possible and for as short time as practically possible to minimise the energy consumption. And then once we obtained the different samples of calcined London clay material, we carried out tests on its reactivity and its potential use, use in concrete, using microstructural techniques and thermal processing techniques.
Rhian Owen
The team showed that the clay extracted was of a consistent quality. In the lab, they demonstrated concrete made with it would perform as required. But can the project be scaled up?
Athina Papakosta 25:57
It can be a, let’s say, gradual process of increasing, let’s say, the size of the plants. But that is exactly, let’s say, the crossroads at which we sit at the minute, because the next step will need to be commercialization.
Apostolos ‘Apos’ Tsoumelekas 26:16
We showed you can produce a concrete mix that can actually be used in the works. Yeah. Now, there needs to be a little bit of a mindset change in the industry in general, because obviously, it’s something new. But if you started the process, and you saw that this can be done. Yeah, it looks like normal concrete. Yeah, the colour might be a little bit different. But it it reacts as concrete, it hardens the way it does, it does whatever you want it to do on site, then more people will look into it and say, okay, yeah, this works, therefore, I’m more happy to go ahead and use it on our pr… on our projects. And this is a good thing that we can do with this, changing the mentality of how people see what we have been doing for the last 20, 30 years and what we’re going to be doing in the next 20 years.
Rhian Owen
The team’s work shows that this could be possible in London with industry support. There’s no shortage of material that could be used in this way.
Tom Burr-Hersey 27:13
So when it comes to London clay, I think really we’re, we’re almost putting our line in the sand. The government is going to have Crossrail two it can pick up off the shelf, there’s going to be other tunnelling projects in London, if you think about the depths of London clay, I think some areas 150 metres deep, normally deeper towards the east end of the basin, as densely populated as the tube map looks when you look at it there’s plenty of space down there. And that space is going to produce London clay as arisings.
Rhian Owen
The paper sets the groundwork for London clay to be used as a cement replacement for concrete production. It has a wider legacy though, that could see benefits across the construction industry.
Fragkoulis ‘Frag’ Kanavaris 27:59
We also contributed to a scientific breakthrough, showing the engineering and scientific community that is possible to use waste clays that are low quality for production of calcine clays in concrete. And we are seeing now because I’m monitoring how research evolves over the past years in that field. We are seeing far more research being conducted in lower grade or lower quality waste clay than it was a couple of years ago or three years ago.
Athina Papakosta 28:32
We’d like to see ourselves as paving the way, that it is a product that of course needs work, but it looks good and it looks like it can be trusted because of the results we are producing.
Rhian Owen
In this episode, we’ve seen how we can design a railway—and other assets—to withstand the effects of climate change. We’ve seen how construction can be carried out safely and efficiently, even as adverse weather conditions become more frequent and more intense. And we’ve learned that the waste materials of tunnelling in London, along with clay from other sources, could one day be used to replace carbon emitting constituents of concrete.
In our next episode, we’ll learn about some of the ways in which the railway is helping improve the health, safety, and wellbeing of its staff and customers.
Credits
Rhian Owen
I’ve been your host Rhian Owen. Thanks to our guests Kay Hughes, Alison Walker, Rachel Alison, Nick Podevyn, Athina Papakosts, Dr. Fragkoulis Kanavaris, Apostolos Tsoumelekas, and Tom Burr-Hersey
You can get more detail on all the topics featured in this series by taking a look the HS2 Learning Legacy website, we have provided links in the episode description.
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