Combining innovation, modern methods of construction and a whole life carbon approach08.02.24
HS2 is Britain’s new high speed rail line, designed to link Britain’s biggest cities and boost economic prosperity across the country via improved connectivity. It is a flagship infrastructure project within the Government’s Levelling Up strategy.
Sustainability is central to the entire project. HS2 has a strong focus on carbon reduction; when running, every HS2 train will be powered by zero carbon energy, in order to provide a genuinely green alternative to road and domestic air travel. The embodied carbon in the project build is an area of intense focus too. As part of the Laing O’Rourke – Murphy joint venture (LMJV), Laing O’Rourke brought its expertise to the project, responding to the client’s request to remove carbon and waste at every stage.
The full scope of works was analysed, and the most carbon intensive work packages identified. These packages provided the most substantial opportunity for carbon savings and as such provided a clear focal point for the team in terms of identifying innovative carbon reduction solutions. Full life cycle carbon assessments were completed, providing a greater level of detail from which to formulate a plan.
We then developed an integrated strategy that considered the carbon savings possible through smart design decisions, material reuse, lower carbon materials, sustainable procurement practices and innovative on-site technologies.
This plan produced a 42% carbon saving versus the baseline
The team was keen to explore further opportunities to reduce HS2’s environmental impact, beyond absolute carbon reduction during construction. Whole life carbon emissions were calculated, enabling us to develop a comprehensive picture of the project, including ongoing operational efficiency once complete and how components are managed at the point of disassembly or end of life, including opportunities for reuse or recycling. Direct environmental impacts were documented as part of the environmental assessment process,
such as water use, air quality impacts and waste management practices. Embedded environmental impacts were also considered to fully understand the project’s environmental ‘reach’. The team interrogated the materials used via Laing O’Rourke’s supply chain partners to formulate a total view of resource availability and the climate change impact of using those materials. It was important that sustainable choices were made when it came to selecting materials. The strategy incorporated reuse of materials from site where possible. Where reuse wasn’t an option, the team sought to use materials with recycled content.
We used the carbon reduction hierarchy framework to develop the strategy, challenging at each stage to ensure carbon was minimised through the project design and construction. This forensic approach enabled us to tailor a programme of work that maximised the carbon savings. For instance, we redesigned a work package for a complex highways diversion that resulted in a 96% reduction in the materials required.
We found opportunities to reuse existing infrastructure or materials from the site to minimise the need for new materials. For example, by using existing pavement in parts of the development we were able to reduce the quantity of new materials required to meet the same depth. In fact, we took an innovative approach to materials deployment across the work packages. This included using a thinner, stronger asphalt, so that less material was necessary. We used lower carbon concrete to reduce overall embodied carbon across the project. Gabion baskets containing stones or aggregate were used to support soil retention, protect against erosion and to replace concrete structures, and we maximised the use of recycled aggregates.
When it came to the construction itself, we completed as much of the manufacture and assembly as we could offsite at our Centre of Excellence for Modern Construction (CEMC). Not only did this minimise disruption at the site and reduce the size of workforce needed, it also reduced the number of vehicle visits to site, provided the perfect conditions to manufacture with lower carbon concrete and bolstered programme efficiency as the manufacture process was not exposed to weather conditions. Electric plant and machinery were used onsite, supported by solar-powered charging stations. Solar-powered tower lights also helped to improve onsite air quality and reduce the project’s overall carbon footprint.
Where electric plant options were not available, hybrid generators were introduced to boost the efficiency of plant equipment, such as tower cranes, and reduce the overall size of generator needed.
The combined result of the activities underpinning the carbon strategy was a 42% carbon saving versus the baseline, which exceeded the original forecast of 24%. The benefits of the approach were further reaching, however. The use of offsite manufacturing and assembly meant that disruption to residents was minimised, and a smaller workforce could be used onsite. Offsite manufacturing brings safety benefits too; it eradicates the need to work at height and standard shift patterns are adhered to in completing the work. The ability to continue work during inclement weather conditions drives operational efficiency, which can be impacted when working onsite.
From an environmental perspective, the decisions to use electric plant and solar-powered technology had positive implications for air quality and noise levels, as well as reducing the risk of diesel spills around the site.